External electric field effect on positronium formation in some polar and nonpolar polymers at different temperatures

External electric field (<= 100 kV/cm) effect on positronium (Ps) formation in nonpolar and polar polymeric samples have been studied under different temperatures (-120 to 80 degrees C). Results indicate that there is completely no electric field effect on Ps formation in the studied polar samples. It was also observed that at room temperature, electric field effectively suppresses Ps formation probability in nonpolar polymers; however, at low temperature (below -60 degrees C for polyethylene), electric field effect is significantly weakened. It is concluded that electric field influences probability of electron-positron recombination with Ps formation in the spur outside of the positron blob. However, additional Ps formation on the trapped electrons at low temperatures, positron (electron) trapping by polar groups in polymers essentially inhibits electric field effect. (c) 2006 Elsevier B.V. All rights reserved.