Energy-loss straggling of swift heavy ions in an electron gas

Classical methods are employed to characterize the energy-loss straggling for swift, heavy ions interacting with independent electrons of a degenerate electron gas. The method of Bohr on the statistical aspects of the energy-loss process is used, and the electron-intruder collision is modeled via a finite-range screened Coulomb potential energy. The transport fluctuation cross section is calculated analytically within the framework of the impact-parameter method. Comparison with straggling data obtained for carbon foils with singly ionized carbon ions is made, and a good agreement is found in the validity range of the applied classical methods.

Figure 1

Cross sections and straggling ratios, as a function of $Z$. The screening parameter is $R=3$, and the velocity is $v=k=3$, both in atomic units (a.u.). Solid curves are based on the classical method, while the open circles refer to the wave-mechanical calculations.

Figure 2

Straggling ratios, $\Omega ∕{\Omega }_B$, as a function of the ion energy. The screening parameter is $R=1.23$ in atomic units. The experimental points are denoted by solid circles, the solid curve is based on the classical approximation, and open circles refer to the wave-mechanical results.