Abstract
We perform quantum dynamics calculations that include all six degrees of freedom of a H2 and investigate the effects of the correlation between the molecular diffraction and rotational excitation on the dynamics of H2 scattered from Cu(001). Our calculation results show that when the H2 undergoes diffraction on Cu(001) and assumes helicopter-like rotation, the rotationally inelastic diffraction (RID) probability (with the rotational quantum number j changing from j=0→ 2, and the corresponding azimuthal quantum number mj changing from |mj| = 0→ 2) decreases with increasing incident energies. On the other hand, when the H2 undergoes diffraction on Cu(001) and assumes cartwheel-like rotation, the rotationally inelastic diffraction (RID) (j=0→ 2,mj = 0→ 0) probability increases with increasing incident energies. Upon averaging over all possible orientations (averaging over all possible values of the azimuthal quantum number mj, |mj|=0,1,2), the mj-averaged RID probability shows qualitative features that depend on which type of H2 rotation (helicopter-like or cartwheel-like) dominates at the particular incident energy range considered. Apart from differences due to isotope effects, the qualitative features of the mj-averaged RID probability agree with recent experimental observations for the scattering of D2 on Cu(001).
