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The experimental data were taken from
(1) A. Janczyk and L. M. Ziurys,
2006, Astrophys. J. 639, L107.
The 27Al hyperfine split a-type
J = 1 – 0 transition
frequencies were also included in the fit. They were
reported by
(2) M. Fukushima and M. C. L. Gerry,
2010, J. Mol. Spectrosc. 262, 11.
Omitting a small number of transition with large
residuals from (1), these data fit to 20 kHz,
including the lines with Ka =
5 and 6. The parameter set differs only in one
additional parameter from the the combined set of
(1) and (2).
27Al HFS splitting may be resolvable at
low values of J and higher values of
Ka, but these transitions are
deemed to be too weak even if the molecule
will have been observed in space. The entry
may be sufficiently accurate for all observational
purposes. Transitions with predicted uncertainties
exceeding 0.2 MHz should be viewed with some caution.
The dipole moment was taken from an ab initio
calculation by
(3) H. S. P. Müller, 2018, unpublished.
Even though the molecule posseses a moderately large
b-dipole moment component, no such transitions
were calculated because their frequencies are too uncertain.
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