On some new green emitting phosphors with Sr3 (PO4)2 type structure

New sodium strontium rare-earth orthophosphates with general formula Na_xSr_3?2xLn_x (PO₄)₂ (Ln = La, Nd, Gd) have been prepared and characterized. They seem to be of Sr₃ (PO₄)₂ structural type. In NaSrLa_1?x?yCe_xTb_y (PO₄)₂, a new green phosphor absorbing in the UV region, high yield results from a Ce³⁺ → Tb³⁺ energy transfer.     

EPR and Magnetic Susceptibility of Na2O–CuO–P2O5 Glasses

Abstract

(50?x/2)Na₂O–xCuO–(50?x/2)P₂O₅ glasses (x=1, 5, 15, or 30 mol%) have been prepared and characterized by electron paramagnetic resonance (EPR) and magnetic susceptibility measurements. The shape of the Cu²⁺ EPR spectrum depends on the Cu content, and the corresponding computer simulations suggest that the Cu²⁺ ions occupy two different sites in these glasses: one of them is preponderant at low Cu content and the other is preponderant at high content, in which the Cu²⁺–Cu²⁺ interactions are more important. From EPR parameters, it was found that for the site at low content, the covalency of copper ion bonding with the surrounding ligands is appreciable. The magnetic susceptibility data appear to follow the Curie–Weiss law (χ=C/(T?θ_p)) with negative paramagnetic Curie temperature θ_p indicating antiferromagnetic interactions between Cu²⁺ ions that are more significant in the samples with high Cu content, in agreement with EPR results.     

Theoretical study of species formed by IA and IB metals or ions and a CN ligand

Multireference second-order perturbation calculations have been carried out for copper and sodium complexes involving one CN ligand. Neutral compounds are strongly linked, cyanides M-CN being more stable than isocyanides M-NC (M = Cu, Na) as in the case of the pair HCN/HNC. Cations are much less strongly linked, Cu-NC⁻ being predicted to be the only system having a fairly bound structure, at variance with the dominance of the cyanide form in the HCN⁺/HNC⁺ pair.     

Interaction of lead atom with atmospheric dioxygen and ozone: quantic study of the structure and the stability of resulting Pb(On) (n=1,2,3) compounds

Lead reaction with oxygen and ozone molecules is of a great importance for the study of the impact of this metal in the atmosphere medium. Stable species, intermediates, and transition states of possible resulting complexes have been studied with the three parameter hybrid B3LYP exchange-correlation DFT method, and coupled cluster with single, double, and triple excitation methods. Geometry, and spectroscopic and thermodynamic properties obtained for the different species are presented, discussed, and compared to available experimental data. On the basis of the knowledge of the thermal dissociation enthalpies and the absorbed wave length edges calculated for each species, we have drawn the most probable oxygenated complexes present in the atmosphere.     

Direct measurements of Ab and Ac using vertex and kaon charge tags at the SLAC detector

Exploiting the manipulation of the SLAC Linear Collider electron-beam polarization, we present precise direct measurements of the parity-violation parameters A(c) and A(b) in the Z-boson-c-quark and Z-boson-b-quark coupling. Quark-antiquark discrimination is accomplished via a unique algorithm that takes advantage of the precise SLAC Large Detector charge coupled device vertex detector, employing the net charge of displaced vertices as well as the charge of kaons that emanate from those vertices. From the 1996-1998 sample of 400 000 Z decays, produced with an average beam polarization of 73.4%, we find A(c)=0.673+/-0.029(stat)+/-0.023(syst) and A(b)=0.919+/-0.018(stat)+/-0.017(syst).