Convergent close-coupling approach to positron scattering on He+

Calculations of positron scattering on the hydrogen molecular ion

“…However, this difference is not attributed to the contribution of Ps formation. A similar difference was observed for the helium ion, where EL by positron impact [25] was about 60% higher than total ionisation by electron impact [44] even at energies where Ps formation is negligible.…”

“…e He starting from about 5eV above the ionisation threshold of He + [25]. Considering the similarity of the + H 2 and He + targets, we expect that the present single-centre calculations for + H 2 are accurate above 35eV.…”

“…In practice this often leads to numerical instabilities and lack of convergence. However, this is a relatively small energy region and for positron collisions with positive ions the Ps-formation cross sections have proved to be relatively small [25]. Due to this we did not observe any significant convergence issues and were able to continue the calculations down to the threshold for the first excitation.…”

“…The effect of Ps-formation channels is expected to be similar for both + H 2 and He + as a result of both targets carrying the same positive charge. For the latter, detailed close-coupling calculations were performed in both the single-and two-centre approaches in [25]. The two-centre results of these calculations are included in figure 2 for both the total EL and Psformation cross sections.…”

“…Results are presented for incident positron energies from 10 to 500eV for various cross sections of interest. In the absence of previous theoretical and experimental data, comparisons are made with the CCC results for electron scattering on + H 2 [24] and positron scattering on He + [25]. All quantities, unless specified otherwise, are in atomic units.…”