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Showing papers on "Fourier transform spectroscopy published in 1996"


Journal ArticleDOI
TL;DR: In this article, a novel method for fast and reliable extraction of material parameters in terahertz time-domain spectroscopy was proposed, which could be applied for most materials and requires neither simplifying assumptions nor samples of different thickness for the extraction.
Abstract: This paper introduces a novel method that allows fast and reliable extraction of material parameters in terahertz time-domain spectroscopy. This method could be applied for most materials and requires neither simplifying assumptions nor samples of different thickness for the extraction. The presented extraction procedure operates either on truncated terahertz signals when temporal windowing is possible, or on full ones otherwise. Some experimental examples covering all practical cases are given. In particular, the extraction procedure treats the tedious case of samples for which internal reflections of the terahertz pulse slightly overlap.

821 citations


Journal ArticleDOI
TL;DR: In this paper, the fundamental principles of Fourier transform mass spectrometry (FTMS) are presented, and the motion of ions in a FTMS analyzer can be understood in terms of the magnetic and electric fields present in the analyzer cell.
Abstract: The fundamental principles of Fourier transform mass spectrometry (FTMS) are presented. The motion of ions in a FTMS analyzer can be understood in terms of the magnetic and electric fields present in the FTMS analyzer cell. Ion motion is illustrated with the results of ion trajectory calculations under both collision-free conditions and at high pressure. Dipolar and quadrupolar excitation are described and compared. Practical considerations in obtaining ultra-high-mass resolution and accuracy are discussed. The FTMS experiment is a series of events (ionization excitation, detection) that occur in sequence. Pulse sequences for mass spectrometric and tandem mass spectrometric experiments are presented.

363 citations


Journal ArticleDOI
TL;DR: In this paper, a fiber-optics-based Fourier transform infrared (FOB-FTIR) spectroscopy was used for in situ monitoring of input partial pressures of organometallic precursors.

158 citations


Journal ArticleDOI
TL;DR: In this paper, the authors performed laboratory measurements of NO2 absorption cross-section using a Fourier transform spectrometer at 2 and 16 cm-1 (0.03 and 0.26 nm at 400 nm).
Abstract: New laboratory measurements of NO2 absorption cross-section were performed using a Fourier transform spectrometer at 2 and 16 cm-1 (0.03 and 0.26 nm at 400 nm) in the visible range (380–830 nm) and at room temperature. The use of a Fourier transform spectrometer leads to a very accurate wavenumber scale (0.005 cm-1, 8×10-5 nm at 400 nm). The uncertainty on the new measurements is better than 4%. Absolute and differential cross-sections are compared with published data, giving an agreement ranging from 2 to 5% for the absolute values. The discrepancies in the differential cross-sections can however reach 18%. The influence of the cross-sections on the ground-based measurement of the stratospheric NO2 total amount is also investigated.

120 citations


Journal ArticleDOI
TL;DR: In this paper, the first double quantum two-dimensional Fourier transform electron spin resonance (2D-FT ESR) experiments were reported, where a distance of 21 A was found for a poly-proline peptide, spin labeled at both ends, in agreement with earlier measurements using fluorescence energy transfer.

119 citations


Journal ArticleDOI
TL;DR: In this article, an indium antimonide (InSb) focal-plane array detector and a commercially available step-scan Fourier transform infrared spectrometer (FTIR) were used to generate image contrast in sections of monkey brain tissue and relate these data to specific lipid and protein fractions.
Abstract: We demonstrate a new mid-infrared and near-infrared imaging approach which is ideally suited to microscopic applications. The method employs an indium antimonide (InSb) focal-plane array detector and a commercially available step-scan Fourier transform infrared spectrometer (FTIR). With either a KBr or a CaF2 beamsplitter, images from 1 to 5.5 μm (10,000–1818 cm-1) can be rapidly acquired with the use of all the available pixels on the detector. The spectral resolution for each image is easily varied by changing the number of acquired images during the interferometer scan. We apply this technique to noninvasively generate image contrast in sections of monkey brain tissue and to relate these data to specific lipid and protein fractions. In addition, we describe several computational methods to highlight the spatial distributions of components within a sample.

101 citations


Journal ArticleDOI
TL;DR: In this paper, the structure and bond formation in the SiCN films were discussed in terms of the present results, and the properties of the deposited films were studied by spectroscopic ellipsometry, Fourier transform infrared spectroscopy, X-ray photoelectron, and Auger electron spectrographs.
Abstract: Silicon–carbon–nitrogen alloys have been deposited by electron cyclotron resonance plasma chemical vapor deposition. Nitrogen, methane, and argon diluted silane have been used as precursor gases. The properties of the deposited films were studied by spectroscopic ellipsometry, Fourier transform infrared spectroscopy, X‐ray photoelectron, and Auger electron spectroscopy. The structure and bond formation in the SiCN films is discussed in terms of the present results.

98 citations


Journal ArticleDOI
TL;DR: The development of Fourier transform ion cyclotron resonance (FT-ICR) spectroscopy is traced from its 1973 conception by analogy to Fourier transforms nuclear magnetic resonance ( FT-NMR) to its 1978 demonstration as the technique of choice for examining complex ion chemistry.
Abstract: The development of Fourier transform ion cyclotron resonance (FT-ICR) spectroscopy is traced from its 1973 conception by analogy to Fourier transform nuclear magnetic resonance (FT-NMR) spectroscopy and its 1974 experimental demonstration to its 1978 demonstration as the technique of choice for examining complex ion chemistry. The intellectual connections between conventional NMR and ICR and FT-NMR are described. The theoretical prediction and experimental demonstration of the many advantageous features of FT-ICR are described. Subsequent FT-ICR technique developments and applications are mentioned briefly.

92 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the adsorption of CO on Ir(111) with Fourier transform infrared reflection-absorption spectroscopy, temperature programmed desorption, and low-energy electron diffraction.

88 citations


Journal ArticleDOI
TL;DR: In this paper, a pulsed multiplex cavity ring down (CRD) spectrometer was proposed for the detection of molecular oxygen using the Fourier transform (FT) spectrum.
Abstract: We present a pulsed multiplex absorption spectrometer in which the sensitivity of the cavity ring down absorption detection technique is combined with the multiplex advantage of a Fourier Transform spectrometer. A description of the Fourier transform cavity ring down (CRD) spectrometer—substantiated with first experimental results on the atmospheric band of molecular oxygen—is given. It is shown that as in the case of normal CRD spectroscopy, the measurement is independent of light intensity fluctuations provided the spectral intensity distribution of the light source is known and is constant during the measurement.

88 citations


Journal ArticleDOI
TL;DR: In this paper, the rotational temperature of the excited state is not in equilibrium with the translational temperatures of the neutral particles, and it is shown that the H atom kinetic temperature is higher than the one.
Abstract: We report temperature measurements in a low-pressure hydrogen microwave plasma. Translational temperatures both of H and of (using Doppler broadening), as well as the rotational temperature of , are simultaneously determined. It is first shown that the rotational temperature of the excited state is not in equilibrium with the translational temperatures of the neutral particles. Then, using a high-resolution Fourier transform spectrometer, we show that the H atom kinetic temperature is higher than the one. This result is interpreted in considering the mechanisms of relaxation of the hot H atoms, produced by electron impact dissociation of , in the molecules and on the tube walls.

Journal ArticleDOI
TL;DR: A new scheme of Fourier-transform spectroscopy in the mid and the far infrared is developed, which relies on an interferometer in the visible or the near infrared, providing a sequence of two femtosecond pulses, which in turn generate a sequences of infrared pulses.
Abstract: We have developed a new scheme of Fourier-transform spectroscopy in the mid and the far infrared. The method relies on an interferometer in the visible or the near infrared, providing a sequence of two femtosecond pulses, which in turn generate a sequence of infrared pulses. The geometrical properties of the different diffracted infrared waves are used to isolate the relevant signal. An experimental demonstration is shown in the mid infrared by use of optical rectification of near-infrared 15-fs pulses.

Journal ArticleDOI
TL;DR: In this article, a step-scan Fourier transform infrared spectroscopy (FTIR) method was proposed to study the electronic excited states of transition metal complexes, taking advantage of the unique properties of carbonyl and cyanide stretching vibrations, including high infrared oscillator strength and well established sensitivity of vibrational frequency, intensity, and bandwidth to electronic and molecular structure.
Abstract: Time-resolved, step-scan Fourier transform infrared spectroscopy has been developed as a method of studying electronically excited states of transition metal complexes. The technique takes advantage of the unique properties of carbonyl and cyanide stretching vibrations, including high infrared oscillator strength and well established sensitivity of vibrational frequency, intensity, and bandwidth to electronic and molecular structure. Electronic excitation generally produces significant transient infrared absorption changes which are characteristic of the changes in electronic structure, such as oxidation of the metal. TRIR spectroscopy thus provides new insight on the nature of the excited state transition (e.g. charge transfer vs. ligand centered), the extent of charge transfer, communication between metal centers, and energy and electron transfer processes. The step-scan FTIR approach has significant advantages over conventional time-resolved techniques, including spectral multiplexing, increas...

Journal ArticleDOI
TL;DR: In this article, a high pressure cell for Fourier transform infrared studies of extraction, impregnation, partitioning, and interactions between supercritical fluids and polymers is presented, and two parallel optical paths through the cell permit the measurement of IR spectra of the supercritical fluid and the polymer sample under the same conditions without essential overlapping of the absorption bands studied.
Abstract: A novel high pressure cell for Fourier transform infrared studies of extraction, impregnation, partitioning, and interactions between supercritical fluids and polymers is presented. Two parallel optical paths through the cell permit the measurement of IR spectra of the supercritical fluid and the polymer sample under the same conditions without essential overlapping of the absorption bands studied. This cell has been applied to study the supercritical CO2 drying of poly(methyl methacrylate) using deuterated water to eliminate the overlap of the IR absorption bands of the stretching modes of water with the bands due to combination modes of CO2. The technique for attaining quantitative measurements of the partitioning of the solute between the supercritical fluid and polymer phases is described.

Journal ArticleDOI
TL;DR: A rigorous test of the photometric accuracy of commercial high-resolution Fourier transform spectrometers has been made by measuring line strengths in the pure rotational spectrum of carbon monoxide, showing that systematic errors affected the retrieved line strengths by less than 1%.
Abstract: A rigorous test of the photometric accuracy of commercial high-resolution Fourier transform spectrometers has been made by measuring line strengths in the pure rotational spectrum of carbon monoxide. Measurements have been made with a Bruker IFS 120 HR spectrometer (transitions: J″ = 7 … 23) and a Bomen DA3.002 spectrometer (J″ = 27 … 35). A least-squares fit of individual data sets and the combined data gave permanent electric dipole moments in the range 0.1091–0.1101 D and quadratic Herman–Wallis factors in the range −0.188 to −0.229 × 10−3, in good agreement with literature values within the overall uncertainty. Sources of systematic errors in the Fourier-transform spectrometer and in the algorithms used to reduce the data are discussed in detail. The experimental results show that such errors affected the retrieved line strengths by less than 1%.

Journal ArticleDOI
TL;DR: In this paper, the analytical merit of Fourier transform electrospray ionization ion mobility spectrometry (FT-ESI-IMS) was investigated, and an increase in both signal/noise ratio (S N ) and ion mobility resolving power was observed for the FT mode of operation.

Journal ArticleDOI
TL;DR: In this article, Fourier transform infrared measurements on the spectra of the products of the vaporization of silicon/carbon mixtures trapped in argon at ∼10 K combined with the results from a published ab initio study and from new theoretical calculations carried out in the present work, have resulted in the first observation of a spectrum for the pentagonal Si3C2 cluster.
Abstract: Fourier transform infrared measurements on the spectra of the products of the vaporization of silicon/carbon mixtures trapped in argon at ∼10 K combined with the results from a published ab initio study and from new theoretical calculations carried out in the present work, have resulted in the first observation of a spectrum for the pentagonal Si3C2 cluster. Three vibrational fundamentals have been assigned: the ν2(a1) symmetric ‘‘breathing’’ vibration at 681.1 cm−1, the ν7(b2) Siα–C–C–Siα stretching deformation at 956.7 cm−1, and the ν8(b2) C–Siβ–C antisymmetric stretching vibration at 597.8 cm−1. The observed frequencies, relative intensities, and 13C, 29Si, and 30Si isotopic shifts are in excellent agreement with the theoretical predictions.

Journal ArticleDOI
TL;DR: In this paper, the electronic emission spectra of LaH and LaD have been investigated in the 3 μm-700 nm spectral region using a Fourier transform spectrometer.
Abstract: The electronic emission spectra of LaH and LaD have been investigated in the 3 μm–700 nm spectral region using a Fourier transform spectrometer. The molecules were excited in a lanthanum hollow cathode lamp operated with neon gas and a trace of hydrogen or deuterium. The bands observed in the 1 μm–3 μm region have been assigned into two new electronic transitions; A 1Π–X 1Σ+ and d 3Φ–a 3Δ. The LaH bands with origins at 4533.5593(8) cm−1 and 4430.1916(13) cm−1 have been assigned as the 0‐0 and 1‐1 bands of the A1Π–X 1Σ+ transition. The rotational analysis of these bands provides the following principal molecular constants for the ground X 1Σ+ state, Be=4.080 534(80) cm−1 and αe=0.077 39(10) cm−1 and re=2.031 969(20) A. To higher wave numbers, three subbands of LaH with origins at 5955.8568(16) cm−1, 6238.3768(8) cm−1, and 6306.6757(15) cm−1 have been assigned as the 3Φ2–3Δ1, 3Φ3–3Δ2, and 3Φ4–3Δ3 subbands of the d 3Φ–a 3Δ electronic transition. The rotational analysis of the 0‐0 and 1‐1 bands of the 3Φ2–3Δ1...

Journal ArticleDOI
TL;DR: In this article, the spectral properties of weakly bound hydrogen-argon complexes were studied at high spectral resolution (0.04-0.10 cm−1) using a long path (154 m), low-temperature (77 K) absorption cell and a Fourier transform infrared spectrometer.
Abstract: Spectra of weakly bound hydrogen–argon complexes have been studied at high spectral resolution (0.04–0.10 cm−1) using a long‐path (154 m), low‐temperature (77 K) absorption cell and a Fourier transform infrared spectrometer. The observations cover a wide spectral range from the far‐infrared D2–Ar S0(0) band at 180 cm−1 to the near‐infrared H2–Ar S2(1) band at 8600 cm−1. Compared to earlier studies, the new results have considerably improved resolution and accuracy. They also extend to new regions, namely the first overtone band of H2 and the pure rotational band of H2 and D2, and they include weak transitions involving excitation of the van der Waals stretching motion. These data serve as a basis for determining a greatly improved three‐dimensional intermolecular potential energy surface for the hydrogen–argon system in the following paper.

Journal ArticleDOI
TL;DR: In this paper, the products of vaporization of boron/carbon mixtures around 3000 K were trapped in argon matrices at 10 K and their Fourier transform infrared spectra were measured.
Abstract: The products of vaporization of boron/carbon mixtures around 3000 K were trapped in argon matrices at 10 K and their Fourier transform infrared spectra were measured. Analysis of the spectra combined with the predictions of density functional theory (DFT) calculations have resulted in the assignment of a previously observed vibration at 1194.4 cm−1 to the ν2 fundamental of cyclic BC2, which is effectively symmetric. The assignment is supported by 10B, 11B, and 13C isotopic data and is in good agreement with the theoretical predictions.

Journal ArticleDOI
TL;DR: In this paper, the structural and chemical properties of hydrogenated amorphous silicon carbide (a−Si1−xCx:H) thin films, deposited by plasmaenhanced chemical-vapor deposition, were determined by extended x-ray absorption fine structure (EXAFS), xray-absorption near-edge spectroscopy (XANES), small-angle xray scattering, Fourier transform infrared (FTIR) spectrograms, Auger electron spectrogram, and visible spectrometry.
Abstract: The structural and chemical properties of hydrogenated amorphous silicon carbide (a‐Si1−xCx:H) thin films, deposited by plasma‐enhanced chemical‐vapor deposition, were determined by extended x‐ray absorption fine structure (EXAFS), x‐ray‐absorption near‐edge spectroscopy (XANES), small‐angle x‐ray scattering, Fourier transform infrared (FTIR) spectroscopy, Auger electron spectroscopy, and visible spectrometry. The EXAFS and XANES results show the crucial influence of the ‘‘starving’’ plasma deposition conditions on the structural properties of wide‐gap a‐Si1−xCx:H films and are consistent with the FTIR and optical‐absorption data. The first‐neighbors distance for alloys with smaller carbon content or deposited at higher silane flow are very close to the mean Si–Si distance obtained for a‐Si:H. On the other hand, the EXAFS spectra of films with higher carbon content (x≳50 at. %) and deposited under ‘‘starving’’ plasma regime show Si–C distances similar to crystalline SiC (c‐SiC). The presence of a typical ...

Journal ArticleDOI
TL;DR: In this article, the fundamental bands ν 1, ν 2, ν 3, and ν 4 were analyzed from two mixtures with different isotopic abundances, and a change in the relative intensities of the three fundamental modes was evidenced for unsymmetrical isotopic species.

Journal ArticleDOI
TL;DR: In this article, a linear motion sample transport (TRANSCELL) was attached to the FTS, which increased the area scanned from 2 mm in diameter (stationary cell or STATCELL), to 2 X 50 mm.
Abstract: The objective of this research was to determine whether diffuse reflectance calibrations using a Fourier transform spectrometer (FTS) could be improved by increasing the scanned sample area. A linear motion sample transport (TRANSCELL) was attached to the FTS, which increased the area scanned from 2 mm in diameter (stationary cell or STATCELL) to 2 X 50 mm. Sodium chlorite-treated forages and by-products (N = 174) were scanned in the near-infrared (NIR) and mid-infrared (MIR) with the use of the TRANSCELL and STATCELL. Samples were analyzed for fiber, digestibility, lignin, protein, and lignin nitrobenzene oxidation products (NOPs). Overall, the best results for fiber, lignin, and digestibility were achieved by using MIR spectra and the TRANSCELL. Results in the NIR (FTS) with the use of the TRANSCELL were also improved over those obtained with the STATCELL. While the TRANSCELL was an improvement over the STATCELL for Fourier NIR analysis of NOPs, in the MIR, results for NOPs were about equal for the TRANSCELL and STATCELL. In conclusion, the use of a TRANSCELL can improve calibrations from Fourier transform spectrometers, although the degree of improvement depends on the spectral region and specific calibration under study.

Journal ArticleDOI
TL;DR: In this paper, infrared absorbance cross-sections and integrated band strengths for HFC-32 (difluoromethane, CH 2 F 2 ) vapour have been determined from laboratory measurements at eight temperatures (203, 212, 222, 243, 253, 264, 287, and 297 K) at 0.03 cm −1 instrument resolution, by Fourier transform infrared spectroscopy.
Abstract: Infrared absorbance cross-sections and integrated band strengths for HFC-32 (difluoromethane, CH 2 F 2 ) vapour have been determined from laboratory measurements at eight temperatures (203, 212, 222, 243, 253, 264, 287, and 297 K) for the region 600–1900 cm −1 at 0.03 cm −1 instrument resolution, by Fourier transform infrared spectroscopy. In addition, air-broadened spectra of HFC-32 vapour have been recorded at 203, 251, and 297 K at pressures of 5, 20, and 100 kPa air.


Journal ArticleDOI
TL;DR: The methodology of spectroscopic remote sensing with high-resolution Fourier-transform spectra obtained from low Earth orbit by the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment is discussed and its development, evolution, robustness, and validation are presented.
Abstract: The methodology of spectroscopic remote sensing with high-resolution Fourier-transform spectra obtained from low Earth orbit by the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment is discussed. During the course of the Atmospheric Laboratory for Applications and Science (ATLAS) shuttle missions (1992-1994) a flexible, yet reproducible, retrieval strategy was developed that culminated in the near-real-time processing of telemetry data into vertical profiles of atmospheric composition during the ATLAS-3 mission. The development, evolution, robustness, and validation of the measurements are presented and assessed with a summary comparison of trace-gas observations within the Antarctic polar vortex in November 1994.


Journal ArticleDOI
TL;DR: In this article, an analytical model including the instrumental line shapes and the intensity distribution is proposed to enable simulations of overlapping rovibrational transitions of symmetric top molecules, and the spectroscopic study of the ν6 and ν10 stretching bands of Fe(CO)5 yielded the following parameters (3σ uncertainties in parenthesis): ν0=2038.
Abstract: Rovibrational FTIR spectra of Ni(CO)4 and Fe(CO)5 have been recorded in supersonic argon expansions at resolutions up to 0.004 cm−1. Rotational temperatures as low as 4 K for the ν6 band of Fe(CO)5 and 6 K for the ν5 band of Ni(CO)4 have been determined from the populations of the rotational levels, and an efficient vibrational cooling has been evidenced by the large reduction of hot band absorptions. An analytical model including the instrumental line shapes and the intensity distribution is proposed to enable simulations of overlapping rovibrational transitions of symmetric top molecules. The spectroscopic study of the ν6 and ν10 stretching bands of Fe(CO)5 yielded the following parameters (3σ uncertainties in parenthesis): ν0=2038.106 97(91) cm−1, B6=0.026 797(12) cm−1, and B0=0.026 826(10) cm−1 for the 610 transition, ν0=2015.5513(12) cm−1, ΔA10=−0.000 086(5) cm−1, B10=0.026 786(4) cm−1, and ξ10=−0.049(3) for the 1010 transition based on the literature value of A0.

Journal ArticleDOI
TL;DR: In this article, the infrared vibration-rotation bands of ND in the X3Σ−state were recorded using a Fourier transform spectrometer using a microwave discharge of a mixture of N2and D2in the presence of He.

Journal ArticleDOI
TL;DR: In this paper, the FT-IR spectra and Raman spectra of (CH 3 ) 4 NSbCl 6 (TMASbCl6), (C 2 H 5 ) 4 NNBS 6 (TEASbCL 6 ), and (CH 2 SbCl 4 (DMASbCCl 6 ) are investigated at 295 K. The vibrational data suggest that the distortion of the octahedral symmetry of SbC 6 − increases in the order TMASbcl 6 6 66 6.