Millimetre-wave and Fourier transform infrared spectra between 325 cm-1 and 4720 cm-1 of BrCN and global rovibrational analysis of the main isotopomers

The infrared absorption spectrum of BrCN has been recorded in the region 325-4720 cm(-1) with a Bruker 120 HR interferometer. More than 30 000 lines have been measured and most of them have been assigned: 10 734 lines for 151 bands and 10 993 lines for 150 bands of (BrCN)-Br-79-C-12-N-14 and (BrCN)-Br-81-C-12-N-14, respectively. Also new millimetre-wave spectra were measured for the vibrational excited states lying between 1000 cm(-1) and 1400 cm(-1). After a band by band analysis of these transitions, rovibrational global analyses have been performed for both isotopomers using all available experimental data. The rotational l-type resonance and the anharmonic resonance associated with k(122) are taken into account in one-step diagonalization procedures. Sets of 73 molecular parameters are obtained for both isotopomers. It is shown that the existing equilibrium structure is likely to be reliable. The vibrational dependence of the quartic centrifugal distortion constant is analysed for the linear triatomic molecules studied so far.