Spectroscopy and Atomic Physics

A short guide to spectroscopy is given with an emphasis on the elementary physics needed to understand and begin modeling the radiation emerging from astrophysical plasmas using the Sun as a guide, without bias toward a particular region of the Sun's atmosphere. The Sun is the astronomical body par excellence upon which our tools for exploring the universe have been most carefully developed. Observable solar plasmas span a broad range of conditions and consequently extremes of local thermodynamic equilibrium deep in the atmosphere, to extreme non-local thermodynamical equilibrium conditions in the corona and wind, including nonstatistical equilibrium conditions. For brevity, important subjects are omitted, notably non-Maxwellian electron distributions, line broadening, polarization, particle diffusion, and high-energy and collective phenomena of importance, at radio and hard x-ray wavelengths.