Positronium Reactions in Solutions

Abstract

The reactions of Ps in solutions, also called Ps quenching, have been a very important topic of the chemical physics of positron annihilation. In particular, Ps reactions were much studied up to 1975 and after 1986, while Ps formation was an important topic in the interval 1975–1986. The rate constants of the Ps reactions, k, are approximately determined from the measured o Ps lifetimes, τ3, using the equation

$$ \lambda _3 \; = \;\tau _3^{ - 1} \; = \;\lambda _p \; + \;kc, $$

(8.1)

where $\lambda _p \; = \;\tau _p^{ - 1}$ the pick off decay rate and c the concentration of the reactant reacting with Ps. Many Ps reactions are diffusion controlled, and hence, they belong to the class of fast reactions which can normally be studied directly only in radiation and photo-chemistry. For example, positronium seems to react with MnO₄- and Mn⁺⁺ in water by oxidation and spin conversion, respectively, and with nitrobenzene in benzene.