Study of a Thermophysical System with Two Time Constants Using an Open Photoacoustic Cell

Abstract

In this paper a study of a thermophysical system with two time constants, an electronic time constant and a thermal relaxation time constant, is presented. The system under study is a thin metallic sample coupled to an open photoacoustic (PA) cell, the resulting signal being measured by a lock-in amplifier or by a data acquisition device. All operations are performed by a computer-based automatic measurement system. A time-and frequency-domain theoretical analysis of the photothermal signal is given combining the usual PA scheme to the energy balance equation of the system. The experimental results are in very good agreement with the developed theory.

Influence of Local Thermodynamic Non-Equilibrium to Photothermally Induced Acoustic Response of Complex Systems

“…In PA measurement, the pressure fluctuations in gaseous surrounding of the optically heated sample are recorded [1][2][3]28]. They are proportional to surface temperature variations of optically excited sample [1,[26][27][28][29][30][31]. To relate these fluctuations with sample properties it is necessary to develop the theoretical description of heat transfer across the illuminated sample and to calculate surface temperature variations based on this description.…”