Electron collisional excitation of the 1s22s22p3 (4So3/2, 2Do5/2,3/2, 2Po3/2,1/2) fine-structure levels in Fe19+ ions

Collision strengths for electron-impact excitation of nitrogen-like Fe ions (Fe19+) have been calculated within the semi-relativistic R-matrix Breit-Pauli approximation. Twenty-three fine-structure levels arising from the 12 2s22p3, 2s2p4, 2p5 and 2s22p23s LSπ target states are included in this paper. Effective collision strengths for all forbidden transitions between the 1s22s22p34So3/2, 2Do5/2,3/2, 2Po3/2,1/2 terms 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 5.0≤Log Te≤8.0 K, applicable to many astrophysical plasmas. Our effective collision strengths, when compared with published values obtained within the distorted wave approximation, show considerable differences which we attribute to the presence of strong resonance structure in the cross sections. (author)