Reactions of silicon atoms with NO molecules in solid argon have been studied using matrix isolation infrared absorption spectroscopy. The reaction products were identified via isotopic substitutions ((NO)-N-15-O-16, (NO)-N-14-O-18, and mixtures) and comparison with density functional calculations of isotopic frequencies. Three different SiNO isomers: SiNO, NSiO, and Si-eta(2)-NO were identified. The Si(NO)(2) and SiNSiO molecules also were formed on annealing. The SiNO, Si(NO)(2), and NSiO molecules decomposed to form the SiO and SiO2 oxides and the NNSiO2 van der Waals complex upon broad band irradiation.