The 9th International Conference on Matter and Radiation at Extremes (ICMRE2026) ( ICMRE2026)

The modeling of plasmas requires a proper evaluation of specific quantities such as charge distribution and radiative properties. These quantities are in turn used to calculate transport properties, radiative losses or simply for spectroscopic diagnostics. The case of XFEL-created plasmas is even more specific since their state is driven by inner-shell photoionization and subsequent processes.

Calculating these quantities requires a preliminary calculation of the population distribution of the numerous atomic or ionic energy levels. Whether in natural or laboratory plasmas, this distribution is rarely given by the laws of thermodynamic equilibrium. Also, for heavy elements, enumerating and calculating these energy levels is a difficult task, not to mention the calculation of the collisional and radiative rates.
The difficulty lies in the fact that we are faced with situations of varying complexity, ranging from simple atomic configurations with almost closed shells to open-shell configurations with many electrons. This is the domain of complex atomic physics, where global properties emerge from these large sets of levels.

After presenting the differences between ‘high-density’ plasmas (e.g., laser-produced plasmas and solid-density XFEL-produced plasmas) and ‘low-density’ plasmas (e.g., plasmas in the core of tokamaks) in terms of collisional-radiative modeling, we will present the standard methods for approaching the atomic physics of heavy elements.

Next, we will go over some details concerning the calculation of the emissivity of high-Z plasmas and, in particular, the issue of completeness of the list of included atomic configurations. Concrete examples will be:
- the calculation of the emission of a heavy element irradiated by laser,
- the calculation of the ionisation and of the fluorescence of a heavy material
   irradiated by intense monochromatic X-ray radiation,
- the calculation of the ionisation and of the radiative emission (cooling factor) of
   tungThe modeling of plasmas requires a proper evaluation of specific quantities such as charge distribution and radiative properties. These quantities are in turn used to calculate transport properties, radiative losses or simply for spectroscopic diagnostics. The case of XFEL-created plasmas is even more specific since their state is driven by inner-shell photoionization and subsequent processes.

Calculating these quantities requires a preliminary calculation of the population distribution of the numerous atomic or ionic energy levels. Whether in natural or laboratory plasmas, this distribution is rarely given by the laws of thermodynamic equilibrium. Also, for heavy elements, enumerating and calculating these energy levels is a difficult task, not to mention the calculation of the collisional and radiative rates.
The difficulty lies in the fact that we are faced with situations of varying complexity, ranging from simple atomic configurations with almost closed shells to open-shell configurations with many electrons. This is the domain of complex atomic physics, where global properties emerge from these large sets of levels.

After presenting the differences between ‘high-density’ plasmas (e.g., laser-produced plasmas and solid-density XFEL-produced plasmas) and ‘low-density’ plasmas (e.g., plasmas in the core of tokamaks) in terms of collisional-radiative modeling, we will present the standard methods for approaching the atomic physics of heavy elements.

Next, we will go over some details concerning the calculation of the emissivity of high-Z plasmas and, in particular, the issue of completeness of the list of included atomic configurations. Concrete examples will be:
- the calculation of the emission of a heavy element irradiated by laser,
- the calculation of the ionisation and of the fluorescence of a heavy material
   irradiated by intense monochromatic X-ray radiation,
- the calculation of the ionisation and of the radiative emission (cooling factor) of
   tungsten.

Radiation,laser-produced-plasmas,XFEL Absorption spectrum,tokamak plasma,Atomic ph