ATOMIC DATA FROM THE IRON PROJECT .4. ELECTRON-EXCITATION OF THE P-2(3 2)O-P-2(1/2)O FINE-STRUCTURE TRANSITION IN FLUORINE-LIKE IONS/

Total collision strengths for the ground term fine structure transitio n in 17 fluorine-like ions from Ne II to Fe XVIII are obtained in the close coupling approximation. Model target ions with only two terms, 2 p(52)p(o) and 2s2p(62)S are used, so that the collision strengths are perturbed by autoionizing resonances which converge on the excited S-2 term. These features are carefully delineated before averaging over a Maxwell velocity distribution to obtain effective collision strengths . The thermally averaged collision strengths should be reliable for th e infrared lines excited at low temperatures in astrophysical situatio ns where photoabsorption dominates the ionization equilibrium. The pre sent calculation ignores resonances which converge on terms that lie a bove S-2. These are expected to make a significant contribution to the collision rates at higher temperatures. We give the range of temperat ures where the present results should be reliable.