S atoms have been generated through vacuum ultraviolet photolysis of carbonyl sulfide (OCS) in Ar matrices. Excitation spectra measured by monitoring the S-1 --> D-1 emission of S at 784 nm. are assigned to Ar+S- <-- ArS charge-transfer (CT) (135 nm, substitutional site (SS) and 159 nm, interstitial site (IS)) and S-3 <-- P-3 Rydberg (160.8 nm) transitions. Empirically derived potential curves of Rg(+) S- and Rg(+)O(-) species predict the transition energies with reasonable accuracy. S atoms are found to be more photomobile than O atoms in Ar matrices.