Distribution of the radiative lifetimes over the excited states of atoms and ions

The empirical regularities in the variation of the radiative lifetimes $\tau_k$ of excited states of atoms are reviewed. A quasiclassical theory of radiation damping processes is constructed. The formalism of quantization of the natural width $A_k=\tau_k^{-1}$ of the excited states of atoms and ions is presented. The question of how to describe the serial dependences for a perturbed series is investigated. It is demonstrated that the radiation emission of atomic systems is sharply reduced when the classical factors in the radiative processes are suppressed. Schemes are proposed for extrapolating lifetimes from the lower terms of a series to the upper Rydberg states, right up to the continuum. Recommended values of $\tau_k$ for group I, II, and VIII atoms are given in a form that is convenient for inclusion in a computerized data base.