Theory of Thin Layer Photoacoustic Cells for Determination of Volume Changes in Solution

Abstract

The wave equation for the photoacoustic effect generated by heat deposition and molecular volume change is solved for a one-dimensional geometry for the case of excitation of a single molecular electronic state that decays to the ground state exponentially in time. The solution for a uniformly illuminated, infinite layer of fluid in contact with two infinite fluid or solid half-spaces, corresponding to a recently developed experimental geometry for generation of the photoacoustic effect is given. The solutions show the effects of finite decay of the excited state and of reflections at the interfaces.