This chapter presents an overview of atomic processes which play important roles in plasma spectroscopy. Starting with the atomic wavefunction of hydrogen, the absorption oscillator strengths between discrete levels and their continuation to the continuum states (i.e., the photoionization cross section) are derived. The spontaneous transition probability and the radiative recombination rate coefficient follow. Excitation cross section by electron impact is discussed somewhat in detail. Several general features of cross sections are noted (e.g., the Bethe limit at high energy, different behaviours near the excitation threshold between neutral atoms and ions, and the resonance structure for ions). Continuation from the excitation cross section to the ionization cross section is noted. Three-body recombination, autoionization, dielectronic recombination, and satellite lines are also introduced.
Keywords: absorption oscillator strength, transition probability, radiative recombination, excitation cross section, Bethe limit, ionization cross section, three-body recombination, autoionization, dielectronic recombination, satellite lines
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