Identification of the Li ground state

The proton-stripping reaction from a ¹¹Be radioactive beam incident on a beryllium target demonstrates that only (7±3)% of the ⁹Li residues in the reaction are in coincidence with the 2.7 MeV γ-ray corresponding to the ⁹Li first excited state. This implies that the previously observed low-energy neutrons from the decay of the unbound nucleus ¹⁰Li represent a direct l=0 transition to the ⁹Li ground state. Consequently, neutron-unbound ¹⁰Li is proven to have the same parity inversion as occurs in the case of ¹¹Be with a  intruder state below the natural parity state.     

Absorption and Oxidation of Nitrogen Oxide in Ionic Liquids

A new strategy for capturing nitrogen oxide, NO, from the gas phase is presented. Dilute NO gas is removed from the gas phase by ionic liquids under ambient conditions. The nitrate anion of the ionic liquid catalyzes the oxidation of NO to nitric acid by atmospheric oxygen in the presence of water. The nitric acid is absorbed in the ionic liquid up to approximately one mole HNO₃ per mole of the ionic liquid due to the formation of hydrogen bonds. The nitric acid can be desorbed by heating, thereby regenerating the ionic liquid with excellent reproducibility. Here, time‐resolved in‐situ spectroscopic investigations of the reaction and products are presented. The procedure reveals a new vision for removing the pollutant NO by absorption into a non‐volatile liquid and converting it into a useful bulk chemical, that is, HNO₃.     

The swelling and dissolution of cellulose crystallites in subcritical and supercritical water

The swelling and dissolution phenomena of microcrystalline cellulose (MCC) were investigated in subcritical and supercritical water. Commercial MCC was treated in water at temperatures of 250–380 °C and a pressure of 250 bar for 0.25–0.75 s. As reaction products, undissolved but depolymerised cellulose residue, short-chain cellulose precipitate, water-soluble cello-oligosaccharides and monosaccharides, as well as their degradation products, were detected. The highest yield of the cellulose II precipitate was obtained after a reaction time of 0.25 s at 360 °C. Our hypothesis was that if the crystallites were swollen, the depolymerization pattern would be that of homogeneous reaction and the cellulose Iβ to cellulose II transformation would be observed. The changes in the structure of the undissolved cellulose residue were characterised by size exclusion chromatography, wide-angle X-ray scattering and ¹³C solid-state NMR techniques. In many cases, the cellulose residue samples contained cellulose II; however, due to experimental limitations, it remains unclear whether it was formed through the swelling of crystallites or the partial readsorption of the dissolved cellulose fraction. The molar mass distributions of untreated MCC and after low intensity treatments showed a bimodal shape. After high intensity treatments the high molar mass chains disappeared which indicated a complete swelling or dissolution of the crystallites.     

Wasserstein convergence rates for random bit approximations of continuous Markov processes

We determine the convergence speed of a numerical scheme for approximating one-dimensional continuous strong Markov processes. The scheme is based on the construction of certain Markov chains whose laws can be embedded into the process with a sequence of stopping times. Under a mild condition on the process' speed measure we prove that the approximating Markov chains converge at fixed times at the rate of 1/4 with respect to every p-th Wasserstein distance. For the convergence of paths, we prove any rate strictly smaller than 1/4. Our results apply, in particular, to processes with irregular behavior such as solutions of SDEs with irregular coefficients and processes with sticky points.     

Far field emission of micropillar and planar microcavities lattice-matched to ZnTe

We investigate light emission from ZnTe-based microcavities containing CdTe quantum dots (QDs), with 2D (planar cavity) and 0D (pillar cavities) photonic confinement. The angular distribution from the planar cavity is presented as well as 2D cross-sections of the far field distribution of radiation from the micropillars. The efficient and desirable modification of the isotropic radiation of the QDs is shown for such structures. The diffraction observed is found to be inherent for such experiments with large numerical aperture of the lens and small diameters of the investigated pillars. This diffraction is successfully modeled.     

K+N scattering in the constituent quark model

We calculate S-wave phase shifts of the KN system in the framework of a nonrelativistic quark model, using variational methods (generator coordinates). We show that the I = 0 channel is determined by the QCD residual interaction, which leads to a small repulsion, and that the I = 1 channel receives strong repulsive contributions already from quark exchange. We discuss the relevance and physical origin of these results. We furthermore construct an approximate local potential extracted from the nonlocal cluster interaction.     

Optical characterization of InxGa1−xN alloys

InGaN layers were grown by molecular beam epitaxy (MBE) either directly on (0 0 0 1) sapphire substrates or on GaN-template layers deposited by metal-organic vapor-phase epitaxy (MOVPE). We combined spectroscopic ellipsometry (SE), Raman spectroscopy (RS), photoluminescence (PL) and atomic force microscopy (AFM) measurements to investigate optical properties, microstructure, vibrational and mechanical properties of the InGaN/GaN/sapphire layers.The analysis of SE data was done using a parametric dielectric function model, established by in situ and ex situ measurements. A dielectric function database, optical band gap, the microstructure and the alloy composition of the layers were derived. The variation of the InGaN band gap with the In content (x) in the 0 < x ≤ 0.14 range was found to follow the linear law E_g = 3.44-4.5x.The purity and the stability of the GaN and InGaN crystalline phase were investigated by RS.     

Preparation of peralkylchromium(IV) compounds

Tetra-t-butylchromium was prepared from CrCl₃·3THF and t-butyllithium in pentane by a disproportionation reaction or from tetra-t-butoxychromium and t-butyllithium. It was isolated by sublimation and characterized by ESR, UV, visible and IR spectra. The following compounds were not isolated but characterized in solution by their ESR spectra: tetramethylchromium, tetraisopropylchromium, tetra-sec-butylchromium, tetra-n-butylchromium, tetra-3-pentylchromium and tetrakis(cyclohexylmethyl)chromium.