Infrared Spectrum of Solid Ammonium Azide : A Vibrational Assignment

Infrared spectra of solid ammonium azide at 68°K are presented. The solid, prepared by sublimation onto a cold salt window, seems to be a disordered crystal which becomes ordered on warming above 150°K. The annealed crystal displays spectral features with spacings of 10—20 cm—1 which can be attributed to crystal site perturbations. A band at 1830 cm—1 appears which is assigned as a combination involving a lattice torsional motion of the ammonium ion (420±20 cm—1). A vibrational assignment of solid ammonium azide is made. The vapor over ammonium azide at room temperature contains predominantly hydrazoic acid and ammonia.