An isotopic independent fit was performed by
(1) H. S. P. Müller, 2021, unpublished.
The J = 1 – 0 transition frequencies of MgS, v = 0, 1, and of ²⁵MgS, ²⁶MgS, and Mg³⁴S were reported by
(2) K. A. Walker and M. C. L. Gerry, 1997, J. Mol. Spectrosc. 182, 178.
Additional millimeter and lower submillimeter data of MgS in v = 0 were published by
(3) S. Takano, S. Yamamoto, and S. Saito, 1989, Chem. Phys. Lett. 159, 563.
Information on the vibrational spacing was taken from
(4) M. Marcano and R. F. Barrow, 1970, Trans. Faraday Soc. 66, 2936.
Uncertainties in (3) were taken as 3σ and adjusted accordingly. Nuclear spin-rotation was considered for the ²⁵MgS data from (2). This hyperfine splitting, however, is very small and can be neglected for astronomical observations.
The transition frequencies should be viewed with some caution because of the limited data set.
The ground electronic state of MgS is probably perturbed by low-lying excited states, similar to MgO. This makes extrapolation to higher v even more questionable than under normal circumstances. This will also affect the partition function non-neglibly at temperatures of 500 or 1000 K and higher.
The dipole moment of the main isotopolog was taken from a quantum-chemical calculation in
(5) G. Chambaud, M. Guitou, and S. Hayashi, 2008, Chem. Phys. 352, 147.
Isotopic changes and possibly also rotational changes in the dipole moment can be neglected, vibrational changes possibly not.