Electron Impact Excitation Cross Section Measurement for n = 3 to n = 2 Line Emission in Fe 17+ to Fe 23+

Abstract

We report the measurement of electron impact excitation cross sections for the strong iron L-shell 3 → 2 lines of Fe XVIII through Fe XXIV at the EBIT-I electron beam ion trap using a crystal spectrometer and a 6 × 6 pixel array microcalorimeter. The cross sections were determined by direct normalization to the well established theoretical cross section of radiative electron capture through a sophisticated model analysis, which results in the excitation cross section for 48 lines at multiple electron energies. We also studied the electron-density-dependent nature of the emission lines, which is demonstrated by the effective excitation cross section of the 3d → 2p transition in Fe XXI. © 2006. The American Astronomical Society. All rights reserved.