Transition frequencies have been reported by
(1) M. C. McCarthy, L. Zou, and M.-A. Martin-Drumel, 2017, J. Chem. Phys. 146, Art. No. 154301.
Additional frequencies are from
(2) K. N. Crabtree, M.-A. Martin-Drumel, G. G. Brown, S. A. Gaster, T. M. Hall, and M. C. McCarthy, 2016, J. Chem. Phys. 144, Art. No. 124201.
The reported uncertainties from both sources were deemed to be slightly conservative; they have been adjusted. Predictions were truncated at J = 70 and K_a = 1 because of limitations in the experimental data. Larger quantum numbers were accessed for the determination of the partition function. The predictions should be sufficient for the identification of the molecule in dark clouds. Predictions with uncertainties larger than 0.05 MHz should be viewed with caution.
The dipole moment is from an ab initio calculation in (1).