Vibrational energy levels of water

摘要: Abstract Several quartic force fields and a full sextic anharmonic field for H 2 O have been determined from high-quality ab initio calculations, the highest at aug-cc-pVQZ CCSD(T) level of theory. These used to determine vibrational excited state band origins up 15000 cm −1 above zero-point level, using both perturbation-resonance approach variational approach. An optimised has obtained by least squares refinement our best results fit observed overtone levels 5 symmetrically substituted isotopomers water (H 16 O, 17 18 D T O) with an rms error less than 10 , model calculation. Predicate was provide loose constraint refined results. The prove viability use in larger molecular systems also highlight some its weaknesses.