Samples formed by codepositing S-2 from a superheater source with Ar/O-2 on a 10 K substrate exhibit very strong 1403.0-cm(-1), and weaker 725.5-cm(-1) infrared absorptions. Photolysis decreases these bands slightly and produces SO2 and S2O. The infrared bands show O-18(2) and S-34(2) Shifts appropriate for O-O and S-S fundamental vibrations, and triplet absorptions in mixed isotopic experiments suggesting two equivalent O and two equivalent S atoms in the product complex. Similar results were obtained for Se-2 and O-2; new absorptions appeared at 1404.5 and 391 cm(-1). Ab initio calculations at the SCF, CISD, and CCSD levels of theory failed to find a complex with the observed spectroscopic properties. However, calculations with the BP density functional characterized a singlet (S-2)(O-2) parallelogram structure bound by 15.6 kJ/mol relative to triplet S-2 and O-2 With the O-O stretching frequency red-shifted 187 cm(-1) and the S-S fundamental blue-shifted 20 cm(-1). This weakly bound (S-2)(O-2) complex is chemically intermediate between the unstable O-4 and stable S-4 molecules. The argon matrix has made possible the formation of the weak (S-2)(O-2) complex and DFT with the BP functional has characterized this weak charge-transfer interaction.