Abstract—The IR absorption spectra of solutions of mixtures of halothane (C₂HBrClF₃) and trimethylamine ((CD₃)₃N) in liquefied krypton were obtained and analyzed. Bands assigned to weak hydrogen-bonded complexes have been identified. In a series of temperature experiments on the change in the integral intensities of the bands of monomers and complexes, the enthalpy of formation of complexes was estimated. An extremely strong increase in the intensity of the second-order bands attributed to the first overtone of bending CH vibrations of halothane was found. The effect is determined by strong anharmonic interactions of a resonant nature (Fermi resonance and Darling–Dennison resonance). The results of ab initio calculations reproduce the experimentally observed effects.