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Helium Temperatures (helium + temperature)

Distribution by Scientific Domains

Physics and Astronomy	50%

Selected Abstracts

New results on characterization of highly transparent nanocrystalline C-modification Lu2O3 nanocrystalline ceramics: room-temperature tunable CW laser action of Yb3+ ions under LD-pumping and the propagation kinetics of non-equilibrium acoustic phonons

LASER PHYSICS LETTERS, Issue 8 2006
A. A. Kaminskii
Abstract We report on the first achievement of CW oscillation in Yb3+:Lu2O3 ceramic lasers (2F5/2 , 2F7/2 channel) under LD-pumping at 0.976 µm wavelength, as well as present of the thickness of grain boundary layers in Lu2O3 ceramics was estimated under non-equilibrium acoustic phonon propagation kinetics at helium temperature (2.4,3.8 K). (© 2006 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

Microcircuit tailoring in ferromagnetic semiconductor (Ga,Mn)As

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003
T. Figielski
Abstract In order to search for novel giant-magnetoresistance systems, we fabricated and investigated narrow constrictions in the layers of the ferromagnetic semiconductor (Ga,Mn)As. We found that constrictions a few hundred nanometers wide, tailored by means of the electron-beam lithography and wet etching, were not conducting at liquid helium temperatures unless illuminated, probably due to the trapping action of surface states appearing on an extra surface area denuded by the etching. To avoid this, we used selective implantation of oxygen ions into the ferromagnetic layer to tailor the constrictions. We have shown that such an implantation inactivates Mn acceptors in the layer and destroys ferromagnetism. We propose an application of oxygen ion implantation as a method of fabricating microcircuits in future spin electronics based on Mn-containing III,V semiconductor compounds. [source]

Luminescent properties of PP and LDPE films and rods doped with the Eu(III)-La(III) complex

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 1 2006
Roman Pogreb
Abstract The work is devoted to luminescent properties of trivalent lanthanide complexes dispersed in thermoplastic host matrices. Polyethylene films and polypropylene-rods, both doped with these complexes, were manufactured using an extrusion technique. Two kinds of dopants were used: Eu(III)-thenoyltrifluoroacetone-1,10-phenanthroline complex (1) and Eu(III)-La(III)-1,10-phenanthroline complex (2). Absorption, excitation, emission spectra and lifetime of luminescence were studied. The impact of the polymer matrix on the emission spectra was investigated. Emission spectra of the films were studied at room and helium temperatures. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) surface mapping showed that in the Eu(III)-La(III) complex europium forms islands (clusters) with a dimension of 1,µm, whereas lanthanum was dispersed more uniformly in the polymer matrix. Dependence of emission intensity on the excitation was determined. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Excited-state structure by time-resolved X-ray diffraction

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 2 2002
Christopher D. Kim
X-ray crystallography has traditionally been limited to the study of the ground-state structure of molecules and solids. Recent technical advances are removing this limitation as demonstrated here by a time-resolved stroboscopic study of the photo-induced 50,µs lifetime excited triplet state of the [Pt2(pop)4]4, ion [pop = pyrophosphate, (H2P2O5)2,], performed at helium temperatures with synchrotron radiation. The shortening of the Pt,Pt bond by 0.28,(9),Å upon excitation is compatible with the proposed mechanism involving promotion of a Pt,Pt antibonding d,* electron to a weakly bonding p orbital. The contraction is accompanied by a 3° molecular rotation. The time-resolved diffraction technique described here is applicable to reversible light-driven processes in the crystalline solid state. [source]