Determination of the Binding Energy of He2+ from Ion Scattering Data

Abstract

Data on the elastic and the charge exchange scattering of beams of He⁺ ions in He gas between 4 and 400 ev are analyzed to determine precisely the interaction energies for the lowest ²Σ_u and ²Σ_g states of He₂⁺. A Morse function is used to represent the energy for the attractive ²Σ_u state and an exponential is chosen for the repulsive ²Σ_g state. An attempt is made to determine the three disposable parameters strictly from the scattering data, but does not lead to a unique result. However, use of the spectroscopic value of the equilibrium distance for the ²Σ_u state permits a unique determination, leading to interaction energies valid from about 0.9 A to 3.8 A. The energies are in good agreement with available quantum‐mechanical calculations and give a dissociation energy of 2.16 ev for the ²Σ_u state. The cross‐section calculations are given in reduced units in a form readily applicable to the calculation of binding energies for similar systems as data may become available.