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Showing papers on "Fourier transform spectroscopy published in 1999"


Journal ArticleDOI
TL;DR: In this paper, the structure of lanthanum aluminosilicate (LAS) glasses, containing: (15−25) mol% La2O3, (15-35)mol% Al2O 3 and (40−70) mol % SiO2, were studied by 27Al nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR).
Abstract: The structure of lanthanum aluminosilicate (LAS) glasses, containing: (15–25) mol% La2O3, (15–35) mol% Al2O3 and (40–70) mol% SiO2, were studied by 27Al nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). The effects of La2O3 and Al2O3 content on the properties and structure of the LAS glasses were evaluated. Al3+ ion enters into the glass structure mainly in fourfold co-ordination, forming ( AlO 4/2 ) − tetrahedra, and only in small amounts in fivefold and sixfold co-ordination. La3+ acts as network modifier, producing more non-bridging oxygen atoms as its content increases.

176 citations


Journal ArticleDOI
TL;DR: In this article, a miniaturized Fourier transform spectrometer (FTS) based on optical microelectromechanical system technology is presented, which is a Michelson interferometer with one scanning mirror.
Abstract: We present a miniaturized Fourier transform spectrometer (FTS) based on optical microelectromechanical system technology The FTS is a Michelson interferometer with one scanning mirror A new type of electrostatic comb drive actuator moves the mirror We have measured a nonlinearity of the driving system of ±05 µm for a displacement of 385 µm A method is presented to correct the spectrum to get rid of the nonlinearity The driving reproducibility is ±25 nm The measured resolution of the spectrometer after the phase correction is 6 nm at a wavelength of 633 nm

167 citations


Journal ArticleDOI
TL;DR: In this paper, a new approach to the Fourier transform infrared (FTIR) absorption spectroscopy of molecular clusters in pulsed supersonic jets is developed to the point where it is competitive with high-sensitivity laser absorption techniques for intermediate and large molecular systems.
Abstract: A new approach to the Fourier transform infrared (FTIR) absorption spectroscopy of molecular clusters in pulsed supersonic jets is developed to the point where it is competitive with high-sensitivity laser absorption techniques for intermediate and large molecular systems. A combination of rapid spectral acquisition and of a buffered jet chamber enables the use of intense gas pulses which cover complete interferometer scans. Applications to (N2O)n, (CH3OH)n and (HCl)n demonstrate the capabilities of this technique. Investigations of the association of bulky alcohols and of clusters within clusters illustrate some ongoing research.

158 citations


Journal ArticleDOI
TL;DR: In this article, a noninvasive continuous measurement of leaf water content is presented based on transmission measurements of terahertz radiation with a null-balance quasi-optical transmissometer operating at 94 GHz.
Abstract: A novel technique for the noninvasive continuous measurement of leaf water content is presented. The technique is based on transmission measurements of terahertz radiation with a null-balance quasi-optical transmissometer operating at 94 GHz. A model for the propagation of terahertz radiation through leaves is presented. This, in conjunction with leaf thickness information determined separately, may be used to quantitatively relate transmittance measurements to leaf water content. Measurements using a dispersive Fourier transform spectrometer in the range of 100 GHz-500 GHz using Phormium tenax and Fatsia japonica leaves are also reported.

143 citations


Journal ArticleDOI
TL;DR: In this paper, two experimental techniques of cavity ringdown spectroscopy and high-resolution, long-path Fourier transform (FTT) spectrograms have been used to measure quantitative absorption spectra and determine the integrated absorption intensity (Sint,B) for the O2 a 1Δg −X 3 Σg− (0,0) band Einstein A-factors and radiative lifetimes for the 0,0 band.
Abstract: The two experimental techniques of cavity ringdown spectroscopy and high-resolution, long-path Fourier transform spectroscopy have been used to measure quantitative absorption spectra and determine the integrated absorption intensity (Sint,B) for the O2 a 1Δg–X 3Σg− (0,0) band Einstein A-factors and radiative lifetimes for the O2 a 1Δg v=0 state have been derived from the Sint,B values The two methods give values for the integrated absorption intensity that agree to within 2% The value recommended from the results of this study is Sint,B=310±010×10−24 cm molecule−1, corresponding to an Einstein-A coefficient of A=219±007×10−4 s−1 and a radiative lifetime of τrad=76 min The measurements are in excellent agreement with the recent absorption study of Lafferty et al [Appl Opt 37, 2264 (1998)] and greatly reduce the uncertainty in these parameters, for which accurate values are required for determination of upper stratospheric and mesospheric ozone concentrations

141 citations


Proceedings ArticleDOI
23 May 1999
TL;DR: Spectroscopic optical coherence tomography (OCT), an extension of conventional OCT, is demonstrated for performing cross-sectional tomographic and spectroscopic imaging in a simple model as well as in vivo in the Xenopus laevis (African frog) tadpole.
Abstract: Summary form only given. Optical coherence tomography (OCT) has recently emerged as a powerful imaging technique for biological tissue. OCT can perform real time, in situ imaging of tissue cross-sectional microstructure with micron resolution. The spatial resolution of OCT depends directly on the optical bandwidth and thus on the coherence length of the used light source. Using a femtosecond mode-locked Ti:sapphire laser as a low coherence source, in-vivo imaging of biological tissue has been demonstrated with a spatial resolution below 2 /spl mu/m. We report a spectroscopic OCT approach which detects the full interferometric fringe signal and extracts spectroscopic data from the measurement using Fourier signal processing.

81 citations


Journal ArticleDOI
TL;DR: In this article, a new Fourier transform infrared (FT-IR) spectrometer is described by which it is possible to acquire interferograms with 0.25 cm optical path difference (4 cm−1 spectral resolution) in less than 1 ms.

75 citations


Journal ArticleDOI
TL;DR: In this paper, a new spectroscopic investigation on the X(1)Sigma(+) electronic ground state of the RbCs molecule is reported by using laser-induced fluorescence combined with Fourier transform spectroscopy (LIF-FTS).

69 citations


Journal ArticleDOI
TL;DR: A simple and powerful method for obtaining analytic instrument line shapes (ILS's) for Fourier transform spectrometers is explained and results match earlier ILS simulations.
Abstract: A simple and powerful method for obtaining analytic instrument line shapes (ILS’s) for Fourier transform spectrometers is explained. ILS’s for off-axis circular and rectangular detectors are calculated to illustrate the method. Results match earlier ILS simulations. The contribution of the nonuniformity of light intensity across the detector surface is also taken into account.

56 citations


Journal ArticleDOI
TL;DR: In this article, a mesoporous silica molecular sieve (MCM-41) with pore diameters from 3 to 10nm was synthesized by a liquid-crystal template mechanism.

53 citations


Journal ArticleDOI
TL;DR: In this article, Fourier Transform infrared spectrometry has been used to study the vibrational spectroscopy of water clusters prepared in a supersonic expansion, and the first observation of bending vibration for any size gas-phase water cluster was made.
Abstract: Fourier Transform infrared spectrometry has been used to study the vibrational spectroscopy of water clusters prepared in a supersonic expansion. The clusters are assigned as being composed of 10−100 waters based on consideration of the free OH and bound OH vibrations and the experimental conditions used. Four vibrational features were observed simultaneously including the bend, free OH stretch, bound OH stretch, and an unresolved group of intermolecular vibrations. No absorption features were observed between 4000 and 8000 cm-1. This is the first observation of the bending vibration for any size gas-phase water cluster.

Journal ArticleDOI
TL;DR: In this paper, attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy was used to analyze hydrogen−deuterium exchange for streptavidin and its complex with biotin.
Abstract: Hydrogen−deuterium exchange for streptavidin and its complex with biotin is studied by means of attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy. To analyze the spectral changes upon deuteration, difference spectra and two-dimensional correlation spectra are calculated. We find that the exchange rate varies with the secondary structure in which the exchanging amide protons are incorporated. The most slowly exchanging protons, with a characteristic time constant on the order of hours, are part of the β-sheet secondary structure. The separation in time of exchange of the β-sheet from other structural elements allows the amide II and II‘ frequencies of the β-sheet (1530 and 1445 cm-1) to be identified. A second component which exchanges more rapidly than the β-sheet is characterized by its amide I frequencies 1680, 1640, and 1465 cm-1. This component is attributed to the exchange of amide groups in secondary structures other than the central β-barrel. Binding of the ligand res...

Journal ArticleDOI
TL;DR: In this article, the rotationally resolved nν1 (n=2-6) overtone transitions of the CH acetylenic stretching of propyne (CH3-C≡C-H) have been recorded by using Fourier transform spectroscopy, various intracavity laser absorption spectrometers (n =3, 4, and 6) and cavity ring down spectroscopic (CRDS) (n.5).
Abstract: The rotationally resolved nν1 (n=2–6) overtone transitions of the CH acetylenic stretching of propyne (CH3–C≡C–H) have been recorded by using Fourier transform spectroscopy (n=2), various intracavity laser absorption spectrometers (n=3, 4, and 6) and cavity ring down spectroscopy (CRDS) (n=5). The 2ν1, 3ν1, and 6ν1 bands exhibit a well-resolved and mostly unperturbed J-rotational structure, whose analysis is reported. The 5ν1 band recorded by pulsed CRDS shows an unresolved rotational envelope. In the region of 12 700 cm−1, an anharmonic interaction is confirmed between 4ν1 and 3ν1+ν3+ν5. The band at a higher wave number in this dyad exhibits a partly resolved K-structure, whose analysis is reported. The mixing coefficient of the two interacting states is determined consistently using different procedures. The 1/35 anharmonic resonance evidenced in the 4ν1 manifold induces weaker intensity borrowing from the 2ν1 and 3ν1 levels to the ν1+ν3+ν5 and 2ν1+ν3+ν5 level, respectively, which have been predicted an...

Journal ArticleDOI
TL;DR: In this article, the authors developed a new dynamic infrared spectroscopy in which step-scan Fourier transform infrared (FT-IR) interferometry, surface-enhanced infrared absorption (SEIRAS), and attenuated-total-reflection (ATR) techniques were coupled.

Journal ArticleDOI
TL;DR: In this paper, the Fourier transform intra-cavity laser absorption spectroscopy (FT-ICLAS) was used to record the νOD=5 stretching overtone of HOD at a resolution of 0.05 cm-1 in the region 12550-12900 cm 1.
Abstract: The newly developed high resolution Fourier-transform intra-cavity laser absorption spectroscopy (FT-ICLAS) was utilized to record the νOD=5 stretching overtone of HOD at a resolution of 0.05 cm-1 in the region 12550–12900 cm-1. The spectrum was rotationally analysed and the spectroscopic parameters were derived from nonlinear least-squares fitting. Good agreement of the observed with the calculated energy levels was achieved.

Journal ArticleDOI
TL;DR: In this article, Fourier transform spectrometers were used for measuring 294 Ba I lines and 52 Ba II lines with uncertainties in the range ±0.001 cm-1 to ± 0.01 cm- 1.
Abstract: Barium spectra emitted from hollow cathode discharges and recorded with Fourier transform spectrometers in the region 1700–31 000 A have been used for measuring 294 Ba I lines and 52 Ba II lines with uncertainties in the range ±0.001 cm-1 to ±0.01 cm-1. Energy level values have been derived from the measurements. The energy levels have been used for an improved determination of the Ba II ionization limit, giving the value 80686.30 ± 0.10 cm-1.

Journal ArticleDOI
TL;DR: In this article, the effects of ultraviolet (UV) irradiation and heat-treatment on hydrogen speciation in H2 loaded Ge-doped silica glasses have been investigated using Fourier transform infrared (FTIR) spectroscopy and high-resolution 1H nuclear magnetic resonance (NMR).
Abstract: The effects of ultraviolet (UV) irradiation and heat-treatment on hydrogen speciation in H2 loaded Ge-doped silica glasses have been investigated using Fourier transform infrared (FTIR) spectroscopy and high-resolution 1H nuclear magnetic resonance (NMR) spectroscopy. Various H-bearing species, including H2, SiOH, GeOH, SiH, GeH, GeH2, are identified in the glasses. Their characteristic infrared 7(IR) absorption frequency and 1H NMR chemical shift values are determined, and the molar absorption coefficients of these IR bands calibrated. IR measurements based on the molar absorption coefficients calibrated in this study indicate that GeH and OH are the major H-bearing species produced in hydrogen-loaded germanosilicate glass upon intense UV irradiation.

Proceedings ArticleDOI
22 Jun 1999
TL;DR: Astronomical spectroscopy at submillimetre wavelengths holds much promise for fields as diverse as the study of planetary atmospheres, molecular clouds and extragalactic sources as mentioned in this paper.
Abstract: Astronomical spectroscopy at submillimetre wavelengths holds much promise for fields as diverse as the study of planetary atmospheres, molecular clouds and extragalactic sources.

Journal Article
TL;DR: In this paper, the structural modifications occurring in the glass network as consequence of the heat treatments performed near the glass transition temperature and their effect on the devitrification behavior have been examined by Fourier transform infrared spectroscopy, differential thermal analysis and x-ray diffraction.
Abstract: Glasses whose compositions are expressed by the general formula: (50-x/2) BaO. (50-x/2) B 2 O 3 .xTiO 2 with x=4, 8 and 16 have been prepared and the structural modifications occurring in the glass network as consequence of the heat treatments performed near the glass transition temperature and their effect on the devitrification behaviour have been examined by Fourier transform infrared spectroscopy, differential thermal analysis and x-ray diffraction. The 16 h heat treatment produces a microphase separation in the glassy matrix of all investigated glasses with a typical droplet structure'. Furthermore, for the glass with x=16, during this heat treatment nucleation of BaB 4 O 7 crystals occurs. These crystals, for long nucleation times, act as heterogeneous nuclei for the growth of β-BaB 2 O 4 crystals.

Journal ArticleDOI
TL;DR: In this article, the Fourier transform infrared (FTIR) and the FT-Raman spectra of a new thiophene-based oligomer in neutral form were studied and correlated with vibrational data of unsubstituted α-linked oligothiophenes.
Abstract: We have studied the Fourier transform infrared (FTIR) and the Fourier transform Raman (FT-Raman) spectra of a new thiophene-based oligomer in neutral form. The compound has a well–barrier–well structure, where the well parts are two bithienyl end moieties and the barrier part is a vinylene fragment with a larger energy gap. Characteristic features are correlated with vibrational data of unsubstituted α-linked oligothiophenes and α,α′-dimethyl end-capped oligothiophenes to assess information about the effective conjugation length of this oligomer. The FTIR and FT-Raman spectra have also been theoretically calculated at the B3LYP/6-31G** and RHF/6-31G** levels, respectively, to propose a vibrational assignment for the main bands in the whole spectral range.

Proceedings ArticleDOI
15 Mar 1999
TL;DR: In this paper, the optical absorption spectrum of the (ν2+2ν3) combination band of methane in the 1.33 μm range was investigated by photoacoustic and FTIR long path spectroscopy.
Abstract: The optical absorption spectrum of the (ν2+2ν3) combination band of methane in the 1.33 μm range was investigated by photoacoustic and FTIR long path spectroscopy. The photoacoustic measurements were performed with a commercial external cavity diode laser (ECDL) and a differential photoacoustic (PA) detector. The absorption spectrum was obtained by scanning the wavelength of the ECDL through the 1317–1343 nm range of the methane (ν2+2ν3) band. A certified mixture of 1000 ppmV methane in synthetic air was used in a continuous flow mode. A linear concentration dependence of the PA signal was observed in the region of 10–1000 ppmV CH4. The absorption coefficients calculated from the measured sound pressure are in good agreement with the values given in the literature for several R-branch lines. Optical absorption measurements were performed with a long path White cell in combination with a FTIR spectrometer.

Book ChapterDOI
Derek Marsh1
TL;DR: This chapter discusses two forms of spectroscopy, spin-label electron spin resonance (ESR) spectroscopic, and Fourier transform infrared (FTIR) Spectroscopy that are particularly well adapted to membrane and ion channel studies.
Abstract: Publisher Summary This chapter discusses two forms of spectroscopy, spin-label electron spin resonance (ESR) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy that are particularly well adapted to membrane and ion channel studies. FTIR is a branch of vibrational spectroscopy, whereas spin label ESR is a form of magnetic resonance. These two techniques are capable of giving complementary structural and dynamic information and have the advantage that, unlike visible, fluorescence, or UV spectroscopy, they are insensitive to opaque or highly scattering particulate samples. The requirements for the quantity of sample are similar in both cases. Neither has the high sensitivity of, for example, fluorescence spectroscopy, but both have specific advantages in terms of the detailed information that may be obtained. In general, quantities in excess of 100 μg will be required, although higher sensitivity can be achieved by using attenuated total reflection techniques in infrared spectroscopy and loop-gap resonators, coupled with microwave preamplifiers, in the case of spin-label ESR spectroscopy.

Journal ArticleDOI
TL;DR: A differential optical absorption spectroscopy optical setup based on a Bruker IFS 120M spectrometer is built, enabling the simultaneous detection of numerous chemical species with better discriminating properties.
Abstract: Concentration measurements of trace gases in the atmosphere require the use of highly sensitive and precise techniques. The UV–visible differential optical absorption spectroscopy technique is one that is heavily used for tropospheric measurements. To assess the advantages and drawbacks of using a Fourier transform spectrometer, we built a differential optical absorption spectroscopy optical setup based on a Bruker IFS 120M spectrometer. The characteristics and the capabilities of this setup have been studied and compared with those of the more conventional grating-based instruments. Two of the main advantages of the Fourier transform spectrometer are (1) the existence of a reproducible and precise wave-number scale, which greatly simplifies the algorithms used to analyze the atmospheric spectra, and (2) the possibility of recording large spectral regions at relatively high resolution, enabling the simultaneous detection of numerous chemical species with better discriminating properties. The main drawback, on the other hand, is due to the fact that a Fourier transform spectrometer is a scanning device for which the scanning time is small compared with the total measurement time. It does not have the signal integration capabilities of the CCD or photodiode array-based grating spectrographs. The Fourier transform spectrometer therefore needs fairly large amounts of light and is limited to short to medium absorption path lengths when working in the UV.

Journal ArticleDOI
TL;DR: In this article, the surface properties of sheds of composite insulators are analyzed using X-ray photoelectron spectroscopy and emission Fourier transform infrared (FTIR) spectrograms.
Abstract: Methods of sampling and analyzing the surface material of sheds of composite insulators are reviewed. It is shown that scanning electron microscopy gives useful information from slivers cut from the insulator surfaces, and emission Fourier transform infrared (FTIR) spectroscopy enables derivation of indicators of material oxidation to be developed from surface swabbing with solvents. FTIR absorption spectroscopy and diffuse reflectance FTlR spectroscopy give indicators of surface chalking for ehtylene propylene diene monomer (EPDM) insulators. X-ray photoelectron spectroscopy is used to determine surface layer elemental composition and concentration of oxidized bonds. The techniques are applied to field aged 275 kV EPDM and silicone rubber insulators and tentative correlations developed between surface condition and leakage current. Cluster analysis of results from sampling of a large population of EPDM insulators shows that the surface analysis methods facilitate grouping by location and manufacturer.

Journal ArticleDOI
TL;DR: The effluent gas-phase composition from the atmospheric pressure reaction between tetraethylorthosilicate (TEOS) and ozone was investigated as a function of reactor temperature and initial reactant molar ratio.
Abstract: The effluent gas-phase composition from the atmospheric pressure reaction between tetraethylorthosilicate (TEOS) and ozone was investigated as a function of reactor temperature and initial reactant molar ratio Online, continuous quantitative determination of gas species was achieved using Fourier transform infrared techniques TEOS decomposition was a function of initial ozone concentration and reactor temperature Ozone enhanced TEOS decomposition was found to generate carbon monoxide, carbon dioxide, formic and acetic acids, and water, in addition to unreacted source species

Journal ArticleDOI
TL;DR: In this article, the authors presented the first high-resolution infrared absorption study of the ν 3 fundamental of white phosphorus, P 4, using the STDS (Spherical Top Data System) software.

Journal ArticleDOI
TL;DR: In this paper, the Fourier transform infrared spectrum of the ν 6 and 2ν 9 bands of deuterated formic acid (HCOOD) was recorded with an apodized resolution of 0.004 cm −1 in the frequency range of 930-1040 cm − 1.

Journal ArticleDOI
TL;DR: In this paper, the presence of systematic ordinate errors in Fourier transform spectroscopy (FTS) is discussed, largely in terms of interreflection effects between the various interfaces of a two-beam interferometer and its adjacent optical components.

Journal ArticleDOI
TL;DR: In this paper, near-infrared absorption cross-sections of oxygen and nitrogen gas mixtures were determined from laboratory measurements using Fourier transform spectroscopy and a long path-length absorption cell.

Journal ArticleDOI
TL;DR: In this paper, the effect of spectroscopic ellipsometry, using the effective medium approximation (SE-EMA), may be used meaningfully to analyze plasma-enhanced chemical vapor deposition silicon nitride films, using Rutherford backscattering spectrometry and Fourier transform infrared spectroscopy as reference methods.
Abstract: This work addresses the issues of whether spectroscopic ellipsometry, using the effective medium approximation (SE-EMA), may be used meaningfully to analyze plasma-enhanced chemical vapor deposition silicon nitride films We use Rutherford backscattering spectrometry and Fourier transform infrared spectroscopy as reference methods and compare the results to the results of SE-EMA analyses and Auger analyses The results are that Auger analysis, using properly determined sensitivity factors, gives compositions which are within the uncertainty of the reference methods SE-EMA, on the other hand, always overestimates the oxide contribution and underestimates the nitride contribution Probable causes are discussed