Complex atom physics and radiative properties of hot dense plasmas

The understanding of ICF plasmas requires specific quantities such as average ionizations, emissivities and opacities, both for hydro-simulations and diagnostics. These quantities clearly involve the internal state of the ions. The well-known traditional few-electron atomic physics provides such satisfactory quantities for LTE and NLTE plasmas. On the other hand, calculations for high-Z plasmas containing open-shell complex ionic emitters have been attempted only recently. Because of the very large density of states in such ions, these calculations are based upon statistical considerations about the energy levels and the collisional-radiative rates rather than individual level or process accounting. Complex many-electron excited levels may have purely statistical, i.e. thermally induced, properties or intrinsic statistical properties due to the mixing of a large number of electron configurations. We review these statistical properties and we sum up the advances in complex atom physics which improve our capabilities to model radiative properties of hot dense plasmas.