Photoabsorption measurement by laser-induced thermal lensing effect

The temperature gradient induced after the photoabsorption of molecule causes a change of refractive index of the matrix and make a thermal lens perpendicular to the direction of light propagation. The optical property of the thermal lens is dependent on the total photo-energy absorbed by the molecule. This makes the thermal lens effect be useful to the concentration analysis. We have been studied the time resolved laser induced fluorimetry for uranium concentration analysis. Some difficulties were found out in the fluorescence analysis for the samples including many fluorescence quenchers. For the purpose to circumvent quencher problem, it is necessary to adapt a new analytical method which can be used complimentarily to the fluorimetry. The analytical technique using thermal lens effect is known to be a powerful method due to the high sensitivity and selectivity. Because the thermal lens signal (TLS) is dependent on thermal relaxation mechanisms, it serves as a complimentary technique to the very sensitive laser excited fluorimetry. 22 figs., 8 tabs., 34 refs. (Author)