Nitrosylazide is a highly unstable nitrogen oxide, chemical formula N4O, which can be synthesized via the following reaction at low temperatures:
NaN3 (in excess) + NOCl → NaCl + N4O

Below –50 °C, nitrosylazide exists as a pale yellow solid. Above this temperature, it decomposes into nitrous oxide
Nitrous oxide
Nitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula . It is an oxide of nitrogen. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...

 and elemental nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

N4O → N2O + N2
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