Abstract

Photothermal deflection has been demonstrated to be a suitable technique for low absorbance measurements of nonfluorescent molecular spieces such as atmospheric constituents.^1-3 This technique involves the excitation of a sample by a modulated "pump-laser" beam. The heat generated from the absorption of light by the sample increases the temperature which changes the index of refraction, which in turn effects the optical beam of the "probe laser". Absorptivities in order of 10^-6cm^-1 have been measured using this technique^1-3. Recent attempts to improve the photothermal measurements have utilized interferometric detection scheme⁴. In spite of their high sensitivity, interferometric photothermal apparatuses are not suitable for general analytical use because they are bulky and require strict accurate alignments.

© 1987 Optical Society of America