# Charge Transfer in He+ − He → He(1s4l, l ≥ 2) − He+ Collisions in Intermediate Energy Range

## TL;DR

This study investigates charge transfer in helium ion collisions at intermediate energies and finds asymmetric electronic charge distributions.

## Contribution

The paper reveals the role of the Paul trap mechanism in charge transfer excitation at intermediate energies.

## Key findings

- Electronic charge distributions were asymmetric in the intermediate energy range.
- Electric dipole moments remained unchanged during charge transfer.
- The Paul trap mechanism significantly influences charge transfer excitation.

## Abstract

The anticrossing spectra of the helium line λ1s4l D3,F−1s2p P3=447.2 nm emitted after electron capture by He+ ions in He+−He collisions were measured for projectile energies of 10–29 keV. Furthermore, considering the excited states’ time evolution, the theoretical intensity functions were calculated. The electric field and density distributions of the target He atoms in the collision volume were taken into account, and by fitting the theoretical intensities to the measured ones, the post-collisional states of the charge-transferred He atoms were determined. The results indicate that for the intermediate projectile energy range, the electronic charge distributions were asymmetric, but the electric dipole moments did not change, as in the case of the target atoms excited directly in the collisions. This result shows that the Paul trap mechanism may play an important role in the charge transfer excitation in this energy range.