Many-Body Theory of Atomic Structure and Processes

Abstract

All atomic structuremany-body perturbation theoryperturbation theoryperturbation theorydiagrammaticperturbation theorymany-bodymany-body perturbation theory (MBPT) atoms except hydrogen are many-body systems, in which the interelectron interaction plays an important or even decisive role. The aim of this chapter is to describe a consistent method for calculating the structure of atoms and the characteristics of different atomic processes, by applying perturbation theory to take into account the interelectron interaction. This method involves drawing a characteristic diagram based on the structure or process. This is then used to create an analytical expression to the lowest order in the interelectron interaction. Higher-order corrections are subsequently generated. This technique was invented about half a century ago in quantum electrodynamics by Feynman [23.1], Feynman diagram then modified and adjusted for multiparticle systems by a number of authors. Its application to atomic structure and atomic processes required further modifications, which were initiated at the end of the fifties (see, e.g., [23.2]) and later. The corresponding technique was successfully applied to the calculation of a wide variety of characteristics and processes in many papers and several review articles [23.3,4]. The increasing amount of experimental data available has led to improved accuracy for this technique, so that it can be applied to current problems considering not only atoms and ions, both positive and negative [23.5,6,7,8], but also molecules [23.9], clusters [23.10] and fullerenes. The elements of the diagrammatic technique, which form a convenient and simple “language”, are given together with the rules for creating “sentences” using basic “words”. A kind of “dictionary” helps to translate diagrammatic “sentences” into analytical expressions suitable for calculations. diagrammatic technique