Showing papers on "Fourier transform spectroscopy published in 1986"
TL;DR: This chapter describes the basic principles, techniques, and applications of resolution-enhanced Fourier transform infrared spectroscopy, which provides several advantages over conventional dispersive techniques: higher resolution, sensitivity, signal-to-noise ratio (S/N), and frequency accuracy.
Abstract: Publisher Summary This chapter describes the basic principles, techniques, and applications of resolution-enhanced Fourier transform infrared spectroscopy. Infrared spectroscopy constitutes one of the oldest methods for studying the secondary structure of polypeptides and proteins. Polypeptides and proteins exhibit a total of nine characteristic absorption bands in the infrared region. These are usually termed the amide A, B, and amide I-VII bands. The amide I (∼1630-1690 cm -1 ) band is the most useful for protein structure studies by infrared spectroscopy. The use of Fourier transform infrared spectroscopy (FTIR) has led to major improvements in this regard. In principle, FTIR provides several advantages over conventional dispersive techniques: higher (1) resolution, (2) sensitivity, (3) signal-to-noise ratio (S/N), and (4) frequency accuracy. Any one of the first three advantages can be emphasized at the expense of the other two. For protein structure studies, high sensitivity makes it possible to acquire usable infrared spectra of aqueous solutions; such spectra are always notoriously difficult to obtain.
698 citations
TL;DR: In this article, the feasibility of Fourier transform Raman spectroscopy has been investigated and a single instrument for both spectroscopies both convenient and cost-effective has been proposed.
Abstract: There has long been a widespread interest in the feasibility of Fourier transform Raman spectroscopy. The well-deserved reputation of FT-IR has generated hopes for similar benefits in Raman spectroscopy, and the complementarity of IR and Raman spectroscopy has made the use of a single instrument for both spectroscopies both convenient and cost-effective.
351 citations
TL;DR: In this paper, the A3Π-X3Σ− transition of NH has been observed using a high-resolution Fourier transform spectrometer and the first three vibrational levels in each state were observed and the vibrational, fine structure, and rotational constants obtained.
191 citations
TL;DR: Extension de la gamme dynamique par ejection selective des ions les plus abondants suivie par excitation normale and detection des ions restants.
Abstract: Extension de la gamme dynamique par ejection selective des ions les plus abondants suivie par excitation normale et detection des ions restants
145 citations
TL;DR: In this article, Fourier transform-infrared reflection absorption spectroscopy (FT-IRAS) was used in a detailed study of the N-N stretching band of N2 weakly chemisorbed on the Ni (110) surface.
Abstract: A newly constructed apparatus for Fourier transform‐infrared reflection absorption spectroscopy (FT‐IRAS) studies has been used in a detailed study of the N–N stretching band of N2 weakly chemisorbed on the Ni (110) surface. The high resolution and the high signal‐to‐noise ratios of the spectra allow observation of subtle changes of the band shape which accompany changes in the overlayer structure. The results are discussed with respect to a detailed two‐dimensional phase diagram recently proposed for the N2/Ni (110) system. The IR data clearly reveal that for low coverages nonequilibrium adsorption occurs at 81 K, while equilibrium is attained at 125 K in agreement with the phase diagram. The present results indicate that the incommensurate overlayer structure which forms at the highest coverages is characterized by an intense sharp IR band at 2194 cm−1, a weak shoulder at 2204 cm−1, and a still weaker satellite peak at 2220 cm−1. The IR results for the incommensurate N2 overlayer are compared with model...
95 citations
TL;DR: Polarized, low-temperature Fourier transform infrared (FTIR) difference spectroscopy has been used to investigate the structure of bacteriorhodopsin as it undergoes phototransitions from the light-adapted state, bR570, to the K630 and M412 intermediates.
Abstract: Polarized, low-temperature Fourier transform infrared (FTIR) difference spectroscopy has been used to investigate the structure of bacteriorhodopsin (bR) as it undergoes phototransitions from the light-adapted state, bR570, to the K630 and M412 intermediates. The orientations of specific retinal chromophore and protein groups relative to the membrane plane were calculated from the linear dichroism of the infrared bands, which correspond to the vibrational modes of those groups. The linear dichroism of the chromophore C=C and C-C stretching modes indicates that the long axis of the polyene chain is oriented at 20-25 degrees from the membrane plane at 250 K and that it orients more in-plane when the temperature is reduced to 81 K. The polyene plane is found to be approximately perpendicular to the membrane plane from the linear dichroism calculations of the HOOP (hydrogen out-of-plane) wags. The orientation of the transition dipole moments of chromophore vibrations in the K630 and M412 intermediates has been probed, and the dipole moment direction of the C=O bond of an aspartic acid that is protonated in the bR570----M412 transition has been measured.
80 citations
TL;DR: In this article, the use of optical fibers in an attenuated total reflectance type cell with an FTIR spectrometer was demonstrated for the first time, and the spectra of acetone in water and of glycine in water were acquired with the cell.
Abstract: Silver halide (AgCl:AgBr) fibers were used as the light conductor for total internal reflection measurements in a Fourier transform infrared (FTIR) spectrometer, to obtain spectra of aqueous solutions. The use of optical fibers in an attenuated total reflectance type cell with an FTIR spectrometer was demonstrated for the first time. Spectra of acetone in water and of glycine in water were acquired with the cell.
73 citations
TL;DR: The resolution, sensitivity, calibration accuracy, and spectral coverage achieved in these spectra demonstrate the viability of the FTS for Raman spectroscopy.
Abstract: Fourier transform spectrometry (FTS) is presently used to record the spontaneous incoherent laser Raman spectra of gases. The high resolution, sensitivity, calibration accuracy and spectral coverage achieved demonstrate the viability of FTS for Raman spectroscopy. Attention is given to the coefficients obtained by fitting measurements obtained from the spectrum of D2, containing both v = 0-0 and 1-0 transitions, to the Dunham (1932) expansion of the vibration-rotation energy levels.
64 citations
TL;DR: The current status of reflection-absorption infrared spectroscopy (RAIRS) is reviewed with examples illustrating its application to studies of structural chemical transformations at surfaces in this article, and the prospects for the future are briefly discussed including the use of synchrotron and laser i.r. sources.
59 citations
TL;DR: The experimental conditions for the microwave Fourier transform spectroscopy are given in this paper, where a typical set up of a spectrometer is presented and discussed, as well as possible extensions to the set up.
Abstract: After an introduction to the interaction of a microwave field and an ensemble of dipolar molecules the experimental conditions for the microwave Fourier transform spectroscopy are given. Specifications are derived for a spectrometer. A typical set up of a spectrometer is presented and discussed. The application to rotational spectroscopy of stable molecules is demonstrated by some examples. Possibilities for extension are mentioned.
54 citations
TL;DR: In this paper, the high-resolution Fourier transform emission spectrum of the c1Π-a1Δ transition of NH was recorded and analyzed, and the line positions and molecular constants were determined from the 1 −0, 0 −0 and 0 −1 vibrational bands.
Abstract: The high-resolution Fourier-transform emission spectrum of the c1Π–a1Δ transition of NH was recorded and analyzed. Improved line positions and molecular constants were determined from the 1–0, 0–0, and 0–1 vibrational bands. In addition to the rotational constants, lambda-doubling parameters for both the c1Π and a1Δ states were extracted from the line positions.
TL;DR: In this article, two prototype experiments on a fast motional nitroxide spectrum are described, based on detection of the Han echo and may be used for discriminating the homogeneous broadening of an inhomogeneous spectrum (and/or the echo envelope modulation).
Abstract: New Fourier transform ESR techniques, which permit rapid data acquisition of ESR spectra, now allow one to perform a variety of two‐dimensional ESR experiments. Two prototype experiments on a fast motional nitroxide spectrum are described. The first is based upon detection of the Han echo and may be used for discriminating the homogeneous broadening of an inhomogeneous spectrum (and/or the echo envelope modulation). The second is based upon detection of the FID after the three‐pulse Jeener–Ernst sequence, and it leads to cross peaks due to Heisenberg spin exhange among the hyperfine lines.
TL;DR: In this paper, the authors describe a new design for a mirage cell which is much more compact than the previously described setup and whose sensitivity has been improved by an order of magnitude.
Abstract: We describe a new design for a mirage cell which is much more compact than the previously described setup and whose sensitivity has been improved by an order of magnitude. This cell has been successfully coupled to Fourier transform infrared spectrometers, visible spectrometers, and a thermal wave imaging setup.
TL;DR: In this paper, the infrared spectrum of the ν6 asymmetric deformation band of hydrogen peroxide (H2O2) was studied in the region 1100-1350 cm−1 using the two techniques of Fourier transform spectroscopy at 0.02cm−1 resolution and tunable diode laser spectroscopic at Doppler-limited resolution.
TL;DR: A new method for removing the most important distortions from Fourier transform spectra recorded with nonlinear detectors is reported and illustrated with practical examples.
Abstract: A new method for removing the most important distortions from Fourier transform spectra recorded with nonlinear detectors is reported and illustrated with practical examples. The removal of these distortions is obtained with a two-output interferometer configuration. This essentially works because the resulting interferogram is made up of the difference between the signals of the two detectors and because these signals have the same amplitude and opposite phases. The proposed method leaves the detectors unchanged and makes use of their distorted signals. The correction is not restricted to the nonlinear effects of the only detectors but also of the entire electronic system amplifying each detector signal. It easily applies to absorption, emission, low and high resolution spectra, as well as spectra of short and long lifetime phenomena. The benefit of the method is not restricted to Fourier transform spectroscopy. It is even not restricted to techniques making use of detectors. Its advantages are available for any data treatment where the important information is made up of the difference between nonlinear functions (or signals) having similar amplitudes and opposite phases, whatever the number of pairs of such distorted functions (or signals) may be.
TL;DR: In this paper, the emission spectrum of a plasma of silane flowing through a multipass reactor and excited by a radio frequency discharge has been recorded with a high information Fourier transform spectrometer.
Abstract: The emission spectrum of a plasma of silane flowing through a multipass reactor and excited by a radio frequency discharge has been recorded with a high information Fourier transform spectrometer. 192 rovibrational transitions of the 28SiH radical, between 1800 and 2150 cm−1, have been measured in the electronic ground state. These transitions are related to the fundamental band 1–0 and the two hot bands 2–1 and 3–2. A least squares procedure have led to the determination of a unique set of 25 accurate molecular constants for the vibrational levels v=0, 1, 2, 3 of the X 2Π state. The standard deviation on the calculated frequencies is 7×10−4 cm−1.
TL;DR: In this article, dispersive Fourier transform spectroscopy of the amplitude and phase of the reflectivity of GaAs/Al x Ga 1-x As MQW and superlattice specimens in the spectral region 75-500 cm -1 are presented.
TL;DR: In this paper, the fundamental and first overtone bands of the FO radical were measured in the infrared using a high-resolution Fourier transform spectrometer coupled to a long-path-length flow tube absorption cell.
TL;DR: In this article, an electrical trap potential is applied to two plates perpendicular to the magnetic field to keep ions from traveling along the helical path shown in Fig. 1 and being lost from the observing region.
Abstract: Principles Fourier transform ion cyclotron resonance (FTICR)lm4 mass spectrometry (MS) is based on the classical motion of ions under the influence of electric and magnetic fields. The magnetic force i? = q (7 X t) acting on a particle of mass m, charge q, and initial velocity ZJ in a field with magnetic induction B causes it to follow a helical path (Fig. 1). The projection of this path onto a plane perpendicular to the magnetic field is a circle of radius r = m v,l(q B), where 2: is the velocity component perpendicular to the magnetic field. The frequency of this circular (or cyclotron) motion is given by Y, = (1/2n)q B/m, so that each ion of a given massto-charge ratio has a characteristic cyclotron frequency. Thus determination of an ion’s cyclotron frequency in a magnetic field of known strength leads directly to knowledge of its mass-to-charge ratio. To keep ions from travelling along the helical path shown in Fig. 1 and being lost from the observing region, an electrical trapping potential is applied to two plates perpendicular to the magnetic field. This potential, typically 1 V for trapping positive ions or -1 V for trapping negative ions, causes ions approaching the trapping plates to turn back toward the center of the observing region (Fig. 2). An oscillatory motion, parallel to the magnetic field and between the trapping plates, is thus superimposed on
TL;DR: Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is a recently developed technique that offers several significant advantages over conventional methods of sampling solids as mentioned in this paper.
Abstract: Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) is a recently developed technique that offers several significant advantages over conventional methods of sampling solids. Some of these include: (1) minimal sample preparation (no sample preparation in a few cases); (2) a very wide range of sample concentrations which yield useful spectra; and (3) a very high sensitivity (less than 100 ng in some cases). DRIFTS has been applied to the analysis of a number of materials of forensic science interest. Specific applications for a variety of evidence types have been found; this work is therefore presented as a series. This paper presents the principles of the technique and examples of the sampling methods, including a microsampling method for liquids. Some of the unique advantages that DRIFTS offers for forensic science work, including better characterization of many compounds, are illustrated. In addition, an explanation of these DRIFTS features is discussed.
TL;DR: In this paper, the authors evaluated the noise performance and behavior of inductively coupled plasma/Fourier transform spectroscopy (ICP-FTS) for atomic emission spectra in the ultraviolet spectral region.
Abstract: Inductively coupled plasma/Fourier transform spectroscopy (ICP-FTS) has the potential to become an excellent combined technique for analytical atomic emission spectrometry. However, the noise performance and behavior of a Fourier transform spectrometer for the measurement of atomic emission spectra in the ultraviolet spectral region is not well understood or characterized. In this study the noise behavior of ICP-FTS is empirically evaluated. The key empirical measurement carried out is the evaluation of complete standard deviation and signal-to-noise ratio spectra (i.e., those parameters measured as a function of wavenumber). A study of these spectra, along with the corresponding emission spectra as a function of concentration and matrix, allows an assessment of noise distribution, multiplex advantage/disadvantage, the nature of the limiting noise, detection limits, and precision.
TL;DR: In this paper, a high-powered, atmospheric-pressure, helium microwave-induced plasma (MIP) is used as the interface between a gas chromatograph (GC) and a Fourier transform near-infrared (FT-NIR) emission spectrometer.
Abstract: A high-powered, atmospheric-pressure, helium microwave-induced plasma (MIP) is used as the interface between a gas chromatograph (GC) and a Fourier transform near-infrared (FT-NIR) emission spectrometer. By the collection of a series of time-resolved interferograms when organic compounds elute from the GC into the plasma, a complete account of both spectral and chromatographic activity is recorded. Computer-generated, element-specific chromatographic reconstructions for each of eight different nonmetals are obtained from a single injection of a chemical mixture. Atomic emission intensity vs. chromatographic retention time is plotted for each of eight or more optical frequencies chosen from the 15,700-7900 cm−1 region. The frequencies are preselected to coincide with spectral lines of C, H, N, O, F, Cl, Br, and S emitting from the helium MIP. This unique GC/MIP/FT-NIR emission spectrometer provides simultaneous multielement-specific chromatographic detection of a variety of nonmetals important to synthetic organic chemistry.
TL;DR: In this paper, a combined analysis of complex permittivity data from the literature is presented for H2O from 10 to 40°C, including microwave data measured by spot frequency methods and recent far-infrared data determined by dispersive Fourier transform spectroscopy.
TL;DR: An analysis method that uses the nonlinear least-squares fit technique has been developed for emission spectra obtained with a Fourier transform spectrometer that was carried out as a correlative measurement for the LIMS satellite experiment.
Abstract: An analysis method that uses the nonlinear least-squares fit technique has been developed for emission spectra obtained with a Fourier transform spectrometer. This method is used for the analysis of submillimeter-region atmospheric emission spectra obtained with a balloon-borne FT spectrometer that was carried out as a correlative measurement for the Limb IR Monitor of the Stratosphere (LIMS) satellite experiment. The retrieved mixing ratios of H2O and O3 in the stratosphere from four spectral intervals have standard deviations of about 10 percent, and the average values agree to within 10 percent of corresponding results from the LIMS satellite experiment which used a broadband emission radiometer in the IR region.
TL;DR: In this paper, Fourier transform spectrometers were used to detect infrared fluorescence of Rb2 in the region 6800-8000 cm-1, arising when the levels of the C 1Π u state are pumped by the 472·7, 476·5, 488·0 and 496·5 nm lines of an argon-ion laser.
Abstract: Infrared fluorescence of Rb2 in the region 6800-8000 cm-1, arising when the levels of the C 1Π u state are pumped by the 472·7, 476·5, 488·0 and 496·5 nm lines of an argon-ion laser, has been recorded by Fourier transform spectrometry. The fluoresence is assigned to the system C 1Π u → 2 1Σ+ g . The 2 1Σ+ g state energy levels up to v = 24 have been determined. The main spectroscopic constants for this 2 1Σ+ g state are The unusual spacing of the vibrational levels reflects the ionic character of the 2 1Σ+ g state.
TL;DR: In this article, rotational and rovibrational transitions of silane-28Si in the ν 2 ν 4 dyad were observed directly with a pulsed microwave Fourier transform spectrometer operating in the 8- to 18-GHz frequency range.
TL;DR: In this paper, an introduction to Fourier transform spectrometers (FTS) is presented for the analytical chemist, with a focus on ICP-FTS. But the basic principles of FTS are not discussed.
Abstract: Recently the search for new and improved analytical chemistry methods has led to investigations at several laboratories into the feasibility of applying Fourier transform spectrometry (FTS) to spectrochemical measurements in the ultraviolet (UV) and visible spectral regions used in atomic spectroscopy. By combining Fourier transform spectrometers with excitation sources such as the inductively coupled plasma (ICP), it is possible to develop new and advanced analytical techniques such as ICP-FTS. Although Fourier transforms have been applied extensively in many scientific fields, the analytical atomic spectroscopist is generally unfamiliar with the basic principles. An introduction to FTS is presented here for the analytical chemist.