Infrared spectrum and anharmonic force field of CH2DBr

The gas-phase infrared spectrum of monodeuteromethyl bromide, CH2DBr, has been examined at medium resolution in the range 400-10000 cm-1, leading to the identification of 70 vibrational transitions. The assignment of the absorptions in terms of fundamentals, overtones, combinations, and hot bands, assisted by quantum chemical calculations, is consistent all over the region investigated. The 79/81Br isotopic splitting for the lowest fundamental ν6 and the value for the v8 ) 1 level have been now precisely determined. Anharmonic resonances are very marginal for all fundamentals and the Coriolis interaction effects are clearly evident in the ν4/ν8 band system, in the ν2 and ν7 fundamentals. Spectroscopic parameters, obtained from the analysis of partially resolved rotational structure, have been derived in the symmetric tops limit approximation. Highquality ab initio calculations have been performed, and harmonic and anharmonic force fields have been predicted from coupled cluster CCSD(T) calculations employing the cc-pVTZ basis set. A good agreement between computed and experimental data, also including the C-H stretching overtones at 6000 and 9000 cm-1, has been obtained.