The microwave data of the first entry of Dec. 2021 were contributed by
(1) L. H. Scharpen and V. W. Laurie, 1965, J. Chem. Phys. 43, 2765.
while the millimeter-wavelength data was taken from
(2) L. Bonah, B. Helmstaedter, J.-C. Guillemin, S. Schlemmer, and S. Thorwirth, 2025, J. Mol. Spectrosc. 408, Art. No. 111967.
The data fit to roughly 15 kHz using an S-reduced Hamiltonian.
The calculations were truncated at J = 50 and at 500 GHz. They should be sufficient for all observational purposes. Transition frequencies with calculated uncertainties exceeding 0.1 MHz should be viewed with caution.
Spin-statistical weight ratios of 9 : 7 for levels with K_a being even and odd, respectively, have been taken into account.
The dipole moment was assumed to agree with that of the main isotopolog, see e066520.cat, but it is along the a-axis.