The Energy Loss Straggling of low Z Ions in Solids and Gases

摘要

We present a study on the energy loss straggling of low Z ions (H up to B) in different solid (Al, Ti, Cu, Zn, Ge, Au) and gaseous targets (Ne, Ar, Kr, Xe). This work includes on one side, a critical analysis of the available experimental data and possible non-statistical (rugosity and inhomogeneity) contributions. On the other side, theoretical calculations performed by using the shell-wise local plasma approximation and the comparison of these results with the experimental data and with other theoretical curves available in the literature. We find that for the ions here considered, the square of the energy loss straggling normalized to Bohr limit is independent of the ion nuclear charge and of the ion charge state, in the case of electrons bound to the projectile. This shows a clear Z~2 dependence of the square energy loss straggling, with Z being the ion nuclear charge. The tendency to Bohr limit at high energies, and the inconvenience of using Yang formula (Q. Yang etal, Nucl. Instrum. Meth. Phys. Res B 61, 149-155 (1991)) are also mentioned. The bases for the future development of a general formula for the energy loss straggling are introduced.