High-resolution infrared spectrum of the v₁ and v₃ bands of dichlorine monoxide, Cl₂O

The v₁ (symmetric stretch) and v₃ (asymmetric stretch) fundamental bands of the semistable molecule ClOCl have been recorded and analyzed. This is the first high-resolution infrared study of dichlorine monoxide. The spectrum, which occurs in the 600 to 700 cm^-1 region, is very dense, and its assignment was greatly aided by the results of previous microwave studies of the ground and excited vibrational states. About 5400 transitions belonging to the two most abundant isotopic forms, ³⁵Cl¹⁶O³⁵Cl and ³⁵Cl¹⁶O³⁷Cl, were assigned and fitted. For each isotope, the v₁ and v₃ bands were analyzed simultaneously in order to account for the Coriolis interaction which couples these vibrations. The band origins for the ³⁵Cl¹⁶O³⁵Cl isotope were determined to be v₁ = 641.9694(1) cm^-1 and v₃ = 686.5936(1) cm^-1. The Coriolis interaction parameter was determined to be G_c = 0.21087(2) cm^-1, which corresponds to ζ^C₁₃ = 0.928.