Effects of Correlation between Molecular Diffraction and Rotational Excitation on the Scattering Dynamics of H2from 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 from | m j | = 0→2) decreases with increasing incident energies. On the other hand, when the H 2 undergoes diffraction on 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 m j -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).