Charge equilibration and electronic stopping for self-irradiated silicon

Charged energetic particle radiation has technological interest in applications including nuclear energy, outer space, medicine, and fundamental research. As a result of irradiation, damage, including point defects, forms and ultimately determines the material properties. Therefore, understanding the underlying interactions between charged particles and a material from first principles is important. Recently, we investigated heavy (silicon) projectiles traversing crystalline bulk silicon and found a pronounced dependence of electronic stopping on the initial projectile charge state. This effect was not observed for light projectiles impacting metal or semiconductor targets. To understand this, we analyze the dynamics of charge equilibration, influence of the impact parameter, and contributions of core and valence electrons to electronic stopping. We observe that the equilibrium charge state of the Si projectile depends on the impact parameter and ultimately dominates electronic stopping. We also predict that this effect should be observable experimentally for large-Z projectiles of different charge, on hyper-channeling trajectories, e.g. in a thin film.