Conversion of SO2 to SO3 by in situ photolysis of SO2 and O-3 mixtures isolated in argon matrixes: Isotopic effects

The mechanism of photooxidation of sulfur dioxide in the presence of ozone and under irradiation at 266 nm has been investigated at low temperature in an argon matrix. Formation of stable SO3 occurs from the reaction between SO2 and O(D-1) and also by oxygen atom transfer within the SO2:O-3 complex. Use of isotopic SO2 species led to unusual observations suggesting that ph otooxidation of SO2 proceeds via an intermediate species, namely, OSOO; thi s trioxide sulfur isomer transforms into SO3 by tunneling. In the gas phase , the quenching of the O(D-1) atom by SO2 could occur through this intermed iate.