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tokens: of C 6+ . However, the Ecker–Kröll model ( Ecker Kröll 1963 ) predicts a much higher population fraction of C 6+ compared with that obtained using our model. This differs from the conclusion drawn using the solid-density Mg, Al, and Si plasma ( Ciricosta et al. 2012 , 2016 ; Zeng et al. 2020 ), where the IPDs determined by the Ecker–Kröll model were in much better agreement with the experimental results than those of the SP model. Fig. 4. Charge-state distribution of C plasma as a function of the plasma temperature at mass densities of 2.25 g cm −3 ( a ), 3.75 g cm −3 ( b ), and 5.0 g cm −3 ( c ). Our results are compared with the Debye–Hückel (DH; Debye Hückel 1923 ), Stewart–Pyatt (SP; Stewart Pyatt 1966 ), ion-sphere (IS; Rozsnyai 1972 ), and Ecker–Kröll (EK; Ecker Kröll 1963 ) analytical models. We obtained the best agreement with the Ecker–Kröll model ( Ecker Kröll 1963 ) for the CSDs at a mass density of 3.75 g cm −3 . The SP ( Stewart Pyatt 1966 ), IS ( Rozsnyai 1972 ), and Debye-Hückel ( Debye Hückel 1923 ) models predicted a higher population fraction for C 5+ and a lower fraction for C 6+ than those predicted by our model and the Ecker–Kröll model. With the increasing mass density up to 5.0 g cm −3 , our theoretical IPDs and those of the IS and Ecker–Kröll models exhibited good agreement. The SP and Debye–Hückel models predicted a higher population fraction for C 5+ and a lower fraction for C 6+ . The aforementioned results can be seen in Fig. 5 , which shows the average ionization degree of C plasma as a function of the plasma temperature (100–500 eV) at mass densities of 2.25, 3.75, and 5.0 g cm −3 . Our predicted average ionization degree is consistent with those of the Ecker–Kröll model ( Ecker Kröll 1963 ) at a density of 3.75 g cm −3 and the IS and Ecker–Kröll models at a density of 5.0 g cm −3 , which is completely in accordance with the features observed with respect to CSDs (Fig. 4 ). Fig. 5. Average ionization degree of C plasma as a function of plasma temperature at mass densities of 2.25 g cm −3 ( a ), 3.75 g cm −3 ( b ), and 5.0 g cm −3 ( c ). Our results are compared with the Debye–Hückel ( Debye Hückel 1923 ), Stewart–Pyatt ( Stewart Pyatt 1966 ), ion-sphere ( Rozsnyai 1972 ), and Ecker–Kröll ( Ecker Kröll 1963 ) analytical models. 3.3. Analysis and explanation of a recent experiment Here, we verify the validity of our proposed model of screening potential by comparing its predictions with the results of a recent experimental measurement of the average ionization degree of C in a CH-mixture plasma ( Kraus et al. 2016 ). In this experiment, a highly compressed CH-mixture plasma (polystyrene) was created via spherically convergent shocks at the National Ignition Facility. Then, the spectrally resolved X-ray scattering of line radiation at 9.0 keV was recorded. The experiment measured an average ionization degree of 4.92 ± 0.15 for C at an average temperature of 86 ± 20 eV (radiation–hydrodynamics simulations show that