Ftir cryospectroscopic study of Fermi resonance polyades $\nu_{s}\approx$ 2$\nu_{b}$ in CHF$_{3}$

The sequences of Fermi resonances $\nu_{s}\approx$ 2$\nu_{b}$ in the IR spectrum of a fluoroform solution (CHF$_3$) in liquefied krypton have been studied. Here, $\nu_{s}$ is the CH-stretching vibration and $\nu_{b}$ is the bending vibration. It has been shown that it is necessary to use an extended set of spectroscopic parameters for the correct description of resonant multiplets at a high degree of vibrational excitation. Among other factors, it is necessary to consider the dependence of the anharmonic interaction constant $\alpha_{sbb}$ on the vibrational quantum numbers. The conclusions are generalized for the arbitrary case of the CH-chromophore CHX$_3$.