| Project/Area Number |
01540360
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
物理化学一般
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| Research Institution | University of Tokyo |
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Principal Investigator |
ITO Yasuo Research Center for Nuclear Science and Technology, Associate Professor, 原子力研究総合センター, 助教授 (40011150)
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| Co-Investigator(Kenkyū-buntansha) |
ZHICHENG Zhang Fac. Engin. Univ. of Tokyo, Visiting Research Fellow (on leave from Univ. Sci. a
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| Project Period (FY) |
1989 – 1990
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| Project Status |
Completed (Fiscal Year 1990)
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| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1990: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1989: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | Positronium / Radiation spur / Excited States / Electron Scavengers / ポジトロン / 放射線化学 / スパ-反応 / 共鳴反応 |
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| Research Abstract |
Positronium (Ps) is a hydrogen-like atom which is formed between positron (e^+) and electron (e^-). The mechanism of Ps formation is not yet made clear. There are two models of Ps formation. The Ore model assumes that energetic (epithermal) e^+ picks up an electron from the medium, and the spur model assumes that e^+ is nearly thermalized in its own terminal radiation spur and combines with e^- (excess electron) that is ejected by ionization.
The head investigator has long been involved in the research of this problem, and has a conclusion that the spur model is a better model than the former at least regarding Ps formation in condensed molecular substances. The precious study aims to advance this viewpoint and hopefully make the "Ps formation experiment" a research tool to study fast intra-spur reactions.
The experiments have been to measure Ps yield in various mixtures inert and electrophilic molecules. The importance of the spur process has been confirmed. Moreover a new aspect of Ps formation, namely "Ps formation from excited molecular states" has been found. By the discovery of this new process, the picture of Ps formation has been improved substantially, and we have published a thesis titles "A New Model of Positronium formation".
There still remains problems concerning evaluation of mutual relative importance of the Ore model and the spur model. These problems have been summarized in a review article.
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