Positron Annihilation in a Dilute Metal: Li-NH3Solution

Abstract

The momentum distribution of photons from positrons annihilating in lithium-ammonia solutions of various concentrations has been measured. For all except very dilute solutions, the momentum distribution was found to be independent of concentration and unlike the distribution for ammonia or for a metal. At extremely low concentrations, the distributions resemble more that of pure ammonia. No effect due to a magnetic field was observed for the solutions although a small effect was noted for pure liquid ammonia. In addition the momentum distribution for a concentrated solution was observed to change slightly over the temperature range -164°C to 13°C. These data suggest the formation of a positronium state in this dilute metallic solution.