Laser-induced surface decomposition of Al2O3 excited in the V-center absorption band

The primary products of desorption from Al2O3 surface excited by laser puls es (pulse duration tau similar to ns; wavelength lambda = 354 nm, radiant p ower density PIS < 10(8) W/cm(2)) in the V-center absorption band were stud ied by the time-of-flight (TOF) spectroscopy. The TOF spectra show evidence of the desorption of one "cold" (T-1 = 300 K) and two "hot" (T-2 = 1000 K, T-3 4300 K) groups of oxygen molecules with the Maxwell velocity distribut ions, as well as of the hot Al and O atoms with nonequilibrium energy distr ibutions (E-1 = 0.37 eV, E-2 = 0.38 eV). A model describing the oxygen deso rption as initiated by the electron transitions is suggested, in which esca pe of the cold O-2 molecules from the surface is related to discharge of th e O-2(-) anions adsorbed on the V-centers, desorption of the hot atoms is a ttributed to discharge of the surface O- anions, and the appearance of the hot O-2 molecules is related to the associative desorption of two O- anions localized at the same V-center discharged by a pair of excitons. (C) 2000 MAIK "Nauka/lnterperiodica".