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 dynamical considerations are found to explain the velocity distributions characterizing a large number of photodesorption and electron stimulated desorption systems. Without invoking any thermalization processes, the model predicts a Maxwell–Boltzmann velocity distribution, thus providing a theoretical justification for this distribution’s widespread use as an empirical fitting formula for velocity distributions of nonthermally desorbed species.