MATTER AND STOPPING IN MATTER UNDER EXTREME CONDITIONS

For the dynamic behaviour of a target under irradiation with dense par ticle beams, it is essential to study static and transport properties of matter over a wide range of densities and temperatures. Of particul ar interest are the formation of neutral atoms and molecules through r ecombination in a dense plasma, and the eventual emergence of ordered structures, as well as the delocalization and the lowering of the cont inuum edge that precurses the transition to a metallic state. As a the oretical tool, we employ wave packet molecular dynamics, in which elec trons are represented by Gaussian wave packets, whose parameters follo w pseudo-Hamiltonian dynamics. To exclude artifacts from the finite si ze of the simulation box, about 10(3) particles must be simulated. For reasons of numerical economy, the wave function is only pairwise symm etrized at present. As stationary observables, we study the energy-res olved electron-proton pair distribution function for hydrogen and the spectral density of the electrons. With increasing density, we observe the delocalization of the states and the lowering of the continuum ed ge. As a dynamical observable, we consider the stopping of ions. In co mparison with classical point particles, the finite width of the wave packet leads to a smoothing of the singular Coulomb potential and a re duction of the stopping power. This is confirmed by actual calculation s of the stopping of ions in matter.