On the electronic density of states of the transition metals

A superposition model is suggested to describe the electronic density of states curves of binary alloys with the aid of those of the component metals. It is based on a charge transfer between the different atomic cells. The application of this model to different spectroscopic methods studying the density of states brings up the question of the localizing and averaging properties of the corresponding experiments.     

Massive photons in General Relativity

In order to avoid a speed-of-light catastrophe in General Relativity with an electromagnetic source, gauge invariance with respect to the electric charge is broken with the photon acquiring mass. The general equations for the Einstein-Maxwell system are derived for the case with massive photons. Nonminimal couplings which might compete with the small minimal photon mass term are included.     

Tunneling from an ultrathin quantum well in a strong electrostatic field: A comparison of different methods

A case study of field emission from a zero-range quantum well has been carried out. The various strong-field approximations, both time-dependent and time-independent, are discussed and compared with exact numerical results. The exponential decay law is shown to be a good approximation on the average, but it cannot account for short-time ripples in the ionisation probability.     

Polarization forces in elastic nuclear coulomb scattering

The polarization potential is determined for the adiabatic sub-Coulomb scattering of two nuclei. No collective coordinates are used. The relevant nuclear polarizabilities are evaluated by means of sum rules. The departure from the pure Rutherford scattering law is calculated for various nuclei. For adiabatic heavy-ion collision the differential cross section is found to be reduced below the Coulomb scattering by one percent at backward angles.     

Enantioselective total synthesis of (S)-(−)-quinolactacin B

The enantioselective total synthesis of (−)-quinolactacin B (−)-1 was performed in seven steps and 33% overall yield from tryptamine. The synthesis features the use of ruthenium catalytic asymmetric hydrogen reaction to introduce the chirality in dihydro-β-carboline 2. Based on Noyori’s work, the hydrogenation using the (R,R)-TsDPEN-Ru complex produces dihydro-β-carbolines possessing the (S) absolute configuration, the corrected asymmetric center of the natural product. The synthetic quinolactacin B displayed optical rotations that was in accordance with that of the natural product, thereby supporting the (S) configuration for natural quinolactacin B. The final product’s stereochemical assignment is in agreement with that proposed by Nakagawa and co-workers.     

a 0 + (980)-resonance production in the reaction pp → dπ + η close to the K\bar K threshold

The reaction pp → dπ ⁺ η has been measured at a beam energy of T _p = 2.65 GeV (p _p = 3.46 GeV/c) using the ANKE spectrometer at COSY-Julich. The missing-mass distribution of the detected dπ ⁺ pairs exhibits a peak around the η mass on top of a strong background of multipion pp → dπ ⁺(nπ) events. The differential cross section d ⁴ σ/dΩ_d dΩ _π ⁺ dp _d dp _π ⁺ for the reaction pp → dπ ⁺ η has been determined model independently for two regions of phase space. Employing a dynamical model for the a ₀ ⁺ production allows one then to deduce a total cross section of σ(pp → da ₀ ⁺ → dπ ⁺ η) = 1.1 ± 0.3_stat ± 0.7_syst μb for the production of π ⁺ η via the scalar a ₀ ⁺ (980) resonance and σ(pp → dπ ⁺ η) = 3.5 ± 0.3_stat ± 1.0_syst μb for the nonresonant production. Using the same model as for the interpretation of recent results from ANKE for the reaction , the ratio of the total cross sections is , which is in agreement with branching ratios in the literature. The text was submitted by the authors in English.     

Design of an NO photoinduced releaser xerogel based on the controlled nitric oxide donor trans-[Ru(NO)Cl(cyclam)](PF6)2 (cyclam=1,4,8,11-tetraazacyclotetradecane)

The immobilization and properties of the nitric oxide donor trans-[Ru(NO)Cl(cyclam)](PF(6))(2), RuNO, entrapped in a silica matrix by the sol-gel process is reported herein. The entrapped nitrosyl complex was characterized by spectroscopic (UV-vis, infrared (IR), X-ray photoelectron, and (13)C and (29)Si MAS NMR) and electrochemical techniques. The entrapped species exhibit one characteristic absorption band in the UV-vis region of the electronic spectrum at 354 nm and one IR nu(NO) stretching band at 1865 cm(-1), as does the RuNO species in aqueous solution. Our results show that trans-[Ru(NO)Cl(cyclam)](PF(6))(2) can be entrapped in a SiO(2) matrix with preservation of the molecular structure. However, in a SiO(2)/SiNH(2) matrix, the complex undergoes a nucleophilic attack by the amine group at the nitrosonium. Irradiation of the complex, entrapped in the SiO(2) matrix, with light of 334 nm, resulted in NO release. The material was regenerated to its initial nitrosyl form by reaction with nitric oxide.