Showing papers on "Photoacoustic spectroscopy published in 1980"
TL;DR: In this article, a theory of optical beam deflection near a heated surface was introduced as a method of photothermal spectroscopy and applied to the measurement of thermal diffusivity of gases.
Abstract: Optical beam deflection near a heated surface was recently introduced as a method of photothermal spectroscopy. Photothermal spectroscopy (PTS) is closely related to photoacoustic spectroscopy (PAS) in its ability to measure optical properties of opaque solids and liquids. This paper develops a theory of this effect and compares this theory with extensive experimental observations. Both are in excellent agreement. The relationship between this form of PTS and PAS is explicitly developed. Applications to the measurement of thermal diffusivity of gases is described.
313 citations
TL;DR: In this article, the theory of piezoelectric photoacoustic spectroscopy for condensed-matter samples is developed for condensedmatter samples, treating the sample as an elastic layer and neglecting the transducers effect on the sample, the three-dimensional uncoupled quasistatic thermoelastic equations are solved using a Green's function for the stress.
Abstract: The theory of piezoelectric photoacoustic spectroscopy is developed for condensed‐matter samples. Treating the sample as an elastic layer and neglecting the transducer’s effect on the sample, the three‐dimensional uncoupled quasistatic thermoelastic equations are solved using a Green’s function for the stress. An expression for the dependence of the signal on absorption, modulation frequency, thermal properties, and mechanical properties of the sample is derived. The theoretical predictions are experimentally verified, the sources of noise are analyzed, and the noise equivalent power is estimated. Finally, considerations for detector optimization are discussed.
296 citations
TL;DR: In this paper, a simplified model based on the Rosencwaig and Gersho theory of the photoacoustic effect is presented, which applies to thermally thick samples and is compared to the experimental results for a wide range of very or moderately absorbing materials.
Abstract: Based upon the Rosencwaig and Gersho theory of the photoacoustic effect, a simplified model, which applies to thermally thick samples, is presented. The theoretical variations of the modulus and of the phase of the photoacoustic signal are compared to the experimental results for a wide range of very or moderately absorbing materials. The variations of the tangent of the phase with regard to the wavelength reproduce an absorption spectrum turning the photoacoustic spectroscopy into a quantitative technique.
117 citations
TL;DR: In this paper, the Rosencwaig-Gersho theory for the photoacoustic signal from a homogeneous solid has been extended to include effects of a coating layer with different thermal and optical properties than the substrate.
Abstract: The Rosencwaig‐Gersho theory for the photoacoustic signal from a homogeneous solid has been extended to include effects of a coating layer with different thermal and optical properties than the substrate. The cases treated include one with an optically transparent coating and one with appreciable optical absorption.
78 citations
76 citations
TL;DR: Findings indicate that under the last conditions there is an unsuspected photoactivity of PS I which was not detected hitherto by the conventional techniques, and the dependence on the background light intensity confirms this result.
74 citations
TL;DR: In this paper, a single-beam, computer-controlled spectrometer fitted with a broad-band source and LiF and CaF2 prisms was used for IR-photoacoustic spectroscopy of organic solids.
Abstract: Infrared photoacoustic spectra were recorded over the 3900 to 1400 cm-1 range with a single-beam, computer-controlled spectrometer fitted with a broad-band source and LiF and CaF2 prisms. The exploratory results indicate that structured IR spectra of organic solids can be obtained. Various surface treatments were used to alter the chemical composition of the surfaces of samples composed of thick catalyst pellets and of thick beds of powdered silica and alumina, under controlled conditions in a reactor attached to the acoustic cell. The IR bands of resulting surface species were observable at sub-monolayer coverages. With some improvements, IR-photoacoustic spectroscopy will be a useful ancillary technique especially suited for studying surface species on thick adsorbents, catalysts, and corrosion layers.
69 citations
TL;DR: In this article, the influence of light scattering on photoacoustic signals is treated and the theoretical and experimental results are compared based on a model in which the photons diffuse through the sample.
Abstract: The influence of light scattering on photoacoustic signals is treated. Theoretical and experimental results are compared. The theoretical results are based on a model in which the photons diffuse through the sample. An equation governing the diffusion process is solved with appropriate boundary conditions. This gives the distribution of photons in the sample. The photoacoustic signal is then calculated and the result is compared with the result for nonscattering samples, giving the influence of the light scattering. The experimental results are obtained by measuring the photoacoustic signal for both scattering and nonscattering samples. The experimental and theoretical results are in good agreement. The differences are mainly due to the incompleteness of the original diffusion theory. An improved theory incorporating internal reflection at the sample surface is also analyzed. The paper illustrates the effects of light scattering on photoacoustic signals. It also shows how to estimate theoretically the photoacoustic signal from a light‐scattering sample.
69 citations
65 citations
TL;DR: The photoacoustic effect is the basis for photo-acoustic spectroscopy, a rapidly developing technique for studying optical absorption in many solid and liquid samples which are difficult to study by conventional means as mentioned in this paper.
Abstract: The photoacoustic effect is the basis for photoacoustic spectroscopy, a rapidly developing technique for studying optical absorption in many solid and liquid samples which are difficult to study by conventional means. Understanding of the effect requires knowledge of both acoustic and thermal waves, making this an interesting problem in the application of fundamental wave concepts and techniques. Both qualitative and quantitative discussions are presented for use as classroom examples at various levels.
64 citations
TL;DR: In this paper, a method for determining the absolute absorption coefficient of condensed samples is presented. But this method is not applicable to the case of ion electrophoresis in aqueous solutions.
Abstract: In order to perform quantitative photoacoustic spectroscopy (PAS) it is desirable to have a method of obtaining the absolute absorption coefficient of a sample from PAS measurements alone. The photoacoustic signal contains both amplitude and phase data and this paper discusses a method by which this information may be used to determine the absolute absorption coefficient of condensed samples. Experimental results on ions in aqueous solution are also presented.
TL;DR: In this article, a wide selection of infrared absorption spectra of opaque samples is presented to show the versatility of Fourier-transformed infrared photoacoustic spectroscopy, and a method for correcting these spectra for incident radiant power variations with respect to wavelength is also demonstrated.
Abstract: A wide selection of infrared absorption spectra of opaque samples is presented to show the versatility of Fourier-transformed infrared photoacoustic spectroscopy. A method for correcting these spectra for incident radiant power variations with respect to wavelength is also demonstrated.
TL;DR: In this article, the application of the newly developed technique of photoacoustic infrared spectroscopy, using a Fourier transform infrared spectrometer, to the measurement of the infrared spectra of single slabs of various coal types is described.
Abstract: The application of the newly developed technique of photoacoustic infrared spectroscopy, using a Fourier transform infrared spectrometer, to the measurement of the infrared spectra of single slabs of various coal types is described. The effects of aging of coal surfaces, which include both oxidation and abrasion, are clearly apparent in a comparison of the spectra of freshly cleaved and aged coal surfaces.
TL;DR: Fourier transform infrared photoacoustic techniques have been employed to remove the spectral distortion present in the transmission and reflectance spectra of powdered solids suspended in mulls and pressed pellets as discussed by the authors.
Abstract: Fourier transform infrared photoacoustic techniques have been employed to remove the spectral distortion present in the transmission and reflectance spectra of powdered solids suspended in mulls and pressed pellets. Results are presented for AgCN. The photoacoustic data is also compared to that obtained by Raman spectroscopy.
TL;DR: In this article, the photoacoustic spectrum of a sample is compared to the emission spectrum of the source measured directly with, say, a photocell, power meter, or photodiode.
Abstract: Photoacoustic spectra of solids1 are usually “source compensated,” i. e., normalized for differences in source emission at different wavelengths, and such compensation is done by comparing the photoacoustic spectrum of a sample to the emission spectrum of the source measured directly with, say, a photocell,2 power meter,3 or photodiode,4 or to the photoacoustic spectrum of “carbon” recorded under the same conditions as that of the sample. A variety of carbons has been used for this purpose, including carbon black on silica,5 soot from a gas torch,6 and acatylene-sooted bakelite,7 such a reference substance being assumed to be a flat black absorber. That assumption appears to be valid, as indicated by the close
TL;DR: In this article, it was shown that the one-dimensional theories of the photoacoustic effect in solids are still applicable when the heat flow is three dimensional, provided that the thermal diffusion length in the gas is much less than the radius of the sample chamber.
Abstract: It is demonstrated both theoretically and experimentally that the one‐dimensional theories of the photoacoustic effect in solids are still applicable when the heat flow is three dimensional, provided that the thermal diffusion length in the gas is much less than the radius of the sample chamber.
TL;DR: In this paper, Malpas et al. used a piezoelectric detector and photoacoustic spectroscopy of electrodes for the monitoring of electrochromic systems, and the results showed that the detector was able to achieve state-of-the-art performance.
Abstract: Analytical Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 In situ monitoring of electrochromic systems by piezoelectric detector photoacoustic spectroscopy of electrodes Richard E. Malpas, and Allen J. Bard Anal. Chem., 1980, 52 (1), 109-112• DOI: 10.1021/ac50051a026 • Publication Date (Web): 01 May 2002 Downloaded from http://pubs.acs.org on February 13, 2009
TL;DR: In this article, laser photoacoustic spectroscopy measurements were made on Nd3 + ions in garnet, vanadate, and pentaphosphate host crystals, indicating that the mechanisms for generating heat have different characteristics in these two types of samples.
Abstract: Laser photoacoustic spectroscopy measurements were made on Nd3 + ions in garnet, vanadate, and pentaphosphate host crystals. The variations of signal intensities with chopping frequency of the incident light are not in agreement with the predictions of standard photoacoustic signal generation theory. The results are distinctly different for concentrated and dilute Nd-doped crystals, indicating that the mechanisms for generating heat have different characteristics in these two types of samples. The determination of radiative quantum efficiencies of these materials by photoacoustic spectroscopy techniques is also described. These results are compared with those obtained by other methods.
TL;DR: Cross-section data are important for the assessment of the capability of CO(2) laser-based spectroscopic techniques for monitoring low levels of hydrazine-fuel vapors in the ambient air.
Abstract: Absorption cross-section data are reported for the toxic rocket fuels hydrazine, monomethylhydrazine, and unsymmetrical dimethylhydrazine (UDMH), as well as for their selected air oxidation products dimethylamine, trimethylamine, and methanol at up to seventy-eight CO(2) laser wavelengths each. These data are important for the assessment of the capability of CO(2) laser-based spectroscopic techniques for monitoring low levels of hydrazine-fuel vapors in the ambient air. Interference-free detection sensitivities of <30 ppb have been demonstrated for UDMH using a laboratory photoacoustic detection system.
TL;DR: In this article, the degree of surface coverage on chemically modified silica gel was determined by using photoacoustic spectroscopy, and a linear relationship between signal amplitude and carbon or nitrogen content on the chemically modified surface was obtained.
TL;DR: In this paper, the detection of electron paramagnetic resonance absorption has been achieved using techniques similar to those used in the photoacoustic spectroscopy of solids, such as magnetic field and amplitude modulation.
Abstract: The detection of electron paramagnetic resonance absorption has been achieved using techniques similar to those used in the photoacoustic spectroscopy of solids. Magnetic field and amplitude modulation have been used in both resonant and nonresonant microwave spectrometers.
TL;DR: In this article, a theoretical model for photoacoustic response of a condensed sample with a two-level optical absorption band is presented and the nonradiative lifetime of the excited state and the transfer function of the pressure transducer are included in the formalism.
Abstract: A theoretical model is presented for the time‐domain photoacoustic response of a condensed sample with a two‐level optical‐absorption band. The nonradiative lifetime of the excited state and the transfer function of the pressure transducer are included in the formalism. The limitations of the technique for nonradiative lifetime measurements are discussed and the experimental conditions necessary for optimum relaxation time determinations are evaluated. It is found that the limitations imposed by the modified gas thermal transport equations used in the model restrict it to relaxation times greater than ∼10−5 sec. This is of the same order as the limit imposed on experimental measurements by the transfer function of commercial microphones.
TL;DR: In this article, a Michelson interferometer with step-and-integrate mirror motion is described for use in Fourier transform photoacoustic spectrometry (FTPAS) at visible wavelengths.
Abstract: A Michelson interferometer with step‐and‐integrate mirror motion is described for use in Fourier transform photoacoustic spectrometry (FTPAS) at visible wavelengths. An overview of mechanical and software construction is supplied and the advantages of FTPAS are illustrated with a spectrum of powdered erbium oxide at visible wavelengths. The relative merits of step‐and‐integrate and rapid scan mirror motion for FTPAS are considered.
TL;DR: The sensitivity of photoacoustic Raman spectroscopy (PARS) has been improved substantially by the use of high peak-power pulsed lasers as discussed by the authors, and applications of PARS are discussed, and a comparison is made with other Raman techniques.
Abstract: The sensitivity of a new spectroscopic technique, photoacoustic Raman spectroscopy (PARS), has been improved substantially by the use of high‐peak‐power pulsed lasers. The theory for generation of photoacoustic signals from stimulated Raman scattering is outlined, and vibration‐rotation Raman spectra for CO2 and CH4 are presented. Applications of PARS are discussed, and a comparison is made with other Raman techniques.
TL;DR: In this paper, the use of the photoacoustic spectroscopy (PAS) technique to measure nonradiative lifetimes in either the frequency or time-domain mode is discussed.
Abstract: The use of the photoacoustic spectroscopy (PAS) technique to measure nonradiative lifetimes in either the frequency or time-domain mode is discussed. Expressions are presented for the dependence of the cell pressure upon the lifetime, and the modifications introduced by the microphone transfer function are discussed. It is shown that in both measurement modes thermally and optically thick specimens are preferred. Other sample types have contributions to the measured phase or time delay arising from the optical absorption depth and sample cell parameters. The model presented suggests that the PAS technique is suitable for the measurement of lifetimes in the range between 10−5 and 10−1 s, with the limits arising from the microphone transfer function, the finite sound velocity, and thermal transport velocity in the transducer gas.
TL;DR: In this paper, photoacoustic spectroscopy was used to investigate nonradiative states in GaAs and InP and found that the PA signal intensity in InP at the band edge is much smaller than that of GaAs.
Abstract: Nonradiative states in GaAs and InP are investigated by photoacoustic spectroscopy. InGaAs, we observed (1) an increase of photoacoustic (PA) signals with a decrease of photoluminescence (PL), (2) a PA signal due to nonradiative states near the crystal surface, and (3) a PA signal due to nonradiative states in the bulk which act as absorption levels of PL. We found that the PA signal intensity in InP at the band edge is much smaller than that of GaAs.
TL;DR: The photoacoustic spectra of hemin, hemoglobin, protoporphyrin IX, and horseradish peroxidase show how this technique can be used to obtain structural information about biological materials which cannot readily be studied by normal transmission infrared spectroscopy.
Abstract: A new technique for measuring the infrared spectra of solids has been developed. The photoacoustic spectra of hemin, hemoglobin, protoporphyrin IX, and horseradish peroxidase show how this technique can be used to obtain structural information about biological materials which cannot readily be studied by normal transmission infrared spectroscopy. The method requires milligram quantities of material and involves no sample preparation.
TL;DR: Fourier transform photoacoustic spectroscopy (FTPAS) can be carried out in the visible using either a piezoelectric crystal or a microphone to detect the interferogram produced in a sample when the latter is illuminated by white light passed through a Michelson interferometer as discussed by the authors.
Abstract: Fourier transform photoacoustic spectroscopy (FTPAS) can be carried out in the visible using either a piezoelectric crystal or a microphone to detect the interferogram produced in a sample when the latter is illuminated by white light passed through a Michelson interferometer. Spectra of lanthanide oxides and whole human blood are reported that illustrate benefits and limitations of visible FTPAS.