Role of the Renner-Teller effect after core hole excitation in the dissociation dynamics of carbon dioxide dication

The fragmentation of the doubly-charged carbon dioxide molecule is studied after photoexcitation to the C 1s 12π u and O 1s 12π u states using a multicoincidence ion-imaging technique. The bent component of the Renner- Teller split states populated in the 1s→ π* resonant excitation at both the carbon and oxygen 1sionization edges opens pathways to potential surfaces in highly bent geometries in the dication. Evidence for a complete deformation of the molecule is found in the coincident detection of C+ and O+2 ions. The distinct alignment of this fragmentation channel indicates rapid deformation and subsequent fragmentation. Investigation of the complete atomization dynamics in the dication leading to asymmetric charge separation shows that the primary dissociation mechanisms, sequential, concerted, and asynchronous concerted, are correlated to specific fragment kinetic energies. The study shows that the bond angle in fragmentation can extend below 20°