Temperature dependence of positronium bubble oscillation in room temperature ionic liquids

Hirade, Tetsuya  

Positronium (Ps) creates a bubble in liquids because of a negative work function and the ortho-Ps annihilation probability depends on the size of the bubble. The oscillation of the ortho-Ps annihilation probability at very young positron ages, i.e. before 1ns, was successfully observed in room temperature ionic liquids (RTILs). The frequency of the oscillation deceased just above the melting point. Moreover, the stable annihilation rates at older positron ages in RTILs are much smaller than the annihilation rates of other liquids having similar surface tensions, and the rates do not become smaller at higher temperatures. These phenomena are probably caused by the complicated RTIL structure.