[3] This increased interest in polynitrogen compounds in the late twentieth century was due to the advance of computational chemistry which predicted that these types of molecules could be used as potential high-energy-density matter (HEDM) sources.

[6] Theoretical chemistry predicted several possible synthesis mechanisms for N4 including reaction of a neutral N atom with a N•3 radical, binding of two N2 molecules in the excited state, and extrusion from polycyclic compounds, none of which could be accomplished experimentally.

[7] A deflecting electrode was used to remove any unreacted N+4 ions as well as the target gas, CH4, and any additional unintended reaction products, leaving a stream of N4 molecules.

[7] Ab initio calculations in the neutral molecular suggest that previously proposed rectangular or tetrahedral structures, analogous to cyclobutadiene and tetrahedrane, respectively, are not likely to be the most thermodynamically stable.

[8] The structure of N+4 has been predicted by theoretical experiments and confirmed by experimental techniques involving collisionally activated dissociation mass spectrometry (CADMS).

Based on the fragments observed, a structure was determined invlvolving two pairs of triple-bonded nitrogen atoms (two N2 units) that are associated with each other with a longer, weaker bond.