State-specific dynamics of ${\mathrm{D}}_2$ desorption from Cu(111): The role of molecular rotational motion in activated adsorption-desorption dynamics

We report state-specific kinetic energy distributions for ${\mathrm{D}}_2$ desorbed from Cu(111), which we have analyzed to obtain state-specific functions for adsorption probability versus kinetic energy. The dependence of these functions on vibrational state is in agreement with previous adsorption measurements. The dependence of the adsorption functions on rotational state J reveals a complex dynamical role for rotation in activated adsorption. As a function of J, the translational energy required for adsorption first increases slightly as J increases from 0 to 5 and then decreases markedly with higher J.