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991.
Meriem Benmelouka Johan Van Tol Alain Borel Saritha Nellutla Marc Port Lothar Helm Louis‐Claude Brunel André E. Merbach 《Helvetica chimica acta》2009,92(11):2173-2185
An electron paramagnetic resonance (EPR) study of glasses and magnetically dilute powders of [Gd(DTPA)(H2O)]2?, [Gd(DOTA)(H2O)]?, and macromolecular gadolinate(1?) complexes P792 was carried out at the X‐ and Q‐bands and at 240 GHz (DTPA=diethylenetriaminepentaacetato; DOTA=1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetato). The results show that the zero‐field splitting (ZFS) parameters for these complexes are quite different in a powder as compared to the frozen aqueous solution. In several complexes, an inversion of the sign of the axial component D of the zero field splitting is observed, indicating a significant structural change. In contrary to what was expected, powder samples obtained by lyophilization do not allow a more precise determination of the static ZFS parameters. The results obtained in glasses are more relevant to the problem of electron spin relaxation in aqueous solution than those obtained from powders. 相似文献
992.
We study cold heteronuclear atom-ion collisions by immersing a trapped single ion into an ultracold atomic cloud. Using ultracold atoms as reaction targets, our measurement is sensitive to elastic collisions with extremely small energy transfer. The observed energy-dependent elastic atom-ion scattering rate deviates significantly from the prediction of Langevin but is in full agreement with the quantum mechanical cross section. Additionally, we characterize inelastic collisions leading to chemical reactions at the single particle level and measure the energy-dependent reaction rate constants. The reaction products are identified by in-trap mass spectrometry, revealing the branching ratio between radiative and nonradiative charge exchange processes. 相似文献
993.
V. S. Varadarajan Jukka T. Virtanen 《P-Adic Numbers, Ultrametric Analysis, and Applications》2010,2(2):157-174
It is well known that at distances shorter than Planck length, no length measurements are possible. The Volovich hypothesis
asserts that at sub-Planckian distances and times, spacetime itself has a non-Archimedean geometry. We discuss the structure
of elementary particles, their classification, and their conformal symmetry under this hypothesis. Specifically, we investigate
the projective representations of the p-adic Poincaré and Galilean groups, using a new variant of the Mackey machine for projective unitary representations of semidirect
products of locally compact and second countable (lcsc) groups. We construct the conformal spacetime over p-adic fields and discuss the imbedding of the p-adic Poincaré group into the p-adic conformal group. Finally, we show that the massive and the so called eventually masssive particles of the Poincaré group
do not have conformal symmetry. The whole picture bears a close resemblance to what happens over the field of real numbers,
but with some significant variations. 相似文献
994.
Maya Bar Sadan Markus Heidelmann Lothar Houben Reshef Tenne 《Applied Physics A: Materials Science & Processing》2009,96(2):343-348
The characterization of nanostructures to the atomic dimensions becomes more important, as devices based on a single particle
are being produced. In particular, inorganic nanotubes were shown to host interesting properties making them excellent candidates
for various devices. The WS2 nanotubes outperform the bulk in their mechanical properties offering numerous applications especially as part of high strength
nanocomposites. In contrast, their electrical properties are less remarkable. The structure–function relationship can be investigated
by aberration-corrected high-resolution transmission electron microscopy (HRTEM), which enables the insight into their atomic
structure as well as performing spectroscopic measurements down to the atomic scale. In the present work, the deciphering
of atomic structure and the chiral angle of the different shells in a multiwall WS2 nanotube is demonstrated. In certain cases,
the helicity of the structure can also be deduced. Finally, first electron energy loss spectra (EELS) of a single tube are
presented, acquired by a new acquisition technique that allows for high spatial resolution (denoted StripeSTEM). The measured
band gap values correspond with the values found in literature for thin films, obtained by spectroscopic techniques, and are
higher than the values resulting from STM measurements. 相似文献
995.
Tero T. Heikkilä Mikhail Silaev Pauli Virtanen F. Sebastian Bergeret 《Progress in Surface Science》2019,94(3):100540
A ferromagnetic insulator (FI) attached to a conventional superconductor (S) changes drastically the properties of the latter. Specifically, the exchange field at the FI/S interface leads to a splitting of the superconducting density of states. If S is a superconducting film, thinner than the superconducting coherence length, the modification of the density of states occurs over the whole sample. The coexistence of the exchange splitting and superconducting correlations in S/FI structures leads to striking transport phenomena that are of interest for applications in thermoelectricity, superconducting spintronics and radiation sensors. Here we review the most recent progress in understanding the transport properties of FI/S structures by presenting a complete theoretical framework based on the quasiclassical kinetic equations. We discuss the coupling between the electronic degrees of freedom, charge, spin and energy, under non-equilibrium conditions and its manifestation in thermoelectricity and spin-dependent transport. 相似文献
996.
We study the Riemann-Hilbert problem of finding φ, ψ ∈ Hp such that their nontangential boundary values satisfy the equation
where
is a given 2π-periodic continuous function. We prove the nonexistence of nontrivial solutions for a wide class of continuous
vanishing complex-valued coefficients a. 相似文献
997.
Takao Kobayasi Stanley Mroczkowski James F. Owen Lothar H. Brixner 《Journal of luminescence》1980,21(3):247-257
An investigation of the relevant parameters for broadly tunable lasers utilizing the efficient, broad-band 5d → 4f emission in a number of Eu2+ doped metal fluorides, chlorides, and fluoro-chlorides has been performed. Results of measurements of absorption and emission spectra, quantum efficiencies, and fluorescence lifetimes in MF2 and MCl2 (M = Ca, Ba, Sr) and MFCl (M = Ba, Sr) are presented. A calculation of the pump energy threshold for laser action in CaF2 : Eu2+ based on our spectroscopic data is made. Although the estimation indicated that laser threshold in CaF2 : Eu can be easily achieved, strong excited-state absorption in this system was found to prohibit laser oscillation. 相似文献
998.
999.
Weber L Domke I Rausch A Chrostowska A Dargelos A 《Dalton transactions (Cambridge, England : 2003)》2004,(14):2188-2191
Reaction of 2-cyano-1,3,2-diazaborole tBuNCH=CHN(tBu)BCN (2) with half an equivalent of isopropyllithium afforded compound tBuNCH=CHN(tBu)BC(iPr=N-BN(tBu)CH=CHNtBu (7). In contrast to this, a 1:1 stoichiometry of the reactants led to tBuNCH=CHN(tBu)BiPr (6) as the product of a nucleophilic substitution process at the boron atom. Similarly, regardless of the molar ratio of reactants employed, treatment of 2 with cyclopropyllithium, isobutyllithium or phenyllithium afforded solely substitution products tBuNCH=CHN(tBu)BR [R =cPr (12); Ph (13); iBu (14)]. 相似文献
1000.
Attaching a superconductor in good contact with a normal metal gives rise to a proximity effect where the superconducting
correlations leak into the normal metal. An additional contact close to the first one makes it possible to carry a supercurrent
through the metal. Forcing this supercurrent flow along with an additional quasiparticle current from one or many normal-metal
reservoirs leads many interesting effects. The supercurrent can be used to tune the local energy distribution function of
the electrons. This mechanism also leads to finite thermoelectric effects even in the presence of electron–hole symmetry.
Here we review these effects and discuss to which extent the existing observations of thermoelectric effects in metallic samples
can be explained through the use of the dirty limit quasiclassical theory.
PACS 74.25.Fy; 73.23.-b; 74.45.+c; 74.40.+k 相似文献