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Energy-loss straggling of ions with v\ensuremath{\ll}${v}_{F}$ in an electron gas has been evaluated from phase shifts determined from nonlinear, density-functional calculations. These results differ markedly from those obtained from linear theory and show oscillations in straggling with increasing nuclear charge which can be correlated with the scattering properties of electrons at the Fermi level.

The real and imaginary parts of the complex refractive index, n(..omega..) = n(..omega..)+ik(..omega..), of arc-evaporated carbon films have been obtained over the range of photon energies h..omega.. from 0.5 to 62.0 eV. Values of k(..omega..) obtained from transmission measurements in this energy range were combined with values of k(..omega..) from the literature in the infrared and soft-x-ray regions. A Kramers-Kronig analysis then yielded the values of n(..omega..). The density of the arc-evaporated carbon films was found to be 1.90 +- 0.05 g cm/sup -3/ by the ''sink-float'' method, and their thicknesses were determined optically. A sum-rule calculation yielded the effective numbers of valence and core electrons to be 4.2 and 1.8, respectively. The experimental values determined for n(..omega..) have been used to estimate values of the inelastic mean free path ..lambda..(E) for electrons of energy E from 200 to 3000 eV in amorphous carbon. Good agreement is found between ..lambda..(E) and experimentally determined values of electron attenuation length L(E) from the literature.

An electron slowing-down flux spectrum has been measured for ..beta.. particles, delta rays, and secondaries generated by the ..beta.. decay of neutron-activated /sup 164/Dy uniformly distributed in Al/sub 2/O/sub 3/. The energy range covered in these measurements extends from 1.5 to 32 keV. Fairly good agreement with predictions of the Spencer-Fano theory is found for energies above 10 keV. The overall shape of the spectrum is similar to that found earlier for metals and semiconductors. A companion theoretical calculation has been carried out based on cross sections for ionization of electrons from the inner shells of Al and O derived from generalized oscillator strengths, and on cross sections for valence-band electrons derived from a model-insulator theory. The effect of Auger cascade electrons is also included in the numerical solution of the electron slowing-down cascade equation. The theoretical spectra are smaller than the experimental results by as much as a factor of 4 in the energy range from 50 to 2000 eV.

Theoretical calculations of the stopping power of the electron gas for slow ions, v${v}_{F}$, are reviewed. New results are presented for stopping power and effective charge based on nonlinear density-functional calculations. Extensive comparisons with available experimental data show that these new theoretical results are clearly superior to earlier calculations based on linear theory.

We consider in a classical formulation the interaction of a particle of charge ${Z}_{1}e$ incident at a given impact parameter with an electron bound isotropically and harmonically to the origin with a frequency $\ensuremath{\omega}$. Using a perturbation expansion that assumes that the displacement of the bound electron is small compared to the impact parameter, and integrating over the impact parameter from some minimum value to infinity, we are led to an expression for the stopping power. The leading term in this expansion is proportional to ${({Z}_{1}{e}^{2})}^{2}$ and is the usual result for this type of model, while the second term gives us the ${({Z}_{1}{e}^{2})}^{3}$ correction. The ${Z}_{1}^{3}$ correction for the Lenz-Jensen statistical model for the atom is presented. The predictions of this theory are in excellent agreement with available experimental data.

A simple expression is derived for estimating the contribution of surface losses to the stopping power of foils with plane parallel surfaces for normally incident nonrelativistic charged particles. Estimates are presented for electrons incident on foils of carbon and aluminum. The simple expression is modified in an approximate way to apply to the polycrystalline samples used in the work of Ichinokawa et al. and an estimate of the surface-loss contribution to the stopping power of polycrystalline graphite for electrons is given.

The mean excitation energy of polystyrene has been evaluated from the dielectric function for this organic solid. The result, $I=68.7$ eV, is in good agreement with a value in the literature obtained using the more conventional technique of extracting this parameter from stopping-power data.