The experimental millimeter and lower submillimeter lines are from
(1) J. M. Vrtilek, C. A. Gottlieb, E. W. Gottlieb, W. Wang, and P. Thaddeus, 1992, Astrophys. J. 398, L73.
Additional lower frequency data with hyperfine structure splitting were taken from
(2) E. Kim, H. Habara, and S. Yamamoto, 2002, J. Mol. Spectrosc. 212, 83.
The spin-orbit splitting was taken from
(3) S.-G. He and D. C. Clouthier, 2005, J. Chem. Phys. 123, Art. No. 014317.
Uncertainty estimates were quite optimistic in (1) and slightly so in (2). The uncertainties of small number of lines from both sources were increased, and a few lines with large residuals from (1) were omitted.
The prediction should be reliable throughout. Slight caution may be advisable for predictions much higher than 400 GHz.
The ¹H hyperfine splitting may be resolved for lower J transitions. Therefore, a separate hyperfine calculation up to J' = 4.5 is provided. The ¹H spin multiplicity of 2 was considered in the calculation of the partition function !
The dipole moment is from an ab initio calculation from
(4) C. Puzzarini, 2008, Chem. Phys. 346, 45.