[en] The author asks what further information is accessible when photoionization is studied at higher energies, as in the x ray and γ-ray regimes. For a open-quotes completeclose quotes experiment it is in fact not generally sufficient, even at low energy, to determine the energy dependence of the usual dipole parameters. Rather, such parameters should be determined for each multipole or, alternatively, the energy and angle dependence of angular distributions and polarization correlations. However, it is known that in some circumstances, particularly for total cross sections from s-subshells, relativistic and higher multipole contributions tend to cancel well into the γ-ray regime, leaving a non relativistic dipole description useful. Conversely, it has been shown that in some circumstances quadrupole effects remain of some importance at low energy in angular distributions, even for light elements and even at threshold. In general, and neglecting small relativistic effects, except for bound state normalization the high energy photoeffect matrix element is given by the matrix element in the nuclear point Coulomb potential. Consequently, at all energies the dependence of the photoionization matrix element on atomic properties is given by dipole and quadrupole terms, plus small octupole contributions, within an accuracy of 1%. This result, demonstrated within independent particle approximation, is expected to remain valid when many-electron correlations are included

No abstract available

[en] In many cases fragmentation of molecules upon inner-shell ionization is very unspecific with respect to the initially localized ionization site. Often this finding is interpreted in terms of an equilibration of internal energy into vibrational degrees of freedom after Auger decay. In this paper, we investigate the X-ray photofragmentation of ethyl trifluoroacetate upon core electron ionization at environmentally distinct carbon sites using photoelectron–photoion–photoion coincidence measurements and ab initio electronic structure calculations. For all four carbon ionization sites, the Auger decay weakens the same bonds and transfers the two charges to opposite ends of the molecule, which leads to a rapid dissociation into three fragments, followed by further fragmentation steps. Finally, the lack of site specificity is attributed to the character of the dicationic electronic states after Auger decay instead of a fast equilibration of internal energy.

No abstract available

[en] We show that the complete characterization of arbitrarily short isolated attosecond x-ray pulses can be achieved by applying spectral shearing interferometry to photoelectron wave packets. These wave packets are coherently produced through the photoionization of atoms by two time-delayed replicas of the x-ray pulse, and are shifted in energy with respect to each other by simultaneously applying a strong laser field. The x-ray pulse is reconstructed with the algorithm developed for optical pulses, which requires no knowledge of ionization physics. Using a 800-nm shearing field, x-ray pulses shorter than ∼400 asec can be fully characterized

[en] The chaotic dynamics of a particle in two-dimensional periodic potentials or in potentials with quasicrystalline symmetry is investigated. It is shown that under conditions of deterministic chaos the infinite motion of a particle in a periodic hexagonal potential has the character of Levy flights, i.e., diffusion motion alternating with periods of almost free motion. A connection is established between the random walk of the particle and diffusion in multifractals. In potentials with higher degree of symmetry (of the quasicrystalline type) the random walk is close to the ordinary diffusion process

No abstract available

[en] Experimental data on Luna 16, 20 and Apollo 11-17 soils are examined to delineate correlations between various phenomena and parameters characterising lunar surface processes, i.e. micrometeorite impacts, solar flare tracks, size distribution of soil grains and concentration of solar wind gases. Relations which allow one to deduce the time scales involved in the development of the lunar regolith and formation of 'mature' soils with respect to surface irradiation are presented. (author)

[en] We study the 2D motion of independent point particles colliding with a periodic array of circular obstacles. The interaction between the particles and the obstacles is described by a total accommodation reflection law. Assuming that the array of scatterers has finite horizon, the density of particles is approximated by the solution of a diffusion equation in the long-time and large-scale regime. The proof relies on a multiscale asymptotics and gives the order of approximation

[en] This work is devoted to the thermodynamics of high-temperature dense hydrogen plasmas in the pressure region between 10^-1 and 10² Mbar. In particular, we present for this region results of extensive calculations based on a recently developed path integral Monte Carlo scheme (direct PIMC). This method allows for a correct treatment of the thermodynamic properties of hot dense Coulomb systems. Calculations were performed in a broad region of the non-ideality parameter Γ < or approx. 3 and degeneracy parameter n_eΛ³ < or approx. 10. We give a comparison with a few available results from other path integral calculations (restricted PIMC) and with analytical calculations based on Pade approximations for strongly ionized plasmas. Good agreement between the results obtained from the three independent methods is found. (author)