Isotope effect in the formation of hydrogen peroxide by the sonolysis of light and heavy water

The kinetics of the formation of hydrogen peroxide by the sonolysis of ligh t and heavy water in argon and oxygen atmospheres was investigated. The son ochemical reaction has a zero order with respect to hydrogen peroxide (H2O2 , D2O2 or DHO2). The measurement of the kinetic isotope effect (alpha), def ined as the ratio of the reaction rates in H2O and D2O. carried out under a rgon gave a value of 2.2 +/- 0.3. The observed isotope effect decreases wit h an increase in the concentration of light water in H2O-D2O mixtures. No i sotope effect is displayed in the oxygen atmosphere (alpha = 1.05 +/- 0.10) . The isotope effect is determined presumably by the mechanism of sonochemi cal decomposition of water molecules, which includes the H2O-Ar* and D2O-Ar * energy exchange (where Ar* are argon atoms in the P-3(2.0) excited state) in the nonequilibrium plasma generated by a shock wave, arising upon a cav itation collapse.