The observed transitions were taken from
(1) L. Margulès, R. Motiyenko, K. Demyk, B. Tercero, J. Cernicharo, M. Sheng, M. Weidmann. J. Gripp, H. Mäder, and J. Demaison, 2009, Astron. Astrophys. 493, 565.
Some microwave transition were already reported in
(2) H. M. Heise, H. Mäder, and H. Dreizler, 1976, Z. Naturforsch. 29a, 1228.
A small number of transitions with residuals considerably larger than the uncertainties have been omitted from the fit.
Predictions with uncertainties exceeding 0.5 MHz should be viewed with caution.
The partition function values below refer to the ground vibrational state only. Vibrational correction factors have been derived for the main isotopolog in the harmonic approximation. Errors caused by isotopic substitution are small.
The dipole moment was assumed to agree with that of the main isotopic species, see e055502.cat. Some small deviations are expected to occur, but these are probably within the experimental uncertainties.