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Showing papers on "Fourier transform infrared spectroscopy published in 1976"



Journal ArticleDOI
TL;DR: In this article, an infrared absorbance subtraction technique has been used to isolate bands in the composite spectrum of semicrystalline polymers according to their crystalline or amorphous character.
Abstract: An infrared absorbance subtraction technique has been used to “isolate” bands in the composite spectrum of semicrystalline polymers according to their crystalline or amorphous character. Amorphous and crystalline spectra for annealed, melt-quenched, and solution-cast poly(ethylene terephthalate) have been separated. The spectra of the amorphous component show an increased intensity of bands associated with the trans configuration of oxygen about the CC bond when the polymer is annealed. This increased “trans” band intensity reflects the increased proportion of trans structures as a result of annealing. The amorphous trans bands are shifted approximately 1–3 cm−1 from their positions in the crystalline “trans” spectrum. The frequency shift of these bands can be attributed to the differences in chain interactions that exist in the amorphous phase and the crystalline lattice. We have also found that under identical anealing conditions the amorphous phase of the melt-quenched polymer contains an increased intensity of conformational trans bands compared to the sample cast from solution.

73 citations


Journal ArticleDOI
TL;DR: In this paper, two computational techniques for the deconvolution of photoelectron spectra, both based on Fourier transform theory, are described, and the better method is judged to be that depending on the procedure of "band-limiting" the final result.

65 citations


Journal ArticleDOI
09 Jan 1976-Science
TL;DR: This lab will focus on the chemical structures of certain substances, however IR spectroscopy is used for obtaining an abundance of information such as thermodynamic data, bond length and diffusion data.
Abstract: IR spectroscopy is an important relatively inexpensive and efficient analytical method for characterizing materials. In this lab we will focus on the chemical structures of certain substances, however IR spectroscopy is used for obtaining an abundance of information such as thermodynamic data, bond length and diffusion data. On the other hand IR spectroscopy is limited in the ability to obtain accurate quantitative measurements and the range of inorganic materials that are IR visible. The spectrum that is obtained from IR spectroscopy is due to the vibrational modes of the molecules. Each molecule has its own distinct quantized vibrational energy level. This is often termed its ‘fingerprint’. In FTIR, electromagnetic radiation in the infrared region is directed at the sample. When the frequency of this energy matches the frequency of the vibration of the molecules, radiation is absorbed (or transmitted). Below is an example of an IR spectrum.

63 citations


Journal ArticleDOI
TL;DR: In this paper, dispersive Fourier transform spectrometry (DFTS) is used for measuring the optical constants of liquids. But the use of windowed liquid cells enables amplitude reflection measurements to be carried out and this not only solves the liquid vapour problem, but also permits a very thin layer (10 μm) of absorbing liquid to be used.

62 citations


Journal ArticleDOI
TL;DR: In this paper, a set of peak wavenumbers, Vm = m/2nd (1) where m is the sample refractive index, and d, its thickness, is given for thin film solid samples and ΔT = 4 (n − n 0/n + n 0)2 (3) for samples contained between windows of n 0.
Abstract: Thin samples in spectroscopy often show disturbing "channel spectra" due to interference fringes produced by reflections at the sample surface. These fringes will be characterized by a set of peak wavenumbers, vm as Vm = m/2nd (1) where m = 0, 1, 2, ... ; n is the sample refractive index, and d, its thickness. The intensity of these peaks, ΔT, is given by ΔT = 4 (n − 1/n + 1)2 (2) for thin film solid samples and ΔT = 4 (n − n0/n + n0)2 (3) for samples contained between windows of index n0.

52 citations


Journal ArticleDOI
TL;DR: Fourier transform techniques in spectroscopy have been shown to offer significant improvements over classical dispersive methods in the study of infrared spectral features both in astronomical measurements and in laboratory studies as discussed by the authors.
Abstract: Fourier transform techniques in spectroscopy have been shown to offer significant improvements over classical dispersive methods in the study of infrared spectral features both in astronomical measurements and in laboratory studies. These improvements result from now well known principles including spectral multiplexing, high etendue or throughput, and a significantly improved wave number scale.

46 citations


Proceedings ArticleDOI
TL;DR: In this article, the authors used the Michelson type two beam interferometer to measure the complex refractive index (CFI) and the complex relative permittivity of medium loss as well as high loss volatile liquids over a wide temperature range (−80 °C to 80 °C).
Abstract: Dispersive Fourier transform spectrometry (DFTS) of liquids [1] in the millimetre and sub-millimetre wave region has been extended to include precise measurement of the complex refractive index ň or the complex relative permittivity e of medium loss as well as high loss volatile liquids over a wide temperature range (− 80 °C to 80 °C) by the use of variable thickness windowed cell in one active arm of the Michelson type two beam interferometer. In the past these measurements were restricted to liquids of relatively low vapour pressure because of the necessity to use a free layer of liquid. An excess of liquid vapour absorbs radiation and gives its own characteristic spectrum [2]. The free layer method and subtraction [3,4] and double subtraction [5] procedures enabled investigation of liquids of absorption coefficient a up to 250 Neper/cm. But as the absorption increases it becomes more and more difficult to produce a sufficiently thin plane parallel layer held freely under gravity. However for very absorbing liquids, like water, reflection DFTS [5,6] has been successfully used in which accurate determination of the phase shift and an extremely stable interferometric system are essential.

38 citations


Journal ArticleDOI
01 Jan 1976
TL;DR: The recent introduction of Fourier transform infrared (FTIR) spectrometers that are operable over the entire IR frequency range has revitalized the field of IR spectroscopy as discussed by the authors.
Abstract: The recent introduction of Fourier Transform Infrared (FTIR) spectrometers that are operable over the entire IR frequency range has revitalized the field of IR spectroscopy. IR studies of complex polymeric materials that were impossible, or at least extremely difficult using conventional dispersive spectrometers, are now readily accomplished. In this review of the application of FTIR to the study of polymeric materials, we initially present a brief critical comparison of the FTIR and dispersive spectrometers followed by a discussion of the results that have been published to date.

37 citations


Journal ArticleDOI
TL;DR: In this paper, the thermal autoxidation of cis-1,4-polybutadiene was studied by FTIR at various temperatures, and it was shown that the loss of cis and the formation of trans structures at 25° and 60°C is an oxidative process.
Abstract: The thermal autoxidation of cis-1,4-polybutadiene was studied by FTIR at various temperatures. The spectral information obtained gives more details of the autoxidation than was previously available by dispersive infrared spectroscopy. The primary mechanism involves both cyclic alkoxyperoxides that had been previously suggested by Bevilacqua and Bolland, respectively. We have demonstrated that the loss of cis and the formation of trans structures at 25° and 60°C is an oxidative process.

32 citations


Journal ArticleDOI
TL;DR: In this article, the vibrational spectra of species adsorbed on thin layer chromatography (TLC) plates have been studied by Fourier transform infrared (FT-ir) and Raman spectrometry.
Abstract: Methods of measuring the vibrational spectra of species adsorbed on thin layer chromatography (TLC) plates have been studied by Fourier transform infrared (FT-ir) and Raman spectrometry. Previous measurements of the transmittance spectra of species separated by TLC (with the adsorbent deposited on AgCl plates) showed poor signal/noise ratio at high frequency due to scattering by the adsorbent. Scattering has been minimized in these experiments by treating the TLC plate with Fluorolube, an infrared mulling oil whose refractive index closely matches that of the adsorbent. Spectra of chlorinated hydrocarbon pesticides on silica gel and alumina adsorbents measured in this way show differences which can be correlated with the mechanism of adsorption. FT-ir spectra of compounds on TLC plates can be obtained from microgram quantities of sample but Raman spectrometry is not as sensitive, requiring at least 200 μg of sample. The Raman bands of adsorbed pesticides are weak and considerably broadened with respect to the corresponding bands in the spectra of the pure samples.

Journal ArticleDOI
TL;DR: In this article, a new Fourier spectrometer has been constructed for use in the visible range, where the noise is due to the signal itself; the accuracy of the measurements of the position of the lines, is proportional to line intensity, and is of the order of a few hundreths of mK (1 mK = 10-3 cm-1).
Abstract: A new Fourier spectrometer has been constructed for use in the visible range, where the noise is due to the signal itself. With this instrument it is possible to record in one sweep a spectral range of 10 000 cm-1. The interferograms contain 106 points (corresponding to a resolving power of about 106) and the reproducibility of the measurements of the wavenumbers of recorded lines in emission spectroscopy is 10-7 in relative value; the accuracy of the measurements of the position of the lines, is proportional to line intensity, and is of the order of a few hundreths of mK (1 mK = 10-3 cm-1) for the strongest among them. Finally, the intensity of the weakest measurable line is one thousandth of the intensity of the strongest line of the spectrum. Compared to a conventional grating spectrometer, the Fourier transform spectroscopy has the advantage among others, of maintaining the throughput gain (Jacquinot) constant for all the lines of the spectrum; the multiplex gain (Fellgett) does not disappear entirely; it depends strongly on the intensity of the lines. The work presented here, proves clearly that the extension of Fourier transform spectroscopy to regions where the noise is principally photon-noise, is effectively possible.

Journal ArticleDOI
TL;DR: A Michelson-type Fourier transform spectrometer has been constructed for high resolution work in the far ir and can be used with a tunable band pass filter system for the reduction of sampling points in a specific spectral region.
Abstract: A Michelson-type Fourier transform spectrometer has been constructed for high resolution work in the far ir. The instrument has a theoretical resolution of 0.007 cm−1 and can be used with a tunable band pass filter system for the reduction of sampling points in a specific spectral region. Separations of 0.05 cm−1 in the inversion spectrum of NH3 in the 200-cm−1 spectral region have been observed with about 1000 sampling points and splittings of 0.04 cm−1 in the NO2 spectrum at about 100 cm−1.


Journal ArticleDOI
01 Oct 1976-Icarus
TL;DR: A spectrum of Jupiter between 6000 and 12 000 cm − at high resolution (0.05 cm − ) was recorded with a Michelson interferometer at Palomar Mountain in October 1974 as mentioned in this paper.


Journal ArticleDOI
TL;DR: In this article, the authors show that absorbance subtraction spectra can be obtained with repeatability of 10−3 cm−1 if both spectra are taken with the same or no vignetting.
Abstract: Absorbance subtraction spectra, a common application of Fourier transform infrared (FT-ir) spectrometers, typically requires wavenumber scale repeatabilities of the order of 10−3 cm−1. Such repeatabilities are possible only if both spectra are taken with the same or no vignetting, as the following analysis shows.

Journal ArticleDOI
TL;DR: The analysis of Landau emission from impact ionized n -InSb with the aid of Fourier transform spectroscopy is reported in this paper, where it is shown that the emission spectra are influenced by multiple reflections, interferences and selfabsorption effects.

Journal ArticleDOI
TL;DR: In this paper, a tradeoff is made between the reduction in the transmitted energy, which limits scale expansion, and the increased absorptivity resulting from an equal amount of sample spread over a smaller area.
Abstract: In optimizing the clear radius of a KBr micropellet or liquid microcell measurements in an Fourier transform infrared (FTIR) spectrometer, a tradeoff can be made between the reduction in the transmitted energy, which limits scale expansion, and the increased absorptivity resulting from an equal amount of sample spread over a smaller area.

Journal ArticleDOI
TL;DR: In this paper, the spectrum of neutral phosphorus has been studied in the infrared region 1-4 μm with the Fourier Transform Spectrometer at Laboratoire Aime Cotton, Orsay, using a microwave-excited discharge tube as a light source.
Abstract: The spectrum of neutral phosphorus has been studied in the infrared region 1-4 μm with the Fourier Transform Spectrometer at Laboratoire Aime Cotton, Orsay, using a microwave-excited discharge tube as a light source. Altogether 538 transitions between P I levels have been measured and classified, 130 of which were resolved into hfs doublets. The results made it possible to confirm many new levels, established by transitions in the photographic region below 11 500 A, and give adequate configuration assignments to the terms of the 3s3p4 and nd configurations.

Journal ArticleDOI
TL;DR: In this paper, a 14-parameter lattice dynamical shell model was fitted to phonon dispersion curves measured by Vagelatos et al. The two-phonon density-of-states calculated with these parameters was compared with the absorption spectrum.
Abstract: Far-infrared absorption in cubic ZnS due to single-phonon and two-phonon processes was measured with a high resolution, far-infrared Fourier transform spectrometer. A 14-parameter lattice dynamical shell model was fitted to phonon dispersion curves measured by Vagelatos et al. The two-phonon density-of-states calculated with these parameters was compared with the absorption spectrum. Two-phonon combinations and their locations in the Brillouin zone were identified with features of the absorption spectrum. Critical points were found on or near the zone boundary and not only at high symmetry points as suggested previously.


Journal ArticleDOI
01 Sep 1976
TL;DR: In this paper, a complete system for far infrared studies of magnetic materials at temperatures as low as 1.3 K and magnetic fields up to 7.5 T was described, and the results on FeCl2 and Fe2+ ions in MgO.
Abstract: 2014 The description of a complete system for far infrared studies of magnetic materials at temperatures as low as 1.3 K and magnetic fields up to 7.5 T is given. The good overall performance is demonstrated by the results on FeCl2 and Fe2+ ions in MgO. REVUE DE PHYSIQUE APPLIQUEE ROME 11, SEPTEMBRE 1976, PAGE Classification Physics Abstracts 0.644 8.822

Journal ArticleDOI
26 Mar 1976-Science
TL;DR: The Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy (PCAS) is the largest meeting devoted to chemical instrumentation in the United States, and probably the largest in the world as mentioned in this paper.
Abstract: The Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy is the largest meeting devoted to chemical instrumentation in the United States, and probably the largest in the world. Fr...

Book ChapterDOI
01 Jan 1976
TL;DR: There are a variety of interferometers whose output is the inverse Fourier transformation of the spectrum being investigated as discussed by the authors, such as the one described in Section 2.2.1.
Abstract: There are a variety of interferometers whose output is the inverse Fourier transformation of the spectrum being investigated.

Journal ArticleDOI
TL;DR: In this paper, the amplitude and phase reflection spectra of suitable solids were measured by DFTS at temperatures down to 77 K. Satisfactory measurements can be made in the frequency range from 5 to 500 cm-1 using instruments equipped with either dielectric thin film or wire grid beam splitters.
Abstract: In recent years infrared spectroscopy has been widely used to study soft mode behaviour in ferroelectric crystals, the usual approach being to measure the power reflectivity over a wide spectral range, calculate the phase spectrum using a Kramers-Kronig analysis, and hence compute the dielectric functions. The difficulties of this approach are well known but can only be avoided by measuring the phase spectrum directly by dispersive Fourier transform spectroscopy (DFTS). However, DFTS is not yet widely used because of the difficulty of measuring the phase spectrum as a function of temperature with sufficient accuracy.We have developed techniques for measuring the amplitude and phase reflection spectra of suitable solids by DFTS at temperatures down to 77 K. Satisfactory measurements can be made in the frequency range from 5 to 500 cm-1 using instruments equipped with either dielectric thin film or wire grid beam splitters. The phase spectrum can be determined with an error of less than 1° in the region of ...

Journal ArticleDOI
TL;DR: To maximize the signal obtained in ir emission from nearly transparent or low pressure gases, the thickness of gas observed must be as large as feasible as discussed by the authors. But the extent to which this is possible will ultimately be limited by geometrical optical considerations.
Abstract: To maximize the signal obtained in ir emission from nearly transparent or low pressure gases, the thickness of gas observed must be as large as feasible. The extent to which this is possible will ultimately be limited by geometrical optical considerations.


Book ChapterDOI
01 Jan 1976
TL;DR: In this paper, the 1.59 absolute wavenumbers of the 1-0 band of 12C16O with an uncertainty of ± 2 MHz were given with an error of 2 MHz.
Abstract: 59 absolute wavenumbers of the 1–0 band of 12C16O are given with an uncertainty of ± 2 MHz.

Journal ArticleDOI
TL;DR: In this article, the Hg spectrum was reconstructed using the holographic Fourier transform method, and many higher-order lines, up to the third order, were observed, due to the nonlinear effect of the film transmittance-exposure curve, and their positions agreed extremely well with the calculated ones.
Abstract: The Hg spectrum was reconstructed using the holographic Fourier transform method. Many higher-order lines, up to the third order, were observed. All these lines are due to the non-linear effect of the film transmittance-exposure curve, and their positions agree extremely well with the calculated ones. The reconstructed spectrum was observed under two different experimental conditions: (i) when the 5770/90 AA doublet of the Hg spectrum was resolved, and (ii) when the same doublet was not resolved. The results can be explained by a recent theory. There is qualitative agreement between theory and experiment on relative line intensities for certain higher-order lines. In particular, it is shown that the presence of higher-order lines is harmful to the analysis of an unknown spectrum, and therefore film non-linearity should be avoided if possible.