Dipole moment and intensities in the electronic ground state of NH3: Bridging the gap between ab initio theory and spectroscopic experiment

摘要

We report here theoretical values for the transition moments of an extensive set of vibrationalbands in the electronic ground state of 14NH3. For selected bands, we have further made detailedsimulations of the rotational structure. The calculations are carried out by means of recentlydeveloped computational procedures for describing the nuclear motion and are based on a high-level ab initio potential energy surface, and high-level dipole moment surfaces, for the electronicground state of NH3. The reported theoretical intensity values are compared to, and found to agreevery well with, corresponding experimental results. It is believed that the computational method, inconjunction with high-quality ab initio potential energy and dipole moment surfaces, can simulaterotation-vibration spectra of XY3 pyramidal molecules prior to observation with su±cient accuracyto facilitate the observation of these spectra. By degrading the accuracy of selected elements of thecalculations, we have also investigated the in°uence of customary approximations on the computedintensity values.