The g'Gg' conformer is the lower energy form; the gG'g conformer is calculated to be about 2.4 kJ/mol higher in energy. Its rotational spectrum was recorded between 2 and 26 GHz as well as between 75 and 110 GHz by
(1) B. E. Arenas, M. Fatima, C. Pérez, S. Fischer, A. L. Steber, and M. Schnell, 2021, Astrophys. J. 912, Art. No. 90.
The present analysis takes also into account high-J MW data from
(2) B. H. Ellingsen, K.-M. Marstokk, and H. Møllendal, 1978, J. Mol. Struct. 48, 9.
The parameter set differs from the one in (1) as a consequence. The calculations should be sufficiently accurate for observations in cold and possibly luke-warm sources. Frequencies with calculated uncertainties exceeding 0.2 MHz should be viewed with caution.
¹⁴N hyperfine splitting may be resolvable in cold sources at low quantum numbers. Therefore, a separate hyperfine calculation is provided for J ≤ 10 below 52 GHz. NOTE: The partition function does take into account the spin multiplicity of the ¹⁴N nucleus !
The two conformers were treated as separate species in (1) which may be appropriate at low temperatures. The partition function below refers to the ground vibrational state only. Vibrational correction factors for a posteriori corrections will be provided later.
It may be useful to treat the two forms as being in local thermodynamic equilibrium at higher temperatures. Corresponding conformational correction factors with contributions for gG'g for a posteriori corrections of the rotational partition function of g'Gg' are given. Alternatively, the file contains also the ground state partition of both conformers which may be used in combination with an corresponding catalog file along with a adjusted hyperfine calculation.
The experimental dipole moment components are from (2).