Radiolytic products

Alkanes, as radiolytic products 907 Alkanesulphinates as radiolytic products 907 in stereospecific synthesis of sulphoxides 298, 299... 

Sulphones (coni.) allenic - see Allenic sulphones allyl - see Allyl sulphones aryl unsaturated alkyl - see Aryl unsaturated alkyl sulphones aryl vinyl - see Aryl vinyl sulphones as radiolytic products 907 bicyclic - see Bicyclic sulphones bis(/ -hydroxyalkyl) - see Bis... 

Phenomenological evidence for the participation of ionic precursors in radiolytic product formation and the applicability of mass spectral information on fragmentation patterns and ion-molecule reactions to radiolysis conditions are reviewed. Specific application of the methods in the ethylene system indicates the formation of the primary ions, C2H4+, C2i/3+, and C2H2+, with yields of ca. 1.5, 1.0, and 0.8 ions/100 e.v., respectively. The primary ions form intermediate collision complexes with ethylene. Intermediates [C4iZ8 + ] and [CJH7 + ] are stable (<dissociation rate constants <107 sec.-1) and form C6 intermediates which dissociate rate constants <109 sec. l). The transmission coefficient for the third-order ion-molecule reactions appears to be less than 0.02, and such inefficient steps are held responsible for the absence of ionic polymerization. 

The product yield should be independent of temperature and insensitive to variation of experimental conditions during the course of radiolysis such as accumulation of radiolytic products, change in pH and so forth. 

Hydrogen halides will easily add to unsaturated compounds under radiolysis or photolysis. The free-radical chain reaction process is initiated by the dissociation of the halide or by the radiolytic production of radicals from the halide or the organic compound. Thus, for the radiolysis of a mixture of HBr and ethene the postulated initiation is... 

Unique radiolytical products (URP) in irradiated food are usually formed by the secondary reactions of water radicals, eh, H, and OH, and to a lesser extent by the direct action of radiation, especially for foods with considerable water content. Due... 

Sunaryo GR, Katsumura Y, Ishigure K (1995) Radiolysis of water at elevated temperatures-III. Simulation of radiolytic products at 25 and 250°C under the irradiation with y rays and fast neutrons. Rad Phys Chem 45 703-714... 

Finally, solute radical ions can be generated by light-induced, one-photon or multiphoton ionization of their parent compounds (Chaps. 5 and 16). This approach is particularly useful in the ultrafast studies of short-lived, unstable radical ions that aim to unravel their solvation, recombination, reaction, and vibrational relaxation dynamics of the primary charges (see, e.g., Chap. 10). Whereas the time scale of radiolytic production of secondary ions is always limited by the rate with which the primary species reacts with the dispersed parent molecules, light-induced charge separation can occur in <100 fsec. There are many studies on photoionization of solute molecules in liquid solutions we do not intend to review these works. 

Understandably, most workers who use radiolysis, photoionization, CTFS, or CTTS as the means for generation of (secondary) radical ions pay little attention to the nature of short-lived precursors of these ions. After all, the subject of interest is a secondary rather than a primary ion. This ad hoc approach is justifiable because radiolytic production is just another means of obtaining a sufficient yield of the radical ion. Quite often in such studies, the radiolysis is complemented by other techniques for radical ion generation, such as plasma oxidation, electron bombardment-matrix deposition, and chemical and electrochemical reduction or oxidation. While the data obtained in these studies are useful, there is little radiation chemistry in such—nominally, radiation chemistry—studies. 

Photochemistry and radiation chemistry of biomolecules in vacuo and in water. Radiolytic products from Auger cascade are interesting from the viewpoint of radiotherapy. The development of irradiation systems is required in which liquid samples can be irradiated with vacuum UV or ultrasoft x-rays of high intensity. 

Chemical and biological effects of ionizing radiation are thought to occur through two main mechanisms direct interaction of the radiation with food components and living cells in materials exposed to it, and indirect action from radiolytic products, such as the radicals formed from water molecules (see Chap. 12). 

This is a process that is at present being integrated in the current models of spent fuel stability in repository conditions, but some work is still necessary in order to ascertain the reactions and mechanisms that control the reductive passivation of the U02 surface and the inhibition of the radiolytic production of oxidants. 

Radioprotection. The processes of crosslinking and degradation observed in polymers irradiated in the pure state can also be observed in polymers irradiated in solution. The presence of a solvent can intervene in the reaction in several ways thus it allows increased polymer mobility, and some of the radiolytic products of the solvent may react with the polymer or with the polymer radicals, etc. The polymer-water system is of particular interest in that it provides a simple model for some radiobiological systems and can be analyzed far more readily. 

In the presence of water, polymers reveal a greater sensitivity to radiation. This increase has been shown to be caused by the indirect effect of radiation—i.e., the radiolytic products of water react with and form new radicals in the dissolved polymer. This indirect effect is also present in aqueous biological systems. The usual ESR techniques do not enable such radicals to be readily revealed because of the high absorption of water, but other techniques using radical scavengers reveal their presence. 

Major damage results from the radiolytic products of water experiments with aqueous solutions of polymer reveal such effects but could hardly increase the damage by much more than a factor of about 10. 

Tripathi, S.C., Bindu, P., Ramanujam, A. 2001. Studies on the identification of harmful radiolytic products of 30% TBP-n-dodeeane-HN03 by gas-hquid chromatography. I. Formation of diluent degradation products and their role in Pu retention behavior. Sep. Sci. Technol. 36 (7) 1463-1478. 

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