Strong Relativistic Effects and Natural Linewidths Observed in Dielectronic Recombination of Lithiumlike Carbon

The dielectronic recombination spectrum of C³⁺ was recorded for low collision energies. The spectrum of the 1s²2p4 1,3L resonances in the range 0--0.6 eV was analyzed in detail. It was found that the strongest peaks in the spectrum must be explained by dielectronic recombination mediated by relativistic effects, a process forbidden in pure LS coupling. For strongly autoionizing states the natural linewidths were observed. The spectrum was assigned in detail by the aid of very accurate relativistic many-body perturbation calculations.