Proton impact excitation cross sections and rate coefficients for the 2s2 2p5 2P3/2 -2s2 2p5 2P1/2 transition in fluorine-like ions

Proton excitation cross sections and rate coefficients for the 2s² 2p^{5 2}P_3/2 -2s² 2p^{5 2}P_1/2 transition in fluorine-like Mg IV, S VIII, Cl IX, Ti XIV and Ni XX have been calculated using the close-coupled impact parameter method. These data are found to be significantly different from earlier results, and will hence lead to changes in the theoretical electron density diagnostic emission line ratios R₁ = I(2s² 2p^{5 2}P_3/2 -2s² 2p^{5 2}P_1/2)/I(2s² 2p^{5 2}P_3/2 -2s2p^{6 2}S_1/2) and R₂ = I(2s²2p^{5 2}P_3/2-2s²2p^{5 2}P_1/2)/I(2s²2p^{5 2}P_1/2-2s2p^{6 2}S_1/2) in F-like ions.