Perturbations study of the high-resolution spectrum of methyl bromide in the range of the fundamental band

Abstract The Fourier transform absorption spectrum of CH 3 Br has been analyzed between 2930 and 3010 cm −1 with a recorded resolution of 0.007 cm −1 . More than 1300 lines have been assigned for each isotopic species. Two bands have been identified: the fundamental parallel band ν 1 and the parallel component of ν 3 + ν 5 + ν 6 . An anharmonic resonance couples the corresponding levels and affects all the K subbands of these bands. Taking account of this resonance and of a vibrational l -type resonance in ν 3 + ν 5 + ν 6 , molecular parameters of these two bands have been determined for the first time. The band centers are (in cm −1 ) v 1 : 2973.184 ( CH 3 79 Br ), 2973.183 ( CH 3 81 Br ) ; v 3 + v 5 + v 8 : 2996.0.094 ( CH 3 79 Br ), 2994.864 ( CH 3 81 Br ) .