Resonant excitation channels in the 3d10-3d94s and 3d10-3d94p transitions of nickel-like Mo14+ and Zr12+

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At energies below the threshold for direct electron impact excitation, resonant excitations can make a significant contribution to the total excitation rate of a given energy level. In this paper, the rates of resonant excitation into the levels of the 3{ital d}{sup 9}4{ital s} and 3{ital d}{sup 9}4{ital p} configurations of Mo{sup 14+} have been calculated using a fully relativistic, multiconfiguration atomic structure code and detailed accounting of energy levels. By including the effects of resonant excitations in collisional-radiative models for the spectrum of NiI{endash}like Mo{sup 14+} and (by isoelectronic scaling) Zr{sup 12+}, the ratio of the emissivity of the 3{ital d}{sup 10}-4{ital d}{sup 9}4{ital s} {ital E}2 transitions to the emissivity of the 3{ital d}{sup 10}-3{ital d}{sup 9}4{ital p} {ital E}1 transitions is greatly enhanced, and sensitivity to electron temperature in the ratio is introduced. This ratio is density sensitive for {ital n}{sub {ital e}}{ge}10{sup 13} cm{sup {minus}3}, and therefore, given knowledge of either local temperature or density conditions, the {ital E}2-{ital E}1 ratio can serve as a diagnostic for local conditions in magnetically confined fusion plasmas. The current work demonstrates the need to include resonant excitations in collisional-radiative models of the soft x-ray emission of nickel-like ions. Goodmore » agreement is found between measurements of {ital E}1 and {ital E}2 line brightness ratios made in a tokamak plasma, and the predictions of collisional-radiative models in the present work. {copyright} {ital 1996 The American Physical Society.}« less