Atomic data and spectral line intensities for Ni XI

Electron impact collision strengths, energy levels, oscillator strengths, and spontaneous radiative decay rates are calculated for Ni XI. We include in the calculations the 12 lowest configurations, corresponding to 180 fine-structure levels: 3s23p6, s23p53d, 3s23p43d2, 3s3p63d, 3s23p54l, and 3s3p64l with l = s, p, d, f. Collision strengths are calculated at five incident energies for all transitions: 7.45, 17.6, 31.4, 50.1, and 75.2 Ry above the threshold of each transition. An additional energy, very close to the transition threshold, has been added, whose value is between 0.0007 Ry and 0.25 Ry depending on the levels involved. Calculations have been carried out using the Flexible Atomic Code. The scattering problem is solved 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 of the present work, combined with close coupling collision excitation rate coefficients available in the literature for the lowest 17 levels, statistical equilibrium equations for level populations are solved at electron densities covering the range of 108-1014 cm−3 and at an electron temperature of logTeK=6.1, corresponding to the maximum abundance of Ni XI. 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.