Merged-beam measurements of electron-impact excitation ofAl2+(3s2S→3p2P)

Abstract

Absolute cross sections for electron-impact excitation of the ${3s}^{2}\stackrel{\ensuremath{\rightarrow}}{S}{3p}^{2}P$ transition in ${\mathrm{Al}}^{2+}$ were measured near threshold using the merged electron-ion beams energy-loss technique. Although the present results are lower than the previous crossed-beams fluorescence measurements of Dunn et al. [Phys. Rev. A 66, 032706 (2002)] by about 30%, these two experimental excitation cross sections at threshold are in agreement when the energy resolutions and total expanded uncertainties are considered. The present results are in excellent agreement with the published close-coupling calculations, but lie about 30% lower than the distorted-wave predictions.