Positron annihilation lifetime (PAL) and Doppler broadening (DB) measurements were carried out in four semicrystalline polymer samples, viz., polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), polytetrafluoroethylene (PTFE), and Nylon 6, 6 (PA). A correlation between the S and Wparameters which reflect the electron momentum, and the orthc-positronium (0-Ps) lifetime reflecting the electron densities in free volume sites is observed. Interestingly, the present results support the known intuition that 0-Ps has a higher momentum component compared to p-Ps and free annihilations but different from that observed by Davies and Pethrick.') Manasagangotri, Mysore 570 006, India.1'

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