Resonance contribution to electron-impact excitation of Ne-like ions

Detailed calculation of cross sections and rate coefficients for electron-impact excitation of Ne-like ions is presented in which contributions of the resonance intermediate states, 2p⁵{n}ₜlₜnl with nₜ{≤}4, are included, leading to the final states 2p⁵3lf, where lf=0,1,2. The cascade effect greatly complicates the calculation, as compared with the complementary process, the dielectronic recombination. The present study of the Fe¹⁶⁺ ion supplements the earlier work by B. W. Smith et al. [Astrophys. J. 298, 898 (1985)], while the Se²⁴⁺ ion was considered in detail for application to soft x-ray lasers. The resonance-excitation effect reduces substantially the existing discrepancy in the case of Se between the simple ionization-balance model and recent plasma experiments.