Vibrational Spectrum of Perfluoroethane

摘要

We have obtained IR absorption spectra of a C_(2)F_(6) gas and a C_(2)F_(6) cryosolution in Xe (T velence 163 K) in the fundamental and overtone ranges. We have interpreted 28 bands of ~(12)C~(12)CF_(6) and three bands of ~(13)C~(12)CF_(6). In the spectral ranges that correspond to vibrations that are combinations with v_(1), v_(7), and v_(5), we observe multiplets, which we attribute to interactions of the type of Fermi resonances between the states v_(1)(A_(1g)) approx v_(6)(A_(1g)), v_(7)(E_(g)) approx v_(6) + v_(11)(E_(g)) approx 2v_(8)(E_(g)), v_(5)(A_(2u)) approx v_(8) + v_(11)(A_(2u)). 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 ~(12)CF_(3) and ~(13)CF_(3) is indifferent to the excitation of doubly degenerate stretching vibrations v_(7)(E_(g)) and v_(10)(E_(u)).