SIMPLIFIED CLASSICAL TRAJECTORY MODEL OF DISSOCIATIVE SCATTERING ON SURFACES - ROLE OF INCIDENT VIBRATIONAL AND TRANSLATIONAL ENERGIES

Recently reported molecular ion/surface scattering experiments suggest that translational and vibrational energies each have a distinct infl uence on molecular dissociation for the NO+/GaAs(110) system [J. Chem. Phys. 1994, 100, 6791]. To interrogate the coupling between vibration al and translational degrees of freedom, classical trajectory simulati ons were performed. The dissociation dynamics and energy transfer proc esses were examined for three different molecule/surface repulsive pot entials: a Born-Mayer potential, a Ziegler-Biersack-Littmark potential , and a Hartree-Fock potential. In each case, the calculated product a ppearance thresholds and average product translational energies are qu alitatively consistent With the aforementioned experimental results. I n all, this suggests that translational energy activates dissociation via a collision-induced dissociation mechanism. Regarding initial mole cular vibrational energy, the classical model shows that the relative dissociation probability depends on vibrational phase; it is surmised that electron transfer immediately prior to surface impact forms a vib rational coherence, which enhances O- production with increasing NO+(n u(+)) vibrational quanta.