Projectile and target excitation in He+ + He collisions at intermediate energies

Junwen Gao,Zhimin Hu,Jianguo Wang,Yong Wu,Alain Dubois,Nicolas Sisourat

doi:10.1063/5.0025623

Abstract

We present ab initio calculations of cross sections for projectile and target excitation occurring in the course of He+ + He collisions using a three-active-electron semiclassical nonperturbative approach. Intermediate impact energies ranging from 1 keV to 225 keV/u are considered. The results of our calculations agree well with available measurements for both projectile and target excitation in the respective overlapping energy regions. A comparison of our results with those of other theoretical calculations further demonstrates the importance of a nonperturbative approach that includes a sufficient number of channels. Furthermore, it is found that the cross sections for target excitation into singlet states show a valley centered at about 25 keV/u, resulting from competition with electron transfer to singlet projectile states. By contrast, the cross sections for target excitation into triplet states do not exhibit any such structures.

Highlights

He+ + He is one of the simplest atomic collisional systems containing only three electrons
We present ab initio calculations of cross sections for projectile and target excitation occurring in the course of He+ + He collisions using a threeactive-electron semiclassical nonperturbative approach
It is found that the cross sections for target excitation into singlet states show a valley centered at about 25 keV/u, resulting from competition with electron transfer to singlet projectile states

Summary

INTRODUCTION

He+ + He is one of the simplest atomic collisional systems containing only three electrons It is, sufficiently complex to give rise to the main types of inelastic reactions (electron capture, excitation, ionization, and their bielectronic counterparts) observed in ion–atom collisions, since both target and projectile carry active electrons. In 1967, the calculated cross sections for capture and target excitation into He*(1s2s1,3S) were first reported by Sural et al. using a three-electron coupled-channel method These authors considered only six channels and neglected all of the momentum transfer phases.

THEORY

RESULTS AND DISCUSSION

CONCLUSIONS