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

Dielectronic recombination (DR) of AR 1 5 +(1s 22s) 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 e V. A number of Rydberg states formed by DR with Δn=0 and Δn=1 core transistions and even individual terms in the 1s 23l3l ’ 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 2p 1 / 2 n l and 2p 3 / 2nl Rydberg series. Discrepancies between theory and experiment are observed at the series limits of the (1s 23l n l ’) Rydberg series.