Showing papers on "Fourier transform spectroscopy published in 1990"
TL;DR: In this article, Fourier transform infrared absorption spectroscopy has been used to characterize the structure of porous silica gel films, both deposited on c-Si substrates and free standing.
Abstract: Fourier transform infrared absorption spectroscopy has been utilized to characterize the structure of porous silica gel films, both deposited on c‐Si substrates and free standing. The films were either dried at room temperature or subjected to partial densification at 400–450 °C. The spectra of the gel films are compared to those of thermal SiO2 grown on c‐Si and to Kramers–Kronig analysis of the reflection spectra of bulk SiO2 gels and v‐SiO2. The gel films show small frequency shifts compared to the latter spectra and they also exhibit new bands due to the presence of OH groups, although very little molecular water or residual organic species were found. The results are interpreted in terms of the gel structure. Compared to the thermal oxide, the sharp peak near 1070 cm−1 is narrower for the gels and the spread in intertetrahedral angles is estimated at 24° and 27° for room temperature dried and partially densified gels, respectively, compared to 33° for the thermal oxide. This is in agreement with a st...
410 citations
TL;DR: In this paper, the first spectroscopic evidence that bisulfate anion adsorption is associated with the anomalous peaks seen in the cyclic voltammetry of Pt(111) in sulfuric acid was presented.
176 citations
TL;DR: Fourier transform infrared (FTIR) spectroscopic studies are carried out on different, potentiometric well defined oxidation states of polyaniline in aqueous acidic and organic electrolytes.
Abstract: Fourier transform infrared (FTIR) spectroscopic studies are carried out on different, potentiometric well defined oxidation states of polyaniline in aqueous acidic and organic electrolytes. During the oxidation process ring structures transform from benzenoid into quinoid states. The fully reduced state of polyaniline shows differences in the anion contents in acidic and organic electrolytes. The 400 mV vs saturated calomel electrode (SCE) oxidized state has the maximum number of the intercalated anions in aqueous acidic media in accordance with supporting potentiometric titration experiments. This conducting form of polyaniline shows similar FTIR spectra in organic as well as in acidic media. For the oxidized state at 800 mV vs SCE, a deintercalation of anions in aqueous acidic, or further intercalation in organic electrolyte is observed. Beyond 800 mV vs SCE, polyaniline shows degradation processes in aqueous acidic media which are found to proceed via formation of benzoquinone‐like structures and finally result in a complete dissolution of the polymer.
164 citations
TL;DR: In this article, the authors present hardware and software details of the pulsed molecular beam microwave Fourier transform (MB•MWFT) spectrometer used in the Kiel microwave group.
Abstract: We present hardware and software details of the pulsed molecular beam microwave Fourier transform (MB‐MWFT) spectrometer used in the Kiel microwave group. We emphasize an automatic scanning facility which greatly increases the efficiency of MB‐MWFT spectroscopy for the measurement of unassigned spectra.
137 citations
TL;DR: In this article, Fourier transform spectroscopy was used to measure the absolute absorption cross sections for formaldehyde (CH{sub 2}O) as a function of temperature (223-293 K) and formaldehyde concentration in nitrogen at 500 Torr.
Abstract: The near-ultraviolet (300-360 nm, 33,300-27,800 cm{sup {minus}1}) absolute absorption cross sections for formaldehyde (CH{sub 2}O) have been measured as a function of temperature (223-293 K), and formaldehyde concentration in nitrogen at 500 Torr. Fourier transform spectroscopy was performed using an instrumental resolution sufficiently high (1.00 cm{sup {minus}1} or approximately 0.011 nm at 330 nm) to ensure the cross sections which are used in calculated atmospheric photolysis rates are free of artifacts due to overlap (or lack thereof) in the spectral structure of the solar flux or in the structure of the formaldehyde absorption spectrum. Comparisons with previous measurements are made and recommendations presented for use in atmospheric photolysis rate calculations.
128 citations
TL;DR: In this paper, the relative intensities of 88 pairs of rovibrational transitions of OH(X2Pi) distributed over 16 vibrational bands were measured using FTIR emission/absorption spectroscopy.
Abstract: FTIR emission/absorption spectroscopy is used to measure the relative intensities of 88 pairs of rovibrational transitions of OH(X2Pi) distributed over 16 vibrational bands. The experimental technique used to obtain the Einstein A ratios is discussed. The dipole moment function which follows from the intensity ratios along with Einstein A coefficients calculated from mu(r) is presented.
119 citations
TL;DR: The vibrational spectra of tricarbon hydride radicals formed by trapping the products of the vacuum ultraviolet photolysis of methylacetylene and various deuterated isotopomers in argon at 10 K have been investigated by Fourier transform spectroscopy in the range 200-3400 cm−1.
Abstract: The vibrational spectra of tricarbon hydride radicals formed by trapping the products of the vacuum ultraviolet photolysis of methylacetylene and various deuterated isotopomers in argon at 10 K have been investigated by Fourier transform spectroscopy in the range 200–3400 cm−1. Supplementary studies have examined the photolysis products of allene as well as C3H6 and C3D6, cyclopropane. The results reveal new information on the vibrations of C3H; five C3H2 isomers, cyclopropenylidene, vinylidenecarbene, triplet propargylene, trans‐ and cis‐propenediylidene; two C3H3 isomers, propargyl and cyclopropenyl; and C3H5, allyl.
91 citations
65 citations
TL;DR: In this article, polybutadiene (PBD) was applied to nonporous silica of mean particle diameter 1.7 μm (Monospher) for separation of peptides and polypeptides in less than 1 min.
64 citations
TL;DR: In this article, weakly bound complexes of molecular hydrogen have been studied using an infrared Fourier transform spectrometer and a long absorption path (112 m) through equilibrium gas mixtures at temperatures ∼20 K.
Abstract: Weakly bound complexes of molecular hydrogen have been studied using an infrared Fourier transform spectrometer and a long absorption path (112 m) through equilibrium gas mixtures at temperatures ∼20 K Spectra of the dimers (H2)2, (HD)2, and (D2)2 were recorded, along with those of the mixed species H2–D2 and HD–D2 They lie in the 2900–8700 cm−1 (115–335 μm) spectral region corresponding to the monomer fundamental and first overtone bands Since the rotation and vibration of the monomers remain largely unperturbed in a dimer, each dimer band is centered around a monomer rotation–vibration transition The structure within these bands is associated with motions of the dimer as a whole, and particularly its end‐over‐end rotation, denoted by l The spectra are quite detailed and well resolved, especially for the heavier isotopes HD–D2, and (D2)2, and in many cases, their rotational structure can be fully assigned Although a detailed analysis is beyond the scope of the present paper, it should ultimately
57 citations
TL;DR: In this article, a Fourier transform study of the vibrational spectrum of SiC2 produced by vaporizing mixtures of silicon and carbon 12 or carbon 13 at 2900 K and quenching the products in argon at 10 K, has enabled the identification for the first time of the ν‘3(b2) vibrational mode, which the results of an earlier matrix study had suggested should lie in the far infrared.
Abstract: A Fourier transform study of the vibrational spectrum of SiC2 produced by vaporizing mixtures of silicon and carbon‐12 or carbon‐13 at 2900 K and quenching the products in argon at 10 K, has enabled the identification for the first time of the ν‘3(b2) vibrational mode, which the results of an earlier matrix study had suggested should lie in the far infrared. The assignment of a frequency observed at 160.4 cm−1 to the ν″3 mode is confirmed by isotopic data and supported by the predictions of ab initio calculations. Optimized force constants have been derived using the frequencies of the newly assigned mode, the previously reported, ν‘1(a1)=1741.3 and ν″2(a1)=824.3 cm−1 vibrations, and their values on single and double carbon‐13 substitution. Two models, cyclic and T‐shaped, are discussed for the molecule, which is of C2V symmetry.
TL;DR: In+/Duroquinone− in ethanol was studied by detecting the dispersive component in the Fourier transformed free induction decays of the fully separated radical anions as mentioned in this paper, which originate from the exchange coupling J of the radical pair trapped by an attractive temperature dependent Coulomb interaction U(rc,T) at an equilibrium distance rc.
Abstract: Utilizing the high time and phase resolution of Fourier transform electron paramagnetic resonance, the buildup and decay kinetics of the transient radical pair Zn tetraphenylporphyrin+/Duroquinone− in ethanol could be studied by detecting the dispersive component in the Fourier transformed free induction decays of the fully separated radical anions. The dispersive line components originate from the exchange coupling J of the radical pair in its metastable state trapped by an attractive temperature dependent Coulomb interaction U(rc,T) at an equilibrium distance rc. The decay rate constant kd into free ions was studied over the temperature range of 225–298 K and varied from kd=3.2×106 to 10×106 s−1. This change in kd could be fully rationalized in terms of the temperature dependence of the solvent dielectric constant (leading to a variation of the cage potential from 0.07 to 0.12 eV) and the diffusion constant. The buildup rate constants were consistent with the assumption of a diffusion‐controlled electro...
TL;DR: In this article, Fourier transform Raman spectroscopy has been carried out remote from the instrumentation using fibre-optic probes, and the quality of the data is good; the measured signalto-noise ratios from spectra obtained using a conventional sampling arrangement are better only by a factor of ca. 5.
Abstract: Fourier transform Raman spectroscopy has been carried out remote from the instrumentation using fibre-optic probes. The quality of the data is good; the measured signal-to-noise ratios from spectra obtained using a conventional sampling arrangement are better only by a factor of ca. 5. The choice of fibre-optic material and grade is crucial to the success of this work. Two different fibres have been tested and compared. Technical improvements are discussed.
TL;DR: The present method appears to offer the best available determination of the relative abundances of ions of different mass-to-charge ratio in FT/ICR mass spectrometry.
Abstract: The area under a correctly phased absorption-mode spectral peak is a direct measure of the number of oscillators (ions, spins, molecules) in Fourier transform spectrometry (ion cyclotron resonance, magnetic resonance, interferometry absorbance). However, phase correction can prove difficult when (as in broad-band Fourier transform ion cyclotron resonance (FT/ICR] detection is considerably time-delayed after excitation. In the absence of noise, Huang, Rempel, and Gross showed that a "complex area" method yields the correct absorption-mode peak area, for an unphased noiseless spectrum. In this paper, we show that the number of oscillators may also be obtained from a least-squares fit to a magnitude-mode (i.e., phase-independent) spectrum. In the presence of noise and in the absence of peak overlap, the magnitude-mode method offers precision superior to that based on magnitude-mode peak height, "complex area", or even direct digital integration of a correctly phased absorption-mode peak, as demonstrated by both theoretical derivation and experimental FT/ICR results. The present method thus appears to offer the best available determination of the relative abundances of ions of different mass-to-charge ratio in FT/ICR mass spectrometry.
TL;DR: In this article, the intensity enhancement of infrared spectra with Ag island films in surface electromagnetic wave spectroscopy (SEWS), which is commonly associated with the ATR method, was observed with the use of an ordinary transmission configuration.
Abstract: The intensity enhancement of infrared spectra with Ag island films in surface electromagnetic wave spectroscopy (SEWS), which is commonly associated with the ATR method, was observed with the use of an ordinary transmission configuration. We refer to this as "transmission SEWS" or "T-SEWS." With 10 nm Ag, the magnitude of enhancement factor was about 200 for the NO2 symmetric stretching band at 1350 cm−1 with p-nitrobenzoic acid. In order to estimate its effectiveness as a qualitative analytical method, T-SEWS spectra were compared with normal transmission spectra with the use of several samples. The results showed that T-SEWS is useful in detecting and identifying nanogram amounts of substances which do not have reactive functional groups—e.g., triphenyl phosphate (TPP) or polydimethylsiloxane (PDMS), which do not have -COOH, -SO3H, -C=S, etc. A usable spectrum was observed from as little as 25 ng/cm2 of TPP with the use of a standard triglycine sulfate detector without a beam condenser. Combined with microspectroscopy, T-SEWS shows promise for picogram order analysis and chromatographic applications.
TL;DR: In this paper, the A 2 Δ −X 2 Π electronic transition of the CCN free radical was observed in emission with a high-resolution Fourier transform spectrometer.
Abstract: The A 2Δ–X 2Π electronic transition of the CCN free radical was observed in emission with a high‐resolution Fourier transform spectrometer. The CCN was jet‐cooled in a corona‐excited supersonic jet expansion of diazoacetonitrile (HC(N2)CN) in helium. From the 000–000, 000–001, 000–002, and 000–100 vibronic bands spectroscopic constants were derived including the ground‐state vibrational frequencies, ν3=1050.7636(6), 2ν3=2094.8157(18), and ν1=1923.2547(69) cm−1.
TL;DR: Dispersive Fourier transform spectroscopy (DFTS) is a technique for determining the optical constants of solids, liquids and gases from direct measurements of both the amplitude and phase of either their reyection or transmission coeficients.
Abstract: Dispersive Fourier transform spectroscopy (DFTS) is a technique for determining the optical constants of solids, liquids and gases from direct measurements of both the amplitude and phase of either their reyection or transmission coeficients. Measurements are usually made at normal incidence with the specimen in one arm of a Michelson interferometer. The technique has been widely used for measurements in the far-infrared region of the spectrum, where the phase measurement is comparatively straightforward. Recent developments have established the feasibility of extending the spectral range to the visible and ultraviolet. In this article the principles of DFTS are briefly reviewed, and a selection of results presented to illustrate the scope and potential of the technique.
TL;DR: In this article, the gas phase emission spectrum of BC was recorded using a high resolution Fourier transform spectrometer and a set of spectroscopic constants were derived for the 0-0, 1-1, 2-2, 3-3 vibrational bands.
Abstract: The gas‐phase emission spectrum of BC was recorded using a high resolution Fourier transform spectrometer. The BC radical was produced by sputtering in a composite‐wall hollow cathode discharge lamp. The Δv=0 vibrational sequence of the B 4Σ−– X 4Σ− transition near 5590 A was rotationally analyzed. A set of spectroscopic constants were derived for the 0–0, 1–1, 2–2, and 3–3 vibrational bands, including re =1.491 16(34) A for the X 4Σ− state and re =1.460 23(29) A for the B 4Σ− state.
TL;DR: In this paper, the ν 1 ν 3 interacting bands of natural silane have been studied by Fourier transform spectroscopy and stimulated Raman Spectroscopy, respectively, in the regions 2040−2320 and 2180−2187 cm−1.
TL;DR: In this paper, the vibration-rotation emission spectrum of the high temperature molecule SiS was recorded with a Fourier transform spectrometer and a high resolution emission spectrum at 13 μ (750 cm−1) was observed.
Abstract: The vibration–rotation emission spectrum of the high temperature molecule SiS was recorded with a Fourier transform spectrometer. The observation of a high resolution emission spectrum at 13 μ (750 cm−1) is unusual but we believe this technique is generally applicable to high temperature species. Seven bands (1–0 through 7–6) of the main isotopic form, 28Si32S, were observed along with three bands (1–0, 2–1, and 3–2) for each of the minor species, 29Si32S, 30Si32S, and 28Si34S. Mass‐reduced Dunham parameters, including Watson’s correction due to the breakdown of the Born–Oppenheimer approximation, were derived from the data.
TL;DR: In this article, two-dimensional correlation techniques in the field of pulsed microwave Fourier transform spectroscopy are presented, where five different pulse sequences were used to demonstrate connections between rotational transitions with well separated or with closely spaced frequencies.
Abstract: New two‐dimensional correlation techniques in the field of pulsed microwave Fourier transform spectroscopy are presented. Five different pulse sequences were used to demonstrate connections between rotational transitions with well separated or with closely spaced frequencies. The introduction of two‐ and four‐step phase cycles to select the desired coherence transfer pathways simplified the two‐dimensional spectra considerably. Experiments were performed on methyl formate, norbornadiene, 1‐chloro‐1‐fluoroethene, and vinyl cyanide. A theoretical treatment is given in terms of the density matrix formalism. The relationship between our experiments and similar nuclear magnetic resonance (NMR) techniques is also discussed.
TL;DR: In this paper, Fourier transform spectroscopy was used to measure the absolute absorption cross sections for formaldehyde (CH{sub 2}O) as a function of temperature (223-293 K) and formaldehyde concentration in nitrogen at 500 Torr.
Abstract: The near-ultraviolet (300-360 nm, 33,300-27,800 cm{sup {minus}1}) absolute absorption cross sections for formaldehyde (CH{sub 2}O) have been measured as a function of temperature (223-293 K), and formaldehyde concentration in nitrogen at 500 Torr. Fourier transform spectroscopy was performed using an instrumental resolution sufficiently high (1.00 cm{sup {minus}1} or approximately 0.011 nm at 330 nm) to ensure the cross sections which are used in calculated atmospheric photolysis rates are free of artifacts due to overlap (or lack thereof) in the spectral structure of the solar flux or in the structure of the formaldehyde absorption spectrum. Comparisons with previous measurements are made and recommendations presented for use in atmospheric photolysis rate calculations.
TL;DR: In this paper, the authors examined the thermal decomposition of formic acid adsorbed on a Pd(100) surface using thermal desorption spectroscopy (TDS) and Fourier transform reflection-absorption infrared spectroscopic (FT•RAIRS) techniques.
Abstract: We have examined the thermal decomposition of formic acid (HCOOH) adsorbed on a Pd(100) surface using thermal desorption spectroscopy (TDS) and Fourier transform reflection‐absorption infrared spectroscopy (FT‐RAIRS). The first layer of adsorbed HCOOH starts to decompose at 170 K. The main decomposition products are carbon monoxide, carbon dioxide, and hydrogen. Carbon dioxide desorbs upon formation between 170 and 220 K. We have no experimental evidence for a decomposition intermediate containing more than two atoms.
TL;DR: In this paper, Fourier transform infrared (FTIR) and x-ray photoelectron spectroscopy (XPS) were used to characterize spin-on-glass (SOG) compositional changes for different anneal temperatures.
Abstract: Spin‐on‐glass (SOG) has been characterized using process control techniques that provide in‐line monitoring capability. Film composition changes have been observed for different anneal temperatures (300°–1000°C) and ambients (oxygen and nitrogen). Fourier transform infrared (FTIR) spectroscopy and x‐ray photoelectron spectroscopy (XPS) show a reduction in organic content in the film after annealing at temperatures above 500°C. Area integration under the silicon dioxide peak in the FTIR spectrum indicates compositional changes begin at a critical temperature identified as approximately 500°C. Both FTIR and XPS data show further densification of SOG takes place at higher temperature anneals (700°– 1000°C). Refractive index and film stress measurement data correlate well with FTIR and XPS results.
TL;DR: In situ Fourier transform infrared absorption techniques are employed to characterize the gas-phase plasma species and etch products present in halocarbon containing plasmas which produce particles.
Abstract: In situ Fourier transform infrared absorption techniques are employed to characterize the gas‐phase plasma species and etch products present in halocarbon containing plasmas which produce particles. A correlation is demonstrated between the distribution of these species and the extent of particle formation as measured by laser light scattering. The effects of the presence of silicon and the addition of oxygen on both the plasma species distribution and the degree of light scattering are also characterized. Additionally, x‐ray photoelectron spectroscopy (XPS) and infrared (IR) microscopic techniques are employed to determine the chemical composition of the particulate material which is found on the silicon wafer after etching.
Book•
29 Aug 1990
TL;DR: X-ray-induced photoelectron and auger spectroscopy luminescence studies fourier transform infrared and raman Spectroscopy mossbauer spectroscope nuclear magnetic resonance spectroscopic scanning electron microscopy electron spin resonance spectro-electron micro-analysis secondary ion mass spectrometry auger electron spectroelectron appendices.
Abstract: X-ray-induced photoelectron and auger spectroscopy luminescence studies fourier transform infrared and raman spectroscopy mossbauer spectroscopy nuclear magnetic resonance spectroscopy scanning electron microscopy electron spin resonance spectroscopy electron probe micro-analysis secondary ion mass spectrometry auger electron spectroscopy appendices.
TL;DR: In this article, a comparison of the relative optical throughput (etendue) merits of near-infrared Fourier transform (FT) and conventional dispersive Raman spectrometers is presented.
Abstract: A comparison of the relative optical throughput (etendue) merits of near-infrared Fourier transform (FT) and conventional dispersive Raman spectrometers is presented. Design details of an FT Raman system are described and some examples are given to illustrate the performance of the system.