3-DIMENSIONAL HEAT-FLOW EFFECTS IN PHOTOACOUSTIC-SPECTROSCOPY OF SOLIDS

All theories of the photoacoustic effect in solids to date have been one dimensional, ignoring lateral heat transport to the cell walls. By studying the dependence of the photoacoustic signal on the position of focused light on the sample's surface, we have demonstrated experimentally that a three-dimensional heat-flow analysis is required in some cases, especially at low chopping frequencies. These results have implications for techniques where one measures the photoacoustic signal as a function of chopping frequency, such as the depth profiling of layered samples.