Structural and dynamical studies of CH- π bonded CH 4 -C 6 H 6 dimer by ultrafast intermolecular Coulombic decay.

The inner-valence ionization and fragmentation dynamics of CH 4 -C 6 H 6 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 CH 4 + +C 6 H 6 + ion pairs are obtained by coincident momentum measurement. Our analysis on the absolute cross sections indicates that the intermediate dication CH 4 + -C 6 H 6 + is preferentially produced by the removal of an inner-valence electron from CH 4 or C 6 H 6 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.