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Description
In this paper, we present electron-impact excitation collision strengths and Maxwellian averaged effective collision strengths for the complicated iron-peak ion CrII. We consider specifically the allowed lines for transitions from the 3d^5^ and 3d^4^4s even parity configuration states to the 3d^4^4p odd parity configuration levels. The parallel suite of R-Matrix packages, RMATRX II, which have recently been extended to allow for the inclusion of relativistic effects, were used to compute the collision cross sections. A total of 108 LS{pi}/280J{pi} levels from the basis configurations 3d^5^, 3d^4^4s, and 3d^4^4p were included in the wavefunction representation of the target including all doublet, quartet, and sextet terms. Configuration interaction and correlation effects were carefully considered by the inclusion of seven more configurations and a pseudo-corrector {overline}4d type orbital. The 10 configurations incorporated into the CrII model thus listed are 3d^5^, 3d^4^4s, 3d^4^4p, 3d^3^4s^2^, 3d^3^4p^2^, 3d^3^4s4p, 3d^4^{overline}{4d}, 3d^3^4s{overline}{4d}, 3d^3^4p{overline}{4d}, and 3d^3^{overline}{4d}^2^, constituting the largest CrII target model considered to date in a scattering calculation. The Maxwellian averaged effective collision strengths are computed for a wide range of electron temperatures 2000-100000K which are astrophysically significant. Care has been taken to ensure that the partial wave contributions to the collision strengths for these allowed lines have converged with "top-up" from the Burgess-Tully sum rule incorporated. Comparisons are made with the results of Bautista et al. and significant differences are found for some of the optically allowed lines considered.
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