Dissociation of high-energy ionized hydrogen molecules in helium gas

Abstract

The Born and closure approximations are used to obtain an expression (in the form of a series) for the dissociation cross section σ1 for the process H2+ + He → H + H+ + He. Taking the first term only of the series, and assuming the LCAO approximation for the H2+ wave function, that overlap terms can be neglected, and that the hydrogen and helium atoms are in their ground state after the collision, the high-energy limit for the dissociation cross section is found to be 1 59 × 10-14/E cm2, where E is the energy of the incident H2+ in keV, as compared with the experimental values 1 25 × 10-14/E cm2, or 1 10 × 10-14/E cm2. The effect of initial vibrational excitation of the H2+ is also examined, and found to increase σ1 by up to 20%, comparable with the experimental results of Barnett and Ray, and McClure for the dissociation of H2+ in hydrogen gas.