Photodissociation of water. I. Electronic structure calculations for the excited states

Results of ab initio calculations for the four lowest excited states of bot h A' and A' have been discussed. In the multireference configuration intera ction calculations, a large Rydberg basis set has been used. Three-dimensio nal potential energy surfaces, and matrix elements of the transition dipole moment between the excited states and the ground X state, and the electron ic angular momentum operator between the A state and the B and X states hav e been presented. The calculations show that above about 124 nm the photodi ssociation can be well described by the three lowest electronic states, X, A, and B. The ab initio results of matrix elements of the electronic angula r momentum operator allow a realistic nonadiabatic treatment of the photodi ssociation in the B band. At wavelengths smaller than about 124 nm, the dyn amics will be more complicated because of the coupling between various elec tronic states. (C) 2000 American Institute of Physics. [S0021-9606(00)30913 -8].