Articles you may be interested inComment on ''Infrared spectrum and theoretical study of the dinitrogen pentoxide molecule (N2O5) in solid argon'' [Sulfur dioxide ͑OSO͒ isolated in solid argon at 13 K was irradiated with light at 193 nm from an ArF excimer laser. Weak absorption lines at 1006.1, 1004.7, and 739.9 cm Ϫ1 observed after photolysis are assigned to sulfur superoxide ͑SOO͒; the doublet near ϳ1005 cm Ϫ1 is due to matrix site splitting. The assignments are based on results from 18 O-isotopic experiments. Calculations using the B-P86 and the B3-LYP density-functional methods were made for three isomers of OSO; energies, structures, vibrational wave numbers, and infrared intensities were predicted for each species. Although observed line positions are nearly identical to those predicted with theory for cyclic-SO 2 , experimental relative IR intensities and 18 O-isotopic shifts agree with those predicted for SOO. The mechanism of formation of SOO in a matrix cage is discussed.