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Positron is a useful probe on the order of nano-meter (so called nano-meter probe) to investigate molecular and atomic structures of substances. Especially, our group are using it for studying polymer structures. However the basic process has not been well understood, our group has been studying on the formation and annihilation of positronium in polymers. Further more we are developing a slow positron apparatus, which is powerful to study structures at each depth.

So far our study has been focused on epoxy resins, polyethylens, and polypropylene.

1. Probe of polymer structures
   Positrons form positronium (Ps) in substances by picking electrons from surrounding structures. Ps has a hydrogen-like atom and there are two states: ortho-Ps and para-Ps. Ortho-Ps can have longer life in larger holes and annihilates with electrons located on the walls of the holes. The life and intensity are affected by polymer and chemical structures and thus it is a good measure of polymer characteristics.
2. Thermosetting polymer: epoxy resins
   Suzuki T.,Miura T.,Oki Y.,Numajiri M.,Kondo K., Y.Ueda,Y.Shiomi and Ito Y. " Polymerization of bisphenol-A dicyanate studied by positron annihilation" Material Science Forum. Vols.175-178,pp.785-788(1995)
   • Suzuki T. " Polymerization of epoxy resins and characteristics of the molding compounds studied by positron annihilation. " Journal of the Adhesion Society of Japan, vol.30,pp.372-376(1994)
   • Suzuki T.,Oki Y.,Numajiri M.,Miura T.,Kondo K., Ito Y. and Shiomi Y. " Positron annihilation and novolac epoxy resins" Journal of Applied Polymer Science, 49,pp.1921-1929(1993)
   • Suzuki T.,Oki Y.,Numajiri M.,Miura T.,Kondo K., and Ito Y. �@ "Positron annihilation and polymerization of epoxy resins" Polymer, vol 34,No.7,pp.1361-1365(1993)
3. Thermoplastic polymer: polyethylene and polypropylene
   • Kobayashi Yoshinori, Kojima Isao, Hishita shunichi, Suzuki Takenori Asari Eiji, and Kitajima Masahiro "Damage-depth profiling of an ion-irradiated polymer by monoenergetic positron beams" Physical Review B, vol.52, Number 2,823-828(1995)
   • Suzuki T.,Miura T.,Oki Y.,Numajiri M.,Kondo K., and Ito Y. " Structure dependence of gamma-ray irradiation effects on polyethylenes studied by positron annihilation" Radiation Physics and Chemistry 45,pp.797-804(1995)
   • Suzuki T.,Miura T.,Oki Y.,Numajiri M.,Kondo K., and Ito Y. " Positron irradiation effects on polypropylene and polyethylene studied by positron annihilation" Radiation Physics and Chemistry 45,pp.657-663(1995)

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