Ionizing radiation fundamental considerations

Some progress is being made toward an understanding of the fundamental processes of radiation chemistry. The ultimate lethal action of ionizing radiation remains, however, as much as a mystery as the intimate organization of the cell itself. Two somewhat overlapping theories have been advanced, each of which enjoys considerable support. Although both theories have several features in common, they differ in that one is physical and the other is chemical in nature. 

ESR spectra can provide not only an unambiguous assignment of radicals, but also experimental information about their geometrical and electronic structures and reactions. CW-ESR spectroscopy combined with matrix isolation methods and ionizing radiation (y-ray, X-ray, etc.) is applied to the studies on reactive intermediate radicals including anionic and cationic species trapped in low temperature solid matrices. ESR parameters, especially hyperfine (hf) couplings, are predicted with considerable precision by recent advances in computational methods such as density functional theory (DFT), which affords a valuable bridge between experiment and theory at a most fundamental level. 

Such a one-photon ionization was performed with the use of photons of 10.5 eV/photon (=118 nm), that is, the ninth harmonics of the fundamental radiation of a Nd YAG laser [14]. At this photon energy a considerable number of ablated products can be one-photon ionized. 

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