Dielectronic recombination of Ar15+ ions involving Δn=0 and Δn=1 transitions

Dielectronic recombination (DR) of Ar15+ (1s22s) ions was studied in a single-pass merged-beams experiment at the UNILAC accelerator of GSI. Absolute recombination rates and cross sections were measured for electron-ion center-of-mass energies from 0 to 580 eV. A number of Rydberg states formed by DR with Δn=0 and Δn=1 core transitions and even individual terms in the 1s23l3l' configuration could be resolved. Theoretical calculations of DR cross sections are in good overall agreement with the data. In the calculations for Δn=0 transitions effects of electric fields have to be included to reproduce the magnitude of the measured DR rates at the limit of the 2p1/2nl and 2p3/2nl Rydberg series. Discrepancies between theory and experiment are observed at the series limits of the (1s23lnl') Rydberg series. (orig.)