Charge state dependence of channeled ion energy loss

The charge state dependence of channeled ion energy loss has been determined for a series of ions ranging from fluorine to chlorine along the $〈110〉$ direction in a silicon crystal. Energy losses for both bare ions and ions partially clothed with bound electrons at $\frac{E}{A}\cong 3$ MeV/amu have been measured. The energy-loss rate for bare ions follows a strict $Z_1^2$ scaling and agrees reasonably well with quantal perturbation calculations without the need for polarization or Bloch corrections. An explanation for this result is discussed. The clothed-ion energy losses appear to demonstrate screening effects that agree qualitatively with simple estimates. The angular dependence of the observed energy-loss effects is also presented.