Atomic Population Kinetics

Abstract

This chapter introduces to the theory of atomic population kinetics and radiative properties of atomic and ionic bound–bound transitions. Particular attention is devoted to the general problems related to an extremely large number of kinetic equations describing populations of Rydberg and autoionization atomic states in plasmas. A new method of reduced kinetics for autoionizing states, the virtual contour shape kinetic theory (VCSKT), is described in details. The method is based on a probability method for LTE- and non-LTE-level populations that allows effective level reduction while preserving all detailed atomic transitions. The representation employs effective relaxation constants that have analytical solutions. The comparison with detailed level-by-level calculations demonstrates high accuracy and large efficiency of the VCSKT. In order to solve many states’ kinetic problems for Rydberg atomic states, the quasi-classical representation of the system of kinetic equations is proposed. In particular, the two-dimensional radiative cascades between Rydberg atomic states are described by a purely classical motion of atomic electrons in a Coulomb field that lose energy and orbital momentum. The general collisional-radiative model for large principal quantum numbers is reduced to an effective diffusion in two-dimensional energy and orbital momentum space. The results of these new kinetic models are compared with standard collisional-radiative kinetics demonstrating an important reduction of computer times, the possibility to obtain scaling relations and to independently study the precision of complex quantum calculations for these many level kinetic problems.