Precision measurement of the Sherman asymmetry function for electron scattering from gold

Measurements of the asymmetry (Sherman) function for gold as a function of foil thickness have been made in a ‘‘classical’’ electron double-scattering experiment. Results are presented for incident energies of 50 and 120 keV at scattering angles of 45°, 60°, 75°, 105°, 110°, 115°, 120°, 125°, and 130°. The measurements were highly reproducible owing to the consistent method we used for coping with spurious asymmetries. Absolute values of the asymmetry function were determined using two identical foils of 222 μg/${\mathrm{cm}}^2$ at 120 keV and 71 μg/${\mathrm{cm}}^2$ at 50 keV. An analysis of the uncertainties at these calibration points shows that they are below 0.3%. Extrapolation of the data to zero foil thickness and comparison with theory are critically discussed.