THE SINGLET AND TRIPLET-STATES OF PHENYL CATION - A HYBRID APPROACH FOR LOCATING MINIMUM ENERGY CROSSING POINTS BETWEEN NONINTERACTING POTENTIAL-ENERGY SURFACES

The phenyl cation is known to have two low-energy minima, correspondin g to (1)A(1) and B-3(1) states, the first of which is more stable by c a. 25 kcal/mol. The minimum energy crossing point between these two su rfaces, located at various levels including a hybrid method first desc ribed here, lies just above the minimum of the triplet, 0.12 kcal/mol at the CCSD(T)/cc-pVDZ//B3LYP/SV level, and there is significant spin- orbit coupling between the surfaces at this point. On the basis of the se results, the lifetime of the triplet is expected to be very short.