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.

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The photoacoustic measurement of polymer foils, typically 170--200 pm thick, is discussed. It is shown that the measurement based upon the phase lag between the front and rear illuminations is applicable only in a limited range offrequencies from 6 to 12 Hz. The dominant mechanism responsible for the photoacoustic signal, in almost the entire frequency range 10-100 Hz, is proven to be the thermoelastic bending of the foil samples. The thermal diffusivity is then obtained from the frequency dependence of the front~phase illumination data.

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The evaporation and contraction of a droplet wetting a Aat metallic surface is monitored using photoacoustic detection. The results are interpreted in terms of an effective backing model together with the lubrication theory for droplet dynamics.

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.

The kinetics of iodine doping of atactic polystyrene films is investigated using photoacoustic spectroscopy. The changes in the photoacoustically measured physical properties, such as nonradiative relaxation time and thermal diffusivity, are present as a function of the doping time. The results show strong evidence that an order-disorder transition is taking place as a function of the doping time. The suggested order-disorder transition is also evident in the dielectric constant measurements of the doped films.