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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 17O hyperfine parameters were derived from
a matrix ESR measurement by
(5) L. B. Knight and W. Weltner,
1971, J. Chem. Phys. 55, 5066;
and from quantum-chemical calculations by
(6) H. S. P. Müller, 2019, unpublished.
The calculated transitions should be accurate enough for
all observational purposes. Some caution may be advised
above 720 GHz or for HFS components with calculated
uncertainties larger than 0.5 MHz.
27Al and 17O 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 36 for 27Al and 17O
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
(7) A. T. Patrascu, S. N. Yurchenko, and J. Tennyson,
2015, Mon. Not. R. Astron. Soc. 449, 3613.
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