STUDIES ON CHEMICAL-KINETICS OF POSITRONIUM COMPLEX-FORMATION

The complex formation between ortho-positronium and N-(p-substituted-phenyl) glycine (p-RPhG, G = NHCH2COOH; R = NO2, Cl, H, CH3, CH3O) or N-(m-substituted-phenyl) glycine (m-RPhG, R = NO2, Cl) in solutions of 30% (v/v) ethanol-water and 20% (v/v) dioxane-water is discussed. The application of a BaF2 Scintillation counter to a positron annihilation lifetime spectrometer is described. By means of this new type of spectrometer, the complex formation reaction rate constants of ortho-positronium with the glycine derivatives in solutions are determined. The results indicate that the rate constants mainly depend on the conjugation effect at the benzene ring, the induction effects of the substitutes on the phenyl and solvents. There exists a linear free-energy relationship between rate constants and the basicities of N-substituted phenyl glycines in ortho-positronium-glycine complex formation. It means that the transient complex formation of ortho-positronium with molecules is like a general chemical reaction and obeys classical rules.