The entry was reevaluated with respect to the first entry from Aug. 2004 as described in
(1) T. F. Giesen, M. E. Harding, J. Gauss, J.-U. Grabow, and H. S. P. Müller, 2020, J. Mol. Spectrosc. 371, Art. No. 111303.
Transition frequencies with ¹⁴N hyperfine splitting were taken from this work. They are more extensive than those taken from P. Förster's diploma thesis in Cologne in 1992. Frequencies without hyperfine splitting have been reported in
(2) A. J. Alexander, H. W. Kroto, and D. R. M. Walton, 1976, J. Mol. Spectrosc. 62, 175; in
(3) G. Winnewisser, M. Winnewisser, and J. J. Christiansen, 1982, Astron. Astrophys. 109, 141; and in
(4) L. Bizzocchi, C. Degli Esposti, and P. Botschwina, 2004, J. Mol. Spectrosc. 225, 145.
They cover parts of the microwave (2), millimeter wave (3), and millimeter and submillimeter wave regions (4). The hyperfine splitting should be described better in the present entry and the hyperfine free transition frequencies are slightly more certain. The calculations should be accurate enough for all observational purposes.
The ¹⁴N hyperfine splitting has been resolved in the ISM at low values of J. Therefore, separate calculations with ¹⁴N hyperfine splitting are available for J" < 20. NOTE: The partition function DOES take into account now the hyperfine splitting, but no vibrational contributions !
Vibrational correction factors for a posteriori corrections have been derived for the main isotopolog in the harmonic approximation.
The dipole moment was determined in (2).