ExoMol line lists – LIII: empirical rovibronic spectra of yttrium oxide

Abstract

Empirical line lists BRYTS for the open shell molecule 89Y16O (yttrium oxide) and its isotopologues are presented. The line list covers the 6 lowest electronic states: X 2Σ+, A 2Π, A′ 2Δ, B 2Σ+, C 2Π and D 2Σ+ up to 60 000 cm−1 (<0.167 μm) for rotational excitation up to J = 400.5. An 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 Λ-doubling curves and ab initio dipole moment and transition dipole moment curves computed using MRCI. The 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 build diabatic representations for the A 2Π, C 2Π, B 2Σ+ and D 2Σ+ curves. The experimentally derived energies of 89Y16O utilised in the fit are used to replace the corresponding calculated energy values in the BRYTS line list. Simulated spectra of YO show excellent agreement with the experiment, where it is available. Calculated lifetimes of YO are tuned to agree well with the experiment, where available. The BRYTS YO line lists are available from the ExoMol database (www.exomol.com).

Numerical Equivalence of Diabatic and Adiabatic Representations in Diatomic Molecules

“…This study aims to show the numerical equivalence of the adiabatic and diabatic representations in nuclear motion calculations of rovibronic energies and spectral properties for two selected diatomic systems, represented by two coupled electronic states: yttrium oxide (YO) and carbon monohydride (CH) molecules illustrated in Figure . YO shows avoided crossings between the B 2 Σ + , D 2 Σ + and A 2 Π, C 2 Π states as described by Yurchenko et al YO has broad scientific interest, having been observed in stellar spectra, − and found use in solar furnaces , and magneto-optical traps. , YO is a complex system showing many low-lying electronic states; accurate descriptions of its avoided crossings will be valuable to works in several fields. CH is one of the most studied free radicals because it occurs in such a wide variety of environments: it has been observed in flames, , solar − and stellar spectra, − spectra of comets, ISM, − and molecular clouds …”

“…As an example of a two-state system with narrow, coupled-bound electronic curves, we chose the ab initio PEC curves of the B 2 Σ + and D 2 Σ + states of YO from Smirnov et al 90 with the NAC from Yurchenko et al 53 …”