The Average Charge of Heavy Ions Stripped in Gases and Solids

A review is presented of extensive experimental data on average equilibrium charge states, q, of heavy ions penetrating through gaseous and solid media at energies up to 180 MeV. The usefulness of various semi-empirical methods to predict q is critically evaluated, and it is discussed to what extent these methods can be used for extrapolations into ranges where no measurements are available. Existing theoretical models are examined in detail and it is shown that the criterion by Bohr and Lamb is well suited to predict q with good accuracy in gaseous targets. A brief discussion is presented concerning the influence of the density of stripper targets on q.