Photoacoustic theory including energy migration

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Abstract
All theories of the photoacoustic effect to date have assumed that heat is deposited in the sample only where light is absorbed, i.e., that no spatial migration of the energy occurs. We present here an extension of the standard Rosencwaig-Gersho photoacoustic theory, taking into account the possibility of spatial energy migration. Also included in the theory are the effects of surface quenching, i.e., the possibility that excitations near the surface of the sample decay more efficiently than excitations in the bulk. By comparing the experimentally determined chopping frequency dependence of the photoacoustic signal to that predicted by the theory, it should be possible to determine the diffusion constant for energy migration.