Vibrational spectrum of perfluoroethane

Abstract

We have obtained IR absorption spectra of a C2F6 gas and a C2F6 cryosolution in Xe (T = 163 K) in the fundamental and overtone ranges. We have interpreted 28 bands of 12C12CF6 and three bands of 13C12CF6. In the spectral ranges that correspond to vibrations that are combinations with ν1, ν7, and ν5, we observe multiplets, which we attribute to interactions of the type of Fermi resonances between the states ν1(A1g) ∼ ν6(A1g), ν7(Eg) ∼ ν6 + ν11(Eg) ∼ 2ν8(Eg), ν5(A2u) ∼ ν8 + ν 11(A2u). We reveal an anomalous intensity distribution in the spectrum of an asymmetric isotopologue. For the basic and isotopic configurations of perfluoroethane, we calculate the coefficients of shapes of vibrations and the intensities of absorption bands. We reveal that the behavior of the groups 12CF3 and 13CF3 is indifferent to the excitation of doubly degenerate stretching vibrations ν7(Eg) and ν10(Eu).