ABSTRACT
When cells are irradiated, damage is produced primarily by ionization and free radicals. 1–3 Low LET radiations such as X- and γ-rays produce damage primarily by free radicals, whereas high LET radiations such as protons and α particles produce damage primarily by ionization. Ionized molecules are inactive. The energy released per ionization is about 33 eV, which is sufficient to break a chemical bond. For example, the energy associated with a C=C bond is only about 4.9 eV.
