Electron-impact excitation ofAl2+

Detailed calculations of the electron-impact excitation of the sodiumlike ion ${\mathrm{Al}}^{2+}$ were performed using both the unitarized Coulomb-Born approximation and the close-coupling approach. Calculations were undertaken at both the five-state (3s, 3p, 3d, 4s, and 4p) and nine-state (+4d¯, 4f¯, 5s¯, and 5p¯) levels of approximation. Calculations using Hamiltonians both with and without (semiempirical) core-polarization potentials were completed. Particular attention was paid to the resonance (3s-3p) excitation. The inclusion of core-polarization potentials resulted in cross sections for the resonance excitation that are 10% smaller in magnitude. As an additional check on the calculations, binding energies of ${\mathrm{Al}}^{+}$ bound states, and oscillator strengths for ${\mathrm{Al}}^{2+}$ transitions, were also computed and compared with the results of measurements and other calculations.