Low-energy autoionization spectra of doubly excited states in B+(1s22pnl, n≥4)

An experimental and theoretical study is presented of the B+(1s22pnl, n=4 and 5) doubly excited states. Experimentally, low-energy electron emission spectra of B+, excited by B++He, B++Ar, and B++C-foil collisions, have been recorded with a zero-degree electron spectrometer setup. Several autoionizing states of B+ have been observed between 1 and 3 eV in the projectile emitter frame. The observed resonances, namely, (1s22p4s) 3P0, 1P0, (1s22p4p) 3D,1D, (1s22p4d) 3F0, 1F0, (1s22p4d) 3P0, and 1P0 do not appear in any previous data. The observations also suggest that the population of triply excited states in B is not important in the excitation process. Theoretically, five-state (2s,2p,3s,3p,3d) close-coupling calculations using IMPACT have been performed to determine positions, widths, and partial collision strengths for 22 of the lowest B+(1s22pnl) resonance states. Excellent agreement between theoretical and experimental energy positions is obtained