The anti-conformer of H₂NSH is lowest in energy. According to relative intensity measurements, the syn-conformer is roughly 87 cm^–1 or 125 K higher in energy. As this difference is very uncertain, the two conformers were treated as separate molecules.
The experimental millimeter wave lines are from
(1) F. J. Lovas, R. D. Suenram, and W. J. Stevens, 1983, J. Mol. Spectrosc. 100, 316.
The line list is rather limited. No ¹⁴N hyperfine structure splitting was resolved for this conformer. In the present fit, it was assumed that the frequency of the J = 3 – 2, K_a = 2 transitions refers to only the higher frequency transition. In addition, a 1 MHz typographical error was assumed for the J = 4 – 3, K_a = 3 transitions.
The calculation has been truncated at J = 10 and K_a = 3. Frequencies involving higher J and K_a should be viewed with caution.
The ¹⁴N hyperfine splitting may be resolved for lower J transitions. Therefore, a separate hyperfine calculation is provided assuming the HFS parameters of both conformers to be very similar, as suggested by unpublished quantum chemical calculations. The ¹⁴N spin multiplicity of 3 was considered in the calculation of the partition function !
The dipole moment components were determined experimentally for the perdeuterated isotopolog in (1). The a-component agrees well with quantum chemical calculations whereas the very uncertain b-component appears much larger as indicated below. However, b-type transition can not be calculated reliably at present because of the limited data set.