Electronic structure of NSO(-) and SNO(-) anions: Stability, electron affinity, and spectroscopic properties

The low-energy electronic states of NSO anion and its SNO isomeric form for the singlet, triplet, and quintet spin multiplicities have been investigated by accurate ab initio approaches and large atomic basis sets. One-dimensional cuts of the three-dimensional potential energy surfaces (PESs) along selected interatomic distances and bending angles for these states have been calculated to assess the formation and stability of NSO(-) and SNO(-) in the gas phase. Results show that these anions have two low-energy states (X̃(1)A(') and 1(3)A″) that are bound and stable with respect to electron detachment. Owing to the energetic position of the dissociating asymptotes of the neutral and anionic species, several electronic excited states are suggested to be stable with respect to the electron autodetachment process in the long-range parts of the potentials before reaching the molecular region. The nature of the PESs in these regions and their implications and effects on the formation of SNO(-) from atomic and molecular fragments are discussed. This information is essential for a better understanding of the potential role of these species in diverse media.