On the isotopic effects on the inhibition of o-Ps formation in normal and deuterated water

The isotopic effect on the o-Ps annihilation process was investigated in water and methanol. It was found that the hydrogen composition of the solvent influences both the intensity and the mean life of the component of the time spectrum attributed to the o-Ps atom and the inhibition constant of a given solute for Ps formation. In particular it was confirmed that the intensity of the o-Ps component is less in deuterated than in compounds of normal hydrogen composition and it was found that the inhibition constant for nitrate is bigger in heavy water than in normal water. These results can be easily explained in terms of a hot o-Ps reaction model advanced previously for explaining the inhibition of Ps formation, so that, conversely, they can be used in order to support this model. (author)