One-electron charge exchange between and positive multiply charged ions. 1. Collisions

Abstract

The cross section for one-electron transfer H − + He + → H(1s) + He * (1s, nlm) is calculated in this paper. The collisional system is treated as a three-electron one and matrix elements for the formation of excited helium He * (1s, nlm) in both singlet and triplet states (1S, 2 1,3 S, P and 3 1,3 S, P, D) are obtained. Close-coupling calculations were done for the 27 1s, nlm| (1S, 2 1,3 S, P and 3 1,3 S, P, D) final states covering the range 1-10 × 10 7 cm s −1 of the relative collision velocity. An approximation is used for the effective potential of H − and Coulomb Green's functions are used to describe the weakly bound electron of H − . A satisfactory agreement is obtained with the experimental cross section.

Theoretical study of mutual neutralization inHe++H−collisions

“…In Fig. 7, the 4 He + + H − and 4 He + + D − cross sections are compared with measured ones [18,21,22] and previous theoretical predictions [23,24]. At large energies, the cross sections connect smoothly to the measured and previous calculated ones.…”

“…However, at lower energies the calculated cross section is larger than the one measured using a merged-beam apparatus by Peart and Hayton [21]. The measured cross section does not display the same low-energy E −1 behavior as observed from the calculation and which is predicted by Wigner's [18,21,22] and theoretical predictions [23,24]. threshold law [39].…”

“…In 1992, Ermolaev [23] calculated the neutralization cross section at higher collision energies using a one-active-electron model. In the theoretical study by Chibisov et al [24], all three electrons were included. The nuclear motion was described classically and autoionization was not considered.…”

Low collision energy mutual neutralization reaction of He+ and H−

“…However, auto-ionization was found to have a very low contribution to the mutual neutralization reaction total cross section, for energies below 10 eV. The study yielded a large cross section, comparable with previous results [13][14][15][16]. The final states distribution showed a dominance of the state going to the He[1s3s 3 S] + H asymptotic limit, followed by the state going to the He[1s3p 3 P] + H asymptotic limit, with ratios of approximately 50% and 30%, respectively, at low collision energies.…”

Semi-classical Computation of Low-energy Collisions Cross Section in Mutual Neutralization of Helium and Hydrogen Ions

“…However, autoinization was found to have a very low contribution to the MN total cross section, for energies below 10 eV . The results showed a large cross section, comparable with previous results [12][13][14][15]. The current study includes ten adiabatic states and the aim is to test the reliability of the Landau-Zener [16,17] model for the HeH system, since it is not computationally demanding as the log-derivative method.…”