Fig. 3.

X-ray powder diffraction patterns. a Diffraction patterns measured using CuKα radiation for NaN₃ powder before (diffraction pattern at the bottom) plasma reaction and after (diffraction pattern on top) plasma reaction. The lines indicated by < cg > at 37, 66 and 77 2θ degrees correspond closely to the (110), (211) and (220) reflections of the cubic gauche structure of polymeric nitrogen reported by Eremets and co-workers^{4, 5}. The strong lines correspond to unreacted, pristine NaN₃, and the lines indicated by asterisks can be from phase I discussed in the text or a sodium nitride phase. b The X-ray diffraction pattern converted to the X-ray beam wavelength of 0.41686 Å used by Eremets and coworkers^{4, 5}. The (110), (211) and (220) reflections of the cubic gauche structure emerge clearly in the plasma-reacted sample (top) and are completely absent in the pristine NaN₃ sample (bottom)