ATOMIC DATA AND SPECTRAL LINE INTENSITIES FOR Ni XIII

Abstract

Electron impact collision strengths and spontaneous radiative decay rates are calculated for Ni XIII. The data pertain to the 48 levels of the configurations 3s23p4, 3s3p5, 3s23p33d, and 3p6. Collision strengths are calculated at five incident electron energies: 10.0, 20.0, 30.0, 40.0, and 50.0 Ry. Relative spectral line intensities are calculated for all astrophysically important transitions. These are obtained by computing the excitation rate coefficients (cm3s−1), i.e., the collision strengths integrated over a Maxwellian electron distribution, and then solving the equations of detailed balance for the populations of the 48 energy levels, assuming a collisional excitation model and an electron temperature of 2.0 × 106K. This temperature is typical for Ni XIII when formed in equilibrium by collisional ionization and recombination. Using the excitation rate coefficients and the radiative decay rates, level populations are computed for several electron densities and are given in this paper. We also investigate the effects of proton excitation and solar radiative excitation on the level populations and line intensities.