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The observed transitions were taken from
(1) M. Elkeurti, L. H. Coudert, J. Orphal, G. Wlodarczak,
C. E. Fellows, S. Toumi,
2008, J. Mol. Spectrosc. 251, 90.
15NH2D tunnels between two equivalent
positionsas does the main species NH3.
The strong c-type transitions occur between the
tunneling substates whereas a-type transitions
occur within the states.
The antisymmetric, J = 0 state, in the catalog
with the state number 1, is higher than
the symmetric, J = 0 state by
0.3832 cm–1 or 11487.4 MHz.
The rotational constants are average values.
In addition, one has to distinguish between ortho and
para levels with a spin-statistical weight ratio of
3 : 1.
In the symmetric substate, the ortho and para
levels are described by Ka odd and even,
respectively, while it is reversed for the antisymmetric
substate. The 111 level is the lowest ortho
and para level within the symmetric and
antisymmetric substate, respectively. It is 14.3388 and
14.7197 cm–1 above the symmetric
J = 0 level, respectively.
Note, however:
The ortho/para energy difference is only
0.3832 cm–1 because of the different
symmetries of v = 0 and 1 !
Transition frequencies obtained by FT-FIR spectroscopy have
not been merged. They ensure, however, that predictions
with calculated uncertainties below 2 MHz should be
reliable.
The dipole moment was assumed to agree with that of
14NH2D; see e018501.cat. This assumption
is probably correct within the reported uncertainties.
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