Quasiclassical trajectory study of rotational energy transfer in the scattering of NH3 from a flat, rigid gold surface

Abstract

Quasiclassical trajectories are used to study rotational energy transfer in the collision of a rigid-rotor NH3 molecule with a flat, rigid gold surface. The anisotropic term in the long-range attractive potential causes the NH3 to preferentially reorient with its dipole moment normal to the surface plane as it approaches the surface. This reorientation decreases the rotational energy transfer and gives rise to a sharp rotational rainbow at zero rotational energy. Trajectory results predict that the molecule preferentially scatters into low K states (tumbling) rather than the J=K states (spinning). This prediction is in qualitative agreement with recent molecular beam/surface scattering experiments.