Z2-oscillation systematics in the stopping of fission fragments

Abstract

The initial energies associated with fission fragments relate them to the medium velocity region of the order of v 0Z 1 2 3 in which most of the fragment energy is lost by “electronic” stopping. Theoretical models for electronic stopping in this velocity region are based on a statistical treatment of the atoms. Thus effects due to the electronic shell structure of the stopping medium cannot be reproduced and the resulting stopping parameters are monotonically dependent of Z 2. Range and energy loss determinations offission fragments reveal a pronounced non-monotonic dependence on Z 2. Based on these results an attempt is made to determine the systematics of the Z 2-oscillations in the stopping process of fission fragments. Systematic analysis of a large number of experimental results pointed out the dependence of the stopping process on several parameters characterizing both the fragment and the target. A spectral analysis was performed and typical periodicities in the Z 2-oscillations determined. After performing a sensitivity analysis a semiempirical modified LSS-expression for the calculation of fission fragment ranges was developed which includes the Z 2-oscillations. This expression has been evaluated and compared to the original LSS-theory by means of the Theory of Information.