Proton irradiation effect on hydrogen bond in material and biological systems

After proton beam irradiation, we found the magnetic structure change in graphite. This work has been published as 'Electron Spin Resonance of Proton-Irradiated Graphite' (PHYSICAL REVIEW LETTERS, 97, 137206). And this work has been selected as 'the most prominent 10 science news 2006 in Korea'. When the proton beam was irradiated on KDP single crystal with fluence of 1015 ions/cm3, and the range of irradiation energy: 300 kev ∼ 2.0 MeV, the dielectric constant and the capacitance has increased as irradiation energy was increased. This means the distance of the separation of equilibrium in hydrogen bond has enlarged by proton beam irradiation. Using X-Ray diffraction pattern measurement, we found that the lattice constant was decreased after the irradiation and the activation energy has decreased from 0.42 eV to 0.28 eV by 1H NMR spin-lattice relaxation time measurement. This means that after proton beam irradiation, the hydrogen ions in KDP are more activated. We also found similar change in hydrogen bond after proton beam irradiation by dielectric constant measurement. These results have been published as 'Structural and proton-dynamical effects in a proton-irradiated KH2PO4 single crystal' ( PRB 73, 134114. (2006) ). In order to perform finer analysis for hydrogen bonds in KDP single crystal, we focused on the domain freezing effect near the phase transition temperature of KDP. Finally we set up Debye relaxation for domain wall motion, Cole-Cole and Cole-Davison models. We also developed proton beam resist materials for lithography using proton beam irradiation and nano proton-beam writing based technology