Amino wagging and inversion in hydrazines: RR branch of the antisymmetric wagging band of NH2NH2

Infrared absorption spectrum of undeuterated hydrazine in the gaseous state has been observed with a resolving power better than 0.06 cm^?1 in the 1024 ～ 961 cm^?1 region, where the ^RR- and ^RQ-branch lines of the antisymmetric wagging band (v_a = 1 ← 0) appear. It has been found that every line belonging to the ^RR branch as well as every ^RQ peak of the band splits into four components, a, b, c, and d. This is explained by considering that the v_a = 0 state splits into A_I, E, and B₂ substates and the v_a = 1 state into B₁, E, and A₂ substates, because of the four equivalent potential minima (D₄) of the hydrazine molecule which are reached by inversions of the two amino groups. From the observed wave numbers of the ^RR lines, effective values of the rotational constants of the B₁, E, and A₂ sublevels of the v_a = 1 state were obtained. On the basis of these values and the ones for the A₁, E, and B₂ sublevels of the ground vibrational state, obtained from a previous microwave study, a discussion of the antisymmetric wagging-inversion coordinate is given.