If one consider ions as “balls” with momentum p=mv the nuclear stopping is provided by velocity interaction. If the rate of energy loss is plotted as a function of ion energy, it can be seen that the loss increases linearly at low energy because the ion velocity is smaller, the loss reaches maximum and decreases at higher energy because the higher velocity makes ion move too quickly to interact. S_n (E) increases with ion mass (p=mv) and if ions are light (e.g. Boron), its energy loss/unit length () is much lower.

S_e (E) is energy loss per unit length due to electronic stopping. Drag force caused by charged ion in "sea" of electrons (non-local electronic stopping).