Charge-Asymmetric Dissociation of Iodine Bromide in an Intense Femtosecond Laser Field

The mechanism of charge partitioning during Coulomb explosion, especially via charge-asymmetric dissociation (CAD) pathways, remains a key question in strong-field molecular dynamics. We present an experimental and theoretical study of CAD in the heteronuclear diatomic molecule iodine bromide (IBr) driven by 800 nm femtosecond laser pulses. Using dc-sliced ion velocity map imaging, we measured the kinetic energy releases of fragment ions Ip+ (p = 1–4) and Brq+ (q = 1–3), observing both charge-symmetric (CSD) and charge-asymmetric (CAD) dissociation channels. A unified model combining charge-resonance-enhanced ionization (CREI) with a classical over-the-barrier (COB) picture is introduced, which accounts quantitatively for the observed channels. The findings reveal the correlated electron–nuclear dynamics in IBr during Coulomb explosion, advance the understanding of strong-field dissociation in heteronuclear systems, and contribute to the analysis of ultrafast charge transfer in molecules.