The electronic properties of nanoscale-size fibers can be studied by electr
o energy-loss spectroscopy with electron beams that pass near the fiber but
do not penetrate it. we derive the formulas for the differential energy sp
ectrum assuming that the fiber can be treated as a dielectric cylinder. The
formula can be evaluated in closed form for a conducting wire; the spectru
m displays the surface plasmon and a low-energy peak associated with charge
-conduction modes that diverges inversely as the energy loss. [S016-1829(98
)05239-4].