Photoionization for the ground state of Al VII from threshold to theKshell

The photoionization cross sections of N-like Al VII are calculated from the first ionization threshold to 140 Ry using the R-matrix method. 14 target states (including 4 K-shell excited states) of Al VIII are included in the close-coupling calculation. The detailed structure and resonances of the cross sections across the L-shell and K-shell thresholds is described. The resonance energies and widths of some of the autoionization states are determined by analyzing the resonance structures. The results show that the autoionization width of the K-shell excited state of a $1s$ electron being excited into $2p$ orbital is the largest among all of the autoionization states. It is also larger than Doppler and Stark widths under a typical plasma condition. This result shows that the autoionization widths will have essential influence in simulating the x-ray transmission spectrum of Al plasma.