Combining Rhodium and Photoredox Catalysis for CH Functionalizations of Arenes: Oxidative Heck Reactions with Visible Light

Direct, oxidative metal‐catalyzed C? H functionalizations of arenes are important in synthetic organic chemistry. Often, (over‐)stoichoimetric amounts of organic or inorganic oxidants have to be used in these reactions. The combination of rhodium and photoredox catalysis with visible light allows the direct C? H olefination of arenes. Small amounts (1 mol %) of a photoredox catalyst resulted in the efficient C? H functionalization of a broad range of substrates under mild conditions.     

A theoretical study of the influence of ambipolar diffusion on the population distribution of excited states in a plasma

The effect of charged particle diffusion on excitation temperature was investigated theoretically, assuming that the diffusion processes are ambipolar and that the charged particles return to the plasma in the form of ground state atoms, after recombination at the plasma boundary. An approximate expression was obtained by solving a set of balance equations for the excited state atom densities. It shows that, with increase of the plasma pressure, the excitation temperature rises and approaches the electron temperature. It was found also that, as the electron density increases, the diffusion effect on the excitation temperature diminishes. A criterion was obtained which should be satisfied so that the excitation temperature may be in agreement with the electron temperature. The theoretical results of this paper are in good agreement with experimental results.     

Modification of the omega-meson lifetime in nuclear matter

Information on hadron properties in the nuclear medium has been derived from the photoproduction of omega mesons on the nuclei C, Ca, Nb, and Pb using the Crystal Barrel/TAPS detector at the ELSA tagged photon facility in Bonn. The dependence of the omega-meson cross section on the nuclear mass number has been compared with three different types of models: a Glauber analysis, a Boltzmann-Uehling-Uhlenbeck analysis of the Giessen theory group, and a calculation by the Valencia theory group. In all three cases, the inelastic omega width is found to be 130-150 MeV/c(2) at normal nuclear matter density for an average 3-momentum of 1.1 GeV/c. In the rest frame of the omega meson, this inelastic omega width corresponds to a reduction of the omega lifetime by a factor approximately 30. For the first time, the momentum dependent omegaN cross section has been extracted from the experiment and is in the range of 70 mb.     

Utilization of a dilute solid electrolyte in an oxygen gauge

An electrochemical cell involving a SrCl₂-based solid electrolyte either doped or undoped with SrO was investigated. The measuring electrode was of graphite or vitreous carbon and the reference electrode was formed by dissolving Ag⁺ ions and embedding a silver wire. A simple fabrication technique is described. The reported results indicate that an electrode reaction involving dissolved oxide ions: O₂(gas)+4e⁻=2O²⁻ (SrCl₂) can take place and be utilized in an oxygen gauge down to 200°C. The same cell also functions as a chlorinesensor. At least down to 10⁻³ atm, interference with oxygen is negligible.     

Nuclear orientation study of182Ta in 2H-TaS2

Quadrupole-interaction nuclear orientation experiments have been performed on¹⁸²Ta (j^π=3^?1; T_1/2=115d) in 2H-TaS₂. γ-anisotropies up to ～ 30 % have been observed at a temperature of ～ 8 mK, which, however, is only about half of the value expected taking into account known results of TDPAC measurements on¹⁸¹Ta in 2H-TaS₂. In principle, matrices of dichalcogenides could be well suited for nuclear quadrupole resonance on oriented nuclei (NQR-ON) experiments.     

Theoretical and experimental determinations of cesium oscillator strengths

The oscillator strengths of the cesium atom have been calculated theoretically using a semi-empirical construction of the effective potential acting on the valence electron. The results are compared with those deduced from an experimental determination in a quiescent cesium plasma.     

Reactivity of NASICON with water and interpretation of the detection limit of a NASICON based Na(+) ion selective electrode

The leaching of Na(+) ions from NASICON of composition Na(3)Zr(2)Si(2)PO(12) to the aqueous solution was evidenced. The origin of the Na(+) leaching was studied using Na(+) concentration and pH measurements as well as solution and X-ray analyses. The Na(+) released was mainly attributed to the dissolution of a second phase, predominantly amorphous. The rate of Na(+) release was found to be dependent on the inverse of the square of the particle size. It is proposed that it is controlled by diffusion within the particle. An effective diffusion coefficient was deduced to be of the order of 5x10(-10) cm(2) s(-1). The nature of the detection limit of the NASICON based Na(+) ion selective electrodes is discussed.