In this work we present a study in the mixture formed by the beta-carotene
diluted in oleic acid in different concentrations being used for that the technique
called of Thermal Lens. We tried to vary the different control parameters as: the
thickness of the sample, his/her concentration, the potency of the excitation laser,
etc. We applied the aberrant model developed by Shen to find the thermal diffusivity,
the variation of the refraction index with the temperature (dn/dT), and the magnitude
of the sign of thermal lens, in the samples. We verified, with base in the theoretical
model presented in the chapter 2, that if the increase of the potency and of the
concentration it is very big and it reaches a certain value, parameters as thermal
diffusivity start to present distortions in the measured values. We also observed that
the mixture BC:AO presents nonlinear absorption, even for small potencies of the
excitation laser used. The contributions presented in this work are unpublished and they should
contribute to a better understanding of the thermal properties of the system BC:AO or
of similar systems as some vegetable oils that are rich in acid oleic and betacarotene.
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