Ozone is formed in good yield by reacting O-2(+) salts with water in HF at -78 degrees C. With isotopically labeled water O-17-O-16-O-16 and O-18-O-16-O-16 can be prepared, and other isotopomers could be made by starting with O-17(2)+ and O-18(2)+ precursors. O-17 NMR spectroscopy and IR matrix spectroscopy are used for detection and decay of the isotopomers. The O-17 or O-18 label at the terminal position remains at -78 degrees C, but at higher temperatures scrambling of the atoms is observed. Under strict monomolecular conditions no scrambling is observed till 450 degrees C, however. Irradiation of ozone in a 15K argon matrix with lambda = 254 nm affords scrambling of the label and formation of oxygen. Irradiation with lambda > 420 nm initiates only scrambling with little decay. The possible mechanisms of the atomic scrambling are discussed.