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)×${10}^{\mathrm{-}12}$ ${\mathrm{cm}}^3$/sec for all four ions. For the H-like ions, the contribution to total rates from high Rydberg states (n≥6) is found large, accounting for nearly one-half of the total rates. Agreements with earlier estimates are at a ±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 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 2s ${}_{}{}^1{}_{}{}^{}p$ ${}_{}{}^1{}_{}{}^{}\mathrm{nl}$ excitation capture is found to be very large.