Effects of configuration interaction for dielectronic recombination of Na-like ions forming Mg-like ions

Dielectronic recombination (DR) of Na-like ions forming Mg-like ions via excitation of a 21 core electron has been investigated for selected ions from Ca9+ to Zn19+. We find that configuration interaction (CI) between DR resonances with different captured electron principal quantum numbers n can lead to a significant reduction in resonance strengths for n greater than or similar to 5. We also explored the effect of this multi-n CI for the total DR rate coefficient. DR rate coefficients can be reduced by up to 10% at temperatures where an ion is predicted to form in collisional ionization equilibrium and up to 15% at higher temperatures.