Positronium bubble oscillation in room temperature ionic liquids

Hirade, Tetsuya  

Ps has negative work function in insulating materials and the repulsion between Ps and surrounding molecules can form a bubble in liquids. However, it is needed to lose energy to be in a stable bubble state. Therefore the oscillation of the bubble size is expected. The ortho-Ps pick off annihilation probability depends on the size of the Ps bubble and hence the oscillation on the lifetime spectra is expected. In the case of usual liquids, bubble formation time is not so slow and then the oscillation can not be observed by the positron annihilation lifetime measurements with the time resolution of about 200 ps. Now the bubble formation in IL is slow and then the expected oscillation on the lifetime spectra was successfully observed.