Effects of correlation between molecular diffraction and rotational excitation on the scattering dynamics of H2 from Cu(001)

We perform quantum dynamics calculations that include all six degrees of freedom of a H-2 and investigate the effects of the correlation between the molecular diffraction and rotational excitation on the dynamics of H-2 scattered from Cu(001). Our calculation results show that when the H-2 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 m(j) changing hom \m\ = 0 --> 2) decreases with increasing incident energies. On the other hand, when the H-2 undergoes diffraction an Cu(001) and assumes cartwheel-like rotation, the rotationally inelastic diffraction (RID) (j = 0 --> 2,m(j) = 0 --> 0) probability increases with increasing incident energies. Upon averaging over all possible orientations (averaging over all possible values of the azimuthal quantum number m(j), \m(j)\ = 0, 1, 2). the. mi-averaged RID probability shows qualitative features that depend on which type of H-2 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 m(j)-averaged RID probability agree with recent experimental observations for the scattering of D-2 on Cu(001).