Since photon energies are equal to the energy difference of the two levels of the line transition, the collection of photons composing a particular spectral line will have a broader energy distribution than it would have in the absence of microfields. Thus analysis of Stark line broadening is a valuable diagnostic tool in determining plasma densities. The more likely a photon is to be absorbed before leaving the plasma, the more opaque the plasma is. This effect can also result in further broadening of spectral lines by repeated absorption and reemission of photons. Radiation transport modeling is a way to assess how the photons work their way out through the plasma and how the observed spectra differ from those emitted by relatively transparent plasmas.
Fluid dynamics is a business of solving the general equations of motion for fluids.
Since a fluid is almost anything that will spread without a container, plasma obviously qualifies for the privilege to be called a fluid. For the sake of spectral diagnostics, hydro simulations can provide the plasma ion densities, which directly affect the density of emitted photons and hence spectral line intensities. As plasma becomes more rarified, overall radiation intensities decline. If for instance this plasma is intended to be a source of X-rays, a very energetic type of radiation second only to the gamma rays, a very powerful laser is required. However, in industrial applications such as thin layer deposition by laser ablation a much more gentle approach is needed.