Showing papers on "Photoacoustic spectroscopy published in 1977"
TL;DR: In this article, the dependence of photoacoustic spectrometer sensitivity on the physical dimensions of the sample cell was investigated for sizes larger than and smaller than the gas thermal diffusion length.
Abstract: The dependence of photoacoustic spectrometer sensitivity on the physical dimensions of the sample cell was investigated for sizes larger than and smaller than the gas thermal diffusion length. The results depend on the thermal properties of the gas and the sample in agreement with an extension of Parker’s theory of photoacoustic signal generation.
167 citations
TL;DR: In this article, photoacoustic spectroscopy (PAS) is applied to the study of nonradiative processes in luminescent systems and a rate-equation model is developed and applied to interpreting the observed concentration-dependent metastable-level quenching rates in ruby.
Abstract: Photoacoustic spectroscopy (PAS) is applied to the study of nonradiative processes in luminescent systems. A rate‐equation model for this process is developed and applied to interpreting the observed concentration‐dependent metastable‐level quenching rates in ruby. Successful PAS operation at 77°K is reported.
94 citations
TL;DR: In this paper, the frequency dependences of the acoustic stresses in the gas which arise from the surface and bulk absorption are derived, and expressions for the acoustic stress and phase shift which are valid for all frequencies are given.
Abstract: Researchers seek improved ways to measure separately the surface‐ and bulk‐absorption coefficients of highly transparent materials. The case in which a laser beam modulated at angular frequency ω passes through the weakly absorbing windows of a gas cell which contains a nonabsorbing gas is investigated in this paper. In particular, the frequency dependences of the acoustic stresses in the gas which arise from the surface and bulk absorption are derived. An intermediate range of frequencies exists for which the acoustic stress due to surface absorption varies as ω−1 and has a 90 ° phase shift relative to the modulated laser beam and for which the acoustic stress due to bulk absorption varies as ω−3/2 and has a 45 ° phase shift. In addition, expressions for the acoustic stress and phase shift which are valid for all frequencies are given. These expressions enable one to develop numerical procedures by which the surface‐ and bulk‐absorption coefficients may be determined separately. Numerical examples for a representative laser glass and air (nitrogen) are given.
59 citations
TL;DR: In this paper, a model based on the excited states of the 4f 7 configuration acting as a botleneck in the relaxation was proposed to explain the anomalously long relaxation rate from higher 4f 6 5d state of Eu 2+.
56 citations
49 citations
TL;DR: Gray et al. as discussed by the authors proposed a simple sample cell for examination of solids and liquids by photoacoustic spectroscopy, which can be used for image-based analysis of liquids and solids.
Abstract: Analytical Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Simple sample cell for examination of solids and liquids by photoacoustic spectroscopy Robert C. Gray, Victor A. Fishman, and Allen J. Bard Anal. Chem., 1977, 49 (6), 697-700• DOI: 10.1021/ac50014a009 • Publication Date (Web): 01 May 2002 Downloaded from http://pubs.acs.org on February 17, 2009
49 citations
TL;DR: In this article, a new device for absolute calibration of cells for photoacoustic spectroscopy is described, and experimental results for a particular cell are reported, where the absolute calibration is based on a specific cell type.
Abstract: A new device for the absolute calibration of cells for photoacoustic spectroscopy is described. Experimental results for a particular cell are reported.
27 citations
Patent•
04 Nov 1977TL;DR: In this article, a gas-filled photoacoustic cell can be used as a radiometer by adjusting the pulsed electrical energy, which can be made to relate to the pressure wave resulting from pulsed light in a predetermined manner.
Abstract: Pulsed light and readily measurable pulsed electrical energy are independently applied to a solid black, conductive sample in a gas-filled photoacoustic cell, each causing the black sample to heat. The heating of the black sample causes a pressure wave in the cell, which can be detected and measured. By adjusting the pulsed electrical energy, the pressure wave resulting from the pulsed electrical energy can be made to relate to the pressure wave resulting from the pulsed light in a predetermined manner. The pulsed light input intensity can then be measured in electrical units based on the measurable input of the electrical energy pulses. In this manner, the invention can be used as a radiometer. A second application for the present apparatus is in calibrating photoacoustic spectroscopy (PAS) cells. The PAS cell can be self-calibrated by discontinuing the light pulses and relating the pressure wave output to the electrical energy pulse input. The measurement then of light absorption in a test sample, which need be neither black nor conductive, can be made in absolute energy units based on the self-calibration relationship.
27 citations
TL;DR: Using a tunable CO 2 laser, the feasibility of photoacoustic spectroscopy on liquid and solid samples in the middle infrared was demonstrated in this paper, where a spectral feature, tentatively identified as the v 1 mode of SO 4, was observed in ammonium sulphate for the first time.
23 citations
TL;DR: The case in which a laser beam modulated at angular frequency omega passes through the weakly absorbing windows of a gas cell which contains a nonabsorbing gas is investigated and the frequency dependences of the acoustic stresses in the gas which arise from the surface and bulk absorption are derived.
Abstract: The case in which a laser beam modulated at angular frequency w passes through the weakly absorbing windows of a gas cell which contains a nonabsorbing gas is investigated in this paper. In particular, the frequency dependences of the acoustic stresses in the gas which arise from the surface and bulk absorption are derived. An intermediate range of frequencies exists for which the acoustic stress due to surface absorption varies approximately as ω−1 and has an approximate 90° phase shift relative to the modulated laser beam and for which the acoustic stress due to bulk absorption varies approximately as ω−3/2 and has an approximate 45° phase shift. Numerical examples for a representative laser glass and air (nitrogen) are given.
22 citations
TL;DR: This work has applied photoacoustic spectroscopy to the study of hydration and maturation of newborn rat stratum corneum and has obtained clean spectra in the 220 to 450 nm region indicative of a change in thermal diffusivity with increased hydration, and biochemical changes associated with the initial maturation period.
TL;DR: In this paper, the 500-800 nm spectra of replicata phytoplankton cultures freeze-dried upon glass fiber filters were determined both by photoacoustic spectroscopy (PAS) and by photoelectric absorption spectrophotometry.
Abstract: The 500–800 nm spectra of replicata phytoplankton cultures freeze-dried upon glass fiber filters were determined both by photoacoustic spectroscopy (PAS) and by photoelectric absorption spectrophotometry. A number of the features of biological interest are better resolved in the PAS spectra. Further, PAS is sufficiently sensitive that it could be applied in the analysis of readily obtainable field samples.
TL;DR: In this paper, photoacoustic spectroscopy was applied to the measurement of excited-state absorption spectra with nanosecond time resolution, and preliminary experimental results were reported.
Abstract: Preliminary experimental results are reported which demonstrate the application of photoacoustic spectroscopy to the measurement of excited‐state absorption spectra with nanosecond time resolution.
TL;DR: In this article, a small volume photoacoustic cell is described in which signal strengths of 400 mV can be achieved at irradiation levels of 35 mW at frequencies of 16 Hz and up.
Abstract: A small‐volume photoacoustic cell is described in which signal strengths of 400 mV can be achieved at irradiation levels of 35 mW. Thin samples produce a signal of near‐triangular waveform when the incident light is a square wave at frequencies of 16 Hz and up.
01 Jan 1977
01 Jan 1977
TL;DR: In this paper, the physical processes underlying the photoacoustic effect in solids, and a mathematical analysis of the production of the photo-acoustic signal are presented, as well as the methodology of photo acyclic spectroscopy and its application in physics, chemistry, biology, and medicine.
Abstract: There are a great many substances, both organic and inorganic, that, because of their physical state, cannot be readily studied by conventional absorption or reflection techniques. In photoacoustic spectroscopy, light absorbed by the sample is converted into a measurable acoustic signal, and spectra closely corresponding to optical absorption spectra, can be obtained on any type of solid or semisolid material, whether it be crystalline, powder, smear, gel, etc. The physical processes underlying the photoacoustic effect in solids, and a mathematical analysis of the production of the photoacoustic signal will be presented. The methodology of photoacoustic spectroscopy will also be described. Various applications of this technique in the fields of physics, chemistry, biology, and medicine will be discussed. These applications will be treated under three main headings: bulk studies, surface studies, and de‐excitation studies.
20 Sep 1977
TL;DR: The Aerospace Corporation under contract to the Law Enforcement Assistance Administration (LEAA) is supporting the development of a novel explosives-vapor detector based upon photoacoustic spectroscopy as mentioned in this paper.
Abstract: The Aerospace Corporation under contract to the Law Enforcement Assistance Administration (LEAA) is supporting the development of a novel explosives-vapor detector based upon photoacoustic spectroscopy. This paper reviews the principles and history of the method. The encouraging progress to date, obtained through subcontracted programs that characterized explosives vapors and environmental species and that measured photoacoustic absorption coefficients of selected explosives vapors and pollutants, is briefly described© (1977) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
01 Jan 1977
Journal Article•
TL;DR: In this article, the frequency dependences of the acoustic stresses in the gas which arise from the surface and bulk absorption are derived, and an intermediate range of frequencies exists for which the acoustic stress due to surface absorption varies approximately as omega(-1) and has an approximate 90 degrees phase shift relative to the modulated laser beam.
Abstract: The case in which a laser beam modulated at angular frequency omega passes through the weakly absorbing windows of a gas cell which contains a nonabsorbing gas is investigated in this paper. In particular, the frequency dependences of the acoustic stresses in the gas which arise from the surface and bulk absorption are derived. An intermediate range of frequencies exists for which the acoustic stress due to surface absorption varies approximately as omega(-1) and has an approximate 90 degrees phase shift relative to the modulated laser beam and for which the acoustic stress due to bulk absorption varies approximately as omega(-3/2) and has an approximate 45 degrees phase shift. Numerical examples for a representative laser glass and air (nitrogen) are given.
10 Apr 1977
TL;DR: Recently, photoacoustic spectroscopy has been developed which overcomes both of the above problems as mentioned in this paper, and some of its current applications are briefly described in this paper, however, they do not cover the application of this technique in the current paper.
Abstract: Conventional optical spectroscopy of solids, semisolids, smears, and gels generally suffers from excessive light-scattering and opacity effects. Recently a new spectroscopic technique, called photoacoustic spectroscopy has been developed which overcomes both of the above problems. This new technique and some of its current applications are briefly described in this paper.