Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spectroscopy of YO from first principles   We report an ab initio study on the spectroscopy of the open-shell diatomic
molecule yttrium oxide, YO. The study considers the six lowest doublet states,
$X\,{}^{2}\Sigma^{+}$, $A\,{}^{2}\Pi$, $C\,{}^{2}\Pi$, $A'\,{}^{2}\Delta$,
$B\,{}^{2}\Sigma^{+}$, $D\,{}^{2}\Sigma^{+}$ and a few higher-lying quartet
states using high levels of electronic structure theory and accurate nuclear
motion calculations. The coupled cluster singles, doubles, and perturbative
triples, CCSD(T), and multireference configuration interaction (MRCI) methods
are employed in conjunction with a relativistic pseudopotential on the yttrium
atom and a series of correlation-consistent basis sets ranging in size from
triple-$\zeta$ to quintuple-$\zeta$ quality. Core-valence correlation effects
are taken into account and complete basis set limit extrapolation is performed
for CCSD(T). Spin-orbit coupling is included through the use of both MRCI
state-interaction with spin-orbit (SI-SO) approach and four-component
relativistic equation-of-motion CCSD calculations. Using the ab initio data for
bond lengths ranging from 1.0 to 2.5 A, we compute 6 potential energy, 12
spin-orbit, 8 electronic angular momentum, 6 electric dipole moment and 12
transition dipole moment (4 parallel and 8 perpendicular) curves which provide
a complete description of the spectroscopy of the system of six lowest doublet
states. The Duo nuclear motion program is used to solve the coupled nuclear
motion Schr\"{o}dinger equation for these six electronic states. The spectra of
$^{89}$Y$^{16}$O simulated for different temperatures are compared with several
available high resolution experimental studies; good agreement is found once
minor adjustments are made to the electronic excitation energies.

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The categories of this paper are: stat
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The categories of this paper are: math-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: quant-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: nlin
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The categories of this paper are: cond-mat
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The categories of this paper are: econ
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The categories of this paper are: eess
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The categories of this paper are: nucl-th
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The categories of this paper are: math
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The categories of this paper are: adap-org
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The categories of this paper are: plasm-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: patt-sol
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The categories of this paper are: chao-dyn