Estimating the Level of Uncertainty in Electron-Impact Excitation and Photoionisation Rates of Low-Ionised Stages of Ni Ions

Abstract

Ni iv lines can be used as diagnostics for temperature and density for various astrophysical objects. In addition, ionization of Ni2+ is one of the causes of the opacity in the interstellar medium. We calculate the photoionization of Ni2+ and the electron-impact excitation of Ni3+. We use a fully-relativistic Dirac Atomic R-Matrix Code (DARC) method. We include a large set of configurations in the expansion of the wave functions of the target, up to the n=6 atomic shell. We show preliminary results for the photoionization cross-sections of Ni2+ and the electron-impact excitation collision strengths of Ni3+. The expected final results can be implemented in the available software packages for astrophysical plasma simulation, such as CLOUDY. We also show a preliminary estimation of the error of the data by the comparison of different sets of calculations.

Keywords

• atomic data
• opacity
• photoionization
• electron-impact excitation