We propose a model for calculating free-free absorption (inverse bremsstrahlung) in hot dense plasmas. This model writes the total Gaunt factor as the product of a static factor and a dynamic factor. The treatment of the static part is based on a relation between the absorption cross section and the elastic scattering cross section, which is exact for very low frequencies and becomes asymptotically correct when the Born approximation is valid. Generalizing this relation provides an expression of the absorption cross section Q(k, k′), which depends on the initial and final wave vectors k and k′, as an integral of a unique function S*(k). The calculation of nondiagonal matrix elements (k ≠ k′) is thus avoided. The analytic summation of the high angular momenta in the partial wave expansion of the cross section makes possible to apply the model in the limit of weak electron screening. The collective effects are accounted for in a dynamic Gaunt factor and in an index of refraction different from unity. Numerical results for the Gaunt factor in cesium are presented and discussed. An application to the mean opacities of carbon is also shown.

We reconsider correlated ion stopping in plasmas with the aim to emphasize the basic features and their underlying physics. For a better understanding of the effects connected with correlated ion stopping, it is useful to distinguish two types of correlated ion stopping, characterized by a small or large ratio of the correlation length of the ions to the screening length in the plasma. These two types of correlated ion stopping are of rather different character. We describe and explain these differences and give some generic examples of ion structures and ion clusters to demonstrate the basic features of both types of correlated stopping. This shows that only the short-range correlations always yield an enhanced stopping, whereas the long-range correlations, in general, reduce the stopping compared to single, individual ions. We mainly consider classical plasmas; the basic features, however, remain unchanged for a jellium target as well as for a plasma at any degeneracy.

The possibility of using the analytical wave functions in hydrogen-like and semiclassical approximations for self-consistent Hartree-Fock-Slater model is considered. The usage of analytical wave functions simplifies the obtaining of self-consistent field and yields the suitable expressions for calculation various characteristics of high-temperature plasmas—cross sections of radiative processes, Rosseland mean opacities, and equation of state.

Due to the high nonequilibrium charge states specific to heavy ions, the plasma regime with coupling parameters l/ND < 1 and Zp/ND > 1 (ND ∼ number of electrons in a Debye sphere, Zp mean charge state of the projectile) is of interest for the applications. In this regime the stopping power cannot be obtained by a linearization of the Vlasov-Poisson system, but forcing a fully nonlinear treatment. In the present paper the Vlasov-Poisson system is solved numerically by using the capability of the new generation of massively parallel supercomputers. The results are compared with the standard dielectric theory and a binary collision approach. Charge-state calculations are performed, accounting for all relevant features of the atomic processes and the spectra characteristic to heavy ions in dense plasma targets. The results show good agreement with experimental measurement for medium and heavy ions penetrating a Z-pinch device.

The behavior of matter under intense soft X-radiation is considered. An impulse of X-radiation (about 2–1012 W/cm2) produced a strong shock wave in the sample. The velocity of this shock wave was measured. A shock compression about 300 GPa in the lead target was achieved.