Positronium bubble formation in room temperature ionic liquids

16th International Conference on Positron Annihilation

Hirade, T.^1,2 ; Oka, T.^3

Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency, Ibaraki, 319-1195, Japan^1

Graduate School of Science and Engineering, Ibaraki University, 4-12-1 Narusawa, Hitachi, Ibaraki, 316-8511, Japan^2

Research Institute for Science and Engineering, Waseda University, 3-4-1, Shinjuku, Tokyo 169-8555, Japan^3

关键词: Age-momentum correlation;    Core electrons;    Energy distributions;    Formation process;    Momentum distributions;    Nano seconds;    Ps formations;    Room temperature ionic liquids;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/443/1/012060/pdf
DOI  :  10.1088/1742-6596/443/1/012060

来源: IOP

【 摘 要 】

Positron annihilation age-momentum correlation (AMOC) measurements were performed for a room temperature ionic liquid (IL) to investigate positronium (Ps) bubble formation process. The Ps just after the formation must be squeezed Ps that has larger probability of annihilation with core electrons in liquids. However, it has been believed that the bubble formation in liquids is very fast and difficult to observe the squeezed Ps experimentally. When the bubble formation is slow, it can give broader energy distribution of annihilation gamma-rays at young age region. There have been several experimental results showing young age broadening and some of them are interpreted as the delayed Ps formation. However, if the bubble formation is slow, it also can be a reason of the young age broadening. If the squeezed Ps and the free positron give different momentum distributions by annihilation with core electrons on different atoms, it is possible to detect the annihilation from squeezed Ps at the young age, i.e. the bubble formation can be observed. We found larger high momentum distribution at young age in IL and it might be caused by the delayed bubble formation in IL. Positron annihilation methods can be a tool to investigate the IL molecular dynamics at the time range of pico-nano second and in the scale of sub-nano to nano meter.