Chapter 2 - Physics and instrumentation of photothermal and photoacoustic spectroscopy of solids

Abstract

Photoacoustic and photothermal spectroscopy is a unique form of spectroscopy that involves detection of light-induced sound based on the absorption of electromagnetic radiation by the sample present in the form of solid, liquid, or gasses. The beauty of this technique is that it needs either a little or no sample preparation. This spectroscopy is mainly dependent on the photothermal effect. Various processes involved in the generation of photoacoustic and photothermal signals as well as its detection techniques are reviewed. A brief history, various aspect of photothermal effect, direct and indirect generation of photoacoustic signal using periodic and pulsed light sources, theory of photoacoustic signal generation for solid samples, a brief account of photoacoustic spectroscopy, as well as involved instrumentation are presented. The nonradiative decay processes and the mechanism of nonradiative energy transfer that play an important role in the generation of photothermal and photoacoustic signals are also discussed. The basic information about photoacoustic spectroscopy and related technology is important in order to better understand the physical processes involved and to enhance the photoacoustic spectroscopy signal generation for its application in different fields.