Time-resolved, photothermal-deflection spectrometry with step optical excitation

摘要

A theoretical model of a novel time-resolved, photothermal-deflection spectrometry with step optical excitation (a rectangular pulse of a finite duration) is presented. To make the theory practicable, i.e., able to be used to determine the values of optical and thermal properties of the sample by fitting experimental data to the theory, approximations are introduced. The numerical simulations show that when the value of the thermal conductivity of the deflecting medium (e.g., air) is small, the adiabatic approximation for the heat conduction at both front and rear surfaces of a sample is effective for both transparent and opaque samples, while the adiabatic and isothermal approximations for the heat conduction at the front and rear surfaces, respectively, are valid only for an opaque sample. With these approximations, the optical and thermal properties-such as optical absorption coefficient and thermal diffusivity-of solid materials (optically transparent or opaque) can be directly measured by this novel method. (C) 2004 Optical Society of America.