Showing papers on "Photoacoustic spectroscopy published in 1992"
TL;DR: The purpose of this in vitro investigation was to characterize the chemical structure of lased root surfaces using Fourier transform infrared photoacoustic spectroscopy (FTIR/PAS), which showed a decrease in the protein/mineral ratio in comparison to the control.
Abstract: Recently lasers have been recommended as an alternative or adjunctive therapy in the control and treatment of periodontally diseased root surfaces. The purpose of this in vitro investigation was to characterize the chemical structure of lased root surfaces using Fourier transform infrared photoacoustic spectroscopy (FTIR/PAS). Cementum samples, 6 mm x 2 mm, were cut from the root surface of extracted non-carious, unerupted human molars. The experimental samples were lased with a Nd:YAG laser at an average energy of 80 mJ at 10 pulses per second. Total lasing time ranged from 1 minute 45 seconds to 4 minutes. A non-lased cementum sample served as the control. All spectra were recorded from 4000 to 400 cm-1 using the photoacoustic cell attachment on an Analect RFX-65 FTIR Spectrometer. Photoacoustic FTIR spectra of lased cementum samples showed a decrease in the protein/mineral ratio in comparison to the control. Breakdown of protein at the root surface potentially contributed to an ammonium band at 2010 cm-1. The decreased protein/mineral ratio and the potential surface contamination with protein by-products, may ultimately affect cell reattachment at the cementum surface.
67 citations
TL;DR: In this article, the authors used a miniature piezoelectric transducer to study and monitor photoablation in air by an ultraviolet KrF excimer laser and found that the amplitude of the ablative-piston signal is a monotonic function of the etch depth per pulse.
Abstract: We show for the first time the use of pulsed photoacoustic detection using a miniature piezoelectric transducer to study and monitor photoablation in air by an ultraviolet KrF excimer laser. At incident laser fluences below the ablation threshold, the photoacoustic signal is produced by the thermal expansion of the air near the irradiated surface (‘‘thermal‐piston signal’’) and propagates at the speed of sound. Above the ablation threshold, the photoacoustic signal contains an additional component due to the ejection of ablated materials (‘‘ablative‐piston signal’’); this propagates initially at supersonic speeds. The amplitude of the ablative‐piston signal is found to be a monotonic function of the etch‐depth per pulse. Hence, by accumulating the amplitude of the ablative acoustic pulse, the total etch depth can be monitored in real time.
53 citations
Abstract: An observed change in the photoacoustic signal frequency response of laser processed stainless‐steel and carbon steel samples with respect to unprocessed reference samples is reported. A recently developed thermal wave theory for depth profiling of bulk inhomogeneities (where the surface thermal diffusivity is known and is the same as the homogeneous reference material) in condensed phases with arbitrary, continuously varying thermal diffusivity profiles [A. Mandelis, S. B. Peralta, and J. Thoen, J. Appl. Phys. 70, 1761 (1991)] has been modified to obtain quantitative thermal diffusivity profiles extending from the surface into the bulk. Profiles obtained using this method, which is, in principle, of nondestructive nature, are consistent with the profiles obtained from destructive methods such as cross‐sectional optical metallographic examination and microhardness testing.
38 citations
TL;DR: In this paper, photoacoustic spectra have been obtained at room temperature from n and p-type single crystals of CuInSe 2 grown from a near-stoichiometric melt by the vertical Bridgman technique.
38 citations
TL;DR: In this article, two-photon photoacoustic spectra of acetone-h6 and −d6 have been recorded using a pulsed laser in the 3p←n Rydberg transition region.
28 citations
TL;DR: In this paper, a Fourier transform intracavity laser absorption technique was used for gaseous CHD3 at room temperature with 0.12 cm−1 resolution to obtain the absorption spectra for two bands belonging to the N=6 polyad, 61 (6ν1) and 62 (5ν1+2ν5), and a rotational analysis for 61 including transitions up to J=13, verified by means of groundstate combination differences, was reported.
Abstract: Absorption spectra in the 16 100–16 320 cm−1 region have been recorded for gaseous CHD3 at room temperature with 0.12 cm−1 resolution using a Fourier transform intracavity laser absorption technique. Two bands belonging to the N=6 polyad, 61 (6ν1) and 62 (5ν1+2ν5), were identified and a rotational analysis for 61 including transitions up to J=13, verified by means of ground‐state combination differences, is reported. Comparison with rotational contants obtained from photoacoustic laser spectra at 77 K is discussed.
26 citations
TL;DR: In this paper, an alternative mechanism based on the concept of explosive removal is proposed to remove the ablation timescale threshold and surface pressure of excimer laser ablated ceramic and thin film Y•Ba•Cu•O superconductors.
Abstract: Nanosecond photoacoustic measurements of excimer laser ablated ceramic and thin film Y‐Ba‐Cu‐O superconductors are reported that provide information on the ablation timescale threshold and surface pressure. Results for the surface pressure are found to be inconsistent with a simple surface vaporization model, suggesting that a different removal mechanism is operative. The outline of an alternative mechanism based on the concept of explosive removal is put forward.
25 citations
23 citations
TL;DR: In this paper, the photoacoustic signal from a green leaf is the vectorial sum of photothermal (heat emitted by non-radiative deexcitation of molecules) and photobaric (photosynthetic O 2 exchanges) contributions.
13 citations
TL;DR: Owing to the linearity of the photoacoustic signal, the absorption coefficients of Freons were measured on isotopic (13)C(16)O(2) laser lines.
Abstract: Owing to the linearity of the photoacoustic signal, the absorption coefficients of Freons were measured on isotopic 13C16O2 laser lines.
12 citations
TL;DR: In this paper, Fourier transform laser-induced photoacoustic spectroscopy (FT-LIPAS) was applied to the speciation of uranium(VI) in NaHC0 3 /NaC10 4 solution/precipitate systems.
Abstract: We have been investigating Fourier transform laser-induced photoacoustic spectroscopy (FT-LIPAS) for speciation of actinides in aqueous solution, and ultraviolet, visible and nearinfrared photoacoustic spectroscopy (UV-VIS-NIR PAS) and Fourier transform infrared photoacoustic spectroscopy (FT-IR PAS) for speciation in the solid phase. These spectroscopic methods were applied to the speciation of uranium(VI) in NaHC0 3 /NaC10 4 solution/precipitate systems. The results show that FT-LIPAS is capable of speciation of aqueous species at concentrations of 10 M and that UV-VIS-NIR PAS and FT-IR PAS are useful for the speciation of the solid phase, especially for amorphous materials.
01 Jan 1992
TL;DR: In this article, the physical basis for signal generation and enhancement methods for pulsed and continuous-modulated excitations as well as the various sources of noises which become significant when the absorption approaches the part-per-million level or below.
Abstract: This paper provides physical discussions of factors controlling sensitivity in photothermal spectroscopy, in particular, photoacoustic spectroscopy and probe-beam deflection spectroscopy. Wc consider the physical basis for signal generation and enhancement methods for pulsed and continuous-modulated excitations as well as the various sources of noises which become significant when the absorption approaches the part-per-million level or below. Proper signal enhancement and noise suppression are essential to make photothermal spectroscopy a sensitive tool.
01 Mar 1992
TL;DR: In this paper, the authors considered the possibilities of using lasers based on rare isotopic species of carbon dioxide to detect trace quantities of pollutants in ambient air by photoacoustic spectroscopy (PA).
Abstract: This paper considers the possibilities of using lasers based on rare isotopic species of carbon dioxide to detect trace quantities of pollutants in ambient air by photoacoustic spectroscopy (PA). The use of isotopic CO2-laser lines allows to overcome the background absorption of atmospheric carbon dioxide. The effect of water vapor continuum absorption is eliminated by decreasing the gas pressure in the PA cell. The spectroscopic analysis performed within the framework of GEISA-84. Database shows that even at a 10%-measurement error detection sensitivities of 0.1–10 ppbV for NH3, C2H4, O3, HNO3, PH3 and ClO in ambient air can be achieved. A simple PA gas analyzer on the basis of a 13C16O2-laser with a NH3 sensitivity of ≠1 ppbV and a time resolution of 1.5 min is also described.
01 Jan 1992
TL;DR: In recent years, the development of many new techniques such as: dual-wavelength spectroscopy and dual-antenna spectrograms have attracted great interest as discussed by the authors, which quickly awakened great interest.
Abstract: In recent years we have seen the development of many new techniques such as:
Dual-wavelength spectroscopy,
derivative spectroscopy,
reflection spectroscopy,
photoacoustic spectroscopy,
luminescence-excitation spectroscopy,
variable wavelength detectors for chromatography and enzyme kinetics
all of which quickly awakened great interest.
TL;DR: In this article, a photoacoustic technique for measuring very low optical absorption in crystals and glasses is described, which does not use a high power laser pulse to excite an acoustic signal in the sample, but instead uses a continuous laser with the beam modulated at an acoustic resonance frequency of the sample.
Abstract: In this paper, a new photoacoustic technique is described for measuring very low optical absorption in crystals and glasses. The technique differs from the conventional photoacoustic technique in that it does not use a high‐power laser pulse to excite an acoustic signal in the sample, but instead uses a continuous laser with the beam modulated at an acoustic resonance frequency of the sample. By exciting the sample at resonance, the acoustic signal is enhanced by a factor proportional to the quality factor (Q) of the resonance. Because highly transparent crystals and glasses may have a Q on the order of 104 to 106, the technique is orders of magnitude more sensitive than conventional techniques. The Q is enhanced through the use of noncontact acoustic transducers, which also eliminate the problem of background signals due to scattered light. Measurements with various quartz samples have been used to verify the technique. Using a 10‐W continuous laser, the noise level of the resonant photoacoustic techniqu...
TL;DR: A photoacoustic gas spectrometer using a waveguide CO(2), laser, tunable over 500-MHz windows in 70 lines, was used for mapping Doppler-limited spectral signatures of ethylene and for measuring pressure-broadening rates for collisions with N(2, Ar, and He.
Abstract: A photoacoustic gas spectrometer using a wave-guide CO(2), laser, tunable over 500-MHz windows in 70 lines, is described. The spectrometer is used for mapping Doppler-limited spectral signatures of ethylene and for measuring pressure-broadening rates for collisions with N(2), Ar, and He. A total of 41 observed transitions are assigned to the nu(7), nu(10), and nu(4) bands of normal ethylene and to the nu(7) band of the (13)C(12)CH(4) isotopomer.
TL;DR: In this paper, photoacoustic absorption signatures have been obtained for ozone in 450-MHz tuning windows of a waveguide CO 2 laser for the ν 1 and ν 3 bands.
TL;DR: In this article, Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) was used for the studies of oxidation and degradation in various textile fabrics.
Abstract: Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) was used for the studies of oxidation and degradation in various textile fabrics. All the infrared spectroscopic data demonstrate that FT-IR/PAS is able to differentiate the near surface of a textile sample from its bulk. Therefore, it can be used to determine the distribution of degradation products between the near surfaces of fabrics and their bulk. FT-IR/PAS apperas to be reliable qualitative analytical technique for textile samples and does not suffer band distorsion found in diffuse reflectance infrared spectra of some textile samples
TL;DR: In this article, a simple photoacoustic configuration that eliminates the spurious window and external background signals and enhances the main (real) signal of IR gaseous photo-acoustic systems, optimizing the signal-to-noise ratio, is presented.
01 Apr 1992
TL;DR: In this article, a model is developed to describe the effect of fluorescence quenching on photoacoustic signals, taking advantage of the time resolution in pulsed-laser photoacoustics.
Abstract: The development of deconvolution techniques in pulsed-laser, time-resolved photoacoustics has opened the possibility of accurately distinguishing between processes occurring on different time scales, and has given photoacoustics better resolution in determining reaction enthalpies and quantum yields. While fluorescent signals are usually generated by a single de- excitation pathway in the fluorophore, photoacoustic signals usually arise from different sources, such as excited singlet and triplet deactivation, occurring on well-distinguished time scales. The understanding of the effect of quenching on photoacoustic signals therefore requires careful analysis of the data. In this work, a model is developed to describe the effect of fluorescence quenching on photoacoustic signals. The model takes advantage of the time resolution in pulsed-laser photoacoustics. Both static and dynamic quenching are taken into account. Important photophysical parameters (fluorescence and intersystem crossing quantum yields, the bimolecular quenching rate constant, and the volume of the sphere of action) appear in the expressions describing the dependence of photoacoustic signal on quencher concentration. Data from both steady-state fluorescence and time-resolved photoacoustic quenching measurements are analyzed simultaneously using a set of equations containing common parameters. Experimental data on the quenching of organic dyes are presented which support the validity of the model.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this article, photoacoustic spectroscopy (PAS) and DRS were investigated for the quantification of silica using the IR bands at 1080, 797, 693, and 1875 cm−1.
Abstract: The techniques of photoacoustic spectroscopy (PAS) and diffuse reflectance spectroscopy (DRS) are investigated for the quantification of silica using the IR bands at 1080, 797, 693, and 1875 cm−1. It is observed that, in both techniques, signal intensity increases linearly with mass initially. However, signal saturation sets in at much lower masses (>2 mg) in PAS than in DRS (>30 mg), showing that saturation is strongly technique dependent, in addition to having dependence on the absorptivity of the sample. These findings are applied to the quantification of silica in laboratory-generated silica-kaolin mixtures. It is shown that, with the use of the weaker band at 1875 cm−1 in DRS, satisfactory results for the quantification of silica are obtained.
TL;DR: The HNO radical's spectrum has been recorded in the 740-770 nm range via a high resolution, intracavity photoacoustic technique as discussed by the authors, where hydrogen peroxide and diethylene triamine reacted to produce a steady state concentration of HNO within the photo-acoustic cell that was detectable for several hours before the reactants were depleted.
01 Jan 1992
TL;DR: In this article, the use of step-scan Fourier transform infrared (FT-IR) spectroscopy combined with pholoacoustic (PA) detection is used to depth profile laminated polymeric materials.
Abstract: The use of step-scan Fourier transform infrared (FT-IR) spectroscopy combined with pholoacoustic (PA) detection is used to depth profile laminated polymeric materials. Depth profiling can be performed using a combination of the modulation frequency dependence and phase lag of the PA signal.
01 Jan 1992
TL;DR: The current status and capabilities of FTIR PAS arc are discussed in this paper, including historical background, signal generation, FTIR spectrometer and photoacoustic detector technology and use.
Abstract: The current status and capabilities of FTIR PAS arc discussed including historical background, signal generation, FTIR spectrometer and photoacoustic detector technology and use, and qualitative and quantitative applications that demonstrate the state-of-the-art analytical capabilities of the technique.
TL;DR: In this article, the interaction of gamma-iron oxide powder with several substances (silica, stearic acid, Stearylamine, and polyurethane resin) was investigated with the use of Fourier transform infrared photoacoustic spectroscopy.
Abstract: The interaction of gamma-iron oxide powder with several substances (silica, stearic acid, stearylamine, and polyurethane resin) was investigated with the use of Fourier transform infrared photoacoustic spectroscopy. The stearic acid was found to be chemisorbed onto the gammairon oxide surface through the carboxyl group and then dissociated the proton of the carboxyl group. It was also suggested that the stearylamine was chemisorbed onto the surface of the gamma-iron oxides through the NH2 group. In the case of polyurethane, a lower shift of the C=O stretching band and a decreasing of the relative absorption intensity of the NH deformation band were observed, indicating that a chemical interaction between the polyurethane resin and the oxides had occurred. The adsorption sites of these substances on the gamma-iron oxide were also considered.
TL;DR: In this article, a photoacoustic spectroscope was used to study the structure of a silica gel-immobilized diacetamide and showed that it is octahedrally coordinated with a strong tetragonal distortion.
TL;DR: Because the coloured complex was desorbed from the cell with a desorbing agent solution, the present method could afford repeated analyses of natural water samples containing iron at ng/ml levels without any preconcentration procedures.
TL;DR: In this article, the authors used the PA spectroscopic technique to characterize the deep levels in semiconductors, and showed that a distinctive peak at 0.92 eV and a hump near 1.2 eV have been observed for the SI samples.
Abstract: Piezoelectric photoacoustic measurements on semi-insulating (SI) and n-type GaAs were carried out at 90 K. A distinctive peak at 0.92 eV and a hump near 1.2 eV have been observed for the SI samples. By comparing with the optical absorption and the electron photoionization cross section spectra, it is considered that these features are due to the electron transition involving deep EL2 defect levels. The present experimental results show that the PA spectroscopic technique is a novel and a useful tool to characterize the deep levels in semiconductors.
TL;DR: The photoacoustic spectra of uranium(V) in powdered samples have been measured and assigned on the basis of both the time-course of the spectra and comparison with the absorption spectrum of photochemically or electrochemically reduced uranyl ions in solution.