Showing papers on "Fourier transform spectroscopy published in 2002"
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15 Apr 2002
TL;DR: In this paper, the authors introduce the physics of light-tissue interaction and the application of light scattering by biological objects in imaging and imaging of tissue and tissue-like phytoplasm.
Abstract: Part 1 Physics of Light-Tissue Interaction - Diagnostical Aspects: Introduction to Light Scattering by Biological Objects Optics of Blood Propagation of Pulses and Photon Density Waves in Turbid Media Coherence Phenomena and Statistical Properties of Multiply Scattered Light Tissue Phantoms. Part 2 Pulse and Frequency-Domain Techniques for Tissue Spectroscopy and Imaging: Time-Resolved Imaging in Diffusive Media Frequency-Domain Techniques for Tissue Spectroscopy and Imaging Monitoring of Brain Activity With Near-Infrared Spectroscopy Signal Quantification and Localization in Tissue Near-Infrared Spectroscopy Time-Resolved Detection of Optoacoustic Profiles for Measurement of Optical Energy Distribution in Tissues. Part 3 Scattering, Fluorescence, and Infrared Fourier Transform Spectroscopy of Tissues: Light Back Scattering Spectroscopy of Epithelial Tissues - Principles and Applications Reflectance and Fluorescence Spectroscopy of Human Skin in Vivo Infrared and Raman Spectroscopy of Human Skin in Vivo Fluorescence Technologies in Biomedical Diagnostics. Part 4 Coherent-Domain Methods for Biological Flows and Tissue Ultrastructure Monitoring: Speckle and Doppler Methods of Blood and Lymph Flow Monitoring Real-Time Imaging of Microstructure and Blood Flows Using Optical Coherence Tomography Speckle Technologies for Monitoring and Imaging of Tissues and Tissue-Like Phantoms Optical Assessment of Tissue Mechanics.
427 citations
TL;DR: In this article, the Fourier transform Raman (FT-Raman) and Fourier Transform Infrared (FTIR) spectra of polyvinylidene fluoride (PVDF) membranes with different porous structures were obtained by the phase inversion process using different casting solvents.
363 citations
TL;DR: The first example of direct structural characterization of polyaromatic ions by coupling a Fourier transform ion cyclotron resonance mass spectrometer with an infrared free-electron laser is presented and opens the way to understanding chemical reaction paths.
Abstract: The first example of direct structural characterization of polyaromatic ions by coupling a Fourier transform ion cyclotron resonance mass spectrometer with an infrared free-electron laser is presented. Measurement of the IR spectra of selectively prepared ionic reactive intermediates is allowed by the association of the high peak power and wide tunability of the laser with the flexibility of the spectrometer, where several mass selection and ion reaction steps can be combined, as demonstrated in the case of iron cation complexes of hydrocarbons. The present experimental setup opens the way to understanding chemical reaction paths.
272 citations
TL;DR: In this article, the Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR) was used for image current detection of coherently excited ICR motion, and the detected signal magnitude and peak shape may be understood from idealized behavior: single ion, zero-pressure, spatially uniform magnetic field, three-dimensional axial quadrupolar electrostatic trapping potential, and spatially, uniform resonant alternating electric field.
197 citations
TL;DR: In this paper, the absorption cross-sections of NO2 at atmospheric temperatures (223-293 K) and pressures (100 and 1000 mbar) were measured in the 250-800 nm (12500-40000 cm −1 ) region using Fourier-transform spectroscopy, at spectral resolutions of 0.5 cm − 1 above 435 nm and 1.0 cm−1 below 435 nm (corresponding to about 8 and 16 pm at this wavelength).
Abstract: The absorption cross-sections of NO2 at atmospheric temperatures (223–293 K) and pressures (100 and 1000 mbar) were measured in the 250–800 nm (12500–40000 cm −1 ) region using Fourier-transform spectroscopy, at spectral resolutions of 0.5 cm −1 above 435 nm and 1.0 cm −1 below 435 nm (corresponding to about 8 and 16 pm at this wavelength). The wavenumber accuracy of the new cross-sections is better than 0.1 cm −1 (about 0.5 pm at 250 nm and about 6.4 pm at 800 nm), validated by recording of I2 absorption spectra in the visible using the same experimental set-up (light source, beam splitter, interferometer optics). The NO 2 absorption spectra were recorded at five different sample temperatures between 223 and 293 K, and at each temperature at two total pressures (100 and 1000 mbar) using pure N2 as buffer gas. Despite the weakness of this effect compared to the density of the NO2 absorption structures, pressure-broadening was clearly observed at all temperatures. The pressure-broadening was partially modeled using a convolution of the low-pressure NO2 absorption spectra with a Lorentzian lineshape. The pressure-broadening coefficient increases significantly with decreasing temperature, as already observed in the mid- and near-infrared vibration–rotation spectra of NO2. This effect is of importance for high-resolution spectroscopy of the earth’s atmosphere in the UV–visible region. © 2002 Elsevier Science B.V. All rights reserved.
184 citations
94 citations
TL;DR: The FT-IR-PAS technique in combination with PLS was found to accurately predict the contents of carbohydrates, i.e., xylose, glucose, mannose, arabinose, galactose, and hexenuronic acid residues, as well as the content of lignin measured in terms of K numbers and corrected K numbers of the pulps.
Abstract: In the present study, hardwood and softwood pulps were characterized by employing Fourier transform infrared photoacoustic spectroscopy (FT-IR-PAS). The pulp samples examined originated from Swedish sulfite and kraft pulp mills, which utilize different cooking processes and modern bleaching technologies. Partial least-squares (PLS) analysis was used to correlate the spectral data obtained with the kappa (K) numbers and carbohydrate compositions of the pulp samples determined by enzymatic hydrolysis and subsequent capillary zone electrophoresis. Using four principal components, the present PLS model based on photoacoustic FT-IR spectra could explain 85% of the variance in the X matrix and 81% of the variance in the Y matrix. The FT-IR-PAS technique in combination with PLS was found to accurately predict the contents of carbohydrates, i.e., xylose, glucose, mannose, arabinose, galactose, and hexenuronic acid residues, as well as the content of lignin measured in terms of K numbers and corrected K numbers of the pulps. From these predictions, the contents of xylan, glucomannan, and cellulose can also be predicted. The content of 4-O-methylglucuronic acid residues is, however, more difficult to predict accurately, using this approach.
88 citations
TL;DR: Measurements by Fourier transform spectroscopy of the vacuum wavenumber, line width, and relative signal strength of 928 lines in the Ar I spectrum illustrate the sensitivity of Ar I wavelengths to conditions in the light source.
Abstract: We report precision measurements by Fourier transform spectroscopy of the vacuum wavenumber, line width, and relative signal strength of 928 lines in the Ar I spectrum. Wavelength in air and classification of the transition are supplied for each line. A comparison of our results with other precision measurements illustrates the sensitivity of Ar I wavelengths to conditions in the light source.
78 citations
TL;DR: In this article, the simultaneous measurements of gas and particle temperatures (280-330 °C) and gas concentrations (CO, CO2, HCl, H2O) were demonstrated in a hot particle-laden flue gas with a fibre-optic probe connected to a Fourier transform infrared spectrometer.
Abstract: Diagnostic tools for real time and direct gas analysis have been developed. The simultaneous measurements of gas and particle temperatures (280-330 °C) and gas concentrations (CO, CO2, HCl, H2O) are demonstrated in a hot particle-laden flue gas with a fibre-optic probe connected to a Fourier transform infrared spectrometer. The gas temperature is found from the thermal radiation at the 2350 cm-1 CO2 fundamental band, whereas the gas concentrations are determined by comparing the measured transmittance spectra with a spectroscopic database and validation measurements using the Hotgas facility at Riso. Measurement uncertainties are discussed. The measured local gas temperatures and concentrations are in good agreement with measurements made with conventional equipment.
77 citations
TL;DR: In this paper, the Fourier transform infrared spectroscopy of deoxyribonucleic acid (DNA) macromolecules and related biological materials in the submillimeter range (i.e., ∼10-500 cm−1) was reported.
Abstract: In this article we report experimental results on Fourier-transform infrared spectroscopy of deoxyribonucleic acid (DNA) macromolecules and related biological materials in the submillimeter range (i.e., ∼10–500 cm−1). Film samples made from commercial DNA fibers, polyadenylic acid potassium salt, and cellular agents such as the spore form of Bacillus subtillis have been prepared and measured. A broad series of measurements carried out in the low frequency region (10–50 cm−1) with a higher resolution of 0.2 cm−1 revealed fine features—multiple dielectric resonances in the submillimeter-wave spectra obtained from DNA samples. These long-wave absorption features are shown to be intrinsic properties of biological materials determined by phonon modes. The emphasis is on reproducibility of experimental spectra and on receiving reliable results. The effects of differences in sample preparation, including sample geometry, orientation, and aging are studied and separated from the phonon effects that determine the ...
70 citations
TL;DR: In this paper, the B 1 Σ + u → X 1 ǫ + g system in 4 0 Ca 2 was studied by Fourier transform spectroscopy and an accurate potential energy curve, which covers 99.8% of the well depth, was derived directly from the experimentally observed differences between ground-state levels.
Abstract: The B 1 Σ + u →X 1 Σ + g system in 4 0 Ca 2 was studied by Fourier-transform spectroscopy. Transitions to 730 ground-state levels were induced by the blue-green lines of an Ar + radiation and the single-mode radiation of a frequency-doubled continuous-wave Nd:YAG yttrium aluminum garnet laser. An accurate potential-energy curve, which covers 99.8% of the well depth, was derived directly from the experimentally observed differences between ground-state levels. Long-range analysis led to a revised value of the ground-state dissociation energy, 1102.08(9) cm - 1 , which differs by more than 7 cm - 1 from the previous experimental determination [C. R. Vidal, J. Chem. Phys. 72, 1864 (1980)]. A first estimate of the s-wave scattering length is reported.
TL;DR: In this article, the first field measurements of volcanic gases using mid-IR difference frequency laser spectroscopy were reported at the summit crater of Masaya volcano, Nicaragua, with the gases being drawn into a multi-pass cell and measured at reduced pressure.
TL;DR: In this article, the Fourier transform spectroscopy (FTS) was used to improve the atomic and molecular databases for the analysis of the astrophysical and atmospheric spectra.
TL;DR: ESI FTICR mass spectrometry of smokeless powder, TNT, and Powermite resolves and identifies numerous nonactive ingredients, many of which are recovered in a postblast residue, in contrast, the residue recovered from an explosion of military C4 yielded several species derived from RDX but virtually none from other ingredients.
Abstract: Commercial explosives are complex mixtures that contain not only the active explosive agent(s) but also a host of other organic and inorganic compounds. The ultrahigh mass resolving power (m/Δm50% >200 000) and mass accuracy (<1 ppm) of electrospray ionization Fourier transform ion cyclotron resonance (ESI FTICR) mass spectrometry allow for definitive identification of various species in TNT, RDX, and HMX. We are thereby able to correct prior misassignments of the elemental compositions of the most abundant negative ions from electrospray of RDX and HMX. Although the (known) active agents of many explosives may be identified by low-resolution MS or MS/MS, it is the other characteristic components (indigenous or artificial additives) whose presence and elemental composition can potentially identify the source of the product. ESI FTICR mass spectrometry of smokeless powder, TNT, and Powermite resolves and identifies numerous nonactive ingredients, many of which are recovered in a postblast residue. In contr...
TL;DR: In this paper, the spin-forbidden b 1 Σ g + (v ′ = 0)← X 3 ǫ g − (v″=0) band of molecular oxygen in air has been measured to show that broad band continuous wave phase shift cavity ring down spectroscopy can be combined with Fourier transform spectrometers.
TL;DR: In this article, an accurate potential energy curve for the ground electronic state of the Cs2 molecule was derived by combining the inverted perturbation approach for internuclear distances up to 11 A, with an analytical expression for longer internuclear distance.
Abstract: This study presents the derivation of an accurate potential energy curve for the ground electronic state of the Cs2 molecule. High resolution laser induced emission spectra data involving vibrational levels of the ground X 1Σg+ state up to v″=135 (16 900 wave numbers) have been determined. The ground state potential energy curve is constructed by combining the inverted perturbation approach for internuclear distances up to 11 A, with an analytical expression for longer internuclear distances. This potential curve allows an improved derivation of the dissociation energy and of the Coulombic parameters governing the Cs(6s)+Cs(6s) interaction in the electronic ground state, compared with values derived either by calculations or by recent photoassociative spectroscopy measurements. The main constants are C6=6836 (±100) a.u.=32.945 (±0.49)×106 cm−1 A6, and De=3649.88 (±0.45) cm−1.
TL;DR: The coupling of Fourier transform infrared (FT-IR) spectroscopy as a new on-line detection principle in capillary electrophoresis (CE) is presented to overcome the problem of total IR absorption by the fused-silica capillaries that are normally employed in CE separations.
Abstract: The coupling of Fourier transform infrared (FT-IR) spectroscopy as a new on-line detection principle in capillary electrophoresis (CE) is presented. To overcome the problem of total IR absorption by the fused-silica capillaries that are normally employed in CE separations, a micromachined IR-transparent flow cell was constructed. The cell consists of two IR-transparent CaF2 plates separated by a polymer coating and a titanium layer producing an IR detection window, 150 μm wide and 2 mm long, with a path length of 15 μm. The IR beam was focused on the detection window using an off-axis parabolic mirror in an optical device (made in-house) attached to an external optical port of the spectrometer. The connections between the fused-silica capillaries and the flow cell were made by a small O-ring of UV-curing epoxy adhesive on the sharply cut ends of the capillaries, allowing the capillaries to be easily replaced. Aqueous solutions comprising mixtures of adenosine, guanosine, and adenosine monophosphate were u...
TL;DR: The results provide evidence that, during the ES ionization, electrolytic reactions occur mainly in the ES tip region, as previously predicted, and demonstrate that ESI-MS signal suppression by tetrabutylammonium perchlorate electrolyte, which can be a problem, is minimized in EC/ESI-MS.
Abstract: A miniaturized two-electrode electrochemical (EC) cell was developed and was coupled on-line with an electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (ESI-FTICR MS). Electrochemistry on-line with mass spectrometry, EC/ESI-FTICR MS, of triphenylamine (TPA), which undergoes one-electron oxidation to form a radical cation (TPA•+), demonstrates a significant sensitivity enhancement compared to ESI-FTICR MS. The on-line EC cell configuration with a stainless steel ES needle as the working electrode produces the highest sensitivity in EC/ESI-MS. The results provide evidence that, during the ES ionization, electrolytic reactions occur mainly in the ES tip region, as previously predicted. The results demonstrate that ESI-MS signal suppression by tetrabutylammonium perchlorate electrolyte, which can be a problem, is minimized in EC/ESI-MS. TPA•+ dimer tetraphenylbenzidine (TPB) can be detected by EC/ESI-MS, together with TPA•+, as TPB•+ and TPB2+. The high mass resolving power of...
TL;DR: In this article, the rotational transitions of the parent species together with the spectra corresponding to both 13C isotopomers have been measured using Fourier transform microwave spectroscopy.
TL;DR: A new class of optical multidimensional Fourier-transform spectroscopy associated with a visible excitation-infrared emission configuration, in which the emitted field results from second-order optical nonlinearities.
Abstract: We report on a new class of optical multidimensional Fourier-transform spectroscopy associated with a visible excitation-infrared emission configuration, in which the emitted field results from second-order optical nonlinearities. This configuration is demonstrated on a phase-matched sample of known nonlinear response by coherent measurement of the mid-infrared field emitted after a femtosecond visible double-pulse excitation.
TL;DR: In this paper, the Dicke effect has been observed for P and Q branch lines of the ν 2 band of H 2 O with Fourier transform spectrometer.
TL;DR: In particular, the limit with which space-time variations in the fine structure constant α can be constrained using quasar spectra depends on the availability of more accurate laboratory rest wavelengths as discussed by the authors.
Abstract: The quality of astronomical spectroscopic data now available is so high that interpretation and analysis are often limited by the uncertainties of the laboratory data base. In particular, the limit with which space–time variations in the fine structure constant α can be constrained using quasar spectra depends on the availability of more accurate laboratory rest wavelengths. We recently measured some transitions in magnesium by high-resolution Fourier transform spectroscopy for this purpose, and we now report measurements on some ultraviolet resonance lines of Zn ii (2062 and 2026 A), Cr ii (2066, 2062 and 2056 A) and Ni ii (1751, 1741, 1709 and 1703 A). Apart from the last line, which is very weak, the uncertainty of these measurements is 0.002 cm−1 (0.08 ma) for the lines around 2000 A and 0.004 cm−1 (0.12 ma) for the lines around 1700 A.
TL;DR: In this article, Fourier transform infrared diffuse reflectance spectroscopy (FT-IR-DRS) spectra and the concentration of pesticide residues were measured for real lettuce samples and the residual concentration of the pesticides were derived by the partial least square regression of the spectra.
Abstract: This paper describes nondestructive pesticide measurement of agricultural products based on Fourier transform infrared diffuse reflectance spectroscopy (FT-IR-DRS). Both FT-IR-DRS spectra and the concentration of the pesticide residues are measured for real lettuce samples. Thereafter, the calibration models to estimate the residual concentration of the pesticides are derived by the partial least square regression of the spectra. Cross validations of the calibration models are also carried out. By using this method, it takes two minutes to measure the multi-elements of pesticide residues in a sample lettuce head. Food safety inspection could be enhanced based on FT-IR-DRS.
TL;DR: In this paper, a new type of microwave-detected microwave-optical double-resonance (MODR) spectroscopy has been developed using a Fourier-transform microwave spectrometer and a tunable pulsed dye laser.
Abstract: A new type of microwave-detected microwave-optical double-resonance (MODR) spectroscopy has been developed using a Fourier-transform microwave spectrometer and a tunable pulsed dye laser. In this method, a free-induction decay (FID) signal was detected instead of the microwave (MW) absorption. To demonstrate the performance, we measured the MODR spectra of the CCS and C 4 H radicals in supersonic jets generated by a pulsed-discharge nozzle. Since the pulsed sources are employed for both the optical and microwave radiations, it is possible to control the relative timing of irradiations of the MW and optical pulses. We were able to obtain two different types of spectra; one is the ordinary population labeling spectrum, and the other is a spectrum obtained by breaking the coherence of molecules. In the latter case, more than 50% of depletion of the FID signal was observed, which is unable to be attained when noncoherent phenomena are used to detect the double-resonance signal.
TL;DR: To demonstrate the potential of the cavity ringdown technique in mid-infrared spectroscopy of thin film samples, absorption losses in a C60 film on a BaF2 substrate are measured using a tunable optical parametric amplifier source.
Abstract: To demonstrate the potential of the cavity ringdown technique in mid-infrared spectroscopy of thin film samples, we measured absorption losses in a C60 film on a BaF2 substrate using a tunable optical parametric amplifier source. With a Brewster angle sample geometry, we achieved a fractional loss sensitivity as small as 1.3 × 10-7 with 1.5 cm-1 resolution, an improvement in sensitivity of 2 orders of magnitude compared to standard Fourier transform infrared methods. At an absorption sensitivity of 5 × 10-7, spectra of several C60 overtone lines were recorded.
TL;DR: In this paper, the rotational spectra of the parent and three isotopic species (13CC2H6S3, C3H634SS2 and C 3H633SS2) in natural abundance of 1,3,5-trithiane have been observed by laser ablation combined with molecular-beam Fourier transform microwave spectroscopy.
10 Dec 2002
TL;DR: In this article, the advantages of applying FTIR on power transformers are studied and the results are presented, showing that all the characteristic peaks needed to be analyzed can be covered if the measurable wavenumber region of the spectrometer is 720 cm/sup -1//spl sim/3400 cm/Sup -1/, and the optimum optical length of the gas cell is around 150 mm.
Abstract: Electrochemical sensors and gas chromatography are widely used in online monitors for dissolved gas-in-oil of power transformers, but some fatal defects exist. In view of the many advantages of FTIR, the basics of applying it on such monitors are studied and the results are presented. Investigation shows that all the characteristic peaks needed to be analyzed can be covered if the measurable wavenumber region of the spectrometer is 720 cm/sup -1//spl sim/3400 cm/sup -1/, and the optimum optical length of the gas cell is around 150 mm. Comparative results demonstrate that absorption spectra obtained by wavelet transmission are consistent to those with their real back ground divided and are independent on spectrometers. It is concluded that such a monitor can be constructed using FTIR that can precisely detect all the diagnostic gases except hydrogen and are free of consuming gases as well as in situ calibration.
TL;DR: Using the differential optical absorption spectroscopy (DOAS) technique and a Fourier transform spectrometer, NO2, SO2, O3, benzene.
TL;DR: The rotational spectrum of the ground vibrational state has been measured from 8 to 240 GHz and accurate spectroscopic constants have been determined for the A internal rotation components of the rotational lines.
TL;DR: In this article, the average particle diameter of macroscopic size in water-based latex emulsions was successfully quantified with correlation coefficients > 0.95, both in calibration (known samples, n = 36) and in prediction (unknown samples,n = 11) against conventionally measured values obtained by dynamic laser diffraction scattering method.
Abstract: Vibrational spectroscopy is utilized to characterize compounds, but it has never been applied to quantitative morphological analysis of polymers in a mass. By using near-infrared Fourier transform Raman spectroscopy coupled with multivariate data analysis, the average particle diameter of macroscopic size in water-based latex emulsions was successfully quantified with correlation coefficients >0.95, both in calibration (known samples, n = 36) and in prediction (unknown samples, n = 11) against conventionally measured values obtained by the dynamic laser diffraction scattering method. This method is valid for samples of various monomer compositions together with various fluorescence and Rayleigh scattering intensities causing different background levels in the spectra. Copyright © 2002 John Wiley & Sons, Ltd.