Pulse radiolysis applications

The application of techniques of pulse radiolysis offers the potential to determine rates of primary radiolysis induced reaction processes. This knowledge can be of great value in the determination of redox processes of Pu ions occurring in a wide variety of aqueous solutions. As a matter of fact, such information is essential to a prediction of the Pu oxidation states to be expected in breached repository scenarios. For an... 

Carotenoid radicals — Many of the important oxidations are free-radical reactions, so a consideration of the generation and properties of carotenoid radicals and of carbon-centered radicals derived from carotenoids by addition of other species is relevant. The carotenoid radicals are very short-lived species. Some information has been obtained about them by the application of radiation techniques, particularly pulse radiolysis. Carotenoid radicals can be generated in different ways. "... 

Ogasawara, Ma Application of Pulse Radiolysis to the Study of Polymers and Polymerizations. VoLlQ5,pp. 37-80,... 

Investigations of the kinetics of hole transfer in DNA by means of pulse radiolysis of synthetic ODNs have provided details about the hole transfer process, especially over 1 /is, including the multi-step hole transfer process. Based on the investigation of the kinetics of hole transfer in DNA, development of the DNA nanoelectronic devices is now expected. An active application of the hole transfer process is also desirable from a therapeutical point of view, since hole transfer may play a role in improvement of quantum yield and selectivity of DNA scission during photodynamic therapy. The kinetics of the hole transfer process is now being revealed, although there is still much research to be performed in this area. The kinetics of adenine hopping is another area of interest that should be explored in the future. 

One striking prediction of the energy gap law and eq. 11 and 14 is that in the inverted region, the electron transfer rate constant (kjjj. = ket) should decrease as the reaction becomes more favorable (lnknr -AE). Some evidence has been obtained for a fall-off in rate constants with increasing -AE (or -AG) for intermolecular reactions (21). Perhaps most notable is the pulse radiolysis data of Beitz and Miller (22). Nonetheless, the applicability of the energy gap law to intermolecular electron transfer in a detailed way has yet to be proven. 

AK Pikaev, SA Kabakchi, IE Makarov, BG Ershov. Pulse Radiolysis and its Application. Moscow Atomizdat, 1980, pp 3-290 [in Russian]. 

Many transition metal complexes have been considered as synzymes for superoxide anion dismutation and activity as SOD mimics. The stability and toxicity of any metal complex intended for pharmaceutical application is of paramount concern, and the complex must also be determined to be truly catalytic for superoxide ion dismutation. Because the catalytic activity of SOD1, for instance, is essentially diffusion-controlled with rates of 2 x 1 () M 1 s 1, fast analytic techniques must be used to directly measure the decay of superoxide anion in testing complexes as SOD mimics. One needs to distinguish between the uncatalyzed stoichiometric decay of the superoxide anion (second-order kinetic behavior) and true catalytic SOD dismutation (first-order behavior with [O ] [synzyme] and many turnovers of SOD mimic catalytic behavior). Indirect detection methods such as those in which a steady-state concentration of superoxide anion is generated from a xanthine/xanthine oxidase system will not measure catalytic synzyme behavior but instead will evaluate the potential SOD mimic as a stoichiometric superoxide scavenger. Two methodologies, stopped-flow kinetic analysis and pulse radiolysis, are fast methods that will measure SOD mimic catalytic behavior. These methods are briefly described in reference 11 and in Section 3.7.2 of Chapter 3. 

Application of pulse-radiolysis techniques revealed that the following intramolecular and intermolecular electron-transfer reactions all exhibit a significant acceleration with increasing pressure. The reported volumes of activation are -17.7 0.9, 18.3 0.7, and... 

Here the progress in the picosecond and subpicosecond pulse radiolysis is described first and then the experimental studies on the kinetics of the geminate ion recombination is explained in connection with their application to advanced technology such as the next generation nanolithography and nanotechnology. 

Further detailed kinetics of the geminate recombination of electrons and positive ions and their application to the advanced technology will be studied by higher time resolution of the femtosecond pulse radiolysis and both by the higher S/N ratio and the wider wavelength monitoring light of the improved subpicosecond pulse radiolysis shown in Fig. 7. 

Basic and applied researches on charged particle and photon-induced reactions of polymers are surveyed. The basic parts are fundamentals of radiation effects on polymers and pulse radiolysis studies on polymers. The intermediate parts are a great diversity of radiation effects on polymers and reaction mechanisms of electron beam (EB) and x-ray resists. The applied parts are economic scale of utilization of radiation and industrial application of radiation to polymers. 

It has been shown that Pulse Radiolysis is a powerful tool for the study of the properties of such short lived intermediates (1,2). The application of this technique is based on the capability of producing a large variety of aliphatic radicals (vide infra) within less than 1 pis in physically observable concentrations. Thus one can follow by different techniques the kinetics of disappearance of the initially formed radicals and the properties of unstable intermediates, if formed, in these reactions. The most common detection technique is the spec-trophotometric one, but changes in specific conductivity, EPR, resonance Raman, etc., can be applied and are often helpful in elucidating the nature of the short lived intermediate observed. 

Finally it should be pointed out that the pulse radiolysis technique can be applied to the elucidation of the detailed mechanisms of a variety of catalytic processes. Here two examples for this application will be presented. 

The techniques described here for monitoring flash-photolyzed solutions are clearly applicable to other situations in which the solution s composition is modified suddenly. Henglein and co-workers have used them in some interesting electrochemical studies of free radicals generated by pulse radiolysis [77,78]. They have been able to resolve events on a 10"5 time scale. 

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