Oscillation of sub-nano bubbles in room temperature ionic liquids observed by positron annihilation rate

Hirade, Tetsuya  

Positronoum (Ps) has negative work function in insulating materials and the Ps bubbles which size is smaller than a nano meter can form with the repulsion between Ps and surrounding molecules in liquids. Age-momentum correlation (AMOC) measurements of positron annihilation was performed to understand the anomalous positron annihilation lifetime in room temperature ionic liquids (IL), and it was suggested that the Ps bubble formation is anomalously slow in IL. The pick off annihilation rate of ortho-Ps in bubble depends on the size of the bubble. Hence it is probably possible to investigate the slow Ps bubble formation process, such as the bubble oscillation, by observing the ortho-Ps pick off annihilation rate. To obtain the oscillation of the pick-off annihilation rate of ortho-Ps, subtraction of the simulated exponentially decay curve from the measured curve was performed. The oscillation of the ortho-Ps pick-off annihilation rate was successfully observed.