Adsorbate-site determination by surface-state spectroscopy?

Electronic surface states can interact with adsorbate orbitals only if they have the same symmetry with respect to the adsorption site. Therefore, the interaction between a surface state and a particular adsorbate orbital provides information about the symmetry properties of the adsorption site. This is discussed for the adsorption of hydrogen and ethylene on Ni(110).     

The axiom of real Blackwell determinacy

The theory of infinite games with slightly imperfect information has been developed for games with finitely and countably many moves. In this paper, we shift the discussion to games with uncountably many possible moves, introducing the axiom of real Blackwell determinacy ${\mathsf{Bl-AD}_\mathbb{R}}$ (as an analogue of the axiom of real determinacy ${\mathsf{AD}_\mathbb{R}}$ ). We prove that the consistency strength of ${\mathsf{Bl-AD}_\mathbb{R}}$ is strictly greater than that of AD.     

Soft X‐ray absorption spectroscopy and resonant inelastic X‐ray scattering spectroscopy below 100 eV: probing first‐row transition‐metal M‐edges in chemical complexes

X‐ray absorption and scattering spectroscopies involving the 3d transition‐metal K‐ and L‐edges have a long history in studying inorganic and bioinorganic molecules. However, there have been very few studies using the M‐edges, which are below 100 eV. Synchrotron‐based X‐ray sources can have higher energy resolution at M‐edges. M‐edge X‐ray absorption spectroscopy (XAS) and resonant inelastic X‐ray scattering (RIXS) could therefore provide complementary information to K‐ and L‐edge spectroscopies. In this study, M_2,3‐edge XAS on several Co, Ni and Cu complexes are measured and their spectral information, such as chemical shifts and covalency effects, are analyzed and discussed. In addition, M_2,3‐edge RIXS on NiO, NiF₂ and two other covalent complexes have been performed and different d–d transition patterns have been observed. Although still preliminary, this work on 3d metal complexes demonstrates the potential to use M‐edge XAS and RIXS on more complicated 3d metal complexes in the future. The potential for using high‐sensitivity and high‐resolution superconducting tunnel junction X‐ray detectors below 100 eV is also illustrated and discussed.     

Micromagnetism of two-dimensional permalloy particles with different aspect ratios

Micromagnetic properties of the Fe₁₉Ni₈₁ (5 nm)/NiO (50 nm)/Fe₁₉Ni₈₁ (30 nm) structured system have been investigated in a photoemission electron microscope in the magnetic X-ray circular dichroism operating mode. The microstructured Fe₁₉Ni₈₁ (5 nm) film contained two-dimensional islands with the aspect ratio varying from 1:1 to 10:1, and the linear size of their long axis comprised 24, 12 and 6 μm. It is shown that the magnetic domains have the direction of magnetization preferentially parallel and antiparallel to the magnetic field direction in which this system was prepared. Their number is determined by the particles’ sizes, their shape as well as by the direction of the external magnetizing field and can be characterized by a non-monotonic size dependence. The magnetization of domains with different lateral sizes was found to be 0.4 T with an accuracy better than 20%. Received: 29 May 2002 / Accepted: 17 July 2002 / Published online: 22 November 2002 RID="*" ID="*"Corresponding author. Fax: +49-6131/392-3807, E-mail: nepijko@mail.uni-mainz.de     

Influence of the degree of ionization on the growth mechanism of poly(diallyldimethylammonium)/poly(acrylic acid) multilayers

pH‐dependent growth laws of the mass coverage Γ(n) of poly(diallyldimethylammonium) chloride and poly(acrylic acid) (PAA) layer‐by‐layer films are analyzed by Quartz Crystal Microbalance‐D. (Attenuated Total Reflection)‐FTIR spectroscopy shows a degree of dissociation of acrylic acid groups in the films identical to that in solution. Apart from pH‐regimes of differently pronounced exponential and linear growth, the corresponding kinetics indicate pH‐dependent adsorption, reorganization, and diffusion processes. As the thickest films form with almost uncharged PAA (low pH), the results can only partly be explained by the dissociation degree of PAA in the film. For intermediate and high pH values chain interdiffusion as a mechanism for nonlinear growth is strongly dependent on the charge density of the PAA chains. However, at low pH other types of interactions, most likely ion–dipole interactions, play a major role in the multilayer growth. Furthermore, a change in the symmetry of growth can be observed in the low to intermediate pH range. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 425–434     

Mass transfer limitation in thermogravimetry of biomass gasification

In order to determine the intrinsic reactivity behavior from thermogravimetry studies, the experimental conditions should be such that the reactions are not mass transfer limited. Biomass char usually has a higher reactivity than coal chars. Therefore, mass transfer limitations may be more problematic when studying biomass char reactivity. Chemical reaction kinetics and mass transfer processes present in thermogravimetry are used for modeling the overall reaction rate for spruce bark CO₂ gasification. Thermogravimetric experiments are carried out between 700 and 900 °C, and the CO₂ concentration is varied between 10 and 90 vol%. The intrinsic activation energy is found to be 120 kJ mol^?1. The transition temperature between regimes I and II is here defined when the fraction apparent to true activation energy equals 0.75. Higher external mass transfer (e.g., by decreasing the diffusion path through the crucible’s freeboard), decreasing the sample amounts, and higher CO₂ partial pressures for the Langmuir–Hinshelwood reaction type increase the transition temperature. The results show that the transition temperature between regimes I and II conditions is approx. 1,030 °C for 90 vol% CO₂.