Potential energy surfaces of the first three singlet states of CH3Cl

The photodissociation of CHCl is an important source of atmospheric chlorine atoms. To more fully understand this reaction, potential energy surfaces of the ground state X1A^' and the first two excited singlets ( 21A^' and 11A^″, corresponding to the degenerate 1E at the ground state C_3v equilibrium geometry) of CHCl have been constructed through ab initio Complete Active Space SCF calculations. A X1A^'/21A^' 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.