ExoMol line lists -- LIII: Empirical Rovibronic spectra of Yttrium Oxide (YO)

TL;DR

This paper presents comprehensive empirical line lists for yttrium oxide (YO), covering multiple electronic states and isotopologues, refined through experimental data and advanced ab initio calculations, to aid astrophysical and spectroscopic research.

Contribution

It provides the first detailed empirical line lists for YO with refined theoretical models and non-adiabatic couplings, enhancing spectral data accuracy for this molecule.

Findings

Line lists cover 6 electronic states up to 60000 cm$^{-1}$

Refined spectroscopic model with experimental and ab initio data

Includes lifetimes and diabatic representations

Abstract

Empirical line lists for the open shell molecule $^{89}$Y$^{16}$O (yttrium oxide) and its isotopologues are presented. The line lists cover the 6 lowest electronic states: $X {}^{2}\Sigma^{+}$, $A {}^{2}\Pi$, $A' {}^{2}\Delta$, $B {}^{2}\Sigma^{+}$, $C {}^{2}\Pi$ and $D {}^{2}\Sigma^{+}$ up to 60000 cm$^{-1}$ ($<0.167$ $\mu$m) for rotational excitation up to $J = 400.5$. An \textit{ab initio} spectroscopic model consisting of potential energy curves (PECs), spin-orbit and electronic angular momentum couplings is refined by fitting to experimentally determined energies of YO, derived from published YO experimental transition frequency data. The model is complemented by empirical spin-rotation and $\Lambda$-doubling curves and \textit{ab initio} dipole moment and transition dipole moment curves computed using MRCI. The \textit{ab initio} PECs computed using the complete basis set limit extrapolation and the CCSD(T) method with its higher quality provide an excellent initial approximation for the refinement. Non-adiabatic coupling curves for two pairs of states of the same symmetry $A$/$C$ and $B$/$D$ are computed using a state-averaged CASSCF and used to built diabatic representations for the $A {}^{2}\Pi$, $C {}^{2}\Pi$, $B {}^{2}\Sigma^{+}$ and $D {}^{2}\Sigma^{+}$ curves. Calculated lifetimes of YO are tuned to agree well with the experiment, where available. The BRYTS YO line lists for are included into the ExoMol data base (www.exomol.com).