Positronium Annihilation in Molecular Substances

TLDR: The behavior of the Ps atom in molecular substances, particularly liquids, is investigated in this article, where the pickoff rates of oPs in various liquid compounds are found to have a simple empirical relationship to the values of the surface tension of the liquids.

Abstract: The behavior of the Ps atom in molecular substances, particularly liquids, is investigated. The pickoff rates of o‐Ps in various liquid compounds are found to have a simple empirical relationship to the values of the surface tension of the liquids. The relationship is found to have a theoretical foundation. The Ps atom is highly localized in a cavity created by the balance of various molecular forces inside the liquid. From the above relationship, other simple relationships between the pickoff rates of o‐Ps and the various properties of the medium, e.g., polarizability, cohesive energy density, etc., and the temperature or pressure changes can be derived and explained. The diffusion of o‐Ps is discussed. A similar approach can also be used for molecular solids.