Absolute cross sections and decay rates for the triply excited ${\mathrm{B}}^{2+}{(2s2p}^2{}^{2}D)$ resonance in electron–metastable-ion collisions

Triply excited states of three-electron ions have been produced by resonant transfer excitation (RTE) in metastable two-electron-ion-beam–${\mathrm{H}}_2$ collisions. Measurements of the Auger-electron emission in the direction of the ion beam is used to determine the absolute cross sections for formation of the triply excited states and the branching ratios of the corresponding elastic and inelastic electron scattering channels. The results are compared to existing theoretical calculations of the Auger decay rates. Accurate measurements of the double differential cross sections are made on the bases of the known metastable ion beam fractions and known cross sections for RTE from the ground-state component of the beam. The system investigated is ${\mathrm{B}}^{3+}\left(1s2s{}^{3}S\right)+{\mathrm{H}}_2$ leading to the ${\mathrm{B}}^{2+}{(2s2p}^2{}^{2}D)$ resonance that decays to ${\mathrm{B}}^{3+}\left(1s2s{}^{3}S\right),$ the elastic scattering channel and to ${\mathrm{B}}^{3+}\left(1s2s{}^{1}S\right)$ and ${\mathrm{B}}^{3+}\left(1s2p{}^{3}P\right),$ two inelastic scattering channels.