R-matrix calculations of core-excited negative-ion states in Li

The excitation cross sections for the lowest-lying autoionizing states 1s2s(2) S-2, ls2s2p P-4 and 1s(2s2p P-3) P-2 in lithium have been calculated by the R-matrix method with pseudostates. The close-coupling expansion includes 37 target states with the 1s(2)2l, 1s(2)3l, 1s2l2l', ls2l3l' configurations in the LS-coupling scheme. The excitation cross sections reveal a few prominent resonances in the near-threshold regions. The resonances have been assigned to the 1s2s(2)2p P-3 shape resonance and the 1s2s2p(2)(D-1) D-1,D-3 autodetachment states. This assignment has also been supported by the additional multiconfiguration calculations of these states. Good agreement, including the main resonance features, was obtained with the Is excitation functions measured recently by Borovik and Krasilinec (Borovic AA and Krasilinec V N 1999 J. Phys. B: At. Mel. Opt. Phys. 32 1941). The present calculations provide the first theoretical confirmation for the existence of short-lived core-excited states in the negative Li- ion.