Fermi resonances in the vibrational spectrum of perfluoroethane

Abstract

In this paper the Raman spectrum of liquid C2F6 in the spectral region 250–1500 cm−1 is presented. Data on six fundamental Raman bands of C2F6 are obtained. Doublets are observed in the spectral regions of the ν1 (A1g) (1416.3 cm−1, 1425.0 cm−1) and ν7 (Eg) (1221.9 cm−1, 1239.7 cm−1) fundamental bands. The structure of these bands is explained in terms of the Fermi resonances of ν7 ∼ (2ν8) ∼ (ν6 + ν11) (Eg) and ν1 ∼ (2ν6) (A1g) states. The values of the cubic potential energy constant K166 = 7.7 (2) cm−1 and the effective matrix element of a threefold interaction Weff = 8.5 (5) cm−1 were derived from the simultaneous processing of the doublet parameters in the Raman spectrum of liquid C2F6 and in the IR spectrum of C2F6 in liquid N2.