The energy-angle distribution of heavy particles penetrating solids: Experimental test of the Meyer-Klein-Wedell theory for Ne and Ar ions in carbon below 250 keV

Abstract

Meyer, Klein and Wedell have presented a theory of energy loss for heavy particles in solids. They assume that the electronic energy loss is, for one part, independent of the scattering angle (referring to term C e 0) and, for another part, dependent of the scattering angle (referring to term C e 2). In the present article we compare the MKW theory with experimental results obtained with neon ions (40–120 keV) and argon ions (40–240 keV) on thin carbon foils (4–15 μg/cm 2). Values of C e 0 and C e 2 were obtained in all cases. The MKW theory generally takes into account the principal phenomena observed during the study of the angular dependence of energy loss, i.e. a decreasing intensity with increasing emergence angle θ, and an increasing energy loss as a function of θ. In the energy distribution, the theory overestimates the number of ions having the highest energy losses; consequently it tends to overestimate half-widths, especially for energy spectra obtained at large angles. As far as the scattering angle dependence of the electronic energy loss is concerned, the validity of this basic hypothesis of the theory seems to be verified. The energy dependence of C e 0 seems to be similar to the energy dependence of the electronic energy loss as defined by Lindhard, Nielsen and Scharff.