Infrared Spectrum of HN3 and DN3: Assignment of the Coriolis-Coupled Bending Vibrations

The complex infrared vibration—rotation spectra of hydrazoic acid and deuterohydrazoic acid from 400–1000 cm−1 have been studied. The prominent Q branches have been assigned to three Coriolis-coupled vibrational transitions. From an analysis of the observed frequencies, band origins and Coriolis constants have been determined. HN3: v3=1263.7, v5=534.2, v6=607.0, ζ36z=−0.31, ζ56z=−0.93±0.02; DN3: v4=953.8, v5=492.2, v6=588.4, ζ46z=−0.41, ζ56z=−0.82±0.02. Coriolis coupling between v5(a′) and v6(a″), combined with the inherently small intensity of v6, causes v6 as well as v5 to exhibit predominantly parallel character. The anomalous intensity distribution has been the cause of previous difficulty in assignment.