Theoretical picture of the dynamics of the autoionization event in He(23S)H2 Penning ionization: collision energy dependence Original Research Article

A theoretical picture of the dynamics of the autoionization event He(23S)H2(ν″=0) → [He/3.H2++ (ν′)] + e− is obtained for the values of collision energies ranging from 20 to 150 meV. The treatment of the dynamics consists in 2D classical trajectory calculations based on static characteristics which include a quantum mechanical treatment of the perturbed H2(ν″=0) and H2+(ν′) vibrational motion. The vibrational populations are dynamical averages over the local widths of the He(23S)−H2(ν′=0) state with respect to autoionization to H2+(/3.He) in its ν′th vibrational level, the Penning electron energies are related to the local differences between the energies of the corresponding perturbed H2(ν″=0)(/3.He∗) and H2+(ν′)(/3.He) vibrational states. In accordance with recent experimental data, the average Penning electron energies are found to increase smoothly with increasing collision energy. The dependence on collision energy of the vibrational population factors for the nascent Penning ions H2+(ν′)(/3.He) is found to be less significant than that obtained from experimental data. Various aspects of this difference are discussed.