Photoionization of potassium-like transition metal ions: Ti$^{3+}$ to Fe$^{7+}$

Photoionization cross section calculations are performed on potassium-like transition metal ions (Ti$^{3+}$, V$^{4+}$, Cr$^{5+}$, Mn$^{6+}$and Fe$^{7+})$ using both non-relativistic (LS-coupling) and relativistic (Breit-Pauli) $R$-matrix methods for the ground ([Ne]3$s^{2}$3$p^{6}$3$d$ $^{2}$D$_{3/2}^e )$ and the first excited ([Ne]3$s^{2}$3$p^{6}$3$d$ $^{2}$D$_{5/2}^e )$ states of each of the five ions. Photon energies up to the first 3p ionization threshold are considered. The results show that for Ti$^{3+}$, the cross sections are dominated by the giant (3\textit{p $\to $ }3$d)$ resonances which are analyzed and identified, while for the four other ions (V$^{4+}$, Cr$^{5+}$, Mn$^{6+}$and Fe$^{7+})$, the 3\textit{p $\to $ }3$d$ resonances lie below the ionization threshold, and the cross sections are dominated by 3$p^{5}$3$d$ \textit{ns} and 3$p^{5}$3$d$ \textit{nd} Rydberg series of resonances. Comparison of the Ti$^{3+}$ results with available theoretical and experimental data shows good agreement. This work is supported by DOE and NSF.