Rovibrational Spectra of Water-Carbon Disulfide Complexes in the Bending Region of Water: Anomalous ortho-to-para Ratio.

Rovibrational spectra of D2O-CS2 and HDO-CS2 van der Waals complexes have been measured in the bending region of D2O/HDO by direct absorption in a slit supersonic jet expansion. The H2O-CS2 dimer is reinvestigated in the bending region of H2O with a higher rotational temperature compared with the previous study [Barclay, A. J. Phys. Chem. Chem. Phys. 2024, 26, 23053-23061], namely, ∼10 versus ∼2 K. Only the most stable isomer was observed, and precise molecular constants for these three complexes are determined. The HDO-CS2 complex in the supersonic jet was relaxed into an equilibrated population. But the line intensities for transitions originating from the Ka = 1 levels in the ground state for both D2O-CS2 and H2O-CS2 are found to be significantly stronger than those predicted with normal nuclear spin statistical weights. This abnormality is likely due to the different yielding rates for the para- and ortho- spin species of D2O-CS2 or H2O-CS2 in the supersonic jet expansion.