Inner-shell photoionization and core-hole decay of Xe and XeF$_2$

Molecular effects on inner-shell photoionization and core-hole decay are explored by comparing cross sections and partial ion yields of Xe and XeF$_2$ from Xe 3d and F 1s subshells in the 660-740 eV range. The Xe 3d-$\epsilon$f continuum shape resonances dominate the total cross sections, but prominent resonances appear in the XeF$_2$ cross section due to excitation of Xe 3d and F 1s electrons to the lowest unoccupied molecular orbital (LUMO), a delocalized anti-bonding MO. Relativistic coupled-cluster calculations were performed to identify the subshell ionization thresholds, the LUMO resonances and their oscillator strengths. Comparison of the Xe charge state distributions of the atom and molecule show a general shift to lower charge states in XeF$_2$. The measurements support a model of core-hole decay in which charge is redistributed from Xe to the F ligands and energetic F ions are produced by Coulombic fragmentation.