Momentum transfer cross sections and the Z1 oscillations in stopping power

Heavy ions moving at low velocity along channelling directions in crystals are considered to lose energy by transferring momentum to target electrons which scatter elastically from them. In a model system of an atom moving through an electron gas, the stopping power is shown to be proportional to the electron momentum transfer cross section. The variation of this cross section throughout the periodic table corresponds closely to the observed variation of stopping power for channelled ions.