Contributions of dielectronic, trielectronic, and metastable channels to the resonant intershell recombination of highly charged silicon ions

Intershell, resonant electronic recombination is studied experimentally in an electron-beam ion trap for O-like Si6+ to He-like Si12+ ions at plasma temperatures in the megakelvin range similar to those found in the solar radiative zone and is compared to extended multiconfiguration Dirac-Fock and relativistic configuration-interaction predictions. For this low-Z ion, the higher-order electronic recombination processes are comparable in strength to the first-order one. The ratio of trielectronic to dielectric recombination for B-like species agrees well with predictions, whereas for C-like ions the measured value is only half as large. This difference is explained by the influence of metastable states populated in the recombining plasma.