N2O32- photodissociation was investigated using the CASSCF energy gradient techniques. After the N2O32- dianion is populated in the S-1 state, the system can undergo different routes. One route involves radiationless decay via an intersystem crossing T-1/S-1 to the T, minimum intermediate. Then through the transition state TS (T-1) and the T-1/S-0 to the ground state surface. The other route involves the S-1/S-0 conical intersection. These results show that the main product NO- of the efficient photodissociation is singlet-state rather than triplet ((3)Sigma(-)) state. Our calculated results are in close agreement with experimental observations. (c) 2006 Elsevier B.V. All rights reserved.