ABSTRACT
Bohr’s early investigations were entirely classical; but after quantum mechanics became fully established and Bethe and Bloch obtained good quantum mechanical expressions, Bohr presented a lengthy review in 1948, concentrating on classical concepts but including a discussion of the Bethe formula. Over the years, there have been quite a number of reviews of the theory and quite a few tabulations of numerical stopping powers. Like electrons, heavy ions may interact with target atomic electrons or with atomic nuclei. The ion–nucleus collision is primarily elastic Coulomb scattering. The basic expression for the energy loss rate of an ion passing through matter is known as the Bethe–Bloch equation. In collisions with target atoms, the projectile may lose one or more or all electrons. A feature of ion stopping power noticed early in the twentieth century is that their stopping power is the greatest, and reaches a local peak, near the end oftheir range.
