Continuous wave photothermal deflection spectrometry based on Fresnel diffraction theory: Experimental applications

Abstract

Recently we developed a one-dimensional continuous wave photothermal deflection model based on Fresnel diffraction theory with a set of closed-form analytical signal expressions for both fundamental and second harmonic responses. This article reports its experimental applications in thermal property measurements, demonstrating the simplicity, validity, and usefulness of these analytical signal expressions. The thermal diffusivity of air was found to be (2.2Ϯ0.1) ϫ10 Ϫ5 m 2 /s that is consistent with literature value; the thermal effusivities of a rubber and a graphite plate sample were determined to be (1.2Ϯ0.2)ϫ10 3 W s 1/2 m Ϫ2 K Ϫ1 and (5.6Ϯ0.2) ϫ10 3 W s 1/2 m Ϫ2 K Ϫ1 , respectively, which are in good agreement with the measured values of the same samples by a photoacoustic method.

A composite photothermal technique for the measurement of thermal properties of solids

“…Shen In this work, a composite photothermal technique combining open photoacoustic cell and photothermal deflection methods for thermal characterization of opaque solids was developed. [9][10][11][12][13] Recently, Fresnel diffraction theory was employed to predict the fundamental and harmonic responses of PD signals, 11,12 which can be used for thermal property ͑e.g., thermal effusivity͒ measurement. Thermal diffusivity and thermal effusivity of carbon-based samples were measured, and the values of thermal conductivities and specific heat were then deduced.…”