Showing papers on "Photoacoustic spectroscopy published in 1982"
TL;DR: In this paper, the effect of the direct continuous light depends on the modulation frequency: a decrease in the photoacoustic signal, "negative effect" is observed at low frequency (under approx. 200 Hz) and an increase of the photoACoustic signal (positive effect) at high frequency (above approx 200 Hz). Both effects are reversible.
177 citations
TL;DR: It is shown that while the photothermal signal is significantly affected in the case of highly scattering media, it is independent of scattering for optically thin samples, e.g., photoacoustic and photothermal deflection.
Abstract: We present a general unified theoretical analysis of the role of scattering in photothermal spectroscopy, e.g., photoacoustic and photothermal deflection. We show that while the photothermal signal is significantly affected in the case of highly scattering media, it is independent of scattering for optically thin samples. Numerical estimates of the scattering contribution and comparison with experimental results are given. We also elucidate the relationship between photothermal and diffuse reflectance spectroscopies.
96 citations
TL;DR: In this article, the authors used infrared spectrograms, ultraviolet absorbance spectrometers, photoacoustic spectroscopy, and photoacoustical spectrometer to obtain useful information about an immobilized acetoacetamide formed by reacting diketene with either aminopropylsilane or (aminoethyl) aminoethyl polysilane.
Abstract: Infrared spectometry, ultraviolet absorbance spectrometry, photoacoustic spectroscopy, and solid-state /sup 13/C NMR spectrometry have in combination produced useful information about an immobilized acetoacetamide. The immobilized acetoacetamide formed by reacting diketene with either aminopropylsilane or (aminoethyl)aminopropylsilane bound to silica gel is strongly hydrogen bonded and largely in the keto form. The keto form can be converted to the enolate ion only in very alkaline conditions. In weakly acidic solutions the keto form complexes with several metal ions.
68 citations
62 citations
TL;DR: Pressure dependency in the 10P C(12)O(2)(16) range was studied for various concentrations of ethylene, and a method for relating ethylene pressure-dependency data on absorption to molecular structure was examined.
Abstract: Absorption coefficients have been measured for ethylene in the 9- and 10-μm range with a photoacoustic spectrophone. Pressure dependency in the 10P C12O216 range was studied for various concentrations of ethylene. Comparisons of the data with other measurements of both atmospheric and pressure-dependent absorption coefficients were also made, and a method for relating ethylene pressure-dependency data on absorption to molecular structure was examined. Typical discrepancies between up to six independent measurements of ethylene absorption were 38.1% at the 10-μm R(20) line, 4.4% at the 10-μm P(18) line, and 18.5% at the 10-μm P(26) laser line.
51 citations
49 citations
TL;DR: Absorption and dichroism measurements using Fourier transform spectroscopy and Mirage detection are found to be 3 orders of magnitude more sensitive than conventional photoacoustic spectroscopic measurements.
Abstract: Absorption and dichroism measurements using Fourier transform spectroscopy and Mirage detection are found to be 3 orders of magnitude more sensitive than conventional photoacoustic spectroscopy.
47 citations
TL;DR: The acoustic transfer function of resonant PA cells is investigated experimentally and theoretically in the 10-300-K temperature range in the scope of a generalized Helmholtz resonator model, which includes elements of acoustic transmission lines.
Abstract: The acoustic transfer function of resonant PA cells is investigated experimentally and theoretically in the 10–300-K temperature range. The underlying cell design consists of two cavities that are interconnected by a cylindrical tube. The acoustic properties are treated in the scope of a generalized Helmholtz resonator model, which includes elements of acoustic transmission lines. For the low-temperature measurements the cell construction was modified to fit into a commercial optical cryostat. Photoacoustic signals are recorded from carbon and graphon samples as a function of the chopping frequency and of the temperature. With decreasing sample temperature the photoacoustic signal amplitude increases proportional to T−2.75, as the phase angle and the resonance frequencies are simultaneously reduced.
47 citations
46 citations
TL;DR: In this paper, the qualitative dependence of the tetrahedral ion fraction and octahedral metal ion fraction on metal loading and calcination temperature was examined using photoacoustic spectroscopy.
44 citations
TL;DR: The appearance of longer wavelength absorption bands in senescent wheat is the result of accumulated photochemical modifications of the ligin polymer, demonstrating photoacoustic spectroscopy to be an important new tool for the investigation of insoluble plant components.
Abstract: Photoacoustic spectroscopy is a recently developed nondestructive analytical technique that provides ultraviolet, visible, and infrared absorption spectra from intensely light scattering, solid, and/or optically opaque materials not suitable for conventional spectrophotometric analysis. In wood and other lignocellulosics, the principal ultraviolet absorption bands, in the absence of photosynthetic pigments, arise from the aromatic lignin component of the cell walls. Photoacoustic spectra of extracted lignin fragments (milled wood lignin) and synthetic lignin-like polymers contain a single major absorption band at 280 nanometers with an absorption tail extending beyond 400 nanometers. Photoacoustic spectra of pine, maple, and oak lignin in situ contain a broad primary absorption band at 300 nanometers and a longer wavelength shoulder around 370 nanometers. Wheat lignin in situ, on the other hand, exhibits two principle absorption peaks, at 280 nanometers and 320 nanometers. The presence of absorption bands at wavelengths greater than 300 nanometers in intact lignin could result from (a) interacting, nonconjugated chromophores, or (b) the presence of more highly conjugated structural components formed as the result of oxidation of the polymer. Evidence for the latter comes from the observation that, on the outer surface of senescent, field-dried wheat culms (stems), new absorption bands in the 350 to 400 nanometer region predominate. These new bands are less apparent on the outer surface of presenescent wheat culms and are virtually absent on the inner surface of either senescent or presenescent culms, suggesting that the appearance of longer wavelength absorption bands in senescent wheat is the result of accumulated photochemical modifications of the ligin polymer. These studies also demonstrate photoacoustic spectroscopy to be an important new tool for the investigation of insoluble plant components.
TL;DR: In this paper, the relative numbers of Bronsted acid to Lewis acid sites on silica-alumina have been determined photoacoustically by an infrared analysis of chemisorbed pyridine.
Abstract: Relative numbers of Bronsted acid to Lewis acid sites on silica-alumina have been determined photoacoustically by an infrared analysis of chemisorbed pyridine compared to similar adsorption of ..gamma..-alumina that has only Lewis sites. Results are similar to those obtained by earlier IR transmission studies that suggested the use of framework vibrations of silica as an internal reference standard. The 20% coverage of the silica-alumina surface by pyridine adsorbed at Bronsted sites found photoacoustically is in good agreement with a previous value of 17% estimated from transmission spectroscopic data. Reproducibility of the photoacoustic measurements is excellent.
TL;DR: In this article, a normalization procedure for IR-photo-acoustic spectroscopy spectra of solids and liquids is discussed and applied to experimental data obtained on polymeric samples.
Abstract: Photoacoustic spectra of materials obtained using the Fourier transform technique require normalization to achieve correct relative peak heights over the spectral range studied. This paper discusses procedures for obtaining quantitative Fourier transform IR-photoacoustic spectroscopy spectra of solids and liquids. A normalization routine for absorption amplitudes is discussed and applied to experimental data obtained on polymeric samples.
TL;DR: The single-pulse photoacoustic technique was used to measure cross sections for IR multiphoton absorption and the source of the signals from the microphone was identified.
Abstract: The single-pulse photoacoustic technique was used to measure cross sections for IR multiphoton absorption. A discussion of this technique and the applicable pressure range is given. The source of the signals from the microphone was identified. The first peak is proportional to the energy absorbed by the gas in the focal region, while the subsequently arriving signals correspond to a mixture of the signal from the entrance and exit volumes and the ringings of the microphone and the gas cell.
TL;DR: Intracavity gas-phase photoacoustic spectroscopy is used to study the near IR and visible overtone spectra of propylene, 2- butene, 2,3-dimethyl-2-butene, acetone,2- butanone, and 3-pentanone.
Abstract: Intracavity gas-phase photoacoustic spectroscopy is used to study the near IR and visible overtone spectra of propylene, 2-butene, 2-methyl-2-butene, 2,3-dimethyl-2-butene, acetone, 2-butanone, and 3-pentanone. The spectra are described in terms of the local-mode theory of vibrations as the absorption of loosely coupled anharmonic C–H oscillators within the molecule.
TL;DR: In this article, Fourier transform IR photoacoustic (FT-IR-PAS) dichroism studies have been applied to determine molecular orientation from the surface of one-way drawn poly(ethylene terephthalate) film.
Abstract: Fourier transform IR photoacoustic (FT-IR-PAS) dichroism studies have been applied to determine molecular orientation from the surface of one-way drawn poly(ethylene terephthalate) film. When compared with attenuated total internal reflectance (ATR) dichroic spectra obtained with a modified, rotatable sample holder on the same sample, photoacoustic (PA) spectra show saturation effects in strong absorption bands near 1730, 1250, and 1100 cm−1, probably due to the greater penetration depth in the PA technique. The dichroic ratios (kx/ky) on the plane of the sample film have been calculated from PA spectra, only on bands which do not show saturation and compared with the analogous ratios determined from ATR dichroic spectra. For three well-known parallel bands at 1335, 975, and 795 cm−1 the dichroic ratio is greater than unity in both ATR and PAS, as expected from the drawing process. In general, somewhat lower dichroic ratios are observed by PA spectra than by ATR spectra with this sample. Possible reasons for this trend are discussed. This study demonstrates the potential of FT-IR-PAS dichroism as a complementary technique to ATR dichroism, especially on samples with rough or brittle surfaces.
TL;DR: In this paper, a Fourier transform spectrometer built with a photothermal beam deflection detector was used to record infrared spectra of organic and inorganic solids, and the total absence of sample-containing devices makes it possible to examine portions of the surfaces of objects which are very large in size.
Abstract: Infrared spectra were recorded of organic and inorganic solids with a Fourier transform spectrometer built to operate with a photothermal beam deflection detector. No sample preparation or cells per se is needed to examine milligram quantities of powder. The total absence of sample-containing devices makes it possible to examine portions of the surfaces of objects which are very large in size. Sample heating may occur, so that care must be taken with heat-sensitive materials.
TL;DR: Syracuse University was able to detect NO/sub 2/ at concentrations as low as 2 ppb in samples of air at total pressures of 1 atm, driven by fixed-frequency excitation between 406.7 and 530.9 nm as mentioned in this paper.
Abstract: The high efficiency of laser-assisted photoacoustic detection at higher pressures makes it well-suited for such applications as atmospheric pollution monitoring. Syracuse University was able to photoacoustically detect NO/sub 2/ at concentrations as low as 2 ppb in samples of air at total pressures of 1 atm. Driven by fixed-frequency excitation between 406.7 and 530.9 nm, the photoacoustic signal was linear over approximately 6 orders of magnitude in NO/sub 2/ pressure. The instrumentation was optimized with respect to the generation and propagation of photoacoustical signals under conditions simulating those found in the environmental monitoring of real, captured air samples. The experiment design considered the simplicity of the instrumentation as well as its performance capabilities.
TL;DR: The photoacoustic spectrum (PAS) was measured in the near IR region (1000 to 2600 nm) for organic compounds (C 6 H 6, C 6 D 6, C 7 H 8, and C 6 H 12 ) as discussed by the authors.
TL;DR: In this paper, it was shown that the photoacoustic spectrum of a strongly fluorescing compound which gives a poor photo-acoustic response is very sensitive to the presence of another compound with low fluorescence quantum yield.
Abstract: It is demonstrated that the photoacoustic spectrum of a strongly fluorescing compound which gives a poor photoacoustic response is very sensitive to the presence of another compound with low fluorescence quantum yield. Deliberate addition of such compounds can assist in detection and identification of compounds of low ’’photoacoustic yield.’’ It is also shown that photoacoustic spectroscopy is well suited to the study of energy transfer to acceptor molecules, which have a negligible fluorescence quantum yield.
TL;DR: In this article, the photoacoustic effect with solids has been investigated in the context of analytical applications of PAS in the field of photo-acoustic spectroscopy.
Abstract: Since the revival of interest in the photoacoustic effect with solids, prompted by Rosencwaig's work,1 most papers dealing with the analytical applications of photoacoustic spectroscopy (PAS) have ...
Patent•
25 May 1982
TL;DR: In this paper, a portable device for photoacoustic spectroscopy of plants and other photosynthetic tissues, cells and organelles is provided, and a method of measuring photosynthesis of such tissues and cells is further provided.
Abstract: A portable device for photoacoustic spectroscopy of plants and other photosynthetic tissues, cells and organelles is provided. There is further provided a method of measuring photosynthesis of such tissues, cells and organelles.
TL;DR: CO(2) laser absorption cross-section data are reported for acrolein, styrene, ethyl acrylate, trichloroethylene, vinyl bromide, and vinylidene chloride, indicating that sub parts per billion level, interference-free detection limits should be possible for these compounds by the CO( 2) laser photoacoustic technique.
Abstract: CO2 laser absorption cross-section data are reported for acrolein, styrene, ethyl acrylate, trichloroethylene, vinyl bromide, and vinylidene chloride. These data indicate that sub parts per billion level, interference-free detection limits should be possible for these compounds by the CO2 laser photoacoustic technique. Photoacoustic detectabilities below 40 ppb should be possible for these compounds in the presence of ambient air concentrations of water vapor and other anticipated interferences. These compounds are also found not to be important interferences in the detection of toxic hydrazine-based rocket fuels by CO2 laser spectroscopic techniques.
TL;DR: In this article, a method for the polarization of an electret foil has been described, which has proved very convenient and yields a foil having very good performance in a microphone, and the working of this type of microphone and its comparison with a commercial microphone as used in a (laboratory made) single beam photoacoustic spectrometer is discussed.
Abstract: We describe a new method for the polarization of an electret foil which has proved very convenient and yields a foil having very good performance in a microphone. The variations in the charge accumulation on the electret foil and its decay with time as well as the variation of the microphone sensitivity with different microphone parameterse.g. different thicknesses of the electret foil, different back plates and different polarization techniques has been investigated. The sensitivity of the home-made microphone is estimated as 1 mV/μbar. The working of this type of microphone and its comparison with a commercial microphone as used in a (laboratory made) single beam photoacoustic spectrometer is discussed.
TL;DR: In this article, infrared photothermal deflection spectra were recorded of single crystals and powders of calcite and (NH 4 ) 2 SO 4, SiC powders, of a 58% Ni-on-kieselguhr catalyst and of oxidized carbon.
TL;DR: The photoacoustic signal phase spectra have been also measured; they are shown to be a useful check of the structures observed in the magnitude saturation spectra as mentioned in this paper, and the experimental results are in good agreement with the allowed interband transition energies as observed in thermo-reflectance, electroreflectance and normal reflectivity experiments.
TL;DR: In this article, a surface analysis of the corrosion products formed on iron metal exposed to off gas from a HCN production process has been performed, and the results showed that the surface iron was divalent, coordinated to cyanide, and no iron(II) oxide was present.
Abstract: Surface analysis of the corrosion products formed on iron metal exposed to off gas from a HCN production process has been performed. The atmosphere contains HCN(g), NH3(g), and H2O(g) plus other trace gases. Iron gratings exposed to the atmosphere form a dark blue coating which pits the surface of the iron. Samples of the corroded iron surface were analyzed by FT-IR/photoacoustic spectroscopy (PAS) and x-ray photoelectron spectroscopy (XPS or ESCA). The mid-IR spectrum from PAS yielded peaks due to NH4+, CN−, and H2O. ESCA analysis confirmed that the surface iron was divalent, coordinated to cyanide, and no iron(II) oxide was present. Relative quantitation from ESCA showed a 1:4 ratio of NH4/CN type nitrogen, thus a specific single stoichiometry was not postulated for the corrosion product. Peak positions of the cyanide stretching frequencies suggest a mixed ferro(ferrocyanide) complex, with some ammonium as a counterion. This study illustrates the detailed structural information obtainable from FT-IR/PAS with ESCA and the applicability of FT-IR/PAS to corrosion problems.
TL;DR: A photoacoustic cell has been developed in the form of an elliptical cylinder in which essentially all the acoustic energy generated by a laser beam passing down one axis is focused onto a cylindrical acoustic transducer located along the other axis.
Abstract: A photoacoustic cell has been developed in the form of an elliptical cylinder in which essentially all the acoustic energy generated by a laser beam passing down one axis is focused onto a cylindrical acoustic transducer located along the other axis. Preliminary measurements on a liquid-filled cell of this design show high sensitivity and a notably clean impulse response. A similar design may be useful for photoacoustic measurements in vapors as well.
Journal Article•
TL;DR: This study illustrates the detailed structural information obtainable from FT-IR/PAS with ESCA and the applicability of FT- IR/ PAS to corrosion problems and the specific single stoichiometry was not postulated for the corrosion product.
Abstract: Surface analysis of the corrosion products formed on iron metal exposed to off gas from a HCN production process has been performed. The atmosphere contains HCN(g), NH3(g), and H2O(g) plus other trace gases. Iron gratings exposed to the atmosphere form a dark blue coating which pits the surface of the iron. Samples of the corroded iron surface were analyzed by FT-IR/photoacoustic spectroscopy (PAS) and x-ray photoelectron spectroscopy (XPS or ESCA). The mid-IR spectrum from PAS yielded peaks due to NH4+, CN−, and H2O. ESCA analysis confirmed that the surface iron was divalent, coordinated to cyanide, and no iron(II) oxide was present. Relative quantitation from ESCA showed a 1:4 ratio of NH4/CN type nitrogen, thus a specific single stoichiometry was not postulated for the corrosion product. Peak positions of the cyanide stretching frequencies suggest a mixed ferro(ferrocyanide) complex, with some ammonium as a counterion. This study illustrates the detailed structural information obtainable from FT-IR/PAS with ESCA and the applicability of FT-IR/PAS to corrosion problems.