Electronic energy loss of channeled ions : the giant Barkas effect

• Main Author: Araújo, Leandro Langie
• Publication Date: 2004
• Other Authors: Grande, Pedro Luis, Behar, Moni, Dias, Johnny Ferraz, Lifschitz, A.F., Arista, Nestor, Schiwietz, Gregor
• Format: Article
• Language: eng
• Source: Repositório Institucional da UFRGS
• Download full: http://hdl.handle.net/10183/104178
• topic: Berilio; Perda de energia de particulas; Impacto ion-superfície; Retroespalhamento rutherford; Silício

In this work we have measured the electronic energy loss of ⁹Be and ¹¹B ions for the ‹100› and ‹110› directions in Si as a function of the incident ion energy. The channeling measurements cover a wide energy range between 100 keV/amu and 1 MeV/amu. The Rutherford backscattering technique has been employed in the present experiments. An overall compilation of channeling energy loss values for several ions, including those for He, Li, and O measured previously, provides a clear picture of the Barkas contribution to the stopping power due to valence electrons in the present energy regime. A maximum of the relative contribution occurs for Be ions around 250 keV/amu while a saturation effect is observed for heavier ions. These results are interpreted in terms of a self-consistent nonlinear calculation based on the transport cross-section approach together with the unitary convolution approximation model, which describe the present data reasonably well at high projectile energies.