Orientation dependence in the dissociative scattering of hydrogen molecules from metal surfaces: Interference of electron waves in the scattering process

The molecular orientation dependence of the dissociation probability of hyd rogen molecules scattered from metal surfaces is investigated. It is assume d that the dissociation of the molecule is induced by an excitation of elec tron system in the molecule, involving electron transitions from the bondin g state of the molecule to the metal substrate and from the metal substrate to the antibonding state of the molecule. The probability distributions ar e calculated as functions of the released kinetic energy and the final tran slational energy of the molecule in the cases when the impinging molecule h as various orientations. On the basis of the numerical results, it is found that the orientation dependence of the probability distribution appears as a consequence of the self-interference of electron waves transferring betw een the impinging molecule and the metal substrate. In addition, a good acc ount of the experimental results can be given for the probability distribut ion as functions of the released kinetic energy and the molecular orientati on with respect to the surface normal.