THEORETICAL-STUDIES OF SPIN-FORBIDDEN RADIATIONLESS DECAY IN POLYATOMIC SYSTEMS .2. RADIATIONLESS DECAY OF A-N2O2

The stability with respect to spin-forbidden radiationless decay of the previously reported [J. Chem. Phys. 88, 7248 (1988)] asymmetric dimer of NO, N-N-0-0 (a-N2O2) is considered. The spin-allowed decay channel a-N2O2(1A') --> N2O(X 1SIGMA') +O(1D) is endoergic. However, the spin-forbidden decay channel a-N2O2 (1A') --> N2O (X 1SIGMA+) +O(3P) is exoergic. Large scale multireference configuration interaction wave functions, approximately 300 000-1 400 000 configuration state functions, based on double zeta polarization and triplet zeta polarization bases are used to study this process. The minimum energy crossing of the ground singlet 1A' state and the lowest excited triplet 3A'' state was determined as was the interstate spin-orbit coupling. This electronic structure data was used in the context of a simple one-dimensional model to show that a-N2O2 is rapidly predissociated to N2O (X 1SIGMA+) and O(3P).