Tetranitrogen (N ₄ ), which has been the subject of great theoretical interest, has been prepared from the N ₄ ⁺ cation and positively detected as a gaseous metastable molecule with a lifetime exceeding 1 microsecond in experiments based on neutralization-reionization mass spectrometry. An examination of the geometry of N ₄ ⁺ and the fragmentation pattern of the ¹⁴ N ₂ ¹⁵ N ₂ neutral molecule has revealed that the latter is characterized by an open-chain geometry with two distinct, closely bound N ₂ units joined by a longer weaker bond.

Hydrogen trioxide (HO ₃ ) has long been postulated as a key intermediate in important atmospheric processes but has proved difficult to detect. The molecule was unequivocally detected in experiments based on neutralization-reionization and neutralization-reionization/collisionally activated dissociation mass spectrometry, using protonated ozone (HO ₃ ⁺ ) as the charged precursor. Hydrogen trioxide is a relatively stable species and has a H-O-O-O connectivity and a lifetime exceeding 10 ^–6 seconds at ambient temperature.