A quantum-mechanical study of the predissociation of H2O(+) (B̃ (2)B2) is carried out by using wave packet propagations on ab initio potential energy surfaces connected by nonadiabatic couplings. The simulations show that within the first 30 fs 80% of the initial wave packet is transferred from the B̃ (2)B2 to the à (2)A1 electronic state through a conical intersection. A much slower transfer (in the ps time scale) from the à (2)A1 to the X̃ (2)B1 state due to a Renner-Teller coupling determines the fragmentation branching ratios, which are in accordance with the experimental measurements.
Keywords: ab initio potentials; branching ratio; conical intersection; fragmentation; water cation; wave packet propagations.