Fig. 2. Structures of the water dimer obtained from CASPT2(4,6) calculations in the S0 and S1 states; G2-[1] = equilibrium structure in the S0 state; E2-[1]‡ = transition structure in the S1 state; E2-[2] = equilibrium structure in the S1 state; E2-[3] = O–H dissociated structure in the S1 state. Distances are in Å and the value of the HOMO and LUMO isosurfaces is 0.065. ΔE = Relative energies with respect to the total energy of structure G2-[1]; μ = dipole moment.
