Dependence of the binary-encounter-peak energy on the projectile core

Abstract

The energy of the binary-encounter peak has been determined for 0.6 MeV/u O, F, Si, Ti, Cu, and Br ions colliding with H 2 targets. The projectiles all had the same charge qϭ7, while the atomic number Z of the projectiles ranged from 8 ͑almost totally ionized͒ to 35 ͑retaining 28 electrons͒. We observe that the binaryencounter-peak energy for fixed q increases as Z increases. This trend is opposite to that observed when Z is fixed and the charge q is varied, and it demonstrates that the binary-encounter-peak energy depends not only on the net projectile charge but on the projectile core as well. The experimental trend is qualitatively reproduced by an impulse approximation showing that this variation in the binary-encounter-peak energy may be attributed to the effect that the projectile core potential has on the electron elastic-scattering cross section.