Absolute cross sections for photoionization of Xeq +ions (1 ⩽ q ⩽ 5) at the 3d ionization threshold

The photon-ion merged-beams technique has been employed at the new P hoton- I on spectrometer at PE TRA III for measuring multiple photoionization of Xe q + ( q = 1–5) ions. Total ionization cross sections have been obtained on an absolute scale for the dominant ionization reactions of the type h ν + Xe q + → Xe r + + ( q − r ) e − with product charge states q + 2 ⩽ r ⩽ q + 5. Prominent ionization features are observed in the photon-energy range 650–750 eV, which are associated with excitation or ionization of an inner-shell 3d electron. Single-configuration Dirac–Fock calculations agree quantitatively with the experimental cross sections for non-resonant photoabsorption, but fail to reproduce all details of the measured ionization resonance structures.