Theory of threehyphen;dimensional photoacoustic effect with solids

摘要

The photoacoustic signal from a finite cylindrical solid sample under excitation by an arbitrary incident source is derived and is in general a complicated function of the beam profile, optical, thermal, and geometrical properties of the gas, sample, and backing material in the cell. For sufficiently high chopping frequency or for a sample with large lateral dimension, the signal is similar to its onehyphen;dimensional counterpart. Departure from onehyphen;dimensional theoretical predictions occurs at chopping frequency for which the lateral dimension is of the order of the thermal diffusional length of the gas. Spot size plays a relatively insignificant role in affecting the signal. These predictions as well as quantitative calculations based on the present theory are in agreement with several recently reported experiments.