POSITIVE-ION EMISSION FROM EXCIMER-LASER EXCITED MGO SURFACES

We report measurements of the energy and angular distributions of posi tive ions (principally Mg+) photodesorbed from polished MgO crystals e xposed to 248 nm excimer laser radiation. At low laser fluences, kinet ic energies of several eV are observed and angular distributions are h ighly peaked in the direction perpendicular to the surface. We present an electrostatic model involving Coulombic repulsion of positively ch arged ions repelled by photoionized F centers.