Ionizing radiation interactions

Table 5. Ionizing Radiation Interactions with Polymeric Substrates. ...

Ionizing radiation Radiation that is capable of causing ionization to occur, either directly or indirectly through interaction with matter. 

Addition of metallic oxides to isobutene polymerized by high energy radiation leads to a spectacular increase in the yield.313. It seems that some ions are stabilized by complexing with the surface of the oxide and such an interaction prevents their recombination with the gegen-ions. These observations confirm therefore the suggested cause of inefficient ionic polymerization in systems exposed to ionizing radiation. 

Irradiation of dilute aqueous solutions results in the interaction ofthe ionizing radiation with water molecules. The radiolysis of water produces hydrated electrons (eaq ", G = 2.8), hydrogen atoms (G = 0.6) and hydroxyl radicals (G = 2.8) which react with the molecules of the solutes. The use of special scavengers can convert one species to another, e.g. 

Ion Pair—Two particles of opposite charge, usually referring to the electron and positive atomic or molecular residue resulting after the interaction of ionizing radiation with the orbital electrons of atoms. 

From a chemist s viewpoint, the most important act of ionizing radiation (usually X-rays, y-rays or high energy electrons) is electron ejection. Initially the ejected electrons have sufficient energy to eject further electrons on interaction with other molecules, but the electrons ultimately become thermalised and then are able to interact "chemically". We consider first various reaction pathways for these electrons, and then consider the fate of the "hole" centres created by electron ejection. [We refer to electron-gain and electron-loss centres rather than to radical-anions and -cations since, of course, the substrate may comprise ions rather than neutral molecules. 

IEC 60544-1, Electrical insulating materials - Determination of the effects of ionizing radiation - Part 1 Radiation interaction and dosimetry, 1994. 

Hennequin C, Giocanti N, Favaudon V. Interaction of ionizing radiation with paclitaxel (Taxol) and docetaxel (Taxotere) in HeLa and SQ20B cells. Cancer Res 1996 56(8) 1842-1850. 

All of these mechanisms are felt to be important in contributing to the cytotoxicity seen with gemcitabine as a sole agent. In fact, an understanding of these interactions will be important to fully appreciate the interaction of gemcitabine with ionizing radiation as well. 

Hanna NN, Seetharam S, Mauceri HJ, et al. Antitumor interaction of short-course endostatin and ionizing radiation. Cancer J 2000 6(5) 287-293. 

Polymer radicals can also be produced by the irradiation of a polymer-monomer mixture with ionizing radiation. Thus, the interaction of ionizing radiation with polyethylene-styrene produces radical centers on polyethylene, and these initiate graft polymerization of styrene to produce poly(ethylene-gra/i-styrene) [Rabie and Odian, 1977]. 

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