Spatial and temporal evolution of ionic fragments produced by deep core-level ionization

Multiply charged molecules fragment under Coulomb repulsion, leaving characteristic fingerprints in ensuing electronic decay. Using K-shell ionization of HCl as a benchmark, we identify metastable intermediates that persist to internuclear separations beyond 100 a.u., where weakened Coulomb interactions enable the emergence of narrow atomic lines, while short-lived states decay at smaller separations, producing broad, red-shifted backgrounds. This work provides a previously missing dynamical description of coupled electronic and nuclear evolution in the Coulomb fragmentation regime.