Photoacoustic signal dependence on sample-backing thermal resistance

This paper presents theoretical analysis of the dependency of photoacoustic cell response excited with a modulated laser beam on the quality of thermal contact between the sample and the backing. Periodic changes of the solid sample temperature, resulting from absorption of a modulated laser beam warm up gas surrounding the sample. Changes of gas temperature are transferred into changes of its pressure, as the result of thermodynamic processes in the gas filling photoacoustic cell and are detected with a microphone in a typical photoacoustic experiment. Presence of thermal resistance substantially increases temperature inside the cell in the low frequency range of excitation beam, compared to the case when boundary conditions take into account only continuity of temperature and heat flux at the sample-backing interface.