Steric Effects in the Scattering of Oriented CH3Cl Molecular Beam from a Graphite Surface: Weak Interaction of Physisorption

We report results of a study on steric effects appearing in the scattering of an oriented CH3Cl molecular beam from highly oriented pyrolytic graphite (HOPG) surface at 300 K. Data presented here show that the scattered CH3Cl beam intensity measured at a fixed scattering angle clearly depends on the initial molecular orientation toward the HOPG Surface. The scattered CH3Cl beam intensity for the CH3-end collision is larger than that for the Cl-end collision, suggesting that strong anisotropy of the interaction potential induces the molecular-orientation-dependent energy dissipation during transient trapping into the physisorption well.