Positron Lifetime Spectra in the Noble Gases

Abstract

Positron lifetime spectra have been measured in helium, neon, argon, krypton, and xenon at pressures of a few atmospheres. The annihilation rates of the free positrons are found to be time-dependent. Physical reasons, based on the strong correlation between energy and age of a positron, are suggested for this time dependence. Three parameters describing the main features of the free-positron spectrum are separated from the data, for each gas, and tabulated.