Showing papers on "Fourier transform spectroscopy published in 1984"
TL;DR: In this article, the authors used dispersive Fourier transform spectroscopy applied to a modular two-beam polarization interferometer to obtain high-resolution millimeter-wave (5 to 1/2 mm) continuous spectra on complex refractive index, complex dielectric permittivity, and loss tangent for a variety of materials.
Abstract: It is no longer necessary to use extrapolated microwave dielectric data when designing millimeter-wave components, devices, and systems. Precision measurements can now be made to generate highly accurate millimeter-wave (5 to 1/2 mm) continuous spectra on complex refractive index, complex dielectric permittivity, and loss tangent for a variety of materials such as common ceramics, semiconductors, crystalline, and glassy materials. The continuous spectra reveal an increase in dielectric loss with increase in frequency in this wavelength range for most materials. Reliable measurements also reveal that the method of preparation of nominally identical specimens can change the dielectric losses by many factors. These broad-band measurements were carried out employing dispersive Fourier transform spectroscopy applied to a modular two-beam polarization interferometer. Data obtained with Fabry-Perot open resonator methods at wavelengths of 5 mm and longer will also be compared.
155 citations
TL;DR: A Fourier transform spectrometer with no mechanical moving parts is described, which may be built in a relatively small size and with moderate cost and may lead to the application to time-resolved spectroscopy.
Abstract: A Fourier transform spectrometer with no mechanical moving parts is described. The interferogram is generated spatially by a triangle common-path interferometer and is detected by a self-scanning photodiode array. The spectrum is reconstructed by fast Fourier transform in a microcomputer system. Since no moving part is used and a common-path interferometer is employed for simple, stable, and easy alignment, this spectrometer may be built in a relatively small size and with moderate cost. The self-scanning photodiode array as a multichannel detector may lead this spectrometer to the application to time-resolved spectroscopy. The optical throughput is much larger than that of a multichannel dispersion-type spectrometer, because in the system neither a slit nor an aperture is necessary. The emission spectra of a low pressure mercury lamp and a LED are shown to demonstrate the system performance.
127 citations
81 citations
TL;DR: In this article, the experimental considerations necessary to effect successful recording of in situ vibrational spectroscopy at the electrode-solution interface are described, and the Fourier transform infrared spectrometer is used.
78 citations
TL;DR: In this paper, the Fourier coefficients computed from the NIR spectra of pulverized tobacco samples can be used to estimate certain chemical constituents in the samples, which can reduce the computation time for calibration by 96% and reduce the magnetic storage space requirements by 98%.
Abstract: Fourier coefficients computed from the NIR spectra of pulverized tobacco samples can be used to estimate certain chemical constituents in the samples. As few as 11 coefficients from the Fourier domain used in a stepwise multiple linear regression (SMLR) model provide results equivalent to a 7-term SMLR model using log I/R from the wavelength domain. The Fourier model reduces the computation time for calibration by 96% compared to the wavelength model, and reduces the magnetic storage space requirements by 98%. Removing the mean term from the Fourier model partially corrects the particle size anomaly encountered in pulverized samples.
67 citations
01 Jan 1984
TL;DR: In this article, a review of the theory and application of Fourier transform infrared spectroscopy to the characterization of polymers is presented, where the basic theory, sampling techniques and spectral operations are described.
Abstract: This review covers the theory and application of Fourier transform infrared spectroscopy to the characterization of polymers. The basic theory, the sampling techniques and the spectral operations are described. The applications discussed include the study of polymer reactions, polymer structure and dynamic effects.
64 citations
TL;DR: In this article, the spin-orbit coupling and Λ-doubling intervals in the ground state were estimated for the (0, 0) band of a 5Σ-5Π transition where the 5Π lower state is ground state.
60 citations
59 citations
54 citations
TL;DR: In this article, detailed information about three new singlet gerade states has been obtained, one of which, (3s, 4s)1 Sigma g+, is known to be involved in optically pumped infrared lasing transitions.
Abstract: Ultraviolet lines of krypton-ion and argon-ion lasers have been used to excite infrared fluorescence in Na2 which has been recorded at high resolution by Fourier transform spectroscopy. Detailed information about three new singlet gerade states has been obtained, one of which, (3s, 4s)1 Sigma g+, is known to be involved in optically pumped infrared lasing transitions. Constants for the states are given.
48 citations
TL;DR: In this article, the authors report on special experimental techniques, which are made possible by rapid-scan FTS and the ability to vary the transmission of these devices with a voltage, and discuss Drude absorption and excitation of 2-D plasmon, intersubband and cyclotron resonances as possible applications.
IBM1
TL;DR: In this article, a liquid analyzer was used for infrared spectroscopy of aqueous solutions of penicillin VK, sodium oxacillin and sodium methicillin.
Abstract: Infrared spectra of aqueous antibiotic solutions were obtained using a new Liquid Analyzer accessory in a Fourier transform infrared (FT-IR) spectrometer. Based on a cylindrical internal reflectance element, the Liquid Analyzer accessory provides a sufficiently short (~0.015 mm) effective pathlength for infrared spectroscopy of aqueous solutions from 3200 to 800 cm−1. Spectra of aqueous solutions of penicillin VK, sodium oxacillin and sodium methicillin are shown. By measuring the absorbance of the beta-lactam carbonyl band, FT-IR spectroscopy with the accessory exhibits analytical sensitivity to less than 0.1% concentration by weight of antibiotic both in aqueous solution and in an actual fermentation broth.
TL;DR: In this paper, Fourier transform infrared spectroscopy was applied to the analysis of the strutural changes which occur within the lipid bilayer as the temperature is varied, providing the basis for the interpretation of phase transitions in complex biomembranes.
TL;DR: In this article, the authors measured the infrared emission spectra of thin polymer layers on flat aluminum plate using Fourier transform infrared spectrometry (FT-IR-EMS) and found that the detection limit was comparable with that of FT-IR RAS when an emission ray was collected at a viewing angle of 70°.
Abstract: Infrared emission spectra of thin polymer layers on flat aluminum plate have been measured using Fourier transform infrared spectrometry. The detection limit of Fourier transform infrared emission spectrometry (FT-IR-EMS) was found to be comparable with that of Fourier transform infrared reflection absorption spectrometry (FT-IR-RAS) when an emission ray was collected at a viewing angle of 70°. The merits of FT-IR-EMS over FT-IR-RAS were demonstrated in the measurement of nonflat surfaces. The residual lubricant on steel tire cords could be detected efficiently by the FT-IR-EMS mode. The linear relationship found between the relative emission intensity and the thickness of film represents the possibility for a quantitative analysis of a thin overlayer on metal surface.
TL;DR: Thermal radiation from sample and detector can affect internally modulated Michelson interferometers (for example, rapid scanning, phase-modulated, or internally chopped) and cause serious systematic errors in the spectra measured by these instruments.
Abstract: Thermal radiation from sample and detector can affect internally modulated Michelson interferometers (for example, rapid scanning, phase-modulated, or internally chopped) and cause serious systematic errors in the spectra measured by these instruments.
TL;DR: In this paper, the Fourier transform of pure NQR was observed by pulsed field cycling for deuterium and well resolved spectra were obtained with high sensitivity showing the low frequency nu0 lines and allowing assignments of quadrupole couplings and asymmetry parameters to inequivalent deuterons.
Abstract: We report the observation of Fourier transform pure NQR by pulsed field cycling. For deuterium, well resolved spectra are obtained with high sensitivity showing the low frequency nu0 lines and allowing assignments of quadrupole couplings and asymmetry parameters to inequivalent deuterons. The technique is ideally applicable to nuclei with low quadrupolar frequencies (e.g., 2D, 7Li, 11B, 27Al, 23Na, 14N) and makes possible high resolution structure determination in polycrystalline or disordered materials.
Journal Article•
TL;DR: In this article, a Fourier transform infrared microspectroscopic method was developed for obtaining kinetic data as a function of pressure and temperature, which employed a diamond-anvil high-pressure cell with heating capability, in conjunction with an FT-IR spectrometer modified with an on-axis cassegrain type beam condenser.
Abstract: A Fourier transform infrared microspectroscopic method has been developed for obtaining kinetic data as a function of pressure and temperature. The method employs a diamond-anvil high-pressure cell with heating capability, in conjunction with an FT-IR spectrometer modified with an on-axis cassegrain-type beam condenser. Time-dependent absorption spectra have been obtained for the thermal decomposition of 1,3,5-trinitrohexahydro-1,3,5-triazine (RDX) as a function of pressure and temperature. The pressure dependence of the temperature of thermal decomposition has also been determined. The method has wide applicability to kinetic measurements in general.
TL;DR: In this paper, the detection limits for the determination of sulfur using a monochromator in combination with either a Si photodiode or a Si array at the 0.922 and 1.046 μm lines are presented.
Abstract: Several spectrochemical measurement systems have been used for the characterization of near-IR emission spectra from the inductively coupled plasma, with particular emphasis on the determination of sulphur. Background emission spectra of Ar and N2/Ar ICPs and the emission spectrum of dimethylsulphoxide (DMSO) are presented and the major emission lines of Ar, N, C, O and S are tabulated. These measurements and data cover the spectral region from about 3 μm to 0.7 μm and were obtained using a Fourier transform spectrometer. Detection limits for the determination of sulfur using a monochromator in combination with either a Si photodiode, a Si photodiode array or a PbS detector at the 0.922 and 1.046 μm lines are presented. The best detection limit (20 ppm) was obtained with the Si photodiode detector at the 0.922 μm line.
TL;DR: In this paper, the behavior of the nuclear magnetization during the repetitive application of the pulse-data acquisition sequence is considered from the classical point of view, from which some relations between signal intensity and experimental parameters can be obtained.
Abstract: The behavior of the nuclear magnetization during the repetitive application of the pulse-data acquisition sequence is considered from the classical point of view, from which some relations between signal intensity and experimental parameters can be obtained.
TL;DR: In this paper, a new time-resolved Fourier transform infrared spectroscopy technique has been developed for commercial fast scanning interferometers, which can be easily adapted to measure a variety of external experiments.
Abstract: A new time-resolved Fourier transform infrared spectroscopy technique has been developed for commercial fast scanning interferometers. In contrast to the methods developed previously, this one has greater flexibility in the time resolution achievable (100 microseconds to seconds) and can be easily adapted to measure a variety of external experiments. Experiments are given demonstrating the correct operation of this technique and its applicability in following the deformation behavior in polymers.
TL;DR: The optical constants of the polymer TPX have been determined between 30 and 420 cm−1 at ambient temperature by the technique of dispersive Fourier transform spectroscopy as mentioned in this paper.
TL;DR: In this article, the complex indices of refraction of materials between frequencies of 120 and 550 GHz were measured for crystal quartz, crosslinked polystyrene, glass-loaded polytetrafluoroethylene (Duroid 5880), and nickel ferrite (Trans-Tech 2-111).
Abstract: We have used non-dispersive Fourier-transformspectroscopic techniques to measure the complex indices of refraction of materials between frequencies of 120 and 550 GHz. Results are presented for crystal quartz, crosslinked polystyrene (Rexolite 1422), glass-loaded polytetrafluoroethylene (Duroid 5880) and a nickel ferrite (Trans-Tech 2-111). These results are compared with other data on these materials in this frequency range. The accuracy of these measurements yields a considerable improvement in the near-millimeter-wave characterization of several of these materials. For materials other than crystal quartz, our results are the first measurements of their properties over the entire frequency range studied.
TL;DR: In this article, the authors describe the first demonstration of random-noise excitation for FTMS employing a simple noise excitation source and compare a random excitation spectrum with the corresponding frequency sweep spectrum.
TL;DR: In this paper, the line shapes obtained with pulsed microwave Fourier transform spectroscopy carried out on a static gas at very low pressures in a waveguide absorption cell are described.
Abstract: We describe theoretically the line shapes obtained with pulsed microwave Fourier Transform Spectroscopy carried out on a static gas at very low pressures in a waveguide absorption cell. A density-matrix formalism is used to study the interaction of a two-level quantum system with a classical, pulsed, travelling wave electric field in a rectangular waveguide. Neglecting intermolecular collisions, the effects of the molecular velocity distribution the linewidths of microwave transitions are considered, allowing for Doppler broadening, wall collisions and microwave-field inhomogeneities. General expressions for the decay function of sample polarisation are derived and examples for the resulting line shapes are given.
TL;DR: In this paper, the first two excited 1Σg+ electronic states were derived from spectra recorded at high resolution by Fourier transform spectroscopy, and the main molecular constants were: (2) 1 Σg +: Tc = 12114.090 cm−1, ωe = 23.4.
TL;DR: In this article, Fourier Transform laboratory measurements have been carried out, for the first time in the 8-85 cm−1 spectral region, with an unapodized resolution of 3.3.
Abstract: Fourier Transform laboratory measurements have been carried out, for the first time in the 8–85 cm−1 spectral region, with an unapodized resolution of 3.3. 10−3 cm−1 and a frequency accuracy of 2. 10−4 cm−1. Samples from spectra of several molecules namely: CO, O3, H2O2, NO, NO2, HNO3, SO2, H2S, HOCL, NOCL, HNCO, ND3 and AsH3 are presented to show both the quality of the measurements and the type of information supplied by high resolution spectroscopy in the submillimeter region.
TL;DR: The effects of changing spectral radiance during the scan of an interferometer on the spectra obtained from the interferogram are considered and the changes in the appearance of spectral features are hardly changed beyond a few resolution elements from the changing features.
Abstract: The effects of changing spectral radiance during the scan of an interferometer on the spectra obtained from the interferogram are considered. For well-behaved variations the integrated radiance and base line are the same as at the zero path difference of the interferometer. The changes in the appearance of spectral features are hardly changed beyond a few resolution elements from the changing features.