Structural and dynamical studies of CH-π bonded CH₄-C₆H₆ dimer by ultrafast intermolecular Coulombic decay

The inner-valence ionization and fragmentation dynamics of CH₄-C₆H₆ dimer induced by 200 eV electron impact is studied utilizing a multi-particle coincidence momentum spectroscopy. The three-dimensional momentum vectors and kinetic energy release (KER) of the CH₄⁺+C₆H₆⁺ ion pairs are obtained by coincident momentum measurement. Our analysis on the absolute cross sections indicates that the intermediate dication CH₄⁺-C₆H₆⁺ is preferentially produced by the removal of an inner-valence electron from CH₄ or C₆H₆ and subsequent relaxation of ultrafast intermolecular Coulombic decay followed by two-body Coulomb explosion. Combining with ab initio molecular dynamics (AIMD) simulations, the real-time fragmentation dynamics including translational, vibrational and rotational motions are presented as a function of propagation time. The revealed fragmentation dynamics are expected to have a potential implication for crystal structure imaging with various radiation sources.