Three-body fragmentation of methane dications produced by slow Ar8+-ion impact

The three-body fragmentation dynamics of CH42+ dications induced by single-electron capture of slow (3-keV/u) Ar8+ ions is investigated. The experiment is performed on a newly built, highly charged ion collision platform which consists of an electron cyclotron resonance ion source and a cold target recoil ion momentum spectroscopy (COLTRIMS) setup. Using the COLTRIMS methodology, the complete kinematical information is determined for two three-body breakup channels, CH42+ -> H+ + CH2+ + H and CH42+ -> H-2(+) + CH+ + H. Then analyzing the complete kinematics with the Dalitz plot, very different fragmentation mechanisms (e.g., sequential and/or concerted pathway) are clearly identified for the two channels. To confirm the existence of some possible fragmentation pathways, we also simulate corresponding Dalitz plots employing a simple classical mechanical model. For the H+ + CH2+ + H channel, the dependence of the fragmentation pathway on its kinetic energy release is studied, which reflects the different nature of the corresponding states of CH42+ dications. Furthermore, the kinetic energy ratio of two ionic fragments is analyzed to infer the three-body fragmentation mechanism of CH42+ dications.