Electron-impact excitation of ions in the magnesium sequence. II. S v, Ar vii, Ca ix, Cr xiii, and Ni xvii

Collision strengths are presented for all transitions between the states (including fine structure) 3$s^2$ ${}^1$ $S_0$, 3s3p(${}^3$ $P_0$,1,2,${}^1$P ${}_1{}^{}{}_{}{}^{}$), 3$p^2$(${}^3$ $P_0$,1,2, ${}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$,${}^1$ $S_0$), 3s3d(${}^3$ $D_1$,2,3,${}^1$D ${}_2{}^{}{}_{}{}^{}$), and 3s4s(${}^3$ $S_1$,${}^1$ $S_0$) in Mg-like ions S v, Ar v i i, Ca i x, Cr xiii, and Ni x v i i. The calculations are carried out in LS coupling using the distorted-wave approximation with a ten-state eigenfunction expansion. Relativistic effects in the target states are taken into account using the Breit-Pauli Hamiltonian, and the term-coupling coefficients thereby obtained are employed to accomplish the transformation of the scattering matrices to intermediate coupling. Atomic effects involving autoionizing resonances in some transitions are considered, as well as the contribution of high partial waves to the transition 3$s^2$ ${}^1$ $S_0$–3s3d ${}^1$ $D_2$. The problem of bound-channel correlation-type functions in the eigenfunction expansion is discussed in some detail.