Atomic data and spectral line intensities for Fe XV

Electron impact collision strengths, energy levels, oscillator strengths, and spontaneous radiative decay rates are calculated for the n=4n=4 and 5 complexes in Fe XV. We include in the calculations all the configurations in the n=3n=3, 4, and 5 complexes, corresponding to 283 fine-structure levels. We also provide accurate AA values for the n=3n=3 complex. Collision strengths are calculated at five incident energies for all transitions: 12.1, 28.2, 50.4, 80.9 and 123.0 Ry above the threshold of each transition. An additional energy has been added, whose value is between 0.00075 and 0.40 Ry, depending on the transition. Calculations have been carried out using the Flexible Atomic Code and the distorted-wave approximation. Excitation rate coefficients are calculated as a function of electron temperature by assuming a Maxwellian electron velocity distribution. We combined the excitation rate coefficients and the radiative transition rates calculated in the present work with RR-Matrix results available in the literature for the n=3n=3 complex, to solve the statistical equilibrium equations for level populations at electron densities in the 108–1014 cm−3 range and at an electron temperature of logTe(K)=6.3, corresponding to the maximum abundance of Fe XV. Spectral line intensities are calculated and compared with available observations.

► We calculate atomic data and transition rates to predict Fe XV line intensities. ► We provide data for the first time for many Fe XV lines observed in X-rays. ► These lines allow us to measure the physical parameters of solar and stellar coronae. ► Intensity ratios of lines emitted from n=3n=3 and n=4n=4 configurations do not agree with observations.