Approaching the full set of energy levels of water

We report here measurements of rovibrational levels in the electronic ground state of water at the previously inaccessible energies above 26,000 cm-1. The use of laser double-resonance overtone excitation extends this limit to 34,200 cm-1, which corresponds to 83% of the water dissociation energy. We use experimental data to generate a semi-empirical potential energy surface that now allows prediction of water levels with sub-cm-1 accuracy at any energy up to the new limit.