Direct l-type doubling transitions in the ν6 = 1 vibrational state of CF3Br and CF3I: l-type resonance effects on the spin-rotation coupling

Direct l-type doubling transitions in the ν6 = 1 state of CF379Br, CF381Br and CF3I have been observed using the technique of Fourier transform microwave spectroscopy in the range 4.5–8 GHz. The transitions covered a range of J values from 38–47 for both isotopomers of CF3Br and from 40–51 for CF3I. The transition frequencies including hyperfine structures could solely be explained by the (Δk = ±2, Δl = ±2) l-type resonance interaction including rotation-vibration, quadrupole and spin-rotation terms.