Electron-impact excitation of the fine-structure levels , ) of singly ionized atomic oxygen

Effective collision strengths for O II ions are evaluated from electron-impact excitation collision strengths of singly ionized atomic oxygen ( O II) calculated in the close-coupling approximation using the ab initio R -matrix method at the Breit-Pauli approximation level. The lowest 21 fine-structure levels arising from the 11 , LS target states are included in the calculation. The effective collision strengths for all forbidden transitions between the ground configuration levels are obtained by averaging the electron collision strengths, for a wide range of incident electron energies, over a Maxwellian distribution of velocities. Results are presented for electron temperatures in the range 2000-1000 000 K, applicable to many laboratory and astrophysical plasmas. We believe that the results are the most accurate to date and so should be used in preference to previous values available in the literature.