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) under bar hoton-(I) under bar on spectrometer at (PE) under bar TRA III for measuring multiple photoionization of Xeq+ ( q = 1-5) ions. Total ionization cross sections have been obtained on an absolute scale for the dominant ionization reactions of the type hv + Xeq+ -> Xer+ + (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.