Abstract
Accurate photodetachment cross sections are evaluated for the 1s22s2 1S bound state of the negative lithium ion over a wide range of initial photon energies. The calculation employs a multichannel theory based upon the R-matrix method for electron-atom collisions. Special emphasis has been given to the energy region in the vicinity of the opening of the 2p 2po threshold where strong coupling between the two channels produces a pronounced cusp in the 2Sepsilon p channel cross section. The evaluated cross sections across this very narrow energy region are found to be in excellent agreement with previous theoretical calculations, but are unable to reproduce the 'resonance-like' structure found in the experimental data of Dellwo et al. (1992).