Positronium formation at low temperatures in polymers and other molecular solids

Positronium (Ps) formation by weakly localized long-lived electrons (trapped electrons or anions) and positrons at low temperatures successfully explained the Ps formation enhancement at low temperatures observed in polymers and molecular solids. This Ps formation process is different from Ore process and spur process. The phenomena expected by this Ps formation mechanism, such as an effect due to visible light exposure, a density dependence of weakly localized electrons and the delayed Ps formation were successfully observed as the experimental evidence of this Ps formation process. Some possibilities for application of this new Ps formation were also given. One is a new idea for estimation of spin polarity of positrons. Another is the possibility of application to study the local molecular motion by observing the decay of Ps formation intensity.