Intramolecular scattering in dissociating multiply charged diiodoacetylene

The fragmentation dynamics of diiodoacetylene (${\mathrm{C}}_{2}{\mathrm{I}}_{2}$), multiply ionized by low-energy collisions of ${\mathrm{Ar}}^{8+}$, is studied by using a momentum imaging spectrometer. The kinetic energy releases of four-body fragmentation channels of ${\mathrm{C}}_{2}{\mathrm{I}}_{2}^{q+}$ are investigated for $q$ up to 10, in which generation of high-$q$ ions requires conversion of the projectile collision energy to the electronic energy. The experimentally observed momentum correlation in the four-body dissociation channels reveals the tendency that the direction of the emitted carbon and iodine ions are mutually perpendicular, in contrast to the intuitive prediction that the fragments of the linear molecule will align. The simulated trajectories of the fragments based on the pure (classical) Coulomb explosion model manifest that the fragmentation scheme can be well described by this model, taking into account the significant Coulombic interactions between dissociating carbon and iodine ions.