A CASSCF study on photodissociation of the dianion

N 2 O 3 2 - photodissociation was investigated using the CASSCF energy gradient techniques. After the N 2 O 3 2 - dianion is populated in the S1 state, the system can undergo different routes. One route involves radiationless decay via an intersystem crossing T1/S1 to the T1 minimum intermediate. Then through the transition state TS (T1) and the T1/S0 to the ground state surface. The other route involves the S1/S0 conical intersection. These results show that the main product NO− of the efficient photodissociation is singlet-state rather than triplet (3Σ−) state. Our calculated results are in close agreement with experimental observations.