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Ethanethiol, aka ethyl mercaptan, occurs in two distinguishable
conformers because of the orientation of the SH group.
The internal rotation of the CH3 group can be
neglected in most instances. The doubly degenerate gauche
conformer is lowest in energy, the anti conformer is
higher in energy by about 160 K. This is an average value
of several reported ones. Tunneling between the two equivalent
gauche conformers lifts the degeneracy, causing a
gauche+ and a gauche–
state which interact heavily.
The spectroscopic parameters were published by
(1) H. S. P. Müller, A. Belloche, L.-H. Xu, R. M. Lees,
R. T. Garrod, A. Walters, J. van Wijngaarden, F. Lewen,
S. Schlemmer, and K. M. Menten,
2016, Astron. Astrophys. 587, Art. No. A92.
The transition frequencies are from
(2) L. Kolesniková, B. Tercero, J. Cernicharo,
J. L. Alonso, A. M. Daly, B. P. Gordon, and S. T. Shipman,
2014, Astrophys. J. 784, Art. No. L7.
Predictions should be sufficiently accurate for all
observational purposes. Transition frequencies with
uncertainties larger than 500 kHz should be viewed
with caution. Uncertainties concerning the signs of
the main interaction parameters with respect to those of
the dipole moment components appears to have only minute
effects on the intensities.
The partition function does not takes into account the
anti conformer !
The dipole moment was assumed to agree with that of the
main species, see e062523.cat.
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