Introduction

Photothermal spectroscopy is a group of high sensitivity methods used to measure optical absorption and thermal characteristics of a sample. There are a variety of methods used to monitor the thermal state of the analytical sample. Direct calorimetric or thermometric methods use temperature transducers to measure analytical sample temperature. Pressure transducers are used to monitor the pressure wave associated with rapid sample heating. Photothermal interferometry, photothermal deflection spectroscopy, photothermal lens spectroscopy, photothermal diffraction spectroscopy, and methods based on sample reflection changes are all based on monitoring refractive index changes associated with sample heating. Each of these methods is based on a measurement of temperature change associated with increasing the energy of the analytical sample. There have been many applications of photothermal methods for chemical and materials analysis. These applications fall under four main categories: Photothermal spectroscopy, Photothermal detection, Photothermal monitoring of excitation and relaxation process, and Photothermal probing of physical properties.