Calculation of Rotation–Vibration Energy Levels of the Water Molecule with Near-Experimental Accuracy Based on an ab Initio Potential Energy Surface

摘要: A recently computed, high-accuracy ab initio Born–Oppenheimer (BO) potential energy surface (PES) for the water molecule is combined with relativistic, adiabatic, quantum electrodynamics, and, crucially, nonadiabatic corrections. Calculations of ro-vibrational levels are presented several isotopologues and shown to have unprecedented accuracy. purely calculation reproduces some 200 known band origins associated seven a standard deviation (σ) about 0.35 cm–1. Introducing three semiempirical scaling parameters, two affecting BO PES one controlling effects, reduces σ below 0.1 further rotational parameter gives better than cm–1 all observed up J = 25. We conjecture that closed-shell molecules roughly same number electrons as water, such NH3, CH4, H3O+, could be calculated this accuracy using an analogous procedur...