Effects of classical nonlinear resonances in grazing diatom-surface collisions

Abstract

Energy transfer between vibrational, rotational, and translational degrees of freedom of a molecule during a collision process is enhanced when the classical frequencies associated with the initial state are in the proximity of nonlinear resonance conditions. We present an analysis of the classical resonant effects in the collisions of light diatoms with periodic surfaces, and discuss the initial conditions in which these effects can be observed. In particular, we find that for grazing incidence and resonant initial values of the classical frequencies, corresponding to specific vibro-rotational molecular states and translational energies, an efficient energy transfer between the intramolecular vibro-rotational degrees of freedom and the translational degree of freedom along a symmetry direction on the surface can be found. This efficient energy transfer manifests itself in the emergence of specific peaks in the molecular diffraction patterns. The predictions of the resonance analysis are contrasted with the results of classical trajectory calculations obtained in a diatom-rigid surface collision model.

Quantum and classical dynamics of reactive scattering of H2 from metal surfaces

“…Interesting predictions from the diffraction studies are that RID peaks should be larger than elastic diffraction peaks, 242 and that energy transfer to an intramolecular mode should be enhanced if the classical frequency corresponding to a specific rovibrational state is close to a nonlinear resonance condition. 340 An interesting prediction from the studies on dissociative scattering at FGI are that the probabilities of this process and of dissociative chemisorption under (hyper)thermal conditions should show a similar dependence on normal incidence energy. 243 This implies that experiments on dissociative scattering at FGI could be used to determine saturation values of dissociative chemisorption probabilities of highly activated systems like H 2 + Cu (111), Ag (111), and Au (111), which are not accessible in ordinary molecular beam experiments.…”

“…A few simulations have already been performed, 242,243,246,340 using a simple classical (or quasiclassical) binning method. 340 This efficient energy transfer would manifest itself in the diffraction spectra through the appearance of specific peaks. However, to corroborate this prediction experimentally is not an easy task, due to the polar angular resolution required, which is approximately 0.151, while the experimental spectra available in the literature 85,89 show a resolution of about 0.41.…”

“…From a theoretical point of view, this topic presents a real challenge, because of the high energy of the projectile. A few simulations have already been performed, 242,243,246,340 using a simple classical (or quasiclassical) binning method. 330,341 Based on these theoretical results it has been suggested that RID peaks should be larger than the elastic ones 242 under the typical experimental conditions (E i 4 200 eV).…”

“…Theoretical results have also suggested that the energy transfer between the intramolecular and the translational DOFs is enhanced whenever the classical frequency corresponding to an specific rovibrational state lies in the proximity of a nonlinear resonance condition. 340 This efficient energy transfer would manifest itself in the diffraction spectra through the appearance of specific peaks. Once again it may not be easy to confirm this theoretical prediction experimentally, because the experiments would have to be carried out using molecular beams with H 2 in specific highly excited states and with a well defined translational momentum.…”

Scattering of H(D) from LiF(100) under fast grazing incidence conditions: To what extent is classical dynamics a useful tool?

“…For example, Ruiz et al [34,35] have studied the momentum and the energy transfer between the intramolecular degrees of freedom (DOF's) in the quasiresonance region, using classical trajectory calculations and a diatom-rigid surface collision model. Classical trajectory calculations have also been used to study classical rainbow angles [16].…”