A method is proposed to describe the impact-parameter dependence of energy loss in ion–atom collisions, ΔE(b), which is based on the local plasma frequency (LPF) approach. In this method, a linear response approach is combined with an explicit description of the energy loss to a free electron. This results in a general scheme of calculation where both the Barkas and Bloch corrections are presented. The calculated stopping cross-sections are in satisfactory agreement with the relevant experimental results. However, a serious disagreement was found by comparing the calculations with our recent results for energy losses in a thin gold foil, measured as a function of exit angle. This data reflect the impact-parameter dependence of energy loss in single ion–atom collisions. To explain this disagreement we address the problem of proper conversion of the impact parameter scale to the angle of deflection in single ion–atom collisions. It is argued that, due to specific quantum effects, the deflection angle for a given impact parameter depends significantly on the eventual energy loss. Under the conditions used in the experiment this can lead to an increase by a factor of two of the variation of the energy loss in a foil as a function of exit angle.

In this paper we present the results of measurement of the mean energy losses of 0.5 and 1 MeV/amu H+, D+, He++ and Li3+ ions transmitted through a gold foil of 24 nm thickness as a function of exit angle. The simultaneous manifestation of the higher-order corrections in energy loss and the non-equilibrium stopping in a thin foil has been observed.

Experimental results are presented on the exit angle dependence of the energy loss of H2+ and OH+ molecular ions transmitted through a thin gold target in the energy range of 50–200 keV. We have not found any noticeable angular dependence of the energy losses of H2+ ions in contrast to that for atomic ions. This result is in disagreement with a simple model of independent multiple scattering of the molecular fragments in the target.

The experimental data on the ejection angle dependence of the energy loss for He ions in a thin Au foil are discussed. The ion energies vary from 200 to 1000 keV. The results are analysed by the Monte Carlo method with allowance for the change of the charge distribution of the beam and the impact parameter dependence of the energy loss.

The experimental data on the emergence-angle dependence of 100–400 keV proton energy loss in thin Au foils are reanalysed taking into account the impact parameter dependence of energy loss and the foil thickness inhomogeneity. The results of computer simulations are presented for different theoretical models.

AbstractThe trajectories of 200 to 400 keV protons in 5 to 18 nm thick gold foils are simulated by means of Monte‐Carlo calculations. The impact‐parameter distributions of ion–atomic collisions at different emission angles are obtained. The impact‐parameter distributions of the mean energy transfered to the atom at given emission angles are calculated. The angular dependence of the mean energy loss is also calculated. By fitting the latter with experiment the impact‐parameter dependence of the energy transfer in a single collision is obtained.

The integral energy losses of H+, He+ and He2+ ions in thin gold foils at incident energies 40 to 500 keV have been determined experimentally. Pre-equilibrium stopping in the near-surface metal layers is found. Measurements of the energy loss straggling of protons in Au in the 9–45 nm thickness range are also been made. The straggling data are compard with the theories. The experimental angular dependence of the energy loss for protons are compared with the results of a Monte Carlo simulation of particle penetration through a foil.

In the measurement of energy loss Q within the collision parameter interval 0.02 Å ≲ b ≲ 0.4 Å a plateau of the curve of Q(b) at b ≲ 0.1 Å has been revealed which may be associated with the polarization of the electronic shell of a gold atom.

AbstractThe energy losses of protons scattered by atoms of gold are measured in the impact‐parameter range of 0.4 ≦ ϱ/αTF ≦ 4.0 where αTF is the Thomas‐Fermi radius. If the penetration depth of a proton into the electronic shell of an atom increases, there occurs a peculiar saturation of the stopping power at ϱ/αTF ≧ 1 at the levels (0.35 ± 0.05), (0.45 ± 0.05), and (0.52 ± 0.05) keV/ atom for incident beam energies of 100, 200, and 400 keV, respectively.

Experimental results concerning to discovery of coherent Coulomb excitation for the He+ ions passing through monocrystalline silver film are reported.