State-to-state dynamics of high-n Rydberg H-atom scattering with H2: inelastic scattering and reactive scattering

Abstract

The state-to-state dynamics of high-n Rydberg H-atom scattering with para-H₂ at the collision energies of 0.45 and 1.07 eV have been studied using the H-atom Rydberg tagging time-of-flight technique. Both the inelastic scattering and reactive scattering are observed in the experimental time-of-flight spectra. The products H₂(v′, j′ = odd) come only from reactive scattering and present clearly forward–backward asymmetric angular distributions, which differ from those of the corresponding ion–molecule reaction. The products H₂(v′, j′ = even), however, come from both reactive scattering and inelastic scattering. Simulating the rotational distribution from reactive scattering, we found that most of the H₂(v′, j′ = even) products come from inelastic scattering. The angular distributions of the product H₂(v′, j′ = even) are consistent with what is predicted by the conventional textbook mechanism of inelastic scattering, and are a little different from those of the corresponding ion–molecule inelastic scattering. These results suggest that the effect of Rydberg electron could not be neglected in describing the differential cross sections of H* + para-H₂ scattering. From the simulation, the branching ratios of the inelastic scattering channel were determined to be 66% and 79% at the collision energies of 0.45 and 1.07 eV, respectively.