Charge Exchange of Highly Charged Ne and Mg Ions with H and He

Cross sections for single electron capture (SEC), or charge exchange (CX), in collisions of Ne(8-10)+ and Mg(8-12)+ with H and He, are computed using an approximate multichannel Landau-Zener (MCLZ) formalism. Final-stateresolved cross sections for the principal (n), orbital angular momentum (l), and where appropriate, total spin angular momentum (S) quantum numbers are explicitly computed, except for the incident bare ions Ne10+ and Mg12+. In the latter two cases, nl -resolution is obtained from analytical l-distribution functions applied to n-resolved MCLZ cross sections. In all cases, the cross sections are computed over the collision energy range 1 meV/u to 50 keV/u with LZ parameters estimated from atomic energies obtained from experiment, theory, or, in the case of high-lying Rydberg levels, estimated with a quantum defect approach. Errors in the energy differences in the adiabatic potentials at the avoided crossing distances give the largest contribution to the uncertainties in the cross sections, which are expected to increase with decreasing cross section magnitude. The energy differences are deduced here with the Olson-Salop-Tauljberg radial coupling model. Proper selection of an l-distribution function for bare ion collisions introduces another level of uncertainty into the results. Comparison is made to existing experimental or theoretical results when available, but such data are absent for most considered collision systems. The nl S-resolved SEC cross sections are used in an optically thin cascade simulation to predict X-ray spectra and line ratios that will aid in modeling the X-ray emission in environments where CX is an important mechanism. Details on a MCLZ computational package, Stueckelberg, are also provided.