The sputter-generation of negative ion beams: Analytical modeling

The secondary negative ion generation process is examined through the use of energy-dependent analytical models. Nonlinear least-squares fit parameters for the models are determined from fits to the experimental data of Yu. These models are used to illustrate the effect of the work function on the energy distributions of negative ions sputter-ejected from a polycrystalline molybdenum surface covered with fractional layers of cesium. Predictions are also made of the functional dependence of the probability for negative ion formation on cesium coverage. (orig.)