Dissociative Excitation of Molecular Hydrogen by Electron Impact
Phys. Rev. A 6, 2180 – Published 1 December, 1972
DOI: https://doi.org/10.1103/PhysRevA.6.2180
Abstract
Dissociative excitation of molecular hydrogen can proceed via the process and yield metastable atoms that have kinetic energies near 0.3 eV ("slow") or near 4 eV ("fast"). The dissociation process has been studied using a pulsed electron gun with an energy resolution of ± 0.3 eV and using a metastable atom detector capable of viewing atoms with an angular resolution of 1° over a range 60°-120° with respect to the electronbeam direction. The measurement of the angular intensity distribution gives information about the final states that are involved in the dissociation process. (i) For slow atoms, the electron energy threshold for production of the least energetic of the slow metastable atoms is 14.6 ±0.3 eV. The excitation function and the angular distribution of the slow atoms suggest that the , , , and excited states are involved in the formation of these metastable fragments. (ii) For fast atoms, the electron energy threshold for production of the least energetic of the fast atoms is near 29 eV. The angular distribution data would indicate that these atoms arise from a state; the form of the excitation function indicates that the parent state has a multiplicity of 1. The change in energy distribution of the fast atoms, measured as a function of electron-gun voltage, supports the view that the state is a previously unreported doubly excited state that has an asymptotic energy of 24.9 eV.