  Characterization of the inner-shell decay processes in molecules containing
heavy elements is key to understanding x-ray damage of molecules and materials
and for medical applications with Auger-electron-emitting radionuclides. The 1s
hole states of heavy atoms can be produced by absorption of tunable x-rays and
the resulting vacancy decays characterized by recording emitted photons,
electrons, and ions. The 1s hole states in heavy elements have large x-ray
fluorescence yields that transfer the hole to intermediate electron shells that
then decay by sequential Auger-electron transitions that increase the ion's
charge state until the final state is reached. In molecules the charge is
spread across the atomic sites, resulting in dissociation to energetic atomic
ions. We have used x-ray/ion coincidence spectroscopy to measure charge states
and energies of I$^{q+}$ and Br$^{q'+}$ atomic ions following 1s ionization at
the I and Br \textit{K}-edges of IBr. We present the charge states and kinetic
energies of the two correlated fragment ions associated with core-excited
states produced during the various steps of the cascades. To understand the
dynamics leading to the ion data, we develop a computational model that
combines Monte-Carlo/Molecular Dynamics simulations with a classical
over-the-barrier model to track inner-shell cascades and redistribution of
electrons in valence orbitals and nuclear motion of fragments.
