Landau–Zener studies of mutual neutralization in collisions of ${{{\rm H}}^{+}}+{{{\rm H}}^{-}}$ and ${\rm B}{{{\rm e}}^{+}}+{{{\rm H}}^{-}}$

Abstract

Semi-classical Landau–Zener studies of mutual neutralization reactions in low-energy H+ + H− and Be+ + H− collisions are performed. Avoided crossings between ionic and covalent states occurring at large internuclear distances are considered, and electronic couplings between these states are estimated using different semi-empirical and ab initio methods and tested on the H+ + H− reaction. The method is then applied to compute the cross sections and final state distributions for mutual neutralization in collisions of H− with Be+. These are reactions that might be important for the modeling of the fusion edge plasma of the divertor of ITER.

Atomic data on inelastic processes in low-energy beryllium-hydrogen collisions

“…We can see that the highest values of the mutual neutralization cross sections correspond to the transitions into the Be(2s3s 1 S), Be(2s3p 1,3 P), and Be(2s3d 3 D) states as the final states. This finding agrees with the conclusion from Hedberg et al (2014), though Hedberg et al (2014) are more in favor of the Be(2s3p 1 P) and Be(2s3d 3 D) states than Be(2s3p 1,3 P), see their discussion. We also note the different treatments for the Be(2p 2 1 D) state, see the discussion above.…”

“…The total mutual neutralization cross section calculated in the present work, that is, a sum of all partial mutual neutralization cross sections is in a perfect agreement with that computed by Hedberg et al (2014). Some deviation in the final state distribution appears due to (i) different formulas for evaluating the exchange interaction matrix elements; (ii) different techniques Table 1. for computing the Landau-Zener parameters; and (iii) accounting for multiple nonadiabatic regions in a nuclear dynamics (see Eq.…”

“…(3) for multichannel formulas). Unfortunately, no rate coefficients are published by Hedberg et al (2014) preventing comparison with the present calculations. The calculated partial rate coefficients for all processes in beryllium-hydrogen collisions between the states listed in Table 1 are presented in Tables A.1-A.10.…”

“…For this reason, Hedberg et al (2014) calculated the total cross section for the mutual neutralization process Be + + H − → Be * + H based on the model approach, not on ab initio potentials. However, these data are not sufficient for stellar atmosphere modeling: one has to know not only the total cross section for the neutralization process, but also partial cross sections and rate coefficients for all inelastic processes in collisions treated.…”

Switching classical trajectory Monte Carlo method to describe two-active-electron collisions

“…H + + H − collisions have been studied extensively, from both the experimental [39][40][41][42][43][44] and theoretical [30,31,[45][46][47][48][49][50][51][52] sides. In this respect, the main challenges of a classical description are to describe a stable two-electron target anion and to correctly represent the mutual neutralization process,…”