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The Z stereo isomer is the higher energy form;
the E form is calculated to be 3.16 kJ/mol
lower in energy.
The rotational spectrum was recorded between
158 and 470 GHz by
(1) L. Margulès, A. Remijan, A. Belloche, R. A.
Motiyenko, B. A. McGuire, C. Xue, H. S. P. Müller,
R. T. Garrod, K. M. Menten, and J.-C. Guillemin,
2022, Astron. Astrophys. 663, Art. No. A132.
The parameter set differs very slightly from the one in (1); an estimate
of HK was kept fixed and HKJ
was released because LKKJ was fit.
No hyperfine structure (HFS) splitting was resolved,
and it may be too small to be resolved in astronomical
observations. The calculations should be sufficiently
accurate for all observational purposes. Frequencies with
calculated uncertainties exceeding 0.2 MHz should be
viewed with caution.
The two stereo isomeric forms were treated as separate
species in (1) which is certainly appropriate at low
temperatures. The partition function below refers to
the ground vibrational state only.
Vibrational correction factors for a posteriori corrections
were derived in (1) in the harmonic approximation.
It may be useful to treat the two forms as being in local
thermodynamic equilibrium at higher temperatures. Corresponding
frequency calculations along with
vibrational correction factors with contributions for Z for
a posteriori corrections of the rotational partition function of E
were derived in the harmonic approximation.
The dipole moment components are from a quantum-chemical
calculation in (1).
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