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Data of several vibrational states and isotopologs were
fit together. Ground state rotational transition frequencies
of the main isotopic species were reported by
(1) T. Törring and R. Herrmann,
1989, Mol. Phys. 68, 1379;
and by
(2) C. Yamada, E. A. Cohen, M. Fujitake, and E. Hirota,
1990, J. Chem. Phys. 92, 2146.
Data within the first two excited vibrational states
were taken from
(3) M. Goto, S. Takano, S. Yamamoto, H. Ito, and S. Saito,
1994, Chem. Phys. Lett. 227, 287.
Ground state data of the 18O isotopolog were
taken from
(4) A. A. Breier, B. Waßmuth, T. Büchling,
G. W. Fuchs, J. Gauss, and T. F. Giesen,
2018, J. Mol. Spectrosc. 350, 43.
A small number of lines with large residuals were omitted.
The spectroscopic parameters differ somewhat from earlier
published values, including the combined fit in (4).
The calculated transitions should be accurate enough for
all observational purposes. Some caution may be advised,
though, in particular above 720 GHz or for HFS components
with calculated uncertainties larger than 0.5 MHz.
27Al hyperfine splitting may be resolvable,
in particular at low J. Therefore, a
separate hyperfine calculation is provided for
frequencies below 500 GHz. Please note that a sequential
coupling scheme was employed.
The first 30 vibrational states were included in the
calculation of partition function values. The spin
multiplicity of 6 for 27Al was considered
in the entry without HFS splitting.
The ground state dipole moment from a quantum-chemical calculation
for the main isotopolog was reported by
(5) A. T. Patrascu, S. N. Yurchenko, and J. Tennyson,
2015, Mon. Not. R. Astron. Soc. 449, 3613.
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