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Proceedings Volume 0553

Fourier and Computerized Infrared Spectroscopy

David G. Cameron, Jeannette G. Grasselli
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Proceedings Volume 0553

Fourier and Computerized Infrared Spectroscopy

David G. Cameron, Jeannette G. Grasselli
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 20 December 1985
Contents: 1 Sessions, 192 Papers, 0 Presentations
Conference: 1985 International Conference on Fourier and Computerized Infrared Spectroscopy 1985
Volume Number: 0553

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Table of Contents

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Biological And Biomedical Applications Of Fourier Transform Infrared Spectroscopy
Michael Gendreau
The application of infrared spectroscopy to the study of proteins and protein systems has a relatively long history when compared to other biomedical infrared applications. However, the application of infrared to studies of proteins in aqueous solutions has a much more limited history, with work beginning in the mid-1960's. Aqueous work conducted in the 1960's used conventional dispersive infrared spectrometers with limited frequency accuracy and signal-to-noise ratios, which made it very difficult to observe the weaker amide and skeletal vibrations present in the proteins and polypeptides under study. Thus, it was the common consensus of workers at that time (1) that infrared protein spectra were for all intents and purposes very similar to one another, which is in fact the case; and (2) that when working in aqueous solutions, proteins such as those found in blood would be indistinguishable due to this great similarity, which has not proven to be the case.
In situ Spectroelectrochemistry Via Infrared Techniques
R. Kellner, H. Neugebauer, G. Nauer, et al.
Spectroscopic studies of electrode processes at molecular level are necessary both for a more detailed understanding of the fundamental electrochemical reactions involved and for the development of better electrode materials. Such investigations require molecular-specific, non destructive surface analytical techniques capable of analyzing solid-liquid interfaces in situ, without changing the structure of the often unstable reaction products during the measurements. It has been demonstrated previously that IR-spectroscopy fulfills these requirements. Recently, the development of FTIR-spectrometry provides the sensitivity and speed necessary to study also shortliving intermediates generated in a spectroelectrochemical cell during potentiodynamic measurements. This paper deals with the advantages and limi-tations of the different IR-spectroscopic reflection techniques developed and applied since 1980 for the in situ study of metal and organic polymer electrodes in contact with aaueous and non aqueous electrolytes (external reflection techniques, internal reflection technique) . Special emphasis is placed on recent combined electrochemical and FTIR-ATR-spectroscopic investigations on polythiophene, poly-3-methylthiophene and polybithiophene.
Industrial Applications of Fourier Transform Infrared Spectroscopy
A. Ishitani
The latest advancement and potentiality of FT-IR as a tool for industrial materials characterization are reviewed. The position and advantages of FT-IR among other analytical techniques are also discussed, especially in surface and microanalyses. Several examples of FT-IR applications being done in TRC are presented. A study on bilayer membranes with embedded polypeptides, dispersed in water is shown as an example of bulk analysis. Surface analysis of an oxide layer on a silicon wafer by ATR using the wafer itself as an IRE plate is explained. Potentiality of PAS for a deep sampling probe on multilayered composition is illustrated. Finally the present stage of FT-IR microanalysis using an infrared microscope is discussed using examples on real samples.
Quantitative Intensity Measurements By Fourier Transform Infrared Spectroscopy (FT-IR)
John E. Bertie, H. H. Eysel, V. Behnam, et al.
We have made quantitative infrared intensity measurements by FT-IR transmission and attenuated total reflection spectroscopy of liquids and by specular reflection spectroscopy of single crystals. Knowledge of the accuracy of the measurements is necessary, and this paper emphasizes how this was determined for liquid samples. It is concluded that a value of an absorption coefficient that is determined from 4 to 6 transmission spectra of a pure liquid is likely to vary by ±0.6% to 1.5%, depending on the cell used, the beamsplitter used and the optical alignment of the interferometer and detector, provided that the cell is mounted firmly. The average value is likely to agree with the available calibrated value to within 3%, which is within the approximately 5% accuracy of the calibrated value. We believe the main source of error to be the effect of the infrared cell on the light path through the instrument. An attenuated total reflection method has been developed for the easy evaluation of the absorption and dispersion parameters of liquids to an accuracy of about 6% for bands of medium intensity. This accuracy is compatible with typical literature data and is useful to current theory. Specular reflection measurements were calibrated against a silicon standard. They are reproducible to about 3% of the reflectance value, largely due to the surface and position of the sample.
Mathematics Of Spectral Treatment In The Fourier Domain
James A. de Haseth
The basic premise of Fourier domain processing is that the Fourier transform does not alter the information content of a spectrum. Spectra have traditionally been recorded in the frequency, wavelength or wavenumber domain, and this is referred to as the spectral domain. The Fourier transform of a spectrum converts the data to the time, wavenumber or retardation domain, known as the Fourier domain. Data manipilation is often carried out in the Fourier domain, particularly Fourier self-deconvolution, smoothing, and differentiation. These operations involve convolution in the spectral domain, which is equivalent to a multiplication in the Fourier domain. It is mathematically less expensive to achieve these operations in the Fourier domain. Other data handling operations can be achieved in the Fourier domain. The first of these is the Gram-Schmidt orthogonalization of raw GC/FT-IR spectrometry interferograms to construct infrared-based chromatograms. Search systems and structure elucidation methods can also be effectively carried out using Fourier transforms of absorption spectra.
Correlation Transform Spectroscopy
D. E. Honigs, J. H. Perkins
As a spectroscopist, one rapidly learns that obtaining a spectrum of a sample is only part of the work. Many times the real challenge comes in interpreting the spectrum. In correlation transform spectroscopy, commonly referred to as near-infrared analysis, a large emphasis is placed on the data interpretation phase. To make the spectral results intelligible to the analyst, near-infrared analysis correlates a series of spectra with the known analyte concentration. This correlation transforms the spectra so that the relationship between the analyte and the spectra is displayed. This process can be extended to deduce the spectrum of a pure component from those of mixtures, or to deduce the analyte concentration in an unknown sample. Interestingly, near-infrared analysis has shown that surprisingly little spectral resolution is required to quantitate many analytes. Thus, instrumentation designs are being developed which make use of very broad filters made of polymers or other materials. These instruments provide spectral information in much the same way that the eye does.
JOHN OVEREND: 1928 - 1984 A Colleague's Appreciation
Bryce Crawford Jr.
It is not inappropriate that John Overend should be remembered at the 1985 Conference on FTIR. His premature loss in November, 198k at age 56, at the height of his powers, is so recent; although no paper of his appears on the program, the influence of his work shows up in a number of ways, not only in the explicit references; the participants include many of his former students and colleagues; and so many recall him as a spectroscopist and as a man and a friend worth knowing.
Modulation Spectroscopy
Isao Noda, A. E. Dowrey, Curtis Marcott
Polarization modulation can be used to obtain infrared (IR) spectra of any sample which absorbs light of two orthogonal polarizations to different extents. Examples of applications include vibrational circular dichroism (VCD), infrared reflection-absorption spectroscopy (IRRAS), infrared linear dichroism of statically-oriented samples, and time-dependent dynamic infrared linear dichroism (DIRLD) of samples under small-amplitude oscillatory strain. Modulation spectroscopy can be performed on either Fourier transform or dispersive IR spectrometers. A photoelastic modulator (PEM) placed in a linearly-polarized beam of light can alternate the state of polarization at frequencies on the order of 50 kHz. This enables a small difference signal to be obtained in a single measurement without having to subtract or ratio two separately-measured large signals. The principles of polarization modulation are developed and examples of VCD, IRRAS, and DIRLD presented.
Spectral Searching
James F. Sprouse
Infrared Spectral Searching has progressed rapidly over the past two years since the last FT-IR Conference in Durham, England. In addition, if we compare the searching capabilities available to the Infrared Spectroscopist today with those that were available a short four years ago at the last North American Conference held in Columbia, South Carolina, then the advancements are even more impressive. In retrospect, I would describe the state-of-the-art in Spectral Searching at the 1981 FT-IR Conference as "Level 1 Searching", where the spectroscopist was limited to measuring a spectrum for his unknown material, and automatically searching it against very limited libraries at that time to obtain a search report. The report generally provided an ordered ranking of the best matches, chemical name, and a spectrum number so the reference spectrum could be located and reviewed in books. In 1981, there existed a total of three commercially available infrared search packages at the instrument level. Two of the packages were available for FT-IR instruments and the third was available on a dispersive instrument. Only the FT-IR packages allowed viewing the reference spectra on the CRT along with the unknown spectrum by automated spectral retrieval from the reference libraries stored on disk. However, the primary source of reference spectra was still predominantly hard copy.
High Resolution Fourier Spectroscopy of Diatomic Molecules.
J. Verges
Two kinds of studies are mainly considered from conventional emission and laser-induced fluorescence experiments. Several new results are presented : observation of new electronic states, assignment of weak, quasibound and perturbed transitions, studies at the dissociation limit and of collision processes.
High Resolution Infrared Spectroscopy From Space: Preliminary Results Of The Atms Experiment On Spacelab-3
Crofton B. Farmer
A high-resolution FTIR spectrometer had its first flight in May of this year as part of the Spacelab-3 science pay-load. The experiment - Atmospheric Trace Molecule Spectroscopy (ATMOS) - is designed to obtain fundamental information related to the physical and chemical structure of the Earth's upper atmosphere (from 15 to 150 km altitude). There are two major aspects to the investi-gation: the first is the determination of the detailed composition of the stratosphere and mesosphere, and its global, seasonal and long-term variability; the second is the study of the partitioning of solar energy at levels in the atmosphere characterized by dissociation of the constituents and by the breakdown of thermodynamic equilibrium.
Spectroscopy; An Ill-Posed Problem
B. Carli
Spectroscopy can be described as an inversion technique for the retrieval from measured data of an unknown spectral distribution. The implications which follow from this general approach are discussed. It turns out that spectroscopy belongs to the category of ill-posed problems that have more degrees of freedom than data. A revised concept of resolution is suggested, and the role of the model for the data interpretation is underlined.
FT-IR : Today And Tomorrow
J. G. Grasselli, M. Mehicic, J. R. Mooney
The last decade has been a period of astonishing growth and vigor for FT-IR spectroscopy. The first International Conference on Fourier Transform Spectroscopy held in Aspen, Colorado, in 1970, described new instrumentation using Michelson interferometers that had been developed in response to problems in astro-physics, where faster acquisition of data and better ways of handling the large quantity of data generated were needed. The problems had driven the development of new instrumentation. With this impetus, instrument manufacturers introduced reliable, computerized FT-IR instruments for use by industry. These new instru-ments, with their speed and advanced data processing capabilities, led to an explosion of new examples of practical problem solving, as well as new sophistication in analyzing structures of materials or composition mixtures. Today the field of industrial infrared spectroscopy which was literally "transformed" just 15 years ago is vigorous, healthy, and still expanding. Perhaps we have now come full circle, for today industry is again articulating ever more challenging problems that need solving via novel instrumentation and/or accessories. This will lead to a tomorrow in areas that have been elegantly described in the invited lectures and poster contributions of this conference. In this paper, we will describe some typical uses of FT-IR today and from them predict where FT-IR will "walk tomorrow". We will concentrate on industrial applications because that is the community we represent. It is also relevant to point out that the growth and success of new analytical tools or techniques are dependent on the extent of use by industry. Industrial practical problem solving - and just because it's practical or solving a problem does not preclude good science and basic work - drives the development of newer and better ways to get answers to problems or to understand properties of materials.
Fourier Transform Infrared (FTIR) Study of Thermal Stability in Vinylidene Fluoride Copolymers.
S. K. Ahuja, S. Bailey Hiergesell, A. DeLuca, et al.
Fourier Transform Infrared (FTIR) was used to investigate the thermal stability of bisphenol AF crosslinked vinylidene (VF2)/hexafluoropropylene (HFP) copolymers. The uncrosslinked copolymers have the same copolymer ratio of VF2/HFP (3.5/1) with different molecular weights and dynamic shear moduli. The FTIR spectra of the crosslinked copolymer network show that the thermal stability is related to the molecular weights and dynamic shear moduli of the linear, uncrosslinked copolymers, and the concentrations of base and metal oxide filler in the precrosslinked copolymer films. The thermo-oxidation of the crosslinked copolymers by X-ray Photoelectron Spectroscopy (XPS) also shows dependence on the molecular weights and dynamic shear moduli.
Characterization Of Epoxy-Graphite Composites By Diffuse Reflectance FTIR
K. C. Cole, D. Noel, J. J. Hechler
Diffuse reflectance Fourier transform infrared spectroscopy has been used to obtain IR spectra of epoxy-graphite prepregs and cured panels. The spectra are influenced by fibre orientation and front-surface reflection effects which limit the usefulness of the method for quantitative analysis. However, for qualitative work, excellent spectra can be obtained with practically no sample preparation.
FTIR Reflection Absorption Technique Applied For The Characterization Of Electroactive Species
Monika Datta
A spectroelectrochemical technique based on the reflection absorption spectroscopic method is described whereby high resolution in situ vibrational spectra of electrogenerated reaction intermediates(including radicals) and species adsorbed on electrode surfaces can be obtained. Theoretical and experimental aspects of the method,in a single reflection mode, are discussed. The application of this technique to aqueous and non-aqueous systems, using platinum and carbon electrodes are described.
Characterization Of Propellants With Burning Rate Promoters By Pyrolysis GC-FTIR
Pamela J. Duff
Pyrolysis GC-FTIR has been used to study the effects of burning rate promoters on decomposition products of nitramine propellants. The nitramine materials studied are cyclotrimethylenetrinitramine (RDX) and cyclotetramethylenetetranitramine (HMX), and the burning rate promoters consist of an organic and in inorganic salt of the BloH10-2 anion. The samples have been pyrolyzed under controlled conditions of heating rate and duration, and were separated using both packed column (with thermal conductivity detection) and capillary column (with flame ionization detection) chromatography. Both the packed and capillary columns yielded peaks which were not identifiable on the basis of retention times; consequently, FTIR was used to elucidate the structure of these components. In some cases, components not separated chromatographically were individually determined by their FTIR spectra. Also, peaks from various runs having similar retention times were found to have different chemical structures from their spectra. DSC results for RDX and RDX mixtures are also shown.
FTIR/ATR Studies Of Polymer Blend Films
R. Popli, A. M. Dwivedi
Variable angle ATR was used to obtain a depth profile analysis of the films cast from blends of a high molecular weight styrene-acrylate copolymer colloid, an alkali soluble styrene-acrylic resin and an emulsified polypropylene. The dried films show a homogeneous distribution of the styrene-acrylate colloid particles and the solution polymer, however, the particles of polypropylene have a concentration gradient through the film thickness.
Detection And Characterization Of Low-Temperature Phast Transitions By Fourier-Transform Infrared Spectroscopy
Michael Falk
The application of FT-IR spectroscopy to study low-temperature phase transitions in crystalline solids is illustrated by our investigations of (NH4)2NaFeF6 and Cd(C104)2.6H20 between 10 and 300 K. The possibilities of this technique and its limitations are discussed.
Analytical Applications Of FT-IR
D. E. Pivonka, R, C. Fry, W. G. Fateley
Fourier Transform atomic emission spectroscopy is well suited to the determination of nonmetals in the red to near infrared region from 7,900 to 15,800 cm-1 (1) . The speed of Fourier Transform spectroscopy allows full spectrum monitoring of transient atomic emissions on a time scale as short as 0.5 s. The present report demonstrates new applications of this system for "on the fly" collection of nonmetal atomic emission spectra produced as gas chromatographic effluent is introduced into an atmospheric pressure helium microwave induced plasma (MIP). Simultaneous multi-element determination of C, H, N, 0, S, Si, P, F, Cl, Br, and I is now possible with the red to NIR Fourier transform atomic emission spectrometer.
Structure Of Aqueous Liquid Monopropellants By Isotopic Uncoupling FTIR Spectroscopy
Robert A. Fifer
Isotopic uncoupling vibrational spectroscopy is being used to study inter-species hydrogen bonding in aqueous hydroxylammonium nitrate (HAN) as a function of concentration (9.5-17 Molar) and temperature (-170 to 70°C).
Thermo spectral analysis (TSA) of living human skin by FT-IR -Development of a diagnostic method for the early detection of chronic diseases
W. Folberth, G. Heim
A Fourier spectrometer was used in order to measure the spectral emissivity E(k) of human skin in the FIR region k=190-420 cm-1. Three studies on patient groups with defined chronic diseases have been performed: patients with untreated bronchial carcinoma, patients with rheumatic arthritis and patients with chronic renal insufficiency. In comparison with a symptomfree control group all patient groups show significant differences in E(k). As result of a discriminant analysis a separation of 95.7% between carcinoma patients and control persons is possible. The separation quotes between the other groups indicate that patients with malignant neoplasms can be discriminated from other chronically ill persons.
The Graphical Analysis of In-situ FTIR Studies of Coal Reactions
Jon S. Gethner
High resolution graphical analysis techniques of FTIR spectra permit correlations between spectral features to be easily visualized. The techniques are illustrated with an analysis of FTIR difference spectra showing the kinetics of coal drying.
Fourier Transform Infrared Ellipsometry Of Thin Polymer Films
R . T. Graf, J. L. Koenig, H. Ishida
Reflection spectra containing phase as well as intensity information were collected on a FT-IR spectrometer using two linear polarizers. The sample consisted of a poly(vinyl acetate) (PVAc) film on a copper substrate. Using well known principles of ellipsometry, the relative phase retardation (delta) and relative amplitude (psi) were calculated from these measurements.
FTIR-Difference Spectroscopy: A Means of Elucidating Biomolecular Mechanisms
K. J. Rothschild, W. J. de Grip, T. N. Earnest, et al.
FTIR-difference spectra can be obtained from both photoreceptor membrane, involved in visual detection, and purple membrane, involved in light-driven proton pumping. Peaks often can be assigned to single molecular groups, thereby providing information about the molecular mechanisms of these processes. Fourier self-deconvolution can be used to separate overlapping bands.
Fourier-transform infrared (FTIR) Studies On The Hydration Of Polyethylene Terephthalate And Its Copolymer
Guo Hai, Shi Nai, Xu Duanfu
Water absorbed in polyethylene terephthalate (PET) and sulfonated polyethylene terephtha-late copolymer (S-PET) were studied by FTIR spectroscopy. The FTIR spectra of PET and S-PET for different amounts of absorbed water were measured. The subtraction spectra of water containing PET have been determined using nitrogen dried PET as the reference. The characteristic bands arising from water-polymer interactions were obtained. The subtraction spectra show that four oxygen associated infrared bands 1720, 1260, 1122 and 1101 cm-1 were splitted into ten bands. The subtraction spectra of S-PET resemble those of PET. From observed results, a model of hydration in PET and its copolymer is suggested.
Micro-Diffuse Reflectance And Matrix Isolation Fourier Transform Infrared Techniques For The Identification Of Tetrachlorodibenzodioxins
Donald F. Gurka, Stephen Billets, Jimmie W. Brasch, et al.
Diffuse reflectance infrared Fourier transform (DRIFT) and matrix isolation gas chromatography Fourier transform infrared (MI/GC/FT-IR) spectra of the 22 tetrachloro dibenzodioxin (TCDD) isomers have been measured. The spectrum of each TCDD isomer is unique.
The Analysis Of Textile Materials And Textile Additives By Fourier Transform Infrared (FTIR) Photoacoustic Spectroscopy (PAS)
John Hodson
The advantages of FTIR/PAS are outlined for the analysis of textiles, and the application of the technique is illustrated by spectra obtained from an extended range of natural and synthetic materials. The sampling advantages and data handling facilities of FTIR/PAS permit the study of textile additives and forensic type samples.
Surface Contamination by FTIR-PAS
Dennis M. Davis, Lynn D. Hoffland
Fourier Transform Infrared Photoacoustic Spectroscopy (FTIR-PAS) is used to study the contamination of alkyd painted panels by liquids and solids. These alkyd painted panels are stainless steel panels coated with primer and an alkyd resin based paint which the Army uses for its vehicles. Portions of these panels were contaminated by dimethyl methyl phosphonate, tri-(2-ethylhexyl) phosphate, and triphenyl phosphate. The panels were then studied using FTIR-PAS, and the spectra identified.
Detection of Physiological Levels of Hormonal Steroids Labelled with Organometallic Markers by FT-IR Spectroscopy
Ashraf A. Ismail, Ian S. Butler, Gerard Jaouen, et al.
Hormonal steroids such as 17α-estradiol derivatives, labelled with organometallic moieties, have been tested as markers for hormone receptor assay. Among the organometallic labels used were: Cr(C0)3 and Cr(C0)2(CS), which can be attached to the A ring of the steroid, and Co2(C0)6 and Mo2(7-15-05H5)(C0)4, which can be bonded to acetylenic groups in the 1713-position of the five-membered ring of the steroid. The new analytical approach is based on the FT-IR detection of the υ(CO) modes of the organometallic markers. The present estradiol-receptor detection level for 10,000-20,000 scans at 4 cm-1 resolution is about 100 fM, i.e., in the neighbourhood of physiological levels.
Spectroscopic Studies Of The Stratum Corneum
K. Knutson, M. Scott, R. Obremski, et al.
Current spectroscopic investigations of thermally induced changes in the lipophilic pathway of the stratum corneum are beginning to provide insight into the molecular structure and barrier function of the stratum corneum. Enhanced permeability of lipophilic compounds has been noted between 37 and 70°C. Reversible solid to liquid transitions occur in the lipophilic pathway of the stratum corneum in the temperature region associated with enhanced permeability.
Diffuse Reflectance FT-IR Studies At Elevated Temperatures
S. L. Hill, K. Krishnan, H. Matsumoto
The study of gas-solid interactions is of much importance for the understanding of the mechanisms of catalytic reactions. Such systems have traditionally been studied by flowing a gas of interest through a heatable, evacuable chamber containing a thin, free-standing pressed pellet of a solid (1). The preparation of so thin a pellet can be rather time-consuming. FT-IR Diffuse Reflectance (DR) is a popular technique for the study of solids (2-4). Little, if any, sample preparation is required and powdered catalysts may directly be analyzed. The evacuable, heatable chamber allows a sample to be studied at any temperature in a specific environment. When compared to the pellet technique, DR has the advantage of a larger sample surface area and, hence, more sites for interaction. The small optical path within the chamber minimizes potential spectral interference by the gas during the gas-solid experiment.
Infrared Spectra Of Live Cells
H . H. Mantsch, A. Martin, D. J. Moffatt, et al.
The physical state of membranes in the bacterium Acholeplasma laidlawii was investigated by FT-IR spectroscopy. A comparison of the temperature dependence of the infrared spectra of live and lifeless Acholeplasma laidlawii cells reveals that at the temperature of growth, i.e., 37°C, the membranes of live cells have a considerably higher degree of conformational disorder. Furthermore, the thermal response of membranes in live and lifeless cells, as monitored by various infrared spectra parameters, is shown to be quite different.
FT-IR Studies Of Lipid/Protein Interaction In Biological Membranes
Richard Mendelsohn, Mark Jaworsky, Gloria Anderle
FT-IR spectroscopy has been used to monitor phospholipid order and melting characteristics as well as protein secondary structure in reconstituted membrane systems. The protein used in the current work is CaATPase, a Calcium-pumping protein isolated from rabbit skeletal muscle. The protein is isolated, purified and reconstituted into phospholipid vesicles of the desired composition. High precision (0.03 cm-1) measurements of the temperature dependence of the acyl chain CH2 stretching frequencies are used to construct melting curves for the various phospholipids used in the current work. The effect of CaATPase on lipid order depends upon the level of unsaturation of the lipid acyl chains, the strongest perturbations being observed for molecules containing one saturated and one unsaturated chain. Use of acyl chain perdeuterated lipids as one component of a binary lipid mixture permits studies of the thermal response of each component in either binary lipid mixtures or ternary complexes composed of two lipids plus protein. The tendencies of this integral membrane protein to preferentially interact with a particular lipid component is noted in several instances.
Reversible Molecular Orientation in Stressed Bisphenol-A Polycarbonate
R. A. Mosher, W. M. Prest Jr.
The reversible, stress induced changes in the vibrational modes of amorphous bisphenol-A polycarbonate films have been determined by polarized FTIR. The change in the polarization of the integrated intensities of each absorption band are consistent with the preferential alignment of the molecular segmental axis parallel to the applied stress in the low strain elastic deformation region. This implies that the stresses are primarily transmitted through the chain backbone. The stress induced dichroism of the assignable modes corresponds to 0.1%/MPa increase in the degree of orientation. The CH bands are not a function of stress and there is a slight stress induced shift in the frequency of the 1081 cm-1 band towards lower energies. These results indicate that the environment of the inplane modes is perturbed and suggests that the stress transmitted through the polymeric backbone partially relaxes the steric constraints that restrict the orientation of the ortho protons of the phenol rings.
An IR Spectroscopic Characterization Of The Blood Component Platelet Activating Factor
E. C. Mushayakarara, H. H. Mantsch
The platelet activating factor, PAF, has been recently identified as an ether lipid with dramatic bioreactivity. The present IR spectroscopic investigation demonstrates that in an aqueous environment PAF can assume three different structures, a micellar form at tempera-tures above 21°C, a solid-like opaque lamellar form at temperatures below 12°C, and an intermediate transparent lamellar form that exists at temperatures between 12 and 21°C. The three structures are separated by two reversible phase transitions; however, the rate of the reversed micellar to lamellar change is negatively temperature dependent, i.e., about 6 min at -1°C and 12 min at 3°C, and slower than the lamellar to micellar change.
The Phase Transition Behaviour Of Multibilayer Preparations Of Free Lipid A, The Endotoxic Principle Of The Outer Membrane Of Gram-Negative Bacteria: A FT-IR Study
D. Naumann, Ch. Schultz, H. Labischinski, et al.
FT-IR spectra of free lipid A, isolated from Escherichia coli containing C-14 and C-12 acyl chains have been recorded and tentative band assignments were undertaken. The highly complex phase transition behaviour of fully hydrated multibilayer preparations of lipid A has been investigated using temperature-induced frequency shifts, difference spectra and second derivatives of >CH2 asymmetric and symmetric stretching modes near 2918 and 2850 cm -1, respectively. Three "phase transitions" near 22, 34 and 41oC could be detected, the latter being the main transition and - most probably - the familiar B-u-transition. The high value of 41°C found for the main transition temperature may reflect the stability and permeation barrier function of this molecule within the outer membrane of gram-negative bacteria.
Fourier Transform Infrared Spectroscopy (FTIR) Analysis Of Violacein
Nina M. Roscher, Jo Ann Noble
Coupled with thin layer chromatography, FTIR Proved to be an accurate, fast, and inexpensive way to monitor and estimate the relative purity of samples of violacein while also providing a procedure for identifying solvent systems which result in optimum separation of the pigment from non-pigment components with maximum speed and reproducibility.
FTIR Characterization Of Poly(Amido-Amine)S Either In Solution Or Grafted On Materials
M. Nocentini, R. Barbucci, P. Ferruti
The behaviour of some poly(amido-amine)s either in aqueous solution or grafted on the surface of various materials has been studied by the FTIR technique. Difference spectra of the polymers at different pH's show the presence of different protonated forms. By the same technique the capability of the polymers to form complexes with Cu(II) ion has also been evaluated. Transmittance and ATR FTIR techniques are used for monitoring each chemical step in grafting poly(amido-amine)s chain on the surface of polyurethanes.
FT-IR Studies Of The Folding Of Ribonuclease
Jill M. Olinger
FT-IR spectra of ribonuclease A, a small globular enzyme, show the effects of a ribonuclease molecule unfolding and then refolding in deuterium oxide. The deuteration process causes changes in the Amide I and Amide II regions of the spectra that provide information allowing assignment of peaks of the deconvolved Amide I band to secondary structural features.
On The Water Subtraction In The Fourier Transform Infrared (FTIR) Spectra Of Proteins And Lipids
Marie Therrien, Michel Lafleur, Michel Pezolet
A procedure is described to subtract the buffer contribution from the infrared spectra of aqueous solutions of proteins using the 2130 cm-1 association band of water as an internal intensity standard. After correction, the spectra of several globular proteins were used to develop a method to evaluate their conformation in solution.
New Insights On The Oxidic Species In Preoxidized Polyacrylonitrile
Joseph J. Rafalko
Isotopically labelled polyacrylonitriles have been degraded at 235°C in the presence of 16 e 02 and '802 in order to aid the unraveling of the preox infrared spectrum. Replacing 02 with 1802 as a reactant did not affect the position of the 1595 cm-1 band. The only oxygen-18 sensitive modes were found between 1800 and 1650 cm-1. Bands indicative of acids, imides, and pyridone units fused to pyridine rings were detected. The preoxidized powders were subsequently heated in N2 to 750°C. Initially carboxylic acids and imides are lost. Eventually the preox ring vibrations are replaced at higher temperatures by bands at 1600 and 1300 cm-1. The nature of oxygen in the ring structure of preox is discussed.
Medicinals Bonded To Biopolymers: Quantitative And Qualitative FTIR Determinations
L. G. Tensmeyer, H. L . Hunter, R. Nagarajan, et al.
We report the successful quantitative determination of small molecules (haptens) to biomacromolecules. Results are shown for two such systems: 7-[4-chloro-3,5-dinitro-benzamido)-deacetoxycephalosporanic acid (CDNB-7-ADCA), coupled to bovine serum albumin, and polyethyleneglycol coupled to ovalbumin. In each case, the number of haptens actually bonded is considerably less than theoretically possible. We also report the successful analysis of three additional systems, but examples of their data are not shown: CDNB-7-ADCA,CDNB, and 3-[CDNB]-2-azetidinone coupled to ovalbumin. In all cases, the fact that pertinent moieties of the hapten are intact indicates that the entire hapten is intact also.
Detection Of Organic Impurities In Sulfur By Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFT)
Gary A. Totten, Anthony G. Severdia
Diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) was used to qualitatively identify organic impurities in sulfur. The impurities were furthur graded by sorbing carbon disulfide (CS2), and measuring the area under the band from 1600 to 1500 cm-1 relative to the sulfur band at 1300 cm-1, as observed in the DRIFT spectrum. The sorption of CS2 was proportional to the amount of organic impurity, was not removed by vacuum at 70 C, and was reproducible whether sorption was by infusion or by exposure to vapor.
Study On Gallstone And Bezoar (Ox Gallstone) by FT-IR Spectroscopy
Jinguang Wu, Guorong Shen, Hai Guo, et al.
Some specimens of gallstones with black colour and pigment gallstones were studied by FT-IR spectroscopy. From the subtraction spectra of the samples using calcium bilirubin as the reference substance, the characteristic bands of the proteins were obtained. Bezoar is the gallstone of ox. It is an important ingredient of some Chinese traditional medicines. Four specimens of natural bezoar produced from different places were studied by FT-IR. From the subtraction spectra of the bezoar samples using calcium bilirubin as the reference, the main bands of protein were also obtained. The secondary structures of the proteins were discussed.
Picogram Fourier transform-Infrared (FT-IR): Ultramicrosampling And Gas Chromatograph-Infrared (GC-IR)
Tomas Hirschfeld
The commonality between ultramicrosampling and GC-IR is far deeper than the desire for picogram detection levels in both cases. Both techniques also need small area light spots: in ultramicrosampling, for spatial resolution; and in GC-IR, to match limited sample volumes. Fast response is needed for real-time measurements on the fly GC-IR, and for mapping analysis of extended samples in a finite line in ultramicro-sampling. And finally, the fly fast processing is required for real-time recognition of significant success in GC-IR (presence of peaks) and in ultramicrosampling (presence of local anomalies in sample). A small FT-IR interferometer benefiting from the counter-Jacquinot advantage (and some less awkward nomenclature is clearly required here), immersion optics for microsampling and optimized sample cells for GC-IR, high efficiency sources and detectors (and detector electronics!), and the systematic application of information,theory to data processing algorithms can be used to bring both these techniques into the middle picogram domain. Progress from here will require cryogenic sampling GC-IR (giving only small improvements over an optimized light pipe) or non FT-IR techniques, such as grating (shudder!) scanned CO2 lasers (capable of a >100 fold gain).
FT-IR of Reinforced Plastics
Andrew Garton
An internal reflection spectroscopy (IRS) element may be modified by application of thin layers of metal oxides, aramids or carbonised polymers, so that it resembles chemically the surface of reinforcements (eg. glass, carbon, Kevlar) used in the production of reinforced plastics. The first 0.2-1 µm (depending on wavelength) of polymer matrix adjacent to the modified surface may then be examined by FT-IR, using "windows" in the spectra of the coatings. In this way the simulated reinforcement surfaces are shown to modify the chemistry of the thin layer of polymer matrix adjacent to the surface (ie. the interphase). These chemical differences are shown to correlate with property differences in reinforced plastics.
Analytical Applications of Head Space/GC/FT-IR
R. G. Kollar, R. Citerin, M. Markelov, et al.
Headspace analysis is an equilibrium sampling method which involves injeTting the vapor phase of a sample which has been warmed in a sealed vial into a gas chromatograph . This can lead to substantial sensitivity enhancements for volatile components, and can remove the volatiles from non-chromatographable matrices. The combination of headspace gas chromatographic analysis and FT-IR can provide a powerful tool for the identification of volatile organics in a variety of matrices. It also has the potential to enhance GC/FT-IR sensitivity by 1-2 orders of magnitude.
Industrial Applications for TGA/FT-IR
M. L. Mittleman, D. A. C. Compton
A wide range of samples have been studied by TGA/FT-IR, using a mobile, low-cost FT-IR spectrometer coupled to a standard TGA. Much qualitative information can be obtained about the thermal properties of a sample. We have also achieved success at quantitating the evolution of some gases, namely sulfur and carbon dioxides, by observing the decomposition of reference samples.
A Diffuse Reflectance Interface for SFC/FT-IR
Kenneth H. Shafer, Stephen L. Pentoney, Peter R. Griffiths
Supercritical fluid chromatography (SFC) permits nonvolatile or thermally labile compounds to be separated at high resolution without necessarily using a mobile phase which is liquid at atmospheric pressure or room temperature. The most common mobile phase to date has been carbon dioxide, at a pressure above about 1000 p.s.i. and a temperature above 35°C. Both packed columns of the type used for high performance liquid chromatography (HPLC) and wall coated open tubular (WCOT) capillary columns of the type used for high resolution gas chromatography (GC) can be used. In this paper, we report the on-line measurement of infrared spectra of peaks eluting from SFC columns using two approaches: 1) By passing the effluent from the column directly through a flow cell; 2) By eliminating the mobile phase while depositing the solute on KC1 powder prior to measuring its diffuse reflectance (DR) spectrum.
Dynamic approach to FT-IR spectroelectrochemistry
Stuart I. Yaniger, Warren Vidrine
Rapid-scan time-resolved Fourier-transform infrared (FT-IR) spectroscopy is a method that allows one to examine the changes in the infrared spectrum of a system undergoing a chemical or physical change. This method exploits the inherent multiplex advantage of FT-IR; each scan of the FT-IR spectrometer yields the entire infrared spectrum of the sample at the time the scan is taken. Clearly, a time-resoved infrared spectrum can be obtained by storing each scan in a separate computer file. The degree of time resolution is limited by the speed at which the interferometer mirror can be moved and the data system can acquire and store spectral data. At medium spectral resolution (16 cm-1), time resolutions of 12-15 milliseconds are possible using commercially available instrumentation and software, that is, interferograms may be collected and stored at a rate of 65-85 scans per second (1).
Fast FTIR And Infrared Intensity Spectroscopy As A Way To Reveal Structural And Electronic Properties Of Conducting Polymers.
G. Zerbi, C. Castiglioni, M. Gussoni
Polyacetylene (PA) is the prototype of polimeric compounds which ,when doped, become highly conducting. The origin of the electrical conductivity in this and other similar organic polymers is not yet known, in spite of the great efforts made by experimentalists and theoreticians in the fields of chemistry and physics.
Multicomponent Quantitative Analysis In Systems Not Obeying Beer's Law; The Use Of Curve Fitting With Multiple Standards
M. A . Ford, R.. A . Spragg
Quantitative analysis of multicomponent systems is often hindered by deviations from linear Beer's Law behaviour. Attempts to accommodate non-linearity have generally assumed some explicit relationship between absorbance and concentration,l. An alternative approach is to consider the deviations from Beer's Law as arising from a series of additional spectral components. Such a model has obvious physical significance when there are specific interactions between the components in a mixture, and may prove a useful approximation in any situation. On the basis of this model it will be shown that least squares curve fitting can give accurate quantitative results even when there are gross deviations from Beer's Law.
Near Millimetre Wavelength Birefringence And Dichroism In Ferrofluids
C. A. Bentley, J. P. Llewellyn, J. R. Birch
Near millimetre wavelength studies of the complex refractive indices of ferrofluids by dispersive Fourier transform spectroscopy have allowed their magnetic field - induced birefringence and dichroism to be investigated. The results will be discussed in relation to optical studies and to near millimetre wavelength modulation experiments with these fluids.
ADC Errors In Quantitative FT-IR Spectroscopy
Aslan Baghdadi, Warren K. Gladden
Analog-to-digital converters (ADCs) are an indispensible component in the electronic processing chain of modern computer-ized instruments, such as Fourier transform infrared (FT-IR) spectrophotometers. In an FT-IR spectrometer, the interferogram of a broadband source covers a wide dynamic range, on the order of 106:1. This is a very demanding application for a high-speed ADC. Since FT-IR spectroscopy carries the promise of achieving high accuracy, all possible sources of systematic errors must be examined in order to validate that promise'. We will show that linearity errors in the ADC can result in a distortion of the transformed spectrum. This distortion can lead to significant systematic inaccuracies in FT-IR spectrophotometry.
In-situ Modeling Of Gas And Liquid Phase Hydrocarbon Systems
R. L. Barbour, S. M. Butler, M. W. Pestak, et al.
The pressure dependence of infrared spectra has been measured for several gas and liquid phase hydrocarbon systems. Band position and intensity have been correlated with pressure for methane, carbon dioxide, n-pentane, n-hexane, and n-decane as well as mixtures thereof. The feasibility of using infrared on high pressure (up to 5000 psi) mixtures for compositional analysis has been demonstrated.
Rapid-scan Fourier Transform Infrared Studies Of High-Rate Pyrolysis Of Hydroxylammonium Nitrate (HAN) and HAN-d4
James T. Cronin, Thomas B. Brill
The IR spectral assignments for HAN and HAN-d4 were reexamined and found to be more con-sistent with earlier rather than more recent interpretations. High-rate thermolysis of HAN at elevated pressure reveals an oscillating reaction in the initial stage.
Quantitative Analysis in the Fourier Domain - The Optimum Vectors
Chris W. Brown, Steven M. Donahue, Robert J. Obremski
Multicomponent analysis of optical spectra can be optimized by processing the spectral data in the Fourier domain. The transform makes it possible to take maximum advantage of the informational content of the spectra while reducing the data storage requirements and processing time. The transformed spectra are stored and processed as vectors. We have explored methods for selecting the "best" set of vector representations. During this investigation, we found that any number of chemical interferences can be accounted for in the vector representations without knowing the types of concentrations of these components. The methodology greatly expands the capabilities of multicomponent analyses as will be demonstrated on both infrared and uv-visible spectra.
A Comparison Of The Least-Squares And Center Of Gravity Algorithms
David G. Cameron
The least squares and center of gravity peak position algorithms are compared. It is shown that the center of gravity technique is much more precise than the least squares algorithm.
High Resolution Measurement Of The Far-Infrared Stratospheric Spectrum
M . G. Baldecchi, A . Bonetti, B. Carli, et al.
The stratospheric emission spectrum has been measured with a polarising FT spectrometer in the 7-180 cm-1 interval with an unapodized resolution of 0.0033 cm-1 from a balloon-borne platform. The measurements make possible the simultaneous detection of features due to many different molecular species, and provide a comprehensive picture of the stratospheric composition.
Improved Sample Presentation System For NIR Spectroscopy
D. R. Webster, J. L. Casciero, P. J. Cooper
A uniquely designed sample presentation system allows for rapid analysis of powders, liquids, pastes, emulsions, slurries and films with dramatically reduced sampling errors.
Fourier Transform Vibrational Circular Dichroism Of Carbonyl Stretching Modes In N-urethanyl-a-amino acids
Anita C. Chernovitz, Teresa B. Freedman, Laurence A. Nafie
The vibrational circular dichroism (VCD) spectra of the N-t-BOC and N-CBZ-derivatives of alanine, proline, phenylalanine and valine in 0.2M CHC13 solutions all exhibit a characteristic, strong bisignate couplet in the carbonyl stretching region. The VCD couplet is interpreted in terms of the coupled oscillation of the urethane and acid carbonyl groups in an intramolecularly hydrogen-bonded structure.
Phase Analysis Of Infrared Fourier Transform Photoacoustic Spectra
M. Choquet, G. Rousset, L. Bertrand
From an analysis of the signal phase of a Fourier Transform Photoacoustic Spectrometer,a procedure is proposed to obtain a quantitative photoacoustic spectrum.
The Application of Data Enhancement Techniques to the Study of Hydrocarbon Oxidation Processes
John P. Coates, Lynn C. Setti
Oxidative and thermal degradation of hydrocarbon oils are complex processes. While the fundamental chain reaction mechanisms are known, the actual chemistry of a formulation involving several additives still remains a gray area. An understanding of some of the additive interactions and their degradation pathways will ultimately lead to a more scientific approach to formulation optimization for a given application. Current methodology involves laboratory oxidation tests as a screening mechanism before the more expensive mechanical tests are used for the final lubricant evaluation. This is particularly the case for automotive and gas turbine lubricants. The chemistry linking the laboratory test and the mechanical tests for a given oil formulation are rarely considered.
Microsample Analysis Using An Infrared Microscope
T. D. Dee, W. Herres, A . Simon, et al.
A microscope that can measure both in transmittance and reflectance with high sensitivity is described. Furthermore, the changeover is accomplished by moving only two handles and no realignment of the optics is necessary. Advantages of using this "dual-mode" microscope is discussed and several results are reported, highlighting some of its areas of application.
Infrared Intensities in the liquid Phase, OH Vibrations of Primary Aliphatic Alcohols
Hans H. Eysel, John E. Bertie
A method is presented to assess the infrared optical constants from ATR measurements with the "CIRCLE"R assembly. The complex refractive index A = n+ik and the complex dielectric constants E = E'+iE" are obtained by successive approximations with Kramers-Kronig transforms and application of Fresnels equations of reflection. Optical constants and a molar representation of intensities of the lower n-alcohols is given. Integrated intensities of vOH and out of plane 80H are constant for the hydrogen bonded associates of the series of compounds studied in their pure liquids. On the basis of intensity data in CC14 solution a model of self association is discussed for methanol.
Rapid scanning FT-IR/time Resolved Spectrometry (TRS) For Gas Phase Systems
Cindy R. Friedman, James A. de Haseth
The development of rapid scanning FT-IR/TRS for a gas phase system is described. The main focus of the experiment is to obtain time-resolved spectra, by using a cell that can generate sufficient energy to record thermal excitation and relaxation of gas phase molecules. Several problems encountered by other workers have been eliminated by the optimization of a double hollow cathode cell configuration.
Structure-Activity Relations In Enzymes: An Application Of IR-ATR Modulation Spectroscopy
Urs P. Fringeli, Peter Ahlstrom, Claudius Vincenz, et al.
Relations between structure and specific activity in immobilized acetylcholinesterase (ACNE) have been studied by means of pH- and Ca++-modulation technique combined with attenuated total reflection (ATR) infrared (IR) spectroscopy and enzyme activity measurement. Periodic modulation of pH and Ca++-concentration enabled a periodic on-off switching of about 40% of the total enzyme activity. It was found that about 0.5 to 1% of the amino acids were involved in this process. These 15 to 30 amino acids assumed antiparallel pleated sheet structure in the inhibited state and random and/or helical structure in the activated state.
Hazardous Waste Analysis By Direct-Linked Fused Silica Capillary Column Gas Chromatography/Fourier Transform Infrared/Mass Spectrometry
Donald F. Gurka, Richard Titus
A capillary gas chromatography/Fourier transform infrared (GC/FT-IR) spectrometer has been linked to a Mass Selective Detector (MSD). A 10:1 effluent splitter was used to divert 90% of the GC effluent to the FT-IR cell and 10% tO the MSD. This system has been used to characterize the GC-volatile portion of dye and herbicide manufacturing wastes, sediments, sludge extracts, and the extract of a freshwater turtle. Use of a 2300 member FT-IR spectral data base, in conjunction with the NBS mass spectral (MS) data base, greatly increases the number of on-line MS confirmations obtainable by this direct-linked system over that of the conventional EPA GC retention time method. Chromatographic separation on a single capillary GC column allows a direct one-to-one correlation of peaks in the FT-IR and MSD chromatograms. Although this MS detector is 10 to 100 times more sensitive than the FT-IR detector used, and although the MS search library is over 15 times larger than the FT-IR search library, for the samples analyzed it was determined that each detector provided approximately the same amount of useful structural data.
Theoretical Comparison of Classical (K-Matrix) and Inverse (P-Matrix) Least-Squares Methods for Quantitative Infrared Spectroscopy
David M. Haaland
Both classical and inverse least-squares methods have been applied to the quantitative IR spectral analysis of multicomponent samples. The two methods are presented and compared in this paper. The classical method is capable of higher precision and accuracy since it can use all of the data in a spectrum. Its ability to obtain full-spectrum residuals provides methods for identifying problems in the spectral data. The inverse method has the potential advantage that it can be applied even if only one component in the sample is known.
Diffuse Reflectance Infrared Fourier transform (DRIFT) Spectral Studies
Robert I. Haines, Derrek G. Owen
Diffuse reflectance infrared Fourier transform spectroscopy has been used to identify hydrothermal alteration products of feldspars. In acidic media, kaolinite clay is the major product. The presence of divalent metal ions in saline solutions induces formation of montmorillonite clay. Cesium is incorporated into an alumi•osilicate lattice as pollucite. DRIFTS is shown to be effective in rapidly identifying these reaction products.
Structural Analysis Of Ethylene/Acrylic And Methacrylic Acid Copolymers Using Fourier Self-Deconvolution Of Infrared Spectra
Matthew A. Harthcock
Fourier self-deconvolution (FSD) has been applied to several regions of the infrared spectra of ethylene/acrylic and methacrylic acid copolymers to obtain detailed information on the structure of these copolymers. The computer assisted technique has been applied to the 1050-830 cm-1 region of the infrared spectrum of the copolymers to resolve the vinyl (909 cm-1) and vinylidene (887 cm-1) CH2 wagging vibrations from the in-phase out-of-plane hydrogen deformation vibration of the acid dimer (943 cm-1). The technique was applied to the carbonyl stretching vibration region (1820-1660 cm-1) to study the structure of the acid groups. Two distinct hydrogen bonded (1710 and 1696 cm-1) and free (1758 and 1745 cm-1) acid group structures were observed for the 9% acrylic acid copolymers, while the methacrylic acid copolymer showed predominantly one hydrogen bonded (1696 cm-1) and one free (1758 cm-1) acid group structure. Also, the 6.5% acrylic acid copolymers showed essentially one type of hydrogen bonded (1706 cm-1) carbonyl and two free carbonyl stretching absorptions (1758 and 1745 cm-1).
Improvements In Difference FT-IR Spectroscopy Of Diluted Solutions By A Special Defringing Technique.
H. M. Heise
A procedure in the interferogram domain is presented for the elimination of interference fringes in the infrared difference spectra of diluted solutions. For cases the refractive index of the cell window material is not matched to that of the solvent, residual interference fringes will be obtained if there is a change in the refractive index of the solution due to the solute contribution. Here the change in the refractive index is related to a linear shift of that interferogram part causing the channel spectra. By this defringing technique the shift is compensated for in the solvent interferogram. The results are compared with those from zeroing and from substitution of the considered interferogram features.
Some Applications Of FT-IR Photoacoustic Spectroscopy
K. Krishnan, L. Gelfand, S. L. Hill
The sensitivity and speed of FT-IR make it possible to obtain the photoacoustic spectra of a variety of samples with little or no sample preparation (1,2). A typical photoacoustic (PA) detector consists of an acoustically sealed cell of small volume in which the sample under study is kept surrounded by an inert gas. The cell also contains a sensitive micro-phone. When the interferogram is focussed on the sample, the sample absorption modifies the interferogram and sets up a pressure wave in the cell. This is detected by the micro-phone and Fourier transformed to yield the PA spectrum. A theory of the photoacoustic effect assuming an one-dimensional model for the PA cell has been given by Rosencwaig and Gersho (3), in terms of the optical and thermal properties of the sample, the backing material, and the gas. The general solution for the one-dimensional model is too complex and cannot be used for as such. However, Rosencwaig (3) has simplified the solution for a number of special cases. He has shown that under certain conditions the PA signal is proportional to the thermal diffusion length. This length varies inversely as the square root of the modulation frequency. Thus, it is possible in principle to record the PA spectra from different depths of a sample by simply varying the modulation frequences. In an FT-IR instrument the modulation frequencies can be varied by changing the velocity of the moving mirror. Thus, FT-IR-PA depth profiling studies can be carried out easily.
Accessories For Micro-Emission FTIR And Their Performance
James L. Lauer, Peter Vogel
Micro-emission FTIR (MEFTIR) is a most sensitive technique for the analysis of non-uniform surface layers. It is non-destructive, requires no sample preparation, can be used in an ambient environment, with flat or even rough surfaces, at high and low temperatures, and it requires only microscopic sample areas. In contrast to reflection methods, MEFTIR does not need precise angles of observation and its dynamic range requirement is small, since differencing is not involved. However, its sensitivity depends on wave-length by Planck's law.
New Apodization Function In FT-IR Spectrometer
J. Y. Dong, Z. Z. Li
The important problem in the technique of Fourier transform spectroscopy is obtaining the narrowest possible instrumental function for the Fourier Transform Infrared ( FT-IR ) spectrometer with the smallest possible secondary maxima. In this paper we are to present a new class of apodization functions, which has the characters that reduce resolution less but the largest secondary maximum more, and to study the effects of apodization on resolution in FT-IR spectrometer by this kind of apodization functions.
Fourier Analysis Of Near Infrared Spectra
W. F. McClure, A. M . C Davies
Transforming NIR spectra from the wavelength domain (WD) to the Fourier domain (FD) has a number of advantages. These include: (1) reduces multicollinearity, (2) calibration time reduced by 98%, (3) magnetic storage requirements cut by 98%, (4) improves methodology for spectral searching, matching, and process control, (6) permits fast computation of derivatives and (7) facilitates rapid analysis of instrument noise and anomalies.
Toward Quantitative Diffuse Reflectance: Diffuse Reflectance Without Specular Impurity.
Robert G. Messerschmidt
Diffuse reflectance has become one of the simplest technics available to the researcher for the FT-IR analysis of powdered samples with a minimum of sample preparation. However, it is still not used widely as a quantitative tool. Papers have appeared in the literature suggesting that diffuse reflectance can indeed be used quantitatively l, but more casial attempts in real world laboratories tend to fail.
Resolution Enhancement of Photoacoustic FTIR Spectra
K. H. Michaelian, W. I. Friesen
Fourier self-deconvolution of a photoacoustic FTIR spectrum by direct manipulation of the observed interferogram is shown to be possible. Over a narrow frequency range, the measured photoacoustic (PA) signal is approximately proportional to the optical absorption coefficient, thereby enabling known line shapes to be used in the deconvolution. The method is applied to the PA spectrum of kaolinite and the enhanced spectrum is compared with other theoretical and experimental results.
Studies Of Kinetics Of Non-Isothermal Reactions In Real Time Using Fourier Transform Infrared (FTIR) Spectroscopy
M. P. Miller, R. E. Miller, E. C. Penski
An all-Teflon cell fitted with an ATR prism has been constructed and used to study rates of rapid non-isothermal reactions of trivalent phosphorus compounds with sulfur. Both liquid/liquid and liquid/solid reactions have been studied. In some cases rate constants and activation energy can be calculated from data obtained during a single reaction.
A UNIX Based Computer Workstation For Spectroscopic Data Manipulation
D. J. Moffatt, P. W. Yang
A UNIX-based computer workstation for spectroscopic data reduction is described. A Heurikon Corp. HK-68 microcomputer (with Motorola 68000 CPU and UNIX operting system) accepts data downloaded from five spectrometer systems. Various hardware and software devices are used to optimize the downloading of data to the multi-user UNIX system. Software tools, written in Fortran 77, include: 1) screen interactive routines for Fourier smoothing, Fourier derivatives, Fourier self-deconvolution; 2) mathematical manipulation and plotting of spectra and of measurable spectroscopic parameters (e.g., peak position, halfwidth, intensity); 3) methods of displaying series of spectra. UNIX system features like shell script, shell variables, I/O redirection, and background processing are fully utilized to enhance the power and flexibility for the programs used in data reduction.
Two Dimensional Fourier Transform Infrared (FTIR) Mapping
R . L. Mowery, R. R . Smardzewski
A simple device for the two dimensional IR mapping of curved surfaces was developed and interfaced to a diffuse reflectance attachment for an FTIR spectrometer. The device consists of a mounting frame coupled to a micrometer driven translation stage. The sample is longitudinally driven through the focal point of the diffuse reflection attachment. By combining translations with rotations, a two dimensional matrix of spectra from the surface is acquired. The spatial resolution of these spectra approaches 1 mm. A two dimensional mapping of an electrical contact surface reveals an inhomogeneous distribution of a hydrocarbon species (the lubricant) and the presence of a contaminant containing a cyano group.
The Ultra Rapid Differentiation And Identification Of Pathogenic Bacteria Using FT-IR Techniques
Dieter Naumann
A novel, FT-IR spectroscopic approach to the differentiation and identification of pathogenic microorganisms could be elaborated. The method takes advantage of the Fourier transform mid-infrared spectra of intact microorganisms. Such spectra could be recorded within minutes with high sensitivity and reproducibility when applying a highly standardized experimental procedure prior to ir measurements. By comparing the complete ir spectra - or selected spectral ranges of them - on the basis of their first and second derivatives, differentiation and identification of the microorganisms could be accomplished using cross-correlation algorithms.
Time Resolved Studies Of Adsorbed Species
J. Howard, J. M. Nicol
A time-resolved Fourier transform IR study of ethyne adsorbed on ZnNaA zeolite yields results very different from those reported for related systems. Initially two species (A and B) are formed by the interaction of C2H2 with the cations. Whereas species A (π-bonded C2H2) was found to be removed immediately on evacuation, species B (probably Zn-acetylide) was not fully removed after 60 mins evacuation. In the presence of the gas phase, bands due to Species A decreased slowly in intensity as new bands due to adsorbed ethanal were observed.
IDIOTS - An Interpretation System For Infrared Spectra Based On A Structure-Oriented Library
Michael J. Passlack, W. Bremser
IDIOTS is a structure-oriented documentation and interpretation system' for infrared spectra.
Fourier Transform Vibrational Circular Dichroism In The amide I band Of Polypeptides
M. Germana Paterlini, Teresa B. Freedman, Laurence A. Nafie
The Fourier transform vibrational circular dichroism (VCD) in the amide I region of poly-L-lysine in D20 solution has been investigated. Signals corresponding to the random coil, a-helix and antiparallel (3-sheet have been characterized. The spectrum of the a-helix shows the presence of three distinct features in agreement with previous results on deuterated polypeptides. We were able to detect the antiparallel β-sheet conformation in solution; the signal is unexpectedly large and monosignate in contrast to that predicted from exciton theory.
Considerations for the Optimization of Infrared External Reflection Spectroscopy (IR-ERS) at Liquid/Solid and Gas/Liquid Interfaces
Marc D. Porter, David L. Allara
Classical electromagnetic theory has been used to quantitatively assess the effects of various experimental parameters on the sensitivity of IR-ERS for organic monolayers at liquid/solid (L/S) and gas/liquid (G/L) interfaces. Conditions varied at the G/L were angle of incidence and polarization. Additional conditions examined at the L/S, located in a thin-layer cell (TLC), were solution layer thickness and cell window material. The effects of these variations on sensitivity were determined for a model system consisting of a 30 A layer of C19H39 alkyl chains (C19) at H20/Au and air/H20.
Structural Analysis Using Interferometric Data
Paul T. Richardson, James A. de Haseth
A technique utilizing Fourier domain data for the determination of structure features of compounds has been examined. By categorizing a large data set, similarities in Fourier domain data have been related to structural features. Predictions of molecular structure for a compound can be made by determining which categories its data most closely resemble. Due to the speed and simplicity of this technique, it appears to be feasible to perform structure elucidation in real time for use as a prefilter before a library search, or as confirmation after a library search.
Quantitative Photoacoustic Spectroscopy Of Thick Sample By A New Data Analysis.
G. Rousset, L. Bertrand, B. Mongeau
A new data analysis is proposed for the calculation of quantitative infrared (I.R.) spectra by the photoacoustic (P.A.) method. The theoretical P.A. signal components inquadrature and in-phase with the modulated I.R. excitation exhibit intrinsic variations in function of the variable Op. The identification of such a behavior in the experimental data permits to avoid the signal amplitude saturation and the determination of an external signal phase reference, two common problems in P.A. spectroscopy. The proposed data manipulation leads to the calculation of a quantitative sample spectrum. This is illustrated by an experimental example.
FTIR - Studies Of Infrared-Laser Induced Photorotamerization Reactions In Low -Temperature Matrices
Otto Schrems
IR-laser induced photorotamerizations of 2-fluoroethanol (FE) and of hydrogen-bonded alcohol dimers have been studied in low-temperature inert gas matrices by means of FTIR-spectroscopy. The interconversion processes of FE are complex in many matrices, e.g. solid argon, and show effects due to interconversion, photoorientation as well as effects caused by different trapping sites. In solid xenon, however, only the Gg' Tt isomerization takes place after excitation into the OH stretching band at 3610.5 cm-1 (Gg' isomer) as indicated by the depletion of the 3610.5 cm-1 band and simultaneous growing of the 3650.0 cm-1 absorption band (Tt isomer). This reaction is reversible with the back reaction Tt Gg t (excitation at 3650.0 cm -1 ) being about 5 times slower. IR-induced interconversions of hydrogen-bonded alcohol dimers isolated in cryogenic matrices have also been studied. For many alcohols voli dimer absorption (D2 ) bands have been observed with multiplet structure indicating several mutual positions of the two alcohol molecules relative to the 0 axis. The changes in band intensities observed after excitation into these D2 bands (3550 - 3400 cm range) establishes that interconversions of the dimers take place and that each D2 band corresponds to a particular dimer species with open chain structure.
The Art of FTIR Microsampling
J. C. Shearer, D. C. Peters
This paper describes in detail an FTIR Microscope and its application to an art conservation problem. Spectral results provide qualitative identification of sub-nanogram flecks of paint and aid the conservator in assigning approximate timing of earlier repair or over-painting. The microscope accessory, equipped with a built-in high D* MCT detector, can analyze areas of a thin layer to demonstrate inhomogeneity which can provide a clue to artist techniques.
Protein Structure By FTIR Self-Deconvolution
D. Michael Byler, Heino Susi
Fourier self-deconvolution was applied to the peptide-carbonyl stretching vibration (amide I mode) of more than 20 globular proteins in deuterium oxide solution. This band, which usually exhibits little discernible fine structure, was thereby resolved into three to nine components. The individual components were assigned to protein segments consisting of extended chains, helices, and various turns and bends. The areas of the components were evaluated by Gauss-Newton iterative curve fitting with the assumption of Gaussian band shapes. Quantitative estimations regarding secondary structure were made by calculating the sum of the areas of the components asssociated with a particular conformation as a fraction of the total amide I band area. The results for helix content and for extended chain content are in good agreement with literature values obtained from X-ray data.
Resolution Of Overlapped Bands By A Fourier Method
P B Tooke, D I James
A procedure is described which is aimed at the isolation of individual components, with their original parameters of width, shape and amplitude, from a composite envelope of overlapped bands. The method is based on a development of the Fourier self-deconvolution (FSD) process, and the principles and applications are illustrated with synthetic and real data.
Quantitative Analysis Of Cristobalite In The Presence Of Quartz
Gary A. Totten
The detection and quantitation of-cristobalite in quartz is necessary to calculate threshold value limits (TVL) for free crystalline silica (FCS) as proposed by the American Conference of Governmental Industrial Hygienists (ACGIH). The cristobalite standard used in this study was made by heating diatomaceous earth to the transition temperature for cristobalite. The potassium bromide (KBR) pellet method was used for the analysis. Potassium cyanide (KCN) was used as an internal standard. Samples ranged from 5% to 30% cris-tobalite in quartz. Precision for this method is within 2%.
On The Use Of Natural Bands In Bandsplitprocedures
T. Visser, E . T .G . Lutz, J. H. Van der Maas
Composite OH-stretching bands have been resolved into the contributing components using carefully chosen natural bands as a standard. Visual resemblance and the area of the difference band, A--vbs-Acomposed, proved to be good criteria for the correctness of the splitting. It is demonstrated that both individual bands as well as composite ones form suitable standards, which thus allows the unravelling of bands with a rather complex character. The method is accurate and reliable provided the standards are chosen in accordance with the components one expects to be present. It is a useful tool in conformational analysis and structure elucidation.
Methods Development For Rapid-Scanning Gas Phase Fourier Transform Infrared/Time-Resolved (FT-IR/TRS) Spectrometry
S. Penn Weaver, James A. de Haseth
The development of techniques for use in gas phase Fourier transform infrared time-resolved spectrometry (FT-IR/TRS) is described. Equipment designs and experimental parameters are shown, and problems requiring modification of parameters or equipment are discussed.
The Vibrational Spectra Of Selected Bicyclic Compounds
C. Castro, E. A. Dixon, N. Ibrahim, et al.
A valence force field and the vibrational wavenumbers are determined for bicyclo[2.2.1]- heptane (I), bicyclo[2.2.1]hepta-2,5-diene (II), and 7-oxabicyclo[2.2.1]heptane (III) by ab initio calculations at the STO-3G level. The calculated wavenumbers are compared to ob-served infrared absorptions and Raman emissions. New and in some cases revised assignments are derived.
High Pressure Infrared Studies Of Aqueous Lipid Assemblies
P. T. T . Wong, H. H . Mantsch
Infrared spectra of dipalmitoyl phosphatidylcholine (DPPC) bilayers in water have been measured over the pressure range 0 to 35 kbar. Discontinuities in the pressure dependencies of various infrared spectral parameters indicate that structural phase transitions occur at 1.7, 4.8 and 15 kbar. Pressure-induced changes in the CH2 bond angle and in the chain orientation are evident. Pressure also affects the dispersion of,various vibrational frequencies resulting in drastic changes of the Fermi resonance interaction between the symmetric CH2 stretching mode and the continuum of the binary combination of the CH2 bending mode.
Analytical Uses of PAS
Charles Q. Yang, William G. Fateley, John A. Graham
The aluminum-polyethylene adhesion, the polyurethane-sized cotton yarns, and the photodegradation of the polyvinylchloride-titanium dioxide composite were studied by FT-IR/PAS. It can be concluded that the FT-IR/PAS is well suited for the material science studies and especially for surface investigations.
Pressure And Temperature Induced Phase Transitions In Aqueous Surfactants
P. W. Yang, P. T. T . Wong, H. H. Mantsch
Various infrared spectroscopic parameters were used to study the pressure and temperature induced phase transitions in aqueous sodium alkenoates. It is demonstrated that thermodynamic parameters such as the critical micellization temperature or the critical coagelization pressure, as well as the structural changes that occur at these phase transitions, can be readily obtained with the state-of-the-art FT-IR technique.
Learning Algorithms In The Infrared
Tomas Hirschfeld
The use of learning algorithms to automatically set up analytical procedures in the near IR leads to considerable statistical complexities when one attempts to refine and optimize the method. While current work employs an almost brute force approach using lots of signal/noise ratios, plenty of samples and well defined representative learning sample sets, backed up by plenty of trial and error research, vastly more efficient, more easily automated, and more reliable procedures are, in principle, possible. It soon becomes apparent, however, that the power of our algorithms and the calculating capabilities of our computers are nowhere matched by our understanding of the underlying logic of the procedure. The learning algorithms of correlation spectroscopy, and the optimization process of multilinear regressions underlying them, are logically very complex entities whose complete understanding hinge upon a number of (seemingly) philosophical fine points. While no such complete understanding seems near at present (despite the overwhelming success of our so far crude approach to this spectroscopic technique), a number of insights derived from detailed considerations of the process will be discussed. These include procedures for avoiding optimization pitfalls, overall perform-ance improvements exploiting the non-Gaussian error distribution of the results, simplified optimization routines, and procedures for internal data verification.
An Integrated Approach To GC/FTIR
M. A. Ford, R. A . Hurrell
When FTIR is used in conjunction with Gas Chromatography certain definable system constraints can be shown to apply both to the design and operation of the GC/FTIR system, and the operation of the GC system. The design objective of an integrated system combining a state-of-the-art gas chromatograph with a flexible cost effective GC/FTIR system on the one hand, and the requirements of the analyst of the other is to obtain a realistic compromise between the demands of equipment and analyst.
Triple Modulation FT-IR Spectrometry for Surface Analysis in the Far Infrared Region
Norman A. Wright, Peter R. Griffiths
Although several spectroscopic techniques yield analytical information about species adsorbed on flat surfaces, most of the more sensitive measurements require the sample to be placed in a high vacuum and/or only yield the elemental composition of the surface. Infrared spectrometry is not limited by either of the above constraints but does have the disadvantage of relatively poor sensitivity. Most previous measurements of the infrared spectra of adsorbed species on flat substrates have been above 700 cm-1 so that only the intramolecular vibrations of the adsorbate can be observed. Of equal importance, but very infrequently studied, are the intermolecular vibrational modes of the sorbed species and the metal substrate. Measurement of the frequency of these bands should yield direct information on the strength of the interaction between the adsorbate and the adsorbent.
Intensity Spectroscopy and FTIR as New Tool for the Study of Polymer Blends.
G. Zerbi, E. Galbiati, C. Castiglioni
The determination of the microstructure of polymer blends and of the kind and strength of intermolecular interactions among the blended species is an important goal in the field of material science. Infrared spectra of polymer alloys may provide two important information from peak frequencies and band intensities. In this kind of study FTIR spectra are essential because of the great accuracy in the data collected and because of possibility of data manipulation (e.g. difference of spectra, band deconvolution, ratios of intensities etc.).
Photoacoustic Infrared Fourier Transform Spectroscopy of Thermally and Chemically Modified Coals
Brian M. Lynch
Over the past four years, Photoacoustic Infrared Fourier Transform (PAIFT) spectra of coal samples have been acquired in our laboratory for a data base now amounting to some 6000 spectra. Various preliminary reports of our results have been presented (1-5).
Applications of a New High Pressure Anvil Cell for IR Spectroscopy
Edward G. Bartick
A simple, easy to use, low cost, high pressure anvil cell has been developed to make optically dense samples thinner. This cell was developed as a sample preparation technique for microscopy/infrared spectroscopy(Mic/IR). The application of the cell has been to acquire improved spectra of samples such as fibers and paint chips.
Applications of a hi Fressure Reaction, Cell Using Cylindrical Internal Reflectance with FT-I1
William R. Nose, Edward G. Bartick
The study of two holoceneous reactions and an evaluation of the potential to stucy. hetcroEeneous reactions are described- Reactors constructed with cylindrical internal reflection (CIE) elements were used. The Lonsanto acetic acid process and a. rhodiun catalyzed hexene hydroformyiation reation were examined to follow the product formation anu intermediates. Solids typically. used in heterccencous reactions were successfully' examined with the powders packed acainst a CIR crystal.
Far infrared spectroscopy with a 4-meter path difference interferometer
A. Bonetti, B. Carli, M. Carlotti, et al.
An FT spectrometer with a one-meter mirror stroke and a maximum path difference of 4 meters has been constructed for measurements in the 10 - 180 cm-1 region. The instrument can be used with either a polarizing beam-splitter or a mylar beam-splitter. A line-width of 1.8 10-3 cm-1 FWHM has been measured in preliminary spectra.
Prospects For Process Control Using Fourier Transformed Near Infrared Data
A. M . C . Davies, S. M. Ring, J. Franklin, et al.
Methods are proposed for utilising Fourier transformed near infrared data (FTNIR) in on-line systems for product identification and process control. Tests on spectra from a laboratory-based instrument gave encouraging results.
Infrared Emission Spectroscopy: A New Accessory
M. Handke, N. J. Harrick, J. L. Lauer, et al.
The principal problem in measurement of emission IR spectra is the low signal to noise ratio resulting from the large background radiation. One method of increasing the signal is to collect the emitted radiation over a very large solid angle using an ellipsoidal mirror. In this method, placing the sample at the short focal length of the ellipsoid both increases the amount of radiation collected for an improved signal to noise ratio as well as facilitates sampling of small areas. For locating the area of interest, a microscope is mounted on the emission accessory.
Optical Spectroscopy: Now Six Complementary Methods
N. J . Harrick, M. Handke, S. N. Ignelzi
The recent addition of Photo-Acoustic Spectroscopy (PAS) and Emission Spectroscopy (ES) brings to six the number of methods used throughout the IR-VIS-UV range. The other four techniques are: Transmission Spectroscopy (TS),External Reflection Spectroscopy (ERS), Internal Reflection Spectroscopy (IRS), and Diffuse Reflection Spectroscopy (DRS). Each of these methods can now be used in all the spectrometers without modification to the instrument. The principles of each technique will be discussed as well as advantages and disadvantages with respect to sensitivity,sample preparation,spectra interpretation and applications.
Some Applications Of Microtransmittance And Microreflectance Techniques
K. Krishnan, S. L. Hill, L.. S. Gelfand
A transmission microsampling accessory to use with FT-IR instruments was introduced at the Pittsburgh Conference, 1983. This accessory, which employs all-reflecting on-axis optics, has subsequently been modified, and this Universal Microsampling Unit can be used to record the transmission or the reflection spectra of samples as small as 20μm x 20μm in linear dimensions. The applications of this accessory to the study of the spectra of semiconductors (1) and polymers (2,3) have been published in the literature. The highly sensitive accessory can be used to record the spectra of single polymer filaments as small as 15/μm in diameter. Using a polarizer inserted in the optical path, dichroic spectra of single fibers, such as PET, have been recorded (3). The microsampling method has also been used for the study of contaminant particulates suspended in solution, characterization of different layers in a multi-layer polymer, and "fish eyes" on painted polymer panels (4). In this paper, we will briefly describe the universal microsampling accessory and some of it applications.
Dependence Of Calibration Curves Obtained From Gram-Schmidt Chromatograms From Experimental Parameters In CGC/FTIRS
Hans Malissa Jr., Kurt Martin, Karl Winsauer
The calibration curve for quantitative evaluation of Gram-Schmidt chromatograms (GSC) show a non-linearity in the low concentration region. Systematic experiments revealed, that variation in the baseline height in the GSC is responsible for a shift in the calibration curve. Summarized results are: (1) small changes of baseline introduce relative large errors; (2) this non-linearity must also be considered, when small peaks are measured which are not completely separated from a major one.
Recent Developments In HPLC/FT-IR
Robert G. Messerschmidt
The problems associated with the FT-IR detection of reversed phase liquid chromatographic separations are well documented 1. Strong spectral interference from the (usually) aqueous mobile phase is the worst culprit. Eluent concentrations are generally too low to be sampled directly by transmission or ATR, at the short pathlengths necessary to allow a window past water absorptions. However, a method of sample precon-centration is described which allows a 10-fold enrichment of concentration while placing the analyte in an IR transparent solvent 2. The technic is based on a solid phase extraction procedure whereby analytes are immobilized in preconcentrator cartridges. While immobilized, the sample may be washed free of buffer and dried. The analyte is then eluted in a small volume of less polar, IR-transparent solvent. This paper describes the device, then details two separations studied using the device.
Near-, Mid-, and Far-Infrared Photoacoustic Spectroscopy
J. C. Donini, K. H. Michaelian
Near-, mid-, and far-infrared photoacoustic spectra are obtainable using a commercial FTIR spectrometer and cell. Several sources of noise in these spectra are discussed and some strategies which reduce this noise are mentioned. The near- and far-infrared regions are made accessible by the use of appropriate optics and, in addition for the near-infrared, by reduction in the speed of the interferometer moving mirror.
Near IR Fourier Transform Spectrometer with an IR Vidicon
S. Minami, T. Okamoto, S. Kawata
To accommodate recent demand for spectroscopic sensors durable in field measurement, a compact and rugged near-IR FT spectrometer utilizing a polarization interferometer has been constructed and evaluated. The instrument is characterized by in-line optics and an image sensor which eliminates mechanical moving parts. The wavelength coverage from 0.7 to 2.211m is mainly restricted by an IR vidicon temporarily utilized as the image sensor. The results obtained suggest that a similar design utilizing a solid state IR image sensing element would be an excellent spectroscopic sensor in the near-IR region.
High Speed Countercurrent Chromatography/Fourier Transform Infrared (HSCCC/FT-IR) Spectrometry
Rodolfo J. Romanach, James A. de Haseth
High Speed Countercurrent Chromatography/Fourier transform infrared (HSCCC/FT-IR) spectrometry is present-ed. High solute-to-solvent ratios can be obtained in separations performed using HSCCC. At these high solute concentrations it is possible to obtain spectra of solutes without solvent elimination, even in the presence of polar solvents, such as water and methanol.
Liquid Chromatography Fourier Transform Infrared (LC/FT-IR): Solutions Work
Patricia B. Roush, Gregory L. McClure, Robert W. Hannah
Our initial approach to the LC/FT-IR problem uses an infrared flow cell and a reverse phase LC column with solvent gradient. Using a factor analysis program a pseudo-solvent back-ground can be calculated and fitted to each spectrum obtained in the LC/FT-IR run. By examining the residual spectrum obtained by subtracting the pseudo-reference spectrum from the sample spectrum, the spectra of the trace compounds can be found.
An Infrared Database System from the IRDC Cards and Its Applications
M. Tasumi, I. Suzuki, M. Morii, et al.
An effort has been made to convert the infrared spectral data previously published from Infrared Data Committee (IRDC) of Japan to a form accessible from a wide range of computer systems. For each absorption band, a pair of data representing its line position (in wavenumber) and intensity (in percent transmission) is extracted. These data have been assembled and stored in magnetic tapes so that they can be installed in various types of computers. The spectral search systems have also been constructed from this IRDC database. In this paper some basic structures of the converted IRDC database as well as the constructed search systems for large- to small-scale computer systems are described in some detail. The effect of intensity data upon the spectral search processes is also discussed.
Orchids and Bee's Knees: Investigating the Euglossine Syndrome with Gas Chromatography/Fourier Transform Infrared GC/FT-IR
Gregory L. McClure, N. H . Williams, W. M. Whitten
The GC/FT-IR analysis of a fragrance obtained from a Gongora tricolor orchid is described. The significance of this type of analysis is explained in terms of the elucidation of the complex relationship between orchids and bees known as "The Euglossine Syndrome". The fragrance sample was found to contain p-cresol, p-methylanisole and a variety of terpenoids, including myrcene, cineole, limonene, cymene, ipsdienol, and an olefinic product which appears to be the dehydration product of ipsdienol.
A Standard For Exchange Of Infrared Spectra In Computer Readable Form
Robert S. McDonald, Paul A. Wilks Jr.
Modern public communication systems provide means by which infrared spectra and auxiliary physical and chemical information can be transmitted to remote locations quickly and without error. JCAMP-DX is a proposed standard form for such communications which has been evolving since FACSS-83. Infrared instrument manufacturers are expected to provide software for conversion to and from JCAMP-DX and their own internal representation of spectra. Several have already written preliminary versions of such software for test, and testing itself is underway. This project is sponsored by the Joint Committee on Atomic and Molecular Physical Data (JCAMP) with the support of the infrared instrument manufacturers.
Dynamic Range Considerations in the Ultimate Sensitivity of FTIR Spectroscopy
Robert L. White, Donald L. Beduhn
A dual beam FTIR is described in which both beams generated from a Michelson interferometer are detected. The Michelson interferometer used for this study contained cube-corner retroreflectors instead of flat mirrors. The retroreflectors could be used to access the modulated beam normally superimposed on incoming source radiation. Matched MCT detectors were used to measure each modulated beam. The output from these detectors were summed before digitization to reduce the dynamic range of the signal and minimize digitization noise.
GC/IR Optimal Design, A Comprehensive Study
Don Kuehl, Raul Curbelo
A theoretical model for the optimum optical design of lightpipe GC/FT-IR systems was developed. This model predicts the optimum optical design based on the maximum spectral signal-to-noise (S/N) for a given lightpipe size. Experimental measurements were made to confirm the accuracy of this model and a GC/FT-IR system based on this model was built and tested.
The Design And Performance Of A Moderate Price, Research Grade FT-IR Spectrometer
Richard Crocombe, Don Kuehl
This paper describes the design of the Digilab FTS 60 FT-IR spectrometer. Aspects of both the optical bench and the computer system are shown. The FTS 60 is characterised by high throughput, compact size, versatility and a powerful data system, based on the Motorola 68000 microprocessor.
Properties and Performance of A Rotary Scanning FTIR
M. A. Ford, A. R. Gee
The Perkin-Elmer 1700 Series FTIR Spectrophotometers* use a Michelson Interferometer in which the optical path difference is generated by rotary rather than linear motion as described by Sternberg and James'. The relative alignment of the interfering wavefronts is unaffected by any motion of the rotating assembly in all six degrees of freedom, while the OPD is generated by rotation about one axis. This configuration eliminates any need for dynamic alignment during scans and gives exceptional long term stability.
GC/FT-IR: A Comparison of Single-beam and Optical Subtraction Approaches
David E. Henry, Peter R. Griffiths
Subnanogram detection limits have not been published for any on-line GC/FT-IR system which employs light-pipes. Several approaches aimed at achieving this goal provide (in theory) the means for improving the signal-to-noise ratio (SNR) of most current systems by more than an order of magnitude. While lower detection limits are possible, the practical detection limits of a single-beam GC/FT-IR measurement remain limited by the dynamic range of most affordable analog-to-digital converters (ADC's). In GC/FT-IR a very wide dynamic range is required since the amplitude modulation due to analyte absorption is extremely small in com-parison to the strong signal at the centerburst of the interferogram.
Quality Control And Process Monitoring With FT-IR Spectroscopy
G. L. Ritter, S. R. Lowry, C. R. Anderson
The sensitivity and speed of FT-IR spectroscopy have always appealed to the quality control and process monitoring community. However, the high cost and large size of research grade instruments have limited the use of FT-IR in production environments. The development of smaller, more rugged spectrometers has created renewed interest in these applications. To meet the interest three areas become critical. •The spectrometer must have minimum down time and must be simple to service. • Quantitative analysis must be available so that an analysis may be configured easily. • It must be possible to transfer information from the spectrometer to a computer system for archiving or decision making.
CO2 Band Intensities in the 9.4 and 10.4 µm Regions
M. S. Abubakar, J. H. Shaw
The intensities, widths and positions of lines of 19 CO2 bands in the region 790 - 1110 cm-1 have been determined by the method of whole-band, nonlinear, least-squares analysis from a Fourier Transform spectrum of CO2 recorded at room temperature, a pressure of 177 torr and a path length of 474 m. The resolution is about 0.07 cm-1.
Infrared Fourier Transform Emission Spectroscopy of CuH and NeH
R. S. Ram, P. F. Bernath, J. W. Brault
The vibration-rotation spectra of CuH and Nee were detected by infrared emission from a copper hollow cathode lamp with the Kitt Peak Fourier transform spectrometer. The (1,0), (2,1) and (2,0) bands of °3CuH and 65CuH were found as well as the (1,0), 2,1) and (3,2) bands of NeH+. The Ne and H2 pressures in the lamp were 2 torr and 30 mtorr, respectively. By replacing the H2 with D2 the (1,0) and (2,1) bands of NeD+ were observed. CuH is the first metal hydride for which a vibration-rotation emission spectrum has been detected. Dunham coefficients, including the effects of Born-Oppenheimer breakdown, were extracted from the data.
Synthetic Spectra For The Analysis Of Far IR Stratospheric Emission Measurements
B. Carli, M . Carlotti, B. M . Dinelli, et al.
A radiative transfer model is used for the calculation of synthetic spectra of the far infrared stratospheric emission which are compared with measurements obtained with a balloon-borne FT spectrometer. This analysis technique has been used for the retrieval of concen-tration profiles of minor stratospheric constituents, as well as for an assessment of the present limits of our modelling and measurement capabilities.
Atmospheric Trace Gas Measurements Using Matrix Isolation - FTIR Spectroscopy
David W . T . Griffith, Ernst Berger, Dieter Ihrig, et al.
The technique of matrix isolation combined with Fourier transform infrared spectroscopy has been developed as a sensitive method for atmospheric trace gas analysis. Matrices of solid CO2 are grown at 77K using natural CO2 as the matrix material, in which the atmospheric trace gases are embedded. Analysis of the matrix by FTIR absorption spectroscopy yields simultaneous measurements of a wide range of atmospheric trace gas species, including unstable and reactive ones, with detection limits typically around 101i molecules or 10-11 mixing ratio from a 20-40 litre air sample.
A FTIR Far-Infrared Study Of Isotactic Polypropylene Polymorphs
D. R. Beckett, J. M. Chalmers, M. W. Mackenzie, et al.
Fourier transform far-infrared spectra over the range 500-100 cm' have been recorded of crystalline isotactic polypropylene (IPP) in four polymorphic forms at 293 and 100K. Differences in the spectra, in particular splitting of certain A line-group modes, reflect the environments of isolated IPP chains within the particular unit cell configurations of the crystal form.
Fourier transform-infrared (FT-IR) Spectroscopic Study of Proton Transport in H-bonded solids
Paul J. Wooldridge, J. Paul Devlin
The equilibrium proton concentration in pure cubic ice is sufficiently low at T<125K that the proton hopping step required for the conversion of isolated D20 molecules to neighbor coupled HOD molecules ((HOD)2) is extremely slow. Thus no isotopic exchange is observed. However, it is shown in the present study that cubic ice is subject to photoionization by the uv radiation of a mercury resonance lamp. At low temperatures, the mobile protons that are formed are immediately immobilized in shallow traps after producing only a very limited conversion of D20 to (HOD)2. Above 110K these shallowly trapped protons are released at a significant rate, establishing a psuedoequilibrium concentration of mobile protons that sustains the reaction D20 + H2O "f; (HOD)2 allowing equilibrium to be established. The kinetics for this proton transfer reaction has been followed by monitoring the concentration of D20, (HOD)2 and isolated HOD using FT-IR methods.
Study Of Anharmonic Vibrations By Low Frequency FT-IR Spectroscopy
J. R. Durig, T. S. Little, G . A. Guirgis
Our research efforts in the area of anharmonic vibrations, which include the skeletal bending modes in quasilinear molecules, the ring puckering and ring bending modes in four- and five-membered rings, and the torsional modes for molecules with two internal C3, rotors, have been concentrated more recently on the determination of the asymmetric potential function governing the internal rotation in a number of three-membered ring carbonyl compounds, substituted allylic compounds, propenoyl halides and alkyl halides. Although asymmetric potential functions had been previously proposed for some of these molecules, relatively few of these can be given a significant level of confidence due to a number of experimental problems which have been previously encountered. For example, far infrared spectroscopy has been used in the past for the determination of asymmetric torsional frequencies but we have found that a resolution of at least 0.1 cm-1 needs to be used to record the low frequency data because many torsional bands are extremely sharp and therefore were not even observed with the relatively low resolution utilized. Additionally, insufficient resolution may result in misleading relative intensities of the Q-branches so that incorrect assignments have resulted. In many cases, due to symmetry, both infrared and Raman spectroscopic results are needed to identify the high and low energy conformers. Examples will be provided to demonstrate how asymmetric torsional data can be used to obtain potential constants.
Production And Analysis Of Heavy Atom Spectra With A High Resolution Fourier Transform Spectrometer
Rolf Engleman Jr., Byron A. Palmer
We have developed several sources of atomic spectra suitable for use with a high-resolution Fourier transform spectrometer (FTS). Such sources must produce the required spectra, be relatively stable and noise-free, and yield narrow spectral lines. These sources are the hollow cathode lamp (HCL), the electrodeless discharge tube (EDL), furnace absorption, and the inductively coupled plasma (ICP). The great wavenumber and intensity accuracy of the FTS can be utilized in the analysis of complex spectra in several ways that were not practical with earlier, less precise spectra.
A Slightly-Cooled, High-Resolution Michelson Interferometer For Limb Emission Measurements From Space
F. Fergg, H. Fischer
Spaceborne Fourier Transform Spectrometers can be used to obtain IR limb emission spectra from which profiles of temperature and minor constituents can be derived simultaneously in the middle atmosphere. A corresponding experiment, called MIPAS (Michelson Interferometer for Passive Atmospheric SoundiTig) is und-6- development in Winich. MTPAS utilize? a novel type of interfero-meter which uses two double passed triple mirrors both being fixed to a rotating structure to produce optical path difference (P. Burkert, F. Fergg and H. Fischer, IEEE Transact. on Geosc. and Remote Sens. Vol GE-21, 345, 1983). A He-cooled version of MIPAS for broadband emission measurements was described previously (H. Fischer, F. Fergg, H. Oelhaf, D. Rabus, W. Volker and P. Burkert, Beitr. Phys. Atm. Vol. 56, 260, 1983).
Spectral Directional Emittance Measurements In The Wavelength Range From 1 µm To 15 µm
K. Gindele, M. Kohl, M. Mast
It is the spectral emittance which governs the thermooptical behaviour of surfaces and coatings. It is also the spectral emittance which causes the most serious measuring problems in characterizing coatings. In principle there are two methods: the measurement of the emitted thermal radiation of heated samples and the measurement of the reflectance of opaque samples ( E( X) = 1 - 9(X)). The determination of the reflectance requires the measurement of the radiation reflected into the whole hemisphere, since most of the investigated surfaces are reflecting diffusely. In the spectral range from 1 pm to about 15 μm this can be done with the aid of integrating spheres.
Vibrational Analysis of 1H-labelled Propanes In The 11500 to 100 cm-1 Spectral Region
K. M. Gough, F. L. Baudais, H. L. Casal
The gas phase infrared spectra of specifically 1H-labelled propanes CHD2CD,CD, and CD3CHDCD3 together with the spectrum of CD3CD2CD3 have been measured between 11500 and 500 cm 1. Assignments of these spectra in the fundamental and overtone regions are proposed. The Raman spectra between 100 and 3000 cm-1 of the same compounds are also reported; they are necessary to give the full view of the vibrational spectrum at the fundamental level. The major spectral features of the overtone spectral region can be explained on the basis of coupling between overtones of C-H stretching vibrations and CHD deformation vibrations. Fermi resonance coupling interactions between the two types of overtones are stronger with increasing overtone number. The present results show that there is an effect on isolated C-H stretching frequencies due to deuterium substitution.
FT-IR Isotopic Shifted Spectra Of Calcium Silicates
Miroslaw Handke
Polycrystaline silicates IR and Raman spectra in the range of internal complex anion vibrations are due to crystal field splitting and Davydov's effect are complicated and therefore, correct bands assignement is fundamental problem. The 28Si - 30Si isotopic effect observation is very helpful for better spectra understanding. Because of FT-IR spectroscopy advantages, the accuracy of isotopic bands shift measurements is satisfactory even for small (ca. 6% ) silicon isotopes mass difference. Based on isotopic data, the force constants calculations with molecular approximation for silicates complex anion has been performed.
A Study Of The Order-Disorder Phase-Transition In 2-adamantanone by FT-IR Spectroscopy
Pierre D. Harvey, Denis F. R. Gilson, Ian S. Butler
The 2-adamantanone molecule undergoes a phase transition from a disordered plastic phase (Fm3m, Z = 4) at room temperature to an ordered phase at lower temperature. The phase transition has been monitored by variable-temperature FT-IR spectroscopy. A large hysteresis effect ((~50 K) is observed between the cooling and heating cycles. From the numerous splittings observed, with non-degenerate species yielding at least four components, the low-temperature ordered phase is believed to have at least 4 molecules per unit cell.
Variable Temperature FTIR Spectroscopy Of Inorganic Cyanide Complexes
D. Melick, R. H . Herber
Variable temperature Fourier transform infrared spectroscopy can be used as a sensitive technique for the study of intermolecular bonding forces in solids. Because of the different types of bonding interactions possible for the cyanide moiety and the large oscillator strength of the CN stretching frequency, the infrared active vibrations of this group can serve as a diagnostic reporter entity for the study of a wide variety of inorganic cyanide complexes. The temperature dependence of vcN over the range 78 < T < 300 K are reported in the present study.
Emission Characteristics Of Microwave Plasma In The Near Infrared
Joseph Hubert, HuuVan Tra, Frederick L. Baudais
Fourier transform spectroscopy has not been widely used to detect atomic emission from atmospheric plasmas. Fourier transform spectrophotometers are capable of the simultaneous and continuous measurement of atomic emission, and thus allow flexibility in the choice of emission lines for quantitative analysis and in the ability to correct for background changes. The combination gi.f the Surfatron cavity for the generation of atomic emission in a microwave induced plasma and a FT spectrophotometer for the detection and quantitation of atomic species eluted from a gas chromatograph is reported for a number of the nonmetallic elements.
Structure and Dynamics of Binary Solid and Liquid Mixtures: Sampling Techniques for Mid and Far IR Fourier Spectroscopic Studies
Helmut Kollhoff, Erich Knozinger, Walter Langel
IR and Far IR Fourier spectroscopic studies of liquified and crystallized gas mixtures at low temperatures require special sampling techniques. Appropriate experimental techniques have been developed which provide a free gravity-held plane-parallel layer of the liquid or solid sample. Conventional studies in liquid solution as well as matrix isolation experiments are possible.
Infrared Studies Of Acceptors In Gallium-Arsenide
W. J. Moore, B. V. Shanabrook
The ls-2p electronic intrasite transitions and local vibrational modes (LVM) of impurities and defects in GaAs are studied in FTIR transmission spectroscopy. These features are observed in as-grown samples and in samples which have been compensated by irradiation with 2 MeV electrons. The position of the Fermi level is monitored by observing the lowest energy ls-2p transition.
The Los Alamos Fourier Transform Spectrometer
Byron A. Palmer, Rolf Engleman Jr.
The Los Alamos National Laboratory is building a Fourier Transform Spectrometer (FTS) that will be the most powerful and precise instrument of its kind in the world. The FTS will have a maximum resolution of 0.001 cm-1 when the light is double passed. The A/D con-verter will have a dynamic range of 22-bits and will acquire points at a rate of 40 KHz. A digital filter will be used to reduce the bandwidth of the data and will output data points at a rate of 4-5 KHz. Scan times will be typically 4-5 minutes for a high-resolution scan. The servo control will be accurate to 1-2 millifringes of 632.8 nm He-Ne laser light. The spectral range will be from 200 to 20 000 nm (500 to 50 000 cm-1). We will be able to ac-quire multiple scans to help improve the signal to noise.
Microcomputer-controlled Fourier Transform High Resolution Spectrometer
A. Barbe, D. Courtois, A. Delahaigue, et al.
A 3 m maximum path difference Fourier interferometer is described. The optical design is Connes'type. Interferograms are recorded using the stepping mode. We used a new design microcomputer servo-controlled system. Interferogram recording is completely assisted by this computer. The apparatus function is presented.
Time-resolved Infrared Studies Of Coordinatively Unsaturated Metal Carbonyl Species
Avtar S. Nazran, Michel Drouin, David M. Rayner, et al.
Fast laser based time-resolved infrared absorption spectroscopy has been applied to the study of the ultraviolet photolysis of the pseudo-nickel carbonyl, tricarbonylnitrosocobalt. The kinetics of the disappearance of the starting molecule and the formation of a coordinatively unsaturated cobalt species, tentatively assigned as Co(C0)2, have been observed. Rate constants for the secondary reaction of this species with the parent compound, and with CO, have been determined. A reaction mechanism is proposed.
Selective Cluster Formation In Cryogenic Matrices Monitored By FAR-IR And MID-IR Spectroscopy
O. Schrems, M. Huth, H. Kollhoff, et al.
Selective formation of molecular microclusters isolated in cryogenic solids is shown to be an effective way to obtain detailed information about structures and intermolecular interactions in condensed matter. New techniques are reported which allow the generation of well-defined molecular aggregates in cryogenic matrices by: (a) time- and temperature-controlled diffusion of monomeric molecules in highly diluted solid solutions; (b) condensation of "size-selective" pulsed supersonic beams, and (c) photochemical decomposition of suitable parent molecules isolated in solid inert gases. The efficiency of these methods is demonstrated with hydrogen cyanide as model system. It is shown that locally stable (HCN)n microclusters (n = 2, 3, 4) can be obtained selectively. The influence of the cluster size on intra- and intermolecular vibrational modes has been studied in detail and structural information have been derived from the spectral data. It is shown to be particularly advantageous to use a modified FT-IR spectrometer which permits the recording of mid-ir and far-ir spectra of the very same matrix sample.
Far Infrared Fourier Transform Spectroscopy for the Mixed Crystals Cd1-xMnxTe
S. C. Shen, H. J. Ye, L. S. Kan, et al.
We report here the acoustic local mode and TA band mode for the lattice vibration of the mixed crystals Cd1-xmnxTe as observed by very far infrared spectra. The occurence of the acoustic local mode and the weakly optical activity of TA mode induced by crystalline-mixing are discussed in light of the defect lattice dynamics.
Application of FTIR spectroscopy In Laser-Induced Chemistry
A. Stanley, R. Johnson, J. McDonald, et al.
FTIR spectroscopy is routinely used by this research group as a tool in laser-induced chemistry for identification of end products, reaction mechanisms and kinetic studies. Specific recent studies have included the dissociation of the C-0 bond in alcohols and phosphorus compounds, the formation of polycrystal-line germanium films from germane and the kinetics of the laser-induced chemistry of allylic species and NF3/NO reactions. The specifics of the experimental techniques used in these investigations have been adequately described elsewhere)-2. Fundamentally, the technique is simply the irradiation of gas phase samples using a continuous wave CO2 laser at the frequency of an absorption band in the molecule which is resonant with the output of the CO2 laser.
Stratospheric Cryogenic Interferometer Balloon Experiment (SCRIBE) Interferometer Atmospheric Emission Spectra
George A. Vanasse, David G. Murcray, Frank H. Murcray, et al.
Balloon-borne measurements were made using the Stratospheric Cryogenic Interferometer Balloon Experiment (SCRIBE) interferometer from Holloman AFB on October 1983 and July 1984. The instrument obtained 0.06cm-1 resolution data with good S/N in the spectral region of 600 to 1400cm-1 with an interferometer scan time of 25 seconds. Representative spectra will be shown which demonstrate the capability of the SCRIBE interfero-meter for atmospheric emission measurements. The SNR achieved in the 750 to 1000cm-1 region was high permitting the measurement of emission gases with stratospheric concentrations of the order of PPB to a resolution of 0.06cm-1. Emission spectra of trace gas species easily identified will be presented; these include HNO3, CF1C13 (F11), FC2C12 (F12).
Effects Of Impurity On The IR Absorption Bands Of Si-H Centers
Du Yongchang, Zhang Yufeng, Weng Shifu
The IR bands in N-type and P-type floating-zone silicon grown in hydrogen atmosphere before and after neutron irradiation have been studied using FT-IR spectroscopy. The effects of impurity on the IR bands of Si-H centers have been observed.
The Fourier Transform Infrared Spectra Of Liquid Water
Weng Shifu, Wu Jinguang, Xu Guangxian
Taking the advantage of the high resolving power and sensitivity of the FTIR spectrometer and using multiple scanning technique, we have successfully resolved the stretching vibrational band of liquid water near 3400 cm-1 into 8 peaks of rotational fine structure and determined the molar absorptivities of various vibrational modes.
The VCD Spectrum Of 2-Methyl Oxetan
R. A. Shaw, N. Ibrahim, L.. A . Nafie, et al.
The VCD and absorbance spectra of 2-methyl oxetan are reported for the region of 800-1500 cm-1. A force field consistent with experimental vibrational spectra is derived by an ab initio calculation at the STO-3G level, and is used to compute the VCD signs and intensities using the fixed partial charge (FPC) method. The VCD signs are predicted correctly for all observable bands save one.
FT-IR Study Of Rare Earth Naphthenates In The Extract Phase
Jinguang Wu, Hongcheng Gao, Tianzhu Jin, et al.
The FT-IR spectra and subtraction spectra of fifteen rare earth naphthenates in the extract phase have been studied with the following results: (1). The symmetrical stretching vibration band 04) of the carboxylate ion in the extracted rare earth naphthenates can not be found in the used FT-IR spectra, but we have found them in the subtraction spectra. (2). Then the differences between j),ms (asymmetrical frequency of COO ) and y can be obtained from which the coordination structure of rare earth naphthenates may Be discussed. (3). By this way, the effect of coordination of the secondary octyl alcohol (ROH) with the rare earth naphthenates was observed.
FT Infrared and Raman Spectroscopic Studies On Dynamic And Interaction Processes In Liquid Benzonitrile
F. Guillaume, J. Yarwood
Infrared and Raman studies on benzonitrile have been employed to study the reorientation and vibrational relaxation processes in the liquid and in dilute solutions of a range of solvents. Initial results confirm the rather slow reorientation of the CN group transition dipole. The vibrational relaxation processes seem relatively insensitive to changes in the surrounding potentials. Vibrational-rotational coupling is shown to be insignificant.
Fourier Transform Infrared Study On The Hydration Of Poiyadenylic Acid (Poly A). II. Dynamic Hydration And Dehydration Properties
Yu Baozhu, Guo Hai, Wu Jinguang
The FT-IR spectra of Poly A film at 0.0,'Zffl to 100.0RH approached by dynamic equilibrium were measured according to the ascending and descending order of relative humidity. As compared with the static hydration the experimental phenomena and effects are similar in both processes. however, for the most obsorotion bands the dynamic hydration begin at a lower relative humidity and behave a faster and more even hydration rate than in the static case. The experiments also show that the hydration and dehydration process are irresvertible and the hydrating water could not be desorbed in low relative humidity. This indicates that the water molecules combined with Poly A have strong chemical bonding.
Time-resolved FTS of the IR Emission Of A Pulsed Glow Discharge
W. Barowy, H. Sakai
At the University of Massachusetts we are applying the technique of time-resolved FTS to the study of the negative glow IR emission spectrum of a low pressure glow discharge. For a given pressure and peak excitation current, we have found that the infrared spectral Features of N2 emission vary markedly as a function of both pulse repetition rate and pulse width. In order to observe this behavior without erroneous spectral artifacts, real-time signal processing has been incorporated into the experiment, with special emphasis on D.C. restoration. The relaxation phenomena inherent in our source, coupled with low S/N ratios and high duty cycle, require unique signal processing that is facilitated by computerized techniques.
Performance of an Open Path FTIR Air Monitor
Pamela S. H. Fitch, Sidney W. Fleming, Bruce C. McIntosh
A new type of hazardous gas monitoring system has been installed and tested in a chemical manufacturing facility. It detects the possible presence of several hazardous gases in an open air path by FTIR Spectroscopy. A ruggedized commercial FTIR instrument is coupled through a 10" beam expanding telescope through a path approximately 100 meters long. The FTIR detector is mounted at the focus of a second identical telescope. This paper des cribes the system and the results of the testing.
Enhanced Kinetic Ftir Observation Of Transient Species Generated In SITU By Pulsed Laser Photolysis
M. S. Paquette, H. D. Gafney, M. S. Darsillo
Modern, rapid scanning FTIR spectrometers allow efficient real time sampling of time dependent phenomena such as chromatographic peak elution and chemical reactions. We have particular interest in kinetic and mechanistic studies of catalytic reactions as well as rapid chemical reactions. Using appropriate reactor-cells, we have the potential for observing in situ the existence and fate of short lived species. However, these transient materials, by virtue of their reactivity, are usually difficult to observe in their unenhanced amounts. We have developed techniques which employ ultraviolet, visible, and infrared laser pulses to stimulate reactions in solutions and on surfaces enhancing the occurrence of reactive species. We will present results of an in situ FTIR study of the laser photolysis of iron pentacarbonyl in homogeneous solu-tion and on a porous vycor glass support. An analysis of spectral data from several experiments enabled us to identify reactive iron subcarbonyl species as well as stable compounds and clusters. Spectral stripping procedures were used to quantitate individual components in the kinetic FTIR spectra yielding catalyst lifetimes as short as 0.2 sec. From these experiments we have postulated comprehensive models describing chemical, photochemical, and physical processes in stoichiometric and catalytic reactions of iron carbonyl complexes.
Methods For Determining Reactive Intermediates By FT-IR Spectroscopy
R. J. Rosenthal, F. T. Walder
The ability to actually examine a reaction mechanism is limited by the various intermediates along a reaction coordinate. Detailed information concerning a mechanism is critical for the thorough understanding of the chemistry and physics involved. Matrix isolation affords the opportunity to slow down or freeze out molecular or atomic species which would be unobservable at or near room temperature. In combination with FT-IR, matrix isolation techniques can be used to obtain high quality spectral data of various intermediates.
New High Resolution Infrared Fourier Transform Spectrometer And The First Results In Atomic, Molecular And Crystal Spectroscopy
N. I. Agladze, A. A. Balashov, V. S. Bukreev, et al.
Characteristics of a new laboratory high resolution (0.005 cm1) Fourier transform spectrometer UPS-02 for the 0.8-100 mkm spectral range are presented. A short review of spectroscopic investigations carried out with this instrument is given.
IR Spectroscopy Of H-bonds : Analysis Of A Strongly Anharmonically Coupled Vibration
Y. Marechal
IR spectroscopy is a powerful technique to extract information on the dynamical behaviour of H-bonds, which may be considered as the central reaction site in biology at the molecular scale. H-bonds have dramatic effects in IR spectroscopy which are illustrated in Figure 1
The Taser Induced Fluorescence Spectra And Decay Lifetime Of NI2+ Doped Chrysoberyl
Ji Hanting, Wen Genwang, Oian Jun, et al.
This paper reports the experimental results on the fluorescence spectra and decay lifetime of 3T2---3A2 vibronic transition of NI2+ : BeAl204 with LIFM. The center wavelength of fluorescence spectra is 1.33u , the bandwidth (FWHM) is 0.14u (1.26 - 1.40u), and the center red-shift of fluorescence spectra in relative to absorption spectra is 0.225u at room temperature (300k). The radiation lifetime is 3T2 band is 198 us.
Surface Electromagnetic Wave Fourier-Transform Infrared (FTIR) sPectroscopy Of Very Thin Films
G. N. Zhizhin, M. A. Moskalova, V. A. Sychugov, et al.
Surface electromagnetic wave (SEW) spectroscopy is a new high sensitive technique of the surface analysis, that recently was used only in the narrow spectral interval contai-ning tunable CO2 laser lines.1 Use of thermal sources of infrared (IR) radiation to excite SEW is difficult because of the small coupling efficiency. For effective excitation it is necessary to have an extremely collimated beam that is easy to obtain with laser sources, but is difficult with an extended thermal source. To detect the very weak SEW in the later case, instruments of extremely high sensitivity are necessary. We used the IR Four4r-transform spectrometer FTS-20B (Digilab) equipped with HgCdTe cooling detector e,3 . Two-mirrors SEW unit containing the sample (see Fig.1) is placed into the sample compartement of the instrument. Grating SEW coupling is used. Two gratings (dimensions 10x5 mm2) were etched on the glass plate with 10 mm separation. Then, the plate was coated by the metal (copper). SEW excitation condition for light incidence =glee and wavevector kx is k 27r1) sine + 271 E a
Non-Standard Sampling Techniques For Infrared Spectroscopy
R. L . Barbour, M. D. Smith, D. A.C. Compton, et al.
A number of sample handling methods are discussed which have allowed us to carry out FT-IR analysis of samples that are not considered easy to examine. Examples given discuss the far-infrared examination of air sensitive solids using a polyethylene bag as a sample holder, use of an infrared microscope for examining relatively macroscopic samples and corroded surfaces, the sampling of volatile liquids using a gas cell, and the in-situ study of coatings curing on a steel surface.
Pressure effects on the infrared spectrum of crystalline quartz
F. L. Baudais, P. T. T . Wong, D. J. Moffatt
The effect on the infrared spectrum of crystalline a-quartz by applying external pressure with a diamond anvil cell was systematically measured between atmospheric and 50 kbar. A large pressure induced frequency shift and TO-LO splitting in several phonon bands has been observed.
Diffuse Reflectance Infrared Spectroscopic Studies Of Aromatic Ketones Included In Silicalite
H. L. Casal, P. W. Yang
Diffuse reflectance (DR) infrared spectra of aromatic ketones included in the channel system of the hydrophobic zeolite silicalite have been obtained. These spectra reveal the existence of multiple inclusion and/or adsorption sites available in accord with previous NMR, crystallographic and photophysical studies. Photochemical reduction of included dibenzyl-ketone has been followed by in situ UV photolysis. Formation of products can thus be followed as the reaction proceeds with no need of chemical extraction. Comparison with the spectra obtained using silica gel as support has shown that the dibenzyl molecules included in the channel system are more reactive that surface-adsorbed species.
FTIR Diffuse Reflectance Studies On Catalyst Systems Using An Environmental Cell
N. Poole, J. M. Chalmers, N. Moore
Fourier transform infrared diffuse reflectance (DRIFT) studies using a commercial diffuse reflectance attachment and heatable-evacuable cell are described. The technique provides a convenient means of examining powder materials of catalytic interest, and this is illustrated by studies of acrolein adsorbed onto potassium phosphomolybdate, and methanol conversion and pyridine adsorption on HZSM-5 zeolite.
Application of Diffuse Reflectance FT-IR Spectroscopy for the Surface Study of Kevlar Fibers
E. G. Chatzi, H. Ishida, J. L. Koenig
The surfaces of Kevlar-49 aramid fibers, being used in high-performance composite materials, have been characterized by diffuse reflectance Fourier transform infrared (FT-IR) spectroscopy. Enhancement of the surface selectivity of the technique has been achieved using KBr overlayers. The water absorbed by both the skin and the core of the fibers has been characterized by using this technique and the accessibility of the fiber functional groups has been evaluated.
Energy Difference Between Specific And Localized Conformational Isomers In Liquid n-alkanes: Nonadecane.
G. Conti, P. Jona, G. Zerbi, et al.
It is well known that the enthalpy difference between rotational isomers in a simple n-alkane molecule can be measured from infrared and Raman spectra when the intensity ratio between two characteristic bands can be plotted as function of temperature. From an Arrhenius p1lot the energy difference can be easily derived and it has been derived for many molecules . It is also known that, when a CH0 group in n-alkane chain is replaced by a CD2 group, its rocking motion gives rise to bands at different frequencies deriending on the onformation about the C-C bonds at Tither sides of the CD group (TT 615 cm , TG 650 cm-1 inside the -1 alkane chain; T 615 cm , G 650 cm at the chain end ). We use these selective conformational markers in the attempt to explore experimentally whether the conformational flexibility of the alkane chain is different in the middle or at the chain end.In other words we whisk to measure the energy difference between TT/TG or T/G conformational pairs. This can be done by measuring the intensity of specific conformational markers as function of temperature and using an Arrhenius plot. The rotational isomeric state model by Flory has also been studied.
A Method To Explore Three Dimensional Absorption In Polymers
Leslie J. Fina, Jack L. Koenig
Any processing technique induces orientation in a polymeric system. We have developed techniques originally explored by R. Zbinden spectroscopy Di Hical Polymers, Academic Press, N.Y.,1964) and P.G.Schmidt (J.Polym.Sci. Al, 1271, 1963) to study the trichroic orientation effects. Using a tilting procedure the principal axes of the absorption ellipsoid are calculated and the isotropic-equivalent or structure factor (Ao) spectrum is found. With trichroic information the assumption of transverse isotropy in one-way drawn samples is no longer necessary and, in fact, is shown to be invalid in some cases. The method is applied to two polymer systems, polyethylene terephthalate (PET) and polyvinylidene fluoride (PVDF). In PET the rotational isomeric content in the crystal and amorphous phases is characterized from the Ao spectra by the method of least-squares curve-fitting. In PVDF, frequency shifts in the plane perpendicular to the draw direction are observed indicating single crystal-like orientation behavior.
Thermal CalibratiOn of a Low Temperature Invar Sample Cell for FTIR Spectroscopy
L. M. Casson, R. H. Herber
A sample cell, capable of supporting standard 13 mm diameter pressed pellets, and suitable for mounting in a commercial cryostat, has been constructed of Invar, and fitted with two thermocouple sensors for operating in the range 4.2 < T < 300 K. The thermal lag between the temperature of the experimental sample and the sensor reading has been determined by monitoring four phase changes in covalent solids which can be used as "infrared thermometers". In the temperature range 77 < T < 300 K this thermal lag is less than 0.5 degrees.
Fourier Transform Infrared Surface Electromagnetic Wave Spectroscopy of polymer thin films on metal substrate
Yuichi Ishino, Robert T. Graf, Hatsuo Ishida
FT-IR Surface Electromagnetic Wave Spectroscopy utilizing the Otto configuration is applied to the study of a thin film of polyvinyl acetate) on a copper substrate. Multiple reflection modification was effective to enhance the sensitivity of this technique.
Lower Limit Of The Thickness Of The Measurable Surface Layer On Infrared Absorbing Substrate By FT-IR-ATR Spectroscopy
Koji Ohta, Reikichi Iwamoto
Based on verification of Harrick's relation between absorbances of absorption bands and the thickness of the surface layer probed in ATR spectroscopy, we have studied the lower limit of the thickness of a surface layer on an infrared absorbing substrate that can be measured by spectral subtraction of FT-IR-ATR spectra. Spectral observability of a surface layer of a thickness is predictable by comparing the expected absorbances of the bands of the surface layer with the detectable least signal increment obtainable from the noise level of a spectrometer. The limit of the thickness is, in general, 10 to 50 A for polymers.
IR and Far IR Characterization of High Surface Materials and Adsorbed Species
P. Hoffman, E. Knozinger
This paper reports recent progress made in FTIR investigation of high surface materials such as SiO2 by means of the transmission technique. FTIR spectroscopy provides the following advantages: (a) Improved resolution makes the correct detection of band shapes of absorptions possible which are assigned to free surface OH groups. (b) Part of the finger print region and the total of the far IR range are now accessible. (c) Difference spectra allow the detec-tion of minute changes in the surface induced by variation of physical or chemical parameters.
Surface Adsorbed Species: IR Studies of SO2 and H2S Adsorbed on Oxides
J. C. Lavalley, J. Lamotte, O. Saur, et al.
The adsorption of SO, on alumina leads to the formation of several species such as SO3=, HSO3- and coordinated SO2. In addition sulfates are produced under oxidizing conditions. However, definitive vibra- tional assignments are hampered by the paucity of data below 1000 cm-1 where alumina is strongly absorbing. On the other hand, silica is partially transparent at low frequencies and subtractive IR spectroscopy has permitted us to observe bands which are tentatively assigned to the SO bending modes of bisulfite (HSO3-, 635 cm-I) and disulfite (S2O5-, 660 cm-I) surface species on sodium promoted silica catalysts when SO and H2O are coadsorbed. H2S addition to a surface pretreated with SO2 gives rise to a new band at 680 cm-1 which is pos- sibly due to S2O3 orS2O on the surface. The results are discussed in terms of intermediates in the Claus process (2 H2S + SO2 + 3/n Sn + 2 H2O).
Experimental and theoretical characterization of surfaces using infrared reflectance spectroscopy
David K. Ottesen, Lawrence R. Thorne, Robert W. Bradshaw
External reflectance infrared spectroscopy has been used to study the formation of thin oxide films on metals. Experimental data have been acquired with a Fourier transform infrared (FT-IR) spectrometer using a polarized beam at high angles of incidence, and have been compared with theoretical calculations.
Characterization of Thin Films on Glassy Carbon Electrodes by Infrared External Reflection Spectroscopy
Marc D. Porter, David L. Allara, Thomas B. Bright, et al.
The utility of infrared external reflection spectroscopy [IR-ERS] for the characterization of thin organic surface structures on nonmetallic substrates, such as glassy carbon [GC], has been examined. Surface sensitivity as a function of the angle of incidence and polarization was determined by calculations of mean-square electric field values [MSEF1. Band shapes for IR-ERS spectra, obtained at optimum conditions for thin films (80-3500 A) of poly(methyl metharcylate) [PMMA] on GC, were severly distorted compared to those obtained with transmission spectroscopy. The IR-ERS spectra were accurately modeled (±1096) by classical electromagnetic theory, indicating that the distortions resulted from the inherent physical differences between ERS and transmission measurements.. These results also demonstrated the feasibility of performing quantitative IR-ERS at nonmetallic substrates.
The Characterization Of Structural Disorder In Thin Films At Elevated Temperatures By Spectroscopic Methods
J. F. Rabolt, J. Rabe, C. Brown, et al.
Changes in the IR bandshapes and shifts in frequency can provide an insight into the nature of molecular motion occurring prior to structural reorganization which accompanies a phase transition. In the case of Langmuir-Blodgett films of polymerizable molecules, often there is competition between polymerization and the occurence of structural disorder when monomeric films are subjected to elevated temperatures. To distinguish these two mechanisms, a series of melting experiments on L-B films of cadmium arachidate were under-taken using grazing incidence reflection techniques to assess the change in molecular orientation and order as a function of temperature: the spectroscopic observations being correlated with DSC measurements. Similar thermal and spectroscopic studies of octadecyl-fumarate [H(CH2)100C(0)CHCHC00],Cd indicated that although the resulting polymer was structurally similar to that obtained by UV irradiation at ambient temperature, the orientation of the hydrocarbon side chain and the backbone bridging group (-0C(0)CHCH-) was disrupted owing to the thermal disorder introduced prior to or at the time of polymerization.
Surface Organization of a Spontaneously Adsorbed Monolayer of Arachidic Acid on Silver
N. E. Schlotter, T. Bright, D. L. Allara
Grazing incidence infrared (GI-IR) spectra of spontaneously adsorbed monolayers of arachidic acid on ambient silver surfaces have been recorded. These spectra are very similar to previously obtained measurements on Langmuir - Blodgett (L-B) deposited films prepared from the corresponding carboxylate salts indicating great similarity between the L-B and spontaneously formed films. The acidic head group has reacted with the silver/silver oxide surface to form a carboxylate salt. Additionally, the hydrocarbon chains have assumed a planar zig-zag conformation. These chains are oriented approximately normal to the surface. The spectrum of arachidic acid, CH3(CH2 -) 18COOH, indicates an orthorhombic subcell packing arrangement. Studies with isotopically labeled n-alkanoic acids have been carried out to confirm some mode assignments.
Reflection-absorption IR Spectroscopy Of Organic Monolayers On Aluminum Surfaces
M. Fairlie, B. R. Pathak, R. S. Timsit
The IR absorption spectrum of stearic acid monolayers on oxidized Al surfaces has been investigated as a function of substrate temperature. The spectral changes observed at elevated temperatures are associated with increased disorder in the adsorbate. These changes are reversible on cooling if the maximum temperature reached during heating does not exceed a critical value. Recovery generally occurs over a time interval of hours. Similar results were obtained for stearic acid bi-layers deposited on gold substrates.
Surface Studies Of E-glass Fiber Composite Interfaces Using Diffuse Reflectance And Photoacoustic FTIR Spectroscopy
Marek W. Urban, Jack L. Koenig
DRIFT and PAS FT-IR techniques have been applied to quantitative analysis of coupling agent, N-2-aminoethyl-3-aminopropyltriethoxysilane (i-AAPS) on the E-glass mats. It is shown that both techniques are sensitive to the surface treatment and can successfully be used to quantitatively analyze the surface species. This quantitative approach is shown by a relationship between intensities of the C-H stretching mode as well as the band originating from the E-glass (1638 cm -1) to the concentration of the coupling agent in the aqueous solution. Although similar relationships are found for the PAS and DRIFT data, the slopes and breakpoints of each calibration curve appear to be different.
FTIR Studies Of The Conversion Of Methanol On H-ZSM-5 zeolites
J. Howard, P. J. Lux, J. Yarwood
The hydroxyl groups of H-ZSM-5 type zeolite and their interaction with ethene has been studied by FTIR. Evidence is provided for (1) the existence of three types of silanol sites (2) the formation of a silanol-ethene hydrogen bonded complex and (3) the reaction of ethene, at higher temperatures, to produce non-volatile hydrocarbons. The latter involves the loss of a silanol site different from that involved in the hydrogen bonding.
Fourier Transform Infrared Study On The Hydration Of Polyadenylic Acid(Poly A). I. Static Hydration Properties
Yu Baozhu, Guo Hai, Wu Jinguang
By means of FT-IR and subtraction techniques the absorption spectra of Poly A film have been studied systematically in the 4000 to 800 cm-1 region at 25 0C as a function of relative humidities (from 0% to 100%) approached by static equilibrium. According to the frequency and intensity changes of infrared spectra it proves that the hydration of Poly A has happened mainly on the -NH2 group of base, -P02 group and ribose ring. The largest frequency shift is observed on the -NH2 band and the strongest variation in intensity is on the -NH2 band, ribose-phosphate main chain vibration and -P02 symmetric stretching vibration. The spectra of water molecule also vary obviously and split into multiple peaks during hydration.
Fourier Transform Infrared Examination Of Surface Contamination On Aluminum Coil Stock And Flavor Impact On Beverages Packaged In Aluminum Cans
D. J. Ehntholt, D. Kendall, L. W. Guilmette, et al.
Using Fourier Transform Infrared (FTIR) spectroscopy, we successfully examined low levels of organic contamination on aluminum coil stock surfaces. These organics were thought to have a significant impact on the flavor of beverages packaged in aluminum cans manufactured from these coils. By combining the data from the FTIR spectra and the results from professional panels trained in Profile Attribute Analysis, we were able to derive some strong analytical chemistry/sensory correlations. These types of correlations are useful in examining chemistry that impacts flavor and, in this instance, could lead to an on-line monitoring application.
Analysis of Catalytic Oxidation Products with FTIR
Chen C. Hsu, Joseph V. Pistritto
A Nicolet Fourier transform infrared spectrometer (60SX FTIR) was used for the identification of catalytic reaction products. A mixture of dimethyl methylphosphonate and air was passed through a catalytic reactor where oxidation catalysts with 0.16 wt% Pt and 0.01 wt% Rh was contained. The catalytic reaction products were collected in gas cells and analyzed with FTIR in conjunction with gas chromatographic analysis. The result indicated that a decomposition efficiency of 96% of dimehtyl methylphosphonate was achieved during the first eighteen hours of reaction. The details are described in this paper.
Diffuse Reflectance FT-IR For The Study Of Catalyst Treatment And Performance
Kenneth W. Van Every, Peter R. Griffiths
The study of catalysis involving metals supported on high area metal oxides presents several problems. Many of the surface techniques, including all of the electron spectroscopies, cannot be used under conditions approaching that of a reaction since they require high vacuum conditions. Infrared spectrometry has found wide application in catalyt studies, but the strong absorption and scattering by the support has sometimes made measurements difficult. Diffuse reflectance Fourier transform infrared spectrometry (DR/FT-IR) offers advantages over various transmission measurements due to its surface sensitivity and the more natural environment of the catalyst sample. The adsorption of carbon monoxide on alumina-supported rhodium catalysts has been studied extensively by a number of investigators. The infrared spectral features are found to be quite sensitive to such parameters as metal loading, treatment conditions, precursor material, and measurement conditions. Although the system is by no means well characterized at this point, the assignments of three different adsorbed species are now well accepted by most authors1,2,3. (These species are Species I, a gem dicarbonyl with bands at 2096-2101 and 2022-2032 cm-1; Species II, a linearly bonded CO on one rhodium atom, 2042-2076 cm-1; Species III, a bridge bonded CO between two Rh atoms, 1845-1900 cm-1).
Near Real Time Quantitative Gas Analysis Techniques
William F. Herget, Marianne L. Tromp, Charles R. Anderson
A Fourier transform infrared (FT-IR) - based system has been developed and is undergoing evaluation for near real time multicomponent quantitative analysis of undiluted gaseous automotive exhaust emissions. The total system includes: (1) a gas conditioning system (GCS) for tracer gas injection, gas mixing, and temperature stabilization; and (2) an exhaust gas analyzer (EGA) consisting of a sample cell, an FT-IR system, and a computerized data processing system. Tests have shown that the system can monitor about 20 individual species (concentrations down to the 1-20 ppm range) with a time resolution of one second. Tests have been conducted on a chassis dynamometer system utilizing different autos, different fuels, and different driving cycles. Results were compared with those obtained using a standard constant volume sampling (CVS) system.
Attenuated Total Reflectance (ATR) And Reflection Absorption Infrared (RAMS) Spectroscopic Analysis Of Thin Films
Richard W. Duerst, William A. Peters, W. E. Breneman, et al.
Attenuated total reflectance infrared spectroscopic (ATR-IR) analysis (also termed in ternal reflectance spectroscopy or Ins) of thin films coated on an internal reflectance element (IRE) should be considered a viable alternative to the reflection absorption infra-red spectroscopic (RAIRS) method, where thin films are coated an mirror surfaces, preliminary results have shown that reasonable, if not superior, spectra can be obtained for films as thin as 25 A (approximately a monolayer) coated on a germanium crystal.
Fourier Transform Infrared Spectroscopy Studies Of Magnetic Disk Surfaces
James L. Chao, John S. Mitchell, Yu-Sze Yen
Infrared spectroscopy offers a simple and non-destructive method for the study of particulate disk surfaces. Disk parameters that were previously difficult to obtain may now be measured insitu and in a routine manner. The infrared analysis and distribution mapping of lubricant and magnetic coating have been automated using a Fourier transform spectrometer. An integrated disk handler and software package automatically positions the disk at predetermined locations for measurement and data reduction.
Automated Infrared Spectrometer For Surface Electromagnetic Waves
G N. Zhishin, S. A. Kiselev, M. A. Moskalova, et al.
An automated spectrometer for surface electromagnetic waves (ASSEW) was designed for solution of surface problems in physics and physical chemistry, and, in particular, for the determination of optical constants of metals in the surface layer'. It could also be used for the detection and investigation of vibrational spectra in the infrared of super -thin (up to monomolecular ones) dielectric films on smooth metgl surfaces by the propa-gation of surface electromagnetic waves (SEW) excited on metals2.