The intermediate lifetime
(0.2–0.5 ns) component s2, with intensity I2, results from the
annihilation of positrons trapped at the defects present in the
crystalline regions of the medium. The longest-lived component
s3, with intensity I3, is due to pick-off annihilation of ortho-
Positronium (o-Ps) in the free volume sites present mainly in the
amorphous regions of a polymer sample.