Rotational spectra, structure, and internal dynamics of Ar–H2S isotopomers

Several groups have studied the rotational spectra of various isotopomers of the pseudolinear Ar–H2S dimer. We have found two additional K=0 progressions, for Ar–H2 32S and Ar–H2 34S, which show that the symmetrical isotopomers (with H2S or D2S) exist in lower and upper states giving progressions with B differing by about 50 MHz. When assigned and analyzed on this basis, the overall spectra are quite similar to those of the Ar–H2O analogue where the doubling is caused by 000 and 101 internal rotor states of the H2O or D2O. Such states of the H2S most likely cause the doubling found in the Ar–H2S isotopomers. However, some of the details differ in interesting ways, indicating substantial differences in their potential energy surfaces. The lower states of Ar–D2 32S and D2 34S have B’s about 28 MHz larger than those for H2S, while the isotopomers of the upper states exhibit a more normal decrease of about 12 MHz. Somewhat related to this is the effect of deuteration on the difference in B between lower an...