Charge exchange between He⁺ ions and solid targets: The dependence on target electronic structure revisited

This work compares the charge exchange properties of a large set of pure elemental solid targets by studying the neutralisation and reionisation in low-energy ion scattering (LEIS) experiments with He⁺ as incident ion. Neutralisation is extracted from the characteristic velocity in inverse velocity plots, while reionisation of neutralised He scattered on sub-surface atoms is studied through the threshold energy and intensity of so-called tails in LEIS spectra. Our work qualitatively reproduces the previously reported systematic dependence of neutralisation probability versus group (column) in the periodic table. However, such a trend is not observed for the reionisation probability, which is in contradiction to previously published results on neutral He backscattering. The results are discussed in terms of the electronic structure of transitions metals and charge exchange in close collision.