ROTATION VIBRATION ENERGIES OF FHF- AND CLHCL- FROM HIGH-LEVEL CORRELATED CALCULATIONS OF POTENTIAL-ENERGY SURFACES

Fully variational calculations of the rotation-vibration energy levels of FHF- and ClHCl- and carried out using high-level correlated potential energy surfaces. The corresponding results are compared with those obtained in a simplified model which takes into account only the H-bond stretching vibrations. The differences between the results of the two models are small (almost-equal-to 10 cm-1) for the symmetric stretching frequency-nu-1. A large difference (almost-equal-to 100 cm-1) from the stretch-only approximation is found for the asymmetric stretching frequency-nu-3 and indicates a strong anharmonic coupling between the nu-2 and nu-3 modes.