Photoionization of tungsten ions with synchrotron radiation

Photoionization experiments were performed with tungsten ions using a photon–ion merged-beams setup at the Advanced Light Source. Cross-sections σq,q+1 for photon-induced single ionization of Wq+ ions (q=1,2,3,5) and σq,q+2 for photon-induced double ionization of W+ ions have been explored in the energy range 20–70 eV. While σq,q+1 for the lower charge states is dominated by broad resonance features in the range of 4f and 5p excitations, the cross-section σ5, 6 shows much narrower peak features. Significant contributions from initial metastable states are evident. Double ionization is substantially enhanced at energies above the threshold for single ionization of a 4f electron in W+.