Atomic data from the Iron project

This paper reports on radiative transition rates and electron impact excitation rate coefficients for levels of the 3d 7 ground configuration of Ni IV. The radiative data were computed using the Thomas-Fermi-Dirac central potential method, which allows for configuration interactions (CI) and relativistic effects in the Breit-Pauli formalism. Collision strengths in LS-coupling were calculated in the close coupling approximation with the R-matrix method. Then, fine structure collision strengths were obtained by means of the intermediate-coupling frame transformation (ICFT) method that accounts for spin-orbit coupling effects. The collision strengths were integrated over a Maxwellian distribution of electron energies, and the resulting effective collision strengths are given for a wide range of temperatures. We build a multilevel model for the Ni IV system and use it to identify the most important lines in optical and infrared spectra and to compute line ratios as diagnostics of nebular conditions. Finally, we test these data against recent observations of the bipolar planetary nebula Mz 3.