The experimental spectrum was revisited recently. Data from the June 2009 entry are superceded by the more extensive data set from
(1) S. Spezzano, H. Gupta, S. Brünken, C. A. Gottlieb, P. Caselli, K. M. Menten, H. S. P. Müller, L. Bizzocchi, P. Schilke, M. C. McCarthy, and S. Schlemmer, 2016, Astron. Astrophys. 586, Art.-No. A110.
Predictions should be reliable enough for all astronomy observational purposes. Predictions with K_a = 4 or with uncertainties larger than 0.3 MHz should be viewed with great caution.
Non-trivial spin-statistics do not have to be considered.
The dipole moment was assumed to agree with that of the main isotopic species, see e038501.cat.