Double scattering of rare gas ions from polycrystalline gold and copper

Energy spectra of Ne, Ar, and Kr backscattered from polycrystalline gold and copper have been measured at various scattering angles for primary energies (E0) in the range 4−30 keV. In these experiments, the heavier noble gas ions exhibit wider double−scattering shoulders than do the lighter noble gas ions as expected from kinematic considerations in case of Au. However, in case of Cu, the kinematic calculations give wider double−scattering shoulders for Ne+ than for Ar+ for ϑ?120°. The soulders depend upon ϑ and the ratio of the scattering yield at the shoulder to scattering yield at the main peak (I2/I1) decreases with increasing scattering angle ϑ in all systems studied in this paper, as expected from scattering cross−section considerations. However, for a given primary ion the ratio (I2/I1) is lower for gold than for copper at a given E0 and ϑ in these experiments contrary to what might be expected from scattering cross−section considerations.