Analytical Model for Pulsed-Laser Induced Mode-Mismatched Dual-Beam Thermal Lens Spectroscopy in Liquids.

Analytical models are very important to understand physical, chemical, and biological phenomena. In many cases, obtaining an analytical model is a complex, even an impossible task. In this work, an analytical model for thermal lens spectroscopy has been developed. The model considers light absorbing liquids, a laser pulsed beam as the heat source, timescale thermal regime, and small phase change produced by heating. A simplification for low-absorption samples is obtained. A complete theoretical study of their utilization is shown. Measurements of the thermal diffusivity of water-ethanol sample mixtures in the liquid phase are analyzed. These values for pure substances are in good agreement with those reported in the literature. Our methodology could be very useful in the analysis of the optical and thermal properties of liquids.