Author: Y. Ito 1
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  • 1 The University of Tokyo Research Center for Nuclear Science and Technology Tokai 319-11 Ibaraki (Japan)
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Abstract  

Considering that Ps formation in condensed media has to take place in the teminal positron spur which, comprising many positive ions, provides a strong oxidizing environment for Ps, it is suggested that Ps formation via the epithemal process has to be mixed up with that of the spur process. Eventually in condensed media the observable aspect is those involving slowed down electrons and positron. When the size of the terminal positron spur is large, on the other hand, Ps via the epithermal process can survive. It appears to be possible to overcome the apparent inconsistency between the two models in this way. With this assumption admitted, we propose to investigate the intra-spur positronic processes in more detail. The spur process is an evolution of the energy level and the number of excess electrons, and Ps can be formed from various electron states in the course of the evolution: free excess electrons molecular anions, and excited molecular states. Ideas of Ps formation via resonant energy absorption and that involving vacancies are also presented. The importance of the non-exponential decay of o-Ps in the study of the positronic spur processes is also demonstrated with some recent results of scavenger effects.