The 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 a t different emission angles are obtained. The impact-parameter distributions of the mean energy transfered to the atom a t 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. I n connection with many new applications of ion-beam methods in science and technology it has become necessary to describe the passage of light ions through matter at greater length. Specifically, this concerns the contribution provided by a single collision in the multiple scattering on target atoms to the total deviation from the initial direction and to the total energy losses of particles emitted from the target a t a given angle 8. The contribution of collisions with different impact parameters p t o the resultant deviation 8 and the p-dependence of the energy transfer q in a single collision have not yet been studied well. The theoretical estimates of the dependence q(p) [ l , 21 are contradictory and direct measurements are not available.In [3 to 71 the dependence of the energy losses AE on the emission angle 8 a t different initial conditions was experimentally studied and some tentative conclusions about the dependence q ( p ) were made. In the present paper we attempt to analyze our previous results [4] by means of a computer simulation of particle trajectories in the target. The purpose of the calculations was to determine the contribution of the collisions with differing impact parameters p to the total deviation of a particle (at an angle 8) and to elucidate the possibility of extracting the q ( p ) data from the experimental results obtained a t finite target thickness. The calculations were made for the passage of protons with energy E = 200 and 400 keV through the 5, 9, and 1 8 n m thick gold foils. The impact-parameter ( p ) l) 119899 Moscow, USSR.
K79At present energy loss straggling of ions with low energies in solids receives an increasing interest in connection with ion implantation, ion detection, and analysis techniques with ion beams. In this paper measurements are reported which were carried out with protons and helium ions in a thin carbon target. The energy of the ions was ranging from 40 t o 500 keV. In the lower part of this energy range charge state fluctuations of the ions are typical, whereas the projectiles a r e completely ionized in the upper energy range. In this energy range the electronic stopping cross sections of protons attain their maximum.The measurements at energies above 100 keV were performed with the cascade generator KG-500 at the Moscow State University, the measurements below 100 keV were carried out with an ion accelerator at the Humboldt-University in Berlin.A self-supporting foil, which was prepared by the Bradley method in a vacuum T o r r was used a s target. The thickness of the target was determined to be of -12 andThe ion beam was analysed in the foreward direction with regard to i t s energy distribution. The angular aperture was 0.8' in both experimental arrangements.A silicon surface b a r r i e r detector with a resolving power of 9 to 9.5 keV for protons and 12.5 to 15 keV for helium ions was used a s energy analyzer in the upper range.In the lower range we made use of an electrostatic energy analzyer (cylindrical condenser) with a resolving power 6 E/E = 7 o/OO.The energy distributions were recorded for both the incident ions and the ions which passed through the foil. All the distributions were approximated by Gaussian
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