Rotational dynamics of desorption and inelastic scattering for the NO/Pt(111) system

Abstract

The rotational population and alignment distributions of NO are measured subsequent to the molecule’s interaction with a clean Pt(111) surface. Two distinct dynamical regimes of trapping/desorption and inelastic scattering are studied over the temperature range 375–550 K. For the case of molecular desorption, molecules which desorb with a large amount of angular momentum (J>12.5) prefer to rotate in the plane of the surface. Those molecules which scatter from the surface show the opposite preference for rotational alignment, i.e., they preferentially rotate in a plane perpendicular to the surface. The non-Boltzmann rotational distribution reveals that a large fraction of the scattered molecules contain more energy in rotation than initially exists as total energy in the beam. This observation indicates the important role of surface vibration to rotational energy transfer in this system. A quasiclassical stochastic trajectory model is able to account for much of the observed phenomena.