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Radiation chemistry is a subdivision of nuclear chemistry which is the study of the chemical effects of radiation on matter; this is very different from radiochemistry as no radioactivity needs to be present in the material which is being chemically changed by the radiation. An example is the conversion of water into hydrogen gas and hydrogen peroxide. ==Radiation interactions with matter== As ionizing radiation moves through matter its energy is deposited through interactions with the electrons of the absorber.〔J. W. T. Spinks. R. J. Woods: An Introduction to Radiation Chemistry, Third Edition, John-Wiley and Sons, Inc., New York, Toronto 1990. ISBN 0-471-61403-3〕 The result of an interaction between the radiation and the absorbing species is removal of an electron from an atom or molecular bond to form radicals and excited species. The radical species then proceed to react with each other or with other molecules in their vicinity, it is the reactions of the radical species that are responsible for the changes observed following irradiation of a chemical system.〔Turner, J.E. Atoms, Radiation, and Radiation Protection. United States: Pergamon Books Inc.,Elmsford, NY, 1986. Print〕 Charged radiation species (α and β particles) interact through Coulombic forces between the charges of the electrons in the absorbing medium and the charged radiation particle. These interactions occur continuously along the path of the incident particle until the kinetic energy of the particle is sufficiently depleted. Uncharged species (γ photons, x-rays) undergo a single event per photon, totally consuming the energy of the photon and leading to the ejection of an electron from a single atom.〔Bigelow, R. A. Radiation Interactions in Matter.〕 Electrons with sufficient energy proceed to interact with the absorbing medium identically to β radiation. An important factor that distinguishes different radiation types from one another is the linear energy transfer (LET), which is the rate at which the radiation loses energy with distance travelled through the absorber. Low LET species are usually low mass, either photons or electron mass species (β particles, positrons) and interact sparsely along their path through the absorber, leading to isolated regions of reactive radical species. High LET species are usually greater in mass than one electron,〔Essentials of radiation, biology and protection, S. Forshier, Cengage Learning, Jul 22, 2008, p46〕 for example α particles, and lose energy rapidly resulting in a cluster of ionisation events in close proximity to one another. Consequently the heavy particle travels a relatively short distance from its origin. Areas containing a high concentration of reactive species following absorption of energy from radiation are referred to as spurs. In a medium irradiated with low LET radiation the spurs are sparsely distributed across the track and are unable to interact. For high LET radiation the spurs can overlap, allowing for inter-spur reactions, leading to different yields of products when compared to the same medium irradiated with the same energy of low LET radiation.〔Simon M. Pimblott , Jay A. LaVerne, J. Phys. Chem., 1994, 98 (24), pp 6136–6143, DOI: 10.1021/j100075a016, Publication Date: June 1994〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Radiation chemistry」の詳細全文を読む スポンサード リンク
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