Rovibrationally inelastic scattering of (v=1, j=1) H2 from Cu(100): Experiment and theory

Abstract

Articles you may be interested inReactive scattering of H2 from Cu(100): Comparison of dynamics calculations based on the specific reaction parameter approach to density functional theory with experiment J. Chem. Phys. 138, 044708 (2013); 10.1063/1.4776224Theoretical evidence for nonadiabatic vibrational deexcitation in H 2 ( D 2 ) state-to-state scattering from Cu ( 100 ) A comparison between experiment and theory is performed for the scattering of (vϭ1, jϭ1) H 2 from Cu͑100͒ at normal incidence. Experimentally, this system was studied using molecular beam techniques, with stimulated Raman pumping employed to overpopulate (vϭ1, jϭ1) in the incident beam, and resonance enhanced multi-photon ionization used to detect the H 2 scattered in two (vϭ1, j) states, and two (vϭ0, j) states. Theoretically, six-dimensional wave packet calculations were performed, employing a new, extended potential energy surface that was computed with density functional theory, using the generalized gradient approximation and a slab representation of the metal surface. Theory and experiment are in good agreement for the survival probability, i.e., the probability for rovibrationally elastic scattering. However, the theory overestimates the probabilities for rotationally inelastic scattering ͑to vϭ1, jϭ3) and for rovibrationally inelastic scattering ͑to vϭ0, jϭ5 and 7͒ for channels that could be determined experimentally. The cause of these discrepancies is discussed, as are possibilities for future improvements in the theory as well as the experiment.

Vibrational de-excitation of v=1 H2 during collisions with a Cu(100) surface

“…This is probably a consequence of truncating the spherical harmonic expansion of the potential energy surface at second order, which makes the potential too anisotropic in the polar angle. Calculations using a similar PES but with a fourth-order spherical harmonic expansion 33 report a shift of probability from high final j to low j states, toward better agreement with experiment, which supports this assertion.…”

“…4 and 10͒ are not consistent with recent state-to-state measurements for scattering of (v 0 ϭ1, j 0 ϭ1) H 2 from Cu͑100͒. 33 Stimulated Raman pumping was used to overpopulate (v 0 ϭ1, j 0 ϭ1) in the incident molecular beam. The population of selected final states was measured using resonance enhanced multiphoton ionization.…”

“…In the experiments, a large fraction ͑ϳ0.5͒ of the incident molecules are unaccounted for in the scattered beam and are presumed to either react or scatter in one of these unobserved, low j channels. 33 Calculations using PES III and IV ͑Ref. 33͒ as well as an analysis of experiments 1 indicate that the reaction probability should be negligible at 0.1 eV.…”

Vibrational deexcitation and rotational excitation of H2 and D2 scattered from Cu(111): Adiabatic versus non-adiabatic dynamics

“…22,29,30 A similar conclusion has been recently reached for the scattering of N 2 from W(110) and N from Ag(111). 24 In the particular case of H 2 interacting with copper, adiabatic calculations have been shown to give good results in comparison with experiments for H 2 /Cu(100), 31,32 H 2 /Cu(110) (Ref. 33), and H 2 /Cu(111).…”

Reactive and diffractive scattering of H2 from Pt(111) studied using a six-dimensional wave packet method

“…Previous theoretical 57,58 and experimental 58,59 results show that large rotational excitation probabilities occur for collision energies E Z close to the threshold energy to reaction, because the molecule is able to come close to the barrier where the potential contains a large amount of anisotropy. This explains why rotational excitation is found already for low E Z ; the lowest barrier in the PES to reaction is only 0.06 eV.…”