New species cis- and trans-OSNO, designated c-OSNO and t-OSNO, respectively, are produced and identified with infrared absorption spectra when an argon or nitrogen matrix containing OCS and NO2 is irradiated with laser emission at 248 nm. Lines at 1156.1 and 1454.4 cm−1 are assigned to c-OSNO and those at 1178.0 and 1459.0 cm−1 are assigned to t-OSNO in solid N2. Lines at 1154.9 and 1450.8 cm−1 are assigned to c-OSNO and those at 1181.2 and 1456.0 cm−1 are assigned to t-OSNO in solid Ar; further lines associated with minor matrix sites are identified. Assignments of spectral lines are based on results of both experiments with N15- and O18-isotopic substitution and theoretical calculations using density-functional theories, B3LYP with an aug-cc-pVTZ basis set; these calculations predict the geometry, energy, vibrational frequencies, and infrared intensities of SNO2 as four isomers: C2v-SNO2, t-SONO, t-OSNO, and c-OSNO, in increasing order of stability. Mechanisms are proposed to rationalize that c-OSNO and t-OSNO, rather than t-SONO or C2v-SNO2, are produced from irradiated matrices containing OCS and NO2, and that no reaction product is observed in an Ar matrix containing CS2 and NO2 after irradiation at 193 nm.