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

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 τ3 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.