Introduction to Plasma and Plasma Diagnostics

Abstract

Abstract The nonequilibrium state of gas is introduced as a medium suitable for tailoring the surface properties of solid materials. Such a state of a molecular gas is characterized by a huge deviation of the excitation, dissociation, and/or ionization fractions from the Boltzmann distribution. The key reason for extremely high chemical reactivity of nonequilibrium gases even at a low temperature is a large concentration of gaseous particles of potential energy of several eV, usually 3–7 orders of magnitude larger than in a gas at thermal equilibrium close to room temperature. The production and consumption of gaseous particles is explained for technologically important gases. Some of the most common methods for measuring the concentration of most reactants are presented, such as electrical and catalytic probes as well as optical emission and absorption methods. Two of the most common states of nonequilibrium gas are introduced: glowing plasma and flowing afterglow.