Photoionization cross section for Ni XIX

The relativistic R-matrix method is used to calculate photoionization cross section for the ground state 1s(2)2s(2)2p(6) S-1(e) (J = 0) and the first four excited states ( J = 0 even) of Ne-like Ni XIX, using the lowest 68 target states of Ni XX. Cross sections are dominated by Rydberg series of autoionizing resonances converging to several ionic states. We have compared our new 68-level cross sections with 32-level and with much lower 3-levels calculations. The 3-level results are found to be inadequate for practical applications due to the lack of complete set of resonances converging at higher thresholds. In our calculations, we have taken all the important physical effects like exchange, channel coupling, and short-range correlation, as well as relativistic effects into account. Our present results can be useful for modeling ionization balance of Ni XIX in laboratory and astrophysical plasmas. We believe that this is the first relativistic calculation for this ion to obtain the photoionization cross section.