title: Isotope effect in hydrogen peroxide formation during H2O and D2O sonication.
abstract: The kinetics of hydrogen peroxide formation have been studied during H2O and D2O sonication in the presence of argon and oxygen (f = 22 kHz, I = 3.0 W cm-2, Pac = 0.52 W ml-1, V = 20 ml, T = 20 degrees C). It was found that the sonochemical reaction rate W has a zero order with respect to hydrogen peroxide (H2O, D2O or DHO2) concentration. In argon atmosphere the kinetic isotope effect was found to be equal to alpha = WH2O/WD2O = 2.2 +/- 0.3. The alpha value decreases in H2O-D2O mixtures with increasing H2O concentration. In oxygen atmosphere the isotope effect is not observed (alpha = 1.05 +/- 0.10). It is assumed that the revealed isotope effect is related to the mechanism of water sonolysis including the H2O-Ar* and D2O-Ar* energy transition, where Ar* is an argon atom in an excited state, in nonequilibrium plasma generated by the shock-wave.
authors.affiliation: Institute of Physical Chemistry, Russian Academy of Sciences, Moscow, Russia. nikitenko@ipc.rssi.ru
authors.forename: S I
authors.initials: SI
authors.lastname: Nikitenko