ENERGY-DISTRIBUTION OF LIQUID-METAL IONS NORMAL TO THE EMISSION SURFACE

The analytic distribution for the ions just emitted at the protrusion of the apex surface is obtained from field evaporation theory. The dis tribution profiles are a kind of shifted exponential asymmetry functio n having a sharp increase and exponential decay. These asymmetric prof iles are seen in the experiments of many authors. Although the full-wi dth half-maximum energy is about thermal energy (similar to kT), which is not comparable to the values of similar to eV measured by an energ y analyzer, the variation of the energy spread with the emission curre nt and the temperature can be investigated in the energy-distribution profiles. However, the value of the energy spread at the emission elec trode may increase as the ions are passing through the extractor becau se the energy distribution is broadened during beam propagation betwee n two electrodes.