Energy-loss profiles of transmitted electrons incident on dielectric spheroids

We have obtained expressions for the differential energy-loss probability for electrons passing through small condensed-matter spheroids, parallel to the symmetry axis, at arbitrary impact parameter. The expressions, appropriate to oblate, prolate, and spherical targets, are a sum over all multipole contributions. They are expressed as functions of the local dielectric function ε{lunate}(ω), which is obtained from experimental bulk data as it is used here. Numerical evaluations have been carried out for silver and aluminum oblate and prolate targets, including multipole modes up to order (l, m) = (15, 15). The energy-loss functions have been averaged over impact parameter and presented graphically as functions of plasmon energy for a variety of parameters.