Single-photon double-ionisation coulomb explosion in organic molecules

This review explores Coulomb explosion dynamics in organic molecules triggered by single-photon double ionisation. We focus on the methanol molecule as a benchmark system, investigating competing charge-transfer mechanisms and the role of roaming neutral $ {\rm H}_{2} $ H2 in the Coulomb explosion. Experimental 3D coincidence fragment imaging and state-of-the-art ab initio molecular dynamics simulations provide insights into the complex dynamics. We discuss the concept of Coulomb explosion imaging and its comparison with theoretical models. The review also delves into the mechanisms behind C–C and C–O bond cleavage in various alcohol systems, and examines the contributions of roaming neutral $ {\rm H}_{2} $ H2 dynamics to $ {\rm H}_{3}^{+} $ H3+ and $ {\rm H}_{2}^{+} $ H2+ formation. By combining experimental data with nonadiabatic simulations, we discuss the roles of different spin and excited electronic states of the dication in the overall process.