Analysis of FTIR spectra of CH279Br35Cl; the nu3 and nu9 fundamentals

The infrared spectrum of isotopically pure CH279BrCl has been recorded at a resolution of 0.0025 cm-1 and 0.0023 cm-1 (FWHM) in the range 600-1600 cm-1 with a Bruker IFS 120 HR Fourier transform spectrometer in Wuppertal. Here we report the full rotational analysis of the nu3 and nu9 fundamentals of the most abundant species CH279Br35Cl . Improved ground state constants, up to quartic terms, have been obtained from ground state combination differences (GSCD) involving transitions of the fundamentals nu3, nu4, nu5 and nu9. Both nu3 and nu9 transitions were fitted to a Watson-type Hamiltonian in the S-reduction, yielding accurate molecular constants for the nu3 and nu9 excited states. Small local perturbations were observed in both bands. Prominent features in the spectra were assigned to the nu3 and nu9 fundamentals of the CH279Br37Cl isotopic species and the hot-bands nu3+nu6 - nu6 and nu9+nu6 - nu6 of CH279Br35Cl.