ON THE NATURE OF THE REACTION-PATH FROM THE 2B2 STATIONARY POINT TO THE (X)TILDE2A1 MINIMUM ON THE LOWEST 2A' POTENTIAL-ENERGY SURFACE OF NO2

The lowest X2A' potential energy surface of NO2 exhibits three stationary points: the 2A1 ground state minimum, the 2-PI(u) point at linearity and, at a smaller bond angle, a B-2(2) stationary point. The structural nature of the latter has been a subject of controversy in the literature, and thus we have employed recently published diabatic potential energy functions to study this question. Our findings indicate a saddle character for this point, and a description of the trough leading without energy barrier to the 2A1 minimum is also given. It is also pointed out, however, that because the vibronic coupling between the X and A states is so strong, it will be virtually impossible to settle this issue by experimental means.