Kinetic Theory

Abstract

Kinetic theory provides the basis for macroscopic state variables, such as pressure and temperature, by developing a microscopic picture of particles with kinetic energy, momentum, and, moreover, internal degrees of freedom. Thus, it follows an atomistic model. To treat a system of typically 10²³ particles, kinetic theory introduces the concept of probability and statistics into science. (The probability concept is, moreover, key to the description of quantum mechanics. However, we must clearly distinguish between thermodynamic probability introduced by Ludwig Boltzmann and quantum mechanical probability resulting from Max Born’s interpretation of the wave function (see Sect. 9.1.2 on page 216).) Among the probability density functions, the Maxwell-Boltzmann distribution for the particle velocity is the most prominent, and we deal with it in several problems. The characteristics of a molecular beam leaving an effusion cell, in addition to film growth, are further examples that demonstrate the practical use of kinetic theory.