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Title:Line List For The Lowest Four States Of No
Author(s):Qu, Qianwei
Contributor(s):Tennyson, Jonathan; Yurchenko, Sergei N.
Abstract:We computed an accurate line list, called \texttt{XABC}, for nitric oxide (NO) which covers its pure rotational, vibrational and rovibronic spectra belonging to the lowest four electronic states of NO, i.e. X\,$^2\Pi$, A\,$^2\Sigma^+$, B\,$^2\Pi$ and C\,$^2\Pi$. \texttt{XABC} is a major extension and update of the ExoMol \texttt{NOname} line list which was calculated within the X\,$^2\Pi$ state of NO. As first step we built a spectroscopic model which represents the rovibronic structure of A\,$^2\Sigma^+$, B\,$^2\Pi$, C\,$^2\Pi$ states of NO. Empirical energy levels for the three electronic states are determined using the a combination of the MARVEL procedure and \textit{ab initio} calculations, and the available experimental data are critically evaluated. {\it Ab inito} methods which deal simultaneously with the Rydberg-like A\,$^2\Sigma^+$ and C\,$^2\Pi$, and the valence B\,$^2\Pi$ state are tested. Methods of modeling the sharp avoided crossing between the B\,$^2\Pi$ and C\,$^2\Pi$states are tested. A rovibronic Hamiltonian matrix is constructed using variational nuclear motion program \textsc{Duo} whose eigenvalues are fitted to the MARVEL energy levels. The matrix also includes coupling terms obtained from the refinement of the \textit{ab initio} potential energy and spin-orbit coupling curves. Calculated and observed energy levels agree well with each other, validating the applicability of our method and providing a useful model for this open shell system. This part has been published in \textit{J. Chem. Phys.} A mixture of empirical and theoretical electronic transition dipole moments are used for the final calculation of NO rovibronic transitions belong to the A\,$^2\Sigma^+$ -- X\,$^2\Pi$, B\,$^2\Pi$ -- X\,$^2\Pi$ and C\,$^2\Pi$ -- X\,$^2\Pi$ which correspond to the $\gamma$, $\beta$ and $\delta$ band systems, respectively, as well as minor improvements to transitions within the X\,$^2\Pi$ ground state. Our model generates a high-accuracy NO ultraviolet line list covering the complicated regions where the B\,$^2\Pi$ -C\,$^2\Pi$ states interact. Technical details of this part are given in the \texttt{XABC} line list paper submitted to \textit{Mon. Not. Roy. Astron. Soc.}. \texttt{XABC} provides comprehensive data for $\lambda > 160$ {nm} ($\tilde{\nu} <$ 63000 cm$^{-1}$) for the analysis of atmospheric NO on Earth, Venus or Mars, other astronomical observations and applications. It is available via
Issue Date:2021-06-23
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper / Presentation
Date Available in IDEALS:2021-09-24

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