The influence of physical state and chemical binding on the energy loss of Makrofol KG polycarbonate for helium ions

This work deals with the physical state and chemical bonds effects associated with the stopping powers determination in compound materials. II is primarily aimed to study the processes by which phase effects influence stopping power. The method adopted is based on our knowledge of the nature of the modifications created in the material leading to changes in the stopping power measurements. These chemical and physical modifications are created by helium beam irradiation at different doses and different energies, and the measurements are performed in Makrofol KG polycarbonate using helium ions in the MeV energy region. The experimental results are compared with the theoretical data obtained by adopting the Cores And Bonds formalism (CAB) for stopping power calculations and deviations from Bragg's predictions are estimated. The correlation between the IR spectra - describing the chemical bonds - and the stopping power results, points out three main findings: (i) significant deviations from predicted Bragg's calculations, (ii) competition of physical state and chemical bond effects with a chemical bond effect dominance around the maximum, and (iii) shift of stopping power maximum. (C) 1998 Elsevier Science B.V.