2. Fundamentals of low-temperature plasma theory

The basic theoretical concepts are explained ranging from the definition of a low-temperature plasma and physical processes are described in the various electric discharges used in plasma metallurgy. The respective collisional elementary processes, such as excitation and metastable states formation, dissociation, ionization and recombination are discussed in detail. Dissociation energies of two-atom molecules and ionization energies of most atoms are tabulated. All known ionization mechanisms are discussed and the Saha equation for thermal ionization is derived. Probabilities are compared of the individual types of recombination and the values are given of the recombination factor for different conditions. The plasma thermodynamic equilibrium is described in an electric discharge. The concept is introduced of the distribution function and several examples are shown. The basic thermodynamic quantities characterizing the state of the given system are expressed using the distribution function. (J.U.)