Atomic Data and Spectral Line Intensities for Fe VIII

Abstract

Electron impact collision strengths, energy levels, oscillator strengths and spontaneous radiative decay rates are calculated for Fe VIII. The configurations used are 3p63d, 3p53d2, 3p64s, 3p64p, and 3p53d4s giving rise to 73 fine-structure levels in intermediate coupling. Collision strengths are calculated at four incident energies, 10, 30, 50, and 70 Ry. Excitation rate coefficients are calculated by assuming a Maxwellian electron velocity distribution at an electron temperature of log Te(K)=5.57, corresponding to maximum abundance of Fe VIII. Using the excitation rate coefficients and the radiative transition rates, statistical equilibrium equations for level populations are solved at electron densities 108–1014 cm−3. Relative spectral line intensities are calculated. Proton excitation rates and solar blackbody radiative excitation are also included in the statistical equilibrium equations.