Dissociation Path Competition of Radiolysis-Ionization induced Molecule Damage under Electron Beam Illumination

The radiolysis ionization under electron beam illumination induces dissociation and damage of organic and biological molecules, which causes the inability of transmission electron microscopy (TEM) in imaging the related materials. We developed a procedure based on the real-time time-dependent density functional theory (rt-TDDFT) for simulating the radiolysis damage processes of molecules, which can describe the ionization cross sections of electronic states and the fast dissociation processes caused by the hot carrier cooling and the Auger decay on deep levels. For the radiolysis damage of C₂H₆O₂, our simulation showed unexpectedly that there is strong competition among three different dissociation paths, including the fast dissociation caused by the hot carrier nonadiabatic cooling; the fast dissociation caused by Auger decay induced double ionization and Coulomb explosion; the slow dissociation caused by the increased kinetic energy. As the energy of incident electron beam changes, the time scales of these dissociation paths and their prudency in causing the molecule damage change significantly. These results explained the measured mass spectra of the C₂H₆O₂ dissociation fragments, and revealed the dissociation paths in the TEM imaging of organic and biological materials.