Electron-impact excitation of lithium

The results of R-matrix with pseudostates (RMPS) and time-dependent close-coupling (TDCC) calculations of electron-impact excitation in Li are presented. We included 55 terms in the RMPS close-coupling expansion, of which nine are spectroscopic and 46 are pseudostates. The two-electron radial wave functions generated from earlier TDCC calculations for ionization from the ground state of Li by Colgan et at. [Phys. Rev. A 63, 062709 (2001)] are employed to determine the TDCC excitation cross sections. The RMPS and TDCC cross sections for transitions from 1s(2)2s to 1s(2)2p, 1s(2)3l, and 1s(2)4l are compared to each other and to cross sections determined from our R-matrix calculation without pseudostates, the convergent close-coupling calculations presented by Schweinzer et al. [At. Data Nucl. Data Tables 72, 239 (1999)], the coupled-channel optical calculations of Bray et al. [Phys. Rev. A 47, 1101 (1993)], and experimental measurements. These results indicate that coupling to the target continuum has a significant effect on electron-impact excitation in this atom; this increases with the principal quantum number of the excited term, and is large for transitions to 1s(2)4l.