Near-field mechanism of photoluminescence excitation in quantum well heterostructures

We report a study into the process of energy transfer between quantum wells divided by 30-nm-thick opaque barriers. It was experimentally observed that the intensity of a photoluminescence signal from a quantum well increased by 15% under resonant excitation of exciton transition in the adjacent quantum well. The quantum wells were 30 nm apart. A radiative mechanism of energy transfer in the near-field region of emitting exciton is proposed. Within this theoretical model, the efficiency of the energy transfer decreases by a power law with greater distance between the quantum wells. The theory is found to be in qualitative agreement with the experimental results.     

Synthesis and X‐ray study of cis and trans isomers of 6‐cyano‐2‐oxa‐10‐thia‐1‐phosphabicyclo[4.4.0]decane‐1‐oxide

Intramolecular cyclization of bis(3‐chloropropyl)‐diethoxythiophosphorylacetonitrile 7, taking place under distillation in vacuo, yields 6‐cyano‐2‐oxa‐10‐thia‐1‐phosphabicyclo[4.4.0]decane‐1‐oxide 10 as a mixture of cis and trans isomers in a 2.3:1 ratio. The isomers were separated chromatographically. For both isomers, single crystals with nonequivalent enantiomeric ratios were obtained under crystallization. The structures of both isomers of bicyclophostone 10 are confirmed by X‐ray study of single crystals. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:163–170, 2000     

A convenient one‐pot synthesis of 1,2‐azaphospholanium salts

A novel facile one‐pot synthesis of the 1,2‐azaphospholanes by intramolecular alkylation of 3‐halopropyl amides of tricoordinate phosphorus has been suggested. Using this method, a series of the differently N‐substituted 1,2‐azaphospholanium salts were synthesized. 3‐Aminopropylphosphine oxides were obtained by hydrolysis of the salts. A probable mechanism of the 1,2‐azaphospholanium salts formation is discussed. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:596–602, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10209     

New Nabokoite-like Phases ACu7TeO4(SO4)5Cl (A=Na,K, Rb,Cs) with Decorated and Distorted Square Kagome Lattices

A new family of compounds ACu₇TeO₄(SO₄)₅Cl (A=Na, K, Rb, Cs) isostructural to mineral Nabokoite (K species) was synthesized by solid state and gas transport reactions in sealed ampoules and characterized in measurements of magnetization and specific heat in a wide temperature range. These complex compounds are of the utmost interest as a testing playground to study the properties of quasi-two-dimensional magnets with a square kagome lattice geometry. A quantum ground state of such a corner-sharing network is a spin liquid. Unlike idealized grid analyzed in numerous models, the square kagome lattice in nabokoites is wavy and distorted being composed of versatile triangles. Moreover, it contains “excessive” decorating magnetic ions, which makes magnetism of these objects even more complicated. The interaction of these decorating ions through virtual excitations of the square kagome lattice is accompanied by the formation of a long-range magnetic order coexisting with the spin liquid.