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 Title: FITTING AN ACCURATE AB INITIO POTENTIAL ENERGY SURFACE FOR THE GROUND ELECTRONIC STATE OF H216O INCLUDING ENERGY LEVELS UP TO 37 000 cm−1 Author(s): Conway, Eamon K Contributor(s): Zobov, Nikolay F.; Yurchenko, Sergei N.; Polyansky, Oleg L.; Kyuberis, Aleksandra A.; Gordon, Iouli E Subject(s): Electronic structure, potential energy surfaces Abstract: We present our work on a new semi-empirical potential energy surface (PES) for the ground electronic state of the main water isotopologue that provides accurate energy levels up to 37 000 cm$^{-1}$. A previous attempt (Polyansky \textit{et al.} (2018)) to model the highly energetic levels has seen two independent potentials being merged together into one, however, to date, it is the only PES available that can provide the necessary wave-functions needed to compute theoretical intensities in the visible and near UV. The purpose of this work is to quantify the error associated with the underlying PES for visible near UV line intensities. An initial \textit{ab initio} PES has been fitted to 16 170 aug-cc-pCV6Z DKH2 MR-CI data points with a functional form utilizing only 251 parameters. So far, it has been refined to over 3 500 energy levels originating from both MARVEL (Furtenbacher \textit{et al.} (2007)) and experiment which include rotational levels 0, 1, 2, 3, 4 and 5. Approximately 99\% of all possible energy levels have been included in the refining process. The RMS deviation for all levels is currently 0.08 cm$^{-1}$. It is generally understood that the dipole moment surface (DMS) provides the largest uncertainty to computed intensities, however our results indicate that the error associated with the PES is not negligible, even for the fundamental bands where it can rise to 1\%. That number is some times higher for other bands. This becomes significant in interpreting the atmospheric spectra where the quality of the modern spectrometers places high demands on the accuracy of reference spectroscopic data. Through comparisons with the latest available experiments and observations we provide an analysis on the sensitivity of line intensities from the infrared to the near UV. Issue Date: 2019-06-19 Publisher: International Symposium on Molecular Spectroscopy Genre: Conference Paper / Presentation Type: Text Language: English URI: http://hdl.handle.net/2142/104351 DOI: 10.15278/isms.2019.WD03 Rights Information: Copyright 2019 Eamon K Conway Date Available in IDEALS: 2019-07-152020-01-25
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