Regular Article

Hidden crossing theory of charge exchange in H⁺ + He⁺(1s) collisions in vicinity of maximum of cross section

¹ Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
² Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia

^a e-mail: tasko@ipb.ac.rs

Received: 15 December 2017
Received in final form: 13 February 2018
Published online: 20 April 2018

Abstract

Within the framework of dynamical adiabatic approach the hidden crossing theory of inelastic transitions is applied to charge exchange in H⁺ + He⁺(1s) collisions in the wide range of center of mass collision energies E_cm = (1.6–70) keV. The good agreement with experiment and molecular close coupling calculations is obtained. At low energies our 4-state results are closest to the experiment and correctly reproduce the shoulder in energy dependence of the cross section around E_cm = 6 keV. The 2-state results correctly predict the position of the maximum of the cross section at E_cm ≈ 40 keV, whereas 4-state results fail to correctly describe the region around the maximum. The reason for this is the fact that adiabatic approximation for a given two-state hidden crossing is applicable for values of the Schtueckelberg parameter >1. But with increase of principal quantum number N the Schtueckelberg parameter decreases as ~N⁻³. That is why the 4-state approach involving higher excited states fails at smaller collision energies E_cm ≈ 15 keV, while the 2-state approximation which involves low lying states can be extended to higher collision energies.