Showing papers on "Photoacoustic spectroscopy published in 1990"
TL;DR: In this paper, the main conventional techniques currently applied to the detection of gaseous air pollutants, as well as the state of the art of novel detection schemes, are discussed, and the theoretical aspects of photoacoustic spectroscopy with respect to trace gas detection and multicomponent analysis are discussed in detail.
Abstract: The subject of air pollution monitoring is reviewed. First, we discuss the main conventional techniques currently applied to the detection of gaseous air pollutants, as well as the state of the art of novel detection schemes. We distinguish between nonspectroscopic and spectroscopic methods. Spectroscopic techniques are of primary interest since they offer several advantages, e.g., the simultaneous monitoring of numerous substances. Photoacoustic (PA) spectroscopy represents a promising spectroscopic technique due to its intrinsically high sensitivity, the large dynamic range, and the comparatively simple experimental arrangement. Emphasis is put on detection selectivity which often may restrict the range of applications of the technique for pollution monitoring due to the lack of powerful, continuously tunable IR laser sources. The theoretical aspects of PA spectroscopy with respect to trace gas detection and multicomponent analysis are thus discussed in detail. Some characteristics of a portable PA system built by us are outlined in order to illustrate the usefulness of such systems.
227 citations
TL;DR: In this article, a photoacoustic cell excited in its first longitudinal mode is placed inside the cavity of a CO2 waveguide laser to measure the C2H4 emission of several Rumex species.
Abstract: A photoacoustic intracavity configuration is presented; a resonant photoacoustic cell excited in its first longitudinal mode is placed inside the cavity of a CO2 waveguide laser. Due to the high laser power and the sharp intracavity focus, saturation effects occur in the excitation and relaxation process of absorbing C2H4 molecules. A more optimal configuration is applied to measure the C2H4 emission of several Rumex species. A detection sensitivity of 6 ppt (parts per trillion) C2H4 is reached, equivalent to a minimal detectable absorption of 1.8×10−10 cm−1.
153 citations
Book•
01 Jan 1990
TL;DR: The laboratory use of computers laboratory balances organic elemental analysis continuous flow analysis atomic emission spectroscopy atomic absorption and flame emission spectrometry ultraviolet, visible and near-infrared spectrophotometries molecular fluorescence and phosphorescence rotational and vibrational spectroscopic x-ray methods photoacoustic and acoustic X-ray techniques of chiroptical Spectroscopy nuclear magnetic resonance electon paramagnetic resonance xray as mentioned in this paper.
Abstract: The laboratory use of computers laboratory balances organic elemental analysis continuous-flow analysis atomic emission spectroscopy atomic absorption and flame emission spectrometry ultraviolet, visible and near-infrared spectrophotometries molecular fluorescence and phosphorescence rotational and vibrational spectroscopy x-ray methods photoacoustic spectroscopy techniques of chiroptical spectroscopy nuclear magnetic resonance electon paramagnetic resonance x-ray
140 citations
TL;DR: In this article, a computer controlled CO-laser photoacoustic system is presented for the detection of trace gases at ppbv concentrations in exhaust gas using a dual-beam setup with sample and reference cell.
119 citations
TL;DR: In this article, a photoacoustic wave is determined by the geometry and dimensions of the particle, and by its sound speed and density relative to the fluid that surrounds it, which is referred to as signatures.
Abstract: Absorption of pulsed laser radiation by a single particle generates a photoacoustic wave whose time profile can be measured with a wideband pressure transducer. Solution of the wave equation for pressure in one, two, and three dimensions shows that the photoacoustic wave is determined by the geometry and dimensions of the particle, and by its sound speed and density relative to the fluid that surrounds it. Photoacoustic waves, referred to here as signatures, are reported in experiments in which fluid droplets, cylinders, and layers are irradiated with 10-nanosecond laser pulses.
117 citations
TL;DR: The photoacoustic determination of the ammonia concentration in atmospheric air by absorption of CO( 2) laser radiation at 9.22 microm is influenced by the presence of H(2)O and CO(2), which causes important changes in phase and amplitude of the photoac acoustic signal.
Abstract: The photoacoustic determination of the ammonia concentration in atmospheric air by absorption of CO(2) laser radiation at 9.22 microm is influenced by the presence of H(2)O and CO(2). Kinetic cooling due to the coupling of excited CO(2) and N(2) levels causes important changes in phase and amplitude of the photoacoustic signal. Theoretical background is presented to deduce the correct NH(3) concentration from the signal. The experimental setup used to perform field measurements is described. Adhesion of NH(3) to the walls of the resonant photoacoustic cell was investigated. Temperature effects are treated. Field data of NH(3) and H(2)O concentrations are presented.
100 citations
TL;DR: In this paper, two atmospheric elemental carbon measurement methods based on different analytical principles have been compared using data collected during the summer of 1987 at the Claremont, California site of the Southern California Air Quality Study (SCAQS).
51 citations
TL;DR: In this article, two fundamentally different techniques for measuring atmospheric elemental carbon (EC) aerosol were compared to validate the methods, and a 1 : 1 correlation of atmospheric EC concentrations resulted for measurements by the photoacoustic method vs the thermal method over coincident sampling times.
36 citations
TL;DR: In this article, the stability constants of praseodymium acetate and oxydiacetate complexes were measured by laser-induced photoacoustic spectroscopy, conventional UV-visible absorption spectrograph, and pH titration.
Abstract: The authors measured the stability constants of praseodymium acetate and oxydiacetate complexes by laser-induced photoacoustic spectroscopy, conventional UV-visible absorption spectroscopy, and pH titration. For the spectroscopic studies, changes in the free Pr absorption peaks at 468 and 481 nm were monitored at varying ligand concentrations. The total Pr concentration was 1 {times} 10{sup {minus}4} M in solutions used for the photoacoustic studies and 0.02 M for conventional spectroscopy. For the pH titrations, we used solutions whose Pr concentrations varied from 5 {times} 10{sup {minus}3} to 5 {times} 10{sup {minus}2} M, with total ligand-to-metal ratios ranging from 1 to 10. A comparison of the results obtained by the three techniques demonstrates that photoacoustic spectroscopy can give the same information about metal-ligand speciation as more conventional methods. It is particularly suited to those situations where the other techniques are insensitive because of limited metal concentrations.
31 citations
TL;DR: A design of a Stark photoacoustic cell capable of detecting ammonia in ambient air at trace levels is discussed.
Abstract: A design of a Stark photoacoustic cell capable of detecting ammonia in ambient air at trace levels is discussed.
23 citations
TL;DR: Laser induced photoacoustic spectroscopy (LIPAS) has been confirmed as an analytical tool, suitable for the determination of inorganic and organic species in aqueous and organic solvents, reaching detection limits two orders of magnitude lower than those obtained with conventional spectrophotometry as mentioned in this paper.
Abstract: Laser induced photoacoustic spectroscopy (LIPAS) has been confirmed as an analytical tool, suitable for the determination of inorganic and organic species in aqueous and organic solvents, reaching detection limits two orders of magnitude lower than those obtained with conventional spectrophotometry.
TL;DR: The photosynthetic energy storage yield of uncoupled thylakoid membranes was monitored by photoacoustic spectroscopy at various measuring beam intensities and it was assumed that the energy storage elicited by the photosystems at 35 Hz is detected at the level of the plastoquinone pool.
Abstract: The photosynthetic energy storage yield of uncoupled thylakoid membranes was monitored by photoacoustic spectroscopy at various measuring beam intensities. The energy storage rate as evaluated by the half-saturation measuring beam intensity (i50) was inhibited by 3-(3,4-dichlorophenyl)-1,1 dimethylurea, by heat inactivation or by artificial electron acceptors specific for photosystem I or photosystem II; and was activated by electron donors to photosystem I. The reactions involving both photosystems were all characterized by a similar maximal energy storage yield of 16±2 percent. The data could be interpreted if we assumed that the energy storage elicited by the photosystems at 35 Hz is detected at the level of the plastoquinone pool.
TL;DR: Thermal emission and photochemical energy storage were examined in photosystem I reaction center/core antenna complexes using photoacoustic spectroscopy and are compatible with the hypothesis that energy storage in PS I arises from charge separation between P700 and Fe-S centers FA-FB that is stable on the time scale of the photoac acoustic modulation.
Abstract: Thermal emission and photochemical energy storage were examined in photosystem I reaction center/core antenna complexes (about 40 Chl a/P700) using photoacoustic spectroscopy. Satisfactory signals could only be obtained from samples bound to hydroxyapatite and all samples had a low signal-to-noise ratio compared to either PS I or PS II in thylakoid membranes. The energy storage signal was saturated at low intensity (half saturation at 1.5 W m(-2)) and predicted a photochemical quantum yield of >90%. Exogenous donors and acceptors had no effect on the signal amplitudes indicating that energy storage is the result of charge separation between endogenous components. Fe(CN)6 (-3) oxidation of P700 and dithionite-induced reduction of acceptors FA-FB inhibited energy storage. These data are compatible with the hypothesis that energy storage in PS I arises from charge separation between P700 and Fe-S centers FA-FB that is stable on the time scale of the photoacoustic modulation. High intensity background light (160 W m(-2)) caused an irreversible loss of energy storage and correlated with a decrease in oxidizable P700; both are probably the result of high light-induced photoinhibition. By analogy to the low fluorescence yield of PS I, the low signal-to-noise ratio in these preparations is attributed to the short lifetime of Chl singlet excited states in PS I-40 and its indirect effect on the yield of thermal emission.
01 Jan 1990
TL;DR: In this article, the main principles, detecting techniques and different applications are summarized with special emphasis on plant analysis, and a general scheme of photoacoustic and photothermal measurements is given in Fig. 1.
Abstract: Definition. Photoacoustic (PA) or optoacoustic measurements in the original, strict sense comprise the detection of acoustic waves which arise from non-radiative de-excitation (radiationless transition) of the sample as a consequence of absorption of continuously amplitude-modulated light. Today this term is extended to measurements of acoustic waves induced by other factors, e.g. gas exchange, surface deformation, evaporation. Furthermore photothermal (PT) techniques have been developed which do not determine acoustic waves but measure the temperature rise induced by non-radiative de-excitation or thermal effects on the sample itself or on the medium surrounding the sample. The excitation of the sample may be carried out not only by light but also by any other type of energetic radiation. A general scheme of PA and PT measurements is given in Fig. 1. In this contribution the main principles, detecting techniques and different applications are summarized with special emphasis on plant analysis.
TL;DR: The amplitude of the photoacoustic signal is measured as a function of the chopping frequency for thin benzophenone polycrystalline samples in the temperature range 100-300 K as mentioned in this paper.
Abstract: The amplitude of the photoacoustic signal is measured as a function of chopping frequency for thin benzophenone polycrystalline samples in the temperature range 100–300 K. Analysis of experimental results, obtained by rear surface illumination, allows us to determine the thermal diffusivity of benzophenone crystals in the whole temperature range.
TL;DR: In this paper, two different photothermal methods were used to monitor thermal deactivation of excited pigments during the dark light transitions, and the in vivo photothermal signals measured with both techniques were shown to remain constant during induction of photosynthesis under high light conditions, suggesting that, in contrast to current hypotheses, energy-dependent quenching qE is not associated with significant changes in thermal dissipation of absorbed light energy in the chloroplasts.
Abstract: — Intact leaves, previously adapted to darkness for a prolonged period of time, were suddenly illuminated with a strong, photosynthetically saturating, white light (ca 1500 μmol m−2 s_1), resulting in the rapid establishment of a large energy‐dependent chlorophyll fluorescence quenching (qE) as shown by in vivo fluorescence measurements with a pulse amplitude modulation technique. Two different photothermal methods, photoacoustic spectroscopy and photothermal deflection spectroscopy, were used to monitor thermal deactivation of excited pigments during the dark‐light transitions. The in vivo photothermal signals measured with both techniques were shown to remain constant during induction of photosynthesis under high light conditions, suggesting that, in contrast to current hypotheses, energy‐dependent quenching qE is not associated with significant changes in thermal dissipation of absorbed light energy in the chloroplasts. When photosynthesis was induced with a low‐intensity modulated light, a noticeable decrease in the heat emission yield was observed resulting from the progressive activation of the competing photochemical processes. Copyright © 1990, Wiley Blackwell. All rights reserved
TL;DR: In this paper, the cross calibration of two optical detection techniques for the monitoring of laser-generated Lamb waves is described for the measurement of Lamb waves using an optical beam deflection technique and those using a Michelson interferometer technique.
Abstract: The cross calibration of two optical detection techniques is described for the monitoring of laser‐generated Lamb waves. Measurements of Lamb waves using an optical beam deflection technique are compared with those using a Michelson interferometer technique. Analysis shows that phase changes in acoustic waveforms relate to the physical characteristics of the two detection schemes. Results are self‐consistent, and show that the beam deflection technique is capable of providing quantitative waveform analysis.
TL;DR: By estimating the value of the thermal diffusion length of the powdered sample and those of the extinction coefficients of the most relevant Photofrin II components in the spectral region considered, the local drug concentration was evaluated and a value was determined that is in the range expected for the dose of Phot ofrin II injected.
TL;DR: Results of FTIR‐PAS measurements of known quantities of microbial mass in simulated growth experiments suggest that the technique may be especially suitable for assays of microorganisms used in solid‐state biosyntheses of drugs, hormones, and other biological agents.
Abstract: A relatively new analytical technique, Fourier transform infrared-photoacoustic spectroscopy (FTIR-PAS), provides spectra of bacteria, fungi, and other microorganisms in solid states not suitable for conventional absorption spectroscopy In this paper the feasibility of quantitative measurement of protein biomass on solid substrates by FTIR-PAS is examined and discussed By measuring photoacoustic absorption bands from amide groups in the protein of microorganisms, the increase in biomass that occurs during growth was monitored directly and accurately Incorporation of polyacrylonitrile into the sample as an internal standard was shown to be a convenient method for improving both the reliability and the range of detection by photoacoustic spectroscopy Results of FTIR-PAS measurements of known quantities of microbial mass in simulated growth experiments suggest that the technique may be especially suitable for assays of microorganisms used in solid-state biosyntheses of drugs, hormones, and other biological agents
TL;DR: In this article, the chemical relaxation of the N2O4 dissociation using Ar+ laser excited acoustic resonances of a cylindrical cavity was studied using a computer controlled setup.
Abstract: The chemical relaxation of the N2O4 dissociation was studied using Ar+ laser excited acoustic resonances of a cylindrical cavity. The resonance profiles of the first radial mode were measured as a function of pressure and temperature by a computer controlled setup. The N2O4 dissociation rate constant and the mean rotational and vibrational relaxation time of the N2O4–NO2 mixture were obtained for temperatures between 273 and 317 K by fitting a detailed theoretical model of the resonator to the measured values for frequency dispersion, resonance broadening, and strength of the photoacoustic signal. Excellent agreement between theory and experiment was obtained for the frequency dispersion and the photoacoustic signal. An empirical correction function had to be introduced to account for discrepancies between the theoretically predicted and measured values of the resonance broadening which was in the percent region. A value of 6.1×10−15 cm3/molecule s was determined for the rate constant of N2O4 dissociation...
TL;DR: A rapid, nondestructive, reproducible liquid-bonding technique, which permits the extension of these measurements to a wide variety of samples, and major advantages include narrow-bandwidth detection and a large irradiated area that permits more optical energy on the sample.
Abstract: The sensitivity of surface-acoustic-wave detection is extended by several orders of magnitude to a surface-specific absorbance of αl ∼ 10−9 for a power density of 1 GW/cm2 using a narrow-bandwidth interdigitated surface-acoustic-wave detector and an optical irradiation pattern to provide a matched acoustic signal. Major advantages include narrow-bandwidth detection and a large irradiated area that permits more optical energy on the sample. A rapid, nondestructive, reproducible liquid-bonding technique, which permits the extension of these measurements to a wide variety of samples, is demonstrated. Results for AlN and ZrO2 films (αl ∼ 10−4) and fused-silica substrates (αl ∼ 10−6–10−7) are reported.
TL;DR: In this paper, the infrared spectra of crystalline and amorphous silica particles of different sizes (0.05, 5, 10, 15, 30, 45, and 260 μm) in the range of 400-4000 cm -1 using Fourier transform infrared/photoacoustic spectroscopy are reported.
Abstract: Investigations of the infrared spectra of crystalline and amorphous silica particles of different sizes (0.05, 5, 10, 15, 30, 45, and 260 μm) in the range of 400-4000 cm -1 using Fourier transform infrared/photoacoustic spectroscopy are reported. The change in the intensity I of the signal with porosity ∈ of powders follows the ∈/(1-∈) dependence for strong bands and ∈ dependence for weaker bands are predicted by the theory of McGovern et al. For strong bands, I also follows the empirical relation I∼D -n , where D is the particle diameter in cm and n=0.34-0.42
Journal Article•
TL;DR: In this paper, a method to determine large optical absorption coefficients of liquids from the amplitude ratio of acoustic waves generated under rigid and free-boundary conditions is presented, taking into account the attenuation of the pulse amplitude ratio with the increased acoustic path length due to attenuation effects.
Abstract: A method to determine large optical absorption coefficients of liquids from the amplitude ratio of acoustic waves generated under rigid‐ and free‐boundary conditions is presented. This has been examined both experimentally and theoretically, taking into account the attenuation of the pulse amplitude ratio with the increased acoustic path length due to attenuation effects. Although the proposed method was tested in a narrow wavelength interval and close to the limit of precision of the experimental arrangement, the results show quantitative agreement with the literature values.
01 Feb 1990
TL;DR: In this paper, the principles of photoacoustic spectroscopy are outlined and a new and still developing technique enables one to detect non-radiative de-excitation processes, which is possible to distinguish between signals emenating from different depths of the sample.
Abstract: The principles of photoacoustic spectroscopy are outlined. This new and still developing technique enables one to detect non-radiative de-excitation processes. It is possible to distinguish between signals emenating from different depths of the sample. In plant science photoacoustic spectroscopy has mainly been applied in photosynthesis research. Here it allows the detection of gross oxygen evolution and gives information about the energy balance of the primary photosynthetic reaction.
TL;DR: An overview of the theory of photoacoustics and its application in photosynthesis research to measure energy conversion and storage, and for molecular structure and interaction studies as well as oxygen evolution in photosynthetic systems is given in this article.
TL;DR: In this paper, a laser-induced photoacoustic spectroscopy was applied in order to determine trace amounts of iron adsorbed onto the surface of a solid resin Amberlite XAD-2 microparticle of 300μm in diameter as an oxine (8-quinolinol) complex.
Abstract: Laser-induced photoacoustic spectroscopy was applied in order to determine trace amounts of iron adsorbed onto the surface of a solid resin Amberlite XAD-2 microparticle of 300μm in diameter as an oxine (8-quinolinol) complex. The photoacoustic measurements were carried out with a single particle in order to avoid any scattering effects. The signal magnitude depended on the iron concentration, which ranged from 5×10-3 to 3mg for one gram of resin. This dependence deviated from linearity as the concentration became larger than 40μg per gram of resin. The nonlinear behavior was regarded as being a saturation phenomenon resulting from the spatial variation of the optical thickness due to the sample′s spherical form. The saturation effect could be eliminated by focusing the incident beam to a size sufficiently small with respect to the particle diameter.
TL;DR: In this article, the results of combined optical and photoacoustic spectroscopy measurements and electron spin resonance measurements (ESR) in binary alloys are reported, and the densities of spins as obtained by ESR measurements are correlated with the values of integrated absorption in the low energy range.
TL;DR: A piezoelectric detection system for recording photoacoustic spectra of materials in the condensed phase obtained new information on the Stark components of the ground and excited states of Ho(3+) and Nd( 3+) in the oxide matrix.
Abstract: A piezoelectric detection system for recording photoacoustic (PA) spectra of materials in the condensed phase was designed and fabricated. A Nd-YAG laser pumped tunable dye laser with a bandwidth of 0.05 nm was used for recording the fine structure of bands in the region between 610-680 nm in powdered microcrystalline samples of Ho(2)O(3) and Nd(2)O(3). Analysis of high resolution photoacoustic spectra obtained new information on the Stark components of the ground and excited states of Ho(3+) and Nd(3+) in the oxide matrix.