Absolute cross sections for2s−2pexcitation ofN4+by electron impact

Absolute cross sections have been measured for $1s^{2}2s{}_{}{}^2{}_{}{}^{}S_{\frac{1}{2}}^{}{}_{}{}^{}-1\mathrm{}{s}^{2}2p{}_{}{}^2{}_{}{}^{}P_{\frac{1}{2},\frac{3}{2}}^{}{}_{}{}^{}$ excitation of lithiumlike ${\mathrm{N}}^{4+}$ by electron impact. For this process, which has a threshold at 10 eV, relative cross sections measured at several energies between 4 and 52 eV were normalized to a single absolute measurement taken at 15.5 eV. Similar data for Li-like ${\mathrm{C}}^{3+}$ have been previously reported and are presented for comparison. In both cases, allowing for the experimental electron energy spread, the measurements agree within experimental uncertainties with published Coulomb-Born and close-coupling calculations over the entire experimental energy range. Rate coefficients as a function of electron temperature are also presented for the ${\mathrm{N}}^{4+}$ transition.