Showing papers on "Photoacoustic spectroscopy published in 1991"
81 citations
TL;DR: In this paper, the use of step-scan Fourier transform infrared (FT-IR) spectroscopy with photoacoustic (PA) detection for depth profiling studies of polymer laminates is demonstrated.
Abstract: The use of step-scan Fourier transform infrared (FT-IR) spectroscopy with photoacoustic (PA) detection for depth profiling studies of polymer laminates is demonstrated. Step-scan FT-IR simplifies the extraction of dept; profile information due to the single modulation frequency that can be applied over the entire spectral range. Because a single modulation frequency is generally used in step-scan FT-IR, the thermal diffusion length, μ, is constant for all wavelengths in a single scan. In addition, lock-in detection allows for easy extraction of the signal phase. Two methods of depth profiling are discussed and illustrated. The first is the conventional method of varying the probe depth by changing the modulation frequency. The other method depends on the direct use of the signal phase. The phase analysis technique is particularly useful for cleanly separating the signal due to a thin (<5 μm) surface layer from that of the bulk or substrate.
69 citations
TL;DR: In this article, chemically modified textile fabrics, fibers, and films were studied by both Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) and DRIFT.
Abstract: Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) has been applied as a near-surface analysis technique for various types of samples. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) also was reported for characterizing surface species of fibrous materials. In this research, chemically modified textile fabrics, fibers, and films were studied by both FT-IR/PAS and DRIFT. The capability of near-surface analysis for both techniques was evaluated and compared. Even though diffuse reflectance infrared spectra show an enhancement in the band intensity of near-surface species, FT-IR/PAS appears to have a much smaller sampling depth than DRIFTS. All the data demonstrate that FT-IR/PAS is a useful near-surface analysis technique for polymeric fibers and films.
32 citations
TL;DR: In this paper, the high sensitivity technique of laser photoacoustic spectroscopy and visible absorption spectrum was used to investigate the hydrolysis of Pu(VI) in perchlorate media.
Abstract: The high sensitivity technique of laser photoacoustic spectroscopy and visible absorption spectroscopy were utilized to investigate the hydrolysis of Pu(VI) in perchlorate media. Pu(VI) absorption bands in the 600 to 700 nm were characterized as a function of pH in the pH = 1-7 regime. The formation constant of the 1:1 hydrolysis complex was determined as {beta}{sub 11} = 5.2 based on observed changes in the absorption bands noted. In the pH region investigated, four distinct species were identified and evidence for the existence of polynuclear species was obtained. 13 refs., 12 figs., 2 tabs.
21 citations
TL;DR: In this article, Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) was used to investigate the effects of ultraviolet (UV) radiation on cotton cellulose.
Abstract: Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) was used to investigate the effects of ultraviolet (UV) radiation on cotton cellulose. The infrared spectroscopic data revealed that carboxylic acid was the main photo-oxidation product. It was also concluded that UV radiation was able to penetrate through the cotton fabric and caused oxidation in the bulk of the fabric. However, the highest degree of oxidation occurred in the near-surface of the fabric facing the UV radiation.
19 citations
TL;DR: In this article, the Fourier transform infra-red phase analysis photoacoustic spectroscopy FT i.r.PAPS spectra derived from the imaginary component of the uncorrected interferogram are shown to be more bulk sensitive than the corresponding spectra obtained from the real component.
15 citations
TL;DR: In this article, a novel scheme for on-line ammonia trace-gas detection, based on CO 2 laser intermodulation photoacoustic spectroscopy incorporating high voltage Stark modulation (IMPASS), is described and its sensitivity and specificity tested in a simulated atmosphere.
13 citations
TL;DR: Data in the present study confirm the concept of changes in absorption cross-section of photosystems during state transitions, and shows that state 1-state 2 transitions were demonstrated in vivo in intact sugar maple leaves by following the changes in energy storage of PS I and II.
Abstract: Using photoacoustic spectroscopy, state 1-state 2 transitions were demonstrated in vivo in intact sugar maple leaves (Acer saccharum Marsh.) by following the changes in energy storage of photosystems (PS) I and II. Energy storage measured with 650 nm modulated light (light 2) in the presence of background white light indicated the total energy stored by both photosystems (ESt), and in the presence of background far-red light showed the energy stored by PSI (ESpsi). The difference between ESt and ESpsi gave the energy stored by PSII (ESpsii). While ESt remained nearly constant during state transitions, both ESpsi and ESpsii changed considerably. The ratio of ESpsii to ESpsi, an indicator of the energy distribution between the two photosystems, decreased or increased during transition to state 2 or state 1, respectively. State transitions were completed in about 20 min and were fully reversible. During transition from state 1 to state 2, the fraction of excitation energy gained by PSI was nearly equal to that lost by PSII. This fraction of excitation energy transferred from PSII to PSI accounted for about 5% of the absorbed light (fluorescence is not considered), 19% of ESt, 34% of ESpsii, and 43% of ESpsi in state 2. NaF treatment inhibited the transition to state 1. Data in the present study confirm the concept of changes in absorption cross-section of photosystems during state transitions.
13 citations
TL;DR: Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) has been used to examine surfaces of composite solid propellants as mentioned in this paper, and a method has been developed to determine the mass per unit area of graphite on coated propellant surfaces.
Abstract: Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) has been used to examine surfaces of composite solid propellants. Depletion of crystalline energetic material from extruded surfaces, and of plasticizen from aged surfaces, has been documented. In addition, a method has been developed to determine the mass per unit area of graphite on coated propellant surfaces.
12 citations
TL;DR: In this article, the optical properties (absorption coefficients, refractive indices) and the fluorescence quantum yields of tetraphenylporphins of hydrogen, magnesium and zinc were determined, using optical absorption and photoacoustic spectroscopy.
12 citations
TL;DR: In this article, the influence of ion implantation in the thermal properties of silicon wafers at room temperature was investigated using the photoacoustic technique, and it was suggested that the observed decrease of the values of both thermal diffusivity and conductivity, as the implantation dose increases, is due to the amorphization of the implanted layer.
Abstract: The influence of ion implantation in the thermal properties of silicon wafers at room temperature is investigated using the photoacoustic technique. It is suggested that the observed decrease of the values of both thermal diffusivity and conductivity, as the implantation dose increases, is due to the amorphization of the implanted layer.
TL;DR: Photoacoustic and proton-induced X-ray emission measurements were performed on iron-enriched milk protein concentrates and the possibility of measuring Fe content by photoacoustic measurements in the visible region of the spectrum is discussed.
Abstract: Photoacoustic and proton-induced X-ray emission measurements were performed on iron-enriched milk protein concentrates. The possibility of measuring Fe content by photoacoustic measurements in the visible region of the spectrum is discussed.
TL;DR: In this article, the relative intensities of the peaks in different spectral regions indicate that PAS is the most sensitive in the near-IR region, affording good information on binary vCO and vCH overtones and combinations, while ATR spectroscopy leads to the most intense peaks in the far-IR regions.
Abstract: Photoacoustic (PA), attenuated total reflection (ATR), and transmission IR spectra of the solid organoiron(II) complexes, CpFe(CO)2I and [CpFe(CO)2R]BF4 (Cp = n5-C5H5; R = C2H4, CH2CMe2, 3-Me-thiophene), have been recorded at room temperature in the near-, mid-, and far-IR regions. Vibrational assignments are proposed for most of the observed bands including those in the binary overtone and combination regions. The relative intensities of the peaks in the different spectral regions indicate that PAS is the most sensitive in the near-IR region, affording good information on binary vCO and vCH overtones and combinations, while ATR spectroscopy leads to the most intense peaks in the far-IR region.
TL;DR: In this paper, the authors describe how, with careful selection of a reference peak, one can use the strong peak saturation characteristic of PAS/FT-IR to advantage in the quantification of small amounts of residual unsaturation in a photo-cured acrylate coating.
Abstract: The advent of Fourier transform infrared spectroscopy has allowed for the use of the photoacoustic detection technique in the infrared region of the electromagnetic spectra Urban recently described the advantages of photoacoustic Fourier transform infrared spectroscopy (PAS/FT-IR) in the characterization of polymeric coatings and interfaces at various depths at the molecular level Nonetheless, because of the strong tendency for PAS/FT-IR spectra to be distorted due to saturation of peaks with strong absorbances, PAS/FT-IR has found only limited use as a quantitative procedure In this report we describe how, with careful selection of a reference peak, one can use the strong peak saturation characteristic of PAS/FT-IR to advantage in the quantification of small amounts of residual unsaturation in a photo-cured acrylate coating
TL;DR: In this paper, a transparent LiNbO3 transducer was used to generate photoacoustic (PA) signals in semiconductor thin films, which can be used for measuring optical and thermal properties of thin films on the substrate.
Abstract: We have studied the generation mechanism of photoacoustic (PA) signals in semiconductor thin films by means of a transparent LiNbO3 transducer both experimentally and theoretically. In the transparent transducer method, the PA signal was detected at the light‐irradiated surface of the samples. The PA signal of the thin film directly attached to the transducer is mainly due to the pyroelectric effect, and the PA signal of the underlain substrate is the piezoelectric signal caused by sample bending. These results show that this method becomes a powerful tool for measuring optical and thermal properties of thin films on the substrate nondestructively.
TL;DR: Incorporation of oxygen to crystalline zeolitic chromosilicates, with oxidation of anchored CrIII to non-interacting CrVI species, has been confirmed by photoacoustic spectroscopy.
Abstract: Incorporation of oxygen to crystalline zeolitic chromosilicates, with oxidation of anchored CrIII to non-interacting CrVI species, has been confirmed by photoacoustic spectroscopy; the dichromate anion being extracted from the chromosilicate with water and identified by precipitation of AgCrO4 and oxidation to CrO5.
TL;DR: In this paper, the one-dimensional temperature moment caused by light absorption and heat diffusion was calculated to explain the basic feature of the photoacoustic signal of bonded Cu plates including an air gap detected by a PZT transducer attached to the back surface of the plate.
Abstract: The piezoelectric photoacoustic spectroscopy of multilayered structures was studied both theoretically and experimentally. We calculated the one-dimensional temperature moment caused by light absorption and heat diffusion. It was found that the temperature moment is able to explain the basic feature of the photoacoustic (PA) signal of bonded Cu plates including an air gap detected by a PZT transducer attached to the back surface of the plate. The phase of the PA signal at low frequencies is very sensitive to the thickness of the air gap between two Cu plates.
TL;DR: In this paper, electron energy loss spectroscopy (EELS) was used to study the electronic structure of small Ag, In and Au particles, deposited on thin carbon foils, quartz supports or as self-supporting layers, respectively.
Abstract: Electron energy loss spectroscopy (EELS) in a transmission electron microscope (TEM) and photoacoustic spectroscopy (PAS) has been used to study the electronic structure of small Ag, In and Au particles, deposited on thin carbon foils, quartz supports or as self-supporting layers, respectively.In the low energy-loss region the EELS spectra of Ag particles with diameters of ca. 50 nm are different from the spectra of the homogeneous Ag layers, mainly owing to the influence of the carbon foil. By decreasing the packing density of the Ag particles, a shift of the plasma losses to lower energies is observed in the energy region 10 eV. The optical behaviour of homogeneous metallic and small particle layers on thin quartz supports was studied by PAS in the ultraviolet/visible (UV/VIS) spectral region. The homogeneous layers, e.g. of Ag, show, in the UV range, the well known change of reflectance due to an interband transition of bare silver. For Ag particle layers surface plasma resonances are excited. With increasing packing density of the particles the absorption peak observed is red-shifted and becomes broader, whereas the results of EELS in the low energy-loss region revealed a shift to higher energies.To obtain additional information investigations of In and Au particles were performed.
TL;DR: In this paper, a broad band LN2 cooled CW CO laser was used as a source of radiation, which operates from 4.8-8.4 um in the mid-infrared.
Abstract: Detection of COCl2, a highly toxic gas in chemical industry, using laser photoacoustic spectroscopy is presented. The spectrophone system used has a broad band LN2 cooled CW CO laser as a source of radiation, which operates from 4.8–8.4 um in the mid-infrared. Using an extracavity open longitudinal resonant cell, absorption signals to about 30 CO laser lines in the 5.45 um region could be observed. detection sensitivity has been estimated to be ppb order.
TL;DR: The interaction of amorphous silica particles with several hydrogen bonding agents (H2O, C2H5OH, C7H8NO) was investigated by monitoring the changes in the bulk and surface IR vibrational modes of silica using photoacoustic spectroscopy as discussed by the authors.
Abstract: The interaction of amorphous silica particles with several hydrogen bonding agents (H2O, C2H5OH, C7H8NO) was investigated by monitoring the changes in the bulk and surface IR vibrational modes of silica using photoacoustic spectroscopy. It is argued that the intensity of the silanol band at 3747 cm−1 provides (an inverse) quantitative measure of the interaction of surface groups, along with the shift in the broad hydroxyl band, the interaction following the order C7H8NO > C2H5OH > H2O.
IBM1
TL;DR: In this paper, the physical basis for signal generation and enhancement, as well as noise sources and reduction schemes for pulsed and continuous-modulated excitations, are considered, and various considerations of noise suppression and signal enhancement are essential to exploit photothermal spectroscopy.
Abstract: Photothermal spectroscopy has emerged as a popular spectroscopic technique over the past decade because it is convenient and sensitive. It is convenient since a wide range of samples of all phases from highly opaque, light- scattering or reflective to highly transparent materials can be measured to some level of accuracy over a broad spectral range with little or no sample preparation. It is sensitive since, in principle, it is a 'zero background' technique, unlike the tradition extinction technique to measure absorption. However, in practice, various sources of noises become significant when the absorption approaches the part-per-million level or below, and various considerations of noise suppression and signal enhancement are essential to exploit photothermal spectroscopy, in particular, photoacoustic spectroscopy and probe-beam deflection spectroscopy. The authors consider here the physical basis for signal generation and enhancement, as well as noise sources and reduction schemes for pulsed and continuous-modulated excitations. Examples of experimental techniques are given to illustrate the points
TL;DR: In this article, the hard x-ray spectra of CuO, Cu2O, and pure Cu metal have been measured at X-ray absorption near-edge structure (XANES) regions with a photoacoustic detector using synchrotron radiation.
Abstract: The hard x‐ray spectra of CuO, Cu2O, and pure Cu metal have been measured at x‐ray absorption near‐edge structure (XANES) regions with a photoacoustic detector using synchrotron radiation. It is shown that the information derived from XANES is also included in the x‐ray photoacoustic spectrum which reflects the heat production processes in those copper oxides and metal. However, the results showed that the increases and changes of the photoacoustic signal were different from those of the x‐ray absorption coefficient at the photon energy regions.
01 Jan 1991
TL;DR: In this article, a new procedure for the determination of the absorption coefficient using coupled amplitude and phase photoacoustic spectra, measured on two different modulation frequencies, is demonstrated, and the possibility of this procedure, using semiconducting sample, is analyzed.
Abstract: The procedure for the quantitative determination of absorption coefficient is a very important problem in the application of the photoacoustic method as a quantitative spectroscopic technique. In this work, a new procedure for the determination of the absorption coefficient using coupled amplitude and phase photoacoustic spectra, measured on two different modulation frequencies is demonstrated. The possibility of this procedure, using semiconducting sample, is analyzed. The photoacoustic results are compared with those obtained using a classical optical absorption method for the same sample.
TL;DR: In this article, photoacoustic (PA) measurements were carried out on a specimen of silver, where the light beam was chopped mechanically by a light chopper and periodic pressure fluctuations, induced by thermal changes via nonradiative inactivation in the working electrode, were detected with a piezoelectric detector.
TL;DR: In this paper, the nonradiative recombination process in Cd1-xMnxTe of x=0.4 and 0.6 was studied in highly sensitive photoacoustic spectroscopy.
Abstract: Nonradiative recombination processes have been studied in Cd1-xMnxTe of x=0.4 and 0.6 by highly sensitive photoacoustic spectroscopy. The photoacoustic spectrum is found to be extended deeply into the energy-band-gap region by 150-300 meV and shows a remarkable decrease of the photoacoustic intensity at 2.07 eV. The results are interpreted in terms of the nonradiative recombination process which takes place in the fluctuating band-edge region of the material, and the suppression of the nonradiative process due to the energy transfer from the band electrons to the Mn ion levels. The relationship with the photoluminescence process is also discussed.
TL;DR: In this article, the conformation of the thin layer of keratin on the surface of silica gel particles was investigated by means of photoacoustic Fourier transform infrared (PA/FT-IR) spectroscopy.
Abstract: The conformation of keratin chemically bound to the surface of silica gel particles has been investigated by means of photoacoustic Fourier transform infrared (PA/FT-IR) spectroscopy. On the basis of the peak positions of the amide I and amide II bands, it is concluded that the keratin thin layer assumes the native α-helix form. It is also noted that the PA/FT-IR method is the only feasible method for observing the IR spectra of the very thin layer of keratin coating on the silica gel particles. The diffuse reflectance technique failed to provide any information on keratin, because of the strong spectral artifact due to the specular reflection at the surface of the silica gel.
TL;DR: In this paper, a self-transducer method based on piezo- or pyroelectric properties of the sample was proposed for photoacoustic signal detection, and an expression for the potential difference between surface electrodes was found, which depends on optical, acoustic and thermal properties of sample and intensity and modulation frequency of the light.
TL;DR: In this paper, the authors used photoacoustic detection in the entire range of CO2-laser emission for HDS and D2S IR absorption, and the strongest absorptions were found at 1045.02 cm−1 [laser line P(22] and at 971.93cm−1] [Laser line R(14], respectively.
01 Jan 1991
TL;DR: In this article, a signal generation mechanism is proposed for non-radiative de-excitation energy channels in photoacoustic (PA) and photothermal (PT) methods.
Abstract: In recent years a great deal of work has been devoted to amorphous semiconductors, the main interest concerning not only their technological potentialities, but also the investigation of their physical properties. Among the various techniques used for thin films characterization, photoacoustic (PA) and photothermal (PT) methods are now widely used. Their most prominent feature is the particular signal generation mechanism, which is directly connected to the non-radiative recombination of photoexcited carriers and therefore gives direct information on non-radiative de-excitation energy channels.