Dynamics of the H+ + H− electron capture process in Debye plasmas

Abstract

Collision dynamics of the H+ + H− system is studied by using the atomic-orbital close-coupling (AOCC) method when the interactions of charged particles are screened. The atomic orbitals and eigenenergies of n ⩽ 6 states for H and ns (n ⩽ 5) states for H− are calculated as a function of the screening parameter and used in the AOCC dynamic scheme to calculate the electron capture cross sections in the energy range 1–100 keV u−1. The e−–H interaction in H− is described by a model potential. With decreasing the Debye screening length, the bound states centred on H+ and H− successively enter the continuum, reducing the number of reaction channels in the discrete spectrum. Furthermore, the interaction screening also introduces significant changes in the direct and exchange couplings, thereby affecting the magnitude and energy behaviour of state-selective cross sections. These cause the change of charge exchange spectrum, which may be applied to diagnose the temperature and density in laboratory and astrophysical plasmas.