Two-channel approach to the average retarding force of metals for slow singly ionized projectiles

Based on the fundamental momentum-transfer theorem [Phys. Rev. Lett. 15, 11 (1965)] a novel contribution to the retarding force of metallic systems for slow intruders is derived. This contribution is associated with sudden charge-changing cycles during the path of projectiles. The sum of the novel and the well-known conventional contributions, both expressed in terms of scattering phase shifts, are used to discuss experimental data obtained for different targets. It is found that our two-channel modeling, with two nonlinear channels, improves the agreement between several data and theory and thus, as predictive modeling, can contribute to the desired convergence between experimental and theoretical attempts on the retarding force.