X-ray induced electron and ion fragmentation dynamics in IBr

TL;DR

This study investigates the electron and ion fragmentation dynamics in IBr molecules induced by x-ray core ionization, combining experimental x-ray/ion coincidence spectroscopy with a computational model to understand decay processes and molecular dissociation.

Contribution

The paper introduces a combined experimental and computational approach to analyze inner-shell decay and fragmentation in IBr, providing detailed charge state and kinetic energy data for molecular dissociation.

Findings

Charge states and energies of atomic ions following core ionization are characterized.

A computational model successfully simulates the cascade decay and fragmentation process.

Insights into the redistribution of electrons and nuclear motion during decay are obtained.

Abstract

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.