OPTICAL SATURATION, DIFFUSION AND CONVECTION EFFECTS IN THERMAL LENS SPECTROMETRY

In thermal lens spectrometry (TLS) the intense pump radiation can lead the chromophore to partial optical saturation conditions in which the ground state is depleted and the population of an intermediate excite d state increases. A model in which the excitation process competes wi th both the decay processes and diffusion and convection of the specie s in the excited and ground states is developed. The model is used to explain the variations of the TLS/spectrophotometry sensitivity ratios found for a series of phthalein and azo dyes in aqueous media.