An exchange-Coulomb model potential energy surface for the Ne–COinteraction. I. Calculation of Ne–CO van der Waals spectra

摘要

Exchange-Coulomb model potential energy surfaces have been developed for the Ne–COinteraction. The initial model is a three-dimensional potential energy surface based upon computedHeitler–London interaction energies and literature results for the long-range induction anddispersion energies, all as functions of interspecies distance, the orientation of CO relative to theinterspecies axis, and the bond length of the CO molecule. Both a rigid-rotor model potential energysurface, obtained by setting the CO bond length equal to its experimental spectroscopic equilibriumvalue, and a vibrationally averaged model potential energy surface, obtained by averaging thestretching dependence over the ground vibrational motion of the CO molecule, have beenconstructed from the full data set. Adjustable parameters in each model potential energy surfacehave been determined through fitting a selected subset of pure rotational transition frequenciescalculated for the ~(20)Ne– ~(12)C~(12)0 isotopolog to precisely known experimental values. Both potentialenergy surfaces provide calculated results for a wide range of available experimental microwave,millimeter-wave, and midinfrared Ne–CO transition frequencies that are generally far superior tothose obtained using the best current literature potential energy surfaces. The vibrationally averagedCO ground state potential energy surface, employed together with a potential energy surfaceobtained from it by replacing the ground vibrational state average of the CO stretching dependenceof the potential energy surface by an average over the first excited CO vibrational state, has beenfound to be particularly useful for computing and/or interpreting mid-IR transition frequencies in theNe–CO dimer.