Theory of electronic stopping of heavy ions in metals

The physical mechanisms responsible for the slowing down of energetic heavy ions by electrons in matter are discussed for various values of the ion velocity $v$. The quasiclassical theory of atomic collisions, which determines the energy loss for $v<Z_1^{1/3}v_0$, is presented ($Z_1$ is the atomic number of the ion; $v_0$ is the Bohr velocity). Oscillations of the stopping cross section with variation of the atomic numbers of the colliding particles are discussed. Elastic scattering (with respect to the incident ion) is analyzed; it turns out to be dominant for $Z_1^{1/3}v_0<v<Z_1^{2/3}v_0$. A number of semiempirical formulas for the electronic stopping cross section are discussed.