Accurate MW laboratory data were reported by
(1) B. A. McGuire, M.-A. Martin-Drumel, K. L. K. Lee, J. F. Stanton, C. A. Gottlieb, and M. C. McCarthy 2018, Phys. Chem. Chem. Phys. 20, 13870.
Starting spectroscopic parameters were derived from the main isotopic species by scaling parameters by appropriate powers of the ratios of the isotopolog versus the main species. The rotational parameter B was fit.
Since the reasonable assumption that λ does not change upon isotopic substitution will not hold strictly, calculations of most fine structure components with J = N or N – 1 should be vied with caution. Transition frequencies above 50 GHz should be viewed with some caution throughout.
The dipole moment was assumed to agree with that of the main isotopolog, see e80501.cat.