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

Abstract

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, ζ₃₆^z=−0.31, ζ₅₆^z=−0.93±0.02; DN₃: v₄=953.8, v₅=492.2, v₆=588.4, ζ₄₆^z=−0.41, ζ₅₆^z=−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.