The experimental lines were taken from
(1) A. Bouchy, 1972, PhD thesis, University Nancy; from
(2) A. Bouchy, J. Demaison, G. Roussy, and J. Barriol, 1973, J. Mol. Struct. 18, 211; and from
(3) G. Schwahn, R. Schieder, M. Bester, and G. Winnewisser, 1986, J. Mol. Spectrosc. 116, 263.
Since K_a = 1 ↔ 0 were the only b-type transitions observed, predictions for this type of transitions should be viewed with caution at higher K_a. All predictions above about 350 GHz should be viewed with caution.
The ¹⁴N hyperfine splitting has been resolved resolvable at lower frequencies. Therefore, a calculation with hyperfine structure is available up to 50 GHz for selected transitions with J up to 25.
Note: The partition function takes into account the ¹⁴N hyperfine splitting.
The dipole moment is from (2).