Pressure ionization of atoms in plasmas

It is shown that the main physical reason leading to the ionization of the atoms in plasmas at high densities (pressures) is the Pauli exclusion principle for the electrons which is responsible for the big spatial extension of atoms. Especially for the example of hydrogen the theory is extended to include those effects. Spatial and energetic variants for the definition of the species atom are discussed. The quantum theory of bound states in plasmas is compared with the classical theory of ion association in electrolytes. (author)