Knowledge Bank

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 $500cm-1$ with apodized resolution of $0.011cm-1$. 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 $376cm-1$. 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 $Hougen1$ 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 $h3v$ is -892(3) MHz compared to -2.90(2) MHz in the ground $state,2$ and the inversion splitting constant $h5v$ is +1931(2) MHz compared to -4010.23(4) MHz in the ground $state2$ taking the sign conventions of Refs. 1 and 2.