2007A&A...475..765R

Absorption or emission lines of FeII are observed in many astrophysical spectra and accurate atomic data are required to interpret these lines. The calculation of electron-impact excitation rates for transitions among even the lowest lying levels of FeII is a formidable task for theoreticians. In this paper, we present collision strengths and effective collision strengths for electron-impact excitation of FeII for low-lying forbidden transitions among the lowest 16 fine-structure levels arising from the four LS states 3d⁶4s ⁶D^e, 3d^{7 4}F^e, 3d⁶4s ⁴D^e, and 3d^{7 4}P^e. The effective collision strengths are calculated for a wide range of electron temperatures of astrophysical importance from 30-100000 K. The parallel suite of Breit-Pauli codes are utilised to compute the collision cross sections for electron-impact excitation of FeII and relativistic terms are included explicitly in both the target and the scattering approximation. 100 LS or 262-jj levels formed from the basis configurations 3d⁶4s, 3d⁷, and 3d⁶4p were included in the wavefunction representation of the target, including all doublet, quartet, and sextet terms. Collision strengths for a total of 34191 individual transitions were computed. A detailed comparison is made with previous theoretical works and significant differences were found to occur in the effective collision strengths, particularly at low temperatures.