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The equation of state of light elements is essential to understand the structure of Jovian planets and inertial confinement fusion research. The Omega laser was used to drive a planar shock wave in the cryogenically cooled deuterium, creating warm dense matter conditions. X-ray scattering was used to determine the spectrum near the boundary of the collective and noncollective scattering regimes using a narrow band x-ray source in backscattering geometry. Our scattering spectra are thus sensitive to the individual electron motion as well as the collective plasma behavior and provide a measurement of the electron density, temperature, and ionization state. Our data are consistent with velocity-interferometry measurements previously taken on the same shocked deuterium conditions and presented by K. Falk et al. [High Energy Density Phys. 8, 76 (2012)]. This work presents a comparison of the two diagnostic systems and offers a detailed discussion of challenges encountered.

We employ a pseudopotential approach to investigate the screening of ionic cores in partially ionized plasmas. Here, the effect of the tightly bound electrons is condensed into an effective potential between the (free) valence electrons and the ionic cores. Even for weak electron-ion coupling, the corresponding screening clouds show strong modifications from the Debye result for elements heavier than helium. Modifications of the theoretically predicted x-ray scattering signal and implications on measurements are discussed.

We investigate the short-range structure in strongly coupled fluidlike plasmas using the hypernetted chain approach generalized to multicomponent systems. Good agreement with numerical simulations validates this method for the parameters considered. We found a strong mutual impact on the spatial arrangement for systems with multiple ion species which is most clearly pronounced in the static structure factor. Quantum pseudopotentials were used to mimic diffraction and exchange effects in dense electron-ion systems. We demonstrate that the different kinds of pseudopotentials proposed lead to large differences in both the pair distributions and structure factors. Large discrepancies were also found in the predicted ion feature of the x-ray scattering signal, illustrating the need for comparison with full quantum calculations or experimental verification.

The energy loss of highly charged ions in dense plasmas is investigated. The applied model includes strong beam-plasma correlation via a quantum T-matrix treatment of the cross sections. Dynamic screening effects are modeled by using a Debye-like potential with a velocity dependent screening length that guarantees the known low and high beam velocity limits. It is shown that this phenomenological model is in good agreement with simulation data up to very high beam-plasma coupling. An analysis of the stopping process shows considerably longer ranges and a less localized energy deposition if strong coupling is treated properly.

Temperature equilibration in dense, strongly coupled plasmas has been investigated without most of the usual simplifying assumptions. A quantum kinetic approach is used that accounts for strong electron-ion collisions through an exact T-matrix treatment of the scattering cross section using a screened interaction. Our results reveal the accuracy of the usual Spitzer formula for Coulomb logarithms larger than about three. Moreover, a simple model based on hyperbolic orbits yields surprisingly accurate results. We also have included equation of state effects to describe realistic plasmas.

The stopping power of strongly coupled, partially ionized plasmas is investigated for charged beam particles with arbitrary velocities. Our approach is based on kinetic equations of the Boltzmann type that are suitably generalized to describe three-particle collisions. In this way, we consider elastic collisions between the beam and free plasma particles as well as the ionization and excitation of composite plasma particles by beam particle impact. Explicit expressions for both contributions are given in terms of the momentum transfer cross section that has been generalized for three-particle collisions. For fast beam particles, we obtain a generalized Bethe formula that includes correction terms due to the nonideality of the target plasma. Results are shown for hydrogen, carbon, and argon plasmas. Considerable modifications compared to the ideal behavior arise for strongly coupled plasmas. In particular, we are able to describe the Mott transition in the stopping power of dense, partially ionized plasmas.