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 projectile are treated as classically bound, and it is shown that their main effect is to reduce the effective charge state of the projectile. This effect is expected to be important when the strength of the perturbation is non-negligible. (C) 1996 American Institute of Physics.