Electron-impact excitation of the resonance transition inBe+: Anab initiotreatment of core-correlation and -polarization effects

We present theoretical electron-impact-excitation cross sections for several transitions in ${\mathrm{Be}}^{+}$, and fluorescence radiation polarizations for the ${\mathrm{Be}}^{+}$ resonance doublet. The projectile-electron energy varies from 0.3–2.0 Ry. A five-state close-coupling approximation is used. The target model is the most sophisticated employed in any scattering calculation to date, and yields oscillator strengths for several transitions in ${\mathrm{Be}}^{+}$ that are the most accurate available. Our results do not, however, improve upon previous work as regards the notable discrepancies between calculations and experimental measurements for excitation of the resonance transition. This indicates that high rigor in the treatment of short-range core-correlation effects is not required for an accurate description of these processes, and therefore either that other, heretofore ignored, effects must be taken into account in the theory or that other measurements are necessary. An accurate measurement of the hyperfine structure of the j=(3/2) fine-structure level of the doublet would be of particular and decisive importance.