Dielectronic and Radiative Recombination of Highly Stripped Sulfur Ions Incident on Argon

We have measured sulfur K x-ray emission following electron capture for 70 MeV Sq+(q=13-16) ions incident on Ar. K radiation resulting from capture was isolated by detecting coincidences between S K x rays and electron capture events. Two recombination processes which result in the emission of a K x ray were identified: (1) dielectronic recombination, which is the inverse Auger effect and (2) radiative recombination, which results from capture into a high n state (n≥2). The cross section for K radiation following capture increases by more than three orders of magnitude for q = 13+ to 16+. The fraction of capture events which result in K radiation increases from 0.0004 for q = 13+ to 0.3 for q = 16+, indicating that radiative recombination becomes relatively more important for high charge states, i.e. as q = Z. Possible applications to radiative loss processes in a plasma are discussed.