Molecular dimers of methane clathrates: ab initio potential energy surfaces and variational vibrational states

<div>Mass-dependent diagonal Born-Oppenheimer corrections (DBOC) to the ab initio electronic ground state potential energy surface for tseveral isotopologues of the ozone molecule are reported for the first time. The comparison with experimental band centers shows a significant improvement of the accuracy with respect to the best Born-Oppenheimer (BO) ab initio calculations reducing the total root-mean-squares (calculated - observed) deviations by about factor of two. For the set of 16O3 vibrations up to five bending and four stretching quanta, the mean (calculated - observed) deviations drop down from 0.7 cm-1 (BO) to about 0.1 cm-1, with the most pronounced improvement seen for bending states and for mixed bend-stretch polyads. In case of bending band centers directly observed under high spectral resolutions, the errors are reduced by more than order of magnitude from observed levels, approaching nearly experimental accuracy. New sets of ab initio vibrational states can be used for improving spectroscopic effective models for analyses of observed high-resolution spectra, particularly in cases of accidental resonances with ,,dark'' states requiring accurate theoretical predictions.</div>

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Diagonal Born-Oppenheimer Corrections to the Ground Electronic State Potential Energy Surfaces of Ozone: Improvement of Ab Initio Vibrational Band Centers for the 16O3, 17O3 and 18O3 Isotopologues

10.26434/chemrxiv.12251138 ◽

2020 ◽

Author(s):

Attila Tajti ◽

Péter Szalay ◽

Roman V. Kochanov ◽

Vladimir G. Tyuterev

Keyword(s):

Potential Energy ◽

Ab Initio ◽

Potential Energy Surfaces ◽

Vibrational States ◽

Theoretical Predictions ◽

Order Of Magnitude ◽

State Potential ◽

Effective Models ◽

Energy Surfaces ◽

Mass Dependent

<div>Mass-dependent diagonal Born-Oppenheimer corrections (DBOC) to the ab initio electronic ground state potential energy surface for tseveral isotopologues of the ozone molecule are reported for the first time. The comparison with experimental band centers shows a significant improvement of the accuracy with respect to the best Born-Oppenheimer (BO) ab initio calculations reducing the total root-mean-squares (calculated - observed) deviations by about factor of two. For the set of 16O3 vibrations up to five bending and four stretching quanta, the mean (calculated - observed) deviations drop down from 0.7 cm-1 (BO) to about 0.1 cm-1, with the most pronounced improvement seen for bending states and for mixed bend-stretch polyads. In case of bending band centers directly observed under high spectral resolutions, the errors are reduced by more than order of magnitude from observed levels, approaching nearly experimental accuracy. New sets of ab initio vibrational states can be used for improving spectroscopic effective models for analyses of observed high-resolution spectra, particularly in cases of accidental resonances with ,,dark'' states requiring accurate theoretical predictions.</div>

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