Analysis of FTIR spectra of (CH2BrCl)-Br-79-Cl-35; the nu(3) and nu(9) fundamentals

The infrared spectrum of isotopically pure (CH2BrCl)-Br-79 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 nu(3) and nu(9) fundamentals of the most abundant species (CH2BrCl)-Br-79-Cl-35. Improved ground state constants, LIP to quartic terms, have been obtained from ground state combination differences (GSCD) involving transitions of the fundamentals nu(3), nu(4), nu(5) and nu(9). Both nu(3) and nu(9) transitions were fitted to a Watson-type Hamiltonian in the S-reduction, yielding accurate molecular constants for the nu(3) and nu(9) excited states. Small local perturbations were observed ill both bands. Prominent features in the spectra were assigned to the nu(3) and nu(9) fundamentals of the (CH2BrCl)-Br-79-Cl-37 isotopic species and the hot-bands nu(3)+nu(6)-nu(6) and nu(9)+nu(6)-nu(6) of (CH2BrCl)-Br-79-Cl-35.