Computer Simulation of a Molecular Stopping‐Power Problem

Abstract

A high‐speed computer is used to calculate the trajectory of a fast ``test'' particle injected into a two‐dimensional system of interacting point particles. All particles interact along lines of centers according to a repulsive inverse‐power force law. The evolution of the test‐particle velocity and energy averaged over many machine calculated trajectories is compared with a statistical theory based on binary collisions. In the case of an inverse‐cube force law explicit theoretical results are obtained and show excellent agreement with the machine calculations. A combined relaxation‐time—Fokker—Planck kinetic equation for the test‐particle distribution function is discussed; this equation includes the effects of both strong and weak collisions. For the inverse‐cube force law this equation is approximately solved for the energy distribution function and exhibits the principal features of the machine calculated energy distribution.