Higher order resonant intershell electronic recombination for highly charged ions

Intershell tri-electronic recombination (TR) is reported for highly charged ions of Ar, Fe and Kr, where simultaneously to the K-shell excitation an additional L electron is excited due to resonant recombination of a free electron. Clear evidence on quadru-electronic recombination (QR) is found too, with two additional L electrons being excited at once. The experimental results on first and higher order recombination processes are discussed and compared with multi configuration Dirac-Fock calculations.