Effect of Radiation on Matter

Very primary events in the chemical effect of radiations on matter are excitation and ionization of molecules, which result in the formation of neutral free radicals and radical ions. These reactive species play vital roles in the radiation-induced chemical reactions. As they are paramagnetic with an unpaired electron, electron spin resonance (ESR) spectroscopy has been a useful method for elucidating the mechanism of radiation-induced reactions in solid matter where radical species can be trapped temporarily. Since the early days of the chemical application of ESR, this method has been applied very often to the identification and quantification of free radicals in polymers irradiated by radiation [1]. This is probably because, from the view-point of fundamental research, a variety of free radicals are readily trapped in solid polymers and, from the view-point of applied research, these free radicals have close correlation with radiation-induced crosslinking and degradation of polymers. 

The study of the effects of radiation on matter is called radiochemistry, or radiation chemistry. The two major considerations of radiochemistry are (1) how effective is radiation in producing a chemical event, and (2) what are the specific chemical changes induced by the radiation. 

Several terms are used to express the intensity of radiation (see Figure 9.8). Radiation level is a term often substituted for dose rate or exposure rate. It is generally referred to as the effect of radiation on matter i.e., the amount of radiation that is imparted from the source and absorbed by matter due to emitted radiation per unit of time. The curie is a radiological term for the physical amount of a radioactive material. A curie consists of 37 billion disintegrations per second. It is a physical amount of material that is required to produce a specific amount of ionizing radiation ... 

FIGURE 17.1 Number of species contributing to the effect of radiation on matter. PI, Primary interaction occurs in very short time CE, the cascade excitation P, the electron cloud plasma, electron relaxation LR, lattice relaxation TD, thermodynamic equilibrium PD, point-defect and DL, dislocations loops. 

Induced Radioactivity Transuranium Elements Rate of Radioactive Decay 25-10 Effect of Radiation on Matter 25-11 Applications of Radioisotopes ... 

Effect of Radiation on Matter—The ionizing power of radiation (Fig. 25-10) is the basis both of radiation s effects on matter and methods used to detect radiation. Radiation detectors include simple film badges, Geiger-Miiller (G-M) counters for routine measurements (Fig. 25-11), and scintillation counters in biomedical studies. Two units of measure are used to quantify exposure to radioactivity. One—the rad (radiation absorbed dose)— is related to the amount of radiation energy absorbed, while the other—the rem (radiation equivalent for man)—takes into account the differing effects of the various types of radiation (Table 25.5). 

The treatment of adsorption on a heterogeneous surface has constituted a topic of perennial interest, and this paper provides an extension, to the point of practical usefulness, of an approach for which the groundwork has been in existence for some time. Our interest in this matter developed out of work in this laboratory on the effects of radiation on the surfaces of solids, where changes in the nature of surface heterogeneities were obviously taking place. The results of these studies are given by Adamson, Ling, and Datta (2). 

In spectroscopy we study the effect of interaction of electromagnetic radiation on matter. For examples X-rays are produced by bombandment of metal targets with high speed electrons. So the different types of electromagnetic radiation interact with the matter and give different types of spectroscopy. 

The effect of electromagnetic radiation on matter is to induce a dipole. In a transparent dielectric medium, only the velocity of electromagnetic radiation is reduced, depending on the refractive index of the medium, which is determined by its density. The propagation constant of electromagnetic waves is given by... 

According to the studies of monomers in the organic glass matrices mentioned so far, the ion radicals formed from solute monomers relate their radiation-induced ionic polymerization to the primary effect of ionizing radiations on matter. It is concievable that the initiating species in the anionic polymerization (caxbanions) are formed by the addition of the monomer molecules to the anion radicals which result from electron transfer from the matrices to the solute monomer. The formation of the cation radicals is necessary also to initiate the cationic polymerization. 

There are several reasons for starting this account with a discussion of electromagnetic radiation. Historically, it was in this area that the quantum theory first developed. It is easier here to understand the evidence for the theory, and to appreciate some of its paradoxical consequences, than it is in the quantum theory of matter. The applications of the light-quantum hypothesis, as it was first called, also provide key pieces of evidence for the quantization of energy in atoms and molecules. Studies of the absorption and emission of radiation—the field of spectroscopy—and of the effect of light on chemical reactions—photochemistry—are very important areas of modem chemistry, in which the quantum nature of radiation is crucial. 

We can answer these questions when we understand the effect of electromagnetic radiation on matter. 

After 14 years on the faculty of Imperial College, Jacobs moved from London, England, to London, Ontario, where his research program focused on the optical and electrical properties of ionic crystals, as well as on the experimental and theoretical determination of thermodynamic and kinetic properties of crystal defects.213 Over the years his research interests have expanded to include several aspects of computer simulations of condensed matter.214 He has developed algorithms215 for molecular dynamics studies of non-ionic and ionic systems, and he has carried out simulations on systems as diverse as metals, solid ionic conductors, and ceramics. The simulation of the effects of radiation damage is a special interest. His recent interests include the study of perfect and imperfect crystals by means of quantum chemical methods. The corrosion of metals is being studied by both quantum chemical and molecular dynamics techniques. 

The effect of electromagnetic radiation on matter will depend on the photon s energy, which is, as we previously discussed, given by ... 

In addition to the obvious environmental effect of airborne particulate matter, there have been a number of studies which have shown that particles have direct effects on the climate. Particles can scatter and absorb solar radiation, change levels of precipitation, cause the formation of warm or cold clouds, and cause the formation of fogs or smogs. 

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