We performed positron annihilation lifetime and coincidence Doppler broadening measurements on γ-irradiated high-density polyethylene (HDPE) at temperatures of 80, 293 and 373 K as a function of the measurement time. At 293 K, it is shown that more than one order of magnitude increase in free radical concentration (1018 spins/g) results in a reduction of the ortho-positronium (o-Ps) yield only by ∼2% for HDPE irradiated in vacuum. Stronger Ps formation inhibition was observed in an HDPE irradiated in air, which is attributed to a larger C=O concentration. After temperature was raised from 293 to 373 K, free radicals were found ineffective to the Ps formation. Because of the stabilization of C=O-e+ complex at 80 K, enhanced positron trapping by oxygen was observed. © 2004 Elsevier B.V. All rights reserved.
Yu, R. S., Suzuki, T., Djourelov, N., Kondo, K., Ito, Y., & Shantarovich, V. (2005). Positron annihilation lifetime and coincidence Doppler broadening study of γ-irradiated polyethylene. Chemical Physics, 313(1–3), 63–69. https://doi.org/10.1016/j.chemphys.2004.12.013