K-shell photoionization of Be-like nitrogen from the ground state: energies and Auger widths of the high-lying double-excited states for N IV

Abstract

The K-shell photoionization cross section of Be-like nitrogen (N IV) from the ground state is studied with the R-matrix and distorted-wave method for photon energies from 5.7 to 41.2 Ry. The close-coupling expansion includes 34 target states of N V with the 13 configurations in the LS-coupling scheme. The resonance energies, quantum defect and widths of 18 series of autoionization are determined from QB method and agree with these by cross sections. Our theoretical resonance energies and widths are compared with the existing experiments on the Auger spectra and other theoretical results. The results show that the calculated resonance energies are in rather good agreement with the experiment on the Auger spectra. For the autoionization width of some resonance states, good agreement is also found with recent theoretical results wherever available obtained using a saddle-point complex-rotation method.