Charge exchange cross-sections in collisions of fully stripped N7+ ions with He atoms

ABSTRACT In this work, we present a comprehensive theoretical investigation of charge exchange (or electron capture) processes in collisions of fully stripped N$^{7+}$ ions with He ($1s^{2}$) atoms over a broad energy range of 0.1–225 keV u−1. Using a two-active-electron semiclassical asymptotic-state close-coupling approach, we compute total and partial cross-sections for single-electron capture (SEC) and double-electron capture (DEC), our results show good agreement with available experimental and theoretical data, and where discrepancies arise, possible underlying reasons are discussed in detail. In SEC processes, it is shown that 3$\ell$- and 4$\ell$-selective cross-sections follow a statistical $\ell$-distribution at high energies, favouring capture into high-angular-momentum subshells. In contrast, the $5\ell$-selective cross-sections exhibit oscillatory behaviour, reflecting strong interchannel competition. For DEC processes, asymmetric N$^{5+}(2\ell n\ell ^{\prime }$) and symmetric N$^{5+}(3\ell 3\ell ^{\prime })$ configurations are preferentially populated. Furthermore, we provide a complete and consistent set of cross-sections, particularly for state-selective processes, where available data are scarce. These results will be valuable for astrophysical and plasma radiation modelling.