Effect of resonances on the excitation rates of He-like Fe XXV ion.

Abstract

The effect of the autoionizing states 1s3l'nl, with n\ensuremath{\ge}3 on the He-like effective excitation rates of $_{26}$Fe xxv is examined. Results are obtained by computing directly the excitation rate coefficient for the processes 1${s}^{2}$+e\ensuremath{\rightarrow}1s3l'nl\ensuremath{\rightarrow}1s2l''+e, with n=3, 4, and 5, and by extrapolating them to ng5. For this ion, contribution of these autoionizing states to the excitation rate coefficients is more important than the corresponding contribution due to the 1s2l'nl autoionizing states. Nevertheless, the effect of all these resonances is much smaller than the effect of the radiative cascades.