|This thesis shows the applicability of characteristic x-ray lines of mid-Z materials to investigate the properties of warm and dense plasmas. A many particle quantum-statistical approach to emission line profiles is outlined. Further, a perturbative description of line profiles in dense plasmas based on a self-consistent ion sphere model is presented in detail. Assuming LTE-conditions the plasma composition is calculated to characterize the created warm, dense plasmas. Further, spectral line profiles are synthesized, which are used to analyze recent laser-plasma-experiments.