Excitation Cross Section Measurement for n = 3 to n = 2 Line Emission in Fe(20+) to Fe(23+)

• Published in: The Astrophysical journal 2005-01, Vol.618 (2), p.1086-1094
• Main Authors: Chen, H, Beiersdorfer, P, Scofield, J H, Brown, G V, Boyce, K R, Kelley, R L, Kilbourne, C A, Porter, F S, Gu, M F, Kahn, S M
• Format: Article
• Language: English
• ISSN: 0004-637X
• DOI: 10.1086/426135

Electron impact excitation cross sections have been measured for iron L-shell 3 1 2 lines of Fe XXI to Fe XXIV at the EBIT-II electron beam ion trap using a crystal spectrometer and a 6 x 6 element array microcalorimeter. The cross sections were determined by direct normalization to the well-established cross section of radiative electron capture, and a summary of calculated energy-dependent radiative recombination cross sections for electron capture into the n = 2 state fine-structure levels of Fe(16+) to Fe(23+) ions is given. The measurement results for 17 lines and their comparison with model calculations are presented. While agreement of the model calculations with the experiment is good for most measured lines, significant discrepancies were found for a few lines, including the strongest line in Fe XXI.