Abstract
A thermal diffusion equation has been solved using a spherical particle model, and could well explain the behavior of photoacoustic signals of a powdered sample. The solutions show the following: (1) That the optical absorption coefficient, the thermal diffusion coefficient, and the particle size have significant influences on the photoacoustic signals. (2) That the difference in photoacoustic signal among different particle sizes is caused primarily by an effect related to the surface area of a particle for a small optical absorption coefficient. (3) That, further, the effect of the surface temperature of a particle becomes important as the optical absorption coefficient increases. These consequences have been verified by experiments with powdered samples of chromium(III) potassium sulfate 12-water, CrK(SO4)2•12H2O, and its mixed crystals with aluminum potassium sulfate 12-water, AIK(SO4)2•12H2O.
