Showing papers on "Photoacoustic spectroscopy published in 1994"
01 Jan 1994
TL;DR: Sigrist et al. as mentioned in this paper proposed the use of a Tunable Diode Laser Absorption Spectroscopy for Atmospheric Measurements (H. Schiff, et al.).
Abstract: Introduction to Environmental Sensing (M. Sigrist). Differential Optical Absorption Spectroscopy (DOAS) (U. Platt). Differential Absorption Lidar (DIAL) (S. Svanberg). Air Monitoring by Laser Photoacoustic Spectroscopy (M. Sigrist). The Use of Tunable Diode Laser Absorption Spectroscopy for Atmospheric Measurements (H. Schiff, et al.). Gas Measurement in the Fundamental Infrared Region (P. Hanst & S. Hanst). Matrix Isolation Spectroscopy in Atmospheric Chemistry (D. Griffith). Index.
581 citations
TL;DR: In this article, the band-gap energies of the CdS semiconductor are obtained by a photoacoustic spectroscopy (PAS) technique over a range of temperature of thermal annealing (TTA), in which the evolution of the sample structure is characterized by x-ray diffraction patterns.
Abstract: The band‐gap energies of the CdS semiconductor are obtained by a photoacoustic spectroscopy (PAS) technique over a range of temperature of thermal annealing (TTA), in which the evolution of the sample structure is characterized by x‐ray diffraction patterns. The PAS experiment gives a set of data for the band‐gap shift in the region of the fundamental absorption edge. With increasing TTA the band‐gap shift increases up to a critical TTA when its slope decreases in a roughly symmetrical way. It is suggested that at this temperature a cubic to hexagonal‐lattice transition occurs.
196 citations
TL;DR: Theoretical predictions and experimental measurements of photoac acoustic pulse production within a 0.5% solution of Liposyn suggest that photoacoustic ultrasound imaging may have application to biologic systems such as the human breast.
Abstract: Theoretical predictions and experimental measurements of photoacoustic pulse production within a 0.5% solution of Liposyn, a highly scattering, optical propagation medium, are reported. A simple model for photoacoustic energetics is developed that predicts photoacoustic signal pressure as a function of depth within a turbid medium following surface irradiation from an infrared source. The model is valid for very short irradiation duration. The model predicts that the acoustic pressure produced at a distance r from the center of a small, highly absorbing sphere of radius R consists of two, opposite polarity pulses, one originating from the near and one from the far side of the sphere. The magnitude of these biphasic pulses is expected to be proportional to the energy fluence (E) incident on the surface of the sphere and to the ratio, R/r. Furthermore, the energy fluence (E) that reaches the sphere is roughly proportional to e-mu effZ, where mu eff is the effective attenuation coefficient of the turbid medium and Z is the depth of the embedded sphere below the irradiated surface. The variation of E with depth within the absorber and biphasic acoustic pulse production have been verified experimentally. Further experiments demonstrate that a small (3-mm diameter), highly absorbing sphere can be detected and localized at a depth of 37.5 mm within a 0.5% solution of Liposyn with a spatial resolution of 1 x 6 mm2, using a biologically safe level of infrared irradiation (lambda = 1064 nm) and a conventional ultrasound transducer (frequency = 2.25 MHz). These results suggest that photoacoustic ultrasound imaging may have application to biologic systems such as the human breast.
107 citations
TL;DR: In this article, the volume changes occurring in a thin layer of photosynthetic suspension during the first microsecond following a monochromatic laser flash (3 ns duration) are detected by a piezoelectric ceramic.
57 citations
TL;DR: In this paper, a range of vibrational spectroscopic techniques are used to monitor supercritical fluid extraction and impregnation of polymers using an organometallic complex, CpMn(CO)3 (Cp = η5 − C5 H5) as a spectroscopy probe.
Abstract: A range of vibrational spectroscopic techniques are used to monitor supercritical fluid extraction and impregnation of polymers. Impregnation processes of this type show potential as alternative apporaches to the synthesis of polymer based catalysts and new materials. Methods have been devised using conventional Fourier transform infrared spectroscopy for real time monitoring of the extraction and impregnation of polyethylene films using an organometallic complex, CpMn(CO)3 (Cp = η5 − C5 H5) as a spectroscopic probe. Both low and high density powdered polyethylene may be impregnated using supercritical carbon dioxide. The resulting materials are analysed using FTIR photoacoustic spectroscopy, diffuse reflectance infrared spectroscopy and FT Raman spectroscopy to probe both the impregnated bulk of the polymer and surface-coated material. © 1994 John Wiley & Sons, Inc.
40 citations
32 citations
TL;DR: Time-resolved photoacoustic spectroscopy (TRPS) as discussed by the authors is one of the most powerful techniques in photobiophysics, provided that some limitations in data analysis and time resolution are removed by technical improvements.
Abstract: Acoustic waves generated by heat emission in radiationless transitions from photoexcited molecules can be detected by suitable transducers. Their study allows the investigation of thermal relaxations, thus providing thermodynamic and kinetic data on short-lived species produced by the absorption of pulses of light. In this field of research the best technique has proved to be the so-called pulsed-laser, time-resolved photoacoustic spectroscopy, which is based on piezoelectric detection of pressure waves in the time domain. Deconvolution processing of the transient signals gives both the lifetimes of excited states and the energy content of the transitions, provided that decay times are in the range 5 ns-5 μs. Moreover, when compared with proper theoretical models emphasizing the energy balance, the photoacoustic results can help to build a complete picture of the deactivation pathways, including photochemical events. The biophysical applications, although numerous and widespread both in basic and applied research, offer the real possibility of giving information on photobiological processes in conditions very close to the living state. Among the more significant contributions obtained in this area, the results on photosynthesis and photosensitivity of plants and photosynthetic micro-organisms, structural and functional dynamics of respiratory proteins, photocycles of rhodopsin and bacteriorhodopsin and photophysical properties of several natural pigments are particularly relevant, together with some medical and biotechnological applications. Another promising field of application of photoacoustics concerns photoactive drugs and the photophysics of fluorescent probes for conformational studies of proteins, nucleic acids and membranes. In general terms, time-resolved photoacoustic spectroscopy promises to become one of the most powerful techniques in photobiophysics, provided that some limitations in data analysis and time resolution are removed by technical improvements.
30 citations
TL;DR: In this paper, the solubility and speciation of plutonium (V) and plutonium(VI) in a pH = 6, 1.93 mM dissolved carbonate solution was measured to model the behavior of plutonium in a groundwater.
Abstract: The solubility and speciation of plutonium(V) and plutonium(VI) in a pH = 6, 1.93 mM dissolved carbonate solution was measured to model the behavior of plutonium in a groundwater. We studied the solubility from supersaturation and compared two methods for the determination of oxidation state distribution: an indirect chemical method using the extracting agents PMBP (4-benzoyl-3-methyl-l-phenyl-2-pyrazolin-5-one) and HDEHP (di-(2-ethylhexyl)-orthophosphoric acid), and direct measurement using laser photoacoustic spectroscopy. The plutonium(V) solution had a soluble plutonium concentration of 2.3 ± 2 X 10~ Μ over a time of 53 days and was greater than 95% PuOJ. Chemical extraction and spectroscopic results for the determination of PuOJ\" were in excellent agreement. Immediately after preparation of 1.9 to 3.7X10\"M PuO! solutions, some of the plutonium precipitates and a new soluble species forms, probably Pu02(0H). PuOJ forms within hours, and within a few days, becomes the dominant soluble species. After several months, only 1 2 % of the plutonium added initially remains in solution and it is essentially all Pu OJ. Chemical extraction and spectroscopic results for the determination of PuOi were in excellent agreement for two measurements and differed by 60% in a third determination.
30 citations
TL;DR: In this article, phase dispersion of the photothermal signal along with spectral linearization is used to access the extent of photoacoustic saturation in the photoacoustical spectra. And the effects of various data processing methods are examined.
Abstract: Rapid-scan- and step-scan-based Fourier transform infrared photoacoustic depth profiling results of an extracted but intact human tooth are compared. The effects of various data processing methods are examined. Analysis of the phase dispersion of the photothermal signal along with spectral linearization is used to access the extent of photoacoustic saturation in the photoacoustic spectra. Phase-modulated/phase-resolved depth profiling methods are less prone to photoacoustic saturation and provide superior localization of the surface and subsurface absorbers distributed in the tooth enamel. Mid-infrared depth profiling studies of calcified tissues can aid in the understanding of degenerative bone diseases, bone growth, and modeling, as well as tissue mineralization.
26 citations
TL;DR: In this article, the properties of amorphous GeSe thin films, which were evaporated on quartz substrata, were examined by measuring their amplitude and phase photoacoustic spectra as a function of the modulated optical laser beam frequency.
Abstract: In this work the possibility of simultaneous determination of thermal and transport properties of thin films using a photoacoustic method was investigated. The properties of amorphous GeSe thin films, which were evaporated on quartz substrata, were examined by measuring their amplitude and phase photoacoustic spectra as a function of the modulated optical laser beam frequency. The measurements were performed in a specially constructed photoacoustic cell which enabled excitation of the sample on one side and detection of the acoustic response on the other. Thermal diffusivity and transport properties (diffusivity coefficient, recombination time, and the surface recombination velocity) of the GeSe thin films were determined by comparing of the experimental results and the calculated theoretical photoacoustic spectra.
23 citations
TL;DR: In this paper, the photo-and thermal-oxidation of polypropylene fabric was investigated using Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS).
Abstract: The photo- and thermal-oxidation of a nonwoven polypropylene fabric was investigated using Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS). The infrared spectroscopic data indicate that alcohol, peroxide, aldehyde, ketone, carboxylic acid, and anhydride were formed as the products of the thermal oxidation and photooxidation of the polypropylene fabric. Ester was also formed during the thermal oxidation process. The thermal oxidation was accelerated after an initiation period. It was found that thermal oxidation occurred homogeneously between the surfaces of the fabric and its bulk. For the polypropylene fabric irradiated by ultraviolet (UV) radiation, however, the highest degree of oxidation occurred in the surface of the fabric facing the UV radiation source. It was also found that the UV radiation at 254 nm caused photooxidation of polyropylene. No photooxidation was observed in the fabric exposed to the UV radiation at 350 nm under the same conditions. © 1994 John Wiley & Sons, Inc.
TL;DR: In this paper, the authors used the depth profiling capability of Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) to distinguish spectroscopically between the surface layer (cuticle) and the interior (cortex) of intact keratin fibers.
Abstract: The depth profiling capability of Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) has been used to distinguish spectroscopically between the surface layer (cuticle) and the interior (cortex) of intact keratin fibers. The thermal diffusion lengths of wool and hair fibers, calculated as a function of the wavenumber and optical scanning velocity of the interferometer, indicate a depth resolution of the order of a micrometer. Shifts in the amide I and II bands to lower wavenumbers were observed with increasing velocity of the interferometer, consistent with differences in protein structure between the bulk and surface regions of the fiber. On the basis of these spectral changes, the location of the cuticle/cortex interface below the fiber surface can be determined.
TL;DR: In this paper, the laser damage thresholds of ZrO 2, TiO 2 and HfO 2 films of optical thickness λ ( λ = 248 nm) evaporated on quartz glass substrates were investigated with the photoacoustic probe beam deflection technique in a 1-on-1 irradiation mode for a range of fluences from below to above the thin-film laser damage threshold.
TL;DR: In this paper, a photoacoustic study of cobalt-doped ZnGa2O4 and MgGa 2O4 was performed and the observed visible bands were assigned to the spin-allowed electronic transition 4A2(4F)→4T1(4P).
TL;DR: A new and highly sensitive method, based on the photoacoustic effect, is described for in vivo and in situ studies of photosynthetic activity of undetached leaves.
TL;DR: In this paper, the thermal diffusivity α and conductivity k at room temperature of CdTe semiconductors having different crystalline qualities were determined using a photoacoustic technique.
Abstract: The thermal diffusivity α and conductivity k at room temperature of CdTe semiconductors having different crystalline qualities were determined using a photoacoustic technique. Thermal measurements obtained for each sample were correlated with photoluminescence spectroscopic results in order to associate the observed variation of α and k with crystalline imperfections in CdTe.
TL;DR: In this paper, the photoacoustic overtone spectrum of monochloroacetylene (HCCCl) has been recorded in the wave-number region 9500-14400 cm −1 with a titanium:sapphire ring laser.
TL;DR: The results suggest the feasibility of photoacoustics for quality control in the food-processing industry as a useful tool for discriminating between a variety of opaque, light-scattering samples.
Abstract: Photoacoustic spectroscopy in the 350–700 nm range proved a useful tool for discriminating between a variety of opaque, light-scattering samples. Spectral features originating from powdered food specimens of different colour and grain size were observed. These results suggest the feasibility of photoacoustics for quality control in the food-processing industry.
TL;DR: In this article, a calorimetric method was applied to monitor the heat emission during the induction of photosynthesis (fluorescence) in the green alga Chlorella kessleri suddenly illuminated with HeNe laser light.
Abstract: A calorimetric method was applied to monitor the heat emission during the induction of photosynthesis (fluorescence) in the dark-adapted green alga Chlorella kessleri suddenly illuminated with HeNe laser light. The same method was also applied to record the heat emission from an illuminated preparation of the major light-harvesting pigment-protein complex of photosystem II (LHCII). The results are discussed in terms of the kinetics of recorded fluorescence changes. The direct measurement of thermal energy dissipation by the calorimetric technique is compared with indirect methods based on photothermal techniques such as photoacoustic spectroscopy.
TL;DR: In this article, a pulsed laser photoacoustic technique is described, optimized for the simultaneous investigations of multiphoton absorption processes as well as rotational relaxation and vibration relaxation studies.
Abstract: A pulsed laser photoacoustic technique is described. It is optimized for the simultaneous investigations of multiphoton absorption processes as well as rotational relaxation and vibration relaxation studies. The experimental procedure is presented, concerning the calibration of the photoacoustic detector/cell set-up, applying the transmission spectroscopy technique. The obtained relationships, which can be alternatively used for the sensitivity curve S(p, gamma , T) of the apparatus, are analysed. A previously proposed model is confirmed.
17 Aug 1994
TL;DR: In this article, a simple theory of acoustic wave production within turbid media is presented, assuming a conventional, focused ultrasound transducer and translational scanning are used, assuming that optical absorption can be localized with millimeter spatial resolution for 10% absorption or less in biologic tissues as thick as 60 cm using safe levels of optical radiation.
Abstract: Localizing optical absorption within biologic tissue is compromised by the ubiquitous scattering of light that takes place within such tissues As an alternative to purely optical detection schemes, regional absorption of optical radiation can be detected and localized within highly scattering tissues by detecting the acoustic waves that are produced whenever differential absorption of radiation takes place within such tissues When the source of optical radiation is delivered in pulses of
TL;DR: In this paper, a photoacoustic spectroscopic (PAS) technique was applied to obtain depth-resolved information on CoAPO-44 samples by changing the modulation frequency.
TL;DR: In this paper, photoacoustic spectroscopy was used to determine the critical distance for electron transfer from porphyrin to quinone molecules randomly dispersed in a polymeric matrix.
01 Jan 1994
TL;DR: Photoacoustic spectroscopy was used to determine the critical distance for electron transfer from porphyrin to quinone molecules randomly dispersed in a polymeric matrix and it was found that the electron transfer occurred if the porphirin-quinone distance was less than 33 A.
Abstract: Photoacoustic spectroscopy was used to determine the critical distance for electron transfer from porphyrin to quinone molecules randomly dispersed in a polymeric matrix An enhancement of the porphyrin signal was observed as the quinone concentration was increased The data was analyzed according to the Perrin model [1] and it was found that the electron transfer occurred if the porphyrin-quinone distance was less than 33 ~, To confirm the validity of the method, the fluorescence quenching was also measured for the same samples In this case, the same critical distance was obtained
TL;DR: In this article, the authors combine the principles of nonequilibrium thermodynamics and photoacoustic Fourier transform infrared (PAFT-IR) spectroscopic detection as utilized in the analysis of none-quilibrium processes in matter.
Abstract: This study attempts to combine the principles of nonequilibrium thermodynamics and photoacoustic Fourier transform infrared (PAFT‐IR) spectroscopic detection as utilized in the analysis of nonequilibrium processes in matter. Such processes as diffusion and glass transition temperatures in polymers are analyzed. It is shown that the nonequilibrium mass balance equation, which governs diffusion processes, and the nonequilibrium internal energy balance responsible for the photoacoustic detection can be correlated. As a result, the relationship between the concentration of diffusant molecules in time and the photoacoustic intensity as a function of concentration can be established. Analysis of a nonequilibrium nature of the thermal processes near glass transmission temperatures shows that thermal nonequilibrium relaxations can be described in terms of rate constants for which the weight fractions with various energies can be correlated to the temperature fluctuations in a photoacoustic experiment. In this case, the internal energy balance equation can be represented by a regular heat expression.
TL;DR: A nonradiative transition in ion-implanted and epitaxially grown layers on a Si substrate was measured by a piezoelectric photoacoustic (PA) spectroscopy as mentioned in this paper.
Abstract: A nonradiative transition in ion-implanted and epitaxially grown layers on a Si substrate was measured by a piezoelectric photoacoustic (PA) spectroscopy. It is considered that the observed peak at 1.07 eV is caused by a nonradiative recombination of optically excited electrons from boron acceptor levels. The decrease of the 1.07 eV peak intensity by ion implantation is considered to be due to the formation of a surface damaged layer with deep defect levels. The PA spectra of epitaxially grown samples are well explained by summing the spectra of p- and n-type bulk samples. The electric field at the p-n junction may be effective in the PA signal generation mechanism in the higher photon- energy region.
31 Jan 1994
TL;DR: In this paper, phase correction functions generated from the monosignate spectrum of carbon black are used to compute the in-phase and quadrature interferograms of the sample, allowing unratioed PAS spectra to properly change sign as a function of lock-in amplifier phase angle, thereby making a 2D correlation analysis of the results meaningful.
Abstract: A method is described which corrects for the instrument response function in step-scan FT-IR photoacoustic spectroscopy (PAS) without distorting the thermal response information necessary for depth profiling layered samples. The instrumental phase correction functions are determined from the phase-sensitive photoacoustic signals of a strong surface absorber, such as carbon black. Phase correction functions generated from the monosignate spectrum of carbon black are used to compute the in-phase and quadrature interferograms of the sample. This treatment allows unratioed PAS spectra to properly change sign as a function of lock-in amplifier phase angle, thereby making a 2D correlation analysis of the results meaningful. This approach is used to clearly separate individual signals originating from a three-layer sample film of polydimethylsiloxane (PDMS), polyethylene (PE), and polystyrene (PS).
TL;DR: In this paper, the performance of four related techniques (i.e., photothermal deflection, thermal lensing, and photothermal phase shift spectroscopy) compared to the conventional beam transmittance spectrophotometry has been compared.
Abstract: Performances of four related techniques i.e., photoacoustic spectroscopy, photothermal deflection, thermal lensing, and photothermal phase shift spectroscopy have been compared to the conventional beam transmittance spectrophotometry. This concerns to the analytical potential in studies of environmental pollutants. Solutions of pesticides in water are used as specimens in this study. Spectrophotometric, photoacoustic and thermal lensing techniques are also used as detector behind HPLC loaded with a mixture of methanol and water. Thermal lensing and photothermal deflection spectroscopy appear superior in determination of environmental pollutants. The detection limit obtained for pesticides is 0.1µg/Kg.
TL;DR: In this paper, the optical band edge of solid C60 and the optical absorption coefficient at absorption edge are determined and a weak absorption shoulder at 1.70 eV is observed.
Abstract: Photoacoustic spectroscopy of C60 thin film is presented. The optical band edge of solid C60 and the optical absorption coefficient at absorption edge are determined. A weak absorption shoulder at 1.70 eV is observed. While the thickness of C60 thin film is less than 1 μm, photoacoustic saturation at band edge is avoided.