The O-H bond fission is the main radiationless deactivation pathway of phenol under UV light1.Two conical intersections or avoided crossings of the potential energy surfaces play important roles in this photodissociation dynamics — one involving the bright bound 1ππ* state(which is S1 in the Franck-Condon region)and the dark repulsive 1πσ* state(S2)and the other involving S2 and the ground 1ππ state(S1).