Infrared Spectrum and Vibrational Potential Function of Hydrazoic Acid

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.