Stopping Powers for Positrons and Electrons.

Abstract

Stopping cross sections for 20 keV positrons $({S}^{+})$ and electrons $({S}^{\ensuremath{-}})$ in a thin (61 $\ensuremath{\mu}\mathrm{g}/{\mathrm{cm}}^{2}$) Al target have been measured using an electrostatic analyzer. The results yield a ratio ${S}^{+}{/S}^{\ensuremath{-}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.15\ifmmode\pm\else\textpm\fi{}0.08$, in good agreement with the theoretically calculated value of 1.097. A marked dependence of the mean energy loss on an emergence angle has been observed for a thin target, and its origin is interpreted with the aid of Monte Carlo simulations.