Diffusion-transport cross section and stopping power of swift heavy ions

Abstract

The stopping power of swift heavy ions in both cold and plasma targets is expressed by a single formula from which the standard classical or quantum results are retrieved as specific limits. It is based on a modified Bloch correction term devoted to correctly describe the close collisions contribution to the energy-loss process. This correction term is deduced from the convergent kinetic theory (CKT) derived by Gould and DeWitt for calculating transport coefficients in dense plasmas. The CKT is adapted to neutral targets by using the scaling properties of Yukawa potentials demonstrated by Lindhard. The resulting CKLT stopping expression can be applied to partially ionized heavy ions with a non-Coulomb electron-ion interaction potential. The differences between the CKLT and standard stopping models are investigated in the binary approximation, where the CKLT formula yields the exact result. The usefulness of the CKLT procedure in stopping power applications is then demonstrated using the spherical harmonic oscillator as a target model. The validity domain of the CKLT is analyzed by comparing the results derived by adding the close collision correction term either to the Born I result or to a classical calculation. The classical result is obtained by following during a collision, the time evolution of the Wigner distribution.