Energy loss straggling of swift H+, He+, Li+ ions in solids

ABRIL I.; MONTANARI C. C.; MIRAGLIA J. E.; HEREDIA AVALOS S.; GARCIA MOLINA R.

Sevilla, España

Conferencia; 17th International Conference on Ion Beam Analysis; 2005

Local Organizers of the 17th International Conference on Ion Beam Analysis y Universidad de Sevilla

We present theoretical calculations of the energy loss straggling (W2) of  C, Al, Si and Cu for H+, He+ and Li+ in the range of intermediate and high energies (keV/u – MeV/u). The calculations have been done using the dielectric formalism, where the different equilibrium charge exhange of the projectile inside the target are considered as a function of the projectile energy. Two different models are used to describe the dielectric response of the target to the passage of the fast ion through it: MELF (Mermin Energy Loss Function) and LPA (Local Plasma Approximation). The MELF describes the target outer-electron excitations through a fitting to experimental data (in the optical limit) using a linear combination of Mermin-type [1] Energy Loss Function; the excitations of the target inner-shell electrons are taken into account adopting generalized oscillator strengths [2,3]. The LPA model uses the free electron gas to describe the target valence electrons, and the local density approximation to describe the corresponding inner-shell electrons by the Hartree Fock atomic wave function of each shell [4,5]. The results of the energy loss straggling obtained by these two independent models show a good agreement  with the available experimental data. The contribution to W2 due to each inner-shell of the target are calculated. We find that the energy loss straggling normalized with Z2 is almost independent of the ion atomic number Z, therefore the results for H+, He+ and Li+ in each target can be approximated by an universal curve.