Knowledge Bank

The microwave spectrum of hydrazine in the 18,000 to 35,000 Mc region has been examined and frequency measurements have been made on about 60 lines. Of these lines, 30 are strong and appear in 8 groups. The remaining lines are weak and are scattered throughout the spectrum. From a consideration of the interaction of the paired electrons of the nitrogen atoms, Sutherland and $Penney1$ have concluded that the configuration of minimum potential energy is that in which the planes bisecting the $NH2$ groups are at right angles. On this basis the hydrazine molecule is a slightly asymmetric rotor, and it is difficult to account for the appearance of such a large number of lines as pure rotational transitions. However, the interchange of the hydrogen atoms on each nitrogen atom and relative rotation of the $NH2$ groups leads to eight identical potential minima. Tunneling between these potential minima will produce a splitting of the eight-fold degeneracy. The magnitude of this splitting will vary with the rotational energy level and a large number of lines are possible.