Photodesorption of rubidium atoms from a sapphire surface

Photodesorption of rubidium atoms from crystalline sapphire surface is experimentally studied using the time-of-flight method and the total internal reflection effect. The adsorption energy of rubidium atoms on sapphire is determined to be ~0.7 eV. The dependence of the kinetic energy of desorbed rubidium atoms on the desorbing photon energy in the sapphire transparency range and in the absorption band of rubidium adatoms is determined. It is found that the average kinetic energy of outgoing atoms decreases at desorbing photon energies exceeding 2.3 eV. A model is proposed that relates the decrease in the kinetic energy of desorbed atoms to the appearance of a new channel of desorption of atoms in an excited electronic state.