"Resonance" phenomena in thermal diffusion processes in two-layer structures

The dependence on the chopper frequency of the effective thermal diffusivity and effective thermal conductivity in photoacoustic experiments is discussed. The theoretical model of a two-layer structure at rear-surface illumination in the high frequency limit is considered. It is shown that the effective thermal diffusivity presents "resonance" while the effective thermal conductivity sharply changes its magnitude and sign. Such "resonant" behavior strongly depends on the surface thermal conductivities associated with the interface thermal contacts.