Reactions of nitric oxide with sulfur species. Infrared spectra and density functional theory calculations for SNO, SNO⁺, SSNO, and SNNO in solid argon

Nitrogen oxide sulfide species were produced by codeposition of argon/nitric oxide with sulfur species from an argon/sulfur vapor microwave discharge or by deposition of an argon/nitrogen/oxygen/sulfur vapor discharge mixture on a 12 K CsI window. These two new synthetic routes confirmed the identification of the SNO radical and produced the linear SNO⁺ cation and the higher sulfur-containing nitric oxide complex species SSNO at 1772.5 and 670.9 cm^-1. Codeposition of nitric oxide with an argon/nitrogen/sulfur vapor discharge produced a new band at 1815.2 cm^-1, which is assigned to the N-O stretching vibration in the mixed dimer ONNS species. Reaction of superheated sulfur vapor with argon/nitric oxide gave only the 1772.5 and 670.9 cm^-1 bands for SSNO with no SNO. In contrast codeposition of Ar/O₂ and Ar/NO produced a trace of NO₂, but the analogous dioxygen-nitric oxide complex was not observed. Density functional theory was used to calculate structures and frequencies for these product species.