“…We think that the cause of this behavior is related to the limitations of the thermal piston model [1,8,30]. Namely, this model, as discussed in [27,80], presupposes that the diffusion length of heat in the gas is much smaller than the dimensions of the cells. This assumption is completely justified for harmonics whose frequency is higher than 100 Hz [1], but for lower harmonics of very long pulse excitation, whose influence becomes expressed in the long-time domain, this assumption is not justified, and for a complete analysis of the PA signal, it is necessary to use a generalized model of transformation of variations temperature at the sample/gas boundary in pressure fluctuations in a PA cell of finite length [80].…”