CEPA calculations of potential energy surfaces for open-shell systems.: IV. Photodissociation of H2O in the A1B1 state

A three-dimensional potential energy surface for the photodissociation of H₂O in its lowest excited singlet state $\text{A}$¹B₁ in C_2v or $\text{A}$¹A″ in C₃ symmetry, respectively, has been calculated with quantum-chemical ab initio methods including electron correlation. The main features of the surface are discussed and qualitative explanations are given for the experimentally observed vibrational and rotational excitations of the product OH(²Π) radicals. The surface will be used in subsequent investigations of the dynamics of the H₂O photodissociation process.