ON THE DETERMINATION OF POTENTIAL-ENERGY SURFACES OF SPECTROSCOPIC ACCURACY

The application of ab initio potential energy surfaces and surfaces fitted to spectroscopically determined rotation-vibration levels of triatomic molecules are considered with particular attention to H-3(+) and (H2O)-O-16. Variational treatments of nuclear motion allow these surfaces to be determined with near spectroscopic accuracy and the breakdown of the Born-Oppenheimer (BO) approximation to be quantified. Methods for determining the BO adiabatic correction both ab initio and from spectroscopic data are described.