The lines were reported by
(1) D. T. Halfen, M. Sun, D. J. Clouthier, and L. M. Ziurys, 2012, J. Chem. Phys. 136, Art. No. 144312.
Predictions beyond 650 GHz should be viewed with caution.
At low values of N, ¹⁴N and even more so ³¹P hyperfine splitting is resolvable. Therefore, a separate prediction with ³¹P and ¹⁴N hyperfine splitting up to 200 GHz is available with separate partition function values.
The dipole moment is from an ab initio calculation by
(2) H. S. P. Müller and D. E. Woon, 2013, J. Phys. Chem. A 117, 13868.