R-matrix calculations for electron-impact excitation of ${\mathrm{C}}^{+}$, ${\mathrm{N}}^{2+}$, and ${\mathrm{O}}^{3+}$ including fine structure

Close-coupling calculations are carried out using the R-matrix method for the excitation of a number of states of boronlike carbon, nitrogen, and oxygen by electron impact. The ten lowest LS states of ${\mathrm{C}}^{+}$ and the eight lowest states of ${\mathrm{N}}^{2+}$ and ${\mathrm{O}}^{3+}$ are considered in the eigenfunction expansions. Including fine structure the collision strengths are calculated for all transitions among the states 2${\mathit{s}}^2$2p${(}^2$${\mathrm{P}}_{1/2,{3/2}^{\mathrm{o}}}$), 2s${2\mathrm{p}}^2$${(}^4$${\mathrm{P}}_{1/2,3/2,5/2}$${,}^2$${\mathit{D}}_{3/2,5/2}$${,}^2$S ${}_{1/2}{}^{}{}_{}{}^{}$${,}^2$${\mathrm{P}}_{1/2}$,3/2), 2$p^3$${(}^4$$S_{3/2}^o$${,}^2$${\mathrm{D}}_3$ ${}_2{}^{}{}_{}{}^{}$,${5/2}^o$${,}^2$${\mathrm{P}}_{1/2}$${,}_{32}^{\mathrm{o}}$), 2$s^2$3s${(}^2$$S_{1/2}$), and 2$s^2$3p${(}^2$$P_{1/2}$,${3/2}^{\mathrm{o}}$) for ${\mathrm{C}}^{+}$ and among all states of ${\mathrm{N}}^{2+}$ and ${\mathrm{O}}^{3+}$ excluding the n=3 configurations. Resonance structures in the collision strengths are delineated at a large number of energies and are found to have a substantial effect. A number of selected results are presented, in particular for the fine-structure transition ${}_{}{}^2{}_{}{}^{}\mathrm{P}_{1/2}^{\mathrm{o}}{}_{}{}^{}$${\mathrm{-}}^2$${\mathrm{P}}_{3/2}^{\mathrm{o}}$ and the resonance transition ${}_{}{}^2{}_{}{}^{}\mathrm{P}_{}^{\mathrm{o}}{}_{}{}^{}$${\mathrm{-}}^2$D in all three ions.