Strangeness at the international Facility for Antiproton and Ion Research

The project of the international Facility for Antiproton and Ion Research (FAIR), co-located to the GSI facility in Darmstadt, was officially started on November 7, 2007. An investment of about 1 billion euro will permit new physics programs in the areas of low and medium energy antiproton research, heavy ion physics complementary to LHC, as well as in nuclear structure and astrophysics. The facility will comprise about a dozen accelerators and storage rings, which will enable simultaneous operations of up to four different beams.     

Perfluorinated tert‐Butoxides of Tin(II): The Dimeric Alkoxide and Its Monomeric Ate Complex

Surprisingly little is known about fluorinated tin(II) alkoxides. Here the synthesis and characterization of Sn(OR^F)₂ [OR^F = OC(CF₃)₃] and the crystal structures of its adducts with phenanthroline and dppe are reported. In addition, its ate complex [Sn(OR^F)₃]^– was synthesized with lithium or sodium as cation and as acetonitrile adduct. The thermolytic behavior of both, the alkoxide and the lithium stannate(II), was investigated together with first electrochemical measurements of Li[Sn(OR^F)₃].     

Threshold Photoelectron Spectroscopy of IO and HOI

Iodine oxides appear as reactive intermediates in atmospheric chemistry. Here, we investigate IO and HOI by mass-selective threshold photoelectron spectroscopy (ms-TPES), using synchrotron radiation. IO and HOI are generated by photolyzing iodine in the presence of ozone. For both molecules, accurate ionization energies are determined, 9.71±0.02 eV for IO and 9.79±0.02 eV for HOI. The strong spin-spin interaction in the ³Σ⁻ ground state of IO⁺ leads to an energy splitting into the Ω=0 and Ω=±1 sublevels. Upon ionization, the I−O bond shortens significantly in both molecules; thus, a vibrational progression, assigned to the I−O stretch, is apparent in both spectra.     

Zur Lage des Maximums der Ausbeutekurve bei der Sekundärelektronenemission

There exists a quantitative connection between penetration depth of primary electrons, the maximum escape depth of secondary electrons and the position of the maximum of the yield curve if one assumes: (1) the maximum of the yield curve is determined by an energyE _p ^max of the primary electrons where the maximum penetration depth of primary electrons equals the maximum escape depth of the secondary electrons; and (2) the maximum escape depth of secondary electrons is given by 10 atomic layers for all metals investigated as it has been found earlier by Mayer and Hölzl for potassium. These assumptions are confirmed experimentally by measurements of yield curves and energy distributions at defined conditions and by variation of several parameters as temperature, contamination of the surface, surface roughness, evaporation conditions, and angle of incidence of the primary electrons.     

Space-charge driven emittance growth in a 3D mismatched anisotropic beam

We investigate the phenomenon of space-charge driven emittance growth in a three-dimensional mismatched anisotropic charged particle beam with relevance to high-intensity linear accelerators. The final emittance growth can be understood as a superposition of the contributions from the mismatch-induced halo formation and from the anisotropy-induced energy exchange. The averaged emittance growth per degree of freedom is bounded from above by the so-called "free energy limit" extended by the contributions from energy exchange. The partition of the growth into longitudinal or transverse is, however, a strong function of the tune ratio including the possibility that an initially equipartitioned beam is even driven substantially away from equipartition. The growth of the beam halo extent is dominated by the effect of mismatch, whereas anisotropy itself generates practically no halo.     

Petunia-shaped superstructures of CaCO3 aggregates modulated by modified chitosan

This paper presents the crystallization behavior of calcium carbonate at the air/liquid interface of aqueous systems of carboxymethyl chitosan (CMCS) using the Kitano method. Although the synthesized CMCS (Mw approximately 100,000) with 1.57 degree of carboxymethyl substitution shows no surface activity, it controls the crystallization of calcium carbonate to form a petunia-shaped superstructure. The shuttlecock-like head of this superstructure strongly supports Colfen's opinion (Rudloff, J.; Colfen, H. Langmuir 2004, 20, 991-996) for the existence of a gas template of CO2 bubbles temporarily captured by polymer molecules, while formation of the stem of this superstructure is provisionally attributed to the presence of the strong electrostatic interactions between calcium ions and the carboxylate groups. The CaCO3 superstructure and its morphology depend not only on the polymer concentration but also on the combined number of calcium ions per CMCS molecule. These results imply that this simple and versatile method expands the morphological investigation of mineralization processes.     

Pseudodifferential Calculi on the Half-line Respecting Prescribed Asymptotic Types

Given asymptotics types P, Q, pseudodifferential operators are constructed in such a way that if u(t) possesses conormal asymptotics of type P as t +0, then Au(t) possesses conormal asymptotics of type Q as t +0. This is achieved by choosing the operators A in Schulzes cone algebra on the half-line , controlling their complete Mellin symbols { }, and prescribing the mapping properties of the residual Green operators. The constructions lead to a coordinate invariant calculus, including trace and potential operators at t = 0, in which a parametrix construction for the elliptic elements is possible. Boutet de Monvels calculus for pseudodifferential boundary problems occurs as a special case when P = Q is the type resulting from Taylor expansion at t = 0.     

Finding the Sink Takes Some Time: An Almost Quadratic Lower Bound for Finding the Sink of Unique Sink Oriented Cubes

We give a worst-case (n²/log n) lower bound on the number of vertex evaluations a deterministic algorithm needs to perform in order to find the (unique) sink of a unique sink oriented n-dimensional cube. We consider the problem in the vertex-oracle model, introduced in [18]. In this model one can access the orientation implicitly, in each vertex evaluation an oracle discloses the orientation of the edges incident to the queried vertex. An important feature of the model is that the access is indeed arbitrary, the algorithm does not have to proceed on a directed path in a simplex-like fashion, but could jump around. Our result is the first superlinear lower bound on the problem. The strategy we describe works even for acyclic orientations. We also give improved lower bounds for small values of n and fast algorithms in a couple of important special classes of orientations to demonstrate the difficulty of the lower bound problem.     

Surfaces of Van Vleck ferro- and paramagnets

We investigate surface effects of exchange-induced Van Vleck ferro- and para-magnets. It is pointed out that surface magnetism may exist at temperatures considerably above the bulk Curie temperature and even if the bulk is an intrinsic Van Vleck paramagnet. Model calculations using a point charge model are done for a 6-, 8- and 12-fold coordination of the crystal field ligands. They demonstrate that the magnetic surface properties are usually very different from those of the bulk.