Ab initio characterization of several states of nitroxylium (NO). Comparison of fragmentation energies of nitroxylium, nitroxyl (NO₃), and nitrate

Ab initio calculations have been performed at the self‐consistent field (HF) level, and its perturbative extensions up to fourth‐order (MPn), for several electronic states of nitroxylium (NO ) as well as for a large number of reference species. Geometries are optimized at the HF/DZ and HF/DZP levels (double zeta and double zeta plus polarization bases). The ground state is found to be the D 3 h 1 A 1 ′ state, with the C 2 v 1 A 1 (closed Y ) state higher by 0.94 eV. The relationship between adding electrons or oxygen atoms to NO + and NO is explored, especially in relation to fragmentation energies of NO ( q = 0 or 1). A comparison is drawn between NO and two isoelectronic species, CO 3 and C(CH 2 ) 3 , where no surprises are found.