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

Abstract

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 K_a = 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.