Determination of mechanisms of the ν1(H–F) band shape formation in the absorption spectra of H-bonded complexes of HF from combined experimental studies and nonempirical calculations

The advantage of combining the spectroscopic experiments and nonempirical calculations in one study is discussed. Based on the results of earlier studies of H-bonded complexes H₂O⋯HF, dimethyl ether⋯HF, and acetone⋯HF and the study of HCN⋯HF performed in this paper, the requirements on the experimental conditions and theoretical approaches that can provide reliable spectroscopic data are generalized for the first time. Detailed recommendations on using the proposed theoretical method in multidimensional anharmonic calculations of other related AH⋯B complexes are also formulated. Comparative analysis of the data calculated for the four complexes shows for the first time that the intensity of shoulders of the ν₁(H–F) band (sum and difference transitions) is governed primarily by perturbations of the wave functions of low-frequency modes.