QUENCHING OF POSITRONIUM ATOMS BY NITROBENZENE IN VARIOUS SOLUTIONS

A systematic study has been carried out on the quenching of positronium (Ps) atoms by nitrobenzene in various solvents. In order to see the effect of the energy level of Ps, in the localized bubble state, on the quenching capability of nitrobenzene, overall second-order rate constants were plotted against solvent surface tensions. It was found that the rate constant increased with increasing surface tension up to a critical value of ca. 26 dyn cm-1, corresponding to a Ps bubble energy of 1.24 eV. In liquids where the Ps energy is higher than this, the rate constant decreased with increase in solvent viscosity, as is expected for a diffusion-controlled reaction.