DiracR-matrix calculations of photoionization cross-sections of Ni xiii

Abstract

In this paper, we report total photoionization cross-sections of Ni xiii in the ground state (3P2) and four excited states (3P1,0, 1D2, 1S0) for the first time over the photon energy range 380–480 eV. The target wavefunctions are constructed with fully relativistic atomic structure GRASP code. Our calculated energy levels and oscillator strengths of core ion Ni xiv agree well with available experimental and theoretical results. The ionization threshold value of ground state of Ni xiii is found to be more closer to the experimental ionization energy and improved over the previous calculations. The photoionization cross-sections are calculated using the fully relativistic darc code with an appropriate energy step of 0.01 eV to delineate the resonance structures. The calculated ionization cross-sections are important for the modelling of features of photoionized plasmas and for stellar opacities.