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Hirade, Tetsuya
Radiation Physics and Chemistry, 76(2), p.84 - 89, 2007/02
Times Cited Count：3 Percentile：25.51(Chemistry, Physical)There are many connections between radiation and positronium chemistry. The Spur Reaction model proposed by Mogensen needs much radiation chemistry knowledge. On the other hand, the Spur Reaction model could give new ideas to radiation chemists. Positronium formation reaction is very fast and hence there is a good relationship between reactions observed by a pulse radiolysis measurement and positronium formation, which was shown by Dupratre et al. Enhancement of positronium formation at low temperatures was successfully explained by the reaction of trapped electrons and positrons. The trapped electrons have been studied well by radiation chemists. That knowledge was needed to propose a new idea to explain the positronium formation at low temperatures. And now, probably it is becoming possible to use the positronum formation reaction to study the trapped electrons. Positron methods will be able to be used for the radiation chemistry research.
Hirade, Tetsuya
Acta Physica Polonica A, 107(4), p.615 - 622, 2005/00
Positronium (Ps) formation by weakly localized long-lived electrons (trapped electrons or anions) and positrons at low temperatures successfully explained the Ps formation enhancement at low temperatures observed in polymers and molecular solids. This Ps formation is completely different from Ps formations by Ore process or spur process. The phenomena expected by this Ps formation mechanism, such as an effect due to visible light exposure, the density effect of weakly localized electrons and the delayed Ps formation were successfully observed as the experimental evidence of this Ps formation process. Some possibilities for application of this new Ps formation were also given. One is a new idea for estimation of spin polarity positrons. Another is the possibility of application to study the local molecular motion by observing the decay of Ps formation possibility by this Ps formation process.
Stepanov, S. V.*; Byakov, V. M.*; He, C.*; Hirade, Tetsuya; Mikhin, K. V.*
Acta Physica Polonica A, 107(4), p.642 - 650, 2005/00
Role of trapped and solvated electrons in Ps formation is discussed. Combination of thermalized positron with such electrons is energetically possible and may contribute to Ps formation. Contrary to the positron reaction with a quasi-free electron, this process is not limited to picosecond times, but proceeds on a timescale of nanoseconds. In this case conventional exponential deconvolution of row lifetime positron annihilation spectra becomes questionable. Rigorous treatment of the data needs nonexponential deconvolution, based on an adequate physical input. Such an approach is suggested here. Its reduced form is used for interpretation of the Ps formation data in polyethylene, EMMA and PMMA in dark and in light vs. time of the measurement and temperature. Parameters characterized accumulation of trapped electrons and their recombination with counter ions and positrons are obtained.
Idomura, Yasuhiro
NIFS-PROC-58, p.46 - 50, 2004/07
no abstracts in English
Hirade, Tetsuya
Materials Science Forum, 445-446, p.234 - 238, 2004/02
Positronium (Ps) formation mechanism by shallowly localized long-lived electrons and positrons at low temperatures explained successfully the Ps formation enhancement at low temperatures observed in polymers and molecular solids. The expected phenomena by this Ps formation mechanism, such as effects by visible light exposure, beautiful relation between the density of shallowly localized electrons and the Ps formation and delayed Ps formation were observed. Some possibilities of application of this new Ps formation, such as a new idea of observing spin polarized positrons by this Ps formation, will be given. The shallowly localized long-lived electrons can be polarized when they are placed in magnetic field at very low temperatures. It is probably possible to see the polarity of positrons by the Ps formation with these polarized electrons. The detail of the idea will be introduced. It will be given as an invited talk.
Hirade, Tetsuya; Kumada, Takayuki
Materials Science Forum, 445-446, p.301 - 303, 2004/02
Positrons injected in molecular solids or polymers will have the positronium formation around a terminal spur of positron track, so-called positron spur, with active species in the positron spur, such as excess electrons. In this case, the electrons are not polarized. At low enough temperatures, long-lived shallowly localized electrons are accumulated by irradiation in darkness, and positrons will have a next chance to form positronium with these long-lived shallowly localized electrons. For these electrons, it is possible to make them to be polarized by applying magnetic field at very low temperatures. We successfully observed the effect of the positronium formation reaction of polarized positron and polarized electrons.
Hirade, Tetsuya
Radiation Physics and Chemistry, 68(3-4), p.375 - 379, 2003/10
Times Cited Count：17 Percentile：72.74(Chemistry, Physical)The trapped electrons or anions in molecular solids and polymers cause the enhancement of positronium formation at low temperatures during positron annihilation lifetime (PAL) measurement. This method can be applied to investigate trapped electrons and anions in polymers. The advantage of the method is that the any kinds of trapped electrons or anions can be observed. We clarified that the glow peak appeared around 240K was caused by the trapped electrons on -CH- radicals by PAL experiment.
Suzuki, Naoki*; Hirade, Tetsuya; Saito, Fuminori*; Hyodo, Toshio*
Radiation Physics and Chemistry, 68(3-4), p.647 - 649, 2003/10
Times Cited Count：23 Percentile：80.7(Chemistry, Physical)no abstracts in English
Hirade, Tetsuya
Hoshasen Kagaku, (75), p.46 - 51, 2003/03
Enhancement of positronium (Ps) formation at low temperatures has been observed in many materials since 1980's. There were some interpretations. However, none of them explained the phenomena successfully. In 1998, a new idea of the Ps formation was proposed and the expected phenomena were successfully observed. This new Ps formation process will be explained with those experimental results and the possibility of usage of Ps formation for radiation chemistry researches will be also discussed.
-irradiation on positronium formation in polymers at low temperaturesShantarovich, V. S.*; Hirade, Tetsuya; Kevdina, I. B.*; Gustov, V. W.*; Oleinik, E. F.*
Acta Physica Polonica A, 99(3-4), p.497 - 501, 2001/03
no abstracts in English
Hirade, Tetsuya; Maurer, F. H. J.*; Eldrup, M.*
Radiation Physics and Chemistry, 58(5-6), p.465 - 471, 2000/06
Times Cited Count：130 Percentile：99.13(Chemistry, Physical)no abstracts in English
Hirade, Tetsuya
JAERI-Conf 2000-001, p.306 - 309, 2000/03
no abstracts in English
Ito, Yutaka*; Hirade, Tetsuya; Hamada, Eisaku*; Suzuki, Takenori*; Ito, Yasuo*
Acta Physica Polonica A, 95(4), p.533 - 538, 1999/04
no abstracts in English
Idomura, Yasuhiro
no journal, ,
Transient plasma responses due to modulated electron heating are investigated in numerical experiments of ion temperature gradient driven trapped electron mode turbulence using gyrokinetic full-f Eulerian code GT5D. It is found that even with electron heating without particle and momentum sources such as electron cyclotron resonance heating, dominant turbulence is changed from ion turbulence to electron turbulence due to changes of the electron temperature gradient and the temperature ratio, and the resulting turbulent transport produces responses of density and rotation profiles.
