The Raman spectra of liquid N2F4at temperatures ranging from minus;80deg; to minus;150deg;C have been recorded. Depolarization values have been measured. The farhyphen;infrared spectrum of the vapor and solid has also been reinvestigated. Seventeen pronounced Raman lines have been observed whereas theC2isomer of tetrafluorohydrazine has only 12 fundamentals. The large number of Raman lines suggests the presence of more than one isomer at minus;120deg;C. A comparison of the infrared and Raman bands below 800 cmminus;thinsp;1shows the mutual exclusion principle is operative and it is concluded from this alternate forbiddeness that thetranshyphen;N2F4isomer ofC2hsymmetry gives rise to these mutually exclusive bands. Assignment of the observed frequencies based on depolarization values, band positions, and infrared band contours are presented for the molecule in both theC2andC2hconfigurations. It is shown that the data can only be interpreted in terms of an equilibrium mixture of the two isomers at both ambient and lower temperatures, and that these isomers differ little in energy.
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