Positronium formation on trapped electrons in n-heptadecane

Positronium (Ps) formation on trapped electrons as a function of positron irradiation time by high-energy positrons and temperature were investigated in the case of n-heptadecane, as a representative of odd-numbered alkanes. It was found that the rise of Ps intensity with temperature in the range below 200 K results from an increasing positron mobility, at constant trapped electron density. Thermal collapse of the traps is responsible for reduction of Ps intensity at higher temperatures.