Effects of Correlation between Molecular Diffraction and Rotational Excitation on the Scattering Dynamics of H₂from Cu(001)

Abstract

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).

Quantum tunneling and reflection of a molecule with a single bound state

“…The similarity between tunneling and scattering problems also allows for further applications in molecular physics. The scattering of H 2 from Cu (001) [21] and NO from diamond (110) [22] have been shown to produce energy resonances similar to those predicted in earlier works utilizing time-independent formulations.…”

“…The limits of integration for P Sν (t) correspond to the range of the effective potential inx (for L/a = 10, the effective potential vanishes for |x| > 5). From (20), (21), and (22), we may define the probabilities of reflection, transmission, and straddling in the bound state and in an unbound state as follows:…”

Tunneling of a diatomic molecule incident upon a potential barrier

“…Experimental work on threedimensional molecular scattering is a current area of research. Recent work includes the scattering of Hg from Cu(OOl) [36] and NO from Diamond(llO) [37]. In these works it is shown that some energies are scattered more than others,…”

Isotope effects on direct and indirect processes of hydrogen abstraction from Cu(111)

“…We report isotope effects on hydrogen abstraction from Cu(111) for a surface coverage H = 0.500 monolayers (ML), which corresponds to 1.08 × 10 14 atoms cm −2 . We perform quantum dynamics calculations which quantum mechanically include both the direct and indirect processes by using the numerically stable time-independent coupled-channel method [23,25].…”