Physical Background of Ion Tracks

When energetic ions pass through solids, they dissipate their energy into the target. The resulting energy loss can be divided into two main regimes. The first is nuclear energy loss, which displaces atoms by elastic collisions between the ion and the nuclei. This process typically dominates for heavy ions with kinetic energies around and below 1 MeV. The second type of interaction, the electronic energy loss, occurs mainly between the ions and the electrons of the target and is the primary type of energy loss for ion energies above 10 MeV (so-called swift heavy ions). Additional energy losses can result from repulsive decay of excited states, track potential, and exciting of vibrational states in molecular solids. Radiation emitted from the particle and nuclear reactions can also dissipate energy, although this is only relevant at energies higher than those within the present work.