Between Ultraviolet and Ionizing Radiation: Action Spectra for Cytotoxicity in the Vacuum-UV Region
Like UV-C, vacuum-UV is strongly absorbed by oxygen, so it does not reach the surface of the earth as in the case of UV-C. The vacuum-UV below 180 nm is strongly absorbed by water. This property is an important difference from UV-C. DNA as well as proteins show the first absorption peak in the vacuum-UV region around 190 nm attributable to the double bonds. For DNA such absorption is due to the π electron system of the bases. In the shorter wavelengths the absorption may be attributed largely to the sugar-phosphate moiety. The σ-σ* transition is generally thought to be responsible. Depending on the wavelength (or photon energy) the molecule may be promoted to the higher excited states (Kiseleva et al., 1975; Ito and Ito, 1986).
KeywordsSynchrotron Radiation Action Spectrum Radiation Research High Excited State Bacillus Subtilis Spore
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