Showing papers on "Photoacoustic spectroscopy published in 2000"
TL;DR: In this article, a nitrogen dioxide calibration method was developed to evaluate the theoretical calibration for a photoacoustic instrument used to measure light absorption by atmospheric aerosols at a laser wavelength of 532.0 nm.
Abstract: A nitrogen dioxide calibration method is developed to evaluate the theoretical calibration for a photoacoustic instrument used to measure light absorption by atmospheric aerosols at a laser wavelength of 532.0 nm. This method uses high concentrations of nitrogen dioxide so that both a simple extinction and the photoacoustically obtained absorption measurement may be performed simultaneously. Since Rayleigh scattering is much less than absorption for the gas, the agreement between the extinction and absorption coefficients can be used to evaluate the theoretical calibration, so that the laser gas spectra are not needed. Photoacoustic theory is developed to account for strong absorption of the laser beam power in passage through the resonator. Findings are that the photoacoustic absorption based on heat-balance theory for the instrument compares well with absorption inferred from the extinction measurement, and that both are well within values represented by published spectra of nitrogen dioxide. Photodisso...
164 citations
TL;DR: In this article, the lifetime of the electron-hole pair is on the order of 25 ns with about 60% of the trapped electrons recombining on this time scale, and the electron trapping sites were determined to lie, on average, 0.8 eV below the conduction band edge.
123 citations
TL;DR: The penetration of the drugs dithranol and methoxsalen from semisolid Vaseline formulation into an artificial dodecanol-collodion membrane was followed by three spectroscopic methods; it appears that the diffusion coefficient for the drug in the membrane depends on the distance.
41 citations
TL;DR: In this paper, the optical properties of soft tissue in the near infrared were determined using optoacoustic spectroscopy using an optical parametric oscillator (OPO) having a tuning range from 1500 to 3500 nm.
Abstract: Optical properties of soft tissue in the near infrared are determined using optoacoustic spectroscopy. The acoustic signals are generated with an optical parametric oscillator (OPO) having a tuning range from 1500 to 3500 nm. In order to record the acoustic wave on the same side as the exciting laser pulse (backward mode), an infrared transparent pressure transducer was developed. The effective attenuation coefficients of cartilage and chicken breast were determined in a range between 1860 and 1940 nm. The minimum absorption or effective attenuation coefficient that could be measured with the presented method was 10 cm−1, limited by the detector sensitivity of 1.68% signal change per bar. The maximum measurable coefficient was about 1000 cm−1, limited by temporal broadening of the acoustic signals due to the finite pulse duration (6 ns) of the OPO. Optoacoustic infrared spectroscopy is shown to be suitable for on-line noninvasive, in vivo tissue characterization.
39 citations
TL;DR: In this paper, the structural, surface morphology and optical properties of chemical bath deposited cadmium sulfide (CdS) thin films under the effect of variation of S/Cd ratio were studied.
Abstract: We study the structural, surface morphology and optical properties of chemical bath deposited (CBD) cadmium sulfide (CdS) thin films under the effect of variation of S/Cd ratio CdS thin films have been successfully deposited by CBD technique with solutions containing S/Cd ionic concentration ratio of 50, 25, 10, 05 and 025 Single phase CdS, with a hexagonal structure, is observed for the concentration of S/Cd = 50, 25, 10 and 05 films while for the ratio of 025, the films exhibited a partially amorphous nature These have been confirmed by X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM and SEM) analyses The band gaps of the films obtained by transmission and photoacoustic spectra are found to be in the range of 240 to 326 eV The large variation of band gaps of the films with composition is discussed by employing quantum size effect phenomena The transition levels of CdS are also studied using photoacoustic spectroscopy
35 citations
TL;DR: In this article, the absorption, luminescence and photoacoustic spectra of YAG:Ce 3+ have been measured and analyzed and the Jahn-Teller type coupling in the excited states of Ce 3+ has been evidenced.
32 citations
TL;DR: In this paper, the suitability of Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) for analyzing potato chips was investigated, where the functional groups, vibration modes and intensities corresponding to frequencies related to moisture, fat and protein were labelled.
Abstract: The suitability of Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) for analysing potato chips was investigated. The functional groups, vibration modes and intensities corresponding to frequencies related to moisture, fat and protein in PA spectra were labelled. Oxidation experiments were carried out by heating home-made chips in a convection oven at 80 °C. Changes in chemical groups related to fat and oil were observed visually and statistically. Spectral data were analysed using PCA correlation and a linear discriminant analysis technique with squared Mahalanobis distance metric to estimate the extent of oxidation. Results showed that deterioration indeed could be monitored by photoacoustic spectroscopy. Depth profile analysis of the samples showed that a spectral difference in the fat, moisture and protein bands at different layers exists. Results demonstrated that FTIR-PAS with its depth-profiling capability could be used for qualitative analysis.
© 2000 Society of Chemical Industry
30 citations
Book•
23 Feb 2000
TL;DR: The role of the Stressed State Optical Detection of Photothermal Phenomena in Operating Electronic Devices - Temperature and Defect Imaging Photothermal Radiometric Study of Implanted Semiconductor Non-radiative Investigation of Impurity and defect levels in Si and GaAs by Piezoelectric Photoacoustic Spectroscopy (PPAS) Effect of the Confined Plasma on Thermal Wave Fields in Semiconductors as discussed by the authors.
Abstract: Photothermal and Photoacoustic Characterization of Porous Silicon Structures The Peculiarities of Contrast Formation in Photoacoustic Microscopy of Semiconductors and the Role of the Stressed State Optical Detection of Photothermal Phenomena in Operating Electronic Devices - Temperature and Defect Imaging Photothermal Radiometric Study of Implanted Semiconductor Nonradiative Investigation of Impurity and Defect Levels in Si and GaAs by Piezoelectric Photoacoustic Spectroscopy (PPAS) Effect of the Confined Plasma on Thermal Wave Fields in Semiconductor Devices Photothermal Characterization of Semiconductors Nonlinear Photoacoustic and Photothermal Phenomena in Semiconductors Carrier Transport Contribution to Thermoelastic and Electronic Deformation in Semiconductors Photothermal Spectroscopy of Ceramic and Nano-Crystal II-IV Compound Semiconductors, Together with Ternary and Multinary Compounds.
30 citations
TL;DR: In this paper, the authors measured the optical absorption of TiO2 powders by photoacoustic (PA) spectroscopy, which is powerful for detecting small amounts of strongly scattering materials.
Abstract: We have measured the optical absorption of TiO2 powders by photoacoustic (PA) spectroscopy, which is powerful for detecting small amounts of strongly scattering materials. The band-gap energies Eg of rutile and anatase types of TiO2 powders with particle radii of 40 nm are 3.06 eV and 3.20 eV, respectively, from PA intensity and PA phase spectra, indicating the usefulness of PA spectroscopy. The PA intensity and phase spectra show that the Eg of anatase-type TiO2 powders with a particle radius of 11 nm is 3.25 eV (blue shift) within the experimental accuracy, indicating the possible onset of a quantum size effect with decreasing particle size. The PA intensities plotted semilogarithmically vary linearly with photon energy immediately below the band-gap, in accordance with Urbach's rule (exponential tail). The slope of the exponential absorption of rutile-type TiO2 powders is larger than that of the anatase, indicating that the anatase-type has increasing energy from the displacement of atoms specifically due to oxygen vacancies and/or chlorine impurities in the production processes of the powders.
28 citations
TL;DR: In this paper, an anharmonic oscillator local mode model and an ab initio dipole moment function were used to calculate oscillator strengths for the aryl and methyl transitions.
Abstract: The room-temperature vapor phase overtone spectrum of toluene-α-d2 has been recorded in the CH stretching region corresponding to ΔvCH = 2−6 with conventional near-infrared spectroscopy (ΔvCH = 2−4) and with intracavity titanium:sapphire and dye laser photoacoustic spectroscopy (ΔvCH = 4−6). Both absolute oscillator strengths (conventional spectra) and relative oscillator strengths within a given overtone (conventional and photoacoustic spectra) have been measured. The aryl region of the spectrum is interpreted in terms of two nonequivalent aryl local modes and is essentially identical to the aryl regions of the spectra of toluene-d0 and toluene-α-d1. However, the methyl band profile differs significantly in these three molecules. We use an anharmonic oscillator local mode model and an ab initio dipole moment function to calculate oscillator strengths for the aryl and methyl transitions. Parameters for this model come from a fit of the aryl transition energies and from a fit of the methyl spectral profile...
20 citations
19 May 2000
TL;DR: Pulsed-photoacoustic spectroscopy in the near IR portion of the optical spectrum was used as a local technique for quantitative monitoring of tissue hemoglobin concentration and its oxygenation state as discussed by the authors.
Abstract: Pulsed-photoacoustic spectroscopy in the near IR portion of the optical spectrum was used as a local technique for quantitative monitoring of tissue hemoglobin concentration and its oxygenation state. A pulsed, tunable optical source coupled to a 1mm-diameter optical fiber cable was used to deliver optical energy to the tissue under study. The fiber was placed either on the exterior surface or inserted into the tissue. An ultrasonic signal was produced in the tissue as a result of the absorbed light pulse energy. Since the rate of conversion of laser light energy to heat was rapid and the laser pulse as much shorter than the tissue thermal- diffusion length, the ultrasonic signal amplitude was proportional to the energy absorbed. Spectra of absorbing compounds were obtained by measuring the variation in the acoustic signal with source wavelength. In contrast with near-IR spectroscopic techniques that measure diffuse light transmission and assume knowledge of the pathlength of light traveling through tissues in order to determine the absorption coefficient, the photoacoustic response is produced directly by light absorption. Light scattering merely modifies the spatial distribution of the absorbed energy. Our studies demonstrate that photoacoustic spectra obtained both in vitro and in vivo allow determination of relative changes in the concentration of oxy- and de- oxyhemoglobin.
TL;DR: The technique of pulsed indirect photoacoustic spectroscopy is applied to the examination of free liquid surfaces, and the prospects are assessed for remote detection and identification of chemical species in a field environment.
Abstract: The technique of pulsed indirect photoacoustic spectroscopy is
applied to the examination of free liquid surfaces, and the prospects
are assessed for remote detection and identification of chemical
species in a field environment. A CO2 laser (tunable
within the 9–11-µm region) provides pulsed excitation for a
variety of sample types; the resulting photoacoustic pulses are
detected at ranges of the order of a few centimeters. The
phenomenon is investigated as a function of parameters such as
temperature, sample depth, laser-pulse energy, pulse length, and beam
diameter. The results are in good agreement with a theoretical
model that assumes the mechanism to be expansion of air resulting from
heat conduction from the laser-heated surface of the sample under
investigation. Signal and noise processing issues are discussed
briefly, and the possible extension of the technique to ranges of the
order of 10 m is assessed.
TL;DR: In this article, photoacoustic spectroscopy (PAS) is used in the study of non-crystalline solids and the variation of the energy levels and luminescence efficiencies and the intramolecular relaxation processes of silica gels doped with rare earth complexes with salicylic acid.
Abstract: Photoacoustic spectroscopy (PAS) is useful in the study of non-crystalline solids. By using PA amplitude and phase spectra, together with IR and fluorescence spectra, the variation of the energy levels and luminescence efficiencies and the intramolecular relaxation processes of silica gels doped with rare earth complexes with salicylic acid have been studied in comparison with their corresponding pure complexes. After the complexes are doped into silica gels, the PA and emission peaks of the ligands show a shift, but the peaks of rare earth ions do not apparently shift. The complex molecules are dispersed in the silica gel, this reduces concentration quenching. In addition, the relatively rigid host structure of silica gel limits the vibrations of the ligands, which decreases the non-radiative transition and increases the lifetime of Tb 3+ .
TL;DR: By optimizing the size of a photoacoustic cell for decreasing acoustic loss and noise, and using a proper multipass arrangement for increasing light power in the cell and optical coupling to the acoustic wave, a high-resolution external laser photo-acoustic spectrometer with a detection sensitivity of 6.35×10−9 cm−1 (1:1 signal to noise level) has been developed.
Abstract: By optimizing the size of a photoacoustic cell for decreasing acoustic loss and noise, and using a proper multipass arrangement for increasing light power in the cell and optical coupling to the acoustic wave, a high-resolution external laser photoacoustic spectrometer with a detection sensitivity of 6.35×10−9 cm−1 (1:1 signal to noise level) has been developed. Using this apparatus, the high quality Doppler-limited overtone spectra of AsH3 (600) and H2Se (60) have been observed at room temperature in the wave number regions 11 500–11 650 and 12 600–12 925 cm−1, respectively. Results are presented which highlight the applicability of this apparatus to the spectroscopy of weak optical transitions.
TL;DR: In this article, a ternary compound embedded in mordenite zeolite host is studied by using Photoacoustic techniques and X-ray diffraction, which shows a strong dependence of thermal and optical parameters with the X value (Zn% concentration).
TL;DR: Laser photoacoustic spectroscopy (LPAS) has been used to simultaneously measure scattered light and absorbed light with the use of a single piezoelectric transducer detector.
Abstract: Laser photoacoustic spectroscopy (LPAS) has been used to simultaneously measure scattered light and absorbed light with the use of a single piezoelectric transducer detector. Samples of Ludox™ colloidal silica, with and without added potassium chromate, were illuminated with pulses of 308 or 355 nm light. Signals were measured with a 1 MHz ultrasonic transducer clamped to the side of the cuvette. The resulting oscilloscope tracing shows a pattern of signals originating from light scatter and light absorption that is consistent with experimental geometry and the speeds of light and sound, and linear with incident laser pulse energy. The absorbed light signals are independent of the distance of the laser beam from the transducer, while the scattered light signals are strongly distance-dependent. The absorbed light signals are more indicative of true sample absorbance than are readings from a standard spectrophotometer. A spectrophotometer sums contributions from scattering and absorbance to give an optical density reading, while LPAS separates scattering from absorbance to give quantitative information on each function. Scattered light and fluorescent light behave very similarly in the LPAS technique. Our experiments were done with well-characterized colloidal silica samples, but the technique is readily extended to larger, more heterogeneous, and photochemically complex biological and environmental samples.
TL;DR: In this paper, the potential of Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) for examination of food and the package was demonstrated, and full-fat cheddar cheese slices wrapped in polymer package were chosen as the food sample for analysis.
Abstract: The potential of Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) for examination of food and the package was demonstrated. Full-fat cheddar cheese slices wrapped in polymer package were chosen as the food sample for analysis. Photoacoustic spectroscopy (PAS) in conjunction with the step-scan and digital signal processing (DSP) function was used to perform depth-profiling studies of the intact sample and package. Well-separated PAS bands of fat and protein were obtained in the spectra of cheddar cheese samples with minimum sample preparation. Cheese samples were kept in a dessicator overnight to minimize the effect of moisture on the PAS spectra. Depth profiling study of the cheese polymer package indicated that there is a diffusion of cheese components into the package during storage. Index Headings: Fourier transform infrared photoacoustic spectroscopy; Step-scan; Digital signal processing; Cheese; Package, Depth profiling.
25 Jan 2000
TL;DR: In this article, the authors report on recent advances of laser spectroscopic schemes applied to air pollution monitoring, including a line-tunable CO2 laser, a continuously tunable high-pressure CO 2 laser, an optical-parametric- oscillator-based difference-frequency (DFG) laser and a diode-based DFG laser.
Abstract: We report on recent advances of laser spectroscopic schemes applied to air pollution monitoring. All systems presented are based on tunable narrowband infrared sources including a conventional line-tunable CO2 laser, a continuously tunable high-pressure CO2 laser, an optical-parametric- oscillator-based difference-frequency (DFG) laser and a diode-based DFG laser. These systems cover the mid-infrared wavelength range important for fundamental molecular absorptions. Gas detection is performed with a multipass transmission cell, with specially designed photoacoustic cells using resonant and nonresonant configurations with a single microphone or multi-microphone arrays or with a photothermal arrangement sensing the temporal change of the refractive index. The performance of these systems is illustrated with various examples of trace gas monitoring on the one hand and determination of molecular relaxation rate constants on the other hand with the photothermal scheme. In many cases detection limits corresponding to minimum concentrations in the ppb (10-9, nmole/mole) or even sub-ppb level are achieved. It is demonstrated that this kind of laser spectrometers offer easiness of operation (room temperature, neither sample preparation nor pretreatment, portability), excellent sensitivity and selectivity, large dynamic range (up to 7 orders of magnitude) and good temporal resolution.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this paper, the photoacoustic magnitude spectra of a coated paper and the uncoated basepaper are used to calculate difference spectra, and an increasing relative contribution of the coating layer with an increasing phase modulation frequency is found.
Abstract: Experimental photoacoustic (PA) magnitude spectra of a coated paper and the uncoated basepaper are presented. The normalized and scaled PA magnitude spectra are used to calculate difference magnitude spectra. It was decided to scale all PA magnitude spectra to (low) equal intensity at the approximately optically thin spectral range before subtraction. Then no infrared (IR) bands of identical band shape and height (as needed for common difference spectroscopy) in either PA magnitude spectrum are needed. Contributions of the two individual layers to the IR-PA magnitude spectrum of the coated paper are separated in the difference spectrum by their sign. An increasing relative contribution of the coating layer with an increasing phase modulation frequency is found. On decreasing the thermal length to a value near the coating thickness, the difference spectra increasingly show positive coating bands and negative bulk signals. The extension of the Rosencwaig-Gersho theory to a double-layered system introduced by N. C. Fernelius [J. Opt. Soc. Am . 70, 480 (1980) and J. Appl. Phys. 50, 650 (1980)] applied to synthetic spectra confirms the experimental observation. It is found that photoacoustic difference spectroscopy may provide quantitative depth-resolved spectral information due to the presented scaling procedure, and photoacoustic difference magnitude spectra of any polymeric laminate may therefore be calculated.
TL;DR: In this article, photoacoustic spectroscopy (PAS) data was used to calculate the depth profile of dyed PET films with values around 54 μm and showed that the major amount of incorporated dye was obtained by the following combination of variables: temperature and time of modifier treatment were, respectively, 72.5°C and 15 min; time and temperature of dyeing were respectively, 90°C, and 195 min for a dye concentration of 0.133 g/L.
Abstract: Poly(ethylene terephtalate), PET, can be modified with N,N-dimethylacryl-amide to obtain a better incorporation of disperse dye (Disperse Blue 79). Minimal variations in the decomposition at 10% level, melting, and glass transition temperatures, show that the thermal stability of modified PET films does not change when compared to nonmodified PET. The atomic force images show nanopeaks formation on the surface due to the modification. Modified PET films show a decrease in the contact angle and then, an increase in the superficial tension measurements, when compared to the value of 37 ± 1 dynes cm -1 (nonmodified), with values liying in the range of 42-46 ± 0.5 dynes cm -1 . The data obtained by photoacoustic spectroscopy (PAS) for dyed PET films show a dye peak at 580 nm. The data analysis of the peak area show that PET films modified with N,N-dimethylacrylamide for 15 min at 85°C, dyed for 6 h at 85°C with a dye concentration of 0.333 g/L, incorporate three times more dye than the nonmodified films dyed in the same conditions. By the data obtained from PAS, it was possible to calculate the depth profile of dyeing with values around 54 μm. Factorial analyses show that the dyeing time was the most important variable. The major amount of incorporated dye was obtained by the following combination of variables: temperature and time of modifier treatment were, respectively, 72.5°C and 15 min; time and temperature of dyeing were, respectively, 90°C and 195 min for a dye concentration of 0.133 g/L.
24 Mar 2000
TL;DR: F Fourier Transform Infrared (FTIR) Spectroscopy of lesions before ablation show a strong protein component associated with organic material (i.e., bacteria) and following ablation this protein component is absent.
Abstract: Enamel caries lesions on extracted teeth were ablated with a pulsed Nd:YAG or Er:YAG laser. Tissue ablation was accompanied by a popping' sound (the photoacoustic response). Analysis of the photoacoustic response yields insights into the laser / tissue interactions. Fourier Transform Infrared (FTIR) Spectroscopy of lesions before ablation show a strong protein component associated with organic material (i.e., bacteria). Following ablation this protein component is absent.
TL;DR: In this paper, the potentialities of the infrared photoacoustic method and the ATR Golden Gate method for the measurements of oriented bulk polymer systems are compared, and both methods are suitable for the estimation of orientation, if low and medium intensity bands are used.
TL;DR: In this paper, photoacoustic lines are assigned to the individual d-d transitions of Cu2+ ions, which are further exploited to determine the diverse metal-ligand interaction of the studied compound employing simple crystal field analysis.
Abstract: The potential of photoacoustic spectroscopy to resolve the crystal field levels of Cu2+ ions in three polyamine copper complexes, aqua spermine copper sulfate trihydrate [NH2(CH2)3NH(CH2)4NH(CH2)3NH2Cu2+H2O]SO42-3H2O, norspermine copper sulfate trihydrate [NH2(CH2)3NH(CH2)3NH(CH2)3NH2Cu2+SO42-]3H2O, and homospermine copper sulfate dihydrate [NH2(CH2)3NH(CH2)2NH(CH2)3NH2Cu2+SO42-] 2H2O, has been explored along with UV/VIS and electron paramagnetic resonance (EPR) spectroscopy. Intense absorption is detected in the photoacoustic spectrum corresponding to the d-d transition band weakly traced in the corresponding optical spectrum. The observed fine structure photoacoustic lines are assigned to the individual d-d transitions of Cu2+ ions, which are further exploited to determine the diverse metal-ligand interaction of the studied compound employing simple crystal field analysis.
TL;DR: A new nonlinear Raman spectroscopy technique for trace-gas detection was proposed and demonstrated, involving the use of a thermal-lens detection scheme to monitor thermal emission from the stimulated Raman process.
Abstract: A new nonlinear Raman spectroscopy technique for trace-gas detection was proposed and demonstrated. The technique involved the use of a thermal-lens detection scheme to monitor thermal emission from the stimulated Raman process. We termed this technique thermal-lens Raman spectroscopy, and it was combined with a novel scheme involving a nonlinear Raman spectroscopy without a tunable laser. This technique was applied to detecting trace hydrogen molecules in the atmosphere by use of a pulsed Nd:YAG laser and a continuous-wave He-Ne probe laser. A detection limit of 9 parts in 10(6) was attained.
TL;DR: In this article, a method to determine surface stratification of components within a thermoplastic olefin (TPO) compound is developed using Fourier transform infrared (FT-IR) step-scan photoacoustic spectroscopy (S2 PAS).
TL;DR: In this article, the propagation of wide-band acoustic pulses in one-dimensional periodic structures consisting of alternating plexiglas and water layers is studied theoretically and experimentally with the use of the wideband photoacoustic spectroscopy based on the laser excitation of ultrasound.
Abstract: The propagation of wide-band acoustic pulses in one-dimensional periodic structures consisting of alternating plexiglas and water layers is studied theoretically and experimentally. The experiment is carried out with the use of the wide-band photoacoustic spectroscopy based on the laser excitation of ultrasound and a wide-band signal detection. The fact that the transmission spectrum of a periodic structure has alternating pass and stop bands is confirmed experimentally. The width and localization of the stop bands strongly depend on the thickness of the layers and on the phase velocity of ultrasound in them. It is demonstrated that defects of the structure periodicity give rise to one or several local transmission maxima in the stop band and to a modification of the pass band. The amplitude and position of a local maximum in the stop band strongly depend on the position of the defective layer. The experimental data agree well with the results of numerical simulation.
TL;DR: In this article, the authors used CO 2 laser photoacoustic spectroscopy for quantitative analysis of a multicomponent gaseous mixture of pollutants with similar chemical structures (toluene, ortho -, para - and meta -xylenes) in trace concentrations (50-700ppm).
TL;DR: In this paper, an energy-level diagram related to the luminescence of porous silicon has been constructed from the luminecence data, which is confirmed in detail by the photoacoustic spectra.
Abstract: Porous silicon has been studied with photoluminescence, photoluminescence excitation, and photoacoustic spectroscopy. From the luminescence data, an energy-level diagram related to the luminescence is constructed. The diagram is confirmed in detail by the photoacoustic spectra. The results are discussed with the conclusion that they are in good agreement with the surface-band oxyhydride-like emitter, which recently has been established as the source for the photoluminescence from porous silicon.
TL;DR: In this article, the thermal properties of a diamond film deposited by the chemical vapor deposition (CVD) method were measured using the photoacoustic (PA) method, which is useful for measuring the thermal characteristics of ultra-thin films, because it utilizes critical damping of thermal waves.
TL;DR: In this article, high-pressure photoacoustic calorimetry was used to determine the volume of reaction for organometallic compounds, which allowed the calculation of reaction enthalpies from the photo-acoustic data.
Abstract: We have developed high-pressure photoacoustic calorimetry to determine the volume of reaction for organometallic compounds. This allows the calculation of reaction enthalpies from the photoacoustic data. The photoacoustic signal for chromium hexacarbonyl with acetonitrile in heptane was examined from near ambient pressure to 100 MPa. Two components of the signal were resolved at 10–20 mM acetonitrile. The fast component is attributed to CO displacement by heptane ( −1 , respectively). The enthalpies of CO displacement by heptane are 28 kcal mol −1 and heptane displacement by acetonitrile is −22 kcal mol −1 . Neglect of the volumes of reaction in the PAC experiments can lead to an error of 6 kcal mol −1 .