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The semiclassical approximation with rectilinear trajectory is used to calculate the impactparameter dependence of electronic stopping for fast-proton collisions with gas and solid atoms. The effects arosen from electron shell rearrangement and dynamic screening of proton charge in a solid, on the electron stopping are studied for case of solid targets. The calculation results are compared with experimental data and with approximate calculations based on sum rules and local electron density approximation.Eine halbklassische Naherung mit gerader Trajektorie wird benutzt, um die Abhiingigkeit des StoBparameters der elektronischen Bremsung bei StoBen schneller Protonen mit Gas-und Festkorper-Atomen zu berechnen. Die aus der Umordnung und der dynamischen Abschirmung der Protonenladung in einem Festkorper herruhrenden Einfliisse auf die Elektronenbremsung werden im Fall der Festkorpertargets untersucht. Die berechneten Ergebnisse werden mit experimentellen Werten und mit Naherungsberechnungen verglichen, die auf der Summenregel und der Niiherung der lokalen Elektronendichte beruhen.

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The charge asymmetry effects in the dependence of electronic energy loss on impact parameter are studied theoretically. Allowance for some corrections to the calculations made in terms of the first-order perturbation theory is shown to result in a dependence of stopping on projectile charge sign. Corrections for binding-energy variations and for Coulomb deflection are allowed for in the case of stopping on inner shells of atoms. A correction for electron cloud polarization is allowed for in the case of valence electrons. Particular calculations are carried out in case of proton and antiproton stopping by Si atoms. The antiproton energy loss proves to exceed the proton energy loss in case of low values of impact parameters, and vice versa in case of high values of impact parameters. As the projectile velocity increases, all the corrections decrease, thereby resulting in that the impact parameter dependences of the proton and antiproton stoppings become in practice identical.

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