Shock wave propagation in dissociating low-Z liquids: D2

We present direct molecular dynamics simulations of shock wave propagation in liquid deuterium for a wide range of impact velocities. The calculated Hugoniot is in perfect agreement with the gas-gun data as well as with the most recent experimental data. At high impact velocities we observe a smearing of the shock wave front and propagation of fast dissociated molecules well ahead of the compressed region. This smearing occurs due to the fast deuterium dissociation at the shock wave front. The experimental results are discussed in view of this effect.     

Measurement of spin-transfer observables in p p-->Lambda Lambda at 1.637 GeV/c

Spin-transfer observables for p p-->Lambda Lambda have been measured using a transversely polarized frozen-spin target and a beam momentum of 1.637 GeV/c. Current models of the reaction near threshold are in good agreement with existing measurements performed with unpolarized particles in the initial state but produce conflicting predictions for the spin-transfer observables Dnn and Knn (the normal-to-normal depolarization and polarization transfer), which are measurable only with polarized target or beam. Measurements of Dnn and Knn presented here are found to be in disagreement with predictions from these models.     

The electronic structure of alkali-metal layers on semiconductor surfaces

Alkali-metal layers on semiconductor surfaces are model systems for metal-semiconductor contacts, Schottky barriers, and metallization processes. The strong decrease of the work function as a function of alkali-metal coverage is also technically made use of. Recently, however, interest in these systems is growing owing to ongoing controversial discussions about questions like: Is the adsorbate system at monolayer coverage metallic or semiconducting, and does the metallization take place in the alkali overlayer or in the top layer of the semiconductor? Is the bonding ionic or covalent? What ist the absolute coverage at saturation? What are the adsorption sites? Do all alkali metals behave similar on the same semiconductor surface? We try to answer some of the questions for Li, Na, K and Cs on Si(111)(2×1), K and Cs on Si(111)(7×7) and on GaAs(110), and Na and K on Si(100)(2×1) employing the techniques of direct and inverse photoemission.     

Diffusion of Cu in β-phase CuI

Measurements of ionic diffusion of Cu⁺ in solid CuI in the β-phase is carried out with a non-destructive radioactive tracer technique, utilizing coincidence counting of the annihilation gammas from the positron decay of ⁶⁴Cu. The diffusion coefficient and the activation energy for diffusion are evaluated. The experimental results show distinct diffusion character in the β-phase which differs from those in the γ-and -phases. The β-phase diffusion properties together with the previous results for γ-and -phases will provide valuable guidance for MD calculations, in which the diffusion coefficients and activation energies have been overestimated and the γ-β phase transition does not appear. The ionic conductivity of CuI estimated from tracer diffusion results and the Nernst-Einstein relation are compared with values from electrochemical methods. In all three phases the conductivities obtained from electrochemical methods are much lower than those calculated from the measured tracer diffusion coefficients.     

Über das Verfahren der zentralen Differenzen zur Lösung des Cauchyproblems für partielle Differentialgleichungen

The Cauchy-problem for Hermitian systems of partial differential equations and for equations of Schrödinger type is treated in some detail. Difference methods producing solutions even for large time intervals are discussed with special regard to stability properties.

---

---

Diese Arbeit wurde vom Schwedischen Technischen Forschungsrat und der staatlichen schwedischen Rechenzentrale (MNA) unterstützt.     

Auger energy shifts in fcc AgPd random alloys from complete screening picture and experiment

We extend the complete screening picture to ab initio calculations of Auger kinetic energy and Auger parameter shifts in metallic alloys. Experimental measurements of the L(3)M(4,5)M(4,5) Auger transition in fcc AgPd random alloys are compared with first-principles calculations and the results are in excellent agreement for both the Ag and Pd Auger shifts over the whole concentration range. We discuss the Auger kinetic energy shifts in terms of single-hole states for the 2p(3/2) core level and double-hole states for the 3d(5/2) level.     

Unified treatment of fluorescence and raman scattering processes near metal surfaces

We present a general model study of surface-enhanced resonant Raman scattering and fluorescence focusing on the interplay between electromagnetic effects and the molecular dynamics. Our model molecule is placed close to two Ag nanoparticles and has two electronic levels. A Franck-Condon mechanism provides electron-vibration coupling. Using realistic parameter values for the molecule we find that an electromagnetic enhancement by 10 orders of magnitude can yield Raman cross sections sigma(R) of the order 10(-14) cm(2). We also discuss the dependence of sigma(R) on incident laser intensity.     

First-principles theory of intermediate-valence f-electron systems

We propose a first-principles based method for calculating the electronic structure and total energy of solids in an intermediate-valence configuration. The method takes into account correlation effects (d-f Coulomb interaction) and many-body renormalization of the effective hybridization parameter of the f system. As an example, the formation of a pressure-induced intermediate-valence state in Yb is considered and its electronic structure and equation of state are calculated and compared to experimental data. The agreement is found to be excellent for both properties, and we argue that the developed method, which applies to any element or compound, provides for the first time a quantitative theoretical treatment of intermediate-valence materials.