Impact of Atomic Substitution on Core-Hole Relaxation Dynamics: A Study of Br$_2$ and IBr

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Main Authors: Bhat, Nivedita, Nam, Yeonsig, Young, Linda, Southworth, Stephen H., Ho, Phay J.
Format: Preprint
Published: 2025
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_version_ 1866911183843360768
author Bhat, Nivedita
Nam, Yeonsig
Young, Linda
Southworth, Stephen H.
Ho, Phay J.
author_facet Bhat, Nivedita
Nam, Yeonsig
Young, Linda
Southworth, Stephen H.
Ho, Phay J.
contents Understanding inner-shell decay processes in heavy-element molecules is essential for unraveling x-ray-induced photodynamics and advancing molecular imaging techniques. In this study, we investigate the influence of atomic substitution on core-hole relaxation dynamics and molecular fragmentation in Br2 and IBr, initiated by x-ray absorption at the Br K-edge. Using a combination of X-ray/ion coincidence measurements and Monte Carlo/molecular dynamics simulations, we track charge distribution and the kinetic energy release (KER) of fragment ions with a total charge from 2+ to 8+. For both molecules, the simulated KER values show good agreement with experiment across different fragmentation channels. Our comparison reveals that substituting Br with the heavier I atom in IBr has minimal impact on the inner-shell electronic decay process, but significantly influences nuclear motion, leading to slower dissociation, thereby a KER close to the Coulomb limit, an effect attributed to the atomic mass. These findings highlight the interplay between electronic and nuclear effects in molecular fragmentation, particularly in heavy-element species, and provide new insights into medical therapies, structural biology, and astrophysics.
format Preprint
id arxiv_https___arxiv_org_abs_2509_24915
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Impact of Atomic Substitution on Core-Hole Relaxation Dynamics: A Study of Br$_2$ and IBr
Bhat, Nivedita
Nam, Yeonsig
Young, Linda
Southworth, Stephen H.
Ho, Phay J.
Atomic and Molecular Clusters
Understanding inner-shell decay processes in heavy-element molecules is essential for unraveling x-ray-induced photodynamics and advancing molecular imaging techniques. In this study, we investigate the influence of atomic substitution on core-hole relaxation dynamics and molecular fragmentation in Br2 and IBr, initiated by x-ray absorption at the Br K-edge. Using a combination of X-ray/ion coincidence measurements and Monte Carlo/molecular dynamics simulations, we track charge distribution and the kinetic energy release (KER) of fragment ions with a total charge from 2+ to 8+. For both molecules, the simulated KER values show good agreement with experiment across different fragmentation channels. Our comparison reveals that substituting Br with the heavier I atom in IBr has minimal impact on the inner-shell electronic decay process, but significantly influences nuclear motion, leading to slower dissociation, thereby a KER close to the Coulomb limit, an effect attributed to the atomic mass. These findings highlight the interplay between electronic and nuclear effects in molecular fragmentation, particularly in heavy-element species, and provide new insights into medical therapies, structural biology, and astrophysics.
title Impact of Atomic Substitution on Core-Hole Relaxation Dynamics: A Study of Br$_2$ and IBr
topic Atomic and Molecular Clusters
url https://arxiv.org/abs/2509.24915