Atomic data and spectral line intensities for Ca XIII

Abstract

Electron impact collision strengths, energy levels, oscillator strengths and spontaneous radiative decay rates are calculated for Ca XIII. The configurations used are 2 s 2 2p 4 , 2s2p 5 , 2p 6 , 2s 2 2p 3 3s, 2s 2 2p 3 3p and 2s 2 2p 3 3d giving rise to 86 fine-structure levels in intermediate coupling. Collision strengths are calculated at five incident energies (40, 80, 120, 160 and 200 Ry) in the distorted wave approximation. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. Using the excitation rate coefficients and the radiative transition rates, statistical equilibrium equations for level populations are solved at electron densities covering the range of 10 8 -10 14 cm -3 at an electron temperature of log T e (K) = 6.5, corresponding to maximum abundance of Ca XIII. Relative and absolute spectral line intensities are calculated, and their diagnostic relevance is discussed. This dataset will be made available in the next version of the CHIANTI database.