EFFECT OF EXTERNAL-PRESSURE ON THE REACTIVITY OF NITROBENZENE TOWARD POSITRONIUM IN HEXANE AND BENZENE SOLUTIONS

Reaction rate constants of positronium (Ps) with nitrobenzene have been determined in hexane and benzene solutions as a function of external pressure up to 1000 kg/cm2. These results indicate that the reaction of Ps with nitrobenzene is almost diffusion-controlled in benzene solutions but not in hexane solutions (at low pressures). The increase of the rate constant with pressure in hexane can be explained by considering the decrease of the volume occupied by Ps upon the formation of the Ps-nitrobenzene complex in molecular liquids. © 1990.