Aluminum monohydride, 1Σ+
Species tag 028516
Date of EntryDec. 2009
ContributorH. S. P. Müller

The J = 1 – 0 transition frequencies were reported by
(1) D. T. Halfen and L. M. Ziurys, 2004, Astrophys. J. 607, L63
Also used in the fit were extensive infrared measurements from
(2) J. L. Deutsch, W. S. Neil, and D. A. Ramsay, 1987, J. Mol. Spectrosc. 125, 115
and from
(3) F. Ito, T. Nakanaga, H. Takeo, and H. Jones, 1994, J. Mol. Spectrosc. 164, 379
The predictions should be quite reliable throughout because of the extensive IR data used in the fit.
The 27Al hyperfine splitting has been resolved in the laboratory, but it probably does not matter for astronomical observations. Nevertheless, a separate prediction considering 27Al hyperfine splitting with J" ≤ 4 is available. Note: The partition function does not include the spin-multiplicities of 27Al ! Therefore, partition function values have to be multiplied by 6 when considering 27Al hyperfine splitting ! Vibrational contributions have been considered in the calculation of the partition function. Values for the ground state are given in parentheses.
Note: D. T. Halfen and L. M. Ziurys, 2014, Astrophys. J. 791, Ar. No. 65
report an overlap of the two strongest HFS components of the J = 2 – 1 around 755.200 GHz, about 10 MHz too low. Not only are the transition frequencies incompatible with the infrared data of AlH, the resulting distortion parameter D is incompatible with infrared data of AlD or with rotational data of AlD by Halfen and Ziurys even under consideration of the breakdown of the Born-Oppenheimer approximation.
The ground state dipole moment has been taken from an ab initio calculation by
(4) W. Meyer and P. Rosmus, 1975, J. Chem. Phys. 63, 2356
The predictions should be reliable up to about 1.0 THz.
Note: The dipole moment of aluminum monohydride shows very pronounced vibrational effects. Moreover, its calculated value depends very strongly on the degree of electron correlation. A different article by
(5) J. M. O. Matos, B. O. Roos, A. J. Sadlej, and G. H. F. Diercksen, 1988, Chem. Phys. 119, 71
quote as ground state value calculated at their highest level 0.300 D. Therefore, intensity predictions should be viewed with great care.

Lines Listed25
Frequency / GHz< 8786
Max. J25
log STR0-10.0
log STR1-10.0
Isotope Corr.-0.0
Egy / cm–10.0
 µa / D0.186
 µb / D 
 µc / D 
 A / MHz 
 B / MHz188890.4
 C / MHz 
 Q(500.0)56.3889 (55.8470)
 Q(300.0)33.5707 (33.5564)
 Q(225.0)25.2285 (25.2277)
 Q(150.0)16.9158 (16.9158)
 Q(75.00)8.6228 (8.6228)
 Q(37.50)4.4889 (4.4889)
 Q(18.75)2.4378 (2.4378)
 Q(9.375)1.4490 (1.4490)
detected in ISM/CSMno

Database maintained by Holger S. P. Müller and Sven Thorwirth, programming by D. Roth and F. Schloeder