FAR-INFRARED SPECTRUM OF THE TURSIONAL BAND OF HYDRAZINE

Abstract

We report here the results of a study of the far-infrared spectrum of hydrazine obtained on the NBS BOMEM DA3.002 Fourier transform spectrometer. The spectrum was recorded in the wavenumber region 200 to $500 cm^{-1}$ with apodized resolution of $0.011 cm^{-1}$. This molecule has two large amplitude motions, a wag and the torsion. The spectrum is complicated because of splittings arising from these motions as well as overlapping with a ``hot band” especially below the band origin at $376 cm^{-1}$. The assignments were made using polynomial fittings of individual subbands. The B+A, A+B, and E+E transitions were assigned for each subband. The assigned transitions were analyzed through a global fitting procedure with the use of the model Hamiltion of $Hougen^{1}$ to obtain molecular parameters in the torsionally excited state. The large-amplitude splitting constants show large changes upon torsional excitation; e. g. the torsional-splitting constant $h_{3v}$ is -892(3) MHz compared to -2.90(2) MHz in the ground $state,^{2}$ and the inversion splitting constant $h_{5v}$ is +1931(2) MHz compared to -4010.23(4) MHz in the ground $state^{2}$ taking the sign conventions of Refs. 1 and 2.