Infrared Spectrum and Vibrational Potential Function of Hydrazoic Acid

Abstract

Gas‐phase and N₂ matrix vibrational spectra of HN₃, DN₃, H¹⁵NNN, ¹⁵NNNH, D¹⁵NNN, and ¹⁵NNND are reported. The pure rotation spectrum of HN₃ is given as well. Strong vibration—rotation interaction is evident in the v₅, v₆ spectra, in the changes of the A rotational constant by 4%−8% in the hydrogen stretching and bending fundamentals, and in the pure rotation spectrum of HN₃. Normal coordinates and eight force constants are determined using 22 vibrational frequencies from six molecules. A large (HNN bend)—(HN–N stretch) interaction force constant is found. Its magnitude and sign are readily understood in terms of the electronic structure of hydrazoic acid.