Photoionization of Ions of the Cerium Isonuclear Sequence in the Energy Range of 4d Excitations

Absolute measurements of photoionization cross sections for Ce$^{q+}$ ions (1 $\le $ q $\le $ 9) were performed in the photon energy range 105 -- 150 eV by merging beams of ions and monochromatized synchrotron radiation at the Advanced Light Source. Cross sections were measured for both single and double photoionization of Ce$^{+}$, Ce$^{2+}$ and Ce$^{3+}$. The photon energy resolution was 0.1 eV. The cross sections for initial charge states (1 $\le $ q $\le $ 9) are dominated by extremely broad resonance features due to 4d excitation-autoionization in this energy range, while that for Fe$^{9+}$ is characterized by narrow resonances. The reactant ion beams comprised unknown admixtures of ions in their ground state and in long-lived metastable states, complicating their detailed interpretation. Research supported by the Division of Chemical Sciences, Geosciences and Biosciences of the U.S. Department of Energy.