Atomic Process in Plasmas

Abstract

AbstractWhen a high-intensity laser is irradiated onto a solid gold (Z = 79), half of the electrons is partially ionized. The multi-electron structure of such ions is not obvious. Quantum mechanics of multi-electron systems and calculations of ionization statistics are required. In this chapter, the electrons in the ion are approximated to be bound in a spherically symmetric mean field, and the isolated atom is studied.The Hartree-Hock (HF) equation, which accurately describes atoms in many-electron systems, can be solved, but it is a daunting task. For this purpose, simple but error-prone approximations have been used, such as the HULLAC and OPAL codes, which use the para-potential method instead of a rigorous description of the HF. It is an intuitive and easy-to-understand approximation.Once the quantum state of the bound electrons can be calculated, the statistical distribution of ionization can be obtained by solving the Saha equation for thermal equilibrium. The threshold of ionization (continuum lowering) is determined. The calculation of such an ionic structure is presented. Due to the high temperature of the plasma, interaction with thermal radiation and free electrons cause excitation, ionization, and the reverse process. Calculations of these processes will be presented.Applications of the rate equations will be explained. In the recently introduced X-ray laser (XFEL) heating, free electrons are also non-equilibrium (non-Maxwellian). This chapter begins with a review of hydrogen and helium atoms, and then introduces the topics of atomic physics and processes from the laboratory to the universe.