STOPPING POWERS AND BACKSCATTERED CHARGE FRACTIONS FOR 20–150 keV H+ AND He+ ON GOLD**Research supported by the Natural Sciences and Engineering Research Council of Canada.

The stopping powers for 20–150 keV H+ and He+ in Au have been measured by the backscattering technique. Thin Au layers (~10nm) on Be substrates were used. The Au thickness (N Δt) was determined using Rutherford backscattering with 1 MeV He and a well calibrated detector geometry. An electrostatic analyser was used to determine the energy loss of the keV ions in penetrating the Au layer. This energy loss measurement was corrected for the neutral component of the backscattered ions using the measured charged fraction and its energy dependence with a thin window solid state detector. The estimated accuracy of the results is <5% and they are compared to previous published data and interpolated best estimates.