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It appears as if the NH2 group exerts
an inversion motion which leads to a splitting
of the ground vibrational state into 0+
and 0– substates, the latter
being about 1.7 THz higher in energy, as
determined from relative intensity measurements
in
(1) A. Bauder and T.-K. Ha,
1983, Chem. Phys. Lett. 97, 135.
The millimeter wave transition frequencies were
taken from
(2) K. Luková, L. Kolesniková, J.-C. Guillemin,
T. Uhlíková, J. Koucký, F. Horák,
Lukáš Hrubčík, K. Vávra, P. Kania,
Š. Urban, A. Belloche, I. Jiménez-Serra, and
V. M. Rivilla,
2025, Astrophys. J. 103, 9940.
The calculation should be accurate enough for radio
astronomical searches. Transitions with calculated
uncertainties of 0.1 MHz or larger should be viewed
with caution. 14N hyperfine structure splitting
may occur in transitions with low values of J
and potentially some others.
The partition function refers to the ground vibrational state
consisting of 0+ and 0–.
Some information on low-lying vibrational states is available in (2).
The dipole moment components within 0+ was determined in (1).
It was assumed that the values apply well enough for 0–.
A c-dipole moment between 0+ and 0–
was calculated in (2), but reliable calculations are not possible yet.
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