The vibrational spectra and normal coordinates analysis of bromofluoromethane, CH2BrF

The infrared gas-phase spectra of bromofluoromethane (CH2BrF) have been studied in the region below 6200 cm21 under conditions of medium resolution. All the fundamentals and many overtones, combination and hot bands have been assigned leading to an almost complete set of anharmonicity constants. Rotational analyses have been performed on the observed Qbranch features of over 10 bands. Enriched 79Br and 81Br samples were also employed to confirm vibrational assignment and supply further data. Analyses of Fermi resonance are made. The molecular structure was calculated ab initio at the Hartree– Fock (HF), the second-order Møller–Plesset (MP2) and the density functional theory (DFT) level with the 6-31111G(3df, 2pd) basis set. The ab initio force constants obtained from the vibrational analysis at B3LYP/6-31111G(3df, 2pd) level of theory were employed to fit the experimental data and an optimal harmonic force field was obtained for the CH2BrF molecule.