N. Muñoz, G. González de la Cruz, Yu. G. Gurevich. Departamento de Física. Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional. Apdo. Postal 17-740, 07000 México, D.F.

In these work we calculate the effective thermal parameters of two-layer structure. We used the approximation of two temperatures, when the electrons subsystem does not in equilibrium with the phonons subsystem. These model simulate the physical conditions to photoacustic experiment. In a photoacustic experiment, one face of the sample absorb a modulate laser beam radiation of low powerful. The opposite face is in contact with a gas chamber. The fluctuations of temperature in the sample provoke fluctuations of pressure into the gas, that way that, these fluctuations incite sound into the gas that is detected by a microphone. We report some particular results when the layers are thin films, that is, the cooling length is the same or larger than length of the film. The results show the properties of the effective parameters. The more important properties was that we introduced the concepts: "Static Effective Thermal Parameters" and "Dynamic Effective Thermal Parameters". About the calculations we concluded that these parameters are differents for diferents positions and exist a sensible dependence of the physical conditions of the experiment.