Abstract
We have reported that selective induction of DNA strand breaks or base lesions can be partially realized using synchrotron monochromatic soft X-rays tuned in to particular energy of innershell ionization of DNA constituent atoms (Fujii et al., 2009). These evidences suggest that the monochromatic soft X-irradiation could be a powerful tool to reveal the process of the induction of complex DNA damage involved in biological effects such as cell killing or mutation induction. The ionized DNA molecule produced through innershell electron excitation and successive Auger relaxation is thought to be a precursor of DNA damage. When the energy of soft X-rays is close to the threshold of the innershell ionization, a produced photoelectron might be recaptured by the atom because the slow photoelectron could be overtaken by an Auger electron during the relaxation. This event causes a sharp decline of the Coulomb potential of the atom, and accordingly the photoelectron could be trapped by the atom again. In this study we semiclassically analyze the probability of the photoelectron recapture by DNA constituent atoms. Obtained results are discussed by comparison with our previous data of the unpaired electron showing significant change of the yield in energy regions of particular K-shell ionizations.
