The Hamiltonian is described in
(1) H. S. P. Müller, H. Klein, S. P. Belov, G. Winnewisser, I. Morino, K. M. T. Yamada, and S. Saito 1999, J. Mol. Spectrosc. 195, 177.
The lines used in the fit include submillimeter, and terahertz data from (1) and millimeter and submillimeter lines from
(2) M. Tonooka, S. Yamamoto, K. Kobayashi, and S. Saito, 1997, J. Chem. Phys. 106, 2563.
Microwave optical double resonance (MODR) data, mostly magnetic dipole transitions, from
(3) J. M. Cook, G. W. Hills, and R. F. Curl, Jr., 1977, J. Chem. Phys. 67, 1450;
(4) G. W. Hills, R. S. Lowe, J. M. Cook, and R. F. Curl, Jr., 1978, J. Chem. Phys. 68, 4073; and from
(5) G. W. Hills and J. M. Cook, 1982, J. Mol. Spectrosc. 94, 456 were also used.
However, except for the strongest components of one electric dipole transition these lines have not been merged. Furthermore, far infrared transitions from
(6) I. Morino and K. Kawaguchi, 1997, J. Mol. Spectrosc 182, 428
and far-infrared laser side-band measurements from
(7) H. Ozeki and S. Saito, 1998, J. Mol. Spectrosc. 192, 183
were also used in the fit, but not merged because of their large uncertainties. The new entry employs additionally transitions near 2 THz measured with microwave accuracy. These were taken from
(8) R. Gendriesch, F. Lewen, G. Winnewisser, and H. S. P. Müller, 2001, J. Mol. Struct. 599, 293.
Also used in the fit were ground state combination differences published in (8) which are from an investgation of the NH₂ electronic spectrum by
(9) R. N. Dixon, S. J. Irving, J. R. Nightingale, and M. Vervloet, 1991, J. Chem. Soc. Faraday Trans. 87, 2121.
The dipole moment was determined by
(10) J. M. Brown, S. W. Chalkley, and F. D. Wayne 1979, Mol. Phys. 38, 1521.
At low temperatures, it may be necessary to discern between ortho-NH₂ and para-NH₂. The ortho states are described by K_a + K_c even, the para states by K_a + K_c odd. There are three times as many levels for ortho-NH₂ than there are for para-NH₂. Thus, for transitions with unresolved ¹H hyperfine splitting the nuclear spin-weight ratio is 3 : 1 between ortho-NH₂ and para-NH₂. However, for transitions with resolved ¹H hyperfine splitting no non-trivial spin-statistics have to be considered. The N_KaKc = 1₀₁; n, F + 1/2 = 12, 1 (or J, F₁ = 1.5, 0.5) is the lowest para state. It is 21.1102 cm^–1 above ground. Nov. 2010: corrected separate para and ortho predictions are available along with separate para and ortho partition function values. NOTE: The quantum number format is different from that of the main entry; redundant quantum numbers (e.g. I) have been omitted !
Predictions of the NH₂ pure rotational spectrum without hyperfine splitting are also available in units of MHz along with partition function values or in units of cm^–1.