Effective collision strengths for electron-impact excitation of Ni XII

Effective collision strengths computed by the R-matrix method are presented for the electron-impact excitation of Cl-like Ni XII. The total wave function used in the close-coupling expansion includes the lowest 14 target states of Ni XII, arising from the 3s23p5, 3s3p6 and 3s2p43d configurations. These 14 LS target states corresponds to 31 j-resolved fine-structure levels, connected by 465 independent transitions. Effective collision strengths for all possible transitions, calculated by averaging the electron collision strengths over a Maxwellian distribution of electron velocities, are tabulated over the electron temperature range log T(K) = 5.5 to log T(K) = 6.6. This range includes the temperatures of particular interest for many astrophysical applications