Electron-impact excitation of Fe7+

Abstract

Electron-impact excitation cross sections for Fe7+ are calculated using R-matrix close-coupling theory. The calculation includes 33 LS terms of the seven configurations: 3p63d, 3p53d2, 3p53d4s, 3p64s, 3p64p, 3p64d, and 3p64f. Following an intermediate-coupling frame transformation of the LS K-matrices, cross sections and effective collision strengths are obtained for 2926 transitions among 77 LSJ levels of the original seven configurations. After the solution of the corresponding collisional-radiative equations, the emission line ratio involving a blend of the 3p64f 2F → 3p63d 2D transitions at around 131 A and another blend of the 3p53d22P → 3p63d 2D and 3p53d22D → 3p63d 2D transitions at around 168 A is found to provide a very useful electron-temperature diagnostic.