EPR study of Gd3+ ions in β-alumina single crystals

Single crystals of β-alumina doped with Gd³⁺ have been obtained by high-frequency induction melting of a NaAlO₂Al₂O₃ mixture and slow cooling, followed by a Gd³⁺Na⁺ exchange in molten GdCl₃. In these crystals, Gd³⁺ occupies only one out of the several possible sites, in the spinel block and not in the conduction plane (which could be anticipated from the ionic radius of the ion). The EPR data can be described by a spin Hamiltonian which includes trigonal terms. The b₂⁰ value is close to 0.08 cm^?1. These results suggest a localization of the ion either in the 4f-layer tetrahedra, or in an interstitial site. The second possibility, which is consistent with charge compensation (due to nonstoichiometry in β-alumina) by interstitial oxygen ions seems more likely.     

Ion exchange properties of β-eucryptite (LiAlSiO4): EPR investigation on copper-doped single crystals

Investigation of the ion exchange properties of β-eucryptite (LiAlSiO₄) single crystals indicates that it is impossible to substitute Li⁺ by other bigger univalent cations such as Na⁺, K⁺, or Ag⁺. On the contrary, Li⁺ exchange by bivalent cations, Cu²⁺ or Mn²⁺, is very easy. For a general orientation of the crystal with respect to the magnetic field, the EPR spectrum of Cu²⁺ ions in β-eucryptite consists of 12 sharp lines partially superimposed on a broad line. The sharp lines are attributed to isolated copper ions in the conducting channels. Cu²⁺ lies in sixfold coordinated Li″ sites, but not in the fourfold coordinated Li″ sites. The corresponding spin Hamiltonian parameters at T = 140 K are found to be: g_x = 2.362, g_y = 2.340, g_z = 1.990; ∥A_x∥ = 85 × 10^?4cm^?1, ∥A_y∥ = 71 × 10^?4cm^?1, ∥A_z∥ = 203 × 10^?4 cm^?1. The broad line is attributed to clusters of Cu²⁺ located in neighboring Li″ sites.     

On operatorsT such thatf(T) is hypercyclic

We give conditions such that an operator given by the Dunford-Taylor functional calculus is supercyclic or hypercyclic. Indeed, we improve [15, Theorem 1].tbermudeull.esvivienmath.msstate.eduPartially supported by DGICYT Grant PB97-1489 (Spain)     

Magnetic properties of the υj15/2 intruder orbital in the superdeformed minimum of 197Pb

This work has established eight cross-talk transitions between the two signature partner superdeformed (SD) bands in ¹⁹⁷Pb with the EUROBALL IV spectrometer. Directional correlations from oriented states measurements confirm the ΔI = 1 character of these transitions. The flat behaviour of the dynamical moment of inertia and the agreement between the experimental and microscopic HF+BCS values of (g _K - g _R)K/Q ₀ suggest that the configuration of the SD bands is based upon the υ[752]5/2^- neutron intruder orbital. The derived effective spin gyromagnetic factor g _s ^eff is found to be not quenched, and is close to the theoretical g _s ^free value. Received: 14 June 2000 / Accepted: 14 September 2000     

High spin bands in120Xe

High spin states in¹²⁰Xe were populated in the reaction¹⁰⁶Cd(¹⁸O, 4n) at a bombarding. energy of 90 MeV and the subsequent de- excitation was studied using γ- ray spectroscopic methods. New levels and several. spin and parity. assignments were established. The yrast band was observed up to theK ^π=22⁺state with two band crossins athw _c=0.39MeV and 0.45Mev Negative parity levels and a new positive parity band were also identified.     

Use of magnetic fields in electrochemistry: A selected review

Electrochemical reactions are usually thermally activated and submitted to mass-transfer effects. Although classically, enhanced kinetics of an electrochemical reaction is obtained by heating the cell and feeding the reactant by forced convection, other means can be used to improve mass-transfer and charge-transfer. This article shortly reviews the effects of magnetic fields in electrochemistry. Using a static or an alternating magnetic field enables to enhance electrodeposition and electrocatalysis, via improved gas and species convection, electrochemical kinetics, and whole reaction efficiency. Such enhancement can mainly be related to Lorentz and Kelvin forces, magneto-hydrodynamics, chiral-induced spin selectivity, and hyperthermia, these effects being described herein.