No abstract

A kinetic theory for quantum many-particle systems in time-dependent electromagnetic fields is developed based on a gauge-invariant formulation. The resulting kinetic equation generalizes previous results to quantum systems and includes many-body effects. It is, in particular, applicable to the interaction of strong laser fields with dense correlated plasmas.

In this paper, nonequilibrium properties of strongly coupled plasmas are considered. Usually, such problems are dealt with using Boltzmann– or Lenard–Balescu-type equations. However, for the application to strongly coupled plasmas, these equations exhibit several shortcomings. So, it is not possible (i), to describe the short time kinetics, (ii), to recover the correct (energy) conservation laws and thermodynamics, and, (iii), to account for the formation or destruction of bound states. Therefore, the kinetics of strongly coupled plasmas is considered starting from the Kadanoff–Baym equations, which are known to overcome the above limitations. This is demonstrated by a numerical solution of the two-time Kadanoff–Baym equations in second Born approximation. To be able to discuss approximations which are physically more interesting, it is advantageous to proceed to the time diagonal Kadanoff–Baym equations. In first order gradient expansion, generalizations of the Boltzmann and of the Lenard–Balescu kinetic equations are derived accounting for the bound state problem, too. Thus, the shortcomings (i)–(iii) mentioned above are overcome. Finally, the kinetic equations are applied to the problem of ionization kinetics.

A quantum kinetic approach for the energy relaxation in strongly coupled plasmas with different electron and ion temperatures is presented. Based on the density operator formalism, we derive a balance equation for the energies of electrons and ions connecting kinetic, correlation, and exchange energies with a quite general expression for the electron-ion energy-transfer rate. The latter is given in terms of the correlation function of density fluctuations which allows for a derivation of increasingly realistic approximation schemes including a coupled-mode expression. The equilibration of the contributions of the total energy including the species temperatures in dense hydrogen and beryllium relevant for inertial confinement fusion is investigated as an example.

We report on the dynamics of ultrafast heating in cryogenic hydrogen initiated by a ≲300  fs, 92 eV free electron laser x-ray burst. The rise of the x-ray scattering amplitude from a second x-ray pulse probes the transition from dense cryogenic molecular hydrogen to a nearly uncorrelated plasmalike structure, indicating an electron-ion equilibration time of ∼0.9  ps. The rise time agrees with radiation hydrodynamics simulations based on a conductivity model for partially ionized plasma that is validated by two-temperature density-functional theory.