Showing papers on "Fourier transform infrared spectroscopy published in 1977"
TL;DR: In this paper, a method for least-squares curvefitting of Fourier transform infrared spectra is presented for the analysis of several polymer systems by digital subtraction of spectra and a demonstration of the determination of xylene solution compositions illustrates the accuracy of the method.
Abstract: A method is presented for least-squares curve-fitting of Fourier transform infrared spectra. A demonstration of the determination of xylene solution compositions illustrates the accuracy of the method. Least-squares coefficients are shown to be valuable for the analysis of several polymer systems by digital subtraction of spectra.
119 citations
TL;DR: In this article, the authors derived the optimum volume for a flow-through gas cell used in the gas chromatography-infrared spectroscopy interface (GC-ir) is shown to be equal to the volume of carrier gas between the halfwidth points of the GC peak.
Abstract: The optimum volume for a flow-through gas cell used in the gas chromatography-infrared spectroscopy interface (GC-ir) is shown to be equal to the volume of carrier gas between the half-width points of the GC peak. The optimum length and diameter for lightpipe gas cells for GC fractions separated using ⅛ in. packed columns and support-coated open tubular columns has been calculated for infrared measurements made using a rapid-scanning Fourier transform infrared spectrometer with either a triglycine sulfate or a mercury cadmium telluride detector. A sampling trigger actuated by the inflection points of the GC peak has been shown to be superior to the more usual threshold type of trigger. Expressions for the delay time between actuation of the trigger and initiation of data collection are also derived.
66 citations
TL;DR: In this article, the regularity bands of isotactic polystyrene were determined using Fourier transform infrared spectroscopy to digitally substract the spectrum of a quenched sample from that of an annealed sample.
Abstract: The regularity bands of isotactic polystyrene are determined using Fourier transform infrared spectroscopy to digitally substract the spectrum of a quenched sample from that of an annealed sample. Crystallization-sensitive bands in the Raman spectrum are identified by comparison of the spectra of annealed and quenched samples. The normal modes of isotactic polystyrene are calculated using force fields determined for saturated hydrocarbons and alkyl benzenes. A good fit between observed and calculated frequencies is obtained. It is evident from this study that the complex behavior of certain bands in the spectrum is due to a mixing of phenyl and skeletal vibrations.
66 citations
TL;DR: In this article, a dual-beam Fourier transform infrared (FT-IR) spectrometer was used for GC-IR measurements from less than 100 ng of material, and a method for removing the solvent from the effluent from a high performance liquid chromatograph was proposed, together with a device for on-line LC-ir at the submicrogram level.
Abstract: Several different applications of Fourier transform infrared (FT-ir) spectrometry being developed at Ohio University are described. A dual-beam FT-ir system which enables identifiable GC-ir spectra to be measured from less than 100 ng of material is described. A method for removing the solvent from the effluent from a high performance liquid chromatograph is proposed, together with a device for on-line LC-ir at the submicrogram level. Calculations showing the effect of the instrument line shape function of an FT-ir spectrometer used with or without apodization on Lorentzian absorption bands are described, and the implications of the results of these calculations on spectral subtraction and remote sensing experiments are discussed.
42 citations
TL;DR: In this article, Fourier transform infrared spectroscopy has been used for the detection of thermally induced conformational changes in atactic poly(vinyl chloride) (PVC), which emphasize changes in the distribution of gauche defects in the chains as functions of temperature and annealing.
Abstract: Fourier transform infrared spectroscopy has been used for the detection of thermally induced conformational changes in atactic poly(vinyl chloride) (PVC). Difference spectra emphasize changes in the distribution of gauche defects in the chains as functions of temperature and annealing. Specific bands in the ν(CCl) and δ(CH2) regions varied with inverse temperature, allowing a calculation of the activation energies of the rotamer species. Conformational changes were also detected in quenched PVC films as a result of annealing below the glass transition temperature, Tg.
41 citations
39 citations
TL;DR: In this article, a Fourier transform spectrometer was used to record the spectrum of water vapor heated in an absorption cell at 60°C at a temperature between 4200 and 5000 cm −1.
36 citations
32 citations
TL;DR: The use of tunable uv laser systems to monitor OH radicals by their resonance fluorescence, the use of laser magnetic resonance in kinetic studies of OH, HO/sub 2/ε, and other free radicals was discussed in this article.
Abstract: Application of tunable lasers and infrared Fourier transform spectroscopy to atmospherically important systems has led to the identification and quantification of a number of species in smog chambers, in laboratory experiments, and in the polluted troposphere. Many of these are labile molecules or free radicals whose presence had been previously postulated on sound kinetics and mechanistic grounds, but not directly observed. Others had not even been suspected to exist in atmospheric systems. Additionally, the development of tunable lasers has greatly aided elucidation of the mechanisms of certain important atmospheric reactions, including primary photodecomposition processes. The paper discusses recent studies with tunable lasers and Fourier transform infrared spectroscopy in which certain free radical and labile molecular species present in ambient and simulated atmospheres were directly identified and measured. These species are significant in oxidant control either because of their mechanistic role in establishing kinetic computer models, or alternatively, because of their potential effects on health and visibility, or both. These studies include the use of tunable uv laser systems to monitor OH radicals by their resonance fluorescence, the use of laser magnetic resonance in kinetic studies of OH, HO/sub 2/, and other free radicals, the use of lasers in studying themore » modes of photodecomposition of primary and secondary pollutants, the use of tunable lasers in elucidating the photochemistry of formaldehyde, the use of long pathlength optical systems, and Fourier transform infrared (FT-IR) spectrometers with interferometers.« less
29 citations
TL;DR: In this article, the rotational lines in the P and R branches were measured to J = 165 with reference to uranium standards emitted by a hollow cathode, and the differences between the two sets of measurements were less than 0.001 cm −1, and the standard deviation between the observed wavenumbers and those calculated with the spectroscopic constants B v, D v, and H v is 0.0007 cm − 1.
29 citations
TL;DR: In this article, the infrared absorptivities for four absorption bands of gaseous ClONO2 have been measured at 0.0625 per cm spectral resolution with a Fourier transform infrared (FT-IR) system.
Abstract: High resolution infrared absorptivities of chlorine nitrate (ClONO2) are required in order to quantitatively evaluate, by examination of infrared spectra obtained recently from balloon-borne spectrometers, the possible occurrence of this compound in the stratosphere. In the present study, infrared absorptivities for four absorption bands of gaseous ClONO2 have been measured at 0.0625 per cm spectral resolution with a Fourier transform infrared (FT-IR) system. Spectra were obtained at two pressures (0.05 and 1.05 torr) of pure ClONO2 and with 125 torr of N2 added to a 0.50 torr sample. Absorptivities for a range of spectral resolutions (0.0625, 0.125, 0.25 and 0.50 per cm) have been calculated from the data.
TL;DR: In this paper, a method for measuring the infrared spectra of submicrogram quantities of materials separated by thin-layer chromatography (TLC) without removing the sample from the plate is described.
Abstract: A method is described for measuring the infrared spectra of submicrogram quantities of materials separated by thin-layer chromatography (TLC) without removing the sample from the plate. The use of programmed multiple development for the chromatography concentrates each spot of sample on the TLC plate by approximately a factor of 4 compared to conventional TLC. A Fourier transform infrared spectrometer equipped with a mercury cadmium telluride detector enables recognizable spectra to be measured in less than 10 s.
TL;DR: A phenomenon akin to higher order spectra in grating spectroscopy has been found in Fourier transform spectroscopic, while its relative intensity is orders of magnitude down from similar effects in gratings.
Abstract: A phenomenon akin to higher order spectra in grating spectroscopy has been found in Fourier transform spectroscopy. While its relative intensity is orders of magnitude down from similar effects in gratings, the high sensitivity of Fourier transform ir allows this perturbation to be detected.
TL;DR: In this article, the Michelson interferometer was used to achieve a resolution better than 0.05cm−1, the theoretical resolution being 0.03 cm−1.
TL;DR: In the spectroscopy of highly irregular samples, the spectral distortions introduced by absorbance averaging over nonuniform samples are further compounded by refractive and scattering beam distortion effects as mentioned in this paper.
Abstract: In the spectroscopy of highly irregular samples, the spectral distortions introduced by absorbance averaging over nonuniform samples are further compounded by refractive and scattering beam distortion effects
TL;DR: In this article, it was shown that the position of the uniquely bright fringe of the specimen interferogram for use as the displaced origin of computation is not important for the determination of refractive indices.
TL;DR: In this paper, the effective transmission, neglecting sample reflectance, and for not too strong absorption, is given by Te = T + (1 - T)QFΩE/4π where Te and T are the effective and actual transmission, respectively; QF is the fluorescent quantum efficiency, Ω the solid angle of light collection following the sample, and E is the collection efficiency of the interferometer.
Abstract: For samples showing appreciable fluorescence emission spectra, the effective transmission, neglecting sample reflectance, and for not too strong absorption, is given by Te = T + (1 - T)QFΩE/4π where Te and T are the effective and actual transmission, respectively; QF is the fluorescent quantum efficiency, Ω the solid angle of light collection following the sample, and E is the collection efficiency of the interferometer.
TL;DR: In this paper, the authors discuss the signal/noise ratios attainable in Fourier transform infrared (FT-IR) spectroscopy, including the magnitude of the multiplex and throughput advantages.
Abstract: There has been considerable discussion about the signal/noise ratios attainable in Fourier transform infrared (FT-ir) spectroscopy. This involves not only the magnitude of the multiplex and throughput advantages of FT-ir, but also several other features of this technology.
TL;DR: Amorphous thallium-selenium alloys (a-Tl x Se 1− x ) have been studied by Fourier transform infrared spectroscopy within the composition range 0.53 to 0.97 cm −1 and ∼163 cm − 1, reflecting the similarity of tetrahedral coordination within the [(TlSe 2 ) −1 ] n chains.
Abstract: Amorphous thallium-selenium alloys (a-Tl x Se 1− x ) have been studied by Fourier transform infrared spectroscopy within the composition range 0 ⩽ x ⩽ 0.53. Differential scanning calorimetry measurements were used to check the selenium content and the homogeneity of the samples. For the stoichiometric composition a-TlSe there is strong evidence of short-range order similar to that found in the crystalline phase, c-TlSe. The spectra of both amorphous and crystalline TlSe display features associated with bond-bending and bond-stretching modes of distorted tetrahedra at ∼97 cm −1 and ∼163 cm −1 , reflecting the similarity of tetrahedral coordination within the [(TlSe 2 ) −1 ] n chains. At the Se-rich side with x ⩽ 0.24, a superposition of typical infrared bands of a-TlSe and amorphous selenium (a-Se) is observed. The results are discussed in terms of a structural model for a-Tl x Se 1− x .
TL;DR: In a Michelson interferometer as used in a Fourier transform spectrometer, equal amounts of energy are directed to the detector and back towards the source, with a 180° phase shift between them as discussed by the authors.
Abstract: In a Michelson interferometer as used in a Fourier transform spectrometer, equal amounts of energy are directed to the detector and back towards the source, with a 180° phase shift between them
01 Mar 1977
TL;DR: In this paper, an extensive measurement system for atmospheric transmission field experiments is described with emphasis on the recent additions of a high resolution, scanning, Fourier interferometer system and a gas filter correlation spectrometer.
Abstract: : An extensive measurement system for atmospheric transmission field experiments is described with emphasis on the recent additions of a high resolution, scanning, Fourier interferometer system and a gas filter correlation spectrometer. Results obtained from three concurrent experiments used to generate a data base appropriate to high resolution transmission model validation are displayed. Laser extinction data, high resolution, long path atmospheric transmission spectra, and path integrated water vapor measurements are reported and discussed. Plans for future field experiments utilizing these three measurement techniques plus broadband infrared transmissometer and infrared target signature measurement are discussed.
TL;DR: In this paper, a plasma-scanned Michelson interferometer was used for fast FIR multiplex spectroscopy based on a magnetometer, which has sub-millisecond time response and high spectral resolving power.
TL;DR: The principle of Fourier transform spectroscopy and its application in infrared astronomy are briefly reviewed in this paper, where a survey of existing spectrometers and current applications is presented.