The penetration rates of three different sunscreens into the human skin in vivo have been investigated using photoacoustic spectroscopy. A statistic treatment of the data obtained in a group of 15 healthy volunteers with constitutively light white skin is made using a nonparametric test. The results showed the discrimination between the times of propagation of the used products, evidencing the sensitivity of this technique to evaluate the penetration of topically applied substances through human skin in vivo.

The refractive index and the temperature coefficient of the optical path length change of tellurite ͑80TeO 2 : 20Li 2 O͒ and chalcogenide glasses ͑72.5Ga 2 S 3 : 27.5La 2 O 3 ͒ were determined as a function of temperature ͑up to 150°C͒ and wavelength ͑in the range between 454 and 632.8 nm͒. The tellurite glass exhibits the usual refractive index dispersion in the wavelength range analyzed, while anomalous refractive index dispersion was observed for the chalcogenide glass between 454 and 530 nm. The dispersion parameters were determined by means of the single-effective oscillator model. In addition, a strong dependence of the temperature coefficient of the optical path length on the photon energy and temperature was found for the chalcogenide glass. The latter was correlated to the shift of the optical band gap ͑or electronic edge͒ with temperature, which was interpreted by the electron-phonon interaction model.