Abstract
An interpolation formula for ionization (and excitation) of ions is proposed, which holds for the whole energy range of the colliding electrons. With the aid of this formula a time constant is computed and discussed characterizing the time scale with which the ionization equilibrium of heavier ions is established. Elewert’s ionization formula is generalized for small parameters s=χn/k T (χn=ionization energy). The radiation of impurities namely free —free, free—bound, and excitation radiation are computed and discussed for such a plasma. The interaction of the radiation with the plasma is neglected.