The recombination and level populations of ions. III. The role of charge exchange from neutral hydrogen

Abstract

For pt.II see Mon. Not. R. Astron. Soc., vol.178, p.10 (1977). A detailed calculation is presented of the populations of highly excited levels of impurity ions in plasmas which may be traversed by neutral hydrogen beams. Two degrees of refinement are developed, the 'bundled-n' picture in which whole principal quantum shell populations are treated and the 'resolved-nl' picture in which the separate nl shell populations are treated. The computational procedures are fairly general and treat principal quantum shells up to n approximately 500 and resolved-nl shells up to n approximately 40. They form an extension to earlier work by Burgess and Summers (1981) and by Summers (1977). The authors concentrate on the populations of hydrogen-like, helium-like and lithium-like ions and draws examples from the ions of oxygen. The collisional processes describing excitation from low levels, redistribution amongst high excited levels, charge exchange recombination and dielectronic recombination are examined in some depth with illustrations from oxygen ions.