Electron-impact excitation of Fe7+

Electron-impact excitation cross sections for Fe7+ are calculated using R-m atrix close-coupling theory. The calculation includes 33 LS terms of the se ven configurations: 3p(6)3d, 3p(5)3d(2), 3p(5)3d4s, 3p(6)4s, 3p(6)4p, 3p(6) 4d, and 3p(6)4f. Following an intermediate-coupling frame transformation of the LS K-matrices, cross sections and effective collision strengths are ob tained for 2926 transitions among 77 LSJ levels of the original seven confi gurations. After the solution of the corresponding collisional-radiative eq uations, the emission line ratio involving a blend of the 3p(6)4f F-2 --> 3 p(6)3d D-2 transitions at around 131 A and another blend of the 3p(5)3d(2) P-2 --> 3p(6)3d D-2 and 3p(5)3d(2) D-2 --> 3p(6)3d D-2 transitions at aroun d 168 A is found to provide a very useful electron-temperature diagnostic.