Quantum theory of spectral line broadening by plasma oscillations

Spectral line broadening models often make a number of simplifying approximations. The effects of longitudinal plasma oscillations, otherwise known as Langmuir waves, are often ignored or included in a dynamic screening function. We include the effects of plasma oscillations within the foundational work of Bohm and Pines [D. Bohm and D. Pines, Phys. Rev. 82, 625 (1951)0031-899X10.1103/PhysRev.82.625, D. Pines and D. Bohm, Phys. Rev. 85, 338 (1952)0031-899X10.1103/PhysRev.85.338, D. Bohm and D. Pines, Phys. Rev. 92, 609 (1953)0031-899X10.1103/PhysRev.92.609, and D. Pines, Phys. Rev. 92, 626 (1953)0031-899X10.1103/PhysRev.92.626]. Our line broadening model, therefore, treats the plasma oscillations quantum mechanically, calculating how a radiating atom interacts with plasmons. We investigate the impact that the plasmons have on the line shape when the plasmons are in thermal equilibrium and when the plasmons are excited. Various aspects of the latter include the impact of the intensity-generating higher-order harmonics, and how the spectrum changes as a function of the intensity distribution of the plasmons. Lastly, we also explore cases of a radiator with forbidden components, such as in He-like structure, as well as a highly charged radiator and how the plasma polarization affects the spectral behavior of the plasmons.