On the theory of nonlinear photoacoustic signal generation during gas-microphone detection

A theory is proposed for of the generation of the first two harmonics of a nonlinear photoacoustic signal of a solids sample with an arbitrary value of thermal conductivity. For limiting cases (thermally thin and thick samples) has been obtained simple expressions for the dependence of the amplitude of the excited photoacoustic signal from the emissivity of the sample and the thermophysical parameters of the sample, gas and substrates, including their thermal coefficients.