ΔM j transitions in homonuclear molecule scattering off corrugated surfaces. Square and rectangular lattice symmetry and purely repulsive interaction

Abstract

In this paper, we present the first formal and computational studies of Δmj transitions occurring in homonuclear molecule-corrugated surface collisions. The model potential is a pairwise additive one which correctly incorporates the fact that Δmj transitions occur only for corrugated surfaces (provided the quantization axis is chosen to be the average surface normal). The principal results are: (a) Δmj transitions are extremely sensitive to lattice symmetry; (b) strong selection rules obtain for specular scattering; (c) the magnitude of Δmj -transition probabilities are strongly sensitive to surface corrugation; (d) the Δmj transitions depend strongly on diffraction peak; (e) the ratio of molecular length to lattice dimension (r/a) has a strong influence on the magnitude of Δmj -transition probabilities [with the probabilities increasing as (r/a) increases]; (f) Δmj rainbows are predicted to occur as a function of the (r/a) ratio increases; (g) Δmj transitions and the Δmj rainbow are expected to accompany Δj-rotational rainbows; (h) such magnetic transition rainbows accompanying Δj rainbows are suggested as an explanation of recent experimental observations of quenching of NO polarization for larger Δj transitions in NO/Ag(111) scattering.

Stopping molecular rotation using coherent ultra-low-energy magnetic manipulations.

“…To understand the origin of the discrepancy between the DFT based calculations and the data, we look at the calculated 𝑆-matrix elements shown in Table 1, which predict that only the mJ=0 state undergoes de-excitation with a significant probability, in line with an approximate ∆mJ=0 propensity rule. This prediction has also been seen in previous calculations of RID transitions on square lattices 26,27 . It is important to note that if there is only one nonzero element in the 𝑆-matrix, the shape of the corresponding signal becomes independent of the specific magnitude and phase of the non-zero element.…”

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

“…The measurement of such a large change in the alignment would confirm that Δ m j ≠ 0 transitions occur with large probability: the minimum value of the alignment of the scattered j = 2 molecules is −0.96 if P ( j =2, m j =0→ j ‘=2, m j ‘≠0) ≤ 1%. Such low values for Δ m j ≠ 0 transitions were found for our model potential excluding V els , and also in the model calculations on H 2 −surface scattering referred to above which also excluded V els , as long as realistic values were used for the values of the surface lattice constants. The measurement of a large change in the alignment of the scattered molecules would therefore also serve as further proof for the importance of the electrostatic interaction for the scattering.…”

“…In previous calculations on scattering from ( j =1, m j ) states, we have shown that the probabilities for Δ m j ≠ 0 transitions decrease to less than 1% when the electrostatic interaction is excluded from the model. , Previously, calculations on scattering of homoatomic diatomic molecules using model potentials excluding V els only predicted large probabilities for Δ m j ≠ 0 transitions for cases in which the molecular bond length was close to the surface lattice constant. , As already noted before, the fact that V els is expressed in all second-order spherical harmonics (see eq 3.2) already suggests the possibility of large probabilities for Δ m j ≠ 0 transitions. As shown elsewhere, the reason that such transitions are primarily caused by V els is that it contributes φ-dependent terms that are both longer ranged and larger in the classically allowed region than the other components making up the molecule−surface interaction.…”

“…This finding suggests that the ionicity of insulator surfaces can in principle be probed by combined experiments and calculations on the diffraction of H 2 from such surfaces. Calculations on H 2 + LiF(001) that are based on a model potential which includes the electrostatic interaction 50-52 also contradict the previously established view that the magnetic rotational quantum number m j should be (approximately) conserved in scattering of H 2 from inert surfaces. ,, The calculations also predict that the diffraction should depend on the initial value of m j (the molecule's alignment) . The latter predictions have been cast in a form allowing ready experimental testing 52 and suggest a possible way of producing rotationally polarized beams of H 2 .…”

My Trajectory in Molecular Reaction Dynamics and Spectroscopy

“…Coauthors on the paper are Yinnon, a previously mentioned graduate student, and John Murrell, a well-known theorist from the University of Sussex who visited us then. We also derived useful approximations for rotationally inelastic and vibrationally inelastic molecule-surface scattering (18)(19)(20). These projects were done in cooperation with Donald J. Kouri of the University of Houston, a good friend and a collaborator of many years.…”