Second International Meeting on Photoacoustic Spectroscopy最新文献

{"title":"Signal Enhancement in Photothermal Imaging Produced by Three Dimensional Heat Flow","authors":"J. Murphy, L. Aamodt","doi":"10.1063/1.92800","DOIUrl":"https://doi.org/10.1063/1.92800","url":null,"abstract":"The development of photoacoustic microscopy (SPAM)(1,2) has provided a means of studying the surface and subsurface features of solids including subsurface voids or layer disbonding which modify the efficiency of thermal diffusion into the sample. We have recently introduced a new method of thermal imaging(2) which shares some of the features of SPAM but, rather than acoustic detection, uses the \"mirage effect\"(4) or deflection of an optical probe beam to determine the sample surface temperature distribution.(5) A theory of photothermal imaging has recently been developed for homogeneous samples(6) (i.e., samples containing no thermal diffusion boundaries important to the experiment). This development includes a full treatment of 3-dimensional diffusion in the sample and the gas. The theoretical results are in good agreement with those obtained experimentally.","PeriodicalId":202661,"journal":{"name":"Second International Meeting on Photoacoustic Spectroscopy","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1981-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123620018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Scattering Contribution to Photoacoustic Signal","authors":"Z. Yasa, W. Jackson, N. Amer","doi":"10.1364/pas.1981.ma2","DOIUrl":"https://doi.org/10.1364/pas.1981.ma2","url":null,"abstract":"Insensitivity to scattering has generally been accepted as an inherent characteristic of photoacoustic detection. The physical reasoning underlying this assumption has been that the photoacoustic signal arises from the heat generated following optical absorption, and thereby is a measure of the cross section of such absorption. However, the thermal energy generated by the absorption of light is a function of the intensity distribution within the sample, which depends on its scattering characteristics. Consequently, deviation from Beer's Law should, in principle, affect the thermal signal generated. We will show that for highly scattering media, the photoacoustic signal is strongly dependent on the scattering parameters. On the other hand, for optically thin solids and liquids the photoacoustic signal is insensitive to light scattering up to a scattering coefficient (λα) of ~1/ℓ where ℓ is the sample thickness, λ is the fraction of light scattered, and α is the total attenuation coefficient of a coherent beam.","PeriodicalId":202661,"journal":{"name":"Second International Meeting on Photoacoustic Spectroscopy","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1981-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131288688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New Aspects of Buffer Gas Effects in Resonant Spectrophones","authors":"R. Johnson, L. J. Thomas, R. Gerlach, N. Amer","doi":"10.1364/pas.1981.tua5","DOIUrl":"https://doi.org/10.1364/pas.1981.tua5","url":null,"abstract":"In studies of gas phase photoacoustic spectroscopy, the gas whose spectrum is being investigated is generally one of several present in the sample, and often only in trace amounts. The response of the spectrophone is determined by the characteristics of the sample gas as a whole, and depends on the various thermal and molecular relaxational properties of the gases present. In particular, for an acoustically resonant spectrophone, important characteristics will include the sound velocity, heat capacity, thermal conductivity, viscosity, and the energies and relaxation times of the molecular vibrations. The sound velocity determines the resonant frequencies of the cavity, while the other parameters govern the loss mechanisms that determine the quality factors of the resonances, and also cause small shifts in the resonant frequencies. In an earlier study,1 the resonant frequencies and quality factors of acoustical resonances were determined for various buffer gases at atmospheric pressure, and the results were compared to theoretical predictions2 based on classical surface viscous and thermal losses. Significant discrepancies were observed for all non-noble gases.3 It is the goal of this work to investigate the pressure dependent behavior of the spectrophone, and to incorporate molecular relaxation effects into the theoretical interpretation of that behavior. We have made a number of extensions and improvements in experimental and analytical technique. The spectrophone used was a stainless steel cylinder polished to a 1/3 micron surface finish to guarantee well defined boundary layers whose losses could be calculated accurately from theory. The spectrophone and vacuum system were bakeable to reduce impurity effects due to outgassing. Whereas in the earlier experiment a large concentration of the optically absorbing component (9000 ppm of CH4) was used, we kept the absorber concentration small (50 ppm of C2H4) so as not to disturb the properties of the buffer gas. Use of an electro-optic modulator system allowed access to modes at much higher frequencies, thus enabling the study of lighter gases. We have measured the resonant frequency and quality factor as a function of pressure from atmopsheric pressure down to 10 torr or lower for each buffer gas. Data analysis consisted largely of nonlinear least squares curve fitting of the resonant response curves, which gave more accurate determinations of the resonant frequency and Q than the half power point method used in the previous experiment.","PeriodicalId":202661,"journal":{"name":"Second International Meeting on Photoacoustic Spectroscopy","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1981-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117133446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Absorption Spectra of Crystalline and Amorphous Silicon by Photothermal Deflection Spectroscopy","authors":"W. Jackson, N. Amer, D. Fournier, A. Boccara","doi":"10.1364/pas.1981.wa3","DOIUrl":"https://doi.org/10.1364/pas.1981.wa3","url":null,"abstract":"The nature of the optical absorption in semiconductors at and below the absorption edge is of interest, particularly in the case of amorphous materials. The sensitivity of conventional transmission techniques are limited by the requirement of measuring the difference between two nearly equal signals. Furthermore, such techniques are highly sensitive to scattering. While adequately sensitive, the disadvantages of piezoelectric photoacoustic detection(1) are that it requires a laser as the exciting source, is highly sensitive to scattering, and requires reliable coupling between the transducer and the sample.","PeriodicalId":202661,"journal":{"name":"Second International Meeting on Photoacoustic Spectroscopy","volume":"122 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1981-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115764374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Photo Displacement Imaging","authors":"S. Ameri, E. Ash, V. Neuman, C. R. Petts","doi":"10.1049/EL:19810238","DOIUrl":"https://doi.org/10.1049/EL:19810238","url":null,"abstract":"The renaissance of photo-acoustic spectroscopy {1} has recently led to several novel forms of imaging. Common to all of these is the use of a modulated laser (or electron) beam which is partially absorbed by the object to be imaged. The energy from the incident beam is transformed, with varying degrees of efficiency, into thermal energy giving rise to stress waves within the object, producing pressure changes in the adjacent air, and I.R. radiation from the object. All of these effects have been successfully used as the basis of imaging systems, {2, 3, 4}.","PeriodicalId":202661,"journal":{"name":"Second International Meeting on Photoacoustic Spectroscopy","volume":"112 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1981-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124812958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Discussion of Particle Size Effects in Photoacoustic Spectroscopy","authors":"C. Ashworth, S. Castleden, G. Kirkbright, D. Spillane","doi":"10.1364/pas.1981.tub1","DOIUrl":"https://doi.org/10.1364/pas.1981.tub1","url":null,"abstract":"For some time the particle size of the sample has been noticed to affect the magnitude and quality of the photoacoustic signal observed (1,2,3). These effects have become increasingly significant as attempts have been made to obtain quantitative results in applying photoacoustic spectroscopy to the analysis of real samples. It can be demonstrated easily that a sample containing a wide range of particle size produces a photoacoustic signal with a significantly worse signal-to-noise ratio than does a sample containing only a narrow range of particle size.","PeriodicalId":202661,"journal":{"name":"Second International Meeting on Photoacoustic Spectroscopy","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115181314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evidence for Thermal Wave Interference in Thin Particulate Carbon Samples","authors":"C. A. Bennett, R. Patty","doi":"10.1364/pas.1981.tub2","DOIUrl":"https://doi.org/10.1364/pas.1981.tub2","url":null,"abstract":"It is well known that thermal wave interference will affect the photoacoustic signal arising from very thin samples; (1,2) in this report we present experimental evidence for thermal wave interference effects in thin layers of elemental carbon particles which have been deposited on three commonly used filter substrates. Not only are these results important to our present objectives concerning the calibration of an ambient soot monitor, they may be of significance to those engaged in a photoacoustic study of samples which are less than a thermal wavelength in thickness.","PeriodicalId":202661,"journal":{"name":"Second International Meeting on Photoacoustic Spectroscopy","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122299488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Physics of Signal Production in Enclosed-Cell Photoacoustic Spectroscopy of Condensed Matter","authors":"F. A. McDonald, G. Wetsel","doi":"10.1364/pas.1981.ma1","DOIUrl":"https://doi.org/10.1364/pas.1981.ma1","url":null,"abstract":"Much interest has been shown in recent years in the application of the photoacoustic effect to the spectroscopy of condensed matter using the enclosed-cell, microphone-detection (ECMD) configuration. This paper is concerned with: (1) a review of what is known about the photoacoustic effect in condensed matter from a theoretical perspective, and (2) consideration of the extent to which theory has been experimentally verified.","PeriodicalId":202661,"journal":{"name":"Second International Meeting on Photoacoustic Spectroscopy","volume":"103 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114102869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Photoisomerisation of DODCI Studied by Photoacoustic Spectroscopy","authors":"S. Schneider, U. Möller, H. Coufal","doi":"10.1007/978-3-663-06820-4_25","DOIUrl":"https://doi.org/10.1007/978-3-663-06820-4_25","url":null,"abstract":"","PeriodicalId":202661,"journal":{"name":"Second International Meeting on Photoacoustic Spectroscopy","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126387692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Applications of resonant photoacoustic spectroscopy","authors":"J. Röper, K. Frank, P. Hess","doi":"10.1007/978-3-663-06820-4_10","DOIUrl":"https://doi.org/10.1007/978-3-663-06820-4_10","url":null,"abstract":"","PeriodicalId":202661,"journal":{"name":"Second International Meeting on Photoacoustic Spectroscopy","volume":"107 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132211547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}