The observed transitions were published in
(1) M. Elkeurti, L. H. Coudert, J. Orphal, G. Wlodarczak,
C. E. Fellows, S. Toumi,
2008, J. Mol. Spectrosc. 251, 90.
The spectroscopic parameters of NHD_{2} were
used as starting values in the present fits. Based on the fit results
it was concluded that some weak transitions from (1) may have been
assigned incorrectly. The resulting parameters are consequently
different from those in (1). Nevertheless, predictions for low
energy transitions are beyond any doubt. Moreover, predictions
with calculated uncertainties below 1 MHz should be reliable
because of the extensive farinfrared data which have not been
merged.
The misassignments have recently been confirmed
in
(2) M. Elkeurti, L. H. Coudert, J. Orphal, G. Wlodarczak,
C. E. Fellows, S. Toumi,
2010, J. Mol. Spectrosc. 260, 139.
^{15}NHD_{2} tunnels between two equivalent
positionsas does the main species NH_{3}.
The strong ctype transitions occur between the
tunneling substates whereas btype 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
0.1583 cm^{–1} or 4746.5 MHz.
The rotational constants are average values.
In addition, one has to distinguish between ortho and
para levels with a spinstatistical weight ratio of
2 : 1.
In the symmetric substate, the ortho and para
levels are described by K_{a} + K_{c}
even and odd, respectively, while it is reversed for the
antisymmetric substate.
The 1_{01} level is the lowest para
and ortho level within the symmetric and
antisymmetric substate, respectively. It is 9.0813 and
9.2395 cm^{–1} above the symmetric
J = 0 level, respectively.
Note, however:
The ortho/para energy difference is only
0.1583 cm^{–1} because of the different
symmetries of v = 0 and 1 !
The dipole moment was assumed to agree with that of
^{14}NHD_{2}; see e019501.cat.
