Potential energy curves of the ground and excited states for the dissociation of the Rydberg H2O radical into (OH + H-2) have been calculated using ab initio Hartree-Fock (HF) and singly and doubly excited configuration interaction (SDCI) methods with a large basis set including Rydberg basis functions. Under C-2v symmetry constraint, the ground (2)A(1) potential curve of (H3O+)(e(-))(3s) adiabatically correlates to [OH(A(2)Sigma(+)) + H-2(X(1)Sigma(g)(+))]. while the first excited E-2 state of (H3O+)(e(-))(3s) correlates to [OH(X(2)Pi) + H-2(X(1)Sigma(g)(+))]. The avoided curve crossings between the attractive diabatic states emerging from the cation-anion pair of [OH+ + H-2(-)] and the repulsive diabatic states from antibonding orbitals of [OH. + H-2] occurs around R-OH similar or equal to 1.8 Angstrom. (C) 2002 Elsevier Science B.V. All rights reserved.