Search results for "Condensed Matter::Strongly Correlated Electrons"
showing 10 items of 888 documents
Magnetic resonance imaging of (1)H long lived states derived from parahydrogen induced polarization in a clinical system.
2015
Hyperpolarization is a powerful tool to overcome the low sensitivity of nuclear magnetic resonance (NMR). However, applications are limited due to the short lifetime of this non equilibrium spin state caused by relaxation processes. This issue can be addressed by storing hyperpolarization in slowly decaying singlet spin states which was so far mostly demonstrated for non-proton spin pairs, e.g. 13C-13C. Protons hyperpolarized by parahydrogen induced polarization (PHIP) in symmetrical molecules, are very well suited for this strategy because they naturally exhibit a long-lived singlet state. The conversion of the NMR silent singlet spin state to observable magnetization can be achieved by ma…
Theoretical and experimental study of primary radiation defects in KNbO3 perovskite crystals
2000
Abstract The results of large-scale computer simulations of point defects – F-type electron centers and hole polarons bound to a potassium vacancy – in perovskite KNbO3 crystals are presented. One-site polarons and two-site (molecular) polarons are expected to coexist, both are characterized by close absorption energies around 1 eV. The transient absorption spectra and decay kinetics observed after ns-pulsed electron beam irradiation have been measured for different KNbO3 crystals. The relaxation kinetics of the optical density vary considerably for different impurity concentrations and sample stoichiometries. Experimental data are discussed in the light of the presented calculations.
Spin transition in iron complexes induced by heat, pressure, light and nuclear decay
1988
The phenomenon of temperature-dependent spin transition will be introduced and the numerous chemical and physical influences affecting the spin transition characteristics will be discussed. We shall mainly concentrate on the spin crossover system [Fe(2-pic)3]X2·Sol (2-pic=2-aminomethylpyridine; X=Cl, Br; Sol=C2H5OH, CH3OH) and demonstrate how the behaviour of the spin transition5T2g(Oh)⇌1A1g(Oh) is influenced by substituting the metalion, the non-coordinating anions X, the crystal solvent molecules Sol and by isotopic exchange with H/D and14N/15N. It will also be shown that the spin transition is very susceptible to pressure. A quantitative spin state conversion from low spin to high spin c…
Mössbauer and magnetic studies of mixed-valence linear chain compounds: Na3Fe2S4 and Na3Fe2Se4
1986
Mossbauer and magnetic data establish the two compounds Na3Fe2X4(X=S, Se) as mixed-valence linear chain compounds with rapid valence fluctuation. The compounds exhibit 1-dimensional antiferromagnetic coupling within the chains, and below a critical temperature a 3-dimensional ferrimagnetic ordering between the chains.
Classical-spin approach to a magnetic comb-like chain: application to the two-sublattice chain compound MnMn(CDTA)·7H2O
1991
Abstract We report on the magnetic properties of the two-sublattice manganese chain MnMn(CDTA)·7H 2 O. In view of the structural features, this compound may give rise to a novel type of one-dimensional magnetic network formed by a chain of exchange coupled triangles. A classical-spin model that considers two magnetic sites coupled through two different and isotropic exchange interactions is developed and used in order to analyze the magnetic properties of this compound. The possibility of having a spinfrustration is also examined.
Polarimetry at MAMI
2013
Moller and Mott polarimeters have been compared concerning their measurement accuracy in a dedicated "spin dance" experiment. The results obtained with the different polarimeters at vastly different energy ranges were in agreement with each other within the given systematic uncertainties of a few percent. We discuss investigations of background conditions which may allow to reduce this important contribution to the uncertainties in the Mott polarimeter to a value below 1.0%.
Muon states in metals: Recent progress
1984
We report on our results in two interesting questions related to muon spin rotation studies in condensed matter: (i) energetics of muons in metals, including lattice relaxation and zero point motion in self-trapping phenomena, and (ii) systematics of Knight shifts and hyperfine fields.
Improvement of ESR dosimetry for thermal neutron beams through the addition of gadolinium.
2007
In this paper, the addition of gadolinium is proposed as a useful tool to enhance the electron spin resonance (ESR) sensitivity of organic compounds to thermal neutrons. The target of this work is the detection, through the ESR technique, of the thermal neutron fluence in a mixed field of photons and neutrons. Gadolinium was chosen because it has a very high capture cross section to thermal neutrons; its nuclear reaction with thermal neutrons induces complex inner shell transitions that generate, besides other particles, Auger electrons, which in turn release their energy in the neighborhood (only several nanometers) of the place of reaction. Gadolinium was added to two organic molecules: a…
State-of-the-art density matrix renormalization group and coupled cluster theory studies of the nitrogen binding curve.
2004
We study the nitrogen binding curve with the density matrix renormalization group (DMRG) and single-reference and multireference coupled cluster (CC) theory. Our DMRG calculations use up to 4000 states and our single-reference CC calculations include up to full connected hextuple excitations. Using the DMRG, we compute an all-electron benchmark nitrogen binding curve, at the polarized, valence double-zeta level (28 basis functions), with an estimated accuracy of 0.03mE_h. We also assess the performance of more approximate DMRG and CC theories across the nitrogen curve. We provide an analysis of the relative strengths and merits of the DMRG and CC theory under different correlation condition…
Efficient photo-thermal activation of gold nanoparticle-doped polymer plasmonic switches
2012
International audience; We report on the photo-thermal activation of dielectric loaded plasmonic switches comprised of gold nanoparticle-doped polymer deposited onto a gold film. The plasmonic switches rely on a multi-mode interferometer design and are fabricated by electron beam lithography applied to a positive resin doped with gold nanoparticles at a volume ratio of 0.52%. A cross-bar switching is obtained at telecom wavelengths by pumping the devices with a visible beam having a frequency within the localized surface plasmon resonance band of the embedded nanoparticles. By comparing the switching performances of doped and undoped devices, we show that for the modest doping level we cons…