The experimental data was summarized in
(1) T. Amano, K. Hashimoto, and T. Hirao,
2006, J. Mol. Struct. 795, 190.
Assuming the submillimeter lines to be accurate to
100 kHz, essentially all experimental lines could be
reproduced satisfactorily. In contrast to (1), where a
fairly large number of transitions were omitted from the fit,
here only two lines were not included in the final fit.
Effects of the sextic centrifugal distortion constants
H were estimated from comparison with CH_{3}CN.
These parameters will have sizeable effects for transitions
with even higher quantum numbers. Therefore, it is
difficult to estimate how far the predictions are
reliable, possibly up to 800 GHz or slightly higher,
at least for low values of K.
Note: The
^{14}N hyperfine structure may be resolvable
in cold astronomical sources. No laboratory data are
known at present. Hyperfine structure has not been
considered in the calculation of the partition function.
At low temperatures, it may be necessary to discern between
A and E states of the molecule.
The A state levels are described by K = 3n,
those of E state by K = 3n ± 1.
The nuclear spinweight ratio is 2 : 1 for ACH_{3}CNH^{+}
with K > 0 and all other states, respectively.
The J_{K} = 1_{1} level
is the lowest E state level. It is 5.5398 cm^{–1} above ground.
The dipole moment is from an ab initio calculation
by
(2) P. Botschwina,
2000, J. Mol. Spectrosc. 203, 203.
