An X-Y Coriolis perturbation in ν4 of CD3Br

The region 2242–2273 cm^?1 of the ν₄ band in CD₃Br was remeasured at a resolution limit of 0.025 cm^?1. Line assignments were extended up to J = 50 in some subbands. Transitions in the KΔK = ?8 subband were assigned, and the perturbation apparent in this region was attributed to the x-y Coriolis interaction with ν₃ + ν₅^±1 + ν₆^±1. The x-y Coriolis coupling parameter W_xu and the ν₃ + ν₅^±1 + ν₆^±1 band center (in cm^?1) are 0.01960 and 2339.17 for CD₃⁷⁹Br, while the corresponding values for CD₃⁸¹Br are 0.01956 and 2337.95.