Potential energy curves for the dissociation of the Rydberg H3O radical into (H2O+H)

Potential energy curves of the ground and low-lying excited states for the dissociation of the Rydberg H3O radical into (H2O+H) have been calculated using ab initio Hartree–Fock and singly and doubly excited configuration interaction methods with a large basis set. Under the C2v symmetry constraints, the ground (H3O+)(e−)3s radical adiabatically correlates to the repulsive state emerging from an antibonding interaction of the [H2O(1A1)+H(2S)] asymptote. The ground potential energy barrier of ≃0.12 eV formed by an avoided curve crossing is found at R(OH)≃1.213 Å. The potential energy gap between H3O and (H2O+H) is ≃0.86 eV.