Further studies on positron lifetimes in γ-irradiated teflon in low dose range

Abstract

Positron lifetime spectra in teflon are measured as a function of γ-dose from 3000 Ci cobalt-60 assembly. The irradiations and positron lifetime measurements are carried out, both in air and vacuum. The values of lifetimes τ₁, τ₂, τ₃ and their respective intensities I₁, I₂, and I₃ are determined with the help of three component fit. Electron spin resonance, density, dielectric constant, and nuclear magnetic resonance measurements are also carried out on teflon samples irradiated in a similar way. Initial γ-dose results in increased free volume of voids, where orthopositronium rests. Hence the lifetime t₃ increases. As the dose is increased further quenching effect of free radicals becomes dominant and lifetime of positronium decreases. Similar trend is observed in dielectric constant and NMR data.