Multiple scattering calculations on ions passing through thin amorphous foils

This paper describes experimental studies of the multiple scattering of a number of different ions with $1l{Z}_{1}l18$ and 500 keV incident energy, transmitted through thin films of Se, Pd, Ag, Te, ${\mathrm{Ta}}_{2}$${\mathrm{O}}_{5}$, and Bi, and foils consisting of a mixture of C and Au atoms. We found that the targets fell into two groups with respect to structure. The first group, in which the targets were amorphous or had very small crystallites, showed multiple-scattering distributions of heavy ions, in agreement with current theory. In the second group, where the targets had grain sizes larger than approximately 100 \AA{}, the distributions were consistently narrower than those predicted theoretically. Possible mechanisms responsible for the deviations were investigated.

Multiple scattering of heavy ions of keV energies transmitted through thin films

The potential energy functions between ions and atoms in collision were calculated using equations developed by Firsov and differential cross sections measures by Fuls, et al., and Jones, et al. The equations assumed classical, quasi-adiabatic conditfons and required differential cross sections measured over a wide range of scattering angles at one incident energy. The ion-atom combinations used were Ar/sup +/ on Ar, Ne/sup +/ on Ar, Ne/sup +/ on Ne, He/sup +/ on Ar, He/sup +/ on Ne, and He/sup +/ on He with incident energies of 25, 50, and 100 kev. The potential energies calculated were positive, were in a range from one to sixty thousand electron volts, and corresponded to atomic separations from 0.05 to 0.4 angstroms. The incident ions penetrated inside the electronic shells of the target atoms. Experimental errors will not permit the detection of velocity dependent or inelastic proc esses but the resultant potential energies were found to fit very well a function derived by Firsov from a statistical model. An exponentially screened Coulomb potential energy function did not fit quite as well, but both these functions were within the accuracy of the experimental data and either could be used to calculate the forces betweenmore » the ion and the atom in this energy range.« less

ION-ATOM POTENTIAL ENERGY FUNCTIONS OBTAINED FROM kev SCATTERING DATA

Some new experimental results are reported on multiple scattering of H-, He-, Li-, Ne-, Ar-, and Kr-ions in the energy range between 100 and 1000 keV. The scattering foils of carbon and germanium, with thicknesses between 300 and 1100 A, were self-supporting. The results of the scattering measurements werecompared with the theories of Meyer and Moliere, respectively. Absolute deviations from the theory are always less than 20 per cent for the half-widths. A substantially better correspondence between theory and experiment is achieved by fitting the screening parameter of the interaction potential.

P. Krygel

Papers

The determination of screening parameters from measurements of multiple scattering of low-energy heavy particles