Ionization of Molecular Hydrogen

Abstract

A general model, based on a theoretically calculated ionization oscillator strength and an experimentally determined excitation shape function, has been obtained for calculating the molecular hydrogen electron-impact ionization cross section of a transition between any discrete vibrational levels of the neutral X 1 ∑ g + state and ionic X 2 ∑ g + state. Specifically, the excitation shape function and ionization oscillator strength for transitions from the v i = 0 level of the X 1 ∑ g + neutral state to the discrete levels of the X 2 ∑ g + ionic state are derived from analyzing several experimental measurements. The derived oscillator strength is found to be consistent with the 1994 photoabsorption measurements of Samson & Haddad and the 1977 theoretical cross sections of Flannery and coworkers. The derived excitation function, along with the oscillator strengths for transitions involving the v i > 0 level calculated from the data of Flannery and coworkers, permits an accurate calculation of the nondissociative cross sections of H 2 between any discrete vibrational levels over a wide energy range.