Positronium spin conversion in Li–ammonia solution

Abstract

The time spectrum of positrons annihilated in lithium–ammonia solutions of various concentrations was analyzed. It was found that the decay rate of the longest lived component increases at the same time as the Li concentration increases; likewise its intensity increases until it attains 100% at high concentration. The results are interpreted in terms of electron exchange collisions which convert triplet positronium to singlet and vice versa. The triplet to singlet conversion rate γ was found proportional to the number of Li atoms dissolved per unit volume.