Track core

Recently, a biexcitonic quenching mechanism has been proposed to explain the variation of scintillation intensity in liquid argon (LAr) with the LET and quality of incident radiation (Hitachi et al., 1992). According to this, quenching occurs mainly in the track core due to high-energy deposition density. This... 

Swiatla-Wojcik D, Buxton GV (1998) Modelling of linear energy transfer effects on track core processes in the radiolysis of water up to 300°C. J Chem Soc Faraday Trans 94 2135-2141 Sychev AY, Isak VG (1995) Iron compounds and the mechanisms of the homogeneous catalysis of the activation of O2 and H2O2 and of the oxidation of organic substrates. Russ Chem Rev 12 1105-1129... 

The relatively low overall yields of radicals were attributed to the high recombination rate of closely spaced base ion radicals in the densely ionized track core. The proximity of these radicals coupled with Coulomb attractions facilitates fast core ion radical-ion radical recombination. However, neutral sugar radicals in the core are not affected by Coulomb attractions, thus they do not recombine as readily. Therefore, most of the neutral sugar radicals stabilized at 77 K are presumed to form in the core. On the other hand, most of the base radicals that are stabilized at 77 K are assumed to form in the isolated, low LET-like spurs formed by delta-rays. The similarity in the behavior of the base radicals in argon ion-beam irradiated samples and in y irradiated samples lends support to this picture.In this model C(N3)H is in equilibrium with C and is found to act as an ion-radical. 

Table 3). Based on the experimental design (neutral sugar radicals were probed), the sphere modeled is best thought of as a section of the track cored The diameter of the core thus determined is, again, in good agreement with predictions from theoretical track structure modelsd Thus, these experiments provided the first quantitative experimental confirmation of the track structure models proposed by Chatteq ee and his co-workers... 

Emission measurement from the excited states is also a powerful method to investigate the ion beam radiation chemistry because a very sensitive time resolved photon-counting technique can be applied. In 1970s, temporal behavior of the emission from benzene excited states in 40 mM benzene in cyclohexane irradiated with pulsed proton and He ion particles was measured and compared with UV pulse irradiation. It was found that immediately after the irradiation there is a short decay (< 10 ns) followed by a longer decay corresponding to the life-time of the benzene excited states (26-28 ns). The fraction of the shorter decay component increases with increasing LET of the particle. This was explained by a quenching mechanism that radical species formed in the track core attack and quench the benzene excited states, which would take place only shorter period less than 10 ns after irradiation [69]. 

K. Kimura, Ultra fast luminescence in heavy-ion track-cores in insulators Electron-hole plasma, Nucl. Instr. Meth. Phys. Res. B191, 48 (2002)... 

Mozumder, A., Track-core radius of charged particles at relativistic speed in condensed media, J. Chem. Phys., 60, 1145-1148 (1974). 

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