Valence structure effects in the stopping of swift ions

The valence structure of a material may affect the stopping of swift charged particles primarily via Z2 structure, atom-molecule differences, gas-solid differences and metal-insulator differences. These material effects have a common physical origin and can therefore be considered from a unified point of view. Theoretical arguments focus on the effect of binding and orbital motion of the target electrons as well as projectile screening and Barkas-Andersen effect. Generally, valence effects depend on the atomic number, charge state and velocity of the projectile. Reference is made to recent calculations on the basis of binary stopping theory as well as experimental findings.