Potential energy surfaces of the first three singlet states of

The photodissociation of CH 3 Cl is an important source of atmospheric chlorine atoms. To more fully understand this reaction, potential energy surfaces of the ground state X 1 A ′ and the first two excited singlets ( 2 1 A ′ and 1 1 A ″ , corresponding to the degenerate 1 E at the ground state C 3 v equilibrium geometry) of CH 3 Cl have been constructed through ab initio Complete Active Space SCF calculations. A X 1 A ′ / 2 1 A ′ conical intersection was located, and the importance of this feature in the photolysis of the C–H bond after photoexcitation at 193 nm is discussed.