Scattering of H2 by LiF(001) studied using a new model potential. I. Prediction of large differences in diffraction of cold beams of para-H2 and normal-H2

Abstract

Elastic and rotationally inelastic diffraction of hydrogen molecular beams from the (001) face of LiF at 80°KThe close-coupling wave packet ͑CCWP͒ method has been used for performing calculations on rotationally and diffractionally inelastic scattering of H 2 from LiF͑001͒, using a model potential. The scattering from the initial jϭ0, 1, and 2 states was investigated at normal incidence for a collision energy of 0.1 eV. If the quadrupole-ionic lattice interaction is included in the potential model, large probabilities ͑up to 0.3͒ are obtained for reorientational ͑m j changing͒ transitions in the scattering from the initial jϭ1 and jϭ2 states. This is in contrast with results of previous theoretical work which used model potentials not including the electrostatic interaction and found much smaller probabilities for ⌬m j transitions. Inclusion of the quadrupole-ionic lattice interaction in the model also leads to the prediction of large differences between the diffraction of H 2 in its jϭ0 rotational state and diffraction of jϭ1 H 2 . It should be possible to check this result by diffraction experiments employing cold beams of para-H 2 and normal-H 2 . In addition, the calculations show large differences between the diffraction of ''helicoptering'' H 2 ͑jϭ1 or 2, ͉m j ͉ϭ j͒ and ''cartwheeling'' H 2 ͑jϭ1 or 2, ͉m j ͉ϭ0͒.

Dynamical Quantum Filtering via Enhanced Scattering of para-H2 on the Orientationally Anisotropic Potential of SrTiO3(001)

“…We can compare the present results to previous reports for the inelastic scattering of H 2 on LiF(001), at normal incidence (Θ i = 0°) and incident energy of E i = 100 meV 33 . From the scattering probability data 33 Table 2.…”

“…4.96 and 16.1 along SrTiO 3 (001)[100] and SrTiO 3 (001)[110] of the TiO 2-and SrO-terminated SrTiO 3 (001), respectively). (Note that the results of ref 33. have since been confirmed experimentally34 ).…”

Quantum Dynamics of H2−Surface Scattering: H2+ LiF(001) and H2+ Cu(100)

“…We will show that recent calculations − and experiments 53 have nevertheless lead to a drastic change in the way the H 2 + LiF system is now viewed. New computational and experimental results reveal that the scattering of H 2 by LiF(001) is crucially influenced by the electrostatic interaction between the molecule's quadrupole moment and the surface ions.…”

“…In our work on H 2 + LiF(001) we have used a model interaction potential which can be written as a sum of five main contributions: In eq 3.1, V rep is the short-range repulsion energy, V att (6) is the dipole−dipole dispersion energy, V att (8) is the dipole−quadrupole dispersion energy, and V ind represents the interaction between the dipole moment induced on H 2 by the surface electric field and the surface ions. A detailed description of how these interactions are modeled may be found elsewhere . Most important for our present purpose is the electrostatic interaction between the molecule's quadrupole moment ϑ and the surface ions, which may be written as 42 where and G = 2π/ a , a being the surface unit cell lattice constant (2.84 Å).…”

“…The prime on the summation sign in eq 3.2 denotes that the sum is taken over all (positive and negative) integer values of n and m except the combination ( n = 0, m = 0). Further details concerning V els , including expressions for A nm and γ nm , can be found elsewhere …”