Search results for "electrons"
showing 10 items of 1325 documents
Probing Quantum Frustrated Systems via Factorization of the Ground State
2009
The existence of definite orders in frustrated quantum systems is related rigorously to the occurrence of fully factorized ground states below a threshold value of the frustration. Ground-state separability thus provides a natural measure of frustration: strongly frustrated systems are those that cannot accommodate for classical-like solutions. The exact form of the factorized ground states and the critical frustration are determined for various classes of nonexactly solvable spin models with different spatial ranges of the interactions. For weak frustration, the existence of disentangling transitions determines the range of applicability of mean-field descriptions in biological and physica…
Quark structure of the $$\chi _{\mathrm{c}}(3P)$$ and X(4274) resonances and their strong and radiative decays
2020
AbstractWe calculate the masses of $$\chi _{\mathrm{c}}(3P)$$χc(3P) states with threshold corrections in a coupled-channel model. The model was recently applied to the description of the properties of $$\chi _{\mathrm{c}}(2P)$$χc(2P) and $$\chi _{\mathrm{b}}(3P)$$χb(3P) multiplets (Ferretti and Santopinto in Phys Lett B 789:550, 2019]. We also compute the open-charm strong decay widths of the $$\chi _{\mathrm{c}}(3P)$$χc(3P) states and their radiative transitions. According to our predictions, the $$\chi _{\mathrm{c}}(3P)$$χc(3P) states should be dominated by the charmonium core, but they may also show small meson-meson components. The X(4274) is interpreted as a $$c {{\bar{c}}}$$cc¯$$\chi …
Exclusive c → s, d Semileptonic Decays of Spin-1/2 and Spin-3/2 cb Baryons
2013
We present results for exclusive semileptonic decay widths of ground state spin-$1/2$ and spin-$3/2$ $cb$ baryons corresponding to a $c\to s, d$ transition at the quark level. The relevance of hyperfine mixing in spin-1/2 $cb$ baryons is shown. Our form factors are compatible with heavy quark spin symmetry constraints obtained in the infinite heavy quark mass limit.
Free Charge Carriers in Mixed Valency Oxides as Possible Mediators of Magnetoelectric Effect
2009
We show, that in a substance with mixed-valence ions, which can supply free carriers and have electric dipole and spin moments, three types of long-range order (ferromagnetic, ferroelectric and magnetoelectric (ME)) can occur at low temperatures. The origin of the effect is that free charge carriers can mediate the multiferroic behavior via spin – spin (RKKY), dipole-dipole and dipole - spin interactions. We show that there is an optimal carrier concentration, at which the strength of ME interaction is maximal and comparable to that of RKKY interaction. Our analysis shows that disorder and finite conductivity in the above substances does not suppress multiferroic effects.
Low energy electrons and swift ion track structure in PADC
2015
The current work aims at providing an accurate description of the ion track-structure in poly-allyl dyglycol carbonate (PADC) by using an up-to-date Monte-Carlo code-called TILDA-V (a French acronym for Transport d'Ions Lourds Dans l'Aqua & Vivo). In this simulation the ion track-structure in PADC is mainly described in terms of ejected electrons with a particular attention done to the Low Energy Electrons (LEEs). After a brief reminder of the most important channels through which LEEs are prone to break a chemical bond, we will report on the simulated energetic distributions of LEEs along an ion track in PADC for particular incident energies located on both sides of the Bragg-peak position…
Exposure of -alanine and -ammonium tartrate ESR dosimeters to thermal neutrons: Experiments and Monte Carlo simulations
2008
Abstract Electron spin resonance solid state dosimetry with alanine and ammonium tartrate pellets is a valuable tool in both medical and industrial applications when dealing with photon and charged particle beams. Its use in neutron beams is limited by the low nuclear cross section values of atoms in the pellets. Addition of boron (10B) or gadolinium ( Gd 2 O 3 ) , known to have high neutron capture cross sections, has been proposed to improve neutron sensitivity. In this paper we present the results of an experimental study concerning neutron sensitivity vs. gadolinium concentration in dosimeter mixtures, with the aim of optimizing mixture composition and maximizing the electron spin resol…
Photoabsorption and MXCD in photoemission microscopy for characterisation of advanced materials
1999
Abstract We applied chemical and magnetic sensitive photoemission electron microscopy (PEEM) to investigate surfaces of advanced materials. PEEM at low photon energies provides a high spatial resolution, but suffers from the lack of information about the chemical composition of the imaged surface. Such information can be obtained by PEEM via tuning the photon energy to X-ray absorption edges. To apply spectromicroscopy we acquired and subtracted microscopic images using photon energies just below and at the edges. The resulting difference gives a micro-image of the lateral distribution of a specific element. Microspectroscopy is performed by recording the intensity of secondary electrons in…
Mechanisms of interference of p-diphenols with the Trinder reaction
2020
p-Diphenols, such as homogentisic acid, gentisic acid, etamsylate, and calcium dobesilate, interfere with diagnostic tests utilizing the Trinder reaction but the mechanisms of these effects are not fully understood. We observed substantial differences both in oxidation of p-diphenols by horseradish peroxidase and their influence on oxidation of 4-aminoantipyrine and various phenolic substrates. Homogentisic acid was rapidly oxidized by the enzyme and completely blocked chromophore formation. Enzymatic oxidation of the remaining p-diphenols was slow and they only moderately inhibited chromophore formation. However, in the presence of standard substrates all tested p-diphenols were rapidly co…
Long-Range Order Induced by Intrinsic Repulsion on an Insulating Substrate
2015
An ordered arrangement of molecular stripes with equidistant appearance is formed upon the adsorption of 3-hydroxybenzoic acid onto calcite (10.4) held at room temperature. In a detailed analysis of the next-neighbor stripe distances measured in noncontact atomic force microscopy images at various molecular coverages, we compare the observed stripe arrangement with a random arrangement of noninteracting stripes. The experimentally obtained distance distribution deviates substantially from what is expected for a random distribution of noninteracting stripes, providing direct evidence for the existence of a repulsive interaction between the stripes. At low molecular coverage, where the averag…
Electron-phonon heat transport in degenerate Si at low temperatures
2004
The thermal conductance between electrons and phonons in a solid state system becomes comparatively weak at sub‐Kelvin temperatures. In this work five batches of thin heavily doped silicon‐on‐insulator samples with the electron concentration in the range of 2.0–16 × 1019 cm–3 were studied. Below 1 K all the samples were in the dirty limit of the thermal electron‐phonon coupling, where the thermal phonon wavelength exceeds the electron mean free path. The heat flow between electrons and phonons is proportional to (T6e–T6ph), where Te (Tph) is the electron (phonon) temperature. The constant of proportionality of the heat flow strongly depends on the electron concentration and its magnitude is…