Oscillator strengths and inelastic scattering of electrons from OII

Electron-collision excitation cross sections of inelastic transitions among the 28 LS terms of the 2s(2)2p(3), 2s2p(4), 2s2(2)p(2)3s, 2s(2)2p(2)3p, 2s (2)2p(2)3d and 2s(2)2p(2)4s configurations of singlyionized oxygen are calc ulated using the R-matrix method, The target states are represented by fair ly extensive configuration-interaction wavefunctions which yield excitation energies, oscillator strengths and radiative lifetimes of excited states t hat agree well with available calculated and measured values. To assess the importance of electron correlation and coupling to higher excited states i n the scattering calculation, the present 28-state calculation is compared with the earlier 11-state R-matrix theory. Our cross sections for the 2s(2) 2p(3) S-4 degrees-2s(2)2p(3) D-2 degrees and 2s(2)2p(3) S-4 degrees-2s2p(4) P-4 transitions show good agreement with the merged-beams energy-loss expe riment and the 11-state R-matrix theory.