High-resolution rovibrational analysis of CH281BrF in the range 920–980 cm−1

The high-resolution infrared spectrum of CH281BrF has been studied in part of the atmospheric window between 920 and 980 cm−1, the region characterized by the v9 and v5 + v6 absorptions. The v9 emerges as a pseudo a-type band, with selection rule ΔKa = ΔKc = 0, ±2, and v5 + v6 exhibits a predominant a-type structure. The interactions connecting these levels and the dark 3v6 state have been explored. The anomalous v9 transitions have been ascribed to Coriolis interaction with v4. The analysis yields a set of accurate upper-state parameters for v9 and v5 + v6. Spectroscopic information on 3v6 has been also obtained.