Correlation between the Inhibition of Positronium Formation by Scavenger Molecules, and Chemical Reaction Rate of Electrons with these Molecules in Nonpolar Liquids

o-Ps yields were determined in various liquid hydrocarbons, tetramethylsilane, and mixtures thereof as a function of C2H5Br and CCll concentration. These molecules are known to be good electron scavengers and positronium inhibitors as well. The spur reaction model of Ps formation predicts a correlation between the inhibition coefficient and the chemical rate constant of electrons with scavenger molecules.

We found that the dependence of the inhibition coefficient on the work function (VOo)f electrons in different liquids shows a very unusual behavior, similar to that recently found for the chemical rate constants of quasifree electrons with the same scavenger molecules. The inhibition coefficient as a function of Vo had a maximum for C2HsBr, while it increased monotonously with decreasing V, for CC14.

The inhibition coefficient for C2H5Br in a 1:l molar tetramethylsilane-n-tetradecane mixture was found to be greater than in both of the pure components. The clear correlation found between electron scavenging rate constants and positronium inhibition constitutes the severest test to date of the spur reaction model of positronium formation.

The importance of the positron annihilation method from the point of view of radiation chemistry is also emphasized