VELOCITY DISTRIBUTIONS OF PHOTOCHEMICALLY DESORBED MOLECULES

The standard picture of desorption induced by electronic transitions ( DIET) is analyzed for high excited state quenching rates. Simple dynam ical considerations are found to explain the velocity distributions ch aracterizing a large number of photodesorption and electron stimulated desorption systems. Without invoking any thermalization processes, th e model predicts a Maxwell-Boltzmann velocity distribution, thus provi ding a theoretical justification for this distribution's widespread us e as an empirical fitting formula for velocity distributions of nonthe rmally desorbed species.