Non adiabatic interactions in the symmetric ring opening process of dioxirane

The first two electronic states of 1A1 symmetry in the symmetric ring opening unimolecular reaction, leading from the dioxirane molecule to the dioxymethane diradical, are investigated by ab initio CI calculations. Due to the presence of a strong non-adiabatic interaction between the ground state and the first excited state in the vicinity of the transition state, the diabatic representation is adopted. The nuclear motion problem for the ring opening is solved with the diabatic potentials. The resulting wavefunctions are good approximations to the vibronic state which scarcely mix the two diabatic electronic states. It is therefore argued that the formation of the diradical by excitation of the OCO bending of dioxirane is relatively unlikely.