Effects of correlation between molecular diffraction and rotational excitation on the scattering dynamics of H-2 from Cu(001)

We perform quantum dynamics calculations that include all six degrees of fr eedom of a H-2 and investigate the effects of the correlation between the m olecular diffraction and rotational excitation on the dynamics of H-2 scatt ered from Cu(001). Our calculation results show that when the H-2 undergoes diffraction on Cu(001) and assumes helicopter-like rotation, the rotationa lly inelastic diffraction (RID) probability (with the rotational quantum nu mber j changing from j = 0 --> 2, and the corresponding azimuthal quantum n umber m(j) changing hom \m\ = 0 --> 2) decreases with increasing incident e nergies. On the other hand, when the H-2 undergoes diffraction an Cu(001) a nd assumes cartwheel-like rotation, the rotationally inelastic diffraction (RID) (j = 0 --> 2,m(j) = 0 --> 0) probability increases with increasing in cident energies. Upon averaging over all possible orientations (averaging o ver all possible values of the azimuthal quantum number m(j), \m(j)\ = 0, 1 , 2). the. mi-averaged RID probability shows qualitative features that depe nd on which type of H-2 rotation (helicopter-like or cartwheel-like) domina tes at the particular incident energy range considered. Apart from differen ces due to isotope effects, the qualitative features of the m(j)-averaged R ID probability agree with recent experimental observations for the scatteri ng of D-2 on Cu(001).