Shaping of intense ion beams into hollow cylindrical form

A specifically tailored plasma lens could shape a high-energy, heavy-ion beam into the form of a hollow cylinder without loss of beam intensity. It has been experimentally confirmed that both a positive as well as a negative radial gradient of the current density in the active plasma lens can be the underlying principle. Calculations were performed that yield the ideal current density distribution for both cases. A numerical simulation of an experiment with an intense ion beam highlights that the shaping of the beam increases the achievable compression in a lead sample.     

Adsorption kinetics and dynamics of small organic molecules on a silica wafer: Butane, pentane, nonane, thiophene, and methanol adsorption on SiO2/Si(1 1 1)

The adsorption kinetics (by thermal desorption spectroscopy) and adsorption dynamics (by molecular beam scattering) have been determined for a number of alkanes, methanol, thiophene, and water on a silica wafer—SiO₂/Si(1 1 1). No indications for bond activation were present, i.e., all probe molecules adsorb molecularly obeying 1st order kinetics. The coverage-dependent heat of adsorption has been determined accordingly. The adsorption dynamics are precursor-mediated with Kisliuk-like shapes of the adsorption probabilities at low impact energies and adsorbate-assisted adsorption at large impact energies.     

Lifetime measurements in Pt and the shape coexistence picture

Lifetimes for levels in the yrast band of ¹⁸⁴Pt have been measured up to spin 16⁺ using the recoil distance technique. The B(E2) values exhibit a marked increase in going from spin 2 to 10, consistent with a proposal that two bands of different deformations are mixing at low spin. This provides further support for shape coexistence occuring at low excitation energies in this region.     

An Intermolecular Hydrogen Bridge between a Porphyrinoid μ‐Oxido Diiron(III) Host and a Guest Water Molecule

μ‐Oxido‐bis[(hexaethyldimethyl‐2,2′‐bidipyrrinato)iron(III)] ( 1 ) crystallizes as a mixed dichloromethane/water solvate as black plates in the triclinic system, space group P\bar{1} , with a = 14.536(3), b = 16.194(3), c = 25.883(5) Å, α = 98.89(3)°, β = 91.28(3)°, γ = 90.56(3)°, and Z = 2. In the crystal structure two distinct solvates 1· CH₂Cl₂ and 1· H₂O are present in equal ratio. In both cases the solvent is found in direct vicinity of the Fe–O–Fe subunit and is located within a binding pocket formed by the two helically distorted tetrapyrroles. Whereas the dichloromethane molecule is oriented within this pocket as a dipole with the positive end pointing towards the oxygen atom of the Fe–O–Fe subunit, the water molecule forms a hydrogen bond with this site, supported by additional weak interactions with adjacent N‐donor atoms.     

Atomistic modeling of Zn deposition on the low index faces of Cu

The formation process of Zn/Cu surface alloys is investigated using the Bozzolo-Ferrante-Smith (BFS) method for alloys. The effects of the crystallographic orientation on the deposition process, formation of surface alloys as a function of temperature and coverage, Zn surface migration, and interdiffusion in the Cu substrate, are modeled and discussed with atom-by-atom energy analyses and large scale simulations.     

Structural elucidation of new ferulic acid-containing phenolic dimers and trimers isolated from maize bran

Four new phenolic dimers and trimers that contain ferulic acid moieties were isolated from the alkaline hydrolyzate of insoluble maize bran fiber and their structures were established by 1D/2D NMR and mass spectrometry. The biological role of one dimer remains unclear whereas the dimeric vanillin-ferulic acid-cross-product probably represents an oxidative degradation product from the corresponding diferulate. Both ferulic acid dehydrotrimers are able to cross-link polysaccharide chains. However, the 5-5/8-O-4(H₂O)-triferulic acid may be a cross-link in its identified structure whereas we assume that the identified 8-O-4/8-5(non-cyclic)-triferulic acid arose from a natural 8-O-4/8-5(cyclic)-triferulate analog during the saponification process.