Generalized Collisional Radiative Model Using Screened Hydrogenic Levels

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Collisional-radiative (CR) models are used to obtain atomic level population distributions and radiative properties in plasmas. These quantities are used to help design experiments, to provide data for radiative energy transport in radiation-hydrodynamic simulations, and to diagnose laboratory and astrophysical plasmas whose conditions are difficult to or impossible to directly measure. CR models are constructed by coupling a set of electronic energy levels with spontaneous, collisional, and radiation-driven transitions . Since the number of atomic levels and transitions necessary to build a CR model can be prohibitively high, especially for many-electron ions, models are often customized for specific applications by tailoring the structure based on expected plasma conditions. On the other hand, there remains a need for models that are general enough to predict charge state distributions and radiative properties with reasonable accuracy for plasmas over a wide range of plasma conditions. Such generalized models are especially useful for design simulations, which access a wide range of conditions, and for preliminary analysis of spectroscopic data. This chapter describes a class of generalized CR models based on screened-hydrogenic atomic levels and rates. These models have been applied to a wide variety of applications and have demonstrated reliable performance over a wide range of plasma conditions, from the low-density coronal limit to local thermodynamic equilibrium.