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Light-induced atomic desorption and diffusion of Rb from porous alumina

We present the first study of light induced atom desorption (LIAD) of an alkali atom (Rb) in porous alumina. We observe the variation due to LIAD of the rubidium density in a vapor cell as a function of illumination time, intensity and wavelength. The simple and regular structure of the alumina pores allows a description of the atomic diffusion in the porous medium in which the diffusion constant only depends on the known pore geometry and the atomic sticking time to the pore wall. A simple one-dimensional theoretical model is presented which reproduces the essential features of the observed signals. Fitting of the model to the experimental data gives access to the diffusion constant and consequently the atom-wall sticking time and its dependence on light intensity and wavelength. The non-monotonic dependence of the LIAD yield on the illumination light frequency is indicative of the existence of Rb clusters in the porous medium.