A hyperfine-resolved spectroscopic model for vanadium monoxide (⁵¹V¹⁶O)

Abstract

Vanadium monoxide (${}^{51}$V${}^{16}$O) is believed to play an important role in the atmospheres of hot-Jupiters, but high-resolution studies have so far failed to detect it, at least in part because of the inaccuracy of available lists. It is likely that the large hyperfine splittings in the spectra of VO, arising from the large nuclear spin $I=\frac{7}{2}$ of the ${}^{51}$V atom, has contributed to the non-detections with the current hyperfine-unresolved VOMYT line list. To aid in the production of a new line list, a fully hyperfine-resolved spectroscopic model has been constructed which includes 15 low-lying electronic states (6 quartets and 9 doublets) of VO with the inclusion of hyperfine couplings based on use of the new, hyperfine-resolved version of the diatomic variational nuclear motion programme Duo. The new spectroscopic model is refined against empirical Marvel energies derived from experimental transitions, and hyperfine couplings are fit for the 3 electronic states for which hyperfine effects have been resolved in lab spectra. This model is used to assign some previously identified perturbations.

GRAPHICAL ABSTRACT

Keywords:

• Hyperfine coupling
• variational nuclear motion
• spectroscopy
• potential energy curves
• vanadium monoxide

Acknowledgments

We thank Eileen Döring for providing her experimental results prior to publication.

Data availability

The Duo input file used to compute the new model and the MARVEL transitions and energy levels used for refining the model are given as supporting material. The Duo input file contains descriptions of all potential energy and coupling curves in the model and can be used to recreate the figures presented here. The Duo code is freely available at https://github.com/Trovemaster/Duo. The version used in this work was compiled from commit e88cbb4 on May 25 2023.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme through Advance Grant number 883830 and the UK STFC under grant ST/R000476/1. The final calculations of this work were performed using the DiRAC Data Intensive service at Leicester, operated by the University of Leicester IT Services, which forms part of the STFC DiRAC HPC Facility (https://dirac.ac.uk). The equipment was funded by BEIS capital funding via STFC capital grants ST/K000373/1 and ST/R002363/1 and STFC DiRAC Operations grant ST/R001014/1. DiRAC is part of the National e-Infrastructure.