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It is simulated that the photoacoustic effect in three-dimensional model to compare photoacoustic effect with attenuated different Gaussian radii distribution light sources by the finite element method (FEM). We motivate the enclosed photoacoustic cell at a range of frequencies and compare the results of the amplitude of acoustic pressure frequency curve, the distribution of acoustic pressure and the variation of temperature within the gas layer.

A double-purpose open photoacoustic cell, suitable for optical and thermal characterization of liquid samples is described. An experimental method for the determination of very low concentrations of contaminants in liquid substances is proposed. The proposed technique was used to determine the concentration of Chromium (VI) in water via the measurement of its optical absorption coefficient. To test the suitability of the proposed technique for experimental determination of thermal properties of liquids, studies on ethanol were performed. The agreement between experimentally obtained thermal properties and values reported in the literature is good.

Mathematical formulization of the thermal response in a two-layer photoacoustic cell, where the interference of thermal waves in a sample is compounded by the inter-layer interference effect, has been carried out by employing the thermal-wave interference theory. The physical meanings of the obtained formulae are then discussed in terms of the thermal-wave interference to explain the origin of the thermal phase lag for various cases. In addition, it is found that the inter-layer thermal-wave interference results in an extra phase lag.

The design and construction of a novel cryogenic cell which may be used to carry out photoacoustic measurements on either opaque or transparent samples are described. The design allows any temperature to be employed within 0.5 K. Results for graphite test samples show the expected inverse frequency dependence of the photoacoustic signal, increase in signal with decreasing temperature and resonance effects at low temperature.

The open photoacoustic cell (OPC) technique is applied to photosynthesis research in leaves, where the leaf is still attached to the plant. It is shown that real in situ and in vivo measurements of photosynthetic activities in leaves can be performed. The dehydration effect after cutting the leaf from the plant was monitored and some qualitative measurements related to photosynthetic activities are reported in order to show the usefulness of this technique in this field.

Real time, high-sensitivity and interference-free Stark-tuned photoacoustic concentration detection of atmospheric pollutants at CO2 laser wavelengths requires subatmospheric pressures in the cell containing the gaseous sample of interest. The detected photoacoustic signal is in general directly proportional to the cell responsivity, a definition which implies, among the other parameters, the product of the microphone sensitivity and the absorption cross section of the measured species. For correct interpretation of the results it is necessary to determine the dependence of both of these quantities on pressure. A novel effective methodology is proposed, making no use of a test gas and based on a vibrating strip as the calibrating source. Once the cell responsivity has been determined the method described can be used to study the pressure dependence of the absorption cross section of an arbitrary gas.

The possibility of using a minimal-volume photoacoustic cell to perform spectroscopy of samples is discussed. It is shown that this alternative signal-to-noise-enhanced photoacoustic configuration allows one to obtain both absorption and transmission spectra with minimal experimental arrangement and cell machining requirements. The theoretical model is presented, the use of which is exemplified by a complete optical and thermal characterization of leaves.

A method for determination of the thermal diffusivity of the solid phase of porous samples, based on frequency-dependent scattering of optically induced thermal waves, is presented. The surface temperature variation of powder-metallurgic Fe samples, due to modulated laser heating, was detected by a photoacoustic cell in the frequency range 30-320 Hz. The thermal diffusivity values obtained from comparison with a theoretical model (Appl. Phys. A 54 6 (1992)) are close to those of a homogeneous sample.

We have developed an ink thickness sensor by employing a photoacoustic technique in order to enable the online measurement of ink thickness for printing machines such as a sheet-fed press. This sensor enables the online measurement of black ink thickness, which was impossible using the conventional methods. In order to detect the photoacoustic signals from the ink on a rotating ink roller using a non-contact technique, the halogen light chopping frequency was made to coincide with the pipe acoustical resonance frequency of the photoacoustic cell. With this method, even though the photoacoustic cell is an open cell, the sensitivity of the photoacoustic cell could be improved as compared to the conventional non-resonant closed cell. Further, it was clarified both experimentally and theoretically that the photoacoustic signal strength of black ink corresponds to an ink film thickness when the optimum halogen light chopping frequency is selected. In addition, a study is made on the characteristics of the photoacoustic signal strength variation for the clearance between the resonance tube and the ink roller.

A resonant photoacoustic cell which allows for amplitude and phase measurements over a wide temperature range is described. Photoacoustic measurements prove to be highly sensitive for the study of phase transitions in solids as well as the behaviour of the thermal conductivity. An application to the ferroelectric-incommensurate (N(CH3)4)2CoCl4 is carried out.

A conventional photoacoustic measurement cell is compared with the newly developed acoustic window photoacoustic window cell both theoretically and experimentally using liquid and power samples. The results indicate that the signal strengths from the two cell types are about equal for liquid samples in practical cells. This is important since the acoustic window cell was developed with applications to on-line analysis of liquids in mind. When powder samples are used in the acoustic window cell saturation effects can be important, and it is possible that the acoustic window cell can be used on powder samples with low light absorption.

The transmission matrix method is used to obtain the acoustic transfer function of a photoacoustic (PA) cell. The acoustic transfer function can describe accurately the resonances of all components of a PA cell in terms of a transfer impedance with some criteria. The results show good agreement with the theoretical prediction regarding f-1 dependence in the low frequency region, the longitudinal resonances in the neck and the transverse mode resonances in the cavity.

An acoustically-resonant photoacoustic cell has been designed which is useful for optical spectroscopy and trace analysis for liquid samples. The cell is simple, easy to use and corrosion-free. Acoustic characteristics of the cell are described. High sensitivity is demonstrated by detecting a small amount of permanganate ion (MnO4 -) with the concentration down to 8×10-8 M.