EFFECTIVE CHARGE IN HEAVY-ION STOPPING IN CLASSICAL COLLISIONLESS PLASMAS

The Brandt-Kitagawa (B-K) model for the effective charge is revisited in order to account for the effect of trapped electrons on the energy loss of a slow ion moving in a classical and collisionless plasma. The electrons trapped in the potential created in the plasma by the proje ctile are treated as classically bound, and it is shown that their mai n effect is to reduce the effective charge state of the projectile. Th is effect is expected to be important when the strength of the perturb ation is non-negligible. (C) 1996 American Institute of Physics.