Positronium bubble formation in room temperature ionic liquids

Hirade, Tetsuya  ; Oka, Toshitaka*   

Room temperature ionic liquids (IL) have Negligible vapor pressure and other interesting properties. There are many considerable applications of ionic liquids, because of the environmentally friendly property. The radiation chemistry study for IL is very important for nuclear fuel reprocessing. The solvation of excess electrons is affected by molecular dynamics in sub-nano meter scale. Positronium (bond state of electron and positron) has a negative work function and form a bubble in liquids. The formation time is usually very fast as about 1ps that is difficult to observe by experiment. However we succeeded to observe the delayed bubble formation process in IL by use of the positron annihilation age-momentum correlation (AMOC) measurement. This phenomena could explain the anomalous long lifetime of the singlet positronium intrinsic annihilation lifetime. Probably only the lifetime spectra can give the information of bubble formation time in IL.