Dielectronic recombination for C VI, and O VII,VII.

Abstract

Dielectronic recombination (DR) cross sections and rate coefficients for the H-like and He-like C and O ions are calculated in the zero-field, zero-density limit. The peak rates are approximately (1.2--1.6){times}10{sup {minus}12} cm{sup 3}/sec for all four ions. For the H-like ions, the contribution to total rates from high Rydberg states ({ital n}{ge}6) is found large, accounting for nearly one-half of the total rates. Agreements with earlier estimates are at a {plus minus}5% level. For the He-like ions, the high-Rydberg-state contribution is strongly suppressed because of the extra Auger channel which opens up at {ital n}=5--7. Agreement with previous calculations is again at a 5% level. The DR cross sections for the initial metastable states of the He-like ions are also estimated for a few low-lying resonance states near the DR threshold. The cross section for the 2{ital s} {sup 1}S{r arrow}1s2p {sup 1}P+nl excitation capture is found to be very large.