ST(m1PA + m1PD) observed at 7251.5 cm-1 in absence of resonance. R(0), P(1), Q(1): rovibrational transitions of H2O monomer.
Two quanta transitions involving the vibrational excitation of both proton donor (PD) and proton acceptor (PA) molecules of the water dimer trapped in inert matrices, a particular case of similtaneous transitions, have been identified. They are characterized by weaker intensity and smaller anharmonicity than the usual combinations of PD or PA. In some cases their intensity is strongly enhanced by quasi perfect resonances with PD combinations, as proved by decoupling effects in 18O/16O isotopic mixtures.