calculations of the mean frce paths and stopping powers of low energy electrons are performcd. In the computational model Lindhard's formalism of the dielectric response function for pair and plasmon excitation and the classical cross-section for ionization processes are used. Anomalously high mean free paths and small stopping powers in potassium are found. This behaviour which is connected with low electron concentration in the valence band is expected to hold for all alkali metals. For energies above 10 keV the calculated dE/dx agree well with values calculated from the Bethe-Bloch formula. A Monte-Carlo method is used for the calculation of the energy loss distribution of electrons passing through thin targets.It is noted that Blnnck-Leisegang's theory fails to render the energy straggling a t electron energies below 10 keV.Pur die Elemente C, Be, Mg, Al, Si, I<, Ge, Sb und Bi werden Berechnungen der mittleren freien Weglange und der Bremskraft fur niederenergetische Elektronen durchgefuhrt. Dabei werden im Berechnungsmodell der Lindhardsche Formalismus der dielektrischen Responsefunktion fur Paarund Plasmonanregung sowie der klassische Wirkungsquerschnitt fur die Ionisierungsprozesse angenommen. Anomal hohe mittlere freie Weglangen und geringc Bremskrafte werden in Kalium gefunden. Es wird angenommen, daB das Verhalten, das mit der niedrigen Elektronenkonzentration im Valenzband verknupft ist, fur alle Alkalimetalle gultig ist. Fur Energien oberhalb 10 keV stimmen die berechneten dE/dr gut mit Werten iiberein, die aus der Bethe-Bloch-Formel berechnet werden. Eine Monte-Carlo-Rlethode wird zur Berechnung der Energieverlustverteilung der Elektronen, die diinne Targets passieren, benutzt. E s wird gezeigt, daB die Theorie von Blunck-Leisegang die Energiestreuung bei Elektronenenergien unterhalb 10 keV nicht erkliiren kann.

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The Monte-Carlo model of individual collisions is applied for low energy electron transport calculations. The applicability of this model is analyzed in detail with theoretically calculated cross sections. Some semiempirical relations for the most important characteristics of the transmission, backscattering, and absorbed energy distributions for C, Mg, Al, Si, Ge, Bi solid targets are IntroductionInvestigations of the interaction of a low-energy electron flux with matter are of great interest for electronics, laser technique, semiconductor technology and others. Intense experimental [l to 81 and theoretical [9 to 121 studies of the processes of electron-solid target interaction have been undertaken during the last few decades. The theoretical study of electron transport processes has been developed in several directions: 1. solving the kinetic transport equation [9, lo]; 2. application of the Monte-Car10 technique [ l l , 121: 3. creation of phenomenological models.The first direction involves the derivation of analytical expressions for differential fluxes and their functionals. However, in practice, due to the complicated character of the elementary processes of elastic and inelastic electron scattering in solids it reduces to numerical quadratures of the transport equation. The Monte-Carlo method wit.h its simple computational algorithm allows to get all functionals of the transmitted, reflected, and absorbed fluxes with an accuracy of a few per cent for any geometrical target configuration and any cross-section of the elementary processes.This paper presents the results of this method for obtaining various characteristics of electron beams interacting with solids.

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In vitro experiments show significant reduction in the survival fraction of cells under irradiation treatments assisted with high-Z nanoparticles (NPs). In order to predict the radiosensitization effect of NPs, a modification of the local effect model (LEM), in which the energy deposition from NPs is assessed by Monte Carlo (MC) radiation transport codes, has been employed in the past. In this work, a combined framework that splits the consideration of the radiosensitization effect into two steps is proposed. The first step is the evaluation of the radial dose distribution (RDD) around a single NP ionized by a photon beam with given energy spectrum using MC simulation. Thereafter, an analytical approach based of the LEM and the calculated RDD is used for evaluation of the average dose and the average number of lethal lesions in a cell target due to a set of ionized NPs. The explicit expressions were derived for the case of a spherical cell target and the RDD describing by the power law function. RDDs around gold NPs (GNPs) of different radii were simulated using the MC technique and fitted by a power law function. The fitted RDD and the derived expressions were applied for calculation of the survival curves and relative biological effectiveness of a spherical MDA-MB-231 cell loaded with GNPs and irradiated with monoenergetic photons of 10–150 keV. The proposed framework provides a practical alternative to time-consuming MC simulations, enabling the assessment of the response of cell cultures to an irradiation treatment assisted with NPs for a wide variety of cell geometries, NP distributions and irradiation schemes.