Formation of H3+ through Chloromethane Dication Fragmentation

Using post Hartree-Fock Multi Reference Configuration Interaction methods, we performed suitable one-dimensional cuts of the potential energy surfaces of the lowest electronic states of the CH3Cl2+ dication. Calculations show that the CH3Cl2+ dication fragments efficiently produce the astrophysical, planetary, and atmospherically important H-3(+) cation. A new multistep mechanism is proposed, where the three hydrogens of this methyl halide approach each other simultaneously to form H-3(+) in conjunction with singlet-triplet spin-orbit and internal conversions. The CH3Cl2+ dication can be formed after single or multiple ionizations of the already detected CH3Cl neutral molecule. Our results may be used for the interpretation of the formation of H-3(+) in laboratory and in astrophysical media.