Positronium formation in low temperature polymers

The trapped electrons or anions in molecular solids and polymers cause the enhancement of positronium (Ps) formation at low temperatures during positron annihilation lifetime (PAL) measurement. It used to be understood that the physical structural change caused the enhancement. However, it has been clarified that the enhancement of Ps formation at low temperatures are caused by the reaction of free positrons and localized electrons such as trapped electrons or anions by observing several expected phenomena. The detail of the mechanism of this new Ps formation and the expected experimental results are introduced. Moreover the apparent activation energies of local motions of polymers were successfully obtained with the PAL experiment. (C) 2003 Elsevier Ltd. All rights reserved.