Manipulation of the spin memory of electrons in n-GaAs.

PubMed

Dzhioev, R I; Korenev, V L; Merkulov, I A; Zakharchenya, B P; Gammon, D; Efros, Al L; Katzer, D S

2002-06-24

We report on the optical manipulation of the electron spin relaxation time in a GaAs-based heterostructure. Experimental and theoretical study shows that the average electron spin relaxes through hyperfine interaction with the lattice nuclei, and that the rate can be controlled by electron-electron interactions. This time has been changed from 300 ns down to 5 ns by variation of the laser frequency. This modification originates in the optically induced depletion of an n-GaAs layer.

Angular distribution and polarization of X-ray radiation in highly charged He-like ions: hyperfine-induced transition

NASA Astrophysics Data System (ADS)

Chen, Zhan-Bin; Dong, Chen-Zhong

2018-06-01

The angular distribution and polarization properties of the X-rays produced by the hyperfine-induced transition are investigated within a fully relativistic distorted-wave approximation. The calculations are performed for the 1 s2 p 3/2 3P2 F i = 3/2 → 1 s 2 1S0 F f = 1/2 component of the Kα 1 decay for highly charged He-like 119Sn48+ and 207Tl79+ ions with nuclear spin I = 1/2 following impact excitations by an un-polarized and a completely longitudinally-polarized electron beam, respectively. The Breit interaction and mutipole mixing between the leading M2 decay and the hyperfine-induced E1 decay corrections to both linear and circular polarizations of the emitted X-ray radiations are evaluated. All these effects are found to be significant and may potentially explain the disagreement between the theories and experiments related to the polarization properties of the X-ray radiation.

Nuclear spin warm up in bulk n -GaAs

NASA Astrophysics Data System (ADS)

Kotur, M.; Dzhioev, R. I.; Vladimirova, M.; Jouault, B.; Korenev, V. L.; Kavokin, K. V.

2016-08-01

We show that the spin-lattice relaxation in n -type insulating GaAs is dramatically accelerated at low magnetic fields. The origin of this effect, which cannot be explained in terms of well-known diffusion-limited hyperfine relaxation, is found in the quadrupole relaxation, induced by fluctuating donor charges. Therefore, quadrupole relaxation, which governs low field nuclear spin relaxation in semiconductor quantum dots, but was so far supposed to be harmless to bulk nuclei spins in the absence of optical pumping, can be studied and harnessed in the much simpler model environment of n -GaAs bulk crystal.

Electron-Nuclear Quantum Information Processing

DTIC Science & Technology

2008-11-13

quantum information processing that exploits the anisotropic hyperfine coupling. This scheme enables universal control over a 1-electron, N-nuclear spin...exploits the anisotropic hyperfine coupling. This scheme enables universal control over a 1-electron, N-nuclear spin system, addressing only a...sample of irradiated malonic acid. (a) Papers published in peer-reviewed journals (N/A for none) Universal control of nuclear spins via anisotropic

[Hyperfine structure analysis in magnetic resonance spectroscopy: from astrophysical measurements towards endogenous biosensors in human tissue].

PubMed

Schröder, Leif

2007-01-01

The hyperfine interaction of two spins is a well studied effect in atomic systems. Magnetic resonance experiments demonstrate that the detectable dipole transitions are determined by the magnetic moments of the constituents and the external magnetic field. Transferring the corresponding quantum mechanics to molecular bound nuclear spins allows for precise prediction of NMR spectra obtained from metabolites in human tissue. This molecular hyperfine structure has been neglected so far in in vivo NMR spectroscopy but contains useful information, especially when studying molecular dynamics. This contribution represents a review of the concept of applying the Breit-Rabi formalism to coupled nuclear spins and discusses the immobilization of different metabolites in anisotropic tissue revealed by 1H NMR spectra of carnosine, phosphocreatine and taurine. Comparison of atomic and molecular spin systems allows for statements on the biological constraints for direct spin-spin interactions. Moreover, the relevance of hyperfine effects on the line shapes of multiplets of indirectly-coupled spin systems with more than two constituents can be predicted by analyzing quantum mechanical parameters. As an example, the superposition of eigenstates of the A MX system of adenosine 5'-triphosphate and its application for better quantification of 31P-NMR spectra will be discussed.

Electron paramagnetic resonance of a 10B-containing heterocyclic radical

NASA Astrophysics Data System (ADS)

Eaton, Sandra S.; Ngendahimana, Thacien; Eaton, Gareth R.; Jupp, Andrew R.; Stephan, Douglas W.

2018-05-01

Electron paramagnetic resonance measurements for a 10B-containing heterocyclic phenanthrenedione radical, (C6F5)2B(O2C14H8), were made at X-band in 9:1 toluene:dichloromethane from 10 to 293 K and in toluene from 180 to 293 K. In well-deoxygenated 0.1 mM toluene solution at room temperature hyperfine couplings to 10B, four pairs of protons and five pairs of fluorines contribute to a continuous wave spectrum with many resolved lines. Hyperfine couplings were adjusted to provide the best fit for spectra of the radical enriched in 10B and the analogous radical synthesized with 10,11B in natural abundance, resulting in small refinements of the hyperfine coupling constants previously reported for the natural abundance sample. Electron spin relaxation rates at temperatures between 15 and 293 K were similar for samples containing 10B and natural isotope abundance. Analysis of electron spin echo envelope modulation and hyperfine correlation spectroscopy data at 80 K found Axx = -7.5 ± 0.3, Ayy = -8.5 ± 0.3, and Azz = -10.8 ± 0.3 MHz for 11B, which indicates small spin density on the boron. The spin echo and hyperfine spectroscopy data for the 10B -containing radical are consistent with the factor of 2.99 smaller hyperfine values for 10B than for 11B.

Electrical detection of nuclear spins in organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Malissa, H.; Kavand, M.; Waters, D. P.; Lupton, J. M.; Vardeny, Z. V.; Saam, B.; Boehme, C.

2014-03-01

We present pulsed combined electrically detected electron paramagnetic and nuclear magnetic resonance experiments on MEH-PPV OLEDs. Spin dynamics in these structures are governed by hyperfine interactions between charge carriers and the surrounding hydrogen nuclei, which are abundant in these materials. Hyperfine coupling has been observed by monitoring the device current during coherent spin excitation. Electron spin echoes (ESEs) are detected by applying one additional readout pulse at the time of echo formation. This allows for the application of high-resolution spectroscopy based on ESE detection, such as electron spin echo envelope modulation (ESEEM) and electron nuclear double resonance (ENDOR) available for electrical detection schemes. We conduct electrically detected ESEEM and ENDOR experiments and show how hyperfine interactions in MEH-PPV with and without deuterated polymer side groups can be observed by device current measurements. We acknowledge support by the Department of Energy, Office of Basic Energy Sciences under Award #DE-SC0000909.

Ab initio calculations of torsionally mediated hyperfine splittings in E states of acetaldehyde

NASA Astrophysics Data System (ADS)

Xu, Li-Hong; Reid, E. M.; Guislain, B.; Hougen, J. T.; Alekseev, E. A.; Krapivin, I.

2017-12-01

Quantum chemistry packages can be used to predict with reasonable accuracy spin-rotation hyperfine interaction constants for methanol, which contains one methyl-top internal rotor. In this work we use one of these packages to calculate components of the spin-rotation interaction tensor for acetaldehyde. We then use torsion-rotation wavefunctions obtained from a fit to the acetaldehyde torsion-rotation spectrum to calculate the expected magnitude of hyperfine splittings analogous to those observed at relatively high J values in the E symmetry states of methanol. We find that theory does indeed predict doublet splittings at moderate J values in the acetaldehyde torsion-rotation spectrum, which closely resemble those seen in methanol, but that the factor of three decrease in hyperfine spin-rotation constants compared to methanol puts the largest of the acetaldehyde splittings a factor of two below presently available Lamb-dip resolution.

Gd(III) complexes as paramagnetic tags: Evaluation of the spin delocalization over the nuclei of the ligand

NASA Astrophysics Data System (ADS)

Collauto, A.; Feintuch, A.; Qi, M.; Godt, A.; Meade, T.; Goldfarb, D.

2016-02-01

Complexes of the Gd(III) ion are currently being established as spin labels for distance determination in biomolecules by pulse dipolar spectroscopy. Because Gd(III) is an f ion, one expects electron spin density to be localized on the Gd(III) ion - an important feature for the mentioned application. Most of the complex ligands have nitrogens as Gd(III) coordinating atoms. Therefore, measurement of the 14N hyperfine coupling gives access to information on the localization of the electron spin on the Gd(III) ion. We carried out W-band, 1D and 2D 14N and 1H ENDOR measurements on the Gd(III) complexes Gd-DOTA, Gd-538, Gd-595, and Gd-PyMTA that serve as spin labels for Gd-Gd distance measurements. The obtained 14N spectra are particularly well resolved, revealing both the hyperfine and nuclear quadrupole splittings, which were assigned using 2D Mims ENDOR experiments. Additionally, the spectral contributions of the two different types of nitrogen atoms of Gd-PyMTA, the aliphatic N atom and the pyridine N atom, were distinguishable. The 14N hyperfine interaction was found to have a very small isotropic hyperfine component of -0.25 to -0.37 MHz. Furthermore, the anisotropic hyperfine interactions with the 14N nuclei and with the non-exchangeable protons of the ligands are well described by the point-dipole approximation using distances derived from the crystal structures. We therefore conclude that the spin density is fully localized on the Gd(III) ion and that the spin density distribution over the nuclei of the ligands is rightfully ignored when analyzing distance measurements.

Non-flipping 13C spins near an NV center in diamond: hyperfine and spatial characteristics by density functional theory simulation of the C510[NV]H252 cluster

NASA Astrophysics Data System (ADS)

Nizovtsev, A. P.; Kilin, S. Ya; Pushkarchuk, A. L.; Pushkarchuk, V. A.; Kuten, S. A.; Zhikol, O. A.; Schmitt, S.; Unden, T.; Jelezko, F.

2018-02-01

Single NV centers in diamond coupled by hyperfine interaction (hfi) to neighboring 13C nuclear spins are now widely used in emerging quantum technologies as elements of quantum memory adjusted to a nitrogen-vacancy (NV) center electron spin qubit. For nuclear spins with low flip-flop rate, single shot readout was demonstrated under ambient conditions. Here we report on a systematic search for such stable NV-13C systems using density functional theory to simulate the hfi and spatial characteristics of all possible NV-13C complexes in the H-terminated cluster C510[NV]-H252 hosting the NV center. Along with the expected stable ‘NV-axial-13C’ systems wherein the 13C nuclear spin is located on the NV axis, we found for the first time new families of positions for the 13C nuclear spin exhibiting negligible hfi-induced flipping rates due to near-symmetric local spin density distribution. Spatially, these positions are located in the diamond bilayer passing through the vacancy of the NV center and being perpendicular to the NV axis. Analysis of available publications showed that, apparently, some of the predicted non-axial near-stable NV-13C systems have already been observed experimentally. A special experiment performed on one of these systems confirmed the prediction made.

133Cs-NMR study on aligned powder of competing spin chain compound Cs2Cu2Mo3O12

NASA Astrophysics Data System (ADS)

Yagi, A.; Matsui, K.; Goto, T.; Hase, M.; Sasaki, T.

2018-03-01

S = 1/2 competing spin chain compound Cs2Cu2Mo3O12 has two dominant exchange interactions of the nearest neighbouring ferromagnetic J 1 = 93 K and the second nearest neighbouring antiferromagnetic J 2 = +33 K, and is expected to show the nematic Tomonaga-Luttinger liquid (TLL) state under high magnetic field region. The recent theoretical study by Sato et al. has shown that in the nematic TLL state, the spin fluctuations are expected to be highly anisotropic, that is, its transverse component is suppressed. Our previous NMR study on the present system showed that the dominant contribution to nuclear spin relaxation comes from the longitudinal component. In order to conclude that the transverse component of spin fluctuations is suppressed, the knowledge of hyperfine coupling is indispensable. This article is solely devoted to investigate the hyperfine coupling of 133Cs-NMR site to prove that the anisotropic part of hyperfine coupling, which connects the nuclear spin relaxation with the transverse spin fluctuations is considerably large to be A an = +770 Oe/μB.

Collective nuclear stabilization in single quantum dots by noncollinear hyperfine interaction

NASA Astrophysics Data System (ADS)

Yang, Wen; Sham, L. J.

2012-06-01

We present a theory of efficient suppression of the collective nuclear spin fluctuation, which prolongs the electron spin coherence time through the noncollinear hyperfine interaction between the nuclear spins and the hole spin. This provides a general paradigm to combat decoherence by direct control of environmental noise, and a possible solution to the puzzling observation of symmetric broadening of the absorption spectra in two recent experiments [Xu , Nature (London)NATUAS0028-083610.1038/nature08120 459, 1105 (2009) and Latta , Nature Phys.1745-247310.1038/nphys1363 5, 758 (2009)].

Hyperfine excitation of CH in collisions with atomic and molecular hydrogen

NASA Astrophysics Data System (ADS)

Dagdigian, Paul J.

2018-04-01

We investigate here the excitation of methylidene (CH) induced by collisions with atomic and molecular hydrogen (H and H2). The hyperfine-resolved rate coefficients were obtained from close coupling nuclear-spin-free scattering calculations. The calculations are based upon recent, high-accuracy calculations of the CH(X2Π)-H(2S) and CH(X2Π)-H2 potential energy surfaces. Cross-sections and rate coefficients for collisions with atomic H, para-H2, and ortho-H2 were computed for all transitions between the 32 hyperfine levels for CH(X2Π) involving the n ≤ 4 rotational levels for temperatures between 10 and 300 K. These rate coefficients should significantly aid in the interpretation of astronomical observations of CH spectra. As a first application, the excitation of CH is simulated for conditions in typical molecular clouds.

The hyperfine structure in the rotational spectra of D{sub 2}{sup 17}O and HD{sup 17}O: Confirmation of the absolute nuclear magnetic shielding scale for oxygen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Puzzarini, Cristina, E-mail: cristina.puzzarini@unibo.it; Cazzoli, Gabriele; Harding, Michael E.

2015-03-28

Guided by theoretical predictions, the hyperfine structures of the rotational spectra of mono- and bideuterated-water containing {sup 17}O have been experimentally investigated. To reach sub-Doppler resolution, required to resolve the hyperfine structure due to deuterium quadrupole coupling as well as to spin-rotation (SR) and dipolar spin-spin couplings, the Lamb-dip technique has been employed. The experimental investigation and in particular, the spectral analysis have been supported by high-level quantum-chemical computations employing coupled-cluster techniques and, for the first time, a complete experimental determination of the hyperfine parameters involved was possible. The experimentally determined {sup 17}O spin-rotation constants of D{sub 2}{sup 17}O andmore » HD{sup 17}O were used to derive the paramagnetic part of the corresponding nuclear magnetic shielding constants. Together with the computed diamagnetic contributions as well as the vibrational and temperature corrections, the latter constants have been employed to confirm the oxygen nuclear magnetic shielding scale, recently established on the basis of spin-rotation data for H{sub 2}{sup 17}O [Puzzarini et al., J. Chem. Phys. 131, 234304 (2009)].« less

Characterization of the hyperfine interaction of the excited D50 state of Eu3 +:Y2SiO5

NASA Astrophysics Data System (ADS)

Cruzeiro, Emmanuel Zambrini; Etesse, Jean; Tiranov, Alexey; Bourdel, Pierre-Antoine; Fröwis, Florian; Goldner, Philippe; Gisin, Nicolas; Afzelius, Mikael

2018-03-01

We characterize the europium (Eu3 +) hyperfine interaction of the excited state (D50) and determine its effective spin Hamiltonian parameters for the Zeeman and quadrupole tensors. An optical free induction decay method is used to measure all hyperfine splittings under a weak external magnetic field (up to 10 mT) for various field orientations. On the basis of the determined Hamiltonian, we discuss the possibility to predict optical transition probabilities between hyperfine levels for the F70⟷D50 transition. The obtained results provide necessary information to realize an optical quantum memory scheme which utilizes long spin coherence properties of 3 + 151Eu :Y2SiO5 material under external magnetic fields.

Laser-stimulated electric quadrupole transitions in the molecular hydrogen ion H2+

NASA Astrophysics Data System (ADS)

Korobov, V. I.; Danev, P.; Bakalov, D.; Schiller, S.

2018-03-01

Molecular hydrogen ions are of metrological relevance due to the possibility of precise theoretical evaluation of their spectrum and of external-field-induced shifts. We report the results of the calculations of the rate of laser-induced electric quadrupole transitions between a large set of ro-vibrational states of H2+. The hyperfine and Zeeman structure of the E 2 transition spectrum and the effects of the laser polarization are treated in detail. The treatment is generally applicable to molecules in 2Σ states. We also present the nuclear spin-electron spin-coupling constants, computed with a precision ten times higher than previously obtained.

Stabilization of the electron-nuclear spin orientation in quantum dots by the nuclear quadrupole interaction.

PubMed

Dzhioev, R I; Korenev, V L

2007-07-20

The nuclear quadrupole interaction eliminates the restrictions imposed by hyperfine interaction on the spin coherence of an electron and nuclei in a quantum dot. The strain-induced nuclear quadrupole interaction suppresses the nuclear spin flip and makes possible the zero-field dynamic nuclear polarization in self-organized InP/InGaP quantum dots. The direction of the effective nuclear magnetic field is fixed in space, thus quenching the magnetic depolarization of the electron spin in the quantum dot. The quadrupole interaction suppresses the zero-field electron spin decoherence also for the case of nonpolarized nuclei. These results provide a new vision of the role of the nuclear quadrupole interaction in nanostructures: it elongates the spin memory of the electron-nuclear system.

Stabilization of the Electron-Nuclear Spin Orientation in Quantum Dots by the Nuclear Quadrupole Interaction

NASA Astrophysics Data System (ADS)

Dzhioev, R. I.; Korenev, V. L.

2007-07-01

The nuclear quadrupole interaction eliminates the restrictions imposed by hyperfine interaction on the spin coherence of an electron and nuclei in a quantum dot. The strain-induced nuclear quadrupole interaction suppresses the nuclear spin flip and makes possible the zero-field dynamic nuclear polarization in self-organized InP/InGaP quantum dots. The direction of the effective nuclear magnetic field is fixed in space, thus quenching the magnetic depolarization of the electron spin in the quantum dot. The quadrupole interaction suppresses the zero-field electron spin decoherence also for the case of nonpolarized nuclei. These results provide a new vision of the role of the nuclear quadrupole interaction in nanostructures: it elongates the spin memory of the electron-nuclear system.

Extending the electron spin coherence time of atomic hydrogen by dynamical decoupling.

PubMed

Mitrikas, George; Efthimiadou, Eleni K; Kordas, George

2014-02-14

We study the electron spin decoherence of encapsulated atomic hydrogen in octasilsesquioxane cages induced by the (1)H and (29)Si nuclear spin bath. By applying the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence we significantly suppress the low-frequency noise due to nuclear spin flip-flops up to the point where a maximum T2 = 56 μs is observed. Moreover, dynamical decoupling with the CPMG sequence reveals the existence of two other sources of decoherence: first, a classical magnetic field noise imposed by the (1)H nuclear spins of the cage organic substituents, which can be described by a virtual fluctuating magnetic field with the proton Larmor frequency, and second, decoherence due to anisotropic hyperfine coupling between the electron and the inner (29)Si spins of the cage.

Electron-nuclear coherent spin oscillations probed by spin-dependent recombination

NASA Astrophysics Data System (ADS)

Azaizia, S.; Carrère, H.; Sandoval-Santana, J. C.; Ibarra-Sierra, V. G.; Kalevich, V. K.; Ivchenko, E. L.; Bakaleinikov, L. A.; Marie, X.; Amand, T.; Kunold, A.; Balocchi, A.

2018-04-01

We demonstrate the triggering and detection of coherent electron-nuclear spin oscillations related to the hyperfine interaction in Ga deep paramagnetic centers in GaAsN by band-to-band photoluminescence without an external magnetic field. In contrast to other point defects such as Cr4 + in SiC, Ce3 + in yttrium aluminum garnet crystals, nitrogen-vacancy centers in diamond, and P atoms in silicon, the bound-electron spin in Ga centers is not directly coupled to the electromagnetic field via the spin-orbit interaction. However, this apparent drawback can be turned into an advantage by exploiting the spin-selective capture of conduction band electrons to the Ga centers. On the basis of a pump-probe photoluminescence experiment we measure directly in the temporal domain the hyperfine constant of an electron coupled to a gallium defect in GaAsN by tracing the dynamical behavior of the conduction electron spin-dependent recombination to the defect site. The hyperfine constants and the relative abundance of the nuclei isotopes involved can be determined without the need of an electron spin resonance technique and in the absence of any magnetic field. Information on the nuclear and electron spin relaxation damping parameters can also be estimated from the oscillation amplitude decay and the long-time-delay behavior.

Semiclassical description of hyperfine interaction in calculating chemically induced dynamic nuclear polarization in weak magnetic fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Purtov, P.A.; Salikhov, K.M.

1987-09-01

Semiclassical HFI description is applicable to calculating the integral CIDNP effect in weak fields. The HFI has been calculated for radicals with sufficiently numerous magnetically equivalent nuclei (n greater than or equal to 5) in satisfactory agreement with CIDNP calculations based on quantum-mechanical description of radical-pair spin dynamics.

The tetrahydrobiopterin radical with high- and low-spin heme in neuronal nitric oxide synthase -- a new indicator of the extent of NOS coupling

PubMed Central

Krzyaniak, Matthew D.; Cruce, Alex A.; Vennam, Preethi; Lockart, Molly; Berka, Vladimir; Tsai, Ah-Lim; Bowman, Michael K.

2016-01-01

Reaction intermediates trapped during the single-turnover reaction of the neuronal ferrous nitric oxide synthase oxygenase domain (Fe(II)nNOSOX) show four EPR spectra of free radicals. Fully-coupled nNOSOX with cofactor (tetrahydrobiopterin, BH4) and substrate (l-arginine) forms the typical BH4 cation radical with an EPR spectrum ~4.0 mT wide and hyperfine tensors similar to reports for a biopterin cation radical in inducible NOSOX (iNOSOX). With excess thiol, nNOSox lacking BH4 and l-arg is known to produce superoxide. In contrast, we find that nNOSOX with BH4 but no l-arg forms two radicals with rather different, fast (~ 250 µs at 5 K) and slower (~ 500 µs at 20 K), electron spin relaxation rates and a combined ~7.0 mT wide EPR spectrum. Rapid freeze-quench CW- and pulsed-EPR measurements are used to identify these radicals and their origin. These two species are the same radical with identical nuclear hyperfine couplings, but with spin-spin couplings to high-spin (4.0 mT component) or low-spin (7.0 mT component) Fe(III) heme. Uncoupled reactions of nNOS leave the enzyme in states that can be chemically reduced to sustain unregulated production of NO and reactive oxygen species in ischemia-reperfusion injury. The broad EPR signal is a convenient indicator of uncoupled nNOS reactions producing low-spin Fe(III) heme. PMID:27989753

Hyperfine interaction and its effects on spin dynamics in organic solids

NASA Astrophysics Data System (ADS)

Yu, Z. G.; Ding, Feizhi; Wang, Haobin

2013-05-01

Hyperfine interaction (HFI) and spin-orbit coupling are two major sources that affect electron spin dynamics. Here we present a systematic study of the HFI and its role in organic spintronic applications. For electron spin dynamics in disordered π-conjugated organics, the HFI can be characterized by an effective magnetic field whose modular square is a weighted sum of contact and dipolar contributions. We determine the effective HFI fields of some common π-conjugated organics studied in the literature via first-principles calculations. Most of them are found to be less than 2 mT. While the H atoms are the major source of the HFI in organics containing only the C and H atoms, many organics contain other nuclear spins, such as Al and N in tris-(8-hydroxyquinoline) aluminum, that contribute to the total HFI. Consequently, the deuteration effect on the HFI in the latter may be much weaker than in the former. The HFI gives rise to multiple resonance peaks in electron spin resonance. In disordered organic solids, these individual resonances are unresolved, leading to a broad peak whose width is proportional to the effective HFI field. As electrons hop among adjacent organic molecules, they experience a randomly varying local HFI field, inducing electron spin relaxation and diffusion. This is analyzed rigorously based on master equations. Electron spin relaxation undergoes a crossover along the ratio between the electron hopping rate η¯ and the Larmor frequency Ω of the HFI field. The spin relaxation rate increases (decreases) with η¯ when η¯≪Ω (η¯≫Ω). A coherent beating of electron spin at Ω is possible when the external field is small compared to the HFI. In this regime, the magnetic field is found to enhance the spin relaxation.

Nuclear spin circular dichroism.

PubMed

Vaara, Juha; Rizzo, Antonio; Kauczor, Joanna; Norman, Patrick; Coriani, Sonia

2014-04-07

Recent years have witnessed a growing interest in magneto-optic spectroscopy techniques that use nuclear magnetization as the source of the magnetic field. Here we present a formulation of magnetic circular dichroism (CD) due to magnetically polarized nuclei, nuclear spin-induced CD (NSCD), in molecules. The NSCD ellipticity and nuclear spin-induced optical rotation (NSOR) angle correspond to the real and imaginary parts, respectively, of (complex) quadratic response functions involving the dynamic second-order interaction of the electron system with the linearly polarized light beam, as well as the static magnetic hyperfine interaction. Using the complex polarization propagator framework, NSCD and NSOR signals are obtained at frequencies in the vicinity of optical excitations. Hartree-Fock and density-functional theory calculations on relatively small model systems, ethene, benzene, and 1,4-benzoquinone, demonstrate the feasibility of the method for obtaining relatively strong nuclear spin-induced ellipticity and optical rotation signals. Comparison of the proton and carbon-13 signals of ethanol reveals that these resonant phenomena facilitate chemical resolution between non-equivalent nuclei in magneto-optic spectra.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, S. L., E-mail: shuch@ist.hokudai.ac.jp; Takayama, J.; Murayama, A.

Time-resolved optical spin orientation spectroscopy was employed to investigate the temperature-dependent electron spin injection in In{sub 0.1}Ga{sub 0.9}As quantum well (QW) and In{sub 0.5}Ga{sub 0.5}As quantum dots (QDs) tunnel-coupled nanostructures with 4, 6, and 8 nm-thick GaAs barriers. The fast picosecond-ranged spin injection from QW to QD excited states (ES) was observed to speed up with temperature, as induced by pronounced longitudinal-optical (LO)-phonon-involved multiple scattering process, which contributes to a thermally stable and almost fully spin-conserving injection within 5–180 K. The LO-phonon coupling was also found to cause accelerated electron spin relaxation of QD ES at elevated temperature, mainly via hyperfine interactionmore » with random nuclear field.« less

Fluctuating hyperfine interactions: an updated computational implementation

NASA Astrophysics Data System (ADS)

Zacate, M. O.; Evenson, W. E.

2015-04-01

The stochastic hyperfine interactions modeling library (SHIML) is a set of routines written in the C programming language designed to assist in the analysis of stochastic models of hyperfine interactions. The routines read a text-file description of the model, set up the Blume matrix, upon which the evolution operator of the quantum mechanical system depends, and calculate the eigenvalues and eigenvectors of the Blume matrix, from which theoretical spectra of experimental techniques can be calculated. The original version of SHIML constructs Blume matrices applicable for methods that measure hyperfine interactions with only a single nuclear spin state. In this paper, we report an extension of the library to provide support for methods such as Mössbauer spectroscopy and nuclear resonant scattering of synchrotron radiation, which are sensitive to interactions with two nuclear spin states. Examples will be presented that illustrate the use of this extension of SHIML to generate Mössbauer spectra for polycrystalline samples under a number of fluctuating hyperfine field models.

Magnitude of finite-nucleus-size effects in relativistic density functional computations of indirect NMR nuclear spin-spin coupling constants.

PubMed

Autschbach, Jochen

2009-09-14

A spherical Gaussian nuclear charge distribution model has been implemented for spin-free (scalar) and two-component (spin-orbit) relativistic density functional calculations of indirect NMR nuclear spin-spin coupling (J-coupling) constants. The finite nuclear volume effects on the hyperfine integrals are quite pronounced and as a consequence they noticeably alter coupling constants involving heavy NMR nuclei such as W, Pt, Hg, Tl, and Pb. Typically, the isotropic J-couplings are reduced in magnitude by about 10 to 15 % for couplings between one of the heaviest NMR nuclei and a light atomic ligand, and even more so for couplings between two heavy atoms. For a subset of the systems studied, viz. the Hg atom, Hg(2) (2+), and Tl--X where X=Br, I, the basis set convergence of the hyperfine integrals and the coupling constants was monitored. For the Hg atom, numerical and basis set calculations of the electron density and the 1s and 6s orbital hyperfine integrals are directly compared. The coupling anisotropies of TlBr and TlI increase by about 2 % due to finite-nucleus effects.

Calculation of the spin-polarized electronic structure of an interstitial iron impurity in silicon

NASA Astrophysics Data System (ADS)

Katayama-Yoshida, H.; Zunger, Alex

1985-06-01

We apply our self-consistent, all-electron, spin-polarized Green's-function method within an impurity-centered, dynamic basis set to study the interstitial iron impurity in silicon. We use two different formulations of the interelectron interactions: the local-spin-density (LSD) formalism and the self-interaction-corrected (SIC) local-spin-density (SIC-LSD) formalism. We find that the SIC-LSD approach is needed to obtain the correct high-spin ground state of Si:Fe+. We propose a quantitative explanation to the observed donor ionization energy and the high-spin ground states for Si:Fe+ within the SIC-LSD approach. For both Si:Fe0 and Si:Fe+, this approach leads to a hyperfine field, contact spin density, and ionization energy in better agreement with experiments than the simple LSD approach. The apparent dichotomy between the covalently delocalized nature of Si:Fe as suggested on the one hand by its reduced hyperfine field (relative to the free atom) and extended spin density and by the occurrence of two closely spaced, stable charge states (within 0.4 eV) and on the other hand by the atomically localized picture (suggested, for example, by the stability of a high-spin, ground-state configuration) is resolved. We find a large reduction in the hyperfine field and contact spin density due to the covalent hybridization between the impurity 3d orbitals and the tails of the delocalized sp3 hybrid orbitals of the surrounding silicon atoms. Using the calculated results, we discuss (i) the underlying mechanism for the stability and plurality of charged states, (ii) the covalent reduction in the hyperfine field, (iii) the remarkable constancy of the impurity Mössbauer isomer shift for different charged states, (iv) comparison with the multiple charged states in ionic crystals, and (v) some related speculation about the mechanism of (Fe2+/Fe3+) oxidation-reduction ionizations in heme proteins and electron-transporting biological systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

van den Berg, R.; Brandino, G. P.; El Araby, O.

In this study, we introduce an integrability-based method enabling the study of semiconductor quantum dot models incorporating both the full hyperfine interaction as well as a mean-field treatment of dipole-dipole interactions in the nuclear spin bath. By performing free induction decay and spin echo simulations we characterize the combined effect of both types of interactions on the decoherence of the electron spin, for external fields ranging from low to high values. We show that for spin echo simulations the hyperfine interaction is the dominant source of decoherence at short times for low fields, and competes with the dipole-dipole interactions atmore » longer times. On the contrary, at high fields the main source of decay is due to the dipole-dipole interactions. In the latter regime an asymmetry in the echo is observed. Furthermore, the non-decaying fraction previously observed for zero field free induction decay simulations in quantum dots with only hyperfine interactions, is destroyed for longer times by the mean-field treatment of the dipolar interactions.« less

Competing interactions in semiconductor quantum dots

DOE PAGES

van den Berg, R.; Brandino, G. P.; El Araby, O.; ...

2014-10-14

In this study, we introduce an integrability-based method enabling the study of semiconductor quantum dot models incorporating both the full hyperfine interaction as well as a mean-field treatment of dipole-dipole interactions in the nuclear spin bath. By performing free induction decay and spin echo simulations we characterize the combined effect of both types of interactions on the decoherence of the electron spin, for external fields ranging from low to high values. We show that for spin echo simulations the hyperfine interaction is the dominant source of decoherence at short times for low fields, and competes with the dipole-dipole interactions atmore » longer times. On the contrary, at high fields the main source of decay is due to the dipole-dipole interactions. In the latter regime an asymmetry in the echo is observed. Furthermore, the non-decaying fraction previously observed for zero field free induction decay simulations in quantum dots with only hyperfine interactions, is destroyed for longer times by the mean-field treatment of the dipolar interactions.« less

Quenching of dynamic nuclear polarization by spin-orbit coupling in GaAs quantum dots.

PubMed

Nichol, John M; Harvey, Shannon P; Shulman, Michael D; Pal, Arijeet; Umansky, Vladimir; Rashba, Emmanuel I; Halperin, Bertrand I; Yacoby, Amir

2015-07-17

The central-spin problem is a widely studied model of quantum decoherence. Dynamic nuclear polarization occurs in central-spin systems when electronic angular momentum is transferred to nuclear spins and is exploited in quantum information processing for coherent spin manipulation. However, the mechanisms limiting this process remain only partially understood. Here we show that spin-orbit coupling can quench dynamic nuclear polarization in a GaAs quantum dot, because spin conservation is violated in the electron-nuclear system, despite weak spin-orbit coupling in GaAs. Using Landau-Zener sweeps to measure static and dynamic properties of the electron spin-flip probability, we observe that the size of the spin-orbit and hyperfine interactions depends on the magnitude and direction of applied magnetic field. We find that dynamic nuclear polarization is quenched when the spin-orbit contribution exceeds the hyperfine, in agreement with a theoretical model. Our results shed light on the surprisingly strong effect of spin-orbit coupling in central-spin systems.

Control of coherence among the spins of a single electron and the three nearest neighbor {sup 13}C nuclei of a nitrogen-vacancy center in diamond

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shimo-Oka, T.; Miwa, S.; Suzuki, Y.

2015-04-13

Individual nuclear spins in diamond can be optically detected through hyperfine couplings with the electron spin of a single nitrogen-vacancy (NV) center; such nuclear spins have outstandingly long coherence times. Among the hyperfine couplings in the NV center, the nearest neighbor {sup 13}C nuclear spins have the largest coupling strength. Nearest neighbor {sup 13}C nuclear spins have the potential to perform fastest gate operations, providing highest fidelity in quantum computing. Herein, we report on the control of coherences in the NV center where all three nearest neighbor carbons are of the {sup 13}C isotope. Coherence among the three and fourmore » qubits are generated and analyzed at room temperature.« less

Stochastic hyperfine interactions modeling library-Version 2

NASA Astrophysics Data System (ADS)

Zacate, Matthew O.; Evenson, William E.

2016-02-01

The stochastic hyperfine interactions modeling library (SHIML) provides a set of routines to assist in the development and application of stochastic models of hyperfine interactions. The library provides routines written in the C programming language that (1) read a text description of a model for fluctuating hyperfine fields, (2) set up the Blume matrix, upon which the evolution operator of the system depends, and (3) find the eigenvalues and eigenvectors of the Blume matrix so that theoretical spectra of experimental techniques that measure hyperfine interactions can be calculated. The optimized vector and matrix operations of the BLAS and LAPACK libraries are utilized. The original version of SHIML constructed and solved Blume matrices for methods that measure hyperfine interactions of nuclear probes in a single spin state. Version 2 provides additional support for methods that measure interactions on two different spin states such as Mössbauer spectroscopy and nuclear resonant scattering of synchrotron radiation. Example codes are provided to illustrate the use of SHIML to (1) generate perturbed angular correlation spectra for the special case of polycrystalline samples when anisotropy terms of higher order than A22 can be neglected and (2) generate Mössbauer spectra for polycrystalline samples for pure dipole or pure quadrupole transitions.

Kobayashi-Kondo-Maskawa-'t Hooft interaction in pentaquarks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dmitrasinovic, V.

2005-05-01

We review critically the predictions of pentaquarks in the quark model, in particular, those based on the flavor-spin-dependent (Glozman-Riska) hyperfine interaction and the color-spin (one-gluon-exchange Fermi-Breit) one. We include the antiquark interactions and find that: (1) the exotic SU(3) multiplets are not substantially affected in the flavor-spin model, whereas some of the nonexotic multiplets are; and (2) the variational upper bound on the {xi}{sup --}-{theta}{sup +} mass difference in the color-spin hyperfine interaction model is substantially reduced. This leads us to the U{sub A}(1) symmetry breaking Kobayashi-Kondo-Maskawa-'tHooft interaction. We discuss some of its phenomenological consequences for pentaquarks.

Dark state polarizing a nuclear spin in the vicinity of a nitrogen-vacancy center

NASA Astrophysics Data System (ADS)

Wang, Yang-Yang; Qiu, Jing; Chu, Ying-Qi; Zhang, Mei; Cai, Jianming; Ai, Qing; Deng, Fu-Guo

2018-04-01

The nuclear spin in the vicinity of a nitrogen-vacancy (NV) center possesses long coherence time and convenient manipulation assisted by the strong hyperfine interaction with the NV center. It is suggested for the subsequent quantum information storage and processing after appropriate initialization. However, current experimental schemes are either sensitive to the inclination and magnitude of the magnetic field or require thousands of repetitions to achieve successful realization. Here, we propose a method to polarize a 13C nuclear spin in the vicinity of an NV center via a dark state. We demonstrate theoretically and numerically that it is robust to polarize various nuclear spins with different hyperfine couplings and noise strengths.

Multiple stable states of a periodically driven electron spin in a quantum dot using circularly polarized light

NASA Astrophysics Data System (ADS)

Korenev, V. L.

2011-06-01

The periodical modulation of circularly polarized light with a frequency close to the electron spin resonance frequency induces a sharp change of the single electron spin orientation. Hyperfine interaction provides a feedback, thus fixing the precession frequency of the electron spin in the external and the Overhauser field near the modulation frequency. The nuclear polarization is bidirectional and the electron-nuclear spin system (ENSS) possesses a few stable states. The same physics underlie the frequency-locking effect for two-color and mode-locked excitations. However, the pulsed excitation with mode-locked laser brings about the multitudes of stable states in ENSS in a quantum dot. The resulting precession frequencies of the electron spin differ in these states by the multiple of the modulation frequency. Under such conditions ENSS represents a digital frequency converter with more than 100 stable channels.

Dynamic nuclear spin polarization in the resonant laser excitation of an InGaAs quantum dot.

PubMed

Högele, A; Kroner, M; Latta, C; Claassen, M; Carusotto, I; Bulutay, C; Imamoglu, A

2012-05-11

Resonant optical excitation of lowest-energy excitonic transitions in self-assembled quantum dots leads to nuclear spin polarization that is qualitatively different from the well-known optical orientation phenomena. By carrying out a comprehensive set of experiments, we demonstrate that nuclear spin polarization manifests itself in quantum dots subjected to finite external magnetic field as locking of the higher energy Zeeman transition to the driving laser field, as well as the avoidance of the resonance condition for the lower energy Zeeman branch. We interpret our findings on the basis of dynamic nuclear spin polarization originating from noncollinear hyperfine interaction and find excellent agreement between experiment and theory. Our results provide evidence for the significance of noncollinear hyperfine processes not only for nuclear spin diffusion and decay, but also for buildup dynamics of nuclear spin polarization in a coupled electron-nuclear spin system.

Frequency swept microwaves for hyperfine decoupling and time domain dynamic nuclear polarization

PubMed Central

Hoff, Daniel E.M.; Albert, Brice J.; Saliba, Edward P.; Scott, Faith J.; Choi, Eric J.; Mardini, Michael; Barnes, Alexander B.

2015-01-01

Hyperfine decoupling and pulsed dynamic nuclear polarization (DNP) are promising techniques to improve high field DNP NMR. We explore experimental and theoretical considerations to implement them with magic angle spinning (MAS). Microwave field simulations using the high frequency structural simulator (HFSS) software suite are performed to characterize the inhomogeneous phase independent microwave field throughout a 198 GHz MAS DNP probe. Our calculations show that a microwave power input of 17 W is required to generate an average EPR nutation frequency of 0.84 MHz. We also present a detailed calculation of microwave heating from the HFSS parameters and find that 7.1% of the incident microwave power contributes to dielectric sample heating. Voltage tunable gyrotron oscillators are proposed as a class of frequency agile microwave sources to generate microwave frequency sweeps required for the frequency modulated cross effect, electron spin inversions, and hyperfine decoupling. Electron spin inversions of stable organic radicals are simulated with SPINEVOLUTION using the inhomogeneous microwave fields calculated by HFSS. We calculate an electron spin inversion efficiency of 56% at a spinning frequency of 5 kHz. Finally, we demonstrate gyrotron acceleration potentials required to generate swept microwave frequency profiles for the frequency modulated cross effect and electron spin inversions. PMID:26482131

Frequency swept microwaves for hyperfine decoupling and time domain dynamic nuclear polarization.

PubMed

Hoff, Daniel E M; Albert, Brice J; Saliba, Edward P; Scott, Faith J; Choi, Eric J; Mardini, Michael; Barnes, Alexander B

2015-11-01

Hyperfine decoupling and pulsed dynamic nuclear polarization (DNP) are promising techniques to improve high field DNP NMR. We explore experimental and theoretical considerations to implement them with magic angle spinning (MAS). Microwave field simulations using the high frequency structural simulator (HFSS) software suite are performed to characterize the inhomogeneous phase independent microwave field throughout a 198GHz MAS DNP probe. Our calculations show that a microwave power input of 17W is required to generate an average EPR nutation frequency of 0.84MHz. We also present a detailed calculation of microwave heating from the HFSS parameters and find that 7.1% of the incident microwave power contributes to dielectric sample heating. Voltage tunable gyrotron oscillators are proposed as a class of frequency agile microwave sources to generate microwave frequency sweeps required for the frequency modulated cross effect, electron spin inversions, and hyperfine decoupling. Electron spin inversions of stable organic radicals are simulated with SPINEVOLUTION using the inhomogeneous microwave fields calculated by HFSS. We calculate an electron spin inversion efficiency of 56% at a spinning frequency of 5kHz. Finally, we demonstrate gyrotron acceleration potentials required to generate swept microwave frequency profiles for the frequency modulated cross effect and electron spin inversions. Copyright © 2015 Elsevier Inc. All rights reserved.

An analysis of the rotational, fine and hyperfine effects in the (0, 0) band of the A7Π- X7Σ + transition of manganese monohydride, MnH

NASA Astrophysics Data System (ADS)

Gengler, Jamie J.; Steimle, Timothy C.; Harrison, Jeremy J.; Brown, John M.

2007-02-01

High-resolution (±0.003 cm -1), laser induced fluorescence (LIF) spectra of a supersonic molecular beam sample of manganese monohydride, MnH, have been recorded in the 17500-17800 cm -1 region of the (0, 0) band of the A7Π- X7Σ + system. The low- N branch features were modeled successfully by inclusion of the magnetic hyperfine mixings of spin components within a given low- N rotational level using a traditional 'effective' Hamiltonian approach. An improved set of spectroscopic constants has been extracted and compared with those from previous analyses. The optimum optical features for future optical Stark and Zeeman measurements are identified.

Spin-orbit-coupled Bose-Einstein condensates of rotating polar molecules

NASA Astrophysics Data System (ADS)

Deng, Y.; You, L.; Yi, S.

2018-05-01

An experimental proposal for realizing spin-orbit (SO) coupling of pseudospin 1 in the ground manifold 1Σ (υ =0 ) of (bosonic) bialkali polar molecules is presented. The three spin components are composed of the ground rotational state and two substates from the first excited rotational level. Using hyperfine resolved Raman processes through two select excited states resonantly coupled by a microwave, an effective coupling between the spin tensor and linear momentum is realized. The properties of Bose-Einstein condensates for such SO-coupled molecules exhibiting dipolar interactions are further explored. In addition to the SO-coupling-induced stripe structures, the singly and doubly quantized vortex phases are found to appear, implicating exciting opportunities for exploring novel quantum physics using SO-coupled rotating polar molecules with dipolar interactions.

Muon contact hyperfine field in metals: A DFT calculation

NASA Astrophysics Data System (ADS)

Onuorah, Ifeanyi John; Bonfà, Pietro; De Renzi, Roberto

2018-05-01

In positive muon spin rotation and relaxation spectroscopy it is becoming customary to take advantage of density functional theory (DFT) based computational methods to aid the experimental data analysis. DFT-aided muon site determination is especially useful for measurements performed in magnetic materials, where large contact hyperfine interactions may arise. Here we present a systematic analysis of the accuracy of the ab initio estimation of muon's hyperfine contact field on elemental transition metals, performing state-of-the-art spin-polarized plane-wave DFT and using the projector-augmented pseudopotential approach, which allows one to include the core state effects due to the spin ordering. We further validate this method in not-so-simple, noncentrosymmetric metallic compounds, presently of topical interest for their spiral magnetic structure giving rise to skyrmion phases, such as MnSi and MnGe. The calculated hyperfine fields agree with experimental values in all cases, provided the spontaneous spin magnetization of the metal is well reproduced within the approach. To overcome the known limits of the conventional mean-field approximation of DFT on itinerant magnets, we adopt the so-called reduced Stoner theory [L. Ortenzi et al., Phys. Rev. B 86, 064437 (2012), 10.1103/PhysRevB.86.064437]. We establish the accuracy of the estimated muon contact field in metallic compounds with DFT and our results show improved agreement with experiments compared to those of earlier publications.

A portable version of the program of nettar and villafranca for the simulation of electron paramagnetic resonance spectra of powders

NASA Astrophysics Data System (ADS)

Soulié, Edgar; Gaugenot, Jacques

1995-04-01

Nettar and Villafranca wrote in the FORTRAN programming language a computer program which simulates the electron paramagnetic resonance (EPR) spectra of powders (Journal of Magnetic Resonance, vol. 64 (1985) pp. 61-65). The spin Hamiltonian which their program can handle includes the Zeeman electronic interaction, the fine interaction up to the sixth order in the electron spin, a general hyperfine interaction, an isotropic nuclear Zeeman term; anisotropic ligand hyperfine terms are treated to first order in perturbation. The above Hamiltonian, without the ligand hyperfine terms, is treated exactly, i.e. the resonance equation for a transition between states labeled i and j is solved numerically: h.ν=Ei(H)-Ej(H).

Separating hyperfine from spin-orbit interactions in organic semiconductors by multi-octave magnetic resonance using coplanar waveguide microresonators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joshi, G.; Miller, R.; Ogden, L.

2016-09-05

Separating the influence of hyperfine from spin-orbit interactions in spin-dependent carrier recombination and dissociation processes necessitates magnetic resonance spectroscopy over a wide range of frequencies. We have designed compact and versatile coplanar waveguide resonators for continuous-wave electrically detected magnetic resonance and tested these on organic light-emitting diodes. By exploiting both the fundamental and higher-harmonic modes of the resonators, we cover almost five octaves in resonance frequency within a single setup. The measurements with a common π-conjugated polymer as the active material reveal small but non-negligible effects of spin-orbit interactions, which give rise to a broadening of the magnetic resonance spectrummore » with increasing frequency.« less

Hyperfine state entanglement of spinor BEC and scattering atom

NASA Astrophysics Data System (ADS)

Li, Zhibing; Bao, Chengguang; Zheng, Wei

2018-05-01

Condensate of spin-1 atoms frozen in a unique spatial mode may possess large internal degrees of freedom. The scattering amplitudes of polarized cold atoms scattered by the condensate are obtained with the method of fractional parentage coefficients that treats the spin degrees of freedom rigorously. Channels with scattering cross sections enhanced by the square of the atom number of the condensate are found. Entanglement between the condensate and the propagating atom can be established by scattering. Entanglement entropy is analytically obtained for arbitrary initial states. Our results also give a hint for the establishment of quantum thermal ensembles in the hyperfine space of spin states.

Hyperfine field and magnetic structure in the B phase of CeCoIn5

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graf, Matthias J; Curro, Nicholas J; Young, Ben - Li

2009-01-01

We re-analyze Nuclear Magnetic Resonance (NMR) spectra observed at low temperatures and high magnetic fields in the field-induced B-phase of CeCoIn{sub 5}. The NMR spectra are consistent with incommensurate antiferromagnetic order of the Ce magnetic moments. However, we find that the spectra of the In(2) sites depend critically on the direction of the ordered moments, the ordering wavevector and the symmetry of the hyperfine coupling to the Ce spins. Assuming isotropic hyperfine coupling, the NMR spectra observed for H {parallel} [100] are consistent with magnetic order with wavevector Q = {pi}(1+{delta}/a, 1/a, 1/c) and Ce moments ordered antiferromagnetically along themore » [100] direction in real space. If the hyperfine coupling has dipolar symmetry, then the NMR spectra require Ce moments along the [001] direction. The dipolar scenario is also consistent with recent neutron scattering measurements that find an ordered moment of 0.15{micro}{sub B} along [001] and Q{sub n} = {pi}(1+{delta}/a, 1+{delta}c, 1/c) with incommensuration {delta} = 0.12 for field H {parallel} [1{bar 1}0]. Using these parameters, we find that the hyperfine field is consistent with both experiments. We speculate that the B phase of CeCoIn{sub 5} represents an intrinsic phase of modulated superconductivity and antiferromagnetism that can only emerge in a highly clean system.« less

Electrical detection of electron-spin-echo envelope modulations in thin-film silicon solar cells

NASA Astrophysics Data System (ADS)

Fehr, M.; Behrends, J.; Haas, S.; Rech, B.; Lips, K.; Schnegg, A.

2011-11-01

Electrically detected electron-spin-echo envelope modulations (ED-ESEEM) were employed to detect hyperfine interactions between nuclear spins and paramagnetic sites, determining spin-dependent transport processes in multilayer thin-film microcrystalline silicon solar cells. Electrical detection in combination with a modified Hahn-echo sequence was used to measure echo modulations induced by 29Si, 31P, and 1H nuclei weakly coupled to electron spins of paramagnetic sites in the amorphous and microcrystalline solar cell layers. In the case of CE centers in the μc-Si:H i-layer, the absence of 1H ESEEM modulations indicates that the adjacencies of CE centers are depleted from hydrogen atoms. On the basis of this result, we discuss several models for the microscopic origin of the CE center and conclusively assign those centers to coherent twin boundaries inside of crystalline grains in μc-Si:H.

Hyperfine interaction mechanism of magnetic field effects in sequential fluorophore and exciplex fluorescence.

PubMed

Dodin, Dmitry V; Ivanov, Anatoly I; Burshtein, Anatoly I

2013-03-28

The magnetic field effect on the fluorescence of the photoexcited electron acceptor, (1)A∗, and the exciplex, (1)[D(+δ)A(-δ)] formed at contact of (1)A∗ with an electron donor (1)D, is theoretically explored in the framework of Integral Encounter Theory. It is assumed that the excited fluorophore is equilibrated with the exciplex that reversibly dissociates into the radical-ion pair. The magnetic field sensitive stage is the spin conversion in the resulting geminate radical-ion pair, (1, 3)[D(+)...A(-)] that proceeds due to hyperfine interaction. We confirm our earlier conclusion (obtained with a rate description of spin conversion) that in the model with a single nucleus spin 1/2 the magnitude of the Magnetic Field Effect (MFE) also vanishes in the opposite limits of low and high dielectric permittivity of the solvent. Moreover, it is shown that MFE being positive at small hyperfine interaction A, first increases with A but approaching the maximum starts to decrease and even changes the sign.

Hyperfine structure of the MnH X 7Sigma + state: A large gas-to-matrix shift in the Fermi contact interaction

NASA Astrophysics Data System (ADS)

Varberg, Thomas D.; Field, Robert W.; Merer, Anthony J.

1990-06-01

Sub-Doppler spectra of the A 7Π-X 7Σ+ (0,0) band of gas phase MnH near 5680 Å were recorded by intermodulated fluorescence spectroscopy. The spectra reveal hyperfine splittings arising from both the 55Mn and 1H nuclear spins. Internal hyperfine perturbations have been observed between the different spin components of the ground state at low N`. From a preliminary analysis of several rotational lines originating from the isolated and unperturbed F1(J`=3) spin component of the X 7Σ+(N`=0) level, the 55Mn Fermi contact interaction in the ground state has been measured as bF=Aiso =276(1) MHz. This value is 11% smaller than the value obtained by Weltner et al. from an electron-nuclear double resonance (ENDOR) study of MnH in an argon matrix at 4 K. This unprecedented gas-to-matrix shift in the Fermi contact parameter is discussed.

Theory of long-range interactions for Rydberg states attached to hyperfine-split cores

NASA Astrophysics Data System (ADS)

Robicheaux, F.; Booth, D. W.; Saffman, M.

2018-02-01

The theory is developed for one- and two-atom interactions when the atom has a Rydberg electron attached to a hyperfine-split core state. This situation is relevant for some of the rare-earth and alkaline-earth atoms that have been proposed for experiments on Rydberg-Rydberg interactions. For the rare-earth atoms, the core electrons can have a very substantial total angular momentum J and a nonzero nuclear spin I . In the alkaline-earth atoms there is a single (s ) core electron whose spin can couple to a nonzero nuclear spin for odd isotopes. The resulting hyperfine splitting of the core state can lead to substantial mixing between the Rydberg series attached to different thresholds. Compared to the unperturbed Rydberg series of the alkali-metal atoms, the series perturbations and near degeneracies from the different parity states could lead to qualitatively different behavior for single-atom Rydberg properties (polarizability, Zeeman mixing and splitting, etc.) as well as Rydberg-Rydberg interactions (C5 and C6 matrices).

Spin-Orbit Interactions and Quantum Spin Dynamics in Cold Ion-Atom Collisions

NASA Astrophysics Data System (ADS)

Tscherbul, Timur V.; Brumer, Paul; Buchachenko, Alexei A.

2016-09-01

We present accurate ab initio and quantum scattering calculations on a prototypical hybrid ion-atom system Yb+ -Rb, recently suggested as a promising candidate for the experimental study of open quantum systems, quantum information processing, and quantum simulation. We identify the second-order spin-orbit (SO) interaction as the dominant source of hyperfine relaxation in cold Yb+ -Rb collisions. Our results are in good agreement with recent experimental observations [L. Ratschbacher et al., Phys. Rev. Lett. 110, 160402 (2013)] of hyperfine relaxation rates of trapped Yb+ immersed in an ultracold Rb gas. The calculated rates are 4 times smaller than is predicted by the Langevin capture theory and display a weak T-0.3 temperature dependence, indicating significant deviations from statistical behavior. Our analysis underscores the deleterious nature of the SO interaction and implies that light ion-atom combinations such as Yb+ -Li should be used to minimize hyperfine relaxation and decoherence of trapped ions in ultracold atomic gases.

Electrical control of single hole spins in nanowire quantum dots.

PubMed

Pribiag, V S; Nadj-Perge, S; Frolov, S M; van den Berg, J W G; van Weperen, I; Plissard, S R; Bakkers, E P A M; Kouwenhoven, L P

2013-03-01

The development of viable quantum computation devices will require the ability to preserve the coherence of quantum bits (qubits). Single electron spins in semiconductor quantum dots are a versatile platform for quantum information processing, but controlling decoherence remains a considerable challenge. Hole spins in III-V semiconductors have unique properties, such as a strong spin-orbit interaction and weak coupling to nuclear spins, and therefore, have the potential for enhanced spin control and longer coherence times. A weaker hyperfine interaction has previously been reported in self-assembled quantum dots using quantum optics techniques, but the development of hole-spin-based electronic devices in conventional III-V heterostructures has been limited by fabrication challenges. Here, we show that gate-tunable hole quantum dots can be formed in InSb nanowires and used to demonstrate Pauli spin blockade and electrical control of single hole spins. The devices are fully tunable between hole and electron quantum dots, which allows the hyperfine interaction strengths, g-factors and spin blockade anisotropies to be compared directly in the two regimes.

Disorder induced spin coherence in polyfluorene thin film semiconductors

NASA Astrophysics Data System (ADS)

Miller, Richard G.; van Schooten, Kipp; Malissa, Hans; Waters, David P.; Lupton, John M.; Boehme, Christoph

2014-03-01

Charge carrier spins in polymeric organic semiconductors significantly influence magneto-optoelectronic properties of these materials. In particular, spin relaxation times influence magnetoresistance and electroluminescence. We have studied the role of structural and electronic disorder in polaron spin-relaxation times. As a model polymer, we used polyfluorene, which can exist in two distinct morphologies: an amorphous (glassy) and an ordered (beta) phase. The phases can be controlled in thin films by preparation parameters and verified by photoluminescence spectroscopy. We conducted pulsed electrically detected magnetic resonance (pEDMR) measurements to determine spin-dephasing times by transient current measurements under bipolar charge carrier injection conditions and a forward bias. The measurements showed that, contrary to intuition, spin-dephasing times increase with material disorder. We attribute this behavior to a reduction in hyperfine field strength for carriers in the glassy phase due to increased structural disorder in the hydrogenated side chains, leading to longer spin coherence times. We acknowledge support by the Department of Energy, Office of Basic Energy Sciences under Award #DE-SC0000909.

Molecules in high spin states: The millimeter and submillimeter spectrum of the MnS radical (X 6Sigma+)

NASA Astrophysics Data System (ADS)

Thompsen, J. M.; Brewster, M. A.; Ziurys, L. M.

2002-06-01

The pure rotational spectrum of MnS (v=0) in its X 6Sigma+ ground state has been recorded using millimeter and submillimeter direct absorption techniques in the range 160-502 GHz. MnS was synthesized in the gas phase by the reaction of manganese vapor and CS2 in a high-temperature Broida-type oven. Fourteen rotational transitions for this radical were measured, each consisting of six fine-structure components. In the lower rotational lines, hyperfine structure, arising from the 55Mn nuclear spin of 5/2, was also resolved in each spin component. These data were analyzed using a case (b) Hamiltonian, and rotational, fine structure, and hyperfine parameters determined for MnS. In the analysis, the third-order correction to the spin-rotation interaction, gammaS, and the fourth-order spin-spin coupling term, theta, were found necessary for an acceptable fit. The hyperfine constants determined suggest that MnS is more covalent than MnO, but more ionic than MnH. There additionally appears to be considerable sdsigma hybridization in molecular orbital formation for this molecule. Bond lengths of the 3d transition-metal sulfides were compared as well, and those of MnS, CuS, and TiS do not follow the trend of their oxide analogs. This result indicates that there are significant bonding differences between transition-metal sulfides and transition-metal oxides.

Spectrally resolved hyperfine interactions between polaron and nuclear spins in organic light emitting diodes: Magneto-electroluminescence studies

NASA Astrophysics Data System (ADS)

Crooker, S. A.; Liu, F.; Kelley, M. R.; Martinez, N. J. D.; Nie, W.; Mohite, A.; Nayyar, I. H.; Tretiak, S.; Smith, D. L.; Ruden, P. P.

2014-10-01

We use spectrally resolved magneto-electroluminescence (EL) measurements to study the energy dependence of hyperfine interactions between polaron and nuclear spins in organic light-emitting diodes. Using layered devices that generate bright exciplex emission, we show that the increase in EL emission intensity I due to small applied magnetic fields of order 100 mT is markedly larger at the high-energy blue end of the EL spectrum (ΔI/I ˜ 11%) than at the low-energy red end (˜4%). Concurrently, the widths of the magneto-EL curves increase monotonically from blue to red, revealing an increasing hyperfine coupling between polarons and nuclei and directly providing insight into the energy-dependent spatial extent and localization of polarons.

Hyperfine Sublevel Correlation (HYSCORE) Spectra for Paramagnetic Centers with Nuclear Spin I = 1 Having Isotropic Hyperfine Interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maryasov, Alexander G.; Bowman, Michael K.

2004-07-08

It is shown that HYSCORE spectra of paramagnetic centers having nuclei of spin I=1 with isotropic hfi and arbitrary NQI consist of ridges having zero width. A parametric presentation of these ridges is found which shows the range of possible frequencies in the HYSCORE spectrum and aids in spectral assignments and rapid estimation of spin Hamiltonian parameters. An alternative approach for the spectral density calculation is presented that is based on spectral decomposition of the Hamiltonian. Only the eigenvalues of the Hamiltonian are needed in this approach. An atlas of HYSCORE spectra is given in the Supporting Information. This approachmore » is applied to the estimation of the spin Hamiltonian parameters of the oxovanadium-EDTA complex.« less

Hyperfine structure of 2Σ molecules containing alkaline-earth-metal atoms

NASA Astrophysics Data System (ADS)

Aldegunde, Jesus; Hutson, Jeremy M.

2018-04-01

Ultracold molecules with both electron spin and an electric dipole moment offer new possibilities in quantum science. We use density-functional theory to calculate hyperfine coupling constants for a selection of molecules important in this area, including RbSr, LiYb, RbYb, CaF, and SrF. We find substantial hyperfine coupling constants for the fermionic isotopes of the alkaline-earth-metal and Yb atoms. We discuss the hyperfine level patterns and Zeeman splittings expected for these molecules. The results will be important both to experiments aimed at forming ultracold open-shell molecules and to their applications.

Quantum dynamics of nuclear spins and spin relaxation in organic semiconductors

NASA Astrophysics Data System (ADS)

Mkhitaryan, V. V.; Dobrovitski, V. V.

2017-06-01

We investigate the role of the nuclear-spin quantum dynamics in hyperfine-induced spin relaxation of hopping carriers in organic semiconductors. The fast-hopping regime, when the carrier spin does not rotate much between subsequent hops, is typical for organic semiconductors possessing long spin coherence times. We consider this regime and focus on a carrier random-walk diffusion in one dimension, where the effect of the nuclear-spin dynamics is expected to be the strongest. Exact numerical simulations of spin systems with up to 25 nuclear spins are performed using the Suzuki-Trotter decomposition of the evolution operator. Larger nuclear-spin systems are modeled utilizing the spin-coherent state P -representation approach developed earlier. We find that the nuclear-spin dynamics strongly influences the carrier spin relaxation at long times. If the random walk is restricted to a small area, it leads to the quenching of carrier spin polarization at a nonzero value at long times. If the random walk is unrestricted, the carrier spin polarization acquires a long-time tail, decaying as 1 /√{t } . Based on the numerical results, we devise a simple formula describing the effect quantitatively.

Chiral effective-field theory of the nucleon spin structure

NASA Astrophysics Data System (ADS)

Pascalutsa, Vladimir

2017-01-01

I will review the recent chiral EFT calculations of the nucleon (spin) structure functions at low Q2, confronted with the Jefferson Lab measurements. The moments of the structure functions correspond with various polarizabilities, and I will explain why one of them - δLT - is especially interesting. I will also discuss how the spin structure functions at low Q enter in the atomic calculations of the hyperfine splittings and how they are impacting the ongoing experimental program at PSI (Switzerland) to measure the ground-state hyperfine splitting of muonic hydrogen. Partially supported by the Deutsche Forschungsgemeinschaft (DFG) through the Collaborative Research Center SFB 1044 [The Low-Energy Frontier of the Standard Model].

ESR imaging investigations of two-phase systems.

PubMed

Herrmann, Werner; Stösser, Reinhard; Borchert, Hans-Hubert

2007-06-01

The possibilities of electron spin resonance (ESR) and electron spin resonance imaging (ESRI) for investigating the properties of the spin probes TEMPO and TEMPOL in two-phase systems have been examined in the systems water/n-octanol, Miglyol/Miglyol, and Precirol/Miglyol. Phases and regions of the phase boundary could be mapped successfully by means of the isotropic hyperfine coupling constants, and, moreover, the quantification of rotational and lateral diffusion of the spin probes was possible. For the quantitative treatment of the micropolarity, a simplified empirical model was established on the basis of the Nernst distribution and the experimentally determined isotropic hyperfine coupling constants. The model does not only describe the summarized micropolarities of coexisting phases, but also the region of the phase boundary, where solvent molecules of different polarities and tendencies to form hydrogen bonds compete to interact with the NO group of the spin probe. Copyright 2007 John Wiley & Sons, Ltd.

On the exact solvability of the anisotropic central spin model: An operator approach

NASA Astrophysics Data System (ADS)

Wu, Ning

2018-07-01

Using an operator approach based on a commutator scheme that has been previously applied to Richardson's reduced BCS model and the inhomogeneous Dicke model, we obtain general exact solvability requirements for an anisotropic central spin model with XXZ-type hyperfine coupling between the central spin and the spin bath, without any prior knowledge of integrability of the model. We outline basic steps of the usage of the operators approach, and pedagogically summarize them into two Lemmas and two Constraints. Through a step-by-step construction of the eigen-problem, we show that the condition gj‧2 - gj2 = c naturally arises for the model to be exactly solvable, where c is a constant independent of the bath-spin index j, and {gj } and { gj‧ } are the longitudinal and transverse hyperfine interactions, respectively. The obtained conditions and the resulting Bethe ansatz equations are consistent with that in previous literature.

Communication: Spin densities within a unitary group based spin-adapted open-shell coupled-cluster theory: Analytic evaluation of isotropic hyperfine-coupling constants for the combinatoric open-shell coupled-cluster scheme

DOE Office of Scientific and Technical Information (OSTI.GOV)

Datta, Dipayan, E-mail: datta.dipayan@gmail.com; Gauss, Jürgen, E-mail: gauss@uni-mainz.de

We report analytical calculations of isotropic hyperfine-coupling constants in radicals using a spin-adapted open-shell coupled-cluster theory, namely, the unitary group based combinatoric open-shell coupled-cluster (COSCC) approach within the singles and doubles approximation. A scheme for the evaluation of the one-particle spin-density matrix required in these calculations is outlined within the spin-free formulation of the COSCC approach. In this scheme, the one-particle spin-density matrix for an open-shell state with spin S and M{sub S} = + S is expressed in terms of the one- and two-particle spin-free (charge) density matrices obtained from the Lagrangian formulation that is used for calculating themore » analytic first derivatives of the energy. Benchmark calculations are presented for NO, NCO, CH{sub 2}CN, and two conjugated π-radicals, viz., allyl and 1-pyrrolyl in order to demonstrate the performance of the proposed scheme.« less

Molecules in high spin states III: The millimeter/submillimeter-wave spectrum of the MnCl radical (X 7Σ+)

NASA Astrophysics Data System (ADS)

Halfen, D. T.; Ziurys, L. M.

2005-02-01

The pure rotational spectrum of the MnCl radical (X 7Σ+) has been recorded in the range 141-535 GHz using millimeter-submillimeter direct absorption spectroscopy. This work is the first time the molecule has been studied with rotational resolution in its ground electronic state. MnCl was synthesized by the reaction of manganese vapor, produced in a Broida-type oven, with Cl2. Transitions of both chlorine isotopomers were measured, as well as lines originating in several vibrationally excited states. The presence of several spin components and manganese hyperfine interactions resulted in quite complex spectra, consisting of multiple blended features. Because 42 rotational transitions were measured for Mn35Cl over a wide range of frequencies with high signal-to-noise, a very accurate set of rotational, fine structure, and hyperfine constants could be determined with the aid of spectral simulations. Spectroscopic constants were also determined for Mn37Cl and several vibrationally excited states. The values of the spin-rotation and spin-spin parameters were found to be relatively small (γ=11.2658 MHz and λ=1113.10 MHz for Mn35Cl); in the case of λ, excited electronic states contributing to the second-order spin-orbit interaction may be canceling each other. The Fermi contact hyperfine term was found to be large in manganese chloride with bF(Mn35Cl)=397.71 MHz, a result of the manganese 4s character mixing into the 12σ orbital. This orbital is spσ hybridized, and contains some Mn 4pσ character, as well. Hence, it also contributes to the dipolar constant c, which is small and positive for this radical (c=32.35 MHz for Mn35Cl). The hyperfine parameters in MnCl are similar to those of MnH and MnF, suggesting that the bonding in these three molecules is comparable.

Molecules in high spin states III: the millimeter/submillimeter-wave spectrum of the MnCl radical (X (7)Sigma(+)).

PubMed

Halfen, D T; Ziurys, L M

2005-02-01

The pure rotational spectrum of the MnCl radical (X (7)Sigma(+)) has been recorded in the range 141-535 GHz using millimeter-submillimeter direct absorption spectroscopy. This work is the first time the molecule has been studied with rotational resolution in its ground electronic state. MnCl was synthesized by the reaction of manganese vapor, produced in a Broida-type oven, with Cl(2). Transitions of both chlorine isotopomers were measured, as well as lines originating in several vibrationally excited states. The presence of several spin components and manganese hyperfine interactions resulted in quite complex spectra, consisting of multiple blended features. Because 42 rotational transitions were measured for Mn(35)Cl over a wide range of frequencies with high signal-to-noise, a very accurate set of rotational, fine structure, and hyperfine constants could be determined with the aid of spectral simulations. Spectroscopic constants were also determined for Mn(37)Cl and several vibrationally excited states. The values of the spin-rotation and spin-spin parameters were found to be relatively small (gamma=11.2658 MHz and lambda=1113.10 MHz for Mn(35)Cl); in the case of lambda, excited electronic states contributing to the second-order spin-orbit interaction may be canceling each other. The Fermi contact hyperfine term was found to be large in manganese chloride with b(F)(Mn(35)Cl)=397.71 MHz, a result of the manganese 4s character mixing into the 12sigma orbital. This orbital is spsigma hybridized, and contains some Mn 4psigma character, as well. Hence, it also contributes to the dipolar constant c, which is small and positive for this radical (c=32.35 MHz for Mn(35)Cl). The hyperfine parameters in MnCl are similar to those of MnH and MnF, suggesting that the bonding in these three molecules is comparable.

Controlled rephasing of single spin-waves in a quantum memory based on cold atoms

NASA Astrophysics Data System (ADS)

Farrera, Pau; Albrecht, Boris; Heinze, Georg; Cristiani, Matteo; de Riedmatten, Hugues; Quantum Photonics With Solids; Atoms Team

2015-05-01

Quantum memories for light allow a reversible transfer of quantum information between photons and long lived matter quantum bits. In atomic ensembles, this information is commonly stored in the form of single collective spin excitations (spin-waves). In this work we demonstrate that we can actively control the dephasing of the spin-waves created in a quantum memory based on a cold Rb87 atomic ensemble. The control is provided by an external magnetic field gradient, which induces an inhomogeneous broadening of the atomic hyperfine levels. We show that acting on this gradient allows to control the dephasing of individual spin-waves and to induce later a rephasing. The spin-waves are then mapped into single photons, and we demonstrate experimentally that the active rephasing preserves the sub-Poissonian statistics of the retrieved photons. Finally we show that this rephasing control enables the creation and storage of multiple spin-waves in different temporal modes, which can be selectively readout. This is an important step towards the implementation of a functional temporally multiplexed quantum memory for quantum repeaters. We acknowledge support from the ERC starting grant, the Spanish Ministry of Economy and Competitiveness, the Fondo Europeo de Desarrollo Regional, and the International PhD- fellowship program ``la Caixa''-Severo Ochoa @ICFO.

Constraints on Exotic Spin-Dependent Interactions Between Matter and Antimatter from Antiprotonic Helium Spectroscopy

NASA Astrophysics Data System (ADS)

Ficek, Filip; Fadeev, Pavel; Flambaum, Victor V.; Jackson Kimball, Derek F.; Kozlov, Mikhail G.; Stadnik, Yevgeny V.; Budker, Dmitry

2018-05-01

Heretofore undiscovered spin-0 or spin-1 bosons can mediate exotic spin-dependent interactions between standard model particles. Here, we carry out the first search for semileptonic spin-dependent interactions between matter and antimatter. We compare theoretical calculations and spectroscopic measurements of the hyperfine structure of antiprotonic helium to constrain exotic spin- and velocity-dependent interactions between electrons and antiprotons.

Constraints on Exotic Spin-Dependent Interactions Between Matter and Antimatter from Antiprotonic Helium Spectroscopy.

PubMed

Ficek, Filip; Fadeev, Pavel; Flambaum, Victor V; Jackson Kimball, Derek F; Kozlov, Mikhail G; Stadnik, Yevgeny V; Budker, Dmitry

2018-05-04

Heretofore undiscovered spin-0 or spin-1 bosons can mediate exotic spin-dependent interactions between standard model particles. Here, we carry out the first search for semileptonic spin-dependent interactions between matter and antimatter. We compare theoretical calculations and spectroscopic measurements of the hyperfine structure of antiprotonic helium to constrain exotic spin- and velocity-dependent interactions between electrons and antiprotons.

Noncontact bimolecular photoionization followed by radical-ions separation and their geminate recombination assisted by coherent HFI induced spin-conversion.

PubMed

Dodin, Dmitry V; Ivanov, Anatoly I; Burshtein, Anatoly I

2008-02-07

The Hamiltonian description of the spin-conversion induced by a hyperfine interaction (HFI) in photogenerated radical-ion pairs is substituted for the rate (incoherent) description of the same conversion provided by the widely used earlier elementary spin model. The quantum yields of the free ions as well as the singlet and triplet products of geminate recombination are calculated using distant dependent ionization and recombination rates, instead of their contact analogs. Invoking the simplest models of these rates, we demonstrate with the example of a spin-less system that the diffusional acceleration of radical-ion pair recombination at lower viscosity gives way to its diffusional deceleration (Angulo effect), accomplished with a kinetic plateau inherent with the primitive exponential model. Qualitatively the same behavior is found in real systems, assuming both ionization and recombination is carried out by the Marcus electron-transfer rates. Neglecting the Coulomb interaction between solvated ions, the efficiencies of radical-ion pair recombination to the singlet and triplet products are well fitted to the available experimental data. The magnetic field dependence of these yields is specified.

Rotational spectroscopic study of carbonyl sulfide solvated with hydrogen molecules.

PubMed

Michaud, Julie M; Jäger, Wolfgang

2008-10-14

Rotational spectra of small-sized (H(2))(N)-OCS clusters with N = 2-7 were measured using a pulsed-jet Fourier transform microwave spectrometer. These include spectra of pure (para-H(2))(N)-OCS clusters, pure (ortho-H(2))(N)-OCS clusters, and mixed ortho-H(2) and para-H(2) containing clusters. The rotational lines of ortho-H(2) molecules containing clusters show proton spin-proton spin hyperfine structure, and the pattern evolves as the number of ortho-H(2) molecules in the cluster increases. Various isotopologues of the clusters were investigated, including those with O(13)CS, OC(33)S, OC(34)S, and O(13)C(34)S. Nuclear quadrupole hyperfine structures of rotational transitions were observed for (33)S (nuclear spin quantum number I = 3/2) containing isotopologues. The (33)S nuclear quadrupole coupling constants are compared to the corresponding constant of the OCS monomer and those of the He(N)-OCS clusters. The assignment of the number of solvating hydrogen molecules N is supported by the analyses of the proton spin-proton spin hyperfine structures of the mixed clusters, the dependence of line intensities on sample conditions (pressure and concentrations), and the agreement of the (para-H(2))(N)-OCS and (ortho-H(2))(N)-OCS rotational constants with those from a previous infrared study [J. Tang and A. R. W. McKellar, J. Chem. Phys. 121, 3087 (2004)].

Fine- and hyperfine-structure effects in molecular photoionization. I. General theory and direct photoionization.

PubMed

Germann, Matthias; Willitsch, Stefan

2016-07-28

We develop a model for predicting fine- and hyperfine intensities in the direct photoionization of molecules based on the separability of electron and nuclear spin states from vibrational-electronic states. Using spherical tensor algebra, we derive highly symmetrized forms of the squared photoionization dipole matrix elements from which we derive the salient selection and propensity rules for fine- and hyperfine resolved photoionizing transitions. Our theoretical results are validated by the analysis of the fine-structure resolved photoelectron spectrum of O2 reported by Palm and Merkt [Phys. Rev. Lett. 81, 1385 (1998)] and are used for predicting hyperfine populations of molecular ions produced by photoionization.

The pure rotational spectrum of TiF (X 4Φr): 3d transition metal fluorides revisited

NASA Astrophysics Data System (ADS)

Sheridan, P. M.; McLamarrah, S. K.; Ziurys, L. M.

2003-11-01

The pure rotational spectrum of TiF in its X 4Φr (v=0) ground state has been measured using millimeter/sub-millimeter wave direct absorption techniques in the range 140-530 GHz. In ten out of the twelve rotational transitions recorded, all four spin-orbit components were observed, confirming the 4Φr ground state assignment. Additional small splittings were resolved in several of the spin components in lower J transitions, which appear to arise from magnetic hyperfine interactions of the 19F nucleus. In contrast, no evidence for Λ-doubling was seen in the data. The rotational transitions of TiF were analyzed using a case (a) Hamiltonian, resulting in the determination of rotational and fine structure constants, as well as hyperfine parameters for the fluorine nucleus. The data were readily fit in a case (a) basis, indicating strong first order spin-orbit coupling and minimal second-order effects, as also evidenced by the small value of λ, the spin-spin parameter. Moreover, only one higher order term, η, the spin-orbit/spin-spin interaction term, was needed in the analysis, again suggesting limited perturbations in the ground state. The relative values of the a, b, and c hyperfine constants indicate that the three unpaired electrons in this radical lie in orbitals primarily located on the titanium atom and support the molecular orbital picture of TiF with a σ1δ1π1 single electron configuration. The bond length of TiF (1.8342 Å) is significantly longer than that of TiO, suggesting that there are differences in the bonding between 3d transition metal fluorides and oxides.

Calculated hyperfine coupling constants for 5,5-dimethyl-1-pyrroline N-oxide radical products in water and benzene

NASA Astrophysics Data System (ADS)

Nardali, Ş.; Ucun, F.; Karakaya, M.

2017-11-01

The optimized structures of some radical adducts of 5,5-dimethyl-1-pyrroline N-oxide were computed by different methods on ESR spectra. As trapped radicals, H, N3, NH2, CH3, CCl3, OOH in water and F, OH, CF3, CH2OH, OC2H5 in benzene solutions were used. The calculated isotropic hyperfine coupling constants of all the trapped radicals were compared with the corresponding experimental data. The hyperfine coupling constant due to the β proton of the nitroxide radical was seen to be consist with the McConnel's relation αβ = B 0 + B 1cos2θ and, to be effected with the opposite spin density of oxygen nucleus bonded to the nitrogen. It was concluded that in hyperfine calculations the DFT(B3PW91)/LanL2DZ level is superior computational quantum model relative to the used other level. Also, the study has been enriched by the computational of the optimized geometrical parameters, the hyper conjugative interaction energies, the atomic charges and spin densities for all the radical adducts.

Spin-orbit-coupled Fermi gases of two-electron ytterbium atoms

NASA Astrophysics Data System (ADS)

He, Chengdong; Song, Bo; Haciyev, Elnur; Ren, Zejian; Seo, Bojeong; Zhang, Shanchao; Liu, Xiong-Jun; Jo, Gyu-Boong

2017-04-01

Spin-orbit coupling (SOC) has been realized in bosonic and fermionic atomic gases opening an avenue to novel physics associated with spin-momentum locking. In this talk, we will demonstrate all-optical method coupling two hyperfine ground states of 173Yb fermions through a narrow optical transition 1S0 -> 3P1. An optical AC Stark shift is applied to split the ground hyperfine levels and separate out an effective spin-1/2 subspace from other spin states for the realization of SOC. The spin dephasing dynamics and the asymmetric momentum distribution of the spin-orbit coupled Fermi gas are observed as a hallmark of SOC. The implementation of all-optical SOC for ytterbium fermions should offer a new route to a long-lived spin-orbit coupled Fermi gas and greatly expand our capability in studying novel spin-orbit physics with alkaline-earth-like atoms. Other ongoing experimental works related to SOC will be also discussed. Funded by Croucher Foundation and Research Grants Council (RGC) of Hong Kong (Project ECS26300014, GRF16300215, GRF16311516, and Croucher Innovation Grants); MOST (Grant No. 2016YFA0301604) and NSFC (No. 11574008).

Spin noise spectroscopy of ZnO

NASA Astrophysics Data System (ADS)

Horn, H.; Berski, F.; Balocchi, A.; Marie, X.; Mansur-Al-Suleiman, M.; Bakin, A.; Waag, A.; Hübner, J.; Oestreich, M.

2013-12-01

We investigate the thermal equilibrium dynamics of electron spins bound to donors in nanoporous ZnO by optical spin noise spectroscopy. The spin noise spectra reveal two noise contributions: A weak spin noise signal from undisturbed localized donor electrons with a dephasing time of 24 ns due to hyperfine interaction and a strong spin noise signal with a spin dephasing time of 5 ns which we attribute to localized donor electrons which interact with lattice defects.

Cesium alignment produced by pumping with unpolarized light★

NASA Astrophysics Data System (ADS)

Shi, Yongqi; Weis, Antoine

2018-04-01

We demonstrate optical pumping on the four hyperfine components of the Cs D 1 transition by unpolarized (UPL) resonant laser light. The evidence is based on the reduction of the absorption coefficients κ 0 with increasing light power P in an uncoated Cs vapor cell with isotropic spin relaxation. For comparison we perform the same quantitative κ 0( P) measurements with linearly-polarized light (LPL) and circularly-polarized light (CPL). We find that our previously published algebraic expressions give an excellent description of all experimentally recorded induced transparency signals. Based on this we can make reliable absolute predictions for the power dependence of the spin orientation and alignment produced by pumping with LPL, CPL and UPL.

Radiative improvement of the lattice nonrelativistic QCD action using the background field method and application to the hyperfine splitting of quarkonium states.

PubMed

Hammant, T C; Hart, A G; von Hippel, G M; Horgan, R R; Monahan, C J

2011-09-09

We present the first application of the background field method to nonrelativistic QCD (NRQCD) on the lattice in order to determine the one-loop radiative corrections to the coefficients of the NRQCD action in a manifestly gauge-covariant manner. The coefficients of the σ·B term in the NRQCD action and the four-fermion spin-spin interaction are computed at the one-loop level; the resulting shift of the hyperfine splitting of bottomonium is found to bring the lattice predictions in line with experiment.

Characterization of MgO Based Tunnel Barriers in Graphene Based Spin Valve Devices

NASA Astrophysics Data System (ADS)

Avsar, Ahmet; Balakrishnan, Jayakumar; Koon, Gavin; Ho, Yuda; Patra, Ajit; Bae, Sukang; Hong, Byung-Hee; Özyilmaz, Barbaros

2012-02-01

The low spin orbit coupling and hyperfine interaction in graphene allows a high spin relaxation length even at room temperature [1]. The demonstration of comparable spin transport properties in CVD synthesized single layer and bilayer graphene with its exfoliated counterparts raised hopes for the realization of possible room temperature spintronic applications [2]. To improve the spin transport properties of CVD Graphene based spin valves further, contact induced spin relaxation should be reduced by creating pin-hole free tunneling barriers. In this presentation, we will compare MgO barriers deposited under different conditions towards establishing pin-hole free barriers. We will discuss the effect of the substrate smoothness on the formation of high quality tunnel barriers by studying growth on different substrates. [4pt] [1] N. Tombros, C. Jozsa, M. Popinciuc, H. T. Jonkman, and B. J. van Wees, Nature 448, 571-574 (2007) [0pt] [2] A. Avsar, T. Yang, S. Bae, J. Balakrishnan, F. Volmer, M. Jaiswal, Z. Yi, S. R. Ali, G. Guntherodt, B. H. Hong, B. Beschoten, B. Ozyilmaz, Nano Lett. 10.10.1021/nl200714q (2011)

Strain-Induced Spin-Resonance Shifts in Silicon Devices

NASA Astrophysics Data System (ADS)

Pla, J. J.; Bienfait, A.; Pica, G.; Mansir, J.; Mohiyaddin, F. A.; Zeng, Z.; Niquet, Y. M.; Morello, A.; Schenkel, T.; Morton, J. J. L.; Bertet, P.

2018-04-01

In spin-based quantum-information-processing devices, the presence of control and detection circuitry can change the local environment of a spin by introducing strain and electric fields, altering its resonant frequencies. These resonance shifts can be large compared to intrinsic spin linewidths, and it is therefore important to study, understand, and model such effects in order to better predict device performance. We investigate a sample of bismuth donor spins implanted in a silicon chip, on top of which a superconducting aluminum microresonator is fabricated. The on-chip resonator provides two functions: it produces local strain in the silicon due to the larger thermal contraction of the aluminum, and it enables sensitive electron spin-resonance spectroscopy of donors close to the surface that experience this strain. Through finite-element strain simulations, we are able to reconstruct key features of our experiments, including the electron spin-resonance spectra. Our results are consistent with a recently observed mechanism for producing shifts of the hyperfine interaction for donors in silicon, which is linear with the hydrostatic component of an applied strain.

Collisional relaxation of MnH (X7Σ+) in a magnetic field: effect of the nuclear spin of Mn.

PubMed

Stoecklin, T; Halvick, Ph

2011-11-14

In the present study we investigate the role played by the hyperfine structure of manganese in the cooling and magnetic trapping of MnH((7)Σ(+)). The effect of the hyperfine structure of Mn on the relaxation of the magnetically trappable maximally stretched low-field seeking state of MnH((7)Σ(+)) in collisions with (3)He is deduced from comparison between the results of the present approach and our previous nuclear spin free calculations. We show that our previous results are unchanged at the temperature of the buffer gas cooling experiment but find a new resonance at very low collision energy. The role played by the different contributions to the hyperfine diatomic Hamiltonian considered in this work as well as the effect of an applied magnetic field on this resonance are also analyzed.

Coherent manipulation of mononuclear lanthanide-based single-molecule magnets

NASA Astrophysics Data System (ADS)

Datta, Saiti; Ghosh, Sanhita; Krzystek, Jurek; Hill, Stephen; Del Barco, Enrique; Cardona-Serra, Salvador; Coronado, Eugenio

2010-03-01

Using electron spin echo (ESE) spectroscopy, we report measurements of the longitudinal (T1) and transverse (T2) relaxation times of diluted single-crystals containing recently discovered mononuclear lanthanide-based single-molecule magnets (SMMs) encapsulated in polyoxometallate cages [AlDamen et al. J. Am. Chem. Soc. 130, 8874 -- 8875 (2008)]. This encapsulation offers the potential for preserving bulk SMM properties outside of a crystal, e.g. in molecular spintronic devices. The magnetic anisotropy in these complexes arises from the spin-orbit splitting of the ground state J multiplet of the lanthanide ion in the presence of a ligand field. At low frequencies only hyperfine-split transitions within the lowest ground state ±mJ doublet are observed. Spin relaxation times were measured for a holmium complex, and the results were compared for different hyperfine transitions and crystal dilutions. Clear Rabi oscillations were also observed, indicating that one can manipulate the spin coherently in these complexes.

Fine- and hyperfine-structure effects in molecular photoionization. I. General theory and direct photoionization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Germann, Matthias; Willitsch, Stefan, E-mail: stefan.willitsch@unibas.ch

2016-07-28

We develop a model for predicting fine- and hyperfine intensities in the direct photoionization of molecules based on the separability of electron and nuclear spin states from vibrational-electronic states. Using spherical tensor algebra, we derive highly symmetrized forms of the squared photoionization dipole matrix elements from which we derive the salient selection and propensity rules for fine- and hyperfine resolved photoionizing transitions. Our theoretical results are validated by the analysis of the fine-structure resolved photoelectron spectrum of O{sub 2} reported by Palm and Merkt [Phys. Rev. Lett. 81, 1385 (1998)] and are used for predicting hyperfine populations of molecular ionsmore » produced by photoionization.« less

Rolf Landauer and Charles H. Bennett Award Talk: Experimental development of spin qubits in silicon

NASA Astrophysics Data System (ADS)

Morello, Andrea

The modern information era is built on silicon nanoelectronic devices. The future quantum information era might be built on silicon too, if we succeed in controlling the interactions between individual spins hosted in silicon nanostructures. Spins in silicon constitute excellent solid-state qubits, because of the weak spin-orbit coupling and the possibility to remove nuclear spins from the environment through 28Si isotopic enrichment. Substitutional 31P atoms in silicon behave approximately like hydrogen in vacuum, providing two spin 1/2 qubits - the donor-bound electron and the 31P nucleus - that can be coherently controlled, read out in single-shot, and are naturally coupled through the hyperfine interaction. In isotopically-enriched 28Si, these single-atom qubits have demonstrated outstanding coherence times, up to 35 seconds for the nuclear spin, and 1-qubit gate fidelities well above 99.9% for both the electron and the nucleus. The hyperfine coupling provides a built-in interaction to entangle the two qubits within one atom. The combined initialization, control and readout fidelities result in a violation of Bell's inequality with S = 2 . 70 , a record value for solid-state qubits. Despite being identical atomic systems, 31P atoms can be addressed individually by locally modifying the hyperfine interaction through electrostatic gating. Multi-qubit logic gates can be mediated either by the exchange interaction or by electric dipole coupling. Scaling up beyond a single atom presents formidable challenges, but provides a pathway to building quantum processors that are compatible with standard semiconductor fabrication, and retain a nanometric footprint, important for truly large-scale quantum computers. Work supported by US Army Research Office (W911NF-13-1-0024) and Australian Research Council (CE110001027).

High-field Overhauser dynamic nuclear polarization in silicon below the metal-insulator transition.

PubMed

Dementyev, Anatoly E; Cory, David G; Ramanathan, Chandrasekhar

2011-04-21

Single crystal silicon is an excellent system to explore dynamic nuclear polarization (DNP), as it exhibits a continuum of properties from metallic to insulating as a function of doping concentration and temperature. At low doping concentrations DNP has been observed to occur via the solid effect, while at very high-doping concentrations an Overhauser mechanism is responsible. Here we report the hyperpolarization of (29)Si in n-doped silicon crystals, with doping concentrations in the range of (1-3) × 10(17) cm(-3). In this regime exchange interactions between donors become extremely important. The sign of the enhancement in our experiments and its frequency dependence suggest that the (29)Si spins are directly polarized by donor electrons via an Overhauser mechanism within exchange-coupled donor clusters. The exchange interaction between donors only needs to be larger than the silicon hyperfine interaction (typically much smaller than the donor hyperfine coupling) to enable this Overhauser mechanism. Nuclear polarization enhancement is observed for a range of donor clusters in which the exchange energy is comparable to the donor hyperfine interaction. The DNP dynamics are characterized by a single exponential time constant that depends on the microwave power, indicating that the Overhauser mechanism is a rate-limiting step. Since only about 2% of the silicon nuclei are located within 1 Bohr radius of the donor electron, nuclear spin diffusion is important in transferring the polarization to all the spins. However, the spin-diffusion time is much shorter than the Overhauser time due to the relatively weak silicon hyperfine coupling strength. In a 2.35 T magnetic field at 1.1 K, we observed a DNP enhancement of 244 ± 84 resulting in a silicon polarization of 10.4 ± 3.4% following 2 h of microwave irradiation.

133Cs-NMR Study on the Ground State of the Equilateral Triangular Spin Tube CsCrF4

NASA Astrophysics Data System (ADS)

Matsui, K.; Goto, T.; Manaka, H.; Miura, Y.

2018-03-01

We have investigated the hyperfine coupling between Cs and Cr on the S = 3/2 equilateral triangular spin tube CsCrF4, utilizing 133Cs-NMR. At paramagnetic state above 80 K, we have obtained spectra containing a single peak, which reflects the single crystallographic Cs site. From the temperature dependence of the peak shift and peak width, we evaluated effective values of the isotropic and the anisotropic part of hyperfine coupling. The latter was compared with the calculated dipole contribution. Using obtained parameters with assumed spin structure, we tried to reproduce the broadened spectrum in the ordered state at 2.0 K. The preliminary analysis shows the 120-degree structure does not accord with the observed spectra at the ordered state.

Electron spin resonance identification di-carbon-related centers in irradiated silicon

NASA Astrophysics Data System (ADS)

Hayashi, S.; Saito, H.; Itoh, K. M.; Vlasenko, M. P.; Vlasenko, L. S.

2018-04-01

A previously unreported electron spin resonance (ESR) spectrum was found in γ-ray irradiated silicon by the detection of the change in microwave photoconductivity arising from spin-dependent recombination (SDR). In the specially prepared silicon crystals doped by 13C isotope, a well resolved hyperfine structure of SDR-ESR lines due to the interaction between electrons and two equivalent carbon atoms having nuclear spin I = 1/2 was observed. The Si-KU4 spectrum is described by spin Hamiltonian for spin S = 1 and of g and D tensors of orthorhombic symmetry with principal values g1 = 2.008, g2 = 2.002, and g3 =2.007; and D1 = ± 103 MHz, D2 = ∓170 MHz, and D3 = ± 67 MHz where axes 1, 2, and 3 are parallel to the [1 1 ¯ 0 ], [110], and [001] crystal axes, respectively. The hyperfine splitting arising from 13C nuclei is about 0.35 mT. A possible microstructure of the detect leading to the Si-KU4 spectrum is discussed.

ESR lineshape and {sup 1}H spin-lattice relaxation dispersion in propylene glycol solutions of nitroxide radicals – Joint analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kruk, D., E-mail: danuta.kruk@matman.uwm.edu.pl; Hoffmann, S. K.; Goslar, J.

2013-12-28

Electron Spin Resonance (ESR) spectroscopy and Nuclear Magnetic Relaxation Dispersion (NMRD) experiments are reported for propylene glycol solutions of the nitroxide radical: 4-oxo-TEMPO-d{sub 16} containing {sup 15}N and {sup 14}N isotopes. The NMRD experiments refer to {sup 1}H spin-lattice relaxation measurements in a broad frequency range (10 kHz–20 MHz). A joint analysis of the ESR and NMRD data is performed. The ESR lineshapes give access to the nitrogen hyperfine tensor components and the rotational correlation time of the paramagnetic molecule. The NMRD data are interpreted in terms of the theory of paramagnetic relaxation enhancement in solutions of nitroxide radicals, recentlymore » presented by Kruk et al. [J. Chem. Phys. 138, 124506 (2013)]. The theory includes the effect of the electron spin relaxation on the {sup 1}H relaxation of the solvent. The {sup 1}H relaxation is caused by dipole-dipole interactions between the electron spin of the radical and the proton spins of the solvent molecules. These interactions are modulated by three dynamic processes: relative translational dynamics of the involved molecules, molecular rotation, and electron spin relaxation. The sensitivity to rotation originates from the non-central positions of the interacting spin in the molecules. The electronic relaxation is assumed to stem from the electron spin–nitrogen spin hyperfine coupling, modulated by rotation of the radical molecule. For the interpretation of the NMRD data, we use the nitrogen hyperfine coupling tensor obtained from ESR and fit the other relevant parameters. The consistency of the unified analysis of ESR and NMRD, evaluated by the agreement between the rotational correlation times obtained from ESR and NMRD, respectively, and the agreement of the translation diffusion coefficients with literature values obtained for pure propylene glycol, is demonstrated to be satisfactory.« less

Reanalysis and extension of the MnH A7Π- X7Σ + (0, 0) band: Fine structure and hyperfine-induced rotational branches

NASA Astrophysics Data System (ADS)

Varberg, Thomas D.; Gray, Jeffrey A.; Field, Robert W.; Merer, Anthony J.

1992-12-01

The A7Π- X7Σ + (0, 0) band of MnH at 568 nm has been recorded by laser fluorescence excitation spectroscopy. The original rotational analysis of Nevin [ Proc. R. Irish Acad.48A, 1-45 (1942); 50A, 123-137 (1945)] has been extended with some corrections at low J. Systematic internal hyperfine perturbations in the X7Σ + state, caused by the Δ N = 0, Δ J = ±1 matrix elements of the 55Mn hyperfine term in the Hamiltonian, have been observed in all seven electron spin components over the entire range of N″ studied. These perturbations destroy the "goodness" of J″ as a quantum number, giving rise to hyperfine-induced Δ J = ±2 rotational branches and to observable energy shifts of the most severely affected levels. The A7Π state, with A = 40.5 cm -1 and B = 6.35 cm -1, evolves rapidly from Hund's case ( a) to case ( b) coupling, which produces anomalous branch patterns at low J. A total of 156 rotational branches have been identified and fitted by least squares to an effective Hamiltonian, providing precise values for the rotational and fine structure constants. Values of the principal constants determined in the fit are (1σ errors in units of the last digit are listed in parentheses): The fine structures of the A7Π and X7Σ + states confirm the assignment of the A ← X transition as Mn 4 pπ ← 4 sσ in the presence of a spectator, nonbonding Mn 3 d5 ( 6S) open core.

Ultrafast Study of Dynamic Exchange Coupling in Ferromagnet/Oxide/Semiconductor Heterostructures

NASA Astrophysics Data System (ADS)

Ou, Yu-Sheng

Spintronics is the area of research that aims at utilizing the quantum mechanical spin degree of freedom of electrons in solid-state materials for information processing and data storage application. Since the discovery of the giant magnetoresistance, the field of spintronics has attracted lots of attention for its numerous potential advantages over contemporary electronics, such as less power consumption, high integration density and non-volatility. The realization of a spin battery, defined by the ability to create spin current without associated charge current, has been a long-standing goal in the field of spintronics. The demonstration of pure spin current in ferromagnet/nonmagnetic material hybrid structures by ferromagnetic resonance spin pumping has defined a thrilling direction for this field. As such, this dissertation targets at exploring the spin and magnetization dynamics in ferromagnet/oxide/semiconductor heterostructures (Fe/MgO/GaAs) using time-resolved optical pump-probe spectroscopy with the long-range goal of understanding the fundamentals of FMR-driven spin pumping. Fe/GaAs heterostructures are complex systems that contain multiple spin species, including paramagnetic spins (GaAs electrons), nuclear spins (Ga and As nuclei) and ferromagnetic spins (Fe). Optical pump-probe studies on their interplay have revealed a number of novel phenomena that has not been explored before. As such they will be the major focus of this dissertation. First, I will discuss the effect of interfacial exchange coupling on the GaAs free-carrier spin relaxation. Temperature- and field-dependent spin-resolved pump-probe studies reveal a strong correlation of the electron spin relaxation with carrier freeze-out, in quantitative agreement with a theoretical interpretation that at low temperatures the free-carrier spin lifetime is dominated by inhomogeneity in the local hyperfine field due to carrier localization. Second, we investigate the impact of tunnel barrier thickness on GaAs electron spin dynamics in Fe/MgO/GaAs heterostructures. Comparison of the Larmor frequency between samples with thick and thin MgO barriers reveals a four-fold variation in exchange coupling strength, and investigation of the spin lifetimes argues that inhomogeneity in the local hyperfine field dominates free-carrier spin relaxation across the entire range of barrier thickness. These results provide additional evidence to support the theory of hyperfine-dominated spin relaxation in GaAs. Third, we investigated the origin and dynamics of an emergent spin population by pump power and magnetic field dependent spin-resolved pump-probe studies. Power dependent study confirms its origin to be filling of electronic states in GaAs, and further field dependent studies reveal the impact of contact hyperfine coupling on the dynamics of electron spins occupying distinct electronic states. Beyond above works, we also pursue optical detection of dynamic spin pumping in Fe/MgO/GaAs heterostructures in parallel. I will discuss the development and progress that we have made toward this goal. This project can be simply divided into two phases. In the first phase, we focused on microwave excitation and optical detection of spin pumping. In the second phase, we focused on all-optical excitation and detection of spin pumping. A number of measurement strategies have been developed and executed in both stages to hunt for a spin pumping signal. I will discuss the preliminary data based upon them.

Coherent manipulation of an NV center and one carbon nuclear spin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scharfenberger, Burkhard; Nemoto, Kae; Munro, William J.

2014-12-04

We study a three-qubit system formed by the NV center’s electronic and nuclear spin plus an adjacent spin 1/2 carbon {sup 13}C. Specifically, we propose a manipulation scheme utilizing the hyperfine coupling of the effective S=1 degree of freedom of the vacancy electrons to the two adjacent nuclear spins to achieve accurate coherent control of all three qubits.

Electron spin resonance of an irradiated single crystal of potassium hydrogen maleate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iwasaki, Machio; Itoh, Koichi

1963-09-15

Electron spin resonance absorptions of x-irradiated single crystals of potassium hydrogen maleate and potassium deuterium maleate were observed. Both compounds gave the same hyperfine structures, although the slightly sharper line widths were observed for the deuterium exchanged compound.

Dynamic nuclear polarization assisted spin diffusion for the solid effect case.

PubMed

Hovav, Yonatan; Feintuch, Akiva; Vega, Shimon

2011-02-21

The dynamic nuclear polarization (DNP) process in solids depends on the magnitudes of hyperfine interactions between unpaired electrons and their neighboring (core) nuclei, and on the dipole-dipole interactions between all nuclei in the sample. The polarization enhancement of the bulk nuclei has been typically described in terms of a hyperfine-assisted polarization of a core nucleus by microwave irradiation followed by a dipolar-assisted spin diffusion process in the core-bulk nuclear system. This work presents a theoretical approach for the study of this combined process using a density matrix formalism. In particular, solid effect DNP on a single electron coupled to a nuclear spin system is considered, taking into account the interactions between the spins as well as the main relaxation mechanisms introduced via the electron, nuclear, and cross-relaxation rates. The basic principles of the DNP-assisted spin diffusion mechanism, polarizing the bulk nuclei, are presented, and it is shown that the polarization of the core nuclei and the spin diffusion process should not be treated separately. To emphasize this observation the coherent mechanism driving the pure spin diffusion process is also discussed. In order to demonstrate the effects of the interactions and relaxation mechanisms on the enhancement of the nuclear polarization, model systems of up to ten spins are considered and polarization buildup curves are simulated. A linear chain of spins consisting of a single electron coupled to a core nucleus, which in turn is dipolar coupled to a chain of bulk nuclei, is considered. The interaction and relaxation parameters of this model system were chosen in a way to enable a critical analysis of the polarization enhancement of all nuclei, and are not far from the values of (13)C nuclei in frozen (glassy) organic solutions containing radicals, typically used in DNP at high fields. Results from the simulations are shown, demonstrating the complex dependences of the DNP-assisted spin diffusion process on variations of the relevant parameters. In particular, the effect of the spin lattice relaxation times on the polarization buildup times and the resulting end polarization are discussed, and the quenching of the polarizations by the hyperfine interaction is demonstrated.

VizieR Online Data Catalog: Rotational frequencies of TiO isotopologues (Lincowski+, 2016)

NASA Astrophysics Data System (ADS)

Lincowski, A. P.; Halfen, D. T.; Ziurys, L. M.

2017-03-01

Pure rotational spectra of the rare isotopologues of titanium oxide, 46TiO, 47TiO, 49TiO, and 50TiO, have been recorded using a combination of Fourier transform millimeter-wave (FTmmW) and millimeter/submillimeter direct absorption techniques in the frequency range 62-538GHz. This study is the first complete spectroscopic characterization of these species in their X3Δr ground electronic states. The isotopologues were created by the reaction of N2O or O2 and titanium vapor, produced either by laser ablation or in a Broida-type oven, and observed in the natural Ti isotopic abundances. Between 10 and 11 rotational transitions J+1<->J were measured for each species, typically in all 3 spin-orbit ladders Ω=1, 2, and 3. For 47TiO and 49TiO, hyperfine structure was resolved, originating from the titanium-47 and titanium-49 nuclear spins of I=5/2 and 7/2, respectively. For the Ω=1 and 3 components, the hyperfine structure was found to follow a classic Lande pattern, while that for Ω=2 appeared to be perturbed, likely a result of mixing with the nearby isoconfigurational a1Δ state. The spectra were analyzed with a case (a) Hamiltonian, and rotational, spin-orbit, and spin-spin parameters were determined for each species, as well as magnetic hyperfine and electric quadrupole constants for the two molecules with nuclear spins. The most abundant species, 48TiO, has been detected in circumstellar envelopes. These measurements will enable other titanium isotopologues to be studied at millimeter wavelengths, providing Ti isotope ratios that can test models of nucleosynthesis. (1 data file).

Millimeter/Submillimeter Spectroscopy of TiO (X3Δr): The Rare Titanium Isotopologues

NASA Astrophysics Data System (ADS)

Lincowski, A. P.; Halfen, D. T.; Ziurys, L. M.

2016-12-01

Pure rotational spectra of the rare isotopologues of titanium oxide, 46TiO, 47TiO, 49TiO, and 50TiO, have been recorded using a combination of Fourier transform millimeter-wave (FTmmW) and millimeter/submillimeter direct absorption techniques in the frequency range 62-538 GHz. This study is the first complete spectroscopic characterization of these species in their X 3Δ r ground electronic states. The isotopologues were created by the reaction of N2O or O2 and titanium vapor, produced either by laser ablation or in a Broida-type oven, and observed in the natural Ti isotopic abundances. Between 10 and 11 rotational transitions J + 1 ≤ftrightarrow J were measured for each species, typically in all 3 spin-orbit ladders Ω = 1, 2, and 3. For 47TiO and 49TiO, hyperfine structure was resolved, originating from the titanium-47 and titanium-49 nuclear spins of I = 5/2 and 7/2, respectively. For the Ω = 1 and 3 components, the hyperfine structure was found to follow a classic Landé pattern, while that for Ω = 2 appeared to be perturbed, likely a result of mixing with the nearby isoconfigurational a 1Δ state. The spectra were analyzed with a case (a) Hamiltonian, and rotational, spin-orbit, and spin-spin parameters were determined for each species, as well as magnetic hyperfine and electric quadrupole constants for the two molecules with nuclear spins. The most abundant species, 48TiO, has been detected in circumstellar envelopes. These measurements will enable other titanium isotopologues to be studied at millimeter wavelengths, providing Ti isotope ratios that can test models of nucleosynthesis.

The hyperfine excitation of OH radicals by He

NASA Astrophysics Data System (ADS)

Marinakis, Sarantos; Kalugina, Yulia; Lique, François

2016-04-01

Hyperfine-resolved collisions between OH radicals and He atoms are investigated using quantum scattering calculations and the most recent ab initio potential energy surface, which explicitly takes into account the OH vibrational motion. Such collisions play an important role in astrophysics, in particular in the modelling of OH masers. The hyperfine-resolved collision cross sections are calculated for collision energies up to 2500 cm-1 from the nuclear spin free scattering S-matrices using a recoupling technique. The collisional hyperfine propensities observed are discussed. As expected, the results from our work suggest that there is a propensity for collisions with ΔF = Δj. The new OH-He hyperfine cross sections are expected to significantly help in the modelling of OH masers from current and future astronomical observations. Contribution to the Topical Issue "Atomic Cluster Collisions (7th International Symposium)", edited by Gerardo Delgado Barrio, Andrey Solov'Yov, Pablo Villarreal, Rita Prosmiti.

Hyperfine Induced Transitions as Diagnostics of Isotopic Composition and Densities of Low-Density Plasmas

NASA Astrophysics Data System (ADS)

Brage, Tomas; Judge, Philip G.; Aboussaïd, Abdellatif; Godefroid, Michel R.; Jönsson, Per; Ynnerman, Anders; Froese Fischer, Charlotte; Leckrone, David S.

1998-06-01

The J = 0 --> J' = 0 radiative transitions, usually viewed as allowed through two-photon decay, may also be induced by the hyperfine (HPF) interaction in atoms or ions having a nonzero nuclear spin. We compute new and review existing decay rates for the nsnp 3PoJ --> ns2 1SJ'=0 transitions in ions of the Be (n = 2) and Mg (n = 3) isoelectronic sequences. The HPF induced decay rates for the J = 0 --> J' = 0 transitions are many orders of magnitude larger than those for the competing two-photon processes, and when present are typically 1 or 2 orders of magnitude smaller than the decay rates of the magnetic quadrupole (J = 2 --> J' = 0) transitions for these ions. Several HPF induced transitions are potentially of astrophysical interest in ions of C, N, Na, Mg, Al, Si, K, Cr, Fe, and Ni. We highlight those cases that may be of particular diagnostic value for determining isotopic abundance ratios and/or electron densities from UV or EUV emission-line data. We present our atomic data in the form of scaling laws so that, given the isotopic nuclear spin and magnetic moment, a simple expression yields estimates for HPF induced decay rates. We examine some UV and EUV solar and nebular data in light of these new results and suggest possible applications for future study. We could not find evidence for the existence of HPF induced lines in the spectra we examined, but we demonstrate that existing data have come close to providing interesting upper limits. For the planetary nebula SMC N2, we derive an upper limit of 0.1 for 13C/12C from Goddard High-Resolution Spectrograph data obtained by Clegg. It is likely that more stringent limits could be obtained using newer data with higher sensitivities in a variety of objects.

Internal Spin Control, Squeezing and Decoherence in Ensembles of Alkali Atomic Spins

NASA Astrophysics Data System (ADS)

Norris, Leigh Morgan

Large atomic ensembles interacting with light are one of the most promising platforms for quantum information processing. In the past decade, novel applications for these systems have emerged in quantum communication, quantum computing, and metrology. Essential to all of these applications is the controllability of the atomic ensemble, which is facilitated by a strong coupling between the atoms and light. Non-classical spin squeezed states are a crucial step in attaining greater ensemble control. The degree of entanglement present in these states, furthermore, serves as a benchmark for the strength of the atom-light interaction. Outside the broader context of quantum information processing with atomic ensembles, spin squeezed states have applications in metrology, where their quantum correlations can be harnessed to improve the precision of magnetometers and atomic clocks. This dissertation focuses upon the production of spin squeezed states in large ensembles of cold trapped alkali atoms interacting with optical fields. While most treatments of spin squeezing consider only the case in which the ensemble is composed of two level systems or qubits, we utilize the entire ground manifold of an alkali atom with hyperfine spin f greater than or equal to 1/2, a qudit. Spin squeezing requires non-classical correlations between the constituent atomic spins, which are generated through the atoms' collective coupling to the light. Either through measurement or multiple interactions with the atoms, the light mediates an entangling interaction that produces quantum correlations. Because the spin squeezing treated in this dissertation ultimately originates from the coupling between the light and atoms, conventional approaches of improving this squeezing have focused on increasing the optical density of the ensemble. The greater number of internal degrees of freedom and the controllability of the spin-f ground hyperfine manifold enable novel methods of enhancing squeezing. In particular, we find that state preparation using control of the internal hyperfine spin increases the entangling power of squeezing protocols when f>1/2. Post-processing of the ensemble using additional internal spin control converts this entanglement into metrologically useful spin squeezing. By employing a variation of the Holstein-Primakoff approximation, in which the collective spin observables of the atomic ensemble are treated as quadratures of a bosonic mode, we model entanglement generation, spin squeezing and the effects of internal spin control. The Holstein-Primakoff formalism also enables us to take into account the decoherence of the ensemble due to optical pumping. While most works ignore or treat optical pumping phenomenologically, we employ a master equation derived from first principles. Our analysis shows that state preparation and the hyperfine spin size have a substantial impact upon both the generation of spin squeezing and the decoherence of the ensemble. Through a numerical search, we determine state preparations that enhance squeezing protocols while remaining robust to optical pumping. Finally, most work on spin squeezing in atomic ensembles has treated the light as a plane wave that couples identically to all atoms. In the final part of this dissertation, we go beyond the customary plane wave approximation on the light and employ focused paraxial beams, which are more efficiently mode matched to the radiation pattern of the atomic ensemble. The mathematical formalism and the internal spin control techniques that we applied in the plane wave case are generalized to accommodate the non-homogeneous paraxial probe. We find the optimal geometries of the atomic ensemble and the probe for mode matching and generation of spin squeezing.

Internal Spin Control, Squeezing and Decoherence in Ensembles of Alkali Atomic Spins

NASA Astrophysics Data System (ADS)

Norris, Leigh Morgan

Large atomic ensembles interacting with light are one of the most promising platforms for quantum information processing. In the past decade, novel applications for these systems have emerged in quantum communication, quantum computing, and metrology. Essential to all of these applications is the controllability of the atomic ensemble, which is facilitated by a strong coupling between the atoms and light. Non-classical spin squeezed states are a crucial step in attaining greater ensemble control. The degree of entanglement present in these states, furthermore, serves as a benchmark for the strength of the atom-light interaction. Outside the broader context of quantum information processing with atomic ensembles, spin squeezed states have applications in metrology, where their quantum correlations can be harnessed to improve the precision of magnetometers and atomic clocks. This dissertation focuses upon the production of spin squeezed states in large ensembles of cold trapped alkali atoms interacting with optical fields. While most treatments of spin squeezing consider only the case in which the ensemble is composed of two level systems or qubits, we utilize the entire ground manifold of an alkali atom with hyperfine spin f greater or equal to 1/2, a qudit. Spin squeezing requires non-classical correlations between the constituent atomic spins, which are generated through the atoms' collective coupling to the light. Either through measurement or multiple interactions with the atoms, the light mediates an entangling interaction that produces quantum correlations. Because the spin squeezing treated in this dissertation ultimately originates from the coupling between the light and atoms, conventional approaches of improving this squeezing have focused on increasing the optical density of the ensemble. The greater number of internal degrees of freedom and the controllability of the spin-f ground hyperfine manifold enable novel methods of enhancing squeezing. In particular, we find that state preparation using control of the internal hyperfine spin increases the entangling power of squeezing protocols when f >1/2. Post-processing of the ensemble using additional internal spin control converts this entanglement into metrologically useful spin squeezing. By employing a variation of the Holstein-Primakoff approximation, in which the collective spin observables of the atomic ensemble are treated as quadratures of a bosonic mode, we model entanglement generation, spin squeezing and the effects of internal spin control. The Holstein-Primakoff formalism also enables us to take into account the decoherence of the ensemble due to optical pumping. While most works ignore or treat optical pumping phenomenologically, we employ a master equation derived from first principles. Our analysis shows that state preparation and the hyperfine spin size have a substantial impact upon both the generation of spin squeezing and the decoherence of the ensemble. Through a numerical search, we determine state preparations that enhance squeezing protocols while remaining robust to optical pumping. Finally, most work on spin squeezing in atomic ensembles has treated the light as a plane wave that couples identically to all atoms. In the final part of this dissertation, we go beyond the customary plane wave approximation on the light and employ focused paraxial beams, which are more efficiently mode matched to the radiation pattern of the atomic ensemble. The mathematical formalism and the internal spin control techniques that we applied in the plane wave case are generalized to accommodate the non-homogeneous paraxial probe. We find the optimal geometries of the atomic ensemble and the probe for mode matching and generation of spin squeezing.

Measurement of the spin temperature of optically cooled nuclei and GaAs hyperfine constants in GaAs/AlGaAs quantum dots

NASA Astrophysics Data System (ADS)

Chekhovich, E. A.; Ulhaq, A.; Zallo, E.; Ding, F.; Schmidt, O. G.; Skolnick, M. S.

2017-10-01

Deep cooling of electron and nuclear spins is equivalent to achieving polarization degrees close to 100% and is a key requirement in solid-state quantum information technologies. While polarization of individual nuclear spins in diamond and SiC (ref. ) reaches 99% and beyond, it has been limited to 50-65% for the nuclei in quantum dots. Theoretical models have attributed this limit to formation of coherent `dark' nuclear spin states but experimental verification is lacking, especially due to the poor accuracy of polarization degree measurements. Here we measure the nuclear polarization in GaAs/AlGaAs quantum dots with high accuracy using a new approach enabled by manipulation of the nuclear spin states with radiofrequency pulses. Polarizations up to 80% are observed--the highest reported so far for optical cooling in quantum dots. This value is still not limited by nuclear coherence effects. Instead we find that optically cooled nuclei are well described within a classical spin temperature framework. Our findings unlock a route for further progress towards quantum dot electron spin qubits where deep cooling of the mesoscopic nuclear spin ensemble is used to achieve long qubit coherence. Moreover, GaAs hyperfine material constants are measured here experimentally for the first time.

Morphology effects on spin-dependent transport and recombination in polyfluorene thin films

NASA Astrophysics Data System (ADS)

Miller, Richards; van Schooten, K. J.; Malissa, H.; Joshi, G.; Jamali, S.; Lupton, J. M.; Boehme, C.

2016-12-01

We have studied the role of spin-dependent processes on conductivity in polyfluorene (PFO) thin films by preforming continuous wave (cw) electrically detected magnetic resonance (EDMR) spectroscopy at temperatures between 10 K and room temperature using microwave frequencies between about 1 GHz and 20 GHz, as well as pulsed EDMR at the X band (10 GHz). Variable frequency EDMR allows us to establish the role of spin-orbit coupling in spin-dependent processes whereas pulsed EDMR allows for the observation of coherent spin motion effects. We used PFO for this study in order to allow for the investigation of the effects of microscopic morphological ordering since this material can adopt two distinct intrachain morphologies: an amorphous (glassy) phase, in which monomer units are twisted with respect to each other, and an ordered (β) phase, where all monomers lie within one plane. In thin films of organic light-emitting diodes, the appearance of a particular phase can be controlled by deposition parameters and solvent vapor annealing, and is verified by electroluminescence spectroscopy. Under bipolar charge-carrier injection conditions, we conducted multifrequency cw EDMR, electrically detected Rabi spin-beat experiments, and Hahn echo and inversion-recovery measurements. Coherent echo spectroscopy reveals electrically detected electron-spin-echo envelope modulation due to the coupling of the carrier spins to nearby nuclear spins. Our results demonstrate that, while conformational disorder can influence the observed EDMR signals, including the sign of the current changes on resonance as well as the magnitudes of local hyperfine fields and charge-carrier spin-orbit interactions, it does not qualitatively affect the nature of spin-dependent transitions in this material. In both morphologies, we observe the presence of at least two different spin-dependent recombination processes. At room temperature and 10 K, polaron-pair recombination through weakly spin-spin coupled intermediate charge-carrier pair states is dominant, while at low temperatures, additional signatures of spin-dependent charge transport through the interaction of polarons with triplet excitons are seen in the half-field resonance of a triplet spin-1 species. This additional contribution arises since triplet lifetimes are increased at lower temperatures. We tentatively conclude that spectral broadening induced by hyperfine coupling is slightly weaker in the more ordered β-phase than in the glassy phase since protons are more evenly spaced, whereas broadening effects due to spin-orbit coupling, which impacts the distribution of g -factors, appear to be somewhat more significant in the β-phase.

Influence of the nuclear Zeeman effect on mode locking in pulsed semiconductor quantum dots

NASA Astrophysics Data System (ADS)

Beugeling, Wouter; Uhrig, Götz S.; Anders, Frithjof B.

2017-09-01

The coherence of the electron spin in a semiconductor quantum dot is strongly enhanced by mode locking through nuclear focusing, where the synchronization of the electron spin to periodic pulsing is slowly transferred to the nuclear spins of the semiconductor material, mediated by the hyperfine interaction between these. The external magnetic field that drives the Larmor oscillations of the electron spin also subjects the nuclear spins to a Zeeman-like coupling, albeit a much weaker one. For typical magnetic fields used in experiments, the energy scale of the nuclear Zeeman effect is comparable to that of the hyperfine interaction, so that it is not negligible. In this work, we analyze the influence of the nuclear Zeeman effect on mode locking quantitatively. Within a perturbative framework, we calculate the Overhauser-field distribution after a prolonged period of pulsing. We find that the nuclear Zeeman effect can exchange resonant and nonresonant frequencies. We distinguish between models with a single type and with multiple types of nuclei. For the latter case, the positions of the resonances depend on the individual g factors, rather than on the average value.

Effects of nuclear spins on the transport properties of the edge of two-dimensional topological insulators

NASA Astrophysics Data System (ADS)

Hsu, Chen-Hsuan; Stano, Peter; Klinovaja, Jelena; Loss, Daniel

2018-03-01

The electrons in the edge channels of two-dimensional topological insulators can be described as a helical Tomonaga-Luttinger liquid. They couple to nuclear spins embedded in the host materials through the hyperfine interaction, and are therefore subject to elastic spin-flip backscattering on the nuclear spins. We investigate the nuclear-spin-induced edge resistance due to such backscattering by performing a renormalization-group analysis. Remarkably, the effect of this backscattering mechanism is stronger in a helical edge than in nonhelical channels, which are believed to be present in the trivial regime of InAs/GaSb quantum wells. In a system with sufficiently long edges, the disordered nuclear spins lead to an edge resistance which grows exponentially upon lowering the temperature. On the other hand, electrons from the edge states mediate an anisotropic Ruderman-Kittel-Kasuya-Yosida nuclear spin-spin interaction, which induces a spiral nuclear spin order below the transition temperature. We discuss the features of the spiral order, as well as its experimental signatures. In the ordered phase, we identify two backscattering mechanisms, due to charge impurities and magnons. The backscattering on charge impurities is allowed by the internally generated magnetic field, and leads to an Anderson-type localization of the edge states. The magnon-mediated backscattering results in a power-law resistance, which is suppressed at zero temperature. Overall, we find that in a sufficiently long edge the nuclear spins, whether ordered or not, suppress the edge conductance to zero as the temperature approaches zero.

Modulated magnetic structure of F e3P O7 as seen by 57Fe Mössbauer spectroscopy

NASA Astrophysics Data System (ADS)

Sobolev, A. V.; Akulenko, A. A.; Glazkova, I. S.; Pankratov, D. A.; Presniakov, I. A.

2018-03-01

The paper reports results of the 57Fe Mössbauer measurements on an F e3P O4O3 powder sample recorded at various temperatures, including the point of magnetic phase transition TN≈163 K . The spectra measured above TN consist of a quadrupole doublet with high quadrupole splitting of Δ300 K≈1.10 mm /s , emphasizing that F e3 + ions are located in crystal positions with a strong electric-field gradient (EFG). To predict the sign and orientation of the main components of the EFG tensor, we calculated the EFG using the density-functional-theory approach. In the temperature range T

Hyperfine-Structure-Induced Depolarization of Impulsively Aligned I2 Molecules

NASA Astrophysics Data System (ADS)

Thomas, Esben F.; Søndergaard, Anders A.; Shepperson, Benjamin; Henriksen, Niels E.; Stapelfeldt, Henrik

2018-04-01

A moderately intense 450 fs laser pulse is used to create rotational wave packets in gas phase I2 molecules. The ensuing time-dependent alignment, measured by Coulomb explosion imaging with a delayed probe pulse, exhibits the characteristic revival structures expected for rotational wave packets but also a complex nonperiodic substructure and decreasing mean alignment not observed before. A quantum mechanical model attributes the phenomena to coupling between the rotational angular momenta and the nuclear spins through the electric quadrupole interaction. The calculated alignment trace agrees very well with the experimental results.

Delocalization of Coherent Triplet Excitons in Linear Rigid Rod Conjugated Oligomers.

PubMed

Hintze, Christian; Korf, Patrick; Degen, Frank; Schütze, Friederike; Mecking, Stefan; Steiner, Ulrich E; Drescher, Malte

2017-02-02

In this work, the triplet state delocalization in a series of monodisperse oligo(p-phenyleneethynylene)s (OPEs) is studied by pulsed electron paramagnetic resonance (EPR) and pulsed electron nuclear double resonance (ENDOR) determining zero-field splitting, optical spin polarization, and proton hyperfine couplings. Neither the zero-field splitting parameters nor the optical spin polarization change significantly with OPE chain length, in contrast to the hyperfine coupling constants, which showed a systematic decrease with chain length n according to a 2/(1 + n) decay law. The results provide striking evidence for the Frenkel-type nature of the triplet excitons exhibiting full coherent delocalization in the OPEs under investigation with up to five OPE repeat units and with a spin density distribution described by a nodeless particle in the box wave function. The same model is successfully applied to recently published data on π-conjugated porphyrin oligomers.

Hyperfine structure measurements of neutral vanadium by laser-induced fluorescence spectroscopy in the wavelength range from 750 nm to 860 nm

NASA Astrophysics Data System (ADS)

Başar, Gü.; Güzelçimen, F.; Öztürk, I. K.; Er, A.; Bingöl, D.; Kröger, S.; Başar, Gö.

2017-11-01

The hyperfine structure of 57 spectral lines of neutral vanadium has been investigated using a hollow cathode lamp by laser-induced fluorescence spectroscopy in the wavelength range from 750 nm to 860 nm. New magnetic dipole hyperfine structure constants A have been determined for 14 atomic energy levels and new electric quadrupole hyperfine structure constants B for two levels. Additionally previously published hyperfine structure constants A of 56 levels have been measured again. In five cases, the old A values have been rejected and replaced by improved values.

NMR Shielding in Metals Using the Augmented Plane Wave Method

PubMed Central

2015-01-01

We present calculations of solid state NMR magnetic shielding in metals, which includes both the orbital and the complete spin response of the system in a consistent way. The latter contains an induced spin-polarization of the core states and needs an all-electron self-consistent treatment. In particular, for transition metals, the spin hyperfine field originates not only from the polarization of the valence s-electrons, but the induced magnetic moment of the d-electrons polarizes the core s-states in opposite direction. The method is based on DFT and the augmented plane wave approach as implemented in the WIEN2k code. A comparison between calculated and measured NMR shifts indicates that first-principle calculations can obtain converged results and are more reliable than initially concluded based on previous publications. Nevertheless large k-meshes (up to 2 000 000 k-points in the full Brillouin-zone) and some Fermi-broadening are necessary. Our results show that, in general, both spin and orbital components of the NMR shielding must be evaluated in order to reproduce experimental shifts, because the orbital part cancels the shift of the usually highly ionic reference compound only for simple sp-elements but not for transition metals. This development paves the way for routine NMR calculations of metallic systems. PMID:26322148

Density functional calculations of (55)Mn, (14)N and (13)C electron paramagnetic resonance parameters support an energetically feasible model system for the S(2) state of the oxygen-evolving complex of photosystem II.

PubMed

Schinzel, Sandra; Schraut, Johannes; Arbuznikov, Alexei V; Siegbahn, Per E M; Kaupp, Martin

2010-09-10

Metal and ligand hyperfine couplings of a previously suggested, energetically feasible Mn(4)Ca model cluster (SG2009(-1)) for the S(2) state of the oxygen-evolving complex (OEC) of photosystem II (PSII) have been studied by broken-symmetry density functional methods and compared with other suggested structural and spectroscopic models. This was carried out explicitly for different spin-coupling patterns of the S=1/2 ground state of the Mn(III)(Mn(IV))(3) cluster. By applying spin-projection techniques and a scaling of the manganese hyperfine couplings, computation of the hyperfine and nuclear quadrupole coupling parameters allows a direct evaluation of the proposed models in comparison with data obtained from the simulation of EPR, ENDOR, and ESEEM spectra. The computation of (55)Mn hyperfine couplings (HFCs) for SG2009(-1) gives excellent agreement with experiment. However, at the current level of spin projection, the (55)Mn HFCs do not appear sufficiently accurate to distinguish between different structural models. Yet, of all the models studied, SG2009(-1) is the only one with the Mn(III) site at the Mn(C) center, which is coordinated by histidine (D1-His332). The computed histidine (14)N HFC anisotropy for SG2009(-1) gives much better agreement with ESEEM data than the other models, in which Mn(C) is an Mn(IV) site, thus supporting the validity of the model. The (13)C HFCs of various carboxylates have been compared with (13)C ENDOR data for PSII preparations with (13)C-labelled alanine.

Giant titanium electron wave function in gallium oxide: A potential electron-nuclear spin system for quantum information processing

NASA Astrophysics Data System (ADS)

Mentink-Vigier, Frédéric; Binet, Laurent; Vignoles, Gerard; Gourier, Didier; Vezin, Hervé

2010-11-01

The hyperfine interactions of the unpaired electron with eight surrounding G69a and G71a nuclei in Ti-doped β-Ga2O3 were analyzed by electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopies. They are dominated by strong isotropic hyperfine couplings due to a direct Fermi contact interaction with Ga nuclei in octahedral sites of rutile-type chains oriented along b axis, revealing a large anisotropic spatial extension of the electron wave function. Titanium in β-Ga2O3 is thus best described as a diffuse (Ti4+-e-) pair rather than as a localized Ti3+ . Both electron and G69a nuclear spin Rabi oscillations could be observed by pulsed EPR and pulsed ENDOR, respectively. The electron spin decoherence time is about 1μs (at 4 K) and an upper bound of 520μs (at 8 K) is estimated for the nuclear decoherence time. Thus, β-Ga2O3:Ti appears to be a potential spin-bus system for quantum information processing with a large nuclear spin quantum register.

One-electron oxidation of individual DNA bases and DNA base stacks.

PubMed

Close, David M

2010-02-04

In calculations performed with DFT there is a tendency of the purine cation to be delocalized over several bases in the stack. Attempts have been made to see if methods other than DFT can be used to calculate localized cations in stacks of purines, and to relate the calculated hyperfine couplings with known experimental results. To calculate reliable hyperfine couplings it is necessary to have an adequate description of spin polarization which means that electron correlation must be treated properly. UMP2 theory has been shown to be unreliable in estimating spin densities due to overestimates of the doubles correction. Therefore attempts have been made to use quadratic configuration interaction (UQCISD) methods to treat electron correlation. Calculations on the individual DNA bases are presented to show that with UQCISD methods it is possible to calculate hyperfine couplings in good agreement with the experimental results. However these UQCISD calculations are far more time-consuming than DFT calculations. Calculations are then extended to two stacked guanine bases. Preliminary calculations with UMP2 or UQCISD theory on two stacked guanines lead to a cation localized on a single guanine base.

Optimised frequency modulation for continuous-wave optical magnetic resonance sensing using nitrogen-vacancy ensembles.

PubMed

El-Ella, Haitham A R; Ahmadi, Sepehr; Wojciechowski, Adam M; Huck, Alexander; Andersen, Ulrik L

2017-06-26

Magnetometers based on ensembles of nitrogen-vacancy centres are a promising platform for continuously sensing static and low-frequency magnetic fields. Their combination with phase-sensitive (lock-in) detection creates a highly versatile sensor with a sensitivity that is proportional to the derivative of the optical magnetic resonance lock-in spectrum, which is in turn dependant on the lock-in modulation parameters. Here we study the dependence of the lock-in spectral slope on the modulation of the spin-driving microwave field. Given the presence of the intrinsic nitrogen hyperfine spin transitions, we experimentally show that when the ratio between the hyperfine linewidth and their separation is ≳ 1/4, square-wave based frequency modulation generates the steepest slope at modulation depths exceeding the separation of the hyperfine lines, compared to sine-wave based modulation. We formulate a model for calculating lock-in spectra which shows excellent agreement with our experiments, and which shows that an optimum slope is achieved when the linewidth/separation ratio is ≲ 1/4 and the modulation depth is less then the resonance linewidth, irrespective of the modulation function used.

Stochastic hyperfine interactions modeling library

NASA Astrophysics Data System (ADS)

Zacate, Matthew O.; Evenson, William E.

2011-04-01

The stochastic hyperfine interactions modeling library (SHIML) provides a set of routines to assist in the development and application of stochastic models of hyperfine interactions. The library provides routines written in the C programming language that (1) read a text description of a model for fluctuating hyperfine fields, (2) set up the Blume matrix, upon which the evolution operator of the system depends, and (3) find the eigenvalues and eigenvectors of the Blume matrix so that theoretical spectra of experimental techniques that measure hyperfine interactions can be calculated. The optimized vector and matrix operations of the BLAS and LAPACK libraries are utilized; however, there was a need to develop supplementary code to find an orthonormal set of (left and right) eigenvectors of complex, non-Hermitian matrices. In addition, example code is provided to illustrate the use of SHIML to generate perturbed angular correlation spectra for the special case of polycrystalline samples when anisotropy terms of higher order than A can be neglected. Program summaryProgram title: SHIML Catalogue identifier: AEIF_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEIF_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU GPL 3 No. of lines in distributed program, including test data, etc.: 8224 No. of bytes in distributed program, including test data, etc.: 312 348 Distribution format: tar.gz Programming language: C Computer: Any Operating system: LINUX, OS X RAM: Varies Classification: 7.4 External routines: TAPP [1], BLAS [2], a C-interface to BLAS [3], and LAPACK [4] Nature of problem: In condensed matter systems, hyperfine methods such as nuclear magnetic resonance (NMR), Mössbauer effect (ME), muon spin rotation (μSR), and perturbed angular correlation spectroscopy (PAC) measure electronic and magnetic structure within Angstroms of nuclear probes through the hyperfine interaction. When interactions fluctuate at rates comparable to the time scale of a hyperfine method, there is a loss in signal coherence, and spectra are damped. The degree of damping can be used to determine fluctuation rates, provided that theoretical expressions for spectra can be derived for relevant physical models of the fluctuations. SHIML provides routines to help researchers quickly develop code to incorporate stochastic models of fluctuating hyperfine interactions in calculations of hyperfine spectra. Solution method: Calculations are based on the method for modeling stochastic hyperfine interactions for PAC by Winkler and Gerdau [5]. The method is extended to include other hyperfine methods following the work of Dattagupta [6]. The code provides routines for reading model information from text files, allowing researchers to develop new models quickly without the need to modify computer code for each new model to be considered. Restrictions: In the present version of the code, only methods that measure the hyperfine interaction on one probe spin state, such as PAC, μSR, and NMR, are supported. Running time: Varies

Spin relaxation in quantum dots due to electron exchange with leads.

PubMed

Vorontsov, A B; Vavilov, M G

2008-11-28

We calculate spin relaxation rates in lateral quantum dot systems due to electron exchange between dots and leads. Using rate equations, we develop a theoretical description of the experimentally observed electric current in the spin blockade regime of double quantum dots. A single expression fits the entire current profile and describes the structure of both the conduction peaks and the suppressed ("valley") region. Extrinsic rates calculated here have to be taken into account for accurate extraction of intrinsic relaxation rates due to the spin-orbit and hyperfine spin scattering mechanisms from spin blockade measurements.

Diamond nitrogen vacancy electronic and nuclear spin-state anti-crossings under weak transverse magnetic fields

NASA Astrophysics Data System (ADS)

Clevenson, Hannah; Chen, Edward; Dolde, Florian; Teale, Carson; Englund, Dirk; Braje, Danielle

2016-05-01

We report on detailed studies of electronic and nuclear spin states in the diamond nitrogen vacancy (NV) center under moderate transverse magnetic fields. We numerically predict and experimentally verify a previously unobserved NV ground state hyperfine anti-crossing occurring at magnetic bias fields as low as tens of Gauss - two orders of magnitude lower than previously reported hyperfine anti-crossings at ~ 510 G and ~ 1000 G axial magnetic fields. We then discuss how this regime can be optimized for magnetometry and other sensing applications and propose a method for how the nitrogen-vacancy ground state Hamiltonian can be manipulated by small transverse magnetic fields to polarize the nuclear spin state. Acknowlegement: The Lincoln Laboratory portion of this work is sponsored by the Assistant Secretary of Defense for Research & Engineering under Air Force Contract #FA8721-05-C-0002. Opinions, interpretations, conclusions and recommendations are those of the authors and are not necessarily endorsed by the United States Government.

Transport-related triplet states and hyperfine couplings in organic tandem solar cells probed by pulsed electrically detected magnetic resonance spectroscopy

NASA Astrophysics Data System (ADS)

Kraffert, Felix; Bahro, Daniel; Meier, Christoph; Denne, Maximilian; Colsmann, Alexander; Behrends, Jan

2017-09-01

Tandem solar cells constitute the most successful organic photovoltaic devices with power conversion efficiencies comparable to thin-film silicon solar cells. Especially their high open-circuit voltage - only achievable by a well-adjusted layer stacking - leads to their high efficiencies. Nevertheless, the microscopic processes causing the lossless recombination of charge carriers within the recombination zone are not well understood yet. We show that advanced pulsed electrically detected magnetic resonance techniques such as electrically detected (ED)-Rabi nutation measurements and electrically detected hyperfine sublevel correlation (ED-HYSCORE) spectroscopy help to understand the role of triplet excitons in these microscopic processes. We investigate fully working miniaturised organic tandem solar cells and detect current-influencing doublet states in different layers as well as triplet excitons located on the fullerene-based acceptor. We apply ED-HYSCORE in order to study the nuclear spin environment of the relevant electron/hole spins and detect a significant amount of the low abundant 13C nuclei coupled to the observer spins.

Anomalous electron spin decoherence in an optically pumped quantum dot

NASA Astrophysics Data System (ADS)

Shi, Xiaofeng; Sham, L. J.

2013-03-01

We study the nuclear-spin-fluctuation induced spin decoherence of an electron (SDE) in an optically pumped quantum dot. The SDE is computed in terms of the steady distribution of the nuclear field (SDNF) formed through the hyperfine interaction (HI) with two different nuclear species in the dot. A feedback loop between the optically driven electron spin and the nuclear spin ensemble determines the SDNF [W. Yang and L. J. Sham, Phy. Rev. B 85, 235319(2012)]. Different from that work and others reviewed therein, where a bilinear HI, SαIβ , between the electron (or hole) spin S and the nuclear spin I is used, we use an effective nonlinear interaction of the form SαIβIγ derived from the Fermi-contact HI. Our feedback loop forms a multi-peak SDNF in which the SDE shows remarkable collapses and revivals in nanosecond time scale. Such an anomalous SDE results from a quantum interference effect of the electron Larmor precession in a multi-peak effective magnetic field. In the presence of a bilinear HI that suppresses the nuclear spin fluctuation, the non-Markovian SDE persists whenever there are finite Fermi contact interactions between two or more kinds of nuclei and the electron in the quantum dot. This work is supported by NSF(PHY 1104446) and the US Army Research Office MURI award W911NF0910406.

Local spin structure of the α -RuCl3 honeycomb-lattice magnet observed via muon spin rotation/relaxation

NASA Astrophysics Data System (ADS)

Yamauchi, Ichihiro; Hiraishi, Masatoshi; Okabe, Hirotaka; Takeshita, Soshi; Koda, Akihiro; Kojima, Kenji M.; Kadono, Ryosuke; Tanaka, Hidekazu

2018-04-01

We report a muon spin rotation/relaxation (μ SR ) study of single-crystalline samples of the α -RuCl3 honeycomb magnet, which is presumed to be a model compound for the Kitaev-Heisenberg interaction. It is inferred from magnetic susceptibility and specific-heat measurements that the present samples exhibit successive magnetic transitions at different critical temperatures TN with decreasing temperature, eventually falling into the TN=7 K antiferromagnetic (7 K) phase that has been observed in only single-crystalline specimens with the least stacking fault. Via μ SR measurements conducted under a zero external field, we show that such behavior originates from a phase separation induced by the honeycomb plane stacking fault, yielding multiple domains with different TN's. We also perform μ SR measurements under a transverse field in the paramagnetic phase to identify the muon site from the muon-Ru hyperfine parameters. Based on a comparison of the experimental and calculated internal fields at the muon site for the two possible spin structures inferred from neutron diffraction data, we suggest a modulated zigzag spin structure for the 7 K phase, with the amplitude of the ordered magnetic moment being significantly reduced from that expected for the orbital quenched spin-1/2 state.

Magnetic interactions in equi-atomic rare-earth intermetallic alloys RScGe (R = Ce, Pr, Nd and Gd) studied by time differential perturbed angular correlation spectroscopy and ab initio calculations.

PubMed

Mishra, S N

2009-03-18

Applying the time differential perturbed angular correlation (TDPAC) technique we have measured electric and magnetic hyperfine fields of the (111)Cd impurity in equi-atomic rare-earth intermetallic alloys RScGe (R = Ce, Pr and Gd) showing antiferro- and ferromagnetism with unusually high ordering temperatures. The Cd nuclei occupying the Sc site show high magnetic hyperfine fields with saturation values B(hf)(0) = 21 kG, 45 kG and 189 kG in CeScGe, PrScGe and GdScGe, respectively. By comparing the results with the hyperfine field data of Cd in rare-earth metals and estimations from the RKKY model, we find evidence for the presence of additional spin density at the probe nucleus, possibly due to spin polarization of Sc d band electrons. The principal electric field gradient component V(zz) in CeScGe, PrScGe and GdScGe has been determined to be 5.3 × 10(21) V m(-2), 5.5 × 10(21) V m(-2) and 5.6 × 10(21) V m(-2), respectively. Supplementing the experimental measurements, we have carried out ab initio calculations for pure and Cd-doped RScGe compounds with R = Ce, Pr, Nd and Gd using the full potential linearized augmented plane wave (FLAPW) method based on density functional theory (DFT). From the total energies calculated with and without spin polarization we find ferrimagnetic ground states for CeScGe and PrScGe while NdScGe and GdScGe are ferromagnetic. In addition, we find a sizable magnetic moment at the Sc site, increasing from ≈0.10 μ(B) in CeScGe to ≈0.3 μ(B) in GdScGe, confirming the spin polarization of Sc d band electrons. The calculated electric field gradient and magnetic hyperfine fields of the Cd impurity closely agree with the experimental values. We believe spin polarization of Sc 3d band electrons, strongly hybridized with spin polarized 5d band electrons of the rare-earth, enables a long range Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between RE 4f moments which in turn leads to high magnetic ordering temperatures in RScGe compounds.

Experimental observation and determination of the laser-induced frequency shift of hyperfine levels of ultracold polar molecules

NASA Astrophysics Data System (ADS)

Liu, Wenliang; Wang, Xiaofeng; Wu, Jizhou; Su, Xingliang; Wang, Shen; Sovkov, Vladimir B.; Ma, Jie; Xiao, Liantuan; Jia, Suotang

2017-08-01

We report on the experimental observation and quantitative determination of the laser-induced frequency shift (LIFS) of the ultracold polar molecules formed by photoassociation (PA). The experiments are performed by detecting a series of double PA spectra with a molecular hyperfine structure, which are induced by two PA lasers with a precise and adjustable frequency reference. We find that the LIFS of the molecular hyperfine levels shows a linear dependence on PA laser intensity.

57Fe Mössbauer study of unusual magnetic structure of multiferroic 3R-AgFeO2

NASA Astrophysics Data System (ADS)

Sobolev, A.; Rusakov, V.; Moskvin, A.; Gapochka, A.; Belik, A.; Glazkova, I.; Akulenko, A.; Demazeau, G.; Presniakov, I.

2017-07-01

We report new results of a 57Fe Mössbauer study of hyperfine magnetic interactions in the layered multiferroic 3R-AgFeO2 demonstrating two magnetic phase transitions at T N1 and T N2. The asymptotic value β *  ≈  0.34 for the critical exponent obtained from the temperature dependence of the hyperfine field H hf(T) at 57Fe the nuclei below T N1  ≈  14 K indicates that 3R-AgFeO2 shows quasi-3D critical behavior. The spectra just above T N1 (T N1  <  T  <  T  *  ≈  41 K) demonstrate a relaxation behavior due to critical spin fluctuations which indicates the occurrence of short-range correlations. At the intermediate temperature range, T N2  <  T  <  T N1, the 57Fe Mössbauer spectra are described in terms of collinear spin-density-waves (SDW) with the inclusion of many high-order harmonics, indicating that the real magnetic structure of the ferrite appears to be more complicated than a pure sinusoidally modulated SDW. Below T  <  T N2  ≈  9 K, the hyperfine field H hf reveals a large spatial anisotropy (ΔH anis  ≈  30 kOe) which is related with a local intra-cluster (FeO6) spin-dipole term that implies a conventional contribution of the polarized oxygen ions. We proposed a simple two-parametric formula to describe the dependence of H anis on the distortions of the (FeO6) clusters. Analysis of different mechanisms of spin and hyperfine interactions in 3R-AgFeO2 and its structural analogue CuFeO2 points to a specific role played by the topology of the exchange coupling and the oxygen polarization in the delafossite-like structures.

Practical method for transversely measuring the spin polarization of optically pumped alkali atoms

NASA Astrophysics Data System (ADS)

Ding, Zhichao; Yuan, Jie; Long, Xingwu

2018-06-01

A practical method to measure the spin polarization of optically pumped alkali atoms is demonstrated. In order to realize transverse measurement, the transverse spin component of spin-polarized alkali atoms is created by a rotating exciting magnetic field, and detected using the optical rotation of a near-resonant probe beam for realizing a high detection sensitivity. The dependency of the optical rotation on the spin polarization of 133Cs atoms is derived theoretically and verified experimentally. By changing the direction of the rotating magnetic field, we realize the transverse measurement of the spin polarization of 133Cs atoms in either ground-state hyperfine level.

Creating Spin-One Fermions in the Presence of Artificial Spin-Orbit Fields: Emergent Spinor Physics and Spectroscopic Properties

NASA Astrophysics Data System (ADS)

Kurkcuoglu, Doga Murat; de Melo, C. A. R. Sá

2018-05-01

We propose the creation and investigation of a system of spin-one fermions in the presence of artificial spin-orbit coupling, via the interaction of three hyperfine states of fermionic atoms to Raman laser fields. We explore the emergence of spinor physics in the Hamiltonian described by the interaction between light and atoms, and analyze spectroscopic properties such as dispersion relation, Fermi surfaces, spectral functions, spin-dependent momentum distributions and density of states. Connections to spin-one bosons and SU(3) systems is made, as well relations to the Lifshitz transition and Pomeranchuk instability are presented.

Integration of optically active Neodymium ions in Niobium devices (Nd:Nb): quantum memory for hybrid quantum entangled systems

NASA Astrophysics Data System (ADS)

Nayfeh, O. M.; Chao, D.; Djapic, N.; Sims, P.; Liu, B.; Sharma, S.; Lerum, L.; Fahem, M.; Dinh, V.; Zlatanovic, S.; Lynn, B.; Torres, C.; Higa, B.; Moore, J.; Upchurch, A.; Cothern, J.; Tukeman, M.; Barua, R.; Davidson, B.; Ramirez, A. D.; Rees, C. D.; Anant, V.; Kanter, G. S.

2017-08-01

Optically active rare-earth Neodymium (Nd) ions are integrated in Niobium (Nb) thin films forming a new quantum memory device (Nd:Nb) targeting long-lived coherence times and multi-functionality enabled by both spin and photon storage properties. Nb is implanted with Nd spanning 10-60 keV energy and 1013-1014 cm-2 dose producing a 1- 3% Nd:Nb concentration as confirmed by energy-dispersive X-ray spectroscopy. Scanning confocal photoluminescence (PL) at 785 nm excitation are made and sharp emission peaks from the 4F3/2 -< 4I11/2 Nd3+ transition at 1064-1070 nm are examined. In contrast, un-implanted Nb is void of any peaks. Line-shapes at room temperature are fit with Lorentzian profiles with line-widths of 4-5 nm and 1.3 THz bandwidth and the impacts of hyperfine splitting via the metallic crystal potential are apparent and the co-contribution of implant induced defects. With increasing Nd from 1% to 3%, there is a 0.3 nm red shift and increased broadening to a 4.8 nm linewidth. Nd:Nb is photoconductive and responds strongly to applied fields. Furthermore, optically detected magnetic resonance (ODMR) measurements are presented spanning near-infrared telecom band. The modulation of the emission intensity with magnetic field and microwave power by integration of these magnetic Kramer type Nd ions is quantified along with spin echoes under pulsed microwave π-π/2 excitation. A hybrid system architecture is proposed using spin and photon quantum information storage with the nuclear and electron states of the Nd3+ and neighboring Nb atoms that can couple qubit states to hyperfine 7/2 spin states of Nd:Nb and onto NIR optical levels excitable with entangled single photons, thus enabling implementation of computing and networking/internet protocols in a single platform.

Disentangling overlapping high-field EPR spectra of organic radicals: Identification of light-induced polarons in the record fullerene-free solar cell blend PBDB-T:ITIC

NASA Astrophysics Data System (ADS)

Van Landeghem, Melissa; Maes, Wouter; Goovaerts, Etienne; Van Doorslaer, Sabine

2018-03-01

We present a combined high-field EPR and DFT study of light-induced radicals in the bulk heterojunction blend of PBDB-T:ITIC, currently one of the highest efficiency non-fullerene donor:acceptor combinations in organic photovoltaics. We demonstrate two different approaches for disentangling the strongly overlapping high-field EPR spectra of the positive and negative polarons after charge separation: (1) relaxation-filtered field-swept EPR based on the difference in T1 spin-relaxation times and (2) field-swept EDNMR-induced EPR by exploiting the presence of 14N hyperfine couplings in only one of the radical species, the small molecule acceptor radical. The approach is validated by light-induced EPR spectra on related blends and the spectral assignment is underpinned by DFT computations. The broader applicability of the spectral disentangling methods is discussed.

LOCAL MAGNETIC BEHAVIOR OF 54Fe in EuFe2As2 AND Eu0.5K0.5Fe2As2: MICROSCOPIC STUDY USING TIME DIFFERENTIAL PERTURBED ANGULAR DISTRIBUTION (TDPAD) SPECTROSCOPY

NASA Astrophysics Data System (ADS)

Mohanta, S. K.; Mishra, S. N.; Davane, S. M.; Layek, S.; Hossain, Z.

2013-12-01

In this paper, we report the time differential perturbed angular distribution measurements of 54Fe on a polycrystalline EuFe2As2 and Eu0.5K0.5Fe2As2. The hyperfine field and nuclear spin-relaxation rate are strongly temperature dependent in the paramagnetic state suggesting strong spin fluctuation in the parent compound. The local susceptibility show Curie-Weiss-like temperature dependence and Korringa-like relaxation in the tetragonal phase indicating the presence of local moment. In the orthorhombic phase, the hyperfine field behavior suggesting quasi two-dimensional magnetic ordering. The experimental results are in a good agreement with first-principle calculations based on density functional theory.

Electrical detection of proton-spin motion in a polymer device at room temperature

NASA Astrophysics Data System (ADS)

Boehme, Christoph

With the emergence of spintronics concepts based on organic semiconductors there has been renewed interest in the role of both, electron as well as nuclear spin states for the magneto-optoelectronic properties of these materials. In spite of decades of research on these molecular systems, there is still much need for an understanding of some of the fundamental properties of spin-controlled charge carrier transport and recombination processes. This presentation focuses on mechanisms that allow proton spin states to influence electronic transition rates in organic semiconductors. Remarkably, even at low-magnetic field conditions and room temperature, nuclear spin states with energy splittings orders of magnitude below thermal energies are able to influence observables like magnetoresistance and fluorescence. While proton spins couple to charge carrier spins via hyperfine interaction, there has been considerable debate about the nature of the electronic processes that are highly susceptible to these weak hyperfine fields. Here, experiments are presented which show how the magnetic resonant manipulation of electron and nuclear spin states in a π-conjugated polymer device causes changes of the device current. The experiments confirm the extraordinary sensitivity of electronic transitions to very weak magnetic field changes and underscore the potential significance of spin-selection rules for highly sensitive absolute magnetic fields sensor concepts. However, the relevance of these magnetic-field sensitive spin-dependent electron transitions is not just limited to semiconductor materials but also radical pair chemistry and even avian magnetoreceptors This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award #DE-SC0000909. The Utah NSF - MRSEC program #DMR 1121252 is acknowledged for instrumentation support.

Modification of structural and magnetic properties of soft magnetic multi-component metallic glass by 80 MeV 16O6+ ion irradiation

NASA Astrophysics Data System (ADS)

Kane, S. N.; Shah, M.; Satalkar, M.; Gehlot, K.; Kulriya, P. K.; Avasthi, D. K.; Sinha, A. K.; Modak, S. S.; Ghodke, N. L.; Reddy, V. R.; Varga, L. K.

2016-07-01

Effect of 80 MeV 16O6+ ion irradiation in amorphous Fe77P8Si3C5Al2Ga1B4 alloy is reported. Electronic energy loss induced modifications in the structural and, magnetic properties were monitored by synchrotron X-ray diffraction (SXRD), Mössbauer and, magnetic measurements. Broad amorphous hump seen in SXRD patterns reveals the amorphous nature of the studied specimens. Mössbauer measurements suggest that: (a) alignment of atomic spins within ribbon plane, (b) changes in average hyperfine field suggests radiation-induced decrease in the inter atomic distance around Mössbauer (Fe) atom, (c) hyperfine field distribution confirms the presence of non-magnetic elements (e.g. - B, P, C) in the first near-neighbor shell of the Fe atom, thus reducing its magnetic moment, and (d) changes in isomer shift suggests variation in average number of the metalloid near neighbors and their distances. Minor changes in soft magnetic behavior - watt loss and, coercivity after an irradiation dose of 2 × 1013 ions/cm2 suggests prospective application of Fe77P8Si3C5Al2Ga1B4 alloy as core material in accelerators (radio frequency cavities).

Rabi oscillation and electron-spin-echo envelope modulation of the photoexcited triplet spin system in silicon

NASA Astrophysics Data System (ADS)

Akhtar, Waseem; Sekiguchi, Takeharu; Itahashi, Tatsumasa; Filidou, Vasileia; Morton, John J. L.; Vlasenko, Leonid; Itoh, Kohei M.

2012-09-01

We report on a pulsed electron paramagnetic resonance (EPR) study of the photoexcited triplet state (S=1) of oxygen-vacancy centers in silicon. Rabi oscillations between the triplet sublevels are observed using coherent manipulation with a resonant microwave pulse. The Hahn echo and stimulated echo decay profiles are superimposed with strong modulations known as electron-spin-echo envelope modulation (ESEEM). The ESEEM spectra reveal a weak but anisotropic hyperfine coupling between the triplet electron spin and a 29Si nuclear spin (I=1/2) residing at a nearby lattice site, that cannot be resolved in conventional field-swept EPR spectra.

Room-temperature coupling between electrical current and nuclear spins in OLEDs

NASA Astrophysics Data System (ADS)

Malissa, H.; Kavand, M.; Waters, D. P.; van Schooten, K. J.; Burn, P. L.; Vardeny, Z. V.; Saam, B.; Lupton, J. M.; Boehme, C.

2014-09-01

The effects of external magnetic fields on the electrical conductivity of organic semiconductors have been attributed to hyperfine coupling of the spins of the charge carriers and hydrogen nuclei. We studied this coupling directly by implementation of pulsed electrically detected nuclear magnetic resonance spectroscopy in organic light-emitting diodes (OLEDs). The data revealed a fingerprint of the isotope (protium or deuterium) involved in the coherent spin precession observed in spin-echo envelope modulation. Furthermore, resonant control of the electric current by nuclear spin orientation was achieved with radiofrequency pulses in a double-resonance scheme, implying current control on energy scales one-millionth the magnitude of the thermal energy.

ESR, electrochemical and cyclodextrin-inclusion studies of triazolopyridyl pyridyl ketones and dipyridyl ketones derivatives

NASA Astrophysics Data System (ADS)

Olea-Azar, C.; Abarca, B.; Norambuena, E.; Opazo, L.; Jullian, C.; Valencia, S.; Ballesteros, R.; Chadlaoui, M.

2008-11-01

The electron spin resonance (ESR) spectra of free radicals obtained by electrolytic reduction of triazolopyridyl pyridyl ketones and dipyridyl ketones derivatives were measured in dimethylsulfoxide (DMSO). The hyperfine patterns indicate that the spin density delocalization is dependent of the rings presented in the molecule. The electrochemistry of these compounds was characterized using cyclic voltammetry, in DMSO as solvent. When one carbonyl is present in the molecule one step in the reduction mechanism was observed while two carbonyl are present two steps were detected. The first wave was assigned to the generation of the correspondent free radical species, and the second wave was assigned to the dianion derivatives. The phase-solubility measurements indicated an interaction between molecules selected and cyclodextrins in water. These inclusion complexes are 1:1 with βCD, and HP-βCD. The values of Ks showed a different kind of complexes depending on which rings are included. AM1 and DFT calculations were performed to obtain the optimized geometries, theoretical hyperfine constants, and spin distributions, respectively. The theoretical results are in complete agreement with the experimental ones.

Theoretical research on the spin-Hamiltonian parameters of the rhombic W5+ centers in CaWO4:Y3+ crystal

NASA Astrophysics Data System (ADS)

Mei, Yang; Wei, Cheng-Fu; Zheng, Wen-Chen

2016-02-01

Detailed theoretical calculations for the spin-Hamiltonian parameters (g factors gi and hyperfine structure constants Ai, where i=x, y, z) of the rhombic W5+ center in CaWO4:Y3+ crystal are performed by using the high-order perturbation formulas for d1 ions in rhombic tetrahedral clusters with the ground state |dz2>. These formulas consist of the contributions from two mechanisms, the crystal-field (CF) mechanism connected with CF excited states in the vastly-used CF theory and the frequently-neglected charge-transfer (CT) mechanism related to CT excited states. The calculated results agree well with the experimental values. The calculations indicate that for W5+ ion (or other high valence state dn ions) in crystals, the model calculations of spin-Hamiltonian parameters should take both the CF and CT mechanisms into account. The signs of hyperfine structure constants Ai are suggested and the forming (or defect model) of rhombic W5+ center in CaWO4:Y3+ crystal is confirmed from the calculations.

Quantum simulation of interacting spin models with trapped ions

NASA Astrophysics Data System (ADS)

Islam, Kazi Rajibul

The quantum simulation of complex many body systems holds promise for understanding the origin of emergent properties of strongly correlated systems, such as high-Tc superconductors and spin liquids. Cold atomic systems provide an almost ideal platform for quantum simulation due to their excellent quantum coherence, initialization and readout properties, and their ability to support several forms of interactions. In this thesis, I present experiments on the quantum simulation of long range Ising models in the presence of transverse magnetic fields with a chain of up to sixteen ultracold 171Yb+ ions trapped in a linear radio frequency Paul trap. Two hyperfine levels in each of the 171Yb+ ions serve as the spin-1/2 systems. We detect the spin states of the individual ions by observing state-dependent fluorescence with single site resolution, and can directly measure any possible spin correlation function. The spin-spin interactions are engineered by applying dipole forces from precisely tuned lasers whose beatnotes induce stimulated Raman transitions that couple virtually to collective phonon modes of the ion motion. The Ising couplings are controlled, both in sign and strength with respect to the effective transverse field, and adiabatically manipulated to study various aspects of this spin model, such as the emergence of a quantum phase transition in the ground state and spin frustration due to competing antiferromagnetic interactions. Spin frustration often gives rise to a massive degeneracy in the ground state, which can lead to entanglement in the spin system. We detect and characterize this frustration induced entanglement in a system of three spins, demonstrating the first direct experimental connection between frustration and entanglement. With larger numbers of spins we also vary the range of the antiferromagnetic couplings through appropriate laser tunings and observe that longer range interactions reduce the excitation energy and thereby frustrate the ground state order. This system can potentially be scaled up to study a wide range of fully connected spin networks with a few dozens of spins, where the underlying theory becomes intractable on a classical computer.

Hyperfine structure of excited states and quadrupole moment of Ne-21 using laser-induced line-narrowing techniques.

NASA Technical Reports Server (NTRS)

Ducas, T. W.; Feld, M. S.; Ryan, L. W., Jr.; Skribanowitz, N.; Javan, A.

1972-01-01

Observation results are presented on the optical hyperfine structure in Ne-21 obtained with the aid of laser-induced line-narrowing techniques. The output from a long stabilized single-mode 1.15-micron He-Ne laser focused into an external sample cell containing Ne-21 was used in implementing these techniques. Their applicability is demonstrated for optical hyperfine structure observation in systems whose features are ordinarily masked by Doppler broadening.

Dynamics of 4-oxo-TEMPO-d16-15N nitroxide-propylene glycol system studied by ESR and ESE in liquid and glassy state in temperature range 10-295 K

NASA Astrophysics Data System (ADS)

Goslar, Janina; Hoffmann, Stanislaw K.; Lijewski, Stefan

2016-08-01

ESR spectra and electron spin relaxation of nitroxide radical in 4-oxo-TEMPO-d16-15N in propylene glycol were studied at X-band in the temperature range 10-295 K. The spin-lattice relaxation in the liquid viscous state determined from the resonance line shape is governed by three mechanisms occurring during isotropic molecular reorientations. In the glassy state below 200 K the spin-lattice relaxation, phase relaxation and electron spin echo envelope modulations (ESEEM) were studied by pulse spin echo technique using 2-pulse and 3-pulse induced signals. Electron spin-lattice relaxation is governed by a single non-phonon relaxation process produced by localized oscillators of energy 76 cm-1. Electron spin dephasing is dominated by a molecular motion producing a resonance-type peak in the temperature dependence of the dephasing rate around 120 K. The origin of the peak is discussed and a simple method for the peak shape analysis is proposed, which gives the activation energy of a thermally activated motion Ea = 7.8 kJ/mol and correlation time τ0 = 10-8 s. The spin echo amplitude is strongly modulated and FT spectrum contains a doublet of lines centered around the 2D nuclei Zeeman frequency. The splitting into the doublet is discussed as due to a weak hyperfine coupling of nitroxide unpaired electron with deuterium of reorienting CD3 groups.

The dynamics of the optically driven Lambda transition of the 15N-V- center in diamond.

PubMed

González, Gabriel; Leuenberger, Michael N

2010-07-09

Recent experimental results demonstrate the possibility of writing quantum information in the ground state triplet of the (15)N-V(-) center in diamond by means of an optically driven spin non-conserving two-photon Lambda transition in the presence of a strong applied electric field. Our calculations show that the hyperfine interaction in the (15)N-V(-) center is capable of mediating such a transition. We use a density matrix approach to describe the exact dynamics for the allowed optical spin non-conserving transitions between two sublevels of the ground state triplet. This approach allows us to calculate the Rabi oscillations, by means of which we obtain a Rabi frequency with an upper bound determined by the hyperfine interaction. This result is crucial for the success of implementing optically driven quantum information processing with the N-V center in diamond.

Magnetic properties and hyperfine interactions in Cr{sub 8}, Cr{sub 7}Cd, and Cr{sub 7}Ni molecular rings from {sup 19}F-NMR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bordonali, L.; Borsa, F.; Consorzio INSTM, Via Giusti 9, I-50121 Firenze

2014-04-14

A detailed experimental investigation of the {sup 19}F nuclear magnetic resonance is made on single crystals of the homometallic Cr{sub 8} antiferromagnetic molecular ring and heterometallic Cr{sub 7}Cd and Cr{sub 7}Ni rings in the low temperature ground state. Since the F{sup −} ion is located midway between neighboring magnetic metal ions in the ring, the {sup 19}F-NMR spectra yield information about the local electronic spin density and {sup 19}F hyperfine interactions. In Cr{sub 8}, where the ground state is a singlet with total spin S{sub T} = 0, the {sup 19}F-NMR spectra at 1.7 K and low external magnetic fieldmore » display a single narrow line, while when the magnetic field is increased towards the first level crossing field, satellite lines appear in the {sup 19}F-NMR spectrum, indicating a progressive increase in the Boltzmann population of the first excited state S{sub T} = 1. In the heterometallic rings, Cr{sub 7}Cd and Cr{sub 7}Ni, whose ground state is magnetic with S{sub T} = 3/2 and S{sub T} = 1/2, respectively, the {sup 19}F-NMR spectrum has a complicated structure which depends on the strength and orientation of the magnetic field, due to both isotropic and anisotropic transferred hyperfine interactions and classical dipolar interactions. From the {sup 19}F-NMR spectra in single crystals we estimated the transferred hyperfine constants for both the F{sup −}-Ni{sup 2+} and the F{sup −}-Cd{sup 2+} bonds. The values of the hyperfine constants compare well to the ones known for F{sup −}-Ni{sup 2+} in KNiF{sub 3} and NiF{sub 2} and for F{sup −}-Cr{sup 3+} in K{sub 2}NaCrF{sub 6}. The results are discussed in terms of hybridization of the 2s, 2p orbitals of the F{sup −} ion and the d orbitals of the magnetic ion. Finally, we discuss the implications of our results for the electron-spin decoherence.« less

Effect of Jahn-Teller ion in zinc sodium sulphate hexahydrate: a case of low hyperfine coupling constant for Cu(II) ion

NASA Astrophysics Data System (ADS)

Naidu, K. C.; Shiyamala, C.; Mithira, S.; Natarajan, B.; Venkatesan, R.; Rao, P. S.

2005-06-01

Single crystal electron paramagnetic resonance (EPR) studies of Cu(II) doped zinc sodium sulphate hexahydrate are carried out from room temperature (RT) to 123 K. The RT spectra show unresolved hyperfine lines and hence angular variation studies are also carried out at 123 K to obtain spin Hamiltonian parameters. The spin Hamiltonian parameters calculated from the 123 K spectra are: g(11)=2.039, g(22)=2.232, g(33)=2.394, A(11)=5.64 mT, A(22)=4.20 mT, and A(33)=7.94 mT. The g-matrix values at RT and 123 K have matched fairly well with each other. The low hyperfine value (A(33)), obtained at 123 K, has been explained by considering considerable admixture of d(x 2-y 2) ground state with d(z 2) excited state and the delocalization of the unpaired spin density onto the ligands. The admixture coefficients of ground state wave function are: a=0.346, b=0.935, c=0.055, d=0.040, e=-0.040, where a and b correspond to admixture coefficients for d(z 2) and d(x 2-y 2), respectively. Angular variation of Cu(II) resonances in the three orthogonal axes shows that the impurity has entered a substitutional site in the host lattice in place of Zn(II). Bonding parameters, kappa=0.295, P=245.4x10(-4), alpha(2)=0.709, alpha=0.8421 and alpha'=0.6034, have also been calculated to fully characterize the EPR.

ENDOR with band-selective shaped inversion pulses

NASA Astrophysics Data System (ADS)

Tait, Claudia E.; Stoll, Stefan

2017-04-01

Electron Nuclear DOuble Resonance (ENDOR) is based on the measurement of nuclear transition frequencies through detection of changes in the polarization of electron transitions. In Davies ENDOR, the initial polarization is generated by a selective microwave inversion pulse. The rectangular inversion pulses typically used are characterized by a relatively low selectivity, with full inversion achieved only for a limited number of spin packets with small resonance offsets. With the introduction of pulse shaping to EPR, the rectangular inversion pulses can be replaced with shaped pulses with increased selectivity. Band-selective inversion pulses are characterized by almost rectangular inversion profiles, leading to full inversion for spin packets with resonance offsets within the pulse excitation bandwidth and leaving spin packets outside the excitation bandwidth largely unaffected. Here, we explore the consequences of using different band-selective amplitude-modulated pulses designed for NMR as the inversion pulse in ENDOR. We find an increased sensitivity for small hyperfine couplings compared to rectangular pulses of the same bandwidth. In echo-detected Davies-type ENDOR, finite Fourier series inversion pulses combine the advantages of increased absolute ENDOR sensitivity of short rectangular inversion pulses and increased sensitivity for small hyperfine couplings of long rectangular inversion pulses. The use of pulses with an almost rectangular frequency-domain profile also allows for increased control of the hyperfine contrast selectivity. At X-band, acquisition of echo transients as a function of radiofrequency and appropriate selection of integration windows during data processing allows efficient separation of contributions from weakly and strongly coupled nuclei in overlapping ENDOR spectra within a single experiment.

Spin Biochemistry Modulates Reactive Oxygen Species (ROS) Production by Radio Frequency Magnetic Fields

PubMed Central

Usselman, Robert J.; Hill, Iain; Singel, David J.; Martino, Carlos F.

2014-01-01

The effects of weak magnetic fields on the biological production of reactive oxygen species (ROS) from intracellular superoxide (O2 •−) and extracellular hydrogen peroxide (H2O2) were investigated in vitro with rat pulmonary arterial smooth muscle cells (rPASMC). A decrease in O2 •− and an increase in H2O2 concentrations were observed in the presence of a 7 MHz radio frequency (RF) at 10 μTRMS and static 45 μT magnetic fields. We propose that O2 •− and H2O2 production in some metabolic processes occur through singlet-triplet modulation of semiquinone flavin (FADH•) enzymes and O2 •− spin-correlated radical pairs. Spin-radical pair products are modulated by the 7 MHz RF magnetic fields that presumably decouple flavin hyperfine interactions during spin coherence. RF flavin hyperfine decoupling results in an increase of H2O2 singlet state products, which creates cellular oxidative stress and acts as a secondary messenger that affects cellular proliferation. This study demonstrates the interplay between O2 •− and H2O2 production when influenced by RF magnetic fields and underscores the subtle effects of low-frequency magnetic fields on oxidative metabolism, ROS signaling, and cellular growth. PMID:24681944

Coherence time of over a second in a telecom-compatible quantum memory storage material

NASA Astrophysics Data System (ADS)

Rančić, Miloš; Hedges, Morgan P.; Ahlefeldt, Rose L.; Sellars, Matthew J.

2018-01-01

Quantum memories for light will be essential elements in future long-range quantum communication networks. These memories operate by reversibly mapping the quantum state of light onto the quantum transitions of a material system. For networks, the quantum coherence times of these transitions must be long compared to the network transmission times, approximately 100 ms for a global communication network. Due to a lack of a suitable storage material, a quantum memory that operates in the 1,550 nm optical fibre communication band with a storage time greater than 1 μs has not been demonstrated. Here we describe the spin dynamics of 167Er3+: Y2SiO5 in a high magnetic field and demonstrate that this material has the characteristics for a practical quantum memory in the 1,550 nm communication band. We observe a hyperfine coherence time of 1.3 s. We also demonstrate efficient spin pumping of the entire ensemble into a single hyperfine state, a requirement for broadband spin-wave storage. With an absorption of 70 dB cm-1 at 1,538 nm and Λ transitions enabling spin-wave storage, this material is the first candidate identified for an efficient, broadband quantum memory at telecommunication wavelengths.

Sub-Doppler infrared spectroscopy of propargyl radical (H{sub 2}CCCH) in a slit supersonic expansion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Chih-Hsuan; Nesbitt, David J.

The acetylenic CH stretch mode (ν{sub 1}) of propargyl (H{sub 2}CCCH) radical has been studied at sub-Doppler resolution (∼60 MHz) via infrared laser absorption spectroscopy in a supersonic slit-jet discharge expansion, where low rotational temperatures (T{sub rot} = 13.5(4) K) and lack of spectral congestion permit improved determination of band origin and rotational constants for the excited state. For the lowest J states primarily populated in the slit jet cooled expansion, fine structure due to the unpaired electron spin is resolved completely, which permits accurate analysis of electron spin-rotation interactions in the vibrationally excited states (ε{sub aa} = − 518.1(1.8),more » ε{sub bb} = − 13.0(3), ε{sub cc} = − 1.8(3) MHz). In addition, hyperfine broadening in substantial excess of the sub-Doppler experimental linewidths is observed due to nuclear spin–electron spin contributions at the methylenic (—CH{sub 2}) and acetylenic (—CH) positions, which permits detailed modeling of the fine/hyperfine structure line contours. The results are consistent with a delocalized radical spin density extending over both methylenic and acetylenic C atoms, in excellent agreement with simple resonance structures as well as ab initio theoretical calculations.« less

Paramagnetic species on catalytic surfaces--DFT investigations into structure sensitivity of the hyperfine coupling constants.

PubMed

Sojka, Zbigniew; Pietrzyk, Piotr

2004-05-01

Structure sensitivity of the hyperfine coupling constants was investigated by means of DFT calculations for selected surface paramagnetic species. A *CH2OH radical trapped on silica and intrazeolite copper nitrosyl adducts encaged in ZSM-5 were taken as the examples. The surface of amorphous silica was modeled with a [Si5O8H10] cluster, whereas the zeolite hosting sites were epitomized by [Si4AlO5(OH)10]- cluster. Three different coordination modes of the *CH2OH radical were considered and the isotropic 13C and 1H hyperfine constants of the resultant van der Waals complexes, calculated with B3LYP/6-311G(d), were discussed in terms of the angular deformations caused by hydrogen bonds with the cluster. The magnetic parameters of the eta1-N[CuNO]11 and eta1-O[CuNO]11 linkage isomers were calculated at the BPW91/LanL2DZ and 6-311G(df) level. For the most stable eta1-N adduct a clear dependence of the spin density distribution within the Cu-NO moiety on changes in the Cu-N-O angle and the Cu-N bond distance was observed and accounted for by varying spin polarization and delocalization contributions.

Electric dipole moment of diatomic molecules by configuration interaction. V - Two states of /2/Sigma/+/ symmetry in CN.

NASA Technical Reports Server (NTRS)

Green, S.

1972-01-01

Previous accurate dipole moment calculation techniques are modified to be applicable to higher excited states of symmetry. The self-consistent fields and configuration interactions are calculated for the X(2)Sigma(+) and B(2)Sigma(+) states of CN. Spin hyperfine constants and spin density at the nucleus are considered in the context of one-electron operator properties. The values of the self-consistent field and configuration interaction for the spin density are compared with experimental values for several diatomic molecules.

Cobalt spin states and hyperfine interactions in LaCoO3 investigated by LDA+U calculations

NASA Astrophysics Data System (ADS)

Hsu, Han; Blaha, Peter; Wentzcovitch, Renata M.; Leighton, C.

2010-09-01

With a series of local-density approximation plus Hubbard U calculations, we have demonstrated that for lanthanum cobaltite (LaCoO3) , the electric field gradient at the cobalt nucleus can be used as a fingerprint to identify the spin state of the cobalt ion. Therefore, in principle, the spin state of the cobalt ion can be unambiguously determined from nuclear magnetic resonance spectra. Our calculations also suggest that a crossover from the low-spin to intermediate-spin state in the temperature range of 0-90 K is unlikely, based on the half-metallic band structure associated with isolated IS Co ions, which is incompatible with the measured conductivity.

Spin noise spectroscopy of donor-bound electrons in ZnO

NASA Astrophysics Data System (ADS)

Horn, H.; Balocchi, A.; Marie, X.; Bakin, A.; Waag, A.; Oestreich, M.; Hübner, J.

2013-01-01

We investigate the intrinsic spin dynamics of electrons bound to Al impurities in bulk ZnO by optical spin noise spectroscopy. Spin noise spectroscopy enables us to investigate the longitudinal and transverse spin relaxation time with respect to nuclear and external magnetic fields in a single spectrum. On one hand, the spin dynamic is dominated by the intrinsic hyperfine interaction with the nuclear spins of the naturally occurring 67Zn isotope. We measure a typical spin dephasing time of 23 ns, in agreement with the expected theoretical values. On the other hand, we measure a third, very high spin dephasing rate which is attributed to a high defect density of the investigated ZnO material. Measurements of the spin dynamics under the influence of transverse as well as longitudinal external magnetic fields unambiguously reveal the intriguing connections of the electron spin with its nuclear and structural environment.

Studies of molecular physics in sodium-potassium: An analysis of the 4(3)Sigma+ state and interactions between the 2(A)(1)Sigma+ and 1(b)(3)Pi states

NASA Astrophysics Data System (ADS)

Burns, Patrick

2004-12-01

In this dissertation we report the results of three experiments designed to provide new information on the structure and interactions of the NaK molecule. Specifically these experiments investigate 2(A)1Sigma +(upsilonA, J) + M → 1(b)3 pi0(upsilonb, J) + M collisional excitation transfers (where M is a collision partner), hyperfine structure of the NaK 1(b)3pi and 1(b)3pi0 ˜ 2(A)1Sigma+ spin-orbit interactions, and the structure and spectra of the NaK 43Sigma+ state, respectively. In this first experiment, populations of collisionally populated levels were recorded near the NaK 1(b)3pi0(upsilon =18, J = 44) ˜ 2(A)1Sigma+ (upsilon = 20, J = 44) center of spin-orbit perturbation. Our data indicate that population is transferred from the pumped level, 2(A) 1Sigma+(upsilon = 20, J = 49), directly to the surrounding "daughter" levels [1(b)3Sigma 0(upsilon =18, J = 45--48) and 2(A)1Sigma +(upsilon = 20, J = 45--48)]. The relative populations of the daughter levels appear anomalous, as their populations do not monotonically decrease for levels further away in energy from the pumped level. We have measured the hyperfine structure of mutually perturbing ro-vibrational levels of the 1(b)3pi0 and 2(A)1Sigma + states of the NaK molecule, using the PFOODR method with co-propagating lasers. Unperturbed 1(b)3pi0 levels are split into four hyperfine components by the Fermi contact interaction b FI·S. Mixing between the 1(b)3pi0 and 2(A)1Sigma + levels imparts hyperfine structure to the nominally singlet component, and reduces the hyperfine splitting of the nominally triplet component, of the perturbed levels. We determined a value for the Fermi constant, bF= (0.00989 +/- 0.00027) cm-1, and the magnitude of the electronic part of the 1(b)3pi 0 ˜ 2(A)1Sigma+ spin-orbit coupling, |Hel| = (15.65 +/- 0.14) cm-1 , from an analysis of the measured hyperfine splittings of the mixed singlet-triplet levels. High-resolution spectra have been observed for numerous vibrational-rotational levels (upsilon, N) of the 43Sigma + state of NaK. A potential curve was obtained from the data using the inverse perturbation approximation method. Measured bound-free emission, 43Sigma+ → 1(a)3Sigma +, was used to determine both the absolute vibrational numbering and the transition dipole moment function M(R). Each (upsilon, N) level is typically split into three sets of sublevels by the Fermi contact interaction bFI·S. Further splitting (of order 0.004 cm-1) has been attributed to the spin-rotation interaction gammaN·S. The values of bF that fit the data best are ˜(0.99 +/- 0.04) x 10-2 cm-1, with weak dependence on upsilon. The best fit values of gamma are in the range 1--6 x 10-4 cm-1 and depend strongly on upsilon.

Radiation effects in x-irradiated hydroxy compounds

NASA Astrophysics Data System (ADS)

Budzinski, Edwin E.; Potter, William R.; Box, Harold C.

1980-01-01

Radiation effects are compared in single crystals of xylitol, sorbitol, and dulcitol x-irradiated at 4.2 °K. In xylitol and dulcitol, but not in sorbitol, a primary oxidation product is identified as an alkoxy radical. ENDOR measurements detected three proton hyperfine couplings associated with the alkoxy ESR absorption, one of which is attributed to a proton three bond lengths removed from the seat of unpaired spin density. Intermolecular trapping of electrons is observed in all three crystals. ENDOR measurements were made of the hyperfine couplings between the trapped electron and the hydroxy protons forming the trap.

ENDOR/ESR of Mn atoms and MnH molecules in solid argon

NASA Astrophysics Data System (ADS)

van Zee, R. J.; Garland, D. A.; Weltner, W., Jr.

1986-09-01

Mn atoms and MnH molecules, the latter formed by reaction between metal and hydrogen atoms, were trapped in solid argon and their ESR/ENDOR spectra measured at 4 K. At each pumping magnetic field two ENDOR lines were observed for 55Mn(I=5/2) atoms, corresponding to hyperfine transitions within the MS =±1/2 levels. Values of the hyperfine interaction constant and nuclear moment of 55Mn were derived from the six sets of data. For MnH, three sets of signals were detected: a proton ``matrix ENDOR'' line, transitions in the MS =0,±1 levels involving MI (55Mn)=1/2, 3/2, 5/2 levels, and proton transitions corresponding to νH and νH±aH. Analysis yielded the hyperfine constant aH =6.8(1) MHz and the nuclear quadrupole coupling constant Q'(55Mn)=-11.81(2) MHz. The latter compared favorably with a theoretical value derived earlier by Bagus and Schaefer. A higher term in the spin Hamiltonian appeared to be necessary to fit the proton hyperfine data.

Disentangling overlapping high-field EPR spectra of organic radicals: Identification of light-induced polarons in the record fullerene-free solar cell blend PBDB-T:ITIC.

PubMed

Van Landeghem, Melissa; Maes, Wouter; Goovaerts, Etienne; Van Doorslaer, Sabine

2018-03-01

We present a combined high-field EPR and DFT study of light-induced radicals in the bulk heterojunction blend of PBDB-T:ITIC, currently one of the highest efficiency non-fullerene donor:acceptor combinations in organic photovoltaics. We demonstrate two different approaches for disentangling the strongly overlapping high-field EPR spectra of the positive and negative polarons after charge separation: (1) relaxation-filtered field-swept EPR based on the difference in T 1 spin-relaxation times and (2) field-swept EDNMR-induced EPR by exploiting the presence of 14 N hyperfine couplings in only one of the radical species, the small molecule acceptor radical. The approach is validated by light-induced EPR spectra on related blends and the spectral assignment is underpinned by DFT computations. The broader applicability of the spectral disentangling methods is discussed. Copyright © 2018 Elsevier Inc. All rights reserved.

Aggregate frequency width, nuclear hyperfine coupling and Jahn-Teller effect of Cu2+ impurity ion ESR in SrLaAlO4 dielectric resonator at 20 millikelvin

NASA Astrophysics Data System (ADS)

Hosain, M. A.; Le Floch, J.-M.; Krupka, J.; Tobar, M. E.

2018-01-01

The impurity paramagnetic ion, Cu2+ substitutes Al in the SrLaAlO4 single crystal lattice, this results in a CuO6 elongated octahedron, and the resulting measured g-factors satisfy four-fold axes variation condition. The aggregate frequency width of the electron spin resonance with the required minimum level of impurity concentration has been evaluated in this single crystal SrLaAlO4 at 20 millikelvin. Measured parallel hyperfine constants, A\\Vert Cu , were determined to be -155.7×10-4~cm-1, ~ -163.0×10-4~cm-1, ~ -178.3×10-4~cm-1 and -211.1×10-4~cm-1 at 9.072~GHz~(WGH4, 1, 1) for the nuclear magnetic quantum number M_I=+\\frac{3}{2}, +\\frac{1}{2}, -\\frac{1}{2} , and -\\frac{3}{2} respectively. The anisotropy of the hyperfine structure reveals the characteristics of the static Jahn-Teller effect. The second-order-anisotropy term, ˜ (\\fracspin{-orbit~coupling}{10D_q}){\\hspace{0pt}}2 , is significant and cannot be disregarded, with the local strain dominating over the observed Zeeman-anisotropy-energy difference. The Bohr electron magneton, β=9.23× 10-24 JT-1 , (within -0.43% so-called experimental error) has been found using the measured spin-Hamiltonian parameters. Measured nuclear dipolar hyperfine structure parameter P\\Vert=12.3×10-4~cm-1 shows that the mean inverse third power of the electron distance from the nucleus is < r-3_q>≃ 5.23 a.u. for Cu2+ ion in the substituted Al3+ ion site assuming nuclear electric quadruple moment Q=-0.211 barn.

Spin-dependent recombination probed through the dielectric polarizability

PubMed Central

Bayliss, Sam L.; Greenham, Neil C.; Friend, Richard H.; Bouchiat, Hélène; Chepelianskii, Alexei D

2015-01-01

Despite residing in an energetically and structurally disordered landscape, the spin degree of freedom remains a robust quantity in organic semiconductor materials due to the weak coupling of spin and orbital states. This enforces spin-selectivity in recombination processes which plays a crucial role in optoelectronic devices, for example, in the spin-dependent recombination of weakly bound electron-hole pairs, or charge-transfer states, which form in a photovoltaic blend. Here, we implement a detection scheme to probe the spin-selective recombination of these states through changes in their dielectric polarizability under magnetic resonance. Using this technique, we access a regime in which the usual mixing of spin-singlet and spin-triplet states due to hyperfine fields is suppressed by microwave driving. We present a quantitative model for this behaviour which allows us to estimate the spin-dependent recombination rate, and draw parallels with the Majorana–Brossel resonances observed in atomic physics experiments. PMID:26439933

Mean link versus average plaquette tadpoles in lattice NRQCD

NASA Astrophysics Data System (ADS)

Shakespeare, Norman H.; Trottier, Howard D.

1999-03-01

We compare mean-link and average plaquette tadpole renormalization schemes in the context of the quarkonium hyperfine splittings in lattice NRQCD. Simulations are done for the three quarkonium systems c overlinec, b overlinec, and b overlineb. The hyperfine splittings are computed both at leading and at next-to-leading order in the relativistic expansion. Results are obtained at a large number of lattice spacings. A number of features emerge, all of which favor tadpole renormalization using mean links. This includes much better scaling of the hyperfine splittings in the three quarkonium systems. We also find that relativistic corrections to the spin splittings are smaller with mean-link tadpoles, particularly for the c overlinec and b overlinec systems. We also see signs of a breakdown in the NRQCD expansion when the bare quark mass falls below about one in lattice units (with the bare quark masses turning out to be much larger with mean-link tadpoles).

Proton, muon and ¹³C hyperfine coupling constants of C₆₀X and C₇₀X (X = H, Mu).

PubMed

Brodovitch, Jean-Claude; Addison-Jones, Brenda; Ghandi, Khashayar; McKenzie, Iain; Percival, Paul W

2015-01-21

The reaction of H atoms with fullerene C70 has been investigated by identifying the radical products formed by addition of the atom muonium (Mu) to the fullerene in solution. Four of the five possible radical isomers of C70Mu were detected by avoided level-crossing resonance (μLCR) spectroscopy, using a dilute solution of enriched (13)C70 in decalin. DFT calculations were used to predict muon and (13)C isotropic hyperfine constants as an aid to assigning the observed μLCR signals. Computational methods were benchmarked against previously published experimental data for (13)C60Mu in solution. Analysis of the μLCR spectrum resulted in the first experimental determination of (13)C hyperfine constants in either C70Mu or C70H. The large number of values confirms predictions that the four radical isomers have extended distributions of unpaired electron spin.

Hyperfine coupling constants of the nitrogen and phosphorus atoms: A challenge for exact-exchange density-functional and post-Hartree-Fock methods

NASA Astrophysics Data System (ADS)

Kaupp, Martin; Arbuznikov, Alexei V.; Heßelmann, Andreas; Görling, Andreas

2010-05-01

The isotropic hyperfine coupling constants of the free N(S4) and P(S4) atoms have been evaluated with high-level post-Hartree-Fock and density-functional methods. The phosphorus hyperfine coupling presents a significant challenge to both types of methods. With large basis sets, MP2 and coupled-cluster singles and doubles calculations give much too small values for the phosphorus atom. Triple excitations are needed in coupled-cluster calculations to achieve reasonable agreement with experiment. None of the standard density functionals reproduce even the correct sign of this hyperfine coupling. Similarly, the computed hyperfine couplings depend crucially on the self-consistent treatment in exact-exchange density-functional theory within the optimized effective potential (OEP) method. Well-balanced auxiliary and orbital basis sets are needed for basis-expansion exact-exchange-only OEP approaches to come close to Hartree-Fock or numerical OEP data. Results from the localized Hartree-Fock and Krieger-Li-Iafrate approximations deviate notably from exact OEP data in spite of very similar total energies. Of the functionals tested, only full exact-exchange methods augmented by a correlation functional gave at least the correct sign of the P(S4) hyperfine coupling but with too low absolute values. The subtle interplay between the spin-polarization contributions of the different core shells has been analyzed, and the influence of even very small changes in the exchange-correlation potential could be identified.

Fine and hyperfine collisional excitation of C6H by He

NASA Astrophysics Data System (ADS)

Walker, Kyle M.; Lique, François; Dawes, Richard

2018-01-01

Hydrogenated carbon chains have been detected in interstellar and circumstellar media and accurate modelling of their abundances requires collisional excitation rate coefficients with the most abundant species. Among them, the C6H molecule is one of the most abundant towards many lines of sight. Hence, we determined fine and hyperfine-resolved rate coefficients for the excitation of C6H(X2Π) due to collisions with He. We present the first interaction potential energy surface for the C6H-He system, obtained from highly correlated ab initio calculations and characterized by a large anisotropy due to the length of the molecule. We performed dynamical calculations for transitions among the first fine structure levels (up to J = 30.5) of both spin-orbit manifolds of C6H using the close-coupling method, and rate coefficients are determined for temperatures ranging from 5 to 100 K. The largest rate coefficients for even ΔJ transitions conserve parity, while parity-breaking rate coefficients are favoured for odd ΔJ. Spin-orbit changing rate coefficients are several orders of magnitude lower than transitions within a single manifold. State-to-state hyperfine-resolved cross-sections for the first levels (up to J = 13.5) in the Ω = 3/2 spin-orbit manifold are deduced using recoupling techniques. Rate coefficients are obtained and the propensity rule ΔJ = ΔF is seen. These new data will help determine the abundance of C6H in astrophysical environments such as cold dense molecular clouds, star-forming regions and circumstellar envelopes, and will help in the interpretation of the puzzling C6H-/C6H abundance ratios deduced from observations.

Three-dimensional vortex-bright solitons in a spin-orbit-coupled spin-1 condensate

NASA Astrophysics Data System (ADS)

Gautam, Sandeep; Adhikari, S. K.

2018-01-01

We demonstrate stable and metastable vortex-bright solitons in a three-dimensional spin-orbit-coupled three-component hyperfine spin-1 Bose-Einstein condensate (BEC) using numerical solution and variational approximation of a mean-field model. The spin-orbit coupling provides attraction to form vortex-bright solitons in both attractive and repulsive spinor BECs. The ground state of these vortex-bright solitons is axially symmetric for weak polar interaction. For a sufficiently strong ferromagnetic interaction, we observe the emergence of a fully asymmetric vortex-bright soliton as the ground state. We also numerically investigate moving solitons. The present mean-field model is not Galilean invariant, and we use a Galilean-transformed mean-field model for generating the moving solitons.

Spin and charge transport through 1D Moire Crystals

NASA Astrophysics Data System (ADS)

Barraud, Clement; Bonnet, Romeo; Martin, Pascal; Della Rocca, Maria Luisa; Lafarge, Philippe; Laboratoire Matériaux Et Phénomènes Quantiques Team; Laboratoire Itodys Team

Multiwall carbon nanotubes are good candidates for propagating spin information over large distances due to the large mobility of the carriers and to the weak spin-orbit coupling and hyperfine interactions. In this talk, I will present an experimental study concerning charge and spin transport through large diameter multiwall carbon nanotubes presenting intershell interactions leading to superlattice effects (1D Moire). After a description of 1D Moire crystals and to the implication of such superlattices in quantum transport, I will show that spin transport seems to be very efficient close to the new van Hove singularities. Clear magnetoresistance signals of the order of 40 % are reported at low temperatures. We acknowledge financial supports from the Labex SEAM and DIM NANO-K.

Quantum Spin Gyroscope

DTIC Science & Technology

2015-07-15

performing optically detected CW ESR and on-resonance Rabi nutation of the elec- tronic spins (see figure 5). We observed increased homogeneity (as...different crystal axes. Here the magnetic field applied was ∼ 100G. Right: Rabi nutations 2.3 Sensitivity In order to test the performance of this first...resonant driving, which are strongly dependent on the hyperfine interaction. 5 Fig. 6: 14N Rabi oscillations at B = 450G, B1 ≈ 3.3G in the three NV

The g$$p\\atop{2}$$ Experiment: A Measurement of the Proton's Spin Structure Functions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zielinski, Ryan B.

The E08-027 (gmore » $$p\\atop{2}$$) experiment measured the spin structure functions of the proton at Jefferson Laboratory in Newport News, Va. Longitudinally polarized electrons were scattered from a transversely and longitudinally polarized solid ammonia target in Hall A, with the polarized NH$$_3$$ acting as an effective proton target. Focusing on small scattering angle events at the electron energies available at Jefferson Lab, the experiment covered a kinematic phase space of 0.02 GeV$^2$ $< Q^2 <$ 0.20 GeV$^2$ in the proton's resonance region. The spin structure functions, $$g_{1}^p(x,Q^2)$$ and $$g_{2}^p(x,Q^2)$$ , are extracted from an inclusive polarized cross section measurement of the electron-proton interaction. Integrated moments of $$g_1(x,Q^2)$$ are calculated and compared to theoretical predictions made by Chiral Perturbation Theory. The $$g_1(x,Q^2)$$ results are in agreement with previous measurements, but include a significant increase in statistical precision. The spin structure function contributions to the hyperfine energy levels in the hydrogen atom are also investigated. The $$g_2(x,Q^2)$$ measured contribution to the hyperfine splitting is the first ever experimental determination of this quantity. The results of this thesis suggest a disagreement of over 100% with previously published model results.« less

π to σ Radical Tautomerization in One-Electron Oxidized 1-Methylcytosine and its Analogs

PubMed Central

Adhikary, Amitava; Kumar, Anil; Bishop, Casandra T.; Wiegand, Tyler J.; Hindi, Ragda M.; Adhikary, Ananya; Sevilla, Michael D.

2015-01-01

In this work iminyl σ-radical formation in several one-electron oxidized cytosine analogs including 1-MeC, cidofovir, 2′-deoxycytidine (dCyd), and 2′-deoxycytidine 5′-monophosphate (5′-dCMP) were investigated in homogeneous aqueous (D2O or H2O) glassy solutions at low temperatures employing electron spin resonance (ESR) spectroscopy. Employing density functional theory (DFT) (DFT/B3LYP/6-31G* method), the calculated hyperfine coupling constant (HFCC) values of iminyl σ-radical agree quite well with the experimentally observed ones thus confirming its assignment. ESR and DFT studies show that the cytosine-iminyl σ-radical is a tautomer of the deprotonated cytosine π-cation radical (cytosine π-aminyl radical, C(N4-H)•). Employing 1-MeC samples at various pHs ranging ca. 8 to ca. 11, ESR studies show that the tautomeric equilibrium between C(N4-H)• and the iminyl σ-radical at low temperature is too slow to be established without added base. ESR and DFT studies agree that in the iminyl-σ radical, the unpaired spin is localized to the exocyclic nitrogen (N4) in an in-plane pure p-orbital. This gives rise to an anisotropic nitrogen hyperfine coupling (Azz = 40 G) from N4 and a near isotropic β-nitrogen coupling of 9.7 G from the cytosine ring nitrogen at N3. Iminyl σ-radical should exist in its N3-protonated form as the N3-protonated iminyl σ-radical is stabilized in solution by over 30 kcal/mol (ΔG= −32 kcal/mol) over its conjugate base, the N3-deprotonated form. This is the first observation of an isotropic β-hyperfine ring nitrogen coupling in an N-centered DNA-radical. Our theoretical calculations predict that the cytosine iminyl σ-radical can be formed in dsDNA by a radiation-induced ionization–deprotonation process that is only 10 kcal/mol above the lowest energy path. PMID:26237072

Laser Induced Optical Pumping Measurements of Cross Sections for Fine and Hyperfine Structure Transitions in Sodium Induced by Collisions with Helium Argon Atoms

NASA Technical Reports Server (NTRS)

Dobson, Chris C.; Sung, C. C.

1998-01-01

Optical pumping of the ground states of sodium can radically alter the shape of the laser induced fluorescence excitation spectrum, complicating measurements of temperature, pressure, etc., which are based on these spectra. Modeling of the fluorescence using rate equations for the eight hyperfine states of the sodium D manifolds can be used to quantify the contribution to the ground state pumping of transitions among the hyperfine excited states induced by collisions with buffer gas atoms. This model is used here to determine, from the shape of experimental spectra, cross sections for (Delta)F transitions of the P(sub 3/2) state induced by collisions with helium and argon atoms, for a range of values assumed for the P(sub 1/2), (Delta)F cross sections. The hyperfine cross sections measured using this method, which is thought to be novel, are compared with cross sections for transitions involving polarized magnetic substates, m(sub F), measured previously using polarization sensitive absorption. Also, fine structure transition ((Delta)J) cross sections were measured in the pumped vapor, giving agreement with previous measurements made in the absence of pumping.

Laser-Induced Optical Pumping Measurements of Cross Section for Fine- and Hyperfine-Structure Transitions in Sodium Induced by Collisions with Helium and Argon Atoms

NASA Technical Reports Server (NTRS)

Dobson, Chris C.; Sung, C. C.

1999-01-01

Optical pumping of the ground states of sodium can radically alter the shape of the laser-induced fluorescence excitation spectrum, complicating measurements of temperature, pressure, etc., which are based on these spectra. Modeling of the fluorescence using rate equations for the eight hyperfine states of the sodium D manifolds can be used to quantify the contribution to the ground state pumping of transitions among the hyperfine excited states induced by collisions with buffer gas atoms. This model is used here to determine, from the shape of experimental spectra, cross sections lor DELTA.F transitions of the P(sub 3/2) state induced by collisions with helium and argon atoms, for a range of values assumed for the P(sub 1/2), DELTA.F cross sections. The hyperfine cross sections measured using this method, which to our knowledge is novel, are compared with cross sections for transitions involving polarized magnetic substates m(sub F) measured previously using polarization sensitive absorption. Also, fine-structure transition cross sections were measured in the pumped vapor, giving agreement with previous measurements made in the absence of pumping.

Fourier transform millimeter-wave spectroscopy of the ethyl radical in the electronic ground state.

PubMed

Kim, Eunsook; Yamamoto, Satoshi

2004-02-15

The pure rotational spectrum of the ethyl radical (C2H5) has been detected for the first time with the Fourier transform millimeter-wave spectrometer. The ethyl radical is produced by discharging the C2H5I gas diluted in Ar. The 1(01)-0(00) rotational transition of the ethyl radical is observed in the frequency range from 43,680 to 43,780 MHz. The observed spectrum shows a very complicated pattern of the fine and hyperfine structures of a doublet radical with the nuclear spins of five protons. The fine and hyperfine components are assigned with the aid of measurements of the Zeeman splittings. As a result, the 22 lines are ascribed to the transitions in the ground vibronic state (A2"). The rotational constant, the spin-rotation interaction constant, and hyperfine interaction constants are determined by the least-squares fit. The Fermi contact term of the alpha-proton is determined to be -64.1654 MHz in the gas phase, indicating that the structure of the -CH2 is essentially planar. The present rotational spectroscopic study further supports that the methyl group of the ethyl radical can be regarded as a nearly free internal rotor with a low energy barrier. A few unassigned lines still remain, which may be vibrational satellites of the internal rotation mode. Copyright 2004 American Institute of Physics

Magnetoelectroluminescence of organic heterostructures: Analytical theory and spectrally resolved measurements

NASA Astrophysics Data System (ADS)

Liu, Feilong; Kelley, Megan R.; Crooker, Scott A.; Nie, Wanyi; Mohite, Aditya D.; Ruden, P. Paul; Smith, Darryl L.

2014-12-01

The effect of a magnetic field on the electroluminescence of organic light emitting devices originates from the hyperfine interaction between the electron/hole polarons and the hydrogen nuclei of the host molecules. In this paper, we present an analytical theory of magnetoelectroluminescence for organic semiconductors. To be specific, we focus on bilayer heterostructure devices. In the case we are considering, light generation at the interface of the donor and acceptor layers results from the formation and recombination of exciplexes. The spin physics is described by a stochastic Liouville equation for the electron/hole spin density matrix. By finding the steady-state analytical solution using Bloch-Wangsness-Redfield theory, we explore how the singlet/triplet exciplex ratio is affected by the hyperfine interaction strength and by the external magnetic field. To validate the theory, spectrally resolved electroluminescence experiments on BPhen/m-MTDATA devices are analyzed. With increasing emission wavelength, the width of the magnetic field modulation curve of the electroluminescence increases while its depth decreases. These observations are consistent with the model.

SU(6), triquark states, and the pentaquark

NASA Astrophysics Data System (ADS)

Majee, Swarup Kumar; Raychaudhuri, Amitava

2008-04-01

The purported observation of a state Θ+ with strangeness S=+1 led to its quark model interpretation in terms of a pentaquark combination involving a triquark-diquark structure—the Karliner-Lipkin model. In this work, the proper color-spin symmetry properties for the qq qmacr triquark are elucidated by calculating the SU(6) unitary scalar factors and Racah coefficients. Using these results, the color-spin hyperfine interactions, including flavor symmetry breaking therein, become straightforward to incorporate and the pentaquark masses are readily obtained. We examine the effect on the pentaquark mass of (a) deviations from the flavor symmetric limit and (b) different strengths of the doublet and triplet hyperfine interactions. Reference values of these parameters yield a Θ+ mass prediction of 1601 MeV but it can comfortably accommodate 1540 MeV for alternate choices. In the same framework, other pentaquark states Ξ(S=-2) and Θc (with charm C=-1) are expected at 1783 MeV and 2757 MeV, respectively.

Fluctuation in the Intermediate Magnetic Phase of Triangular Ising Antiferromagnet (CeS)1.16[Fe0.33(NbS2)2

NASA Astrophysics Data System (ADS)

Michioka, Chishiro; Suzuki, Kazuya; Mibu, Ko

2002-10-01

We applied 57Fe Mössbauer spectroscopy for investigating the Ising spin triangular lattice antiferromagnet (TLA) (CeS)1.16[Fe0.33(NbS2)2] between 2 and 300 K. The spectra revealed that the relaxation time of the hyperfine field markedly changes in the intermediate phase between TN1=22 K and TN2=15 K due to strong spin fluctuation. The relaxation of the hyperfine field is not sufficiently fast as a paramagnet even at 77 K, which is much higher than TN1, and the inverse susceptibility of (LaS)1.14[Fe0.33(NbS2)2] deviates from the Curie-Weiss law below 100 K. These results indicate that an unusual short-range order exists above TN1. The temperature dependence of the Mössbauer spectra can be explained by phase transition of the three-dimensional TLA model with weak interlayer exchange interactions.

Hyperfine interaction in K 2Ba[Fe(NO 2) 6

NASA Astrophysics Data System (ADS)

Padmakumar, K.; Manoharan, P. T.

2000-04-01

Magnetic hyperfine splitting observed in the low temperature Mössbauer spectrum of potassium barium hexanitro ferrate(II), in the absence of any external field, is attributed to the 5T 2g state of the central metal atom further split into a ground 5E g state and a first excited 5B 2g state under a distorted octahedral symmetry in contrast to the earlier prediction of 1A 1g ground state on the basis of room temperature Mössbauer spectral and other properties. The central iron atom is co-ordianted to six nitrito groups (NO 2-), having an oxidation state of +2. The temperature dependence of Mössbauer spectra is explained on the basis of electronic relaxation among the spin-orbit coupled levels of the 5E g ground state. Various kinds of electronic relaxation mechanisms have been compared to explain the proposed mechanism. The observed temperature dependent spectra with varying internal magnetic field and line width can be explained by simple spin lattice relaxation.

Calculation of spin-densities within the context of density functional theory. The crucial role of the correlation functional

NASA Astrophysics Data System (ADS)

Filatov, Michael; Cremer, Dieter

2005-09-01

It is demonstrated that the LYP correlation functional is not suited to be used for the calculation of electron spin resonance hyperfine structure (HFS) constants, nuclear magnetic resonance spin-spin coupling constants, magnetic, shieldings and other properties that require a balanced account of opposite- and equal-spin correlation, especially in the core region. In the case of the HFS constants of alkali atoms, LYP exaggerates opposite-spin correlation effects thus invoking too strong in-out correlation effects, an exaggerated spin-polarization pattern in the core shells of the atoms, and, consequently, too large HFS constants. Any correlation functional that provides a balanced account of opposite- and equal-spin correlation leads to improved HFS constants, which is proven by comparing results obtained with the LYP and the PW91 correlation functional. It is suggested that specific response properties are calculated with the PW91 rather than the LYP correlation functional.

HYPERFINE STRUCTURES AND NUCLEAR MOMENTS OF Lu$sup 176$m, Br$sup 80$, Br$sup 80$m, AND I$sup 132$ (thesis)

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, M.B.

1962-09-01

The method of atomic-beam radiofrequency spectroscopy was used to determine some nuclear and atomic properties of Lu/sup 176m/, Br/sup 80/, Br/sup 80m/, and I/sup 132/. Hyperfine structure me asurements were raade to determine the magnetic dipole interaction constants and the electric quadrupole interaction constants of all these isotopes. Also the nuclear spin and the electronic g/sub J/ factor were measured for Lu/sup 176m/, and the nuclear magnetic dipole moments and the electric quadrupole moments for the isotopes were calculated. All results are listed. 62 references. (auth)

Hartree-Fock investigation of muon trapping in the chemical ferromagnet 4-(/p-chlorobenzylideneamino)-TEMPO

NASA Astrophysics Data System (ADS)

Jeong, Junho; Briere, Tina M.; Sahoo, N.; Das, T. P.; Ohira, Seiko; Nishiyama, K.; Nagamine, K.

2000-08-01

First-principles unrestricted Hartree-Fock theory is used to obtain the trapping sites for muon and muonium in ferromagnetic p-Cl-Ph-CHN-TEMPO (4-( p-chlorobenzylideneamino)- 2,2,6,6-tetramethylpiperidin-1-yloxyl) and the hyperfine interaction tensors for these sites. Using the calculated hyperfine interactions to fit the two experimentally observed muon spin rotation frequencies, it has been concluded that the two most likely candidates for explaining the experimental data are a muon trapped at the chlorine site and a singlet muonium state at the radical oxygen. The direction of the easy axis is also determined.

Determination of hyperfine-induced transition rates from observations of a planetary nebula.

PubMed

Brage, Tomas; Judge, Philip G; Proffitt, Charles R

2002-12-31

Observations of the planetary nebula NGC3918 made with the STIS instrument on the Hubble Space Telescope reveal the first unambiguous detection of a hyperfine-induced transition 2s2p 3P(o)(0)-->2s2 1S0 in the berylliumlike emission line spectrum of N IV at 1487.89 A. A nebular model allows us to confirm a transition rate of 4x10(-4) sec(-1)+/-33% for this line. The measurement represents the first independent confirmation of the transition rate of hyperfine-induced lines in low ionization stages, and it provides support for the techniques used to compute these transitions for the determination of very low densities and isotope ratios.

Solid-state EPR strategies for the structural characterization of paramagnetic NO adducts of frustrated Lewis pairs (FLPs)

NASA Astrophysics Data System (ADS)

de Oliveira, Marcos; Wiegand, Thomas; Elmer, Lisa-Maria; Sajid, Muhammad; Kehr, Gerald; Erker, Gerhard; Magon, Claudio José; Eckert, Hellmut

2015-03-01

Anisotropic interactions present in three new nitroxide radicals prepared by N,N addition of NO to various borane-phosphane frustrated Lewis pairs (FLPs) have been characterized by continuous-wave (cw) and pulsed X-band EPR spectroscopies in solid FLP-hydroxylamine matrices at 100 K. Anisotropic g-tensor values and 11B, 14N, and 31P hyperfine coupling tensor components have been extracted from continuous-wave lineshape analyses, electron spin echo envelope modulation (ESEEM), and hyperfine sublevel correlation spectroscopy (HYSCORE) experiments with the help of computer simulation techniques. Suitable fitting constraints are developed on the basis of density functional theory (DFT) calculations. These calculations reveal that different from the situation in standard nitroxide radicals (TEMPO), the g-tensors are non-coincident with any of the nuclear hyperfine interaction tensors. The determination of these interaction parameters turns out to be successful, as the cw- and pulse EPR experiments are highly complementary in informational content. While the continuous-wave lineshape is largely influenced by the anisotropic hyperfine coupling to 14N and 31P, the ESEEM and HYSCORE spectra contain important information about the 11B hyperfine coupling and nuclear electric quadrupolar interaction. The set of cw- and pulsed EPR experiments, with fitting constraints developed by DFT calculations, defines an efficient strategy for the structural analysis of paramagnetic FLP adducts.

Solid-state EPR strategies for the structural characterization of paramagnetic NO adducts of frustrated Lewis pairs (FLPs)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oliveira, Marcos de; Magon, Claudio José; Wiegand, Thomas

2015-03-28

Anisotropic interactions present in three new nitroxide radicals prepared by N,N addition of NO to various borane-phosphane frustrated Lewis pairs (FLPs) have been characterized by continuous-wave (cw) and pulsed X-band EPR spectroscopies in solid FLP-hydroxylamine matrices at 100 K. Anisotropic g-tensor values and {sup 11}B, {sup 14}N, and {sup 31}P hyperfine coupling tensor components have been extracted from continuous-wave lineshape analyses, electron spin echo envelope modulation (ESEEM), and hyperfine sublevel correlation spectroscopy (HYSCORE) experiments with the help of computer simulation techniques. Suitable fitting constraints are developed on the basis of density functional theory (DFT) calculations. These calculations reveal that differentmore » from the situation in standard nitroxide radicals (TEMPO), the g-tensors are non-coincident with any of the nuclear hyperfine interaction tensors. The determination of these interaction parameters turns out to be successful, as the cw- and pulse EPR experiments are highly complementary in informational content. While the continuous-wave lineshape is largely influenced by the anisotropic hyperfine coupling to {sup 14}N and {sup 31}P, the ESEEM and HYSCORE spectra contain important information about the {sup 11}B hyperfine coupling and nuclear electric quadrupolar interaction. The set of cw- and pulsed EPR experiments, with fitting constraints developed by DFT calculations, defines an efficient strategy for the structural analysis of paramagnetic FLP adducts.« less

Electron spin resonance of (CO 2 H)CH 2 CH 2 CH(CO 2 H) in irradiated glutaric acid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Horsfield, A.; Morton, J. R.; Whiffen, D. H.

It is concluded from electron spin resonance spectra that the radical (CO 2 H)CH 2 CH 2 CH(CO 2 H) remains trapped in a glutaric acid crystal after gamma -irradiation. This radical is found in two different conformations. Approximate hyperfine coupling constants are given for each, although exact interpretation is hindered by the overlapping of spectra. Reasons for the formation of the two forms of the radical are discussed.

Storage rings for spin-polarized hydrogen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thompson, D.; Lovelace, R.V.E.; Lee, D.

1989-11-01

A strong-focusing storage ring is proposed for the long-term magnetic confinement of a collisional gas of neutral spin-polarized hydrogen atoms in the Za{l arrow} and Zb{l arrow} hyperfine states. The trap uses the interaction of the magnetic moments of the gas atoms with a static magnetic field. Laser cooling and evaporative cooling can be utilized to enhance the confinement and to offset the influence of viscous heating. An important application of the trap is to the attainment of Bose--Einstein condensation.

The Submillimeter Spectrum of MnH and MnD (X7Σ+)

NASA Astrophysics Data System (ADS)

Halfen, D. T.; Ziurys, L. M.

2008-01-01

The submillimeter-wave spectrum of the MnH and MnD radicals in their 7Σ+ ground states has been measured in the laboratory using direct absorption techniques. These species were created in the gas phase by the reaction of manganese vapor, produced in a Broida-type oven, with either H2 or D2 gas in the presence of a DC discharge. The N = 0 → 1 transition of MnH near 339 GHz was recorded, which consisted of multiple hyperfine components arising from both the manganese and hydrogen nuclear spins. The N = 2 → 3 transition of MnD near 517 GHz was measured as well, but in this case only the manganese hyperfine interactions were resolved. Both data sets were analyzed with a Hund's case b Hamiltonian, and rotational, fine structure, magnetic hyperfine, and electric quadrupole constants have been determined for the two manganese species. An examination of the magnetic hyperfine constants shows that MnH is primarily an ionic species, but has more covalent character than MnF. MnH is a good candidate species for astronomical searches with Herschel, particularly toward material associated with luminous blue variable stars.

Structure and nature of manganese(II) imidazole complexes in frozen aqueous solutions.

PubMed

Un, Sun

2013-04-01

A common feature of a large majority of the manganese metalloenzymes, as well as many synthetic biomimetic complexes, is the bonding between the manganese ion and imidazoles. This interaction was studied by examining the nature and structure of manganese(II) imidazole complexes in frozen aqueous solutions using 285 GHz high magnet-field continuous-wave electron paramagnetic resonance (cw-HFEPR) and 95 GHz pulsed electron-nuclear double resonance (ENDOR) and pulsed electron-double resonance detected nuclear magnetic resonance (PELDOR-NMR). The (55)Mn hyperfine coupling and isotropic g values of Mn(II) in frozen imidazole solutions continuously decreased with increasing imidazole concentration. ENDOR and PELDOR-NMR measurements demonstrated that the structural basis for this behavior arose from the imidazole concentration-dependent distribution of three six-coordinate and two four-coordinate species: [Mn(H2O)6](2+), [Mn(imidazole)(H2O)5](2+), [Mn(imidazole)2(H2O)4](2+), [Mn(imidazole)3(H2O)](2+), and [Mn(imidazole)4](2+). The hyperfine and g values of manganese proteins were also fully consistent with this imidazole effect. Density functional theory methods were used to calculate the structures, spin and charge densities, and hyperfine couplings of a number of different manganese imidazole complexes. The use of density functional theory with large exact-exchange admixture calculations gave isotropic (55)Mn hyperfine couplings that were semiquantitative and of predictive value. The results show that the covalency of the Mn-N bonds play an important role in determining not only magnetic spin parameters but also the structure of the metal binding site. The relationship between the isotropic (55)Mn hyperfine value and the number of imidazole ligands provides a quick and easy test for determining whether a protein binds an Mn(II) ion using histidine residues and, if so, how many are involved. Application of this method shows that as much as 40% of the Mn(II) ions in Deinococcus radiodurans are ligated to two histidines (Tabares, L. C.; Un, S. J. Biol. Chem 2013, in press).

Simple and Accurate Method for Central Spin Problems

NASA Astrophysics Data System (ADS)

Lindoy, Lachlan P.; Manolopoulos, David E.

2018-06-01

We describe a simple quantum mechanical method that can be used to obtain accurate numerical results over long timescales for the spin correlation tensor of an electron spin that is hyperfine coupled to a large number of nuclear spins. This method does not suffer from the statistical errors that accompany a Monte Carlo sampling of the exact eigenstates of the central spin Hamiltonian obtained from the algebraic Bethe ansatz, or from the growth of the truncation error with time in the time-dependent density matrix renormalization group (TDMRG) approach. As a result, it can be applied to larger central spin problems than the algebraic Bethe ansatz, and for longer times than the TDMRG algorithm. It is therefore an ideal method to use to solve central spin problems, and we expect that it will also prove useful for a variety of related problems that arise in a number of different research fields.

Spin-orbit signatures in the dynamics of singlet-triplet qubits in double quantum dots

NASA Astrophysics Data System (ADS)

Rolon, Juan E.; Cota, Ernesto; Ulloa, Sergio E.

2017-05-01

We characterize numerically and analytically the signatures of the spin-orbit interaction in a two-electron GaAs double quantum dot in the presence of an external magnetic field. In particular, we obtain the return probability of the singlet state by simulating Landau-Zener voltage detuning sweeps which traverse the singlet-triplet (S -T+ ) resonance. Our results indicate that non-spin-conserving interdot tunneling processes arising from the spin-orbit interaction have well defined signatures. These allow direct access to the spin-orbit interaction scales and are characterized by a frequency shift and Fourier amplitude modulation of the Rabi flopping dynamics of the singlet-triplet qubits S -T0 and S -T+ . By applying the Bloch-Feshbach projection formalism, we demonstrate analytically that the aforementioned effects originate from the interplay between spin-orbit interaction and processes driven by the hyperfine interaction between the electron spins and those of the GaAs nuclei.

La 139 NMR investigation of the charge and spin order in a La 1.885 Sr 0.115 CuO 4 single crystal

DOE PAGES

Arsenault, A.; Takahashi, S. K.; Imai, T.; ...

2018-02-14

139La NMR is suited for investigations into magnetic properties of La 2CuO 4 -based cuprates in the vicinity of their magnetic instabilities, owing to the modest hyperfine interactions between 139La nuclear spins and Cu electron spins. We report comprehensive 139La NMR measurements on a single-crystal sample of high-T c superconductor La 1.885 Sr 0.115 CuO 4 in a broad temperature range across the charge and spin order transitions (T charge ≃ 80 K, T neutron spin ≃ T c = 30 K). From the high-precision measurements of the linewidth for the nuclear spin I z = + 1 / 2 to -1/2 central transition, we show that paramagnetic line broadening sets in precisely at T charge due to enhanced spin correlations within the CuO 2 planes. Additional paramagnetic line broadening ensues below ~35 K, signaling that Cu spins in some segments of CuO 2 planes are on the verge of three-dimensional magnetic order. A static hyperfine magnetic field arising from ordered Cu moments along the ab plane, however, begins to develop only below Tmore » $$μSR\\atop{spin}$$ = 15 – 20 K, where earlier muon spin rotation measurements detected Larmor precession for a small volume fraction (~20 % ) of the sample. Based on the measurement of 139 La nuclear-spin-lattice relaxation rate 1/T 1, we also show that charge order triggers enhancement of low-frequency Cu spin fluctuations inhomogeneously; a growing fraction of 139 La sites is affected by enhanced low-frequency spin fluctuations toward the eventual magnetic order, whereas a diminishing fraction continues to exhibit a behavior analogous to the optimally superconducting phase even below T charge. In conclusion, these 139La NMR results corroborate our recent 63Cu NMR observation that a very broad, anomalous winglike signal gradually emerges below T charge, whereas the normally behaving, narrower main peak is gradually wiped out [T. Imai et al., Phys. Rev. B 96, 224508 (2017)]. Furthermore, we show that the enhancement of low-energy spin excitations in the low-temperature regime below Tneutron spin (≃ Tc) depends strongly on the magnitude and orientation of the applied magnetic field.« less

La 139 NMR investigation of the charge and spin order in a La 1.885 Sr 0.115 CuO 4 single crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arsenault, A.; Takahashi, S. K.; Imai, T.

139La NMR is suited for investigations into magnetic properties of La 2CuO 4 -based cuprates in the vicinity of their magnetic instabilities, owing to the modest hyperfine interactions between 139La nuclear spins and Cu electron spins. We report comprehensive 139La NMR measurements on a single-crystal sample of high-T c superconductor La 1.885 Sr 0.115 CuO 4 in a broad temperature range across the charge and spin order transitions (T charge ≃ 80 K, T neutron spin ≃ T c = 30 K). From the high-precision measurements of the linewidth for the nuclear spin I z = + 1 / 2 to -1/2 central transition, we show that paramagnetic line broadening sets in precisely at T charge due to enhanced spin correlations within the CuO 2 planes. Additional paramagnetic line broadening ensues below ~35 K, signaling that Cu spins in some segments of CuO 2 planes are on the verge of three-dimensional magnetic order. A static hyperfine magnetic field arising from ordered Cu moments along the ab plane, however, begins to develop only below Tmore » $$μSR\\atop{spin}$$ = 15 – 20 K, where earlier muon spin rotation measurements detected Larmor precession for a small volume fraction (~20 % ) of the sample. Based on the measurement of 139 La nuclear-spin-lattice relaxation rate 1/T 1, we also show that charge order triggers enhancement of low-frequency Cu spin fluctuations inhomogeneously; a growing fraction of 139 La sites is affected by enhanced low-frequency spin fluctuations toward the eventual magnetic order, whereas a diminishing fraction continues to exhibit a behavior analogous to the optimally superconducting phase even below T charge. In conclusion, these 139La NMR results corroborate our recent 63Cu NMR observation that a very broad, anomalous winglike signal gradually emerges below T charge, whereas the normally behaving, narrower main peak is gradually wiped out [T. Imai et al., Phys. Rev. B 96, 224508 (2017)]. Furthermore, we show that the enhancement of low-energy spin excitations in the low-temperature regime below Tneutron spin (≃ Tc) depends strongly on the magnitude and orientation of the applied magnetic field.« less

Hyperfine structure of the hydroxyl free radical (OH) in electric and magnetic fields

NASA Astrophysics Data System (ADS)

Maeda, Kenji; Wall, Michael L.; Carr, Lincoln D.

2015-05-01

We investigate single-particle energy spectra of the hydroxyl free radical (OH) in the lowest electronic and rovibrational level under combined static electric and magnetic fields, as an example of heteronuclear polar diatomic molecules. In addition to the fine-structure interactions, the hyperfine interactions and centrifugal distortion effects are taken into account to yield the zero-field spectrum of the lowest 2Π3 / 2 manifold to an accuracy of less than 2kHz. We also examine level crossings and repulsions in the hyperfine structure induced by applied electric and magnetic fields. Compared to previous work, we found more than 10 percent reduction of the magnetic fields at level repulsions in the Zeeman spectrum subjected to a perpendicular electric field. In addition, we find new level repulsions, which we call Stark-induced hyperfine level repulsions, that require both an electric field and hyperfine structure. It is important to take into account hyperfine structure when we investigate physics of OH molecules at micro-Kelvin temperatures and below. This research was supported in part by AFOSR Grant No.FA9550-11-1-0224 and by the NSF under Grants PHY-1207881 and NSF PHY-1125915. We appreciate the Aspen Center for Physics, supported in part by the NSF Grant No.1066293, for hospitality.

Orbitally excited spectra and decay of cc¯ meson

NASA Astrophysics Data System (ADS)

Chaturvedi, Raghav; Rai, A. K.

2018-05-01

We use the hydrogen like trial wave function for computation of the mass spectra and decay properties of charmonia within the framework of phenomenological quark anti-quark Coulomb plus power potential with varying potential index from 0.5 to 2.0. The spin-spin hyperfine interaction is considered to incorporate splitting of the ground and radially excited states energy levels, further spin-orbit and tensor interactions are employed to calculate the masses of orbitally excited states. We construct the Regge trajectories from the mass spectra in (J, M2) and (nr, M2) planes. We also compute γγ decay width of P wave states of cc¯.

53Cr NMR study of CuCrO2 multiferroic

NASA Astrophysics Data System (ADS)

Smol'nikov, A. G.; Ogloblichev, V. V.; Verkhovskii, S. V.; Mikhalev, K. N.; Yakubovskii, A. Yu.; Kumagai, K.; Furukawa, Y.; Sadykov, A. F.; Piskunov, Yu. V.; Gerashchenko, A. P.; Barilo, S. N.; Shiryaev, S. V.

2015-11-01

The magnetically ordered phase of the CuCrO2 single crystal has been studied by the nuclear magnetic resonance (NMR) method on 53Cr nuclei in the absence of an external magnetic field. The 53Cr NMR spectrum is observed in the frequency range νres = 61-66 MHz. The shape of the spectrum depends on the delay tdel between pulses in the pulse sequence τπ/2- t del-τπ- t del-echo. The spin-spin and spin-lattice relaxation times have been measured. Components of the electric field gradient, hyperfine fields, and the magnetic moment on chromium atoms have been estimated.

Theoretical explanation of spin-Hamiltonian parameters and local structure for the orthorhombic MnO2 -4 clusters in K2CrO4 : Mn6 + crystal

NASA Astrophysics Data System (ADS)

Wang, Ning; Xie, Linhua

2017-12-01

In this paper, the spin-Hamiltonian parameters (g factors gx, gy, gz and hyperfine structure constants A Ax, Ay, Az) and the absorption spectrum of K2CrO4 : Mn6 + crystal are theoretically explained by using the high-order perturbation theory, the double-spin-orbit-coupling model theory and the double-mechanism theory (the crystal field mechanism and the charge-transfer (CT) mechanism). The calculation results show that the contribution of the CT mechanism cannot be neglected for Mn6 + ions in orthorhombic clusters with the ground state ?.

Electrical Control of g-Factor in a Few-Hole Silicon Nanowire MOSFET.

PubMed

Voisin, B; Maurand, R; Barraud, S; Vinet, M; Jehl, X; Sanquer, M; Renard, J; De Franceschi, S

2016-01-13

Hole spins in silicon represent a promising yet barely explored direction for solid-state quantum computation, possibly combining long spin coherence, resulting from a reduced hyperfine interaction, and fast electrically driven qubit manipulation. Here we show that a silicon-nanowire field-effect transistor based on state-of-the-art silicon-on-insulator technology can be operated as a few-hole quantum dot. A detailed magnetotransport study of the first accessible hole reveals a g-factor with unexpectedly strong anisotropy and gate dependence. We infer that these two characteristics could enable an electrically driven g-tensor-modulation spin resonance with Rabi frequencies exceeding several hundred mega-Hertz.

Persistent Optical Nuclear Spin Narrowing in a Singly Charged InAs Quantum Dot

DTIC Science & Technology

2012-02-01

explained in terms of an anisotropic hyperfine coupling between the hole spin and the nuclear spins. © 2012 Optical Society of America OCIS codes: 300.6250...February 2012 / J. Opt. Soc. Am. B A121 where γs (γt) is the spin (trion) dephasing rate, χ is half the pump Rabi frequency ΩR (ΩR # μEℏ , where μ is...probe ab- sorption at the dark state dip (αdip) and the Rabi sideband (αpeak): αdip # α0 χ2γs & γt$γ2s% χ4 & 2χ2γtγs & γ2t γ2s ; (11) αpeak # α0 χ2γs

Microwave ac Zeeman force for ultracold atoms

NASA Astrophysics Data System (ADS)

Fancher, C. T.; Pyle, A. J.; Rotunno, A. P.; Aubin, S.

2018-04-01

We measure the ac Zeeman force on an ultracold gas of 87Rb due to a microwave magnetic field targeted to the 6.8 GHz hyperfine splitting of these atoms. An atom chip produces a microwave near field with a strong amplitude gradient, and we observe a force over three times the strength of gravity. Our measurements are consistent with a simple two-level theory for the ac Zeeman effect and demonstrate its resonant, bipolar, and spin-dependent nature. We observe that the dressed-atom eigenstates gradually mix over time and have mapped out this behavior as a function of magnetic field and detuning. We demonstrate the practical spin selectivity of the force by pushing or pulling a specific spin state while leaving other spin states unmoved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solomatova, Natalia V.; Jackson, Jennifer M.; Sturhahn, Wolfgang

The physical properties of silicate melts within Earth's mantle affect the chemical and thermal evolution of its interior. Chemistry and coordination environments affect such properties. We have measured the hyperfine parameters of iron-bearing rhyolitic and basaltic glasses up to ~120 GPa and ~100 GPa, respectively, in a neon pressure medium using time domain synchrotron Mössbauer spectroscopy. The spectra for rhyolitic and basaltic glasses are well explained by three high-spin Fe2+-like sites with distinct quadrupole splittings. Absence of detectable ferric iron was confirmed with optical absorption spectroscopy. The sites with relatively high and intermediate quadrupole splittings are likely a result ofmore » fivefold and sixfold coordination environments of ferrous iron that transition to higher coordination with increasing pressure. The ferrous site with a relatively low quadrupole splitting and isomer shift at low pressures may be related to a fourfold or a second fivefold ferrous iron site, which transitions to higher coordination in basaltic glass, but likely remains in low coordination in rhyolitic glass. These results indicate that iron experiences changes in its coordination environment with increasing pressure without undergoing a high-spin to low-spin transition. We compare our results to the hyperfine parameters of silicate glasses of different compositions. With the assumption that coordination environments in silicate glasses may serve as a good indicator for those in a melt, this study suggests that ferrous iron in chemically complex silicate melts likely exists in a high-spin state throughout most of Earth's mantle.« less

Effect of Charge Localization on the Effective Hyperfine Interaction in Organic Semiconducting Polymers

NASA Astrophysics Data System (ADS)

Geng, Rugang; Subedi, Ram C.; Luong, Hoang M.; Pham, Minh T.; Huang, Weichuan; Li, Xiaoguang; Hong, Kunlun; Shao, Ming; Xiao, Kai; Hornak, Lawrence A.; Nguyen, Tho D.

2018-02-01

Hyperfine interaction (HFI), originating from the coupling between spins of charge carriers and nuclei, has been demonstrated to strongly influence the spin dynamics of localized charges in organic semiconductors. Nevertheless, the role of charge localization on the HFI strength in organic thin films has not yet been experimentally investigated. In this study, the statistical relation hypothesis that the effective HFI of holes in regioregular poly(3-hexylthiophene) (P3HT) is proportional to 1 /N0.5 has been examined, where N is the number of the random nuclear spins within the envelope of the hole wave function. First, by studying magnetoconductance in hole-only devices made by isotope-labeled P3HT we verify that HFI is indeed the dominant spin interaction in P3HT. Second, assuming that holes delocalize fully over the P3HT polycrystalline domain, the strength of HFI is experimentally demonstrated to be proportional to 1 /N0.52 in excellent agreement with the statistical relation. Third, the HFI of electrons in P3HT is about 3 times stronger than that of holes due to the stronger localization of the electrons. Finally, the effective HFI in organic light emitting diodes is found to be a superposition of effective electron and hole HFI. Such a statistical relation may be generally applied to other semiconducting polymers. This Letter may provide great benefits for organic optoelectronics, chemical reaction kinetics, and magnetoreception in biology.

Effect of Charge Localization on the Effective Hyperfine Interaction in Organic Semiconducting Polymers.

PubMed

Geng, Rugang; Subedi, Ram C; Luong, Hoang M; Pham, Minh T; Huang, Weichuan; Li, Xiaoguang; Hong, Kunlun; Shao, Ming; Xiao, Kai; Hornak, Lawrence A; Nguyen, Tho D

2018-02-23

Hyperfine interaction (HFI), originating from the coupling between spins of charge carriers and nuclei, has been demonstrated to strongly influence the spin dynamics of localized charges in organic semiconductors. Nevertheless, the role of charge localization on the HFI strength in organic thin films has not yet been experimentally investigated. In this study, the statistical relation hypothesis that the effective HFI of holes in regioregular poly(3-hexylthiophene) (P3HT) is proportional to 1/N^{0.5} has been examined, where N is the number of the random nuclear spins within the envelope of the hole wave function. First, by studying magnetoconductance in hole-only devices made by isotope-labeled P3HT we verify that HFI is indeed the dominant spin interaction in P3HT. Second, assuming that holes delocalize fully over the P3HT polycrystalline domain, the strength of HFI is experimentally demonstrated to be proportional to 1/N^{0.52} in excellent agreement with the statistical relation. Third, the HFI of electrons in P3HT is about 3 times stronger than that of holes due to the stronger localization of the electrons. Finally, the effective HFI in organic light emitting diodes is found to be a superposition of effective electron and hole HFI. Such a statistical relation may be generally applied to other semiconducting polymers. This Letter may provide great benefits for organic optoelectronics, chemical reaction kinetics, and magnetoreception in biology.

Low temperature EPR investigation of Co2+ ion doped into rutile TiO2 single crystal: Experiments and simulations

NASA Astrophysics Data System (ADS)

Zerentürk, A.; Açıkgöz, M.; Kazan, S.; Yıldız, F.; Aktaş, B.

2017-02-01

In this paper, we present the results of X-band EPR spectra of Co2+ ion doped rutile (TiO2) which is one of the most promising memristor material. We obtained the angular variation of spectra in three mutually perpendicular planes at liquid helium (7-13 K) temperatures. Since the impurity ions have ½ effective spin and 7/2 nuclear spin, a relatively simple spin Hamiltonian containing only electronic Zeeman and hyperfine terms was utilized. Two different methods were used in theoretical analysis. Firstly, a linear regression analysis of spectra based on perturbation theory was studied. However, this approach is not sufficient for analyzing Co+2 spectra and leads to complex eigenvectors for G and A tensors due to large anisotropy of eigenvalues. Therefore, all spectra were analyzed again with exact diagonalization of spin Hamiltonian and the high accuracy eigenvalues and eigenvectors of G and A tensors were obtained by taking into account the effect of small sample misalignment from the exact crystallographic planes due to experimental conditions. Our results show that eigen-axes of g and A tensors are parallel to crystallographic directions. Hence, our EPR experiments proves that Co2+ ions substitute for Ti4+ ions in lattice. The obtained principal values of g tensor are gx=2.110(6), gy=5.890(2), gz=3.725(7) and principal values of hyperfine tensor are Ax=42.4, Ay=152.7, Az=26 (in 10-4/cm).

Theoretical study of the hyperfine parameters of OH

NASA Technical Reports Server (NTRS)

Chong, Delano P.; Langhoff, Stephen R.; Bauschlicher, Charles W., Jr.

1991-01-01

In the present study of the hyperfine parameters of O-17H as a function of the one- and n-particle spaces, all of the parameters except oxygen's spin density, b sub F(O), are sufficiently easily tractable to allow concentration on the computational requirements for accurate determination of b sub F(O). Full configuration-interaction (FCI) calculations in six Gaussian basis sets yield unambiguous results for (1) the effect of uncontracting the O s and p basis sets; (2) that of adding diffuse s and p functions; and (3) that of adding polarization functions to O. The size-extensive modified coupled-pair functional method yields b sub F values which are in fair agreement with FCI results.

Hyperfine Induced Transitions as Diagnostics of Low Density Plasmas and Isotopic Abundance ratios.

NASA Astrophysics Data System (ADS)

Brage, T.; Judge, P. G.; Aboussaid, A.; Godefroid, M. R.; Jonsson, P.; Leckrone, D. S.

1996-05-01

We propose a new diagnostics of isotope abundance ratios and electron densities for low density plasmas, in the form of J = 0 -> J(') = 0 radiative transitions. These are usually viewed as being allowed only through two-photon decay, but they may also be induced by the hyperfine (HPF) interaction in atomic ions. This predicts a companion line to the E1] and M2 lines in the UV0.01 multiplet of ions isoelectronic to beryllium (e.g. C III, N IV, O V and Fe XXII) or magnesium (e.g. Si II, Ca IX, Fe XV and Ni XVII). As an example the companion line to the well known lambda lambda 1906.7,1908.7 lines in C III will be at 1909.597 Angstroms, but only present in the (13) C isotope (which has nuclear spin different from zero). We present new and accurate decay rates for the nsnp (3P^oJ) -> ns(2) (1S_{J('}=0)) transitions in ions of the Be (n=2) and Mg (n=3) isoelectronic sequences. We show that the HPF induced decay rates for the J = 0 -> J(') = 0 transitions are many orders of magnitude larger than those for the competing two-photon processes and, when present, are typically one or two orders of magnitude smaller than the decay rates of the magnetic quadrupole ( J = 2-> J(') = 0) transitions for these ions. We show that several of these HPF-induced transitions are of potential astrophysical interest, in ions of C, N, Na, Mg, Al, Si, K, Cr, Fe and Ni. We highlight those cases that may be of particular diagnostic value for determining isotopic abundance ratios and/or electron densities from UV or EUV emission line data. We present our atomic data in the form of scaling laws so that, given the isotopic nuclear spin and magnetic moment, a simple expression yields estimates for HPF induced decay rates. We examine some UV solar and nebular data in the light of these new results and suggest possible cases for future study. We could not find evidence for the existence of HPF induced lines in the spectra we examined, but we demonstrate that existing data have come close to providing interesting upper limits. For the planetary nebula SMC N2 we derive an upper limit of (13) C/(12) C of 0.1 from GHRS data obtained by Clegg. It is likely that more stringent limits could be obtained with newer data with higher sensitivities in a variety of objects.

Spin-state transfer in laterally coupled quantum-dot chains with disorders

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang Song; Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026; Bayat, Abolfazl

2010-08-15

Quantum dot arrays are a promising medium for transferring quantum information between two distant points without resorting to mobile qubits. Here we study the two most common disorders, namely hyperfine interaction and exchange coupling fluctuations, in quantum dot arrays and their effects on quantum communication through these chains. Our results show that the hyperfine interaction is more destructive than the exchange coupling fluctuations. The average optimal time for communication is not affected by any disorder in the system and our simulations show that antiferromagnetic chains are much more resistive than the ferromagnetic ones against both kind of disorders. Even whenmore » time modulation of a coupling and optimal control is employed to improve the transmission, the antiferromagnetic chain performs much better. We have assumed the quasistatic approximation for hyperfine interaction and time-dependent fluctuations in the exchange couplings. Particularly for studying exchange coupling fluctuations we have considered the static disorder, white noise, and 1/f noise.« less

An ESR study of the stable radical in a γ-irradiated single crystal of 17α-dydroxy-progesterone

NASA Astrophysics Data System (ADS)

Krzyminiewski, R.; Pietrzak, J.; Konopka, R.

1990-11-01

Electron spin resonance spectroscopy was used to investigate γ-radiation damage of 17α-hydroxy-progesterone molecules in a single crystal. Two types of radicals with different rates of recombination were observed and a definite structure was assigned to the specimen by analyzing the orientational variation of the spectra. The unpaired electron of the radical is delocalized in the 2 pz orbitals of the C(6), C(4) and C(3) atoms, giving rise to a hyperfine spectrum by interaction with two equivalent α-protons in positions 4 and 6 and with two non-equivalent β-protons attached to C(7). The hyperfine coupling tensors are reported, together with the g tensor of the radical. The presence of additional intermolecular interactions caused by hydrogen bonding between O(3) and HO(17) of two molecules does not change the type of radical (which is the same as the stable radical in a γ-irradiated single crystal of progesterone) but does increase the hyperfine coupling anisotropy.

Spin polarization of {sup 87}Rb atoms with ultranarrow linewidth diode laser: Numerical simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Z. G.; Interdisciplinary Center of Quantum Information, National University of Defense Technology, Changsha, 410073; College of Science, National University of Defense Technology, Changsha, 410073

2016-08-15

In order to polarize {sup 87}Rb vapor effectively with ultranarrow linewidth diode laser, we studied the polarization as a function of some parameters including buffer gas pressure and laser power. Moreover, we also discussed the methods which split or modulate the diode laser frequency so as to pump the two ground hyperfine levels efficiently. We obtained some useful results through numerical simulation. If the buffer gas pressure is so high that the hyperfine structure is unresolved, the polarization is insensitive to laser frequency at peak absorption point so frequency splitting and frequency modulation methods do not show improvement. At lowmore » pressure and laser power large enough, where the hyperfine structure is clearly resolved, frequency splitting and frequency modulation methods can increase polarization effectively. For laser diodes, frequency modulation is easily realized with current modulation, so this method is attractive since it does not add any other components in the pumping laser system.« less

Dephasing due to Nuclear Spins in Large-Amplitude Electric Dipole Spin Resonance.

PubMed

Chesi, Stefano; Yang, Li-Ping; Loss, Daniel

2016-02-12

We analyze effects of the hyperfine interaction on electric dipole spin resonance when the amplitude of the quantum-dot motion becomes comparable or larger than the quantum dot's size. Away from the well-known small-drive regime, the important role played by transverse nuclear fluctuations leads to a Gaussian decay with characteristic dependence on drive strength and detuning. A characterization of spin-flip gate fidelity, in the presence of such additional drive-dependent dephasing, shows that vanishingly small errors can still be achieved at sufficiently large amplitudes. Based on our theory, we analyze recent electric dipole spin resonance experiments relying on spin-orbit interactions or the slanting field of a micromagnet. We find that such experiments are already in a regime with significant effects of transverse nuclear fluctuations and the form of decay of the Rabi oscillations can be reproduced well by our theory.

Ultrafast optical control of individual quantum dot spin qubits.

PubMed

De Greve, Kristiaan; Press, David; McMahon, Peter L; Yamamoto, Yoshihisa

2013-09-01

Single spins in semiconductor quantum dots form a promising platform for solid-state quantum information processing. The spin-up and spin-down states of a single electron or hole, trapped inside a quantum dot, can represent a single qubit with a reasonably long decoherence time. The spin qubit can be optically coupled to excited (charged exciton) states that are also trapped in the quantum dot, which provides a mechanism to quickly initialize, manipulate and measure the spin state with optical pulses, and to interface between a stationary matter qubit and a 'flying' photonic qubit for quantum communication and distributed quantum information processing. The interaction of the spin qubit with light may be enhanced by placing the quantum dot inside a monolithic microcavity. An entire system, consisting of a two-dimensional array of quantum dots and a planar microcavity, may plausibly be constructed by modern semiconductor nano-fabrication technology and could offer a path toward chip-sized scalable quantum repeaters and quantum computers. This article reviews the recent experimental developments in optical control of single quantum dot spins for quantum information processing. We highlight demonstrations of a complete set of all-optical single-qubit operations on a single quantum dot spin: initialization, an arbitrary SU(2) gate, and measurement. We review the decoherence and dephasing mechanisms due to hyperfine interaction with the nuclear-spin bath, and show how the single-qubit operations can be combined to perform spin echo sequences that extend the qubit decoherence from a few nanoseconds to several microseconds, more than 5 orders of magnitude longer than the single-qubit gate time. Two-qubit coupling is discussed, both within a single chip by means of exchange coupling of nearby spins and optically induced geometric phases, as well as over longer-distances. Long-distance spin-spin entanglement can be generated if each spin can emit a photon that is entangled with the spin, and these photons are then interfered. We review recent work demonstrating entanglement between a stationary spin qubit and a flying photonic qubit. These experiments utilize the polarization- and frequency-dependent spontaneous emission from the lowest charged exciton state to single spin Zeeman sublevels.

Massively parallel implementations of coupled-cluster methods for electron spin resonance spectra. I. Isotropic hyperfine coupling tensors in large radicals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verma, Prakash; Morales, Jorge A., E-mail: jorge.morales@ttu.edu; Perera, Ajith

2013-11-07

Coupled cluster (CC) methods provide highly accurate predictions of molecular properties, but their high computational cost has precluded their routine application to large systems. Fortunately, recent computational developments in the ACES III program by the Bartlett group [the OED/ERD atomic integral package, the super instruction processor, and the super instruction architecture language] permit overcoming that limitation by providing a framework for massively parallel CC implementations. In that scheme, we are further extending those parallel CC efforts to systematically predict the three main electron spin resonance (ESR) tensors (A-, g-, and D-tensors) to be reported in a series of papers. Inmore » this paper inaugurating that series, we report our new ACES III parallel capabilities that calculate isotropic hyperfine coupling constants in 38 neutral, cationic, and anionic radicals that include the {sup 11}B, {sup 17}O, {sup 9}Be, {sup 19}F, {sup 1}H, {sup 13}C, {sup 35}Cl, {sup 33}S,{sup 14}N, {sup 31}P, and {sup 67}Zn nuclei. Present parallel calculations are conducted at the Hartree-Fock (HF), second-order many-body perturbation theory [MBPT(2)], CC singles and doubles (CCSD), and CCSD with perturbative triples [CCSD(T)] levels using Roos augmented double- and triple-zeta atomic natural orbitals basis sets. HF results consistently overestimate isotropic hyperfine coupling constants. However, inclusion of electron correlation effects in the simplest way via MBPT(2) provides significant improvements in the predictions, but not without occasional failures. In contrast, CCSD results are consistently in very good agreement with experimental results. Inclusion of perturbative triples to CCSD via CCSD(T) leads to small improvements in the predictions, which might not compensate for the extra computational effort at a non-iterative N{sup 7}-scaling in CCSD(T). The importance of these accurate computations of isotropic hyperfine coupling constants to elucidate experimental ESR spectra, to interpret spin-density distributions, and to characterize and identify radical species is illustrated with our results from large organic radicals. Those include species relevant for organic chemistry, petroleum industry, and biochemistry, such as the cyclo-hexyl, 1-adamatyl, and Zn-porphycene anion radicals, inter alia.« less

Spin manipulation and spin-lattice interaction in magnetic colloidal quantum dots

NASA Astrophysics Data System (ADS)

Moro, Fabrizio; Turyanska, Lyudmila; Granwehr, Josef; Patanè, Amalia

2014-11-01

We report on the spin-lattice interaction and coherent manipulation of electron spins in Mn-doped colloidal PbS quantum dots (QDs) by electron spin resonance. We show that the phase memory time,TM , is limited by Mn-Mn dipolar interactions, hyperfine interactions of the protons (1H) on the QD capping ligands with Mn ions in their proximity (<1 nm), and surface phonons originating from thermal fluctuations of the capping ligands. In the low Mn concentration limit and at low temperature, we achieve a long phase memory time constant TM˜0.9 μ s , thus enabling the observation of Rabi oscillations. Our findings suggest routes to the rational design of magnetic colloidal QDs with phase memory times exceeding the current limits of relevance for the implementation of QDs as qubits in quantum information processing.

Entangling atomic spins with a Rydberg-dressed spin-flip blockade

DOE PAGES

Jau, Y. -Y.; Hankin, A. M.; Keating, T.; ...

2015-10-05

Controlling the quantum entanglement between parts of a many-body system is key to unlocking the power of quantum technologies such as quantum computation, high-precision sensing, and the simulation of many-body physics. The spin degrees of freedom of ultracold neutral atoms in their ground electronic state provide a natural platform for such applications thanks to their long coherence times and the ability to control them with magneto-optical fields. However, the creation of strong coherent coupling between spins has been challenging. In this paper, we demonstrate a strong and tunable Rydberg-dressed interaction between spins of individually trapped caesium atoms with energy shiftsmore » of order 1 MHz in units of Planck’s constant. This interaction leads to a ground-state spin-flip blockade, whereby simultaneous hyperfine spin flips of two atoms are inhibited owing to their mutual interaction. Finally, we employ this spin-flip blockade to rapidly produce single-step Bell-state entanglement between two atoms with a fidelity ≥81(2)%.« less

QCCM - Center for NMR Quantum Information Processing

DTIC Science & Technology

2011-02-16

2008, 77, 010802, 1 – 6. 8. Universal control of nuclear spins via anisotropic hyperfine interactions J. S. Hodges, J. C. Yang, C. Ramanthan and D. G...sample environmental noise over a broad frequency range 0.2-20MHz, and we observe a 1/fα-type spectrum which we independently confirm with a Rabi

Magnetoelectroluminescence of organic heterostructures: Analytical theory and spectrally resolved measurements

DOE PAGES

Liu, Feilong; Kelley, Megan R.; Crooker, Scott A.; ...

2014-12-22

The effect of a magnetic field on the electroluminescence of organic light emitting devices originates from the hyperfine interaction between the electron/hole polarons and the hydrogen nuclei of the host molecules. In this paper, we present an analytical theory of magnetoelectroluminescence for organic semiconductors. To be specific, we focus on bilayer heterostructure devices. In the case we are considering, light generation at the interface of the donor and acceptor layers results from the formation and recombination of exciplexes. The spin physics is described by a stochastic Liouville equation for the electron/hole spin density matrix. By finding the steady-state analytical solutionmore » using Bloch-Wangsness-Redfield theory, we explore how the singlet/triplet exciplex ratio is affected by the hyperfine interaction strength and by the external magnetic field. In order to validate the theory, spectrally resolved electroluminescence experiments on BPhen/m-MTDATA devices are analyzed. With increasing emission wavelength, the width of the magnetic field modulation curve of the electroluminescence increases while its depth decreases. Furthermore, these observations are consistent with the model.« less

Tetraquark mixing framework for isoscalar resonances in light mesons

NASA Astrophysics Data System (ADS)

Kim, Hungchong; Kim, K. S.; Cheoun, Myung-Ki; Oka, Makoto

2018-05-01

Recently, a tetraquark mixing framework has been proposed for light mesons and applied more or less successfully to the isovector resonances, a0(980 ) , a0(1450 ) , as well as to the isodoublet resonances, K0*(800 ),K0*(1430 ). In this work, we present a more extensive view on the mixing framework and apply this framework to the isoscalar resonances, f0(500 ), f0(980 ), f0(1370 ), f0(1500 ). Tetraquarks in this framework can have two spin configurations containing either spin-0 diquark or spin-1 diquark and each configuration forms a nonet in flavor space. The two spin configurations are found to mix strongly through the color-spin interactions. Their mixtures, which diagonalize the hyperfine masses, can generate the physical resonances constituting two nonets, which, in fact, coincide roughly with the experimental observation. We identify that f0(500 ), f0(980 ) are the isoscalar members in the light nonet, and f0(1370 ), f0(1500 ) are the similar members in the heavy nonet. This means that the spin configuration mixing, as it relates the corresponding members in the two nonets, can generate f0(500 ) , f0(1370 ) among the members in light mass, and f0(980 ) , f0(1500 ) in heavy mass. The complication arises because the isoscalar members of each nonet are subject to an additional flavor mixing known as Okubo-Zweig-Iizuka rule so that f0(500 ) , f0(980 ) , and similarly f0(1370 ) , f0(1500 ) , are the mixture of two isoscalar members belonging to an octet and a singlet in SUf(3 ) . The tetraquark mixing framework including the flavor mixing is tested for the isoscalar resonances in terms of the mass splitting and the fall-apart decay modes. The mass splitting among the isoscalar resonances is found to be consistent qualitatively with their hyperfine mass splitting strongly driven by the spin configuration mixing, which suggests that the tetraquark mixing framework works. The fall-apart modes from our tetraquarks also seem to be consistent with the experimental modes. We also discuss possible existence of the spin-1 tetraquarks that can be constructed by the spin-1 diquark.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gómez, A. M., E-mail: amgomezl-1@uqvirtual.edu.co; Torres, D. A., E-mail: datorresg@unal.edu.co

The experimental study of nuclear magnetic moments, using the Transient Field technique, makes use of spin-orbit hyperfine interactions to generate strong magnetic fields, above the kilo-Tesla regime, capable to create a precession of the nuclear spin. A theoretical description of such magnetic fields is still under theoretical research, and the use of parametrizations is still a common way to address the lack of theoretical information. In this contribution, a review of the main parametrizations utilized in the measurements of Nuclear Magnetic Moments will be presented, the challenges to create a theoretical description from first principles will be discussed.

Hyperfine interactions in titanates: Study of orbital ordering and local magnetic properties

NASA Astrophysics Data System (ADS)

Agzamova, P. A.; Leskova, Yu. V.; Nikiforov, A. E.

2013-05-01

Hyperfine magnetic fields induced on the nuclei of nonmagnetic ions 139La and 89Y in LaTiO3 and YTiO3, respectively, have been microscopically calculated. The dependence of the hyperfine fields on the orbital and magnetic structures of the compounds under study has been analyzed. The comparative analysis of the calculated and known experimental data confirms the existence of the static orbital structure in lanthanum and yttrium titanates.

Identification of the substrate radical intermediate derived from ethanolamine during catalysis by ethanolamine ammonia-lyase.

PubMed

Bender, Güneş; Poyner, Russell R; Reed, George H

2008-10-28

Rapid-mix freeze-quench (RMFQ) methods and electron paramagnetic resonance (EPR) spectroscopy have been used to characterize the steady-state radical in the deamination of ethanolamine catalyzed by adenosylcobalamin (AdoCbl)-dependent ethanolamine ammonia-lyase (EAL). EPR spectra of the radical intermediates formed with the substrates, [1-13C]ethanolamine, [2-13C]ethanolamine, and unlabeled ethanolamine were acquired using RMFQ trapping methods from 10 ms to completion of the reaction. Resolved 13C hyperfine splitting in EPR spectra of samples prepared with [1-13C]ethanolamine and the absence of such splitting in spectra of samples prepared with [2-13C]ethanolamine show that the unpaired electron is localized on C1 (the carbinol carbon) of the substrate. The 13C splitting from C1 persists from 10 ms throughout the time course of substrate turnover, and there was no evidence of a detectable amount of a product like radical having unpaired spin on C2. These results correct an earlier assignment for this radical intermediate [Warncke, K., et al. (1999) J. Am. Chem. Soc. 121, 10522-10528]. The EPR signals of the substrate radical intermediate are altered by electron spin coupling to the other paramagnetic species, cob(II)alamin, in the active site. The dipole-dipole and exchange interactions as well as the 1-13C hyperfine splitting tensor were analyzed via spectral simulations. The sign of the isotropic exchange interaction indicates a weak ferromagnetic coupling of the two unpaired electrons. A Co2+-radical distance of 8.7 A was obtained from the magnitude of the dipole-dipole interaction. The orientation of the principal axes of the 13C hyperfine splitting tensor shows that the long axis of the spin-bearing p orbital on C1 of the substrate radical makes an angle of approximately 98 degrees with the unique axis of the d(z2) orbital of Co2+.

Gate-defined Quantum Confinement in Suspended Bilayer Graphene

NASA Astrophysics Data System (ADS)

Allen, Monica

2013-03-01

Quantum confined devices in carbon-based materials offer unique possibilities for applications ranging from quantum computation to sensing. In particular, nanostructured carbon is a promising candidate for spin-based quantum computation due to the ability to suppress hyperfine coupling to nuclear spins, a dominant source of spin decoherence. Yet graphene lacks an intrinsic bandgap, which poses a serious challenge for the creation of such devices. We present a novel approach to quantum confinement utilizing tunnel barriers defined by local electric fields that break sublattice symmetry in suspended bilayer graphene. This technique electrostatically confines charges via band structure control, thereby eliminating the edge and substrate disorder that hinders on-chip etched nanostructures to date. We report clean single electron tunneling through gate-defined quantum dots in two regimes: at zero magnetic field using the energy gap induced by a perpendicular electric field and at finite magnetic fields using Landau level confinement. The observed Coulomb blockade periodicity agrees with electrostatic simulations based on local top-gate geometry, a direct demonstration of local control over the band structure of graphene. This technology integrates quantum confinement with pristine device quality and access to vibrational modes, enabling wide applications from electromechanical sensors to quantum bits. More broadly, the ability to externally tailor the graphene bandgap over nanometer scales opens a new unexplored avenue for creating quantum devices.

Revealing weak spin-orbit coupling effects on charge carriers in a π -conjugated polymer

NASA Astrophysics Data System (ADS)

Malissa, H.; Miller, R.; Baird, D. L.; Jamali, S.; Joshi, G.; Bursch, M.; Grimme, S.; van Tol, J.; Lupton, J. M.; Boehme, C.

2018-04-01

We measure electrically detected magnetic resonance on organic light-emitting diodes made of the polymer poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] at room temperature and high magnetic fields where spectral broadening of the resonance due to spin-orbit coupling (SOC) exceeds that due to the local hyperfine fields. Density-functional-theory calculations on an open-shell model of the material reveal g -tensors of charge-carrier spins in the lowest unoccupied (electron) and highest occupied (hole) molecular orbitals. These tensors are used for simulations of magnetic resonance line shapes. Besides providing the first quantification and direct observation of SOC effects on charge-carrier states in these weakly SO-coupled hydrocarbons, this procedure demonstrates that spin-related phenomena in these materials are fundamentally monomolecular in nature.

Coherent storage of temporally multimode light using a spin-wave atomic frequency comb memory

NASA Astrophysics Data System (ADS)

Gündoǧan, M.; Mazzera, M.; Ledingham, P. M.; Cristiani, M.; de Riedmatten, H.

2013-04-01

We report on the coherent and multi-temporal mode storage of light using the full atomic frequency comb memory scheme. The scheme involves the transfer of optical atomic excitations in Pr3+:Y2SiO5 to spin waves in hyperfine levels using strong single-frequency transfer pulses. Using this scheme, a total of five temporal modes are stored and recalled on-demand from the memory. The coherence of the storage and retrieval is characterized using a time-bin interference measurement resulting in visibilities higher than 80%, independent of the storage time. This coherent and multimode spin-wave memory is promising as a quantum memory for light.

Fast Single-Shot Hold Spin Readout in Double Quantum Dots

NASA Astrophysics Data System (ADS)

Bogan, Alexander; Studenikin, Sergei; Korkusinski, Marek; Aers, Geof; Gaudreau, Louis; Zawadzki, Piotr; Sachrajda, Andy; Tracy, Lisa; Reno, John; Hargett, Terry

Solid state spin qubits in quantum dots hold promise as scalable, high-density qubits in quantum information processing architectures. While much of the experimental investigation of these devices and their physics has focused on confined electron spins, hole spins in III-V semiconductors are attractive alternatives to electrons due to the reduced hyperfine coupling between the spin and the incoherent nuclear environment. In this talk, we will discuss a measurement protocol of the hole spin relaxation time T1 in a gated lateral GaAs double quantum dot tuned to the one and two-hole regimes, as well as a new technique for single-shot projective measurement of a single spin in tens of nanoseconds or less. The technique makes use of fast non-spin-conserving inter-dot transitions permitted by strong spin-orbit interactions for holes, as well as the latching of the charge state of the second quantum dot for enhanced sensitivity. This technique allows a direct measurement of the single spin relaxation time on time-scales set by physical device rather than by limitations of the measurement circuit.

Suppression of Pauli Spin Blockade in Few Hole Laterally Gated Double Quantum Dots

NASA Astrophysics Data System (ADS)

Gaudreau, Louis; Bogan, Alex; Studenikin, Sergei; Korkusinski, Marek; Aers, Geof; Zawadzki, Piotr; Sachrajda, Andy; Tracy, Lisa; Reno, John; Hargett, Terry; National Research Council Team; Sandia Labs Team

Hole spins have attracted increasing attention as candidates for qubits in quantum information applications. The p-type character of their wavefunction leads to smaller hyperfine interaction with the nuclei resulting in longer coherence times. Additionally, strong spin-orbit interaction allows for enhanced all-electrical manipulation of spin qubit states. Single hole spins have been electrically studied in InSb and Si nanowire quantum dots, however, electrostatically confined hole spins in a 2D hole gas have thus far been limited to the many hole regime. In this talk we will present a full description of the two-hole spin spectrum in a lateral GaAs/AlGaAs double quantum. High-bias magneto-transport spectroscopy reveals all four states of the spectrum (singlet and triplets) in both the (1,1) and (2,0) configurations, essential for spin readout based on Pauli spin blockade. We show that spin-flip tunneling between dots is as strong as spin conserving tunneling, a consequence of the strong spin-orbit interaction. This suppresses the Pauli spin blockade. Our results suggest that alternate techniques for single hole spin qubit readout need to be explored.

High-efficiency optical pumping of nuclear polarization in a GaAs quantum well

NASA Astrophysics Data System (ADS)

Mocek, R. W.; Korenev, V. L.; Bayer, M.; Kotur, M.; Dzhioev, R. I.; Tolmachev, D. O.; Cascio, G.; Kavokin, K. V.; Suter, D.

2017-11-01

The dynamic polarization of nuclear spins by photoexcited electrons is studied in a high quality GaAs/AlGaAs quantum well. We find a surprisingly high efficiency of the spin transfer from the electrons to the nuclei as reflected by a maximum nuclear field of 0.9 T in a tilted external magnetic field of 1 T strength only. This high efficiency is due to a low leakage of spin out of the polarized nuclear system, because mechanisms of spin relaxation other than the hyperfine interaction are strongly suppressed, leading to a long nuclear relaxation time of up to 1000 s. A key ingredient to that end is the low impurity concentration inside the heterostructure, while the electrostatic potential from charged impurities in the surrounding barriers becomes screened through illumination by which the spin relaxation time is increased compared to keeping the system in the dark. This finding indicates a strategy for obtaining high nuclear spin polarization as required for long-lasting carrier spin coherence.

International Conference on Quantum Chemical Calculations of NMR and EPR Parameters Held in Castle Smolenice, Slovak Republic on September 14-18 1998

DTIC Science & Technology

1998-10-21

site. The electric-field- induced linear shift is also observed in the hyperfine splitting of nuclear quadrupole resonance ( NQR ) spectrum of a nucleus...located at a noncentrosymmetric site in a molecule or in crystal lattice. Thus, the linear electric field effect on the ESR and NQR hyperfine splitting...the electric field effects on ESR and NQR hyperfine couplings. Theoretical methods to calculate the electric field effects within Hartree-Fock

Many-body physics using cold atoms

NASA Astrophysics Data System (ADS)

Sundar, Bhuvanesh

Advances in experiments on dilute ultracold atomic gases have given us access to highly tunable quantum systems. In particular, there have been substantial improvements in achieving different kinds of interaction between atoms. As a result, utracold atomic gases oer an ideal platform to simulate many-body phenomena in condensed matter physics, and engineer other novel phenomena that are a result of the exotic interactions produced between atoms. In this dissertation, I present a series of studies that explore the physics of dilute ultracold atomic gases in different settings. In each setting, I explore a different form of the inter-particle interaction. Motivated by experiments which induce artificial spin-orbit coupling for cold fermions, I explore this system in my first project. In this project, I propose a method to perform universal quantum computation using the excitations of interacting spin-orbit coupled fermions, in which effective p-wave interactions lead to the formation of a topological superfluid. Motivated by experiments which explore the physics of exotic interactions between atoms trapped inside optical cavities, I explore this system in a second project. I calculate the phase diagram of lattice bosons trapped in an optical cavity, where the cavity modes mediates effective global range checkerboard interactions between the atoms. I compare this phase diagram with one that was recently measured experimentally. In two other projects, I explore quantum simulation of condensed matter phenomena due to spin-dependent interactions between particles. I propose a method to produce tunable spin-dependent interactions between atoms, using an optical Feshbach resonance. In one project, I use these spin-dependent interactions in an ultracold Bose-Fermi system, and propose a method to produce the Kondo model. I propose an experiment to directly observe the Kondo effect in this system. In another project, I propose using lattice bosons with a large hyperfine spin, which have Feshbach-induced spin-dependent interactions, to produce a quantum dimer model. I propose an experiment to detect the ground state in this system. In a final project, I develop tools to simulate the dynamics of fermionic superfluids in which fermions interact via a short-range interaction.

Masses of constituent quarks confined in open bottom hadrons

NASA Astrophysics Data System (ADS)

Borka Jovanović, V.; Borka, D.; Jovanović, P.; Milošević, J.; Ignjatović, S. R.

2014-12-01

We apply color-spin and flavor-spin quark-quark interactions to the meson and baryon constituent quarks, and calculate constituent quark masses, as well as the coupling constants of these interactions. The main goal of this paper was to determine constituent quark masses from light and open bottom hadron masses, using the fitting method we have developed and clustering of hadron groups. We use color-spin Fermi-Breit (FB) and flavor-spin Glozman-Riska (GR) hyperfine interaction (HFI) to determine constituent quark masses (especially b quark mass). Another aim was to discern between the FB and GR HFI because our previous findings had indicated that both interactions were satisfactory. Our improved fitting procedure of constituent quark masses showed that on average color-spin (FB) HFI yields better fits. The method also shows the way how the constituent quark masses and the strength of the interaction constants appear in different hadron environments.

Arbitrary Dicke-State Control of Symmetric Rydberg Ensembles

NASA Astrophysics Data System (ADS)

Deutsch, Ivan

2017-04-01

We study the production of arbitrary superpositions of Dicke states via optimal control. We show that N atomic hyperfine qubits, interacting symmetrically via the Rydberg blockade, are well described by the Jaynes-Cummings Model (JCM), familiar in cavity QED. In this isomorphism, the presence or absence of a collective Rydberg excitation plays the role of the two-level system and the number of symmetric excitations of the hyperfine qubits plays the role of the bosonic excitations of the JCM. This system is fully controllable through the addition of phase-modulated microwaves that drive transitions between the Rydberg-dressed states. In the weak dressing regime, this results in a single-axis twisting Hamiltonian, plus time-dependent rotations of the collective spin. For strong dressing we control the entire Jaynes-Cummings ladder. Using optimal control, we design microwave waveforms that can generate arbitrary states in the symmetric subspace. This includes cat states, Dicke states, and spin squeezed states. With currently feasible parameters, it is possible to generate arbitrary symmetric states of _10 hyperfine qubits in 1 microsec, assuming a fast microwave phase switching time. The same control can be achieved with a ``dressed-ground control'' scheme, which reduces the demands for fast phase switching at the expense of increased total control time. More generally, we can achieve control on larger ensembles of qubits by designing waveforms that are bandwidth limited within the coherence time of the system. We use this to study general questions of the ``quantum speed limit'' and information content in a waveform that is needed to generate arbitrary quantum states.

Determining the Topology of Integral Membrane Peptides Using EPR Spectroscopy

PubMed Central

Inbaraj, Johnson J.; Cardon, Thomas B.; Laryukhin, Mikhail; Grosser, Stuart M.

2008-01-01

This paper reports on the development of a new structural biology technique for determining the membrane topology of an integral membrane protein inserted into magnetically aligned phospholipid bilayers (bicelles) using EPR spectroscopy. The nitroxide spin probe, 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid (TOAC) was attached to the pore-lining transmembrane domain (M2δ) of the nicotinic acetylcholine receptor (AChR) and incorporated into a bicelle. The corresponding EPR spectra revealed hyperfine splittings that were highly dependent on the macroscopic orientation of the bicelles with respect to the static magnetic field. The helical tilt of the peptide can be easily calculated using the hyperfine splittings gleaned from the orientational dependent EPR spectra. A helical tilt of 14° was calculated for the M2δ peptide with respect to the bilayer normal of the membrane, which agrees well with previous 15N solid-state NMR studies. The helical tilt of the peptide was verified by simulating the corresponding EPR spectra using the standardized MOMD approach. This new method is advantageous because: (1) bicelle samples are easy to prepare, (2) the helical tilt can be directly calculated from the orientational-dependent hyperfine splitting in the EPR spectra, and (3) EPR spectroscopy is approximately 1000 fold more sensitive than 15N solid-state NMR spectroscopy; thus, the helical tilt of an integral membrane peptide can be determined with only 100 μg of peptide. The helical tilt can be determined more accurately by placing TOAC spin labels at several positions with this technique. PMID:16848493

Verdazyl-ribose: A new radical for solid-state dynamic nuclear polarization at high magnetic field

NASA Astrophysics Data System (ADS)

Thurber, Kent R.; Le, Thanh-Ngoc; Changcoco, Victor; Brook, David J. R.

2018-04-01

Solid-state dynamic nuclear polarization (DNP) using the cross-effect relies on radical pairs whose electron spin resonance (ESR) frequencies differ by the nuclear magnetic resonance (NMR) frequency. We measure the DNP provided by a new water-soluble verdazyl radical, verdazyl-ribose, under both magic-angle spinning (MAS) and static sample conditions at 9.4 T, and compare it to a nitroxide radical, 4-hydroxy-TEMPO. We find that verdazyl-ribose is an effective radical for cross-effect DNP, with the best relative results for a non-spinning sample. Under non-spinning conditions, verdazyl-ribose provides roughly 2× larger 13C cross-polarized (CP) NMR signal than the nitroxide, with similar polarization buildup times, at both 29 K and 76 K. With MAS at 7 kHz and 1.5 W microwave power, the verdazyl-ribose does not provide as much DNP as the nitroxide, with the verdazyl providing less NMR signal and a longer polarization buildup time. When the microwave power is decreased to 30 mW with 5 kHz MAS, the two types of radical are comparable, with the verdazyl-doped sample having a larger NMR signal which compensates for its longer polarization buildup time. We also present electron spin relaxation measurements at Q-band (1.2 T) and ESR lineshapes at 1.2 and 9.4 T. Most notably, the verdazyl radical has a longer T1e than the nitroxide (9.9 ms and 1.3 ms, respectively, at 50 K and 1.2 T). The verdazyl electron spin lineshape is significantly affected by the hyperfine coupling to four 14N nuclei, even at 9.4 T. We also describe 3000-spin calculations to illustrate the DNP potential of possible radical pairs: verdazyl-verdazyl, verdazyl-nitroxide, or nitroxide-nitroxide pairs. These calculations suggest that the verdazyl radical at 9.4 T has a narrower linewidth than optimal for cross-effect DNP using verdazyl-verdazyl pairs. Because of the hyperfine coupling contribution to the electron spin linewidth, this implies that DNP using the verdazyl radical would improve at lower magnetic field. Another conclusion from the calculations is that a verdazyl-nitroxide bi-radical would be expected to be slightly better for cross-effect DNP than the nitroxide-nitroxide bi-radicals commonly used now, assuming the same spin-spin coupling constants.

29Si-NMR study of magnetic anisotropy and hyperfine interactions in the uranium-bsed ferromagnet UNiSi2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakai, Hironori; Baek, Seung H; Bauer, Eric D

2009-01-01

UNiSi{sub 2} orders ferromagnetically below T{sub Curie} = 95 K. This material crystallizes in the orthorhombic CeNiSi{sub 2}-type structure. The uranium atoms form double-layers, which are stacked along the crystallographic b axis (the longest axis). From magnetization measurement the easy (hard) magnetization axis is found to be the c axis (b axis). {sup 29}Si-NMR measurements have been performed in the paramagnetic state. In UNiSi{sub 2}, two crystallographic Si sites exist with orthorhombic local symmetry. The Knight shifts on each Si site have been estimated from the spectra of random and oriented powders. The transferred hyperfine couplings have been also derived.more » It is found that the transferred hyperfine coupling constants on each Si site are nearly isotropic, and that their Knight shift anisotropy comes from that of the bulk susceptibility. The nuclear-spin lattice relaxation rate 1/T{sub 1} shows temperature-independent behavior, which indicates the existence of localized 5f electron.« less

Studies of the spin Hamiltonian parameters and local structure for ZnO:Cu2+.

PubMed

Wu, Shao-Yi; Wei, Li-Hua; Zhang, Zhi-Hong; Wang, Xue-Feng; Hu, Yue-Xia

2008-12-15

The spin Hamiltonian parameters (the g factors and the hyperfine structure constants) and local structure for ZnO:Cu2+ are theoretically studied from the perturbation formulas of these parameters for a 3d9 ion under trigonally distorted tetrahedra. The ligand orbital and spin-orbit coupling contributions are taken into account from the cluster approach due to the significant covalency of the [CuO4](6-) cluster. According to the investigations, the impurity Cu2+ is suggested not to locate on the ideal Zn2+ site in ZnO but to undergo a slight outward displacement (approximately 0.01 angstroms) away from the ligand triangle along C3 axis. The calculated spin Hamiltonian parameters are in good agreement with the observed values. The validity of the above impurity displacement is also discussed.

Decoupling a hole spin qubit from the nuclear spins.

PubMed

Prechtel, Jonathan H; Kuhlmann, Andreas V; Houel, Julien; Ludwig, Arne; Valentin, Sascha R; Wieck, Andreas D; Warburton, Richard J

2016-09-01

A huge effort is underway to develop semiconductor nanostructures as low-noise hosts for qubits. The main source of dephasing of an electron spin qubit in a GaAs-based system is the nuclear spin bath. A hole spin may circumvent the nuclear spin noise. In principle, the nuclear spins can be switched off for a pure heavy-hole spin. In practice, it is unknown to what extent this ideal limit can be achieved. A major hindrance is that p-type devices are often far too noisy. We investigate here a single hole spin in an InGaAs quantum dot embedded in a new generation of low-noise p-type device. We measure the hole Zeeman energy in a transverse magnetic field with 10 neV resolution by dark-state spectroscopy as we create a large transverse nuclear spin polarization. The hole hyperfine interaction is highly anisotropic: the transverse coupling is <1% of the longitudinal coupling. For unpolarized, randomly fluctuating nuclei, the ideal heavy-hole limit is achieved down to nanoelectronvolt energies; equivalently dephasing times up to a microsecond. The combination of large and strong optical dipole makes the single hole spin in a GaAs-based device an attractive quantum platform.

Quantum memory operations in a flux qubit - spin ensemble hybrid system

NASA Astrophysics Data System (ADS)

Saito, S.; Zhu, X.; Amsuss, R.; Matsuzaki, Y.; Kakuyanagi, K.; Shimo-Oka, T.; Mizuochi, N.; Nemoto, K.; Munro, W. J.; Semba, K.

2014-03-01

Superconducting quantum bits (qubits) are one of the most promising candidates for a future large-scale quantum processor. However for larger scale realizations the currently reported coherence times of these macroscopic objects (superconducting qubits) has not yet reached those of microscopic systems (electron spins, nuclear spins, etc). In this context, a superconductor-spin ensemble hybrid system has attracted considerable attention. The spin ensemble could operate as a quantum memory for superconducting qubits. We have experimentally demonstrated quantum memory operations in a superconductor-diamond hybrid system. An excited state and a superposition state prepared in the flux qubit can be transferred to, stored in and retrieved from the NV spin ensemble in diamond. From these experiments, we have found the coherence time of the spin ensemble is limited by the inhomogeneous broadening of the electron spin (4.4 MHz) and by the hyperfine coupling to nitrogen nuclear spins (2.3 MHz). In the future, spin echo techniques could eliminate these effects and elongate the coherence time. Our results are a significant first step in utilizing the spin ensemble as long-lived quantum memory for superconducting flux qubits. This work was supported by the FIRST program and NICT.

Optical Polarization of Nuclear Spins in Silicon Carbide

NASA Astrophysics Data System (ADS)

Falk, Abram L.; Klimov, Paul V.; Ivády, Viktor; Szász, Krisztián; Christle, David J.; Koehl, William F.; Gali, Ádám; Awschalom, David D.

2015-06-01

We demonstrate optically pumped dynamic nuclear polarization of 29Si nuclear spins that are strongly coupled to paramagnetic color centers in 4 H - and 6 H -SiC. The 9 9 % ±1 % degree of polarization that we observe at room temperature corresponds to an effective nuclear temperature of 5 μ K . By combining ab initio theory with the experimental identification of the color centers' optically excited states, we quantitatively model how the polarization derives from hyperfine-mediated level anticrossings. These results lay a foundation for SiC-based quantum memories, nuclear gyroscopes, and hyperpolarized probes for magnetic resonance imaging.

EPR studies of Er 3+, Nd 3+ and Ce 3+ in YAlO 3 single crystals

NASA Astrophysics Data System (ADS)

Asatryan, H. R.; Rosa, J.; Mareš, J. A.

1997-10-01

EPR spectra of Er 3+, Nd 3+ and Ce 3+ ions in YAlO 3 lattice have been studied. These spectra can be described by spin Hamiltonian with an effective spin S = {1}/{2} and rhombohedric symmetry. The g factors as well as the constants of hyperfine interaction of Nd 3+ and Er 3+ were obtained. It was stated that all the resonances which are upon the interest of this article, belong to the RE 3+ ions replacing the Y 3+ cations in the YAlO 3 lattice.

Long-Lived Ultracold Molecules with Electric and Magnetic Dipole Moments.

PubMed

Rvachov, Timur M; Son, Hyungmok; Sommer, Ariel T; Ebadi, Sepehr; Park, Juliana J; Zwierlein, Martin W; Ketterle, Wolfgang; Jamison, Alan O

2017-10-06

We create fermionic dipolar ^{23}Na^{6}Li molecules in their triplet ground state from an ultracold mixture of ^{23}Na and ^{6}Li. Using magnetoassociation across a narrow Feshbach resonance followed by a two-photon stimulated Raman adiabatic passage to the triplet ground state, we produce 3×10^{4} ground state molecules in a spin-polarized state. We observe a lifetime of 4.6 s in an isolated molecular sample, approaching the p-wave universal rate limit. Electron spin resonance spectroscopy of the triplet state was used to determine the hyperfine structure of this previously unobserved molecular state.

Long-Lived Ultracold Molecules with Electric and Magnetic Dipole Moments

NASA Astrophysics Data System (ADS)

Rvachov, Timur M.; Son, Hyungmok; Sommer, Ariel T.; Ebadi, Sepehr; Park, Juliana J.; Zwierlein, Martin W.; Ketterle, Wolfgang; Jamison, Alan O.

2017-10-01

We create fermionic dipolar 23Na 6Li molecules in their triplet ground state from an ultracold mixture of 23Na and 6Li. Using magnetoassociation across a narrow Feshbach resonance followed by a two-photon stimulated Raman adiabatic passage to the triplet ground state, we produce 3 ×1 04 ground state molecules in a spin-polarized state. We observe a lifetime of 4.6 s in an isolated molecular sample, approaching the p -wave universal rate limit. Electron spin resonance spectroscopy of the triplet state was used to determine the hyperfine structure of this previously unobserved molecular state.

Spin disorder in maghemite nanoparticles investigated using polarized neutrons and nuclear resonant scattering

NASA Astrophysics Data System (ADS)

Herlitschke, M.; Disch, S.; Sergueev, I.; Schlage, K.; Wetterskog, E.; Bergström, L.; Hermann, R. P.

2016-04-01

The manuscript reports the investigation of spin disorder in maghemite nanoparticles of different shape by a combination of polarized small-angle neutron scattering (SANSPOL) and nuclear forward scattering (NFS) techniques. Both methods are sensitive to magnetization on the nanoscale. SANSPOL allows for investigation of the particle morphology and spatial magnetization distribution and NFS extends this nanoscale information to the atomic scale, namely the orientation of the hyperfine field experienced by the iron nuclei. The studied nanospheres and nanocubes with diameters of 7.4 nm and 10.6 nm, respectively, exhibit a significant spin disorder. This effect leads to a reduction of the magnetization to 44% and 58% of the theoretical maghemite bulk value, observed consistently by both techniques.

l-Tryptophan Radical Cation Electron Spin Resonance Studies: Connecting Solution-derived Hyperfine Coupling Constants with Protein Spectral Interpretations

PubMed Central

Connor, Henry D.; Sturgeon, Bradley E.; Mottley, Carolyn; Sipe, Herbert J.; Mason, Ronald P.

2009-01-01

Fast-flow electron spin resonance (ESR) spectroscopy has been used to detect a free radical formed from the reaction of l-tryptophan with Ce4+ in an acidic aqueous environment. Computer simulations of the ESR spectra from l-tryptophan and several isotopically modified forms strongly support the conclusion that the l-tryptophan radical cation has been detected by ESR for the first time. The hyperfine coupling constants (HFCs) determined from the well-resolved isotropic ESR spectra support experimental and computational efforts to understand l-tryptophan's role in protein catalysis of oxidation-reduction processes. l-tryptophan HFCs facilitated the simulation of fast-flow ESR spectra of free radicals from two related compounds, tryptamine and 3-methylindole. Analysis of these three compounds' β-methylene hydrogen HFC data along with equivalent l-tyrosine data has led to a new computational method that can distinguish between these two amino acid free radicals in proteins without dependence on isotope labeling, electron nuclear double resonance or high-field ESR. This approach also produces geometric parameters (dihedral angles for the β-methylene hydrogens) which should facilitate protein site assignment of observed l-tryptophan radicals as has been done for l-tyrosine radicals. PMID:18433127

Identification of the Ga interstitial in Al(x)Ga(1-x)As by optically detected magnetic resonance

NASA Technical Reports Server (NTRS)

Kennedy, T. A.; Spencer, M. G.

1986-01-01

A new optically detected magnetic resonance spectrum in Al(x)Ga(1-x)As is reported and assigned to native Ga interstitials. Luminescence-quenching signals were observed over the energy region from 0.75 to 1.1 eV. The optically detected magnetic resonance is nearly isotropic, with spin-Hamiltonian parameters g = 2.025 + or - 0.006, central hyperfine splitting A(Ga-69) = 0.050 + or - 0.001/cm, and A(Ga-71) = 0.064 + or - 0.001/cm for H near the 001 line. The strong hyperfine coupling denotes an electronic state of A1 symmetry, which current theories predict for the Ga interstitial but not the Ga antisite. The slight anisotropy probably indicates that the Ga(i) is paired with a second, unknown defect.

Theoretical study of spin Hall effect in conjugated Organic semiconductors

NASA Astrophysics Data System (ADS)

Mahani, M. R.; Delin, A.

The spin Hall effect (SHE), a direct conversion between electronic and spin currents, is a rapidly growing branch of spintronics. The study of SHE in conjugated polymers has gained momentum recently due to the weak spin-orbit couplings and hyperfine interactions in these materials. Our calculations of SHE based on the recent work, are the result of the misalignment of pi-orbitals in triads consisting of three molecules. In disordered organics, where the electronic conduction is through hopping of the electrons among randomly oriented molecules, instead of identifying a hopping triad to represent the entire system, we numerically solve the master equations for electrical and spin hall conductivities by summing the contributions from all triads in a sufficiently large system. The interference between the direct and indirect hoppings in these triads leads to SHE proportional to the orientation vector of molecule at the first order of spin-orbit coupling. Hence, our results show, the degree of molecular alignment as well as the strength of the spin-orbit coupling can be used to control the SHE in organics.

Effective field theories for muonic hydrogen

NASA Astrophysics Data System (ADS)

Peset, Clara

2017-03-01

Experimental measurements of muonic hydrogen bound states have recently started to take place and provide a powerful setting in which to study the properties of QCD. We profit from the power of effective field theories (EFTs) to provide a theoretical framework in which to study muonic hydrogen in a model independent fashion. In particular, we compute expressions for the Lamb shift and the hyperfine splitting. These expressions include the leading logarithmic O(mμα6) terms, as well as the leading {\\cal O}≤ft( {{m_μ }{α ^5}{{m_μ ^2} \\over {Λ {{QCD}}^2}}} \\right) hadronic effects. Most remarkably, our analyses include the determination of the spin-dependent and spin-independent structure functions of the forward virtualphoton Compton tensor of the proton to O(p3) in HBET and including the Delta particle. Using these results we obtain the leading hadronic contributions to the Wilson coeffcients of the lepton-proton four fermion operators in NRQED. The spin-independent coeffcient yields a pure prediction for the two-photon exchange contribution to the muonic hydrogen Lamb shift, which is the main source of uncertainty in our computation. The spindependent coeffcient yields the prediction of the hyperfine splitting. The use of EFTs crucially helps us organizing the computation, in such a way that we can clearly address the parametric accuracy of our result. Furthermore, we review in the context of NRQED all the contributions to the energy shift of O(mμα5, as well as those that scale like mrα6× logarithms.

Computational Studies of Magnetically Doped Semiconductor Nanoclusters

NASA Astrophysics Data System (ADS)

Gutsev, Lavrenty Gennady

Spin-polarized unrestricted density functional theory is used to calculate the molecular properties of magnetic semiconductor quantum dots doped with 3d-metal atoms. We calculate total energies of the low spin antiferromagnetically coupled states using a spin-flipping algorithm leading to the broken-symmetry states. Given the novel nature of the materials studied, we simulate experimental observables such as hyperfine couplings, ionization/ energies, electron affinities, first and second order polarizabilities, band gaps and exchange coupling constants. Specifically, we begin our investigation with pure clusters of (CdSe )16 and demonstrate the dependence of molecular observables on geometrical structures. We also show that the many isomers of this cluster are energetically quite closely spaced, and thus it would be necessary to employ a battery of tests to experimentally distinguish them. Next, we discuss Mn-doping into the cage (CdSe)9 cluster as well as the zinc-blende stacking type cluster (CdSe)36. We show that the local exchange coupling mechanism is ligand-mediated superexchange and simulate the isotropic hyperfine constants. Finally, we discuss a novel study where (CdSe)9 is doped with Mn or Fe up to a full replacement of all the Cd's and discuss the transition points for the magnetic behavior and specifically the greatly differing band-gap shifts. We also outline an unexpected pattern in the polarizability of the material as metals are added and compare our results with the results from theoretical studies of the bulk material.

Velocity modulation spectroscopy of molecular ions II: The millimeter/submillimeter-wave spectrum of TiF + ( X3Φr)

NASA Astrophysics Data System (ADS)

Halfen, D. T.; Ziurys, L. M.

2006-11-01

The pure rotational spectrum of the molecular ion TiF + in its 3Φr ground state has been measured in the range 327-542 GHz using millimeter-wave direct absorption techniques combined with velocity modulation spectroscopy. TiF + was made in an AC discharge from a mixture of TiCl 4, F 2 in He, and argon. Ten transitions of this ion were recorded. In every transition, fluorine hyperfine interactions, as well as the fine structure splittings, were resolved. The fine structure pattern was found to be regular with almost equal spacing in frequency between the three spin components, in contrast to TiCl +, which is perturbed in the ground state. The data were fit with a case ( a) Hamiltonian and rotational, fine structure, and hyperfine constants were determined. The bond length established for TiF +, r0 = 1.7775 Å, was found to be shorter than that of TiF, r0 = 1.8342 Å—also established from mm-wave data. The hyperfine parameters determined are consistent with a δ1π1 electron configuration with the electrons primarily located on the titanium nucleus. The nuclear spin-orbit constant a indicates that the unpaired electrons are closer to the fluorine nucleus in TiF + relative to TiF, as expected with the decrease in bond length for the ion. The shorter bond distance is thought to arise from increased charge on the titanium nucleus as a result of a Ti 2+F - configuration. A similar decrease in bond length was found for TiCl + relative to TiCl.

Anomalous behavior of the magnetic hyperfine field at 140Ce impurities at La sites in LaMnSi2

NASA Astrophysics Data System (ADS)

Domienikan, C.; Bosch-Santos, B.; Cabrera-Pasca, G. A.; Saxena, R. N.; Carbonari, A. W.

2018-05-01

Magnetic hyperfine field has been measured in the orthorhombic intermetallic compound LaMnSi2 with perturbed angular correlation (PAC) spectroscopy using radioactive 140La(140Ce) nuclear probes. Magnetization measurements were also carried out in this compound with MPSM-SQUID magnetometer. Samples of LaMnSi2 compound were prepared by arc melting the component metals with high purity under argon atmosphere followed by annealing at 1000°C for 60 h under helium atmosphere and quenching in water. X-ray analysis confirmed the samples to be in a single phase with correct crystal structure expected for LaMnSi2 compound. The radioactive 140La (T1/2 = 40 h) nuclei were produced by direct irradiation of the sample with neutrons in the IEA-R1 nuclear research reactor at IPEN with a flux of ˜ 1013 n cm-2s-1 for about 3 - 4 min. The PAC measurements were carried out with a six BaF2 detector spectrometer at several temperatures between 10 K and 400 K. Temperature dependence of the hyperfine field, Bhf was found to be anomalous. A modified two-state model explained this anomalous behavior where the effective magnetic hyperfine field at 140Ce is believed to have two contributions, one from the unstable localized spins at Ce impurities and another from the magnetic Mn atoms of the host. The competition of these two contributions explains the anomalous behavior observed for the temperature dependence of the magnetic hyperfine field at 140Ce. The ferromagnetic transition temperature (TC) of LaMnSi2 was determined to be 400(1) K confirming the magnetic measurements.

Gradient ascent pulse engineering approach to CNOT gates in donor electron spin quantum computing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, D.-B.; Goan, H.-S.

2008-11-07

In this paper, we demonstrate how gradient ascent pulse engineering (GRAPE) optimal control methods can be implemented on donor electron spin qubits in semiconductors with an architecture complementary to the original Kane's proposal. We focus on the high fidelity controlled-NOT (CNOT) gate and we explicitly find the digitized control sequences for a controlled-NOT gate by optimizing its fidelity using the effective, reduced donor electron spin Hamiltonian with external controls over the hyperfine A and exchange J interactions. We then simulate the CNOT-gate sequence with the full spin Hamiltonian and find that it has an error of 10{sup -6} that ismore » below the error threshold of 10{sup -4} required for fault-tolerant quantum computation. Also the CNOT gate operation time of 100 ns is 3 times faster than 297 ns of the proposed global control scheme.« less

Spin-Orbit Qubits of Rare-Earth-Metal Ions in Axially Symmetric Crystal Fields

NASA Astrophysics Data System (ADS)

Bertaina, S.; Shim, J. H.; Gambarelli, S.; Malkin, B. Z.; Barbara, B.

2009-11-01

Contrary to the well-known spin qubits, rare-earth-metal qubits are characterized by a strong influence of crystal field due to large spin-orbit coupling. At low temperature and in the presence of resonance microwaves, it is the magnetic moment of the crystal-field ground state which nutates (for several μs) and the Rabi frequency ΩR is anisotropic. Here, we present a study of the variations of ΩR(H→0) with the magnitude and direction of the static magnetic field H→0 for the odd Er167 isotope in a single crystal CaWO4:Er3+. The hyperfine interactions split the ΩR(H→0) curve into eight different curves which are fitted numerically and described analytically. These “spin-orbit qubits” should allow detailed studies of decoherence mechanisms which become relevant at high temperature and open new ways for qubit addressing using properly oriented magnetic fields.

Spin-orbit qubits of rare-earth-metal ions in axially symmetric crystal fields.

PubMed

Bertaina, S; Shim, J H; Gambarelli, S; Malkin, B Z; Barbara, B

2009-11-27

Contrary to the well-known spin qubits, rare-earth-metal qubits are characterized by a strong influence of crystal field due to large spin-orbit coupling. At low temperature and in the presence of resonance microwaves, it is the magnetic moment of the crystal-field ground state which nutates (for several micros) and the Rabi frequency Omega(R) is anisotropic. Here, we present a study of the variations of Omega(R)(H(0)) with the magnitude and direction of the static magnetic field H(0) for the odd 167Er isotope in a single crystal CaWO(4):Er(3+). The hyperfine interactions split the Omega(R)(H(0)) curve into eight different curves which are fitted numerically and described analytically. These "spin-orbit qubits" should allow detailed studies of decoherence mechanisms which become relevant at high temperature and open new ways for qubit addressing using properly oriented magnetic fields.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harvey-Collard, Patrick; Jacobson, N. Tobias; Rudolph, Martin

Individual donors in silicon chips are used as quantum bits with extremely low error rates. However, physical realizations have been limited to one donor because their atomic size causes fabrication challenges. Quantum dot qubits, in contrast, are highly adjustable using electrical gate voltages. This adjustability could be leveraged to deterministically couple donors to quantum dots in arrays of qubits. In this work, we demonstrate the coherent interaction of a 31P donor electron with the electron of a metal-oxide-semiconductor quantum dot. We form a logical qubit encoded in the spin singlet and triplet states of the two-electron system. We show thatmore » the donor nuclear spin drives coherent rotations between the electronic qubit states through the contact hyperfine interaction. This provides every key element for compact two-electron spin qubits requiring only a single dot and no additional magnetic field gradients, as well as a means to interact with the nuclear spin qubit.« less

Spin label studies of micellar and pre-micellar aggregates.

PubMed

Ernades, J R; Schreier, S; Chaimovich, H

1976-02-01

Micelles of hexadecyl trimethyl ammonium bromide (CTABr) have been investigated with the use of a faty acid spin label and its methyl ester derivative. The esr * spectra provided information about the degree of motion of the probes in the micelles as evaluated from calculation of rotational correlation times. Evidence is presented for the formation of pre-micellar aggregates at concentrations below the cmc. The effect of addition of thiophenoxide on the structure of CTABr micelles was to decrease the rate of motion of the spin probes, probably due to a tighter packing of the hydrophobic core as a consequence of charge neutralization at the micelle surface by the substrate. Decreasing values of the isotropic hyperfine splitting of the spin probe with increasing concentration of thiophenoxide were taken as indicating that the latter causes a decrease of the degree of hydration of the polar head region of the detergent.

Multinuclear Detection of Nuclear Spin Optical Rotation at Low Field.

PubMed

Zhu, Yue; Gao, Yuheng; Rodocker, Shane; Savukov, Igor; Hilty, Christian

2018-06-06

We describe the multinuclear detection of nuclear spin optical rotation (NSOR), an effect dependent on the hyperfine interaction between nuclear spins and electrons. Signals of 1 H and 19 F are discriminated by frequency in a single spectrum acquired at sub-millitesla field. The simultaneously acquired optical signal along with the nuclear magnetic resonance signal allows the calculation of the relative magnitude of the NSOR constants corresponding to different nuclei within the sample molecules. This is illustrated by a larger NSOR signal measured at the 19 F frequency despite a smaller corresponding spin concentration. Second, it is shown that heteronuclear J-coupling is observable in the NSOR signal, which can be used to retrieve chemical information. Multinuclear frequency and J resolution can localize optical signals in the molecule. Properties of electronic states at multiple sites in a molecule may therefore ultimately be determined by frequency-resolved NSOR spectroscopy at low field.

Iron spin transitions in the lower mantle

NASA Astrophysics Data System (ADS)

McCammon, C.; Dubrovinsky, L.; Potapkin, V.; Glazyrin, K.; Kantor, A.; Kupenko, I.; Prescher, C.; Sinmyo, R.; Smirnov, G.; Chumakov, A.; Rüffer, R.

2012-04-01

Iron has the ability to adopt different electronic configurations (spin states), which can significantly influence mantle properties and dynamics. It is now generally accepted as a result of studies over the past decade that ferrous iron in (Mg,Fe)O undergoes a high-spin to low-spin transition in the mid-part of the lower mantle; however results on (Mg,Fe)(Si,Al)O3 perovskite, the dominant phase of the lower mantle, remain controversial. Identifying spin transitions in (Mg,Fe)(Si,Al)O3 perovskite presents a significant challenge. X-ray emission spectroscopy provides information on the bulk spin number, but cannot separate individual contributions. Nuclear forward scattering measures hyperfine interactions, but is not well suited to complex materials due to the non-uniqueness of fitting models. Energy-domain Mössbauer spectroscopy generally enables an unambiguous resolution of all hyperfine parameters which can be used to infer spin states; however high pressure measurements using conventional radioactive point sources require extremely long counting times. To solve this problem, we have developed an energy-domain synchrotron Mössbauer source that enables rapid measurement of spectra under extreme conditions (both high pressure and high temperature) with a quality generally sufficient to unambiguously deconvolute even highly complex spectra. We have used the newly developed method to measure high quality Mössbauer spectra of different compositions of (Mg,Fe)O and (Mg,Fe)(Si,Al)O3 perovskite at pressures up to 122 GPa and temperatures up to 2400 K. Experiments were carried out at the European Synchrotron Radiation Facility on the nuclear resonance beamline ID18 equipped with a portable laser heating system for diamond anvil cells. Our results confirm previous observations for (Mg,Fe)O that show a broad spin crossover region at high pressures and high temperatures, and show unambiguously that ferric iron in (Mg,Fe)(Si,Al)O3 perovskite remains in the high-spin state at conditions throughout the lower mantle. Electrical conductivity data of (Mg,Fe)(Si,Al)O3 perovskite are known to show a drop in conductivity above 50 GPa, which combined with our new results suggests that the currently controversial high-pressure transition of ferrous iron is indeed due to a high-spin to intermediate-spin transition at conditions near the top of the lower mantle. Our current picture of iron in the lower mantle is therefore of a relatively homogeneous spin state in (Mg,Fe)(Si,Al)O3 perovskite throughout most of the lower mantle: intermediate-spin ferrous iron and high-spin ferric iron. Different spin states are expected in ferrous iron in (Mg,Fe)(Si,Al)O3 perovskite only at the very top of the lower mantle (high spin) and at the very bottom (low spin). There is a broad transition from high-spin to low-spin ferrous iron in (Mg,Fe)O in the mid part of the lower mantle. Implications of these results for mantle properties and dynamics will be presented.

Electron paramagnetic resonance and density-functional theory studies of Cu(II)-bis(oxamato) complexes.

PubMed

Bräuer, Björn; Weigend, Florian; Fittipaldi, Maria; Gatteschi, Dante; Reijerse, Edward J; Guerri, Annalisa; Ciattini, Samuele; Salvan, Georgeta; Rüffer, Tobias

2008-08-04

In this work we present the investigation of the influence of electronic and structural variations induced by varying the N,N'-bridge on the magnetic properties of Cu(II)- bis(oxamato) complexes. For this study the complexes [Cu(opba)] (2-) ( 1, opba = o-phenylene- bis(oxamato)), [Cu(nabo)] (2-) ( 2, nabo = 2,3-naphthalene- bis(oxamato)), [Cu(acbo)] (2-) ( 3, acbo = 2,3-anthrachinone- bis(oxamato)), [Cu(pba)] (2-) ( 4, pba = propylene- bis(oxamato)), [Cu(obbo)] (2-) ( 5, obbo = o-benzyl- bis(oxamato)), and [Cu(npbo)] (2-) ( 6, npbo = 1,8-naphthalene- bis(oxamato)), and the respective structurally isomorphic Ni(II) complexes ( 8- 13) have been prepared as ( (n)Bu 4N) (+) salts. The new complex ( (n)Bu 4N) 2[Cu(R-bnbo)].2H 2O ( 7, R-bnbo = (R)-1,1'-binaphthalene-2,2'- bis(oxamato)) was synthesized and is the first chiral complex in the series of Cu(II)-bis(oxamato) complexes. The molecular structure of 7 has been determined by single crystal X-ray analysis. The Cu(II) ions of the complexes 1- 7 are eta (4)(kappa (2) N, kappa (2) O) coordinated with a more or less distorted square planar geometry for 1- 6 and a distorted tetrahedral geometry for 7. Using pulsed Electron Nuclear Double Resonance on complex 6, detailed information about the relative orientation of the hyperfine ( A) and nuclear quadrupole tensors ( Q) of the coordinating nitrogens with respect to the g tensor were obtained. Electron Paramagnetic Resonance studies in the X, Q, and W-band at variable temperatures were carried out to extract g and A values of N ligands and Cu ion for 1- 7. The hyperfine values were interpreted in terms of spin population on the corresponding atoms. The obtained trends of the spin population for the monomeric building blocks were shown to correlate to the trends obtained in the dependence of the exchange interaction of the corresponding trinuclear complexes on their geometry.

Multi-resonance frequency spin dependent charge pumping and spin dependent recombination - applied to the 4H-SiC/SiO2 interface

NASA Astrophysics Data System (ADS)

Anders, M. A.; Lenahan, P. M.; Lelis, A. J.

2017-12-01

We report on a new electrically detected magnetic resonance (EDMR) approach involving spin dependent charge pumping (SDCP) and spin dependent recombination (SDR) at high (K band, about 16 GHz) and ultra-low (360 and 85 MHz) magnetic resonance frequencies to investigate the dielectric/semiconductor interface in 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFETs). A comparison of SDCP and SDR allows for a comparison of deep level defects and defects with energy levels throughout most of the bandgap. Additionally, a comparison of high frequency and ultra-low frequency measurements allows for (1) the partial separation of spin-orbit coupling and hyperfine effects on magnetic resonance spectra, (2) the observation of otherwise forbidden half-field effects, which make EDMR, at least, in principle, quantitative, and (3) the observation of Breit-Rabi shifts in superhyperfine measurements. (Observation of the Breit-Rabi shift helps in both the assignment and the measurement of superhyperfine parameters.) We find that, as earlier work also indicates, the SiC silicon vacancy is the dominating defect in n-MOSFETs with as-grown oxides and that post-oxidation NO anneals significantly reduce their population. In addition, we provide strong evidence that NO anneals result in the presence of nitrogen very close to a large fraction of the silicon vacancies. The results indicate that the presence of nearby nitrogen significantly shifts the silicon vacancy energy levels. Our results also show that the introduction of nitrogen introduces a disorder at the interface. This nitrogen induced disorder may provide at least a partial explanation for the relatively modest improvement in mobility after the NO anneals. Finally, we compare the charge pumping and SDCP response as a function of gate amplitude and charge pumping frequency.

NMR studies of electronic structure in crystalline and amorphous Zr2PdH/x/

NASA Technical Reports Server (NTRS)

Bowman, R. C., Jr.; Johnson, W. L.; Maeland, A. J.; Rhim, W.-K.

1983-01-01

The proton Knight shifts and spin-lattice relaxation times have been measured in crystalline and amorphous Ze2PdH(x). Core polarization from the Zr d-band dominates the proton hyperfine interactions. The density of Fermi level d-electron states is reduced in the amorphous phase relative to the electron density in crystalline Zr2PdH(x).

Characterization of Water Coordination to Ferrous Nitrosyl Complexes with fac-N2O, cis-N2O2, and N2O3 Donor Ligands.

PubMed

McCracken, John; Cappillino, Patrick J; McNally, Joshua S; Krzyaniak, Matthew D; Howart, Michael; Tarves, Paul C; Caradonna, John P

2015-07-06

Electron paramagnetic resonance (EPR) experiments were done on a series of S = (3)/2 ferrous nitrosyl model complexes prepared with chelating ligands that mimic the 2-His-1-carboxylate facial triad iron binding motif of the mononuclear nonheme iron oxidases. These complexes formed a comparative family, {FeNO}(7)(N2Ox)(H2O)3-x with x = 1-3, where the labile coordination sites for the binding of NO and solvent water were fac for x = 1 and cis for x = 2. The continuous-wave EPR spectra of these three complexes were typical of high-spin S = (3)/2 transition-metal ions with resonances near g = 4 and 2. Orientation-selective hyperfine sublevel correlation (HYSCORE) spectra revealed cross peaks arising from the protons of coordinated water in a clean spectral window from g = 3.0 to 2.3. These cross peaks were absent for the {FeNO}(7)(N2O3) complex. HYSCORE spectra were analyzed using a straightforward model for defining the spin Hamiltonian parameters of bound water and showed that, for the {FeNO}(7)(N2O2)(H2O) complex, a single water conformer with an isotropic hyperfine coupling, Aiso = 0.0 ± 0.3 MHz, and a dipolar coupling of T = 4.8 ± 0.2 MHz could account for the data. For the {FeNO}(7)(N2O)(H2O)2 complex, the HYSCORE cross peaks assigned to coordinated water showed more frequency dispersion and were analyzed with discrete orientations and hyperfine couplings for the two water molecules that accounted for the observed orientation-selective contour shapes. The use of three-pulse electron spin echo envelope modulation (ESEEM) data to quantify the number of water ligands coordinated to the {FeNO}(7) centers was explored. For this aspect of the study, HYSCORE spectra were important for defining a spectral window where empirical integration of ESEEM spectra would be the most accurate.

Quantitative analysis of dinuclear manganese(II) EPR spectra

NASA Astrophysics Data System (ADS)

Golombek, Adina P.; Hendrich, Michael P.

2003-11-01

A quantitative method for the analysis of EPR spectra from dinuclear Mn(II) complexes is presented. The complex [(Me 3TACN) 2Mn(II) 2(μ-OAc) 3]BPh 4 ( 1) (Me 3TACN= N, N', N''-trimethyl-1,4,7-triazacyclononane; OAc=acetate 1-; BPh 4=tetraphenylborate 1-) was studied with EPR spectroscopy at X- and Q-band frequencies, for both perpendicular and parallel polarizations of the microwave field, and with variable temperature (2-50 K). Complex 1 is an antiferromagnetically coupled dimer which shows signals from all excited spin manifolds, S=1 to 5. The spectra were simulated with diagonalization of the full spin Hamiltonian which includes the Zeeman and zero-field splittings of the individual manganese sites within the dimer, the exchange and dipolar coupling between the two manganese sites of the dimer, and the nuclear hyperfine coupling for each manganese ion. All possible transitions for all spin manifolds were simulated, with the intensities determined from the calculated probability of each transition. In addition, the non-uniform broadening of all resonances was quantitatively predicted using a lineshape model based on D- and r-strain. As the temperature is increased from 2 K, an 11-line hyperfine pattern characteristic of dinuclear Mn(II) is first observed from the S=3 manifold. D- and r-strain are the dominate broadening effects that determine where the hyperfine pattern will be resolved. A single unique parameter set was found to simulate all spectra arising for all temperatures, microwave frequencies, and microwave modes. The simulations are quantitative, allowing for the first time the determination of species concentrations directly from EPR spectra. Thus, this work describes the first method for the quantitative characterization of EPR spectra of dinuclear manganese centers in model complexes and proteins. The exchange coupling parameter J for complex 1 was determined ( J=-1.5±0.3 cm-1; H ex=-2J S1· S2) and found to be in agreement with a previous determination from magnetization. The phenomenon of exchange striction was found to be insignificant for 1.

Influence of Molecular Oxygen on Ortho-Para Conversion of Water Molecules

NASA Astrophysics Data System (ADS)

Valiev, R. R.; Minaev, B. F.

2017-07-01

The mechanism of influence of molecular oxygen on the probability of ortho-para conversion of water molecules and its relation to water magnetization are considered within the framework of the concept of paramagnetic spin catalysis. Matrix elements of the hyperfine ortho-para interaction via the Fermi contact mechanism are calculated, as well as the Maliken spin densities on water protons in H2O and O2 collisional complexes. The mechanism of penetration of the electron spin density into the water molecule due to partial spin transfer from paramagnetic oxygen is considered. The probability of ortho-para conversion of the water molecules is estimated by the quantum chemistry methods. The results obtained show that effective ortho-para conversion of the water molecules is possible during the existence of water-oxygen dimers. An external magnetic field affects the ortho-para conversion rate given that the wave functions of nuclear spin sublevels of the water protons are mixed in the complex with oxygen.

Quarkonium h states as arbiters of exoticity

NASA Astrophysics Data System (ADS)

Lebed, Richard F.; Swanson, Eric S.

2017-09-01

The mass splitting between the quarkonium spin-singlet state h (JP C=1+-) and the spin average of the quarkonium spin-triplet states χ (JP C=0++,1++,2++) is seen to be astonishingly small, not only in the charmonium and bottomonium cases where the relevant masses have been measured, but in positronium as well. We find, both in nonrelativistic quark models and in nonrelativistic quantum chromodynamics (NRQCD), that this hyperfine splitting is so small that it can be used as a test of the pure Q Q ¯ content of the states. We discuss the 2 P states of charmonium in the vicinity of 3.9 GeV, where the putative exotics X (3872 ) and X (3915 ) have been seen and a new χc 0(2 P ) candidate has been observed at Belle.

Spin disorder in maghemite nanoparticles investigated using polarized neutrons and nuclear resonant scattering

DOE PAGES

Herlitschke, Marcus; Disch, Sabrina; Sergueev, I.; ...

2016-05-11

The manuscript reports the investigation of spin disorder in maghemite nanoparticles of different shape by a combination of polarized small-angle neutron scattering (SANSPOL) and nuclear forward scattering (NFS) techniques. Both methods are sensitive to magnetization on the nanoscale. SANSPOL allows for investigation of the particle morphology and spatial magnetization distribution and NFS extends this nanoscale information to the atomic scale, namely the orientation of the hyperfine field experienced by the iron nuclei. The studied nanospheres and nanocubes with diameters of 7.4nm and 10.6 nm, respectively, exhibit a significant spin disorder. This effect leads to a reduction of the magnetization tomore » 44% and 58% of the theoretical maghemite bulk value, observed consistently by both techniques.« less

Spin disorder in maghemite nanoparticles investigated using polarized neutrons and nuclear resonant scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Herlitschke, Marcus; Disch, Sabrina; Sergueev, I.

The manuscript reports the investigation of spin disorder in maghemite nanoparticles of different shape by a combination of polarized small-angle neutron scattering (SANSPOL) and nuclear forward scattering (NFS) techniques. Both methods are sensitive to magnetization on the nanoscale. SANSPOL allows for investigation of the particle morphology and spatial magnetization distribution and NFS extends this nanoscale information to the atomic scale, namely the orientation of the hyperfine field experienced by the iron nuclei. The studied nanospheres and nanocubes with diameters of 7.4nm and 10.6 nm, respectively, exhibit a significant spin disorder. This effect leads to a reduction of the magnetization tomore » 44% and 58% of the theoretical maghemite bulk value, observed consistently by both techniques.« less

Theoretical study of triplet state properties of free-base porphin

NASA Astrophysics Data System (ADS)

Loboda, Oleksandr; Tunell, Ingvar; Minaev, Boris; Ågren, Hans

2005-06-01

This paper presents results and analysis of various properties of the triplet state of free-base porphin (FBP) as calculated by density-functional theory. The radiative lifetime of phosphorescence lines and microwave signals in optical detection of magnetic resonance (ODMR) spectra are obtained using the B3LYP hybrid density-functional and the quadratic response method. The zero-field splitting (ZFS) in the lowest triplet state, a3 B2u, of FBP is calculated as an expectation value of spin-spin coupling operator using the self-consistent field wavefunction. The second-order contribution to ZFS from the spin-orbit coupling operator is found to be almost negligible. The interpretation of the ODMR spectrum is completed by computing the hyperfine tensors of the 14N, 13C and hydrogen atoms in the lowest triplet state. The most intense phosphorescence emission corresponds to the Tz-spin-sublevel of the a3 B2u state, where the z-axis lies in the N-H direction of the FBP molecule in a qualitative agreement with ODMR data. The results indicate that the observed decay of the lowest triplet state of FBP molecule is determined by non-radiative deactivation. The calculated radiative rate constant for the Tz-spin-sublevel kz = 2.65 × 10-3 s-1 is in agreement with the value kz ≃ 2 × 10-3 s-1, estimated by van Dorp et al. [W. van Dorp, W. Schoemaker, M. Soma, J. van der Waals, Mol. Phys. 30 (1975) 1701] from kinetic analysis of microwave-induced fluorescent signals. The correct prediction of the spin quantization axis of the most active spin sublevel and of its radiative lifetime in the lowest triplet state of the FBP molecule is taken as a proof of capability of the quadratic response time-dependent density-functional theory.

Analysis of the transient response of nuclear spins in GaAs with/without nuclear magnetic resonance

NASA Astrophysics Data System (ADS)

Rasly, Mahmoud; Lin, Zhichao; Yamamoto, Masafumi; Uemura, Tetsuya

2016-05-01

As an alternative to studying the steady-state responses of nuclear spins in solid state systems, working within a transient-state framework can reveal interesting phenomena. The response of nuclear spins in GaAs to a changing magnetic field was analyzed based on the time evolution of nuclear spin temperature. Simulation results well reproduced our experimental results for the transient oblique Hanle signals observed in an all-electrical spin injection device. The analysis showed that the so called dynamic nuclear polarization can be treated as a cooling tool for the nuclear spins: It works as a provider to exchange spin angular momentum between polarized electron spins and nuclear spins through the hyperfine interaction, leading to an increase in the nuclear polarization. In addition, a time-delay of the nuclear spin temperature with a fast sweep of the external magnetic field produces a possible transient state for the nuclear spin polarization. On the other hand, the nuclear magnetic resonance acts as a heating tool for a nuclear spin system. This causes the nuclear spin temperature to jump to infinity: i.e., the average nuclear spins along with the nuclear field vanish at resonant fields of 75As, 69Ga and 71Ga, showing an interesting step-dip structure in the oblique Hanle signals. These analyses provide a quantitative understanding of nuclear spin dynamics in semiconductors for application in future computation processing.

Copper ESEEM and HYSCORE through ultra-wideband chirp EPR spectroscopy.

PubMed

Segawa, Takuya F; Doll, Andrin; Pribitzer, Stephan; Jeschke, Gunnar

2015-07-28

The main limitation of pulse electron paramagnetic resonance (EPR) spectroscopy is its narrow excitation bandwidth. Ultra-wideband (UWB) excitation with frequency-swept chirp pulses over several hundreds of megahertz overcomes this drawback. This allows to excite electron spin echo envelope modulation (ESEEM) from paramagnetic copper centers in crystals, whereas up to now, only ESEEM of ligand nuclei like protons or nitrogens at lower frequencies could be detected. ESEEM spectra are recorded as two-dimensional correlation experiments, since the full digitization of the electron spin echo provides an additional Fourier transform EPR dimension. Thus, UWB hyperfine-sublevel correlation experiments generate a novel three-dimensional EPR-correlated nuclear modulation spectrum.

Coherent Control of Ground State NaK Molecules

NASA Astrophysics Data System (ADS)

Yan, Zoe; Park, Jee Woo; Loh, Huanqian; Will, Sebastian; Zwierlein, Martin

2016-05-01

Ultracold dipolar molecules exhibit anisotropic, tunable, long-range interactions, making them attractive for the study of novel states of matter and quantum information processing. We demonstrate the creation and control of 23 Na40 K molecules in their rovibronic and hyperfine ground state. By applying microwaves, we drive coherent Rabi oscillations of spin-polarized molecules between the rotational ground state (J=0) and J=1. The control afforded by microwave manipulation allows us to pursue engineered dipolar interactions via microwave dressing. By driving a two-photon transition, we are also able to observe Ramsey fringes between different J=0 hyperfine states, with coherence times as long as 0.5s. The realization of long coherence times between different molecular states is crucial for applications in quantum information processing. NSF, AFOSR- MURI, Alfred P. Sloan Foundation, DARPA-OLE

Low-temperature electron-spin relaxation in the crystalline and glassy states of solid ethanol

NASA Astrophysics Data System (ADS)

Kveder, Marina; Merunka, Dalibor; Jokić, Milan; Rakvin, Boris

2008-03-01

X -band electron paramagnetic resonance spectroscopy was used to study the spectral properties of a nitroxide spin probe in ethanol glass and crystalline ethanol, at 5-11.5K . The different anisotropy of molecular packing in the two host matrices was evidenced by different rigid limit values for maximal hyperfine splitting in the signal of the spin probe. The significantly shorter phase memory time Tm for the spin probe dissolved in crystalline ethanol, as compared to ethanol glass, was discussed in terms of contribution from spectral diffusion. The effect of low-frequency dynamics was manifested in the temperature dependence of Tm and in the difference between the data measured at different spectral positions. This phenomenon was addressed within the framework of the slow-motional isotropic diffusion model [S. Lee and S. Z. Tang, Phys. Rev. B 31, 1308 (1985)] predicting the spin probe dynamics within the millisecond range, at very low temperatures. The shorter spin-lattice relaxation time of the spin probe in ethanol glass was interpreted in terms of enhanced energy exchange between the spin system and the lattice in the glass matrix due to boson peak excitations.

Curvature-enhanced Spin-orbit Coupling and Spinterface Effect in Fullerene-based Spin Valves

PubMed Central

Liang, Shiheng; Geng, Rugang; Yang, Baishun; Zhao, Wenbo; Chandra Subedi, Ram; Li, Xiaoguang; Han, Xiufeng; Nguyen, Tho Duc

2016-01-01

We investigated curvature-enhanced spin-orbit coupling (SOC) and spinterface effect in carbon-based organic spin valves (OSVs) using buckyball C60 and C70 molecules. Since the naturally abundant 12C has spinless nuclear, the materials have negligible hyperfine interaction (HFI) and the same intrinsic SOC, but different curvature SOC due to their distinct curvatures. We fitted the thickness dependence of magnetoresistance (MR) in OSVs at various temperatures using the modified Jullière equation. We found that the spin diffusion length in the C70 film is above 120 nm, clearly longer than that in C60 film at all temperatures. The effective SOC ratio of the C70 film to the C60 film was estimated to be about 0.8. This was confirmed by the magneto-electroluminescence (MEL) measurement in fullerene-based light emitting diodes (LED). Next, the effective spin polarization in C70-based OSVs is smaller than that in C60-based OSVs implying that they have different spinterface effect. First principle calculation study shows that the spin polarization of the dz2 orbital electrons of Co atoms contacted with C60 is larger causing better effective spin polarization at the interface. PMID:26786047

Curvature-enhanced Spin-orbit Coupling and Spinterface Effect in Fullerene-based Spin Valves

NASA Astrophysics Data System (ADS)

Liang, Shiheng; Geng, Rugang; Yang, Baishun; Zhao, Wenbo; Chandra Subedi, Ram; Li, Xiaoguang; Han, Xiufeng; Nguyen, Tho Duc

2016-01-01

We investigated curvature-enhanced spin-orbit coupling (SOC) and spinterface effect in carbon-based organic spin valves (OSVs) using buckyball C60 and C70 molecules. Since the naturally abundant 12C has spinless nuclear, the materials have negligible hyperfine interaction (HFI) and the same intrinsic SOC, but different curvature SOC due to their distinct curvatures. We fitted the thickness dependence of magnetoresistance (MR) in OSVs at various temperatures using the modified Jullière equation. We found that the spin diffusion length in the C70 film is above 120 nm, clearly longer than that in C60 film at all temperatures. The effective SOC ratio of the C70 film to the C60 film was estimated to be about 0.8. This was confirmed by the magneto-electroluminescence (MEL) measurement in fullerene-based light emitting diodes (LED). Next, the effective spin polarization in C70-based OSVs is smaller than that in C60-based OSVs implying that they have different spinterface effect. First principle calculation study shows that the spin polarization of the dz2 orbital electrons of Co atoms contacted with C60 is larger causing better effective spin polarization at the interface.

Verdazyl-ribose: A new radical for solid-state dynamic nuclear polarization at high magnetic field.

PubMed

Thurber, Kent R; Le, Thanh-Ngoc; Changcoco, Victor; Brook, David J R

2018-04-01

Solid-state dynamic nuclear polarization (DNP) using the cross-effect relies on radical pairs whose electron spin resonance (ESR) frequencies differ by the nuclear magnetic resonance (NMR) frequency. We measure the DNP provided by a new water-soluble verdazyl radical, verdazyl-ribose, under both magic-angle spinning (MAS) and static sample conditions at 9.4 T, and compare it to a nitroxide radical, 4-hydroxy-TEMPO. We find that verdazyl-ribose is an effective radical for cross-effect DNP, with the best relative results for a non-spinning sample. Under non-spinning conditions, verdazyl-ribose provides roughly 2× larger 13 C cross-polarized (CP) NMR signal than the nitroxide, with similar polarization buildup times, at both 29 K and 76 K. With MAS at 7 kHz and 1.5 W microwave power, the verdazyl-ribose does not provide as much DNP as the nitroxide, with the verdazyl providing less NMR signal and a longer polarization buildup time. When the microwave power is decreased to 30 mW with 5 kHz MAS, the two types of radical are comparable, with the verdazyl-doped sample having a larger NMR signal which compensates for its longer polarization buildup time. We also present electron spin relaxation measurements at Q-band (1.2 T) and ESR lineshapes at 1.2 and 9.4 T. Most notably, the verdazyl radical has a longer T 1e than the nitroxide (9.9 ms and 1.3 ms, respectively, at 50 K and 1.2 T). The verdazyl electron spin lineshape is significantly affected by the hyperfine coupling to four 14 N nuclei, even at 9.4 T. We also describe 3000-spin calculations to illustrate the DNP potential of possible radical pairs: verdazyl-verdazyl, verdazyl-nitroxide, or nitroxide-nitroxide pairs. These calculations suggest that the verdazyl radical at 9.4 T has a narrower linewidth than optimal for cross-effect DNP using verdazyl-verdazyl pairs. Because of the hyperfine coupling contribution to the electron spin linewidth, this implies that DNP using the verdazyl radical would improve at lower magnetic field. Another conclusion from the calculations is that a verdazyl-nitroxide bi-radical would be expected to be slightly better for cross-effect DNP than the nitroxide-nitroxide bi-radicals commonly used now, assuming the same spin-spin coupling constants. Published by Elsevier Inc.

Nuclear Spin Locking and Extended Two-Electron Spin Decoherence Time in an InAs Quantum Dot Molecule

NASA Astrophysics Data System (ADS)

Chow, Colin; Ross, Aaron; Steel, Duncan; Sham, L. J.; Bracker, Allan; Gammon, Daniel

2015-03-01

The spin eigenstates for two electrons confined in a self-assembled InAs quantum dot molecule (QDM) consist of the spin singlet state, S, with J = 0 and the triplet states T-, T0 and T+, with J = 1. When a transverse magnetic field (Voigt geometry) is applied, the two-electron system can be initialized to the different states with appropriate laser excitation. Under the excitation of a weak probe laser, non-Lorentzian lineshapes are obtained when the system is initialized to either T- or T+, where T- results in a ``resonance locking'' lineshape while T+ gives a ``resonance avoiding '' lineshape: two different manifestations of hysteresis showing the importance of memory in the system. These observations signify dynamic nuclear spin polarization (DNSP) arising from a feedback mechanism involving hyperfine interaction between lattice nuclei and delocalized electron spins, and Overhauser shift due to nuclear spin polarization. Using pump configurations that generate coherent population trapping, the isolation of the electron spin from the optical excitation shows the stabilization of the nuclear spin ensemble. The dark-state lineshape measures the lengthened electron spin decoherence time, from 1 ns to 1 μs. Our detailed spectra highlight the potential of QDM for realizing a two-qubit gate. This work is supported by NSF, ARO, AFOSR, DARPA, and ONR.

Hyperfine structure investigations for the odd-parity configuration system in atomic holmium

NASA Astrophysics Data System (ADS)

Stefanska, D.; Furmann, B.

2018-02-01

In this work new experimental results of the hyperfine structure (hfs) in the holmium atom are reported, concerning the odd-parity level system. Investigations were performed by the method of laser induced fluorescence in a hollow cathode discharge lamp on 97 spectral lines in the visible part of the spectrum. Hyperfine structure constants: magnetic dipole - A and electric quadrupole - B for 40 levels were determined for the first time; for another 21 levels the hfs constants available in the literature were remeasured. Results for the A constants can be viewed as fully reliable; for B constants further possibilities of improving the accuracy are considered.

Hyperfine quenching of the 2s2 2p5 3 s3P2 state of Ne-like ions

NASA Astrophysics Data System (ADS)

Safronova, U. I.; Stafford, A.; Safronova, A. S.

2017-04-01

The many-body perturbation theory (RMBPT) is used to calculate energies and multipole matrix elements to evaluate hyperfine quenching of the 2s2 2p5 3 s 3P2 state in Ne-like ions. In particular, the 3P2 excited state decays to the 1S0 ground state by M2 emission, while both 1P1 and 3P1 states decay to the ground-state by E1 emission, which is substantially faster. For odd-A nuclei, the hyperfine interaction induces admixtures of 3P1 and 1P1 states into the 3P2 state, resulting in an increase of the 3P2 transition rate and a corresponding reduction of the 3P2 lifetime. We consider 22 Ne like ions with Z = 14 - 94 and nuclear moment I =1/2. We found that the largess hyperfine quenching contribution by a factor of 2 are for Ne-like 31P and 203Tl. The smallest (less than 1%) induced contribution are the following Ne-like ions: 57Fe, 107Ag, 109Ag, 183W, and 187Os ions. For another 15 Ne-like ions the hyperfine quenching contribution is between 15% and 35%. Applications to x-ray line polarization of Ne-like lines is considered. This work is supported by the Department of Energy, National Nuclear Security Administration, under Award Number DE-NA0002954.

Bandwidth-limited control and ringdown suppression in high-Q resonators.

PubMed

Borneman, Troy W; Cory, David G

2012-12-01

We describe how the transient behavior of a tuned and matched resonator circuit and a ringdown suppression pulse may be integrated into an optimal control theory (OCT) pulse-design algorithm to derive control sequences with limited ringdown that perform a desired quantum operation in the presence of resonator distortions of the ideal waveform. Inclusion of ringdown suppression in numerical pulse optimizations significantly reduces spectrometer deadtime when using high quality factor (high-Q) resonators, leading to increased signal-to-noise ratio (SNR) and sensitivity of inductive measurements. To demonstrate the method, we experimentally measure the free-induction decay of an inhomogeneously broadened solid-state free radical spin system at high Q. The measurement is enabled by using a numerically optimized bandwidth-limited OCT pulse, including ringdown suppression, robust to variations in static and microwave field strengths. We also discuss the applications of pulse design in high-Q resonators to universal control of anisotropic-hyperfine coupled electron-nuclear spin systems via electron-only modulation even when the bandwidth of the resonator is significantly smaller than the hyperfine coupling strength. These results demonstrate how limitations imposed by linear response theory may be vastly exceeded when using a sufficiently accurate system model to optimize pulses of high complexity. Copyright © 2012 Elsevier Inc. All rights reserved.

Pulsed EPR investigations of systems modeling molybdenum enzymes: hyperfine and quadrupole parameters of oxo-17O in [Mo 17O(SPh)4]-.

PubMed

Astashkin, Andrei V; Neese, Frank; Raitsimring, Arnold M; Cooney, J Jon A; Bultman, Eric; Enemark, John H

2005-11-30

Ka band ESEEM spectroscopy was used to determine the hyperfine (hfi) and nuclear quadrupole (nqi) interaction parameters for the oxo-17O ligand in [Mo 17O(SPh)4]-, a spectroscopic model of the oxo-Mo(V) centers of enzymes. The isotropic hfi constant of 6.5 MHz found for the oxo-17O is much smaller than the values of approximately 20-40 MHz typical for the 17O nucleus of an equatorial OH(2) ligand in molybdenum enzymes. The 17O nqi parameter (e2qQ/h = 1.45 MHz, eta approximately = 0) is the first to be obtained for an oxo group in a metal complex. The parameters of the oxo-17O ligand, as well as other magnetic resonance parameters of [Mo 17O(SPh)4]- predicted by quasi-relativistic DFT calculations, were in good agreement with those obtained in experiment. From the electronic structure of the complex revealed by DFT, it follows that the SOMO is almost entirely molybdenum d(xy) and sulfur p, while the spin density on the oxo-17O is negative, determined by spin polarization mechanisms. The results of this work will enable direct experimental identification of the oxo ligand in a variety of chemical and biological systems.

Manipulation of the electroluminescence of organic light-emitting diodes via fringe fields from patterned magnetic domains

NASA Astrophysics Data System (ADS)

Harmon, N. J.; Wohlgenannt, M.; Flatté, M. E.

2016-12-01

We predict very large changes in the room-temperature electroluminescence of thermally-activated delayed fluorescence organic light emitting diodes near patterned ferromagnetic films. These effects exceed the changes in a uniform magnetic field by as much as a factor of two. We describe optimal ferromagnetic film patterns for enhancing the electroluminescence. A full theory of the spin-mixing processes in exciplex recombination and how they are affected by hyperfine fields, spin-orbit effects, and ferromagnetic fringe field effects is introduced. These spin-mixing processes are used to describe the effect of magnetic domain structures on the luminescence in various regimes. This provides a method of enhancing light emission rates from exciplexes and also a means of efficiently coupling information encoded in the magnetic domains to organic light emitting diode emission.

Manipulation of the electroluminescence of organic light-emitting diodes via fringe fields from patterned magnetic domains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harmon, N. J.; Wohlgenannt, M.; Flatté, M. E.

We predict very large changes in the room-temperature electroluminescence of thermally-activated delayed fluorescence organic light emitting diodes near patterned ferromagnetic films. These effects exceed the changes in a uniform magnetic field by as much as a factor of two. We describe optimal ferromagnetic film patterns for enhancing the electroluminescence. A full theory of the spin-mixing processes in exciplex recombination and how they are affected by hyperfine fields, spin-orbit effects, and ferromagnetic fringe field effects is introduced. These spin-mixing processes are used to describe the effect of magnetic domain structures on the luminescence in various regimes. This provides a method ofmore » enhancing light emission rates from exciplexes and also a means of efficiently coupling information encoded in the magnetic domains to organic light emitting diode emission« less

The microwave spectrum of a triplet carbene: HCCN in the X 3Sigma - state

NASA Astrophysics Data System (ADS)

Saito, Shuji; Endo, Yasuki; Hirota, Eizi

1984-02-01

A simple carbene, the HCCN radical, has been identified in the gas phase using a microwave spectroscopic method. The HCCN molecule was generated in a free space absorption cell by the reaction of CH3CN with the microwave discharge products of CF4. Five rotational transitions, each split into three fine structure components, were observed in the region of 110 to 198 GHz. No hyperfine structure was resolved, although some of the observed lines showed broadening. The rotational constant, the centrifugal distortion constant, the spin-spin coupling constant, and the spin-rotation coupling constant were determined with good precision. The observed spectrum is completely consistent with that expected for a linear molecule in a 3Σ state, in agreement with an earlier matrix EPR study of Bernheim et al. [J. Chem. Phys. 43, 196 (1965)].

Nuclear Spin relaxation mediated by Fermi-edge electrons in n-type GaAs

NASA Astrophysics Data System (ADS)

Kotur, M.; Dzhioev, R. I.; Kavokin, K. V.; Korenev, V. L.; Namozov, B. R.; Pak, P. E.; Kusrayev, Yu. G.

2014-03-01

A method based on the optical orientation technique was developed to measure the nuclear-spin lattice relaxation time T 1 in semiconductors. It was applied to bulk n-type GaAs, where T 1 was measured after switching off the optical excitation in magnetic fields from 400 to 1200 G at low (< 30 K) temperatures. The spin-lattice relaxation of nuclei in the studied sample with n D = 9 × 1016 cm-3 was found to be determined by hyperfine scattering of itinerant electrons (Korringa mechanism) which predicts invariability of T 1 with the change in magnetic field and linear dependence of the relaxation rate on temperature. This result extends the experimentally verified applicability of the Korringa relaxation law in degenerate semiconductors, previously studied in strong magnetic fields (several Tesla), to the moderate field range.

Manipulation of the electroluminescence of organic light-emitting diodes via fringe fields from patterned magnetic domains

DOE PAGES

Harmon, N. J.; Wohlgenannt, M.; Flatté, M. E.

2016-12-12

We predict very large changes in the room-temperature electroluminescence of thermally-activated delayed fluorescence organic light emitting diodes near patterned ferromagnetic films. These effects exceed the changes in a uniform magnetic field by as much as a factor of two. We describe optimal ferromagnetic film patterns for enhancing the electroluminescence. A full theory of the spin-mixing processes in exciplex recombination and how they are affected by hyperfine fields, spin-orbit effects, and ferromagnetic fringe field effects is introduced. These spin-mixing processes are used to describe the effect of magnetic domain structures on the luminescence in various regimes. This provides a method ofmore » enhancing light emission rates from exciplexes and also a means of efficiently coupling information encoded in the magnetic domains to organic light emitting diode emission« less

The rotational spectrum of the CH radical in its a 4Sigma(-) state, studied by far-infrared laser magnetic resonance

NASA Technical Reports Server (NTRS)

Nelis, Thomas; Brown, John M.; Evenson, Kenneth M.

1990-01-01

The CH radical has been detected in its a 4Sigma(-) state by the technique of laser magnetic resonance at far-infrared wavelengths. Spectra relating to different spin components of the first three rotational transitions have been recorded. The molecule was generated either by the reaction of F atoms with CH4, with a trace of added oxygen or by the reaction of O atoms with C2H2. The observed resonances have been analyzed and fitted to determine the parameters of an effective Hamiltonian for a molecule in a 4Sigma state. The principal quantities determined are the rotational constant B0 = 451 138.434(94) MHz and the spin-spin parameter lambda(0) = 2785.83(18) MHz. Proton hyperfine parameters have also been determined.

High-spin Fe2+ and Fe3+ in single-crystal aluminous bridgmanite in the lower mantle

NASA Astrophysics Data System (ADS)

Lin, Jung-Fu; Mao, Zhu; Yang, Jing; Liu, Jin; Xiao, Yuming; Chow, Paul; Okuchi, Takuo

2016-07-01

Spin and valence states of iron in single-crystal bridgmanite (Mg0.89Fe0.12Al0.11Si0.89O3) are investigated using X-ray emission and Mössbauer spectroscopies with laser annealing up to 115 GPa. The results show that Fe predominantly substitutes for Mg2+ in the pseudo-dodecahedral A site, in which 80% of the iron is Fe3+ that enters the lattice via the charge-coupled substitution with Al3+ in the octahedral B site. The total spin momentum and hyperfine parameters indicate that these ions remain in the high-spin state with Fe2+ having extremely high quadrupole splitting due to lattice distortion. (Al,Fe)-bearing bridgmanite is expected to contain mostly high-spin, A-site Fe3+, together with a smaller amount of A-site Fe2+, that remains stable throughout the region. Even though the spin transition of B-site Fe3+ in bridgmanite was reported to cause changes in its elasticity at high pressures, (Fe,Al)-bearing bridgmanite with predominantly A-site Fe will not exhibit elastic anomalies associated with the spin transition.

Radiation-Induced Damage to Nucleic Acid Constituents

NASA Astrophysics Data System (ADS)

Kim, Heasook

The objective of this research was to identify the primary free radical species produced by ionizing radiation in DNA. The ultimate goal would be to use these data obtained from model compounds to analyze radiation-induced damage in DNA itself. The different single crystals were studied in detail. The first was the sodium salt of guanosine-3 ^':5^' -cyclic monophosphate (cyclic GMP). The results of studies on crystals irradiated at 4.2^ circK distinguished two species. One of these species exhibited a non-exchangeable proton coupling that was characterized by ENDOR spectroscopy and shown to be sigma proton. The spin density on C8 was deduced from the ENDOR hyperfine coupling tensor and found to be 0.15. The second species also exhibited a non-exchangeable sigma proton coupling and a beta proton coupling. The spin densities on C8 and N9 were deduced from ENDOR measurements to be 0.09 and 0.36. The former is attributed to the oxidation product and the latter to the primary reduction product. These products are respectively the guanine cation and anion. The second single crystal studied was a sodium salt of 2^'-deoxyguanosine -5^'-monophosphate tetrahydrate. The ESR and ENDOR spectra obtained from this crystal after x-irradiation at 4.2^circK were complex and the paramagnetic species were tentatively identified as ionic species. The third DNA model compound studied was thymidine. Single crystal of thymidine were irradiated at 1.6^ circK and at 4.2^circ K. The lower temperature preserved a more primitive stage of the radiation damage process. ENDOR measurements distinguished three paramagnetic species. The most interesting component of the paramagnetic absorption in crystals irradiated at 1.6^circK is attributed to trapped electron. These electrons are stabilized by the electrostatic fields generated by hydroxy dipoles. The hyperfine couplings between the trapped electron and the proton of these polar groups were deduced from ENDOR measurements. The ESR and ENDOR measurements described in this report were carried out DNA model compounds x-irradiated and measured at lower temperatures than reported previously. The experiments have demonstrated that an earlier stage of radiation damage can sometimes be stabilized and characterized in single crystals by maintaining the sample at 1.4 ^circK. (Abstract shortened with permission of author.).

Analysis of the transient response of nuclear spins in GaAs with/without nuclear magnetic resonance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rasly, Mahmoud; Lin, Zhichao; Yamamoto, Masafumi

As an alternative to studying the steady-state responses of nuclear spins in solid state systems, working within a transient-state framework can reveal interesting phenomena. The response of nuclear spins in GaAs to a changing magnetic field was analyzed based on the time evolution of nuclear spin temperature. Simulation results well reproduced our experimental results for the transient oblique Hanle signals observed in an all-electrical spin injection device. The analysis showed that the so called dynamic nuclear polarization can be treated as a cooling tool for the nuclear spins: It works as a provider to exchange spin angular momentum between polarizedmore » electron spins and nuclear spins through the hyperfine interaction, leading to an increase in the nuclear polarization. In addition, a time-delay of the nuclear spin temperature with a fast sweep of the external magnetic field produces a possible transient state for the nuclear spin polarization. On the other hand, the nuclear magnetic resonance acts as a heating tool for a nuclear spin system. This causes the nuclear spin temperature to jump to infinity: i.e., the average nuclear spins along with the nuclear field vanish at resonant fields of {sup 75}As, {sup 69}Ga and {sup 71}Ga, showing an interesting step-dip structure in the oblique Hanle signals. These analyses provide a quantitative understanding of nuclear spin dynamics in semiconductors for application in future computation processing.« less

Unstable spin-ice order in the stuffed metallic pyrochlore Pr 2+xIr 2-xO 7-δ

DOE PAGES

MacLaughlin, D. E.; Bernal, O. O.; Shu, Lei; ...

2015-08-24

Specific heat, elastic neutron scattering, and muon spin rotation experiments have been carried out on a well-characterized sample of “stuffed” (Pr-rich) Pr 2+xIr 2-xO 7-δ. Elastic neutron scattering shows the onset of long-range spin-ice “2-in/2-out” magnetic order at 0.93 kelvin, with an ordered moment of 1.7(1) Bohr magnetons per Pr ion at low temperatures. Approximate lower bounds on the correlation length and correlation time in the ordered state are 170 angstroms and 0.7 nanosecond, respectively. Muon spin rotation experiments yield an upper bound 2.6(7) milliteslas on the local field B 4f loc at the muon site, which is nearly twomore » orders of magnitude smaller than the expected dipolar field for long-range spin-ice ordering of 1.7-Bohr magneton moments (120–270 milliteslas, depending on the muon site). This shortfall is due in part to splitting of the non-Kramers crystal-field ground-state doublets of near-neighbor Pr 3+ ions by the positive-muon-induced lattice distortion. For this to be the only effect, however, ~160 Pr moments out to a distance of ~14 angstroms must be suppressed. An alternative scenario—one consistent with the observed reduced nuclear hyperfine Schottky anomaly in the specific heat—invokes slow correlated Pr-moment fluctuations in the ordered state that average B 4f loc on the μSR time scale (~10 -7 second), but are static on the time scale of the elastic neutron scattering experiments (~10 -9 second). In this picture, the dynamic muon relaxation suggests a Pr 3+ 4f correlation time of a few nanoseconds, which should be observable in a neutron spin echo experiment.« less

Vitamin K 3 family members - Part II: Single crystal X-ray structures, temperature-induced packing polymorphism, magneto-structural correlations and probable anti-oncogenic candidature

NASA Astrophysics Data System (ADS)

Rane, Sandhya; Ahmed, Khursheed; Salunke-Gawali, Sunita; Zaware, Santosh B.; Srinivas, D.; Gonnade, Rajesh; Bhadbhade, Mohan

2008-12-01

Temperature-induced packing polymorphism is observed for vitamin K 3 (menadione, 3-methyl-1,4-naphthoquinone, 1). Form 1a crystallizes at 300 K and 1b at 277 K both in the same space group P2 1/ c. Form 1b contains one molecule per asymmetric unit, performing anisotropy in g-factor viz. g z = 2.0082, g y = 2.0055 and g x = 2.0025, whereas form 1a contains two molecules in its asymmetric unit. Vitamin K 3 family members 2, [2-hydroxy vitamin K 3] and 3, [2-hydroxy-1-oximino vitamin K 3] also perform intrinsic neutral active naphthosemiquinone valence tautomers even in dark having spin concentrations due to hydrogen bonding and aromatic stacking interactions which are compared to vitamin K 3. The significant lateral C-H⋯O and O-H⋯π bifurcated or π-π ∗ interactions are discussed for molecular associations and radical formations. X-ray structure of 3 revealed π-π ∗ stack dimers as radicals signatured in EPR as triplet with five hyperfine splits [ Ā( 14N) = 11.9 G]. The centrosymmetric biradicals in 3 show diamagnetism at high temperature but below 10 K it shows paramagnetism with μeff as 0.19 B.M. Vitamin K 3 and its family members inhibit biological activities of acid phosphatase ( APase), which are proportional to their spin concentrations. This may relate to their probable anti-oncogenic candidature in future.

Spectroscopy of a Synthetic Trapped Ion Qubit

NASA Astrophysics Data System (ADS)

Hucul, David; Christensen, Justin E.; Hudson, Eric R.; Campbell, Wesley C.

2017-09-01

133Ba+ has been identified as an attractive ion for quantum information processing due to the unique combination of its spin-1 /2 nucleus and visible wavelength electronic transitions. Using a microgram source of radioactive material, we trap and laser cool the synthetic A =133 radioisotope of barium II in a radio-frequency ion trap. Using the same, single trapped atom, we measure the isotope shifts and hyperfine structure of the 62P1 /2↔62S1 /2 and 62P1 /2↔52D3 /2 electronic transitions that are needed for laser cooling, state preparation, and state detection of the clock-state hyperfine and optical qubits. We also report the 62P1 /2↔52D3 /2 electronic transition isotope shift for the rare A =130 and 132 barium nuclides, completing the spectroscopic characterization necessary for laser cooling all long-lived barium II isotopes.

Hyperfine frequencies of {sup 87}Rb and {sup 133}Cs atoms in Xe gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGuyer, B. H.; Xia, T.; Jau, Y.-Y.

2011-09-15

The microwave resonant frequencies of ground-state {sup 87}Rb and {sup 133}Cs atoms in Xe buffer gas are shown to have a relatively large nonlinear dependence on the Xe pressure, presumably because of RbXe or CsXe van der Waals molecules. The nonlinear shifts for Xe are opposite in sign to the previously measured shifts for Ar and Kr, even though all three gases have negative linear shifts. The Xe data show striking discrepancies with the previous theory for nonlinear shifts. Most of this discrepancy is eliminated by accounting for the spin-rotation interaction, {gamma}N{center_dot}S, in addition to the hyperfine-shift interaction, {delta} Amore » I{center_dot}S, in the molecules. To the limit of our experimental accuracy, the shifts of {sup 87}Rb and {sup 133}Cs in He, Ne, and N{sub 2} were linear with pressure.« less

Copper ESEEM and HYSCORE through ultra-wideband chirp EPR spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Segawa, Takuya F.; Doll, Andrin; Pribitzer, Stephan

2015-07-28

The main limitation of pulse electron paramagnetic resonance (EPR) spectroscopy is its narrow excitation bandwidth. Ultra-wideband (UWB) excitation with frequency-swept chirp pulses over several hundreds of megahertz overcomes this drawback. This allows to excite electron spin echo envelope modulation (ESEEM) from paramagnetic copper centers in crystals, whereas up to now, only ESEEM of ligand nuclei like protons or nitrogens at lower frequencies could be detected. ESEEM spectra are recorded as two-dimensional correlation experiments, since the full digitization of the electron spin echo provides an additional Fourier transform EPR dimension. Thus, UWB hyperfine-sublevel correlation experiments generate a novel three-dimensional EPR-correlated nuclearmore » modulation spectrum.« less

Diffusion studies on permeable nitroxyl spin probe through lipid bilayer membrane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benial, A. Milton Franklin; Meenakumari, V.; Ichikawa, Kazuhiro

2014-04-24

Electron spin resonance (ESR) studies were carried out for 2mM {sup 14}N labeled deutrated permeable 3- methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl (MC-PROXYL) in pure water, 1 mM, 2 mM, 3 mM and 4 mM concentration of MC-PROXYL in 300 mM concentration of liposomal solution by using a L-band ESR spectrometer. The ESR parameters such as linewidth, hyperfine coupling constant, g-factor, partition parameter and permeability were reported. The partition parameter and permeability values indicate the maximum spin distribution in the lipid phase at 2 mM concentration. This study illustrates that ESR can be used to differentiate between the intra and extra-membrane water by loading themore » liposome vesicles with a lipid-permeable nitroxyl spin probe. From the ESR results, the radical concentration was optimized as 2 mM in liposomal solution for ESR phantom studies and experiments.« less

Coherent coupling between a quantum dot and a donor in silicon

DOE PAGES

Harvey-Collard, Patrick; Jacobson, N. Tobias; Rudolph, Martin; ...

2017-10-18

Individual donors in silicon chips are used as quantum bits with extremely low error rates. However, physical realizations have been limited to one donor because their atomic size causes fabrication challenges. Quantum dot qubits, in contrast, are highly adjustable using electrical gate voltages. This adjustability could be leveraged to deterministically couple donors to quantum dots in arrays of qubits. In this work, we demonstrate the coherent interaction of a 31P donor electron with the electron of a metal-oxide-semiconductor quantum dot. We form a logical qubit encoded in the spin singlet and triplet states of the two-electron system. We show thatmore » the donor nuclear spin drives coherent rotations between the electronic qubit states through the contact hyperfine interaction. This provides every key element for compact two-electron spin qubits requiring only a single dot and no additional magnetic field gradients, as well as a means to interact with the nuclear spin qubit.« less

Nonlocal Polarization Feedback in a Fractional Quantum Hall Ferromagnet.

PubMed

Hennel, Szymon; Braem, Beat A; Baer, Stephan; Tiemann, Lars; Sohi, Pirouz; Wehrli, Dominik; Hofmann, Andrea; Reichl, Christian; Wegscheider, Werner; Rössler, Clemens; Ihn, Thomas; Ensslin, Klaus; Rudner, Mark S; Rosenow, Bernd

2016-04-01

In a quantum Hall ferromagnet, the spin polarization of the two-dimensional electron system can be dynamically transferred to nuclear spins in its vicinity through the hyperfine interaction. The resulting nuclear field typically acts back locally, modifying the local electronic Zeeman energy. Here we report a nonlocal effect arising from the interplay between nuclear polarization and the spatial structure of electronic domains in a ν=2/3 fractional quantum Hall state. In our experiments, we use a quantum point contact to locally control and probe the domain structure of different spin configurations emerging at the spin phase transition. Feedback between nuclear and electronic degrees of freedom gives rise to memristive behavior, where electronic transport through the quantum point contact depends on the history of current flow. We propose a model for this effect which suggests a novel route to studying edge states in fractional quantum Hall systems and may account for so-far unexplained oscillatory electronic-transport features observed in previous studies.

EPR investigation of Ti2+ in SrCl2 single crystals.

NASA Technical Reports Server (NTRS)

Herrington, J. R.; Estle, T. L.; Boatner, L. A.

1972-01-01

The observation of 'double quantum' transitions which made it possible to determine the charge state of Ti as 2+ is reported. The EPR spectrum observed at 1.2 K is presented in a graph. The first derivative of the absorption is shown vs the magnetic field. The hyperfine patterns for the Ti-47 and Ti-49 isotopes are identified. Spin-Hamiltonian parameters for Ti(2+) in various cubic hosts are listed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carvalho, R. S.; Ávila, H. C.; Cremona, M., E-mail: cremona@fis.puc-rio.br

The recently discovered organic magnetoresistance effect (OMAR) reveals the spin-dependent behavior of the charge transport in organic semiconductors. So far, it is known that hyperfine interactions play an important role in this phenomenon and also that spin-orbit coupling is negligible for light-atom based compounds. However, in the presence of heavy atoms, spin-orbit interactions should play an important role in OMAR. It is known that these interactions are responsible for singlet and triplet states mixing via intersystem crossing and the change of spin-charge relaxation time in the charge mobility process. In this work, we report a dramatic change in the OMARmore » effect caused by the presence of strong intramolecular spin-orbit coupling in a series of rare-earth quinolate organic complex-based devices. Our data show a different OMAR lineshape compared with the OMAR lineshape of tris(8-hydroxyquinolinate) aluminum-based devices, which are well described in the literature. In addition, electronic structure calculations based on density functional theory help to establish the connection between this results and the presence of heavy central ions in the different complexes.« less

Zero Quantum Coherence in a Series of Covalent Spin-Correlated Radical Pairs.

PubMed

Nelson, Jordan N; Krzyaniak, Matthew D; Horwitz, Noah E; Rugg, Brandon K; Phelan, Brian T; Wasielewski, Michael R

2017-03-23

Photoinitiated subnanosecond electron transfer within covalently linked electron donor-acceptor molecules can result in the formation of a spin-correlated radical pair (SCRP) with a well-defined initial singlet spin configuration. Subsequent coherent mixing between the SCRP singlet and triplet m s = 0 spin states, the so-called zero quantum coherence (ZQC), is of potential interest in quantum information processing applications because the ZQC can be probed using pulse electron paramagnetic resonance (pulse-EPR) techniques. Here, pulse-EPR spectroscopy is utilized to examine the ZQC oscillation frequencies and ZQC dephasing in three structurally well-defined D-A systems. While transitions between the singlet and triplet m s = 0 spin states are formally forbidden (Δm s = 0), they can be addressed using specific microwave pulse turning angles to map information from the ZQC onto observable single quantum coherences. In addition, by using structural variations to tune the singlet-triplet energy gap, the ZQC frequencies determined for this series of molecules indicate a stronger dependence on the electronic g-factor than on electron-nuclear hyperfine interactions.

Reduction process of nitroxyl spin probes used in Overhauser-enhanced magnetic resonance imaging: An ESR study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meenakumari, V.; Premkumar, S.; Benial, A. Milton Franklin, E-mail: miltonfranklin@yahoo.com

The Electron spin resonance studies on the reduction process of nitroxyl spin probes were carried out for 1mM {sup 14}N- labeled nitroxyl radicals in pure water and 1 mM concentration of ascorbic acid as a function of time. The electron spin resonance parameters, such as line width, hyperfine coupling constant, g-factor, signal intensity ratio and rotational correlation time were estimated. The 3-carbamoyl-PROXYL radical has narrowest line width and fast tumbling motion compared with 3-carboxy-PROXYL, 4-methoxy-TEMPO, and 4-acetamido-TEMPO radicals. The half life time and decay rate were estimated for 1mM concentration of {sup 14}N- labeled nitroxyl radicals in 1 mM concentration ofmore » ascorbic acid. From the results, the 3-carbamoyl-PROXYL has long half life time and high stability compared with 3-carboxy-PROXYL, 4-methoxy-TEMPO and 4-acetamido-TEMPO radicals. Therefore, this study reveals that the 3-carbamoyl-PROXYL radical can act as a good redox sensitive spin probe for Overhauser-enhanced Magnetic Resonance Imaging.« less

Ultrafast Generation of Large Schrodinger Cat States

NASA Astrophysics Data System (ADS)

Johnson, Kale; Neyenhuis, Brian; Wong-Campos, David; Mizrahi, Jonathan; Campbell, Wes; Monroe, Christopher

2014-05-01

Using a series of spin-dependent kicks on a trapped Yb + ion, we create large, entangled, Schrodinger cat states. We prepare the ion in a superposition of its two mf = 0 hyperfine ground states, representing an effective spin-1/2 system. Trapped in a harmonic potential, the ion is illuminated with a specially shaped, 1.5 ns pulse that imparts a momentum kick on the ion with a spin-dependent direction. A fast Pockels cell allows us to change the direction of the spin-dependent kick from each subsequent pulse out of an 80 MHz mode-locked laser. By concatenating a series of these very high fidelity spin-dependent kicks, we separate the ion's wave packet into two, spatially distinct states separated by about 200 recoil momenta and involving about 70 phonons. This method for creating a Schrodinger cat state is not time-limited by the trap frequency, and does not rely on confinement in the Lamb-Dicke regime. This work is supported by grants from the U.S. Army Research Office with funding from the DARPA OLE program, IARPA, and the MURI program; and the NSF Physics Frontier Center at JQI.

Measure synchronization in a spin-orbit-coupled bosonic Josephson junction

NASA Astrophysics Data System (ADS)

Wang, Wen-Yuan; Liu, Jie; Fu, Li-Bin

2015-11-01

We present measure synchronization (MS) in a bosonic Josephson junction with spin-orbit coupling. The two atomic hyperfine states are coupled by a Raman dressing scheme, and they are regarded as two orientations of a pseudo-spin-1 /2 system. A feature specific to a spin-orbit-coupled (SOC) bosonic Josephson junction is that the transition from non-MS to MS dynamics can be modulated by Raman laser intensity, even in the absence of interspin atomic interaction. A phase diagram of non-MS and MS dynamics as functions of Raman laser intensity and Josephson tunneling amplitude is presented. Taking into account interspin atomic interactions, the system exhibits MS breaking dynamics resulting from the competition between intraspin and interspin atomic interactions. When interspin atomic interactions dominate in the competition, the system always exhibits MS dynamics. For interspin interaction weaker than intraspin interaction, a window for non-MS dynamics is present. Since SOC Bose-Einstein condensates provide a powerful platform for studies on physical problems in various fields, the study of MS dynamics is valuable in researching the collective coherent dynamical behavior in a spin-orbit-coupled bosonic Josephson junction.

Coherent manipulation of quantum spin states in a single molecular nanomagnet

NASA Astrophysics Data System (ADS)

Wernsdorfer, Wolfgang

The endeavour of quantum electronics is driven by one of the most ambitious technological goals of today's scientists: the realization of an operational quantum computer (http://qurope.eu). We started to address this goal by the new research field of molecular quantum spintronics. The building blocks are magnetic molecules, i.e. well-defined spin qubits. We will discuss this still largely unexplored field and present our first results: For example, using a molecular spin-transistor, we achieved the electronic read-out of the nuclear spin of an individual metal atom embedded in an SMM. We could show very long spin lifetimes (>10 s). Using the hyperfine Stark effect, which transforms electric fields into local effective magnetic fields, we could not only tune the resonance frequency by several MHz, but also perform coherent quantum manipulations on a single nuclear qubit faster than a μs by means of electrical fields only, establishing the individual addressability of identical nuclear qubits. Using three different microwave frequencies, we could implement a simple four-level Grover algorithm. S. Thiele, F. Balestro, R. Ballou, S. Klyatskaya, M. Ruben, W. Wernsdorfer, Science 344, 1135 (2014).

Reduction process of nitroxyl spin probes used in Overhauser-enhanced magnetic resonance imaging: An ESR study

NASA Astrophysics Data System (ADS)

Meenakumari, V.; Jawahar, A.; Premkumar, S.; Benial, A. Milton Franklin

2016-05-01

The Electron spin resonance studies on the reduction process of nitroxyl spin probes were carried out for 1mM 14N- labeled nitroxyl radicals in pure water and 1 mM concentration of ascorbic acid as a function of time. The electron spin resonance parameters, such as line width, hyperfine coupling constant, g-factor, signal intensity ratio and rotational correlation time were estimated. The 3-carbamoyl-PROXYL radical has narrowest line width and fast tumbling motion compared with 3-carboxy-PROXYL, 4-methoxy-TEMPO, and 4-acetamido-TEMPO radicals. The half life time and decay rate were estimated for 1mM concentration of 14N- labeled nitroxyl radicals in 1 mM concentration of ascorbic acid. From the results, the 3-carbamoyl-PROXYL has long half life time and high stability compared with 3-carboxy-PROXYL, 4-methoxy-TEMPO and 4-acetamido-TEMPO radicals. Therefore, this study reveals that the 3-carbamoyl-PROXYL radical can act as a good redox sensitive spin probe for Overhauser-enhanced Magnetic Resonance Imaging.

Spin-interaction effects for ultralong-range Rydberg molecules in a magnetic field

NASA Astrophysics Data System (ADS)

Hummel, Frederic; Fey, Christian; Schmelcher, Peter

2018-04-01

We investigate the fine and spin structure of ultralong-range Rydberg molecules exposed to a homogeneous magnetic field. Each molecule consists of a 87Rb Rydberg atom the outer electron of which interacts via spin-dependent s - and p -wave scattering with a polarizable 87Rb ground-state atom. Our model includes also the hyperfine structure of the ground-state atom as well as spin-orbit couplings of the Rydberg and ground-state atom. We focus on d -Rydberg states and principal quantum numbers n in the vicinity of 40. The electronic structure and vibrational states are determined in the framework of the Born-Oppenheimer approximation for varying field strengths ranging from a few up to hundred Gauss. The results show that the interplay between the scattering interactions and the spin couplings gives rise to a large variety of molecular states in different spin configurations as well as in different spatial arrangements that can be tuned by the magnetic field. This includes relatively regularly shaped energy surfaces in a regime where the Zeeman splitting is large compared to the scattering interaction but small compared to the Rydberg fine structure, as well as more complex structures for both weaker and stronger fields. We quantify the impact of spin couplings by comparing the extended theory to a spin-independent model.

Electrically Driving Donor Spin Qubits in Silicon Using Photonic Bandgap Resonators

NASA Astrophysics Data System (ADS)

Sigillito, A. J.; Tyryshkin, A. M.; Lyon, S. A.

In conventional experiments, donor nuclear spin qubits in silicon are driven using radiofrequency (RF) magnetic fields. However, magnetic fields are difficult to confine at the nanoscale, which poses major issues for individually addressable qubits and device scalability. Ideally one could drive spin qubits using RF electric fields, which are easy to confine, but spins do not naturally have electric dipole transitions. In this talk, we present a new method for electrically controlling nuclear spin qubits in silicon by modulating the hyperfine interaction between the nuclear spin qubit and the donor-bound electron. By fabricating planar superconducting photonic bandgap resonators, we are able to use pulsed electron-nuclear double resonance (ENDOR) techniques to selectively probe both electrically and magnetically driven transitions for 31P and 75As nuclear spin qubits. The electrically driven spin resonance mechanism allows qubits to be driven at either their transition frequency, or at one-half their transition frequency, thus reducing bandwidth requirements for future quantum devices. Moreover, this form of control allows for higher qubit densities and lower power requirements compared to magnetically driven schemes. In our proof-of-principle experiments we demonstrate electrically driven Rabi frequencies of approximately 50 kHz for widely spaced (10 μm) gates which should be extendable to MHz for nanoscale devices.

Theory for cross effect dynamic nuclear polarization under magic-angle spinning in solid state nuclear magnetic resonance: the importance of level crossings.

PubMed

Thurber, Kent R; Tycko, Robert

2012-08-28

We present theoretical calculations of dynamic nuclear polarization (DNP) due to the cross effect in nuclear magnetic resonance under magic-angle spinning (MAS). Using a three-spin model (two electrons and one nucleus), cross effect DNP with MAS for electron spins with a large g-anisotropy can be seen as a series of spin transitions at avoided crossings of the energy levels, with varying degrees of adiabaticity. If the electron spin-lattice relaxation time T(1e) is large relative to the MAS rotation period, the cross effect can happen as two separate events: (i) partial saturation of one electron spin by the applied microwaves as one electron spin resonance (ESR) frequency crosses the microwave frequency and (ii) flip of all three spins, when the difference of the two ESR frequencies crosses the nuclear frequency, which transfers polarization to the nuclear spin if the two electron spins have different polarizations. In addition, adiabatic level crossings at which the two ESR frequencies become equal serve to maintain non-uniform saturation across the ESR line. We present analytical results based on the Landau-Zener theory of adiabatic transitions, as well as numerical quantum mechanical calculations for the evolution of the time-dependent three-spin system. These calculations provide insight into the dependence of cross effect DNP on various experimental parameters, including MAS frequency, microwave field strength, spin relaxation rates, hyperfine and electron-electron dipole coupling strengths, and the nature of the biradical dopants.

The NaK 1 1,3delta states: theoretical and experimental studies of fine and hyperfine structure of rovibrational levels near the dissociation limit.

PubMed

Wilkins, A D; Morgus, L; Hernandez-Guzman, J; Huennekens, J; Hickman, A P

2005-09-22

Earlier high-resolution spectroscopic studies of the fine and hyperfine structure of rovibrational levels of the 1 3delta state of NaK have been extended to include high lying rovibrational levels with v < or = 59, of which the highest levels lie within approximately 4 cm(-1) of the dissociation limit. A potential curve is determined using the inverted perturbation approximation method that reproduces these levels to an accuracy of approximately 0.026 cm(-1). For the largest values of v, the outer turning points occur near R approximately 12.7 angstroms, which is sufficiently large to permit the estimation of the C6 coefficient for this state. The fine and hyperfine structure of the 1 3delta rovibrational levels has been fit using the matrix diagonalization method that has been applied to other states of NaK, leading to values of the spin-orbit coupling constant A(v) and the Fermi contact constant b(F). New values determined for v < or = 33 are consistent with values determined by a simpler method and reported earlier. The measured fine and hyperfine structure for v in the range 44 < or = v < or = 49 exhibits anomalous behavior whose origin is believed to be the mixing between the 1 3delta and 1 1delta states. The matrix diagonalization method has been extended to treat this interaction, and the results provide an accurate representation of the complicated patterns that arise. The analysis leads to accurate values for A(v) and b(F) for all values of v < or = 49. For higher v (50 < or = v < or = 59), several rovibrational levels have been assigned, but the pattern of fine and hyperfine structure is difficult to interpret. Some of the observed features may arise from effects not included in the current model.

Heavy-ion-induced sucrose radicals investigated using EPR and UV spectroscopy

PubMed Central

Nakagawa, Kouichi; Karakirova, Yordanka; Yordanov, Nicola D.

2015-01-01

The potential use of a sucrose dosimeter for estimating both linear energy transfer (LET) and the absorbed dose of heavy ion and X-ray radiation was investigated. The stable free radicals were produced when sucrose was irradiated with heavy ions, such as helium, carbon, silicon and neon ions, and when the X-ray radiation was similar to the obtained electron paramagnetic resonance (EPR) spectra, which were ∼7 mT wide and composed of several hyperfine structures. In addition, the total spin concentration resulting from heavy-ion irradiation increased linearly as the absorbed dose increased, and decreased logarithmically as the LET increased. These empirical relations imply that the LET at a certain dose can be determined from the spin concentration. For sucrose and alanine, both cross-sections following C-ion irradiation with a 50 Gy dose were ∼1.3 × 10−12 [μm2], taking into account the molecular size of the samples. The values of these cross-sections imply that multiple ionizing particles were involved in the production of stable radicals. Furthermore, UV absorbance at 267 nm of an aqueous solution of irradiated sucrose was found to linearly increase with increasing absorbed dose. Therefore, the EPR and UV results suggest that sucrose can be a useful dosimeter for heavy-ion irradiation. PMID:25480828

Coherent manipulation of a Si/SiGe-based singlet-triplet qubit

NASA Astrophysics Data System (ADS)

Gyure, Mark

2012-02-01

Electrically defined silicon-based qubits are expected to show improved quantum memory characteristics in comparison to GaAs-based devices due to reduced hyperfine interactions with nuclear spins. Silicon-based qubit devices have proved more challenging to build than their GaAs-based counterparts, but recently several groups have reported substantial progress in single-qubit initialization, measurement, and coherent operation. We report [1] coherent control of electron spins in two coupled quantum dots in an undoped Si/SiGe heterostructure, forming two levels of a singlet-triplet qubit. We measure a nuclei-induced T2^* of 360 ns, an increase over similar measurements in GaAs-based quantum dots by nearly two orders of magnitude. We also describe the results from detailed modeling of our materials and devices that show this value for T2^* is consistent with theoretical expectations for our estimated dot sizes and a natural abundance of ^29Si. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressly or implied, of the United States Department of Defense or the U.S. Government. Approved for public release, distribution unlimited.[4pt] [1] B. M. Maune et al., ``Coherent Singlet-Triplet Oscillations in a Silicon-based Double Quantum Dot,'' accepted by Nature.

Electrical control of a long-lived spin qubit in a Si/SiGe quantum dot.

PubMed

Kawakami, E; Scarlino, P; Ward, D R; Braakman, F R; Savage, D E; Lagally, M G; Friesen, Mark; Coppersmith, S N; Eriksson, M A; Vandersypen, L M K

2014-09-01

Nanofabricated quantum bits permit large-scale integration but usually suffer from short coherence times due to interactions with their solid-state environment. The outstanding challenge is to engineer the environment so that it minimally affects the qubit, but still allows qubit control and scalability. Here, we demonstrate a long-lived single-electron spin qubit in a Si/SiGe quantum dot with all-electrical two-axis control. The spin is driven by resonant microwave electric fields in a transverse magnetic field gradient from a local micromagnet, and the spin state is read out in the single-shot mode. Electron spin resonance occurs at two closely spaced frequencies, which we attribute to two valley states. Thanks to the weak hyperfine coupling in silicon, a Ramsey decay timescale of 1 μs is observed, almost two orders of magnitude longer than the intrinsic timescales in GaAs quantum dots, whereas gate operation times are comparable to those reported in GaAs. The spin echo decay time is ~40 μs, both with one and four echo pulses, possibly limited by intervalley scattering. These advances strongly improve the prospects for quantum information processing based on quantum dots.

Schemes of detecting nuclear spin correlations by dynamical decoupling based quantum sensing

NASA Astrophysics Data System (ADS)

Ma, Wen-Long Ma; Liu, Ren-Bao

Single-molecule sensitivity of nuclear magnetic resonance (NMR) and angstrom resolution of magnetic resonance imaging (MRI) are the highest challenges in magnetic microscopy. Recent development in dynamical decoupling (DD) enhanced diamond quantum sensing has enabled NMR of single nuclear spins and nanoscale NMR. Similar to conventional NMR and MRI, current DD-based quantum sensing utilizes the frequency fingerprints of target nuclear spins. Such schemes, however, cannot resolve different nuclear spins that have the same noise frequency or differentiate different types of correlations in nuclear spin clusters. Here we show that the first limitation can be overcome by using wavefunction fingerprints of target nuclear spins, which is much more sensitive than the ''frequency fingerprints'' to weak hyperfine interaction between the targets and a sensor, while the second one can be overcome by a new design of two-dimensional DD sequences composed of two sets of periodic DD sequences with different periods, which can be independently set to match two different transition frequencies. Our schemes not only offer an approach to breaking the resolution limit set by ''frequency gradients'' in conventional MRI, but also provide a standard approach to correlation spectroscopy for single-molecule NMR.

Notch filtering the nuclear environment of a spin qubit.

PubMed

Malinowski, Filip K; Martins, Frederico; Nissen, Peter D; Barnes, Edwin; Cywiński, Łukasz; Rudner, Mark S; Fallahi, Saeed; Gardner, Geoffrey C; Manfra, Michael J; Marcus, Charles M; Kuemmeth, Ferdinand

2017-01-01

Electron spins in gate-defined quantum dots provide a promising platform for quantum computation. In particular, spin-based quantum computing in gallium arsenide takes advantage of the high quality of semiconducting materials, reliability in fabricating arrays of quantum dots and accurate qubit operations. However, the effective magnetic noise arising from the hyperfine interaction with uncontrolled nuclear spins in the host lattice constitutes a major source of decoherence. Low-frequency nuclear noise, responsible for fast (10 ns) inhomogeneous dephasing, can be removed by echo techniques. High-frequency nuclear noise, recently studied via echo revivals, occurs in narrow-frequency bands related to differences in Larmor precession of the three isotopes 69 Ga, 71 Ga and 75 As (refs 15,16,17). Here, we show that both low- and high-frequency nuclear noise can be filtered by appropriate dynamical decoupling sequences, resulting in a substantial enhancement of spin qubit coherence times. Using nuclear notch filtering, we demonstrate a spin coherence time (T 2 ) of 0.87 ms, five orders of magnitude longer than typical exchange gate times, and exceeding the longest coherence times reported to date in Si/SiGe gate-defined quantum dots.

Experimental insights into spin state and hyperfine parameters of Fe3+ in bridgmanite and silicate glass up to 91 GPa

NASA Astrophysics Data System (ADS)

Lv, M.; Dorfman, S.; Liu, J.; Farmer, A. B.; Potapkin, V.; Chumakov, A. I.; McCammon, C. A.; Greenberg, E.; Prakapenka, V. B.; Popov, D.

2017-12-01

The spin and valence state of Fe in (Mg,Fe,Al)(Si,Fe,Al)O3 bridgmanite and silicate melts is important to understanding the composition, structure, and dynamics of the Earth's lower mantle. Previous experimental and theoretical studies conclude that Fe3+ in B-site of bridgmanite undergoes a high spin (HS) to low spin (LS) transition, but conflicting measurements of spin transition pressures (18-70 GPa) and significant disagreement on hyperfine parameters of LS Fe3+ need to be resolved. We performed energy-domain synchrotron Mössbauer spectroscopy (E-SMS) and X-ray diffraction (XRD) experiments up to 91 GPa (corresponding to 2000 km depth in the mid lower mantle) to explore the electronic behavior of Fe in both silicate glass and bridgmanite with measured composition (Mg0.97Fe0.20Si0.90O3). Fe3+ and Fe2+ were identified on the basis of center shift (CS) at 1 bar of 0.4 and 1 mm/s, respectively. The Mössbauer spectra of glass exhibit a continuous spin transition of Fe3+ between 11 to 40 GPa, while Fe2+ adopts the HS state up to 91 GPa. Bridgmanite Mössbauer spectra indicate two HS Fe2+ doublets corresponding to local distortion of the A-site, and that the bulk of the Fe3+ exhibits quadrupole splitting (QS) ranging from 0.8-1.3 mm/s over the entire pressure range studied. Because stoichiometry suggests most Fe3+ occupies the B-site, if the spin transition occurs it must have a small effect on Mössbauer parameters, as observed in recent studies of (Mg0.5Fe1.0Si0.5O3) and (Mg0.97Fe0.06Si0.97O3) bridgmanite. No discontinuity or softening is observed in the equation of state (EOS) of the bridgmanite between 38-103 GPa and 300 K. The bulk modulus and unit cell volume at ambient conditions obtained by fitting the unit cell volume data to the second-order Birch-Murnaghan EOS are 264(3) GPa and 163.6(3) Å3, respectively, consistent with previous studies of (Mg0.90Fe0.20Si0.90O3) bridgmanite. The spin transition in Fe3+ may have too small an effect on elastic properties of bridgmanite in the mantle to be detectable via seismic observations.

Carbon-related platinum defects in silicon: An electron paramagnetic resonance study of high spin states

NASA Astrophysics Data System (ADS)

Scheerer, O.; Höhne, M.; Juda, U.; Riemann, H.

1997-10-01

In this article, we report about complexes in silicon investigated by electron paramagnetic resonance (EPR). In silicon doped with C and Pt we detected two different complexes: cr-1Pt (cr: carbon-related, 1Pt: one Pt atom) and cr-3Pt. The complexes have similar EPR properties. They show a trigonal symmetry with effective g-values geff,⊥=2g⊥≈4 and geff,‖=g‖≈2 (g⊥, g‖ true g-values). The g-values can be explained by a spin Hamiltonian with large fine-structure energy (electron spin S=3/2) and smaller Zeeman interaction. The participation of platinum in the complexes is proved by the hyperfine interaction. From experiments with varying carbon concentration we conclude that the complexes contain carbon. Atomistic models based on the Watkins vacancy-model for substitutional Pt were developed.

Pulsed electron nuclear double resonance studies of the photoexcited triplet state of pentacene in p-terphenyl crystals at room temperature.

PubMed

Yago, Tomoaki; Link, Gerhard; Kothe, Gerd; Lin, Tien-Sung

2007-09-21

Pulsed electron nuclear double resonance (ENDOR) using a modified Davies-type [Phys. Lett. 47A, 1 (1974)] sequence is employed to study the hyperfine (HF) structure of the photoexcited triplet state of pentacene dispersed in protonated and deuterated p-terphenyl single crystals. The strong electron spin polarization and long phase memory time of triplet pentacene enable us to perform the ENDOR measurements on the S=1 spin system at room temperature. Proton HF tensor elements and spin density values of triplet pentacene are extracted from a detailed angular-dependent study in which the orientation of the magnetic field is varied systematically in two different pentacene planes. Analysis reveals that the pentacene molecule is no longer planar in the p-terphenyl host lattice. The distortion is more pronounced in the deuterated crystal where the unit cell dimensions are slightly smaller than those of the protonated crystal.

Experimental investigation of vector static magnetic field detection using an NV center with a single first-shell 13C nuclear spin in diamond

NASA Astrophysics Data System (ADS)

Jiang, Feng-Jian; Ye, Jian-Feng; Jiao, Zheng; Jiang, Jun; Ma, Kun; Yan, Xin-Hu; Lv, Hai-Jiang

2018-05-01

We perform a proof-of-principle experiment that uses a single negatively charged nitrogen–vacancy (NV) color center with a nearest neighbor 13C nuclear spin in diamond to detect the strength and direction (including both polar and azimuth angles) of a static vector magnetic field by optical detection magnetic resonance (ODMR) technique. With the known hyperfine coupling tensor between an NV center and a nearest neighbor 13C nuclear spin, we show that the information of static vector magnetic field could be extracted by observing the pulsed continuous wave (CW) spectrum. Project supported by the National Natural Science Foundation of China (Grant Nos. 11305074, 11135002, and 11275083), the Key Program of the Education Department Outstanding Youth Foundation of Anhui Province, China (Grant No. gxyqZD2017080), and the Education Department Natural Science Foundation of Anhui Province, China (Grant No. KJHS2015B09).

The Pure Rotational Spectrum of KO

NASA Astrophysics Data System (ADS)

Burton, Mark; Russ, Benjamin; Sheridan, Phillip M.; Bucchino, Matthew; Ziurys, Lucy M.

2017-06-01

The pure rotational spectrum of potassium monoxide (KO) has been recorded using millimeter-wave direct absorption spectroscopy. KO was synthesized by the reaction of potassium vapor, produced in a Broida-type oven, with nitrous oxide. No DC discharge was necessary. Eleven rotational transitions belonging to the ^{2}Π_{3/2} spin-orbit component have been measured and have been fit successfully to a case (c) Hamiltonian. Rotational and lambda-doubling constants for this spin-orbit component have been determined. It has been suggested that the ground electronic state of KO is either ^{2}Π (as for LiO and NaO) or ^{2}Σ (as for RbO and CsO), both of which lie close in energy. Recent computational studies favor a ^{2}Σ ground state. Further measurements of the rotational transitions of the ^{2}Π_{1/2} spin-orbit component and the ^{2}Σ state are currently in progress, as well as the potassium hyperfine structure.

Theory of the neutral nitrogen-vacancy center in diamond and its application to the realization of a qubit

NASA Astrophysics Data System (ADS)

Gali, Adam

2009-06-01

The negatively charged nitrogen-vacancy defect (NV-) in diamond has attracted much attention in recent years in qubit and biological applications. The negative charge is donated from nearby nitrogen donors that could limit or stem the successful application of NV- . In this study, we identify the neutral nitrogen-vacancy defect (NV0) by ab initio supercell calculations through the comparison of the measured and calculated hyperfine tensors of the A42 excited state. Our analysis shows that (i) the spin state can be selectively occupied optically, (ii) the electron spin state can be manipulated by time-varying magnetic field, and (iii) the spin state may be read out optically. Based on this NV0 is a hope for realizing qubit in diamond without the need of nitrogen donors. In addition, we propose that NV0 may be more sensitive magnetometer than the ultrasensitive NV- .

Subpicosecond X rotations of atomic clock states

NASA Astrophysics Data System (ADS)

Song, Yunheung; Lee, Han-gyeol; Kim, Hyosub; Jo, Hanlae; Ahn, Jaewook

2018-05-01

We demonstrate subpicosecond-timescale population transfer between the pair of hyperfine ground states of atomic rubidium using a single laser-pulse. Our scheme utilizes the geometric and dynamic phases induced during Rabi oscillation through the fine-structure excited state to construct an X rotation gate for the hyperfine-state qubit system. The experiment performed with a femtosecond laser and cold rubidium atoms, in a magnetooptical trap, shows over 98% maximal population transfer between the clock states.

Optically controlled locking of the nuclear field via coherent dark-state spectroscopy.

PubMed

Xu, Xiaodong; Yao, Wang; Sun, Bo; Steel, Duncan G; Bracker, Allan S; Gammon, Daniel; Sham, L J

2009-06-25

A single electron or hole spin trapped inside a semiconductor quantum dot forms the foundation for many proposed quantum logic devices. In group III-V materials, the resonance and coherence between two ground states of the single spin are inevitably affected by the lattice nuclear spins through the hyperfine interaction, while the dynamics of the single spin also influence the nuclear environment. Recent efforts have been made to protect the coherence of spins in quantum dots by suppressing the nuclear spin fluctuations. However, coherent control of a single spin in a single dot with simultaneous suppression of the nuclear fluctuations has yet to be achieved. Here we report the suppression of nuclear field fluctuations in a singly charged quantum dot to well below the thermal value, as shown by an enhancement of the single electron spin dephasing time T(2)*, which we measure using coherent dark-state spectroscopy. The suppression of nuclear fluctuations is found to result from a hole-spin assisted dynamic nuclear spin polarization feedback process, where the stable value of the nuclear field is determined only by the laser frequencies at fixed laser powers. This nuclear field locking is further demonstrated in a three-laser measurement, indicating a possible enhancement of the electron spin T(2)* by a factor of several hundred. This is a simple and powerful method of enhancing the electron spin coherence time without use of 'spin echo'-type techniques. We expect that our results will enable the reproducible preparation of the nuclear spin environment for repetitive control and measurement of a single spin with minimal statistical broadening.

Electron spin resonance investigations of /sup 11/B/sup 12/C, /sup 11/B/sup 13/C, and /sup 10/B/sup 12/C in neon, argon, and krypton matrices at 4 K: Comparison with theoretical results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knight L.B. Jr.; Cobranchi, S.T.; Petty, J.T.

1989-01-15

The first spectroscopic study of the diatomic radical BC is reported which confirms previous theoretical predictions of a /sup 4/summation/sup -/ electronic ground state. The nuclear hyperfine interactions (A tensors) obtained for /sup 11/B, /sup 10/B, and /sup 13/C from the electron spin resonance (ESR) measurements are compared with extensive ab initio CI calculations. The BC molecule is one of the first examples of a small high spin radical for such an in-depth experimental--theoretical comparison. The electronic structure of BC obtained from an analysis of the nuclear hyperfine interaction (hfi) is compared to that obtained from a Mulliken-type population analysismore » conducted on a CI wave function which yields A/sub iso/ and A/sub dip/ results in good agreement with the observed values. The BC radical was generated by the laser vaporization of a boron--carbon mixture and trapped in neon, argon, and krypton matrices at 4 K for a complete ESR characterization. The magnetic parameters (MHz) obtained for /sup 11/B/sup 13/C in solid neon are: g/sub parallel/ = 2.0015(3); g/sub perpendicular/ = 2.0020(3); D(zfs) = 1701(2); /sup 11/B: chemically bondA/sub parallel/chemically bond = 100(1); chemically bondA/sub perpendicular/chemically bond = 79(1); /sup 13/C: chemically bondA/sub parallel/chemically bond = 5(2) and chemically bondA/sub perpendicular/chemically bond = 15(1). Based on comparison with the theoretical results, the most likely choice of signs is that all A values are positive.« less

Local magnetic moment formation at 119Sn Mössbauer impurity in RCo2 (R=Gd,Tb,Dy,Ho,Er) Laves phase compounds

NASA Astrophysics Data System (ADS)

de Oliveira, A. L.; de Oliveira, N. A.; Troper, A.

2008-04-01

In this work, we theoretically study the local magnetic moment formation and the systematics of the magnetic hyperfine fields at a Mösbauer Sn119 impurity diluted at the R site (R=Gd,Tb,Dy,Ho,Er) of the cubic Laves phase intermetallic compounds RCo2. One considers that the magnetic hyperfine fields have two contributions, (i) the contribution from R ions, calculated via an extended Daniel-Friedel [J. Phys. Chem. Solids 24, 1601 (1963)] model, and (ii) the contribution from the induced magnetic moments arising from the Co neighboring sites. Our calculated self-consistent total magnetic hyperfine fields are in a good agreement with recent experimental data.

The optical pumping of alkali atoms using coherent radiation from semi-conductor injection lasers and incoherent radiation from resonance lamps

NASA Technical Reports Server (NTRS)

Singh, G.

1973-01-01

An experimental study for creating population differences in the ground states of alkali atoms (Cesium 133) is presented. Studies made on GaAs-junction lasers and the achievement of population inversions among the hyperfine levels in the ground state of Cs 133 by optically pumping it with radiation from a GaAs diode laser. Laser output was used to monitor the populations in the ground state hyperfine levels as well as to perform the hyperfine pumping. A GaAs laser operated at about 77 K was used to scan the 8521 A line of Cs 133. Experiments were performed both with neon-filled and with paraflint-coated cells containing the cesium vapor. Investigations were also made for the development of the triple resonance coherent pulse technique and for the detection of microwave induced hyperfine trasistions by destroying the phase relationships produced by a radio frequency pulse. A pulsed cesium resonance lamp developed, and the lamp showed clean and reproducible switching characteristics.

Material science and solid state physics studies with positive muon spin precession. [fe(a1) alloys

NASA Technical Reports Server (NTRS)

Stronach, C. E.

1979-01-01

The hyperfine field on the muon, B sub hf, at interstitial sites in dilute Fe(Al) alloys was measured for four different concentrations of Al and as a function of temperature by the muon spin rotation method. The magnitude of B sub hf, which is negative, decreases at rates ranging from 0.09 + or - 0.03% per at.% Al at 200 K to an asymptotic limit of 0.35 + or - far above 440 K. This behavior shows that sites near the Al impurity are weakly repulsive to the muon, with an interaction potential of 13 + or - 3 meV. In order to fit the temperature dependence of the hyperfine field, it is necessary to hypothesize the existence of a small concentration of unidentified defects, possibly dislocations, which are attractive to the muon. Although the Al impurity acts as a non-magnetic hole in the Fe lattice, the observed decrease in B sub hf is only 35% of the decrease in the bulk magnetization. It is concluded that B sub hf is determined mainly by the enhanced screening of conduction electrons in Fe and Fe(Al). Since the influence of the Al impurity on the neighboring Fe monents is very small, most of the change in B sub hf is therefore attributed to the increase in conduction electron polarization of the Al impurity.

Electronic and Magnetic Structures, Magnetic Hyperfine Fields and Electric Field Gradients in UX3 (X = In, Tl, Pb) Intermetallic Compounds

NASA Astrophysics Data System (ADS)

Khan, Sajid; Yazdani-Kachoei, Majid; Jalali-Asadabadi, Saeid; Farooq, Muhammad Bilal; Ahmad, Iftikhar

2018-02-01

Cubic uranium compounds such as UX3 (X is a non-transition element of groups IIIA or IVA) exhibit highly diverse magnetic properties, including Pauli paramagnetism, spin fluctuation and anti-ferromagnetism. In the present paper, we explore the structural, electronic and magnetic properties as well as the hyperfine fields (HFFs) and electric field gradients (EFGs) with quadrupole coupling constant of UX3 (X = In, Tl, Pb) compounds using local density approximation, Perdew-Burke-Ernzerhof parametrization of generalized gradient approximation (PBE-GGA) including the Hubbard U parameter (GGA + U), a revised version of PBE-GGA that improves equilibrium properties of densely packed solids and their surfaces (PBEsol-GGA), and a hybrid functional (HF-PBEsol). The spin orbit-coupling calculations have been added to investigate the relativistic effect of electrons in these materials. The comparison between the experimental parameters and our calculated structural parameters we confirm the consistency and effectiveness of our theoretical tools. The computed magnetic moments show that magnetic moment increases from indium to lead in the UX3 family, and all these compounds are antiferromagnetic in nature. The EFGs and HFFs, as well as the quadrupole coupling constant of UX3 (X = In, Tl, Pb), are discussed in detail. These properties primarily originate from f and p states of uranium and post-transition sites.

Fingerprints of single nuclear spin energy levels using STM - ENDOR

NASA Astrophysics Data System (ADS)

Manassen, Yishay; Averbukh, Michael; Jbara, Moamen; Siebenhofer, Bernhard; Shnirman, Alexander; Horovitz, Baruch

2018-04-01

We performed STM-ENDOR experiments where the intensity of one of the hyperfine components detected in ESR-STM is recorded while an rf power is irradiated into the tunneling junction and its frequency is swept. When the latter frequency is near a nuclear transition a dip in ESR-STM signal is observed. This experiment was performed in three different systems: near surface SiC vacancies where the electron spin is coupled to a next nearest neighbor 29Si nucleus; Cu deposited on Si(111)7x7 surface, where the unpaired electron of the Cu atom is coupled to the Cu nucleus (63Cu, 65Cu) and on Tempo molecules adsorbed on Au(111), where the unpaired electron is coupled to a Nitrogen nucleus (14N). While some of the hyperfine values are unresolved in the ESR-STM data due to linewidth we find that they are accurately determined in the STM-ENDOR data including those from remote nuclei, which are not detected in the ESR-STM spectrum. Furthermore, STM-ENDOR can measure single nuclear Zeeman frequencies, distinguish between isotopes through their different nuclear magnetic moments and detect quadrupole spectra. We also develop and solve a Bloch type equation for the coupled electron-nuclear system that facilitates interpretation of the data. The improved spectral resolution of STM - ENDOR opens many possibilities for nanometric scale chemical analysis.

Fingerprints of single nuclear spin energy levels using STM - ENDOR.

PubMed

Manassen, Yishay; Averbukh, Michael; Jbara, Moamen; Siebenhofer, Bernhard; Shnirman, Alexander; Horovitz, Baruch

2018-04-01

We performed STM-ENDOR experiments where the intensity of one of the hyperfine components detected in ESR-STM is recorded while an rf power is irradiated into the tunneling junction and its frequency is swept. When the latter frequency is near a nuclear transition a dip in ESR-STM signal is observed. This experiment was performed in three different systems: near surface SiC vacancies where the electron spin is coupled to a next nearest neighbor 29 Si nucleus; Cu deposited on Si(111)7x7 surface, where the unpaired electron of the Cu atom is coupled to the Cu nucleus ( 63 Cu, 65 Cu) and on Tempo molecules adsorbed on Au(111), where the unpaired electron is coupled to a Nitrogen nucleus ( 14 N). While some of the hyperfine values are unresolved in the ESR-STM data due to linewidth we find that they are accurately determined in the STM-ENDOR data including those from remote nuclei, which are not detected in the ESR-STM spectrum. Furthermore, STM-ENDOR can measure single nuclear Zeeman frequencies, distinguish between isotopes through their different nuclear magnetic moments and detect quadrupole spectra. We also develop and solve a Bloch type equation for the coupled electron-nuclear system that facilitates interpretation of the data. The improved spectral resolution of STM - ENDOR opens many possibilities for nanometric scale chemical analysis. Copyright © 2018 Elsevier Inc. All rights reserved.

The effect of fringe fields from patterned magnetic domains on the electroluminescence of organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Harmon, Nicholas J.; Wohlgennant, Markus; Flatté, Michael E.

2016-10-01

Large magnetic field effects, either in conduction or luminescence, have been observed in organic light-emitting diodes (OLEDs) for over a decade now. The physical processes are largely understood when exciton formation and recombination lead to the magnetic field effects. Recently, magnetic field effects in some co-evaporated blends have shown that exciplexes deliver even larger responses. In either case, the magnetic field effects arise from some spin-mixing mechanism and spin-selective processes in either the exciton formation or the exciplex recombination. Precise control of light output is not possible when the spin mixing is either due to hyper-fine fields or differences in the Lande g-factor. We theoretically examine the optical output when a patterned magnetic film is deposited near the OLED. The fringe fields from the magnetic layers supply an additionally source of spin mixing that can be easily controlled. In the absence of other spin mixing mechanisms, the luminescence from exciplexes can be modified by 300%. When other spin-mixing mechanisms are present, fringe fields from remanent magnetic states act as a means to either boost or reduce light emission from those mechanisms. Lastly, we examine the influence of spin decoherence on the optical output.

The electronic structure of iron in rhyolitic and basaltic glasses at high pressure

NASA Astrophysics Data System (ADS)

Solomatova, N. V.; Jackson, J. M.; Sturhahn, W.; Roskosz, M.

2016-12-01

The physical properties of silicate melts within the Earth's mantle affect the chemical and thermal evolution of the Earth's interior. To understand melting processes within the Earth, it is imperative to determine the structure of silicate melts at high pressure. It has been proposed that iron-bearing silicate melts may exist in the lower mantle just above the core-mantle boundary [1]. The behavior of iron in mantle melts is poorly understood, but can be experimentally approximated by iron-bearing silicate glasses. Previous studies have conflicting conclusions on whether iron in lower mantle silicate melts goes through a high-spin to low-spin transition [2-4]. Additionally, the average coordination environment of iron in glasses is poorly constrained. XANES experiments on basaltic glasses have demonstrated that both four and six-fold coordinated iron may exist in significant amounts regardless of oxidation state [5] while conventional Mössbauer experiments have observed five-fold coordinated Fe2+ with small amounts of four and six-fold coordinated Fe2+ [6]. In an attempt to resolve these discrepancies, we have measured the hyperfine parameters of iron-bearing rhyolitic glass up to 115 GPa and basaltic glass up to 92 GPa in a neon pressure medium using time-resolved synchrotron Mössbauer spectroscopy at the Advanced Photon Source (Argonne National Laboratory, IL). We observed changes in the hyperfine parameters likely due to coordination changes as a result of increasing pressure. Our results indicate that iron does not undergo a high-spin to low-spin transition within the pressure range investigated. Changes in the electronic configuration, such as the spin state of iron affects the compressibility and thermal properties of melts. With the assumption that silica glasses can be used to model structural behavior in silicate melts, our study predicts that iron in chemically-complex silica-rich melts in the lower mantle likely exists in a high-spin state. Select references: [1] Williams and Garnero, Science 273, 1528-1530 (1996). [2] Nomura et al., Nature 473, 199-202 (2011). [3] Gu et al., Geophys. Res. Lett. 39 (2012). [4] Mao et al., Am. Mineral. 99, 415-423 (2014). [5] Wilke et al., Chem. Geology 220, 143-161 (2005). [6] Cottrell and Kelley Earth Planet. Sci. Lett. 305, 270-282 (2011).

Molecular beam electric resonance study of KCN, K 13CN and KC 15N

NASA Astrophysics Data System (ADS)

van Vaals, J. J.; Leo Meerts, W.; Dymanus, A.

1984-08-01

The microwave spectra of the isotopic species K 13CN and KC 15N have been investigated by molecular beam electric resonance spectroscopy, using the seeded beam technique. For both isotopic species about 20 rotational transitions originating in the ground vibrational state were observed in the frequency range 9-38 GHz. The observed transitions were fitted to an asymmetric rotor model to determine the three rotational, as well as the five quartic and three sextic centrifugal distortion constants. The hyperfine spectrum of KCN has been unravelled with the help of microwave-microwave double-resonance techniques. One hundred and forty hyperfine transitions in 11 rotational transitions have been assigned. The hyperfine structures of K 13CN and KC 15N were also studied. For all three isotopic species the quadrupole coupling constants and some spin-rotation coupling constants could be deduced. The rotational constants of the 13C and 15N isotopically substituted species of potassium cyanide, combined with those of the normal isotopic species (determined more accurately in this work), allowed an accurate and unambiguous evaluation of the structure, which was confirmed to be T shaped. Both the effective structure of the ground vibrational state and the substitution structure were evaluated. The results for the effective structural parameters are r CN = 1.169(3) Å, r KC = 2.716(9) Å, and r KN = 2.549(9) Å. The values obtained for the principal hyperfine coupling constant eQqz(N), the angle between the CN axis and zN, and the bond length rCN indicate that in gaseous potassium cyanide the CN group can be considered as an almost unperturbed CN - ion.

Frequency-Comb Based Double-Quantum Two-Dimensional Spectrum Identifies Collective Hyperfine Resonances in Atomic Vapor Induced by Dipole-Dipole Interactions

NASA Astrophysics Data System (ADS)

Lomsadze, Bachana; Cundiff, Steven T.

2018-06-01

Frequency-comb based multidimensional coherent spectroscopy is a novel optical method that enables high-resolution measurement in a short acquisition time. The method's resolution makes multidimensional coherent spectroscopy relevant for atomic systems that have narrow resonances. We use double-quantum multidimensional coherent spectroscopy to reveal collective hyperfine resonances in rubidium vapor at 100 °C induced by dipole-dipole interactions. We observe tilted and elongated line shapes in the double-quantum 2D spectra, which have never been reported for Doppler-broadened systems. The elongated line shapes suggest that the signal is predominately from the interacting atoms that have a near zero relative velocity.

Electromagnetically induced absorption and transparency in degenerate two level systems of metastable Kr atoms and measurement of Landé g-factor

NASA Astrophysics Data System (ADS)

Kale, Y. B.; Tiwari, V. B.; Mishra, S. R.; Singh, S.; Rawat, H. S.

2016-12-01

We report electromagnetically induced absorption (EIA) and transparency (EIT) resonances of sub-natural linewidth in degenerate two level systems (DTLSs) of metastable 84Kr (84Kr*) and 83Kr (83Kr*) atoms. Using the spectrally narrow EIA signals obtained corresponding to the closed hyperfine transition 4p55s[3/2]2(F=13/2) to 4p55p[5/2]3(F‧ = 15 / 2) in 83Kr* atom, we have measured the Landé g-factor (gF) for the lower hyperfine level involved in this transition by application of small values of magnetic field of few Gauss.

Activities report in nuclear physics and particle acceleration

NASA Astrophysics Data System (ADS)

Jansen, J. F. W.; Demeijer, R. J.

1984-04-01

Research on nuclear resonances; charge transfer; breakup of light and heavy ions; reaction mechanisms of heavy ion collisions; high-spin states; and fundamental symmetries in weak interactions are outlined. Group theoretical methods applied to supersymmetries; phenomenological description of rotation-vibration coupling; a microscopic theory of collective variables; the binding energy of hydrogen adsorbed on stepped platinium; and single electron capture are discussed. Isotopes for nuclear medicine, for off-line nuclear spectroscopy work, and for the study of hyperfine interactions were produced.

Rotational spectra of the X 2Sigma(+) states of CaH and CaD

NASA Technical Reports Server (NTRS)

Frum, C. I.; Oh, J. J.; Cohen, E. A.; Pickett, H. M.

1993-01-01

The rotational spectra of the 2Sigma(2+) ground states of calcium monohydride and monodeuteride have been recorded in absorption between 250 and 700 GHz. The gas phase free radicals have been produced in a ceramic furnace by the reaction of elemental calcium with molecular hydrogen or deuterium in the presence of an electrical discharge. The molecular constants including the rotational constant, centrifugal distortion constants, spin-rotation constants, and magnetic hyperfine interaction constants have been extracted from the spectra.

Organic magnetoresistance based on hopping theory

NASA Astrophysics Data System (ADS)

Yang, Fu-Jiang; Xie, Shi-Jie

2014-09-01

For the organic magnetoresistance (OMAR) effect, we suggest a spin-related hopping of carriers (polarons) based on Marcus theory. The mobility of polarons is calculated with the master equation (ME) and then the magnetoresistance (MR) is obtained. The theoretical results are consistent with the experimental observation. Especially, the sign inversion of the MR under different driving bias voltages found in the experiment is predicted. Besides, the effects of molecule disorder, hyperfine interaction (HFI), polaron localization, and temperature on the MR are investigated.

Resonant quantum transitions in trapped antihydrogen atoms.

PubMed

Amole, C; Ashkezari, M D; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Capra, A; Cesar, C L; Charlton, M; Deller, A; Donnan, P H; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Humphries, A J; Isaac, C A; Jonsell, S; Kurchaninov, L; Little, A; Madsen, N; McKenna, J T K; Menary, S; Napoli, S C; Nolan, P; Olchanski, K; Olin, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sarid, E; Shields, C R; Silveira, D M; Stracka, S; So, C; Thompson, R I; van der Werf, D P; Wurtele, J S

2012-03-07

The hydrogen atom is one of the most important and influential model systems in modern physics. Attempts to understand its spectrum are inextricably linked to the early history and development of quantum mechanics. The hydrogen atom's stature lies in its simplicity and in the accuracy with which its spectrum can be measured and compared to theory. Today its spectrum remains a valuable tool for determining the values of fundamental constants and for challenging the limits of modern physics, including the validity of quantum electrodynamics and--by comparison with measurements on its antimatter counterpart, antihydrogen--the validity of CPT (charge conjugation, parity and time reversal) symmetry. Here we report spectroscopy of a pure antimatter atom, demonstrating resonant quantum transitions in antihydrogen. We have manipulated the internal spin state of antihydrogen atoms so as to induce magnetic resonance transitions between hyperfine levels of the positronic ground state. We used resonant microwave radiation to flip the spin of the positron in antihydrogen atoms that were magnetically trapped in the ALPHA apparatus. The spin flip causes trapped anti-atoms to be ejected from the trap. We look for evidence of resonant interaction by comparing the survival rate of trapped atoms irradiated with microwaves on-resonance to that of atoms subjected to microwaves that are off-resonance. In one variant of the experiment, we detect 23 atoms that survive in 110 trapping attempts with microwaves off-resonance (0.21 per attempt), and only two atoms that survive in 103 attempts with microwaves on-resonance (0.02 per attempt). We also describe the direct detection of the annihilation of antihydrogen atoms ejected by the microwaves.

Synthesis and magnetic properties of LiFePO4 substitution magnesium

NASA Astrophysics Data System (ADS)

Choi, Hyunkyung; Kim, Min Ji; Hahn, Eun Joo; Kim, Sam Jin; Kim, Chul Sung

2017-06-01

LiFe0.9Mg0.1PO4 sample was prepared by using a solid-state reaction method, and the temperature-dependent magnetic properties of the sample were studied. The X-ray diffraction (XRD) pattern showed an olivine-type orthorhombic structure with space group Pnma based on Rietveld refinement method. The effect of Mg substitution in antiferromagnetic LiFe0.9Mg0.1PO4 was investigated using a vibrating sample magnetometer (VSM) and Mössbauer spectroscopy. The temperature-dependence of the magnetization curves of LiFe0.9Mg0.1PO4 shows abnormal antiferromagnetic behavior with ordering temperature. Sudden changes in both the magnetic hyperfine field (Hhf) and its slope below 15 K suggest that magnetic phase transition associated to the abrupt occurrence of spin-reorientation. The Néel temperature (TN) and spin-reorientation temperature (TS) of LiFe0.9Mg0.1PO4 are lower than those of pure LiFePO4 (TN = 51 K, TS = 23 K). This is due to the Fe-O-Fe superexchange interaction being larger than that of the Fe-O-Mg link. Also, we have confirmed a change in the electric quadrupole splitting (ΔEQ) by the spin-orbit coupling effect and the shape of Mössbauer spectrum has provided the evidence for TS and a strong crystalline field. We have found that Mg ions in LiFe0.9Mg0.1PO4 induce an asymmetric charge density due to the presence of Mg2+ ions at the FeO6 octahedral sites.

Experimental Studies of the NaK 3^1Π and 1^3Δ States

NASA Astrophysics Data System (ADS)

Prodan, I. D.; Marks, A.; Sibbach, L.; Laub, E.; Mazsa, I.; Webb, S.; La Civita, J.; Galle, E.; Jabbour, Z. J.; Namiotka, R. K.; Morgus, T.; Huennekens, J.; Li, Li

2000-06-01

We report the results of optical-optical double resonance experiments designed to study the 3^1Π and 1^3Δ states of NaK. In the first step, a narrow band cw dye laser (PUMP) was tuned to excite a particular 2(A)^1Σ^+(v_A, J') level [or 2(A)^1Σ^+(v_A, J') ~ 1(b)^3Π(v_b, J') mixed level], and its frequency was then fixed. A second narrow band tunable cw Ti:Sapphire laser (PROBE) was then scanned over transitions to various 3^1Π(v_Π, J) [or 1^3Δ(v_Δ, J)] levels while 3^1Π arrow 1(X)^1Σ^+ violet fluorescence [or collision-induced ^3Λ arrow 1(a)^3Σ^+ green fluorescence] was monitored. The Doppler-free signals accurately map the 3^1Π and 1^3Δ state ro-vibrational energy levels. These energy levels were then fit to Dunham expansions to provide experimental molecular constants, allowing the construction of RKR potential curves that have been compared to recent theoretical calculations. Comparison between observed and calculated Franck-Condon factors was used to determine variation of the 3^1Πarrow1(X)^1Σ^+ transition dipole moment with internuclear separation. A deperturbation analysis of the 1^3Δ state was performed to determine the spin-orbit constant for that state. The 1^3Δ state hyperfine structure, due to the Fermi contact interaction between the electron spin and the sodium atom nuclear spin, was also studied.

The Radical Pair Mechanism and the Avian Chemical Compass: Quantum Coherence and Entanglement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yiteng; Kais, Sabre; Berman, Gennady Petrovich

2015-02-02

We review the spin radical pair mechanism which is a promising explanation of avian navigation. This mechanism is based on the dependence of product yields on 1) the hyperfine interaction involving electron spins and neighboring nuclear spins and 2) the intensity and orientation of the geomagnetic field. One surprising result is that even at ambient conditions quantum entanglement of electron spins can play an important role in avian magnetoreception. This review describes the general scheme of chemical reactions involving radical pairs generated from singlet and triplet precursors; the spin dynamics of the radical pairs; and the magnetic field dependence ofmore » product yields caused by the radical pair mechanism. The main part of the review includes a description of the chemical compass in birds. We review: the general properties of the avian compass; the basic scheme of the radical pair mechanism; the reaction kinetics in cryptochrome; quantum coherence and entanglement in the avian compass; and the effects of noise. We believe that the quantum avian compass can play an important role in avian navigation and can also provide the foundation for a new generation of sensitive and selective magnetic-sensing nano-devices.« less

Preparation and properties of a monomeric high-spin Mn(V)-oxo complex.

PubMed

Taguchi, Taketo; Gupta, Rupal; Lassalle-Kaiser, Benedikt; Boyce, David W; Yachandra, Vittal K; Tolman, William B; Yano, Junko; Hendrich, Michael P; Borovik, A S

2012-02-01

Oxomanganese(V) species have been implicated in a variety of biological and synthetic processes, including their role as a key reactive center within the oxygen-evolving complex in photosynthesis. Nearly all mononuclear Mn(V)-oxo complexes have tetragonal symmetry, producing low-spin species. A new high-spin Mn(V)-oxo complex that was prepared from a well-characterized oxomanganese(III) complex having trigonal symmetry is now reported. Oxidation experiments with [FeCp(2)](+) were monitored with optical and electron paramagnetic resonance (EPR) spectroscopies and support a high-spin oxomanganese(V) complex formulation. The parallel-mode EPR spectrum has a distinctive S = 1 signal at g = 4.01 with a six-line hyperfine pattern having A(z) = 113 MHz. The presence of an oxo ligand was supported by resonance Raman spectroscopy, which revealed O-isotope-sensitive peaks at 737 and 754 cm(-1) assigned as a Fermi doublet centered at 746 cm(-1)(Δ(18)O = 31 cm(-1)). Mn Kβ X-ray emission spectra showed Kβ' and Kβ(1,3) bands at 6475.92 and 6490.50 eV, respectively, which are characteristic of a high-spin Mn(V) center. © 2012 American Chemical Society

Ab initio calculation of hyperfine splitting constants of molecules

NASA Astrophysics Data System (ADS)

Ohta, K.; Nakatsuji, H.; Hirao, K.; Yonezawa, T.

1980-08-01

Hyperfine splitting (hfs) constants of molecules, methyl, ethyl, vinyl, allyl, cyclopropyl, formyl, O3-, NH2, NO2, and NF2 radicals have been calculated by the pseudo-orbital (PO) theory, the unrestricted HF (UHF), projected UHF (PUHF) and single excitation (SE) CI theories. The pseudo-orbital (PO) theory is based on the symmetry-adapted-cluster (SAC) expansion proposed previously. Several contractions of the Gaussian basis sets of double-zeta accuracy have been examined. The UHF results were consistently too large to compare with experiments and the PUHF results were too small. For molecules studied here, the PO theory and SECI theory gave relatively close results. They were in fair agreement with experiments. The first-order spin-polarization self-consistency effect, which was shown to be important for atoms, is relatively small for the molecules. The present result also shows an importance of eliminating orbital-transformation dependence from conventional first-order perturbation calculations. The present calculations have explained well several important variations in the experimental hfs constants.

Hyperfine field, electric field gradient, quadrupole coupling constant and magnetic properties of challenging actinide digallide

NASA Astrophysics Data System (ADS)

Khan, Sajid; Yazdani-Kachoei, M.; Jalali-Asadabadi, S.; Ahmad, Iftikhar

2017-12-01

In this paper, we explore the structural and magnetic properties as well as electric field gradient (EFG), hyperfine field (HFF) and quadrupole coupling constant in actinide digallide AcGa2 (Ac = U, Np, Pu) using LDA, GGA, LDA+U, GGA+U and hybrid functional with Wu-Cohen Generalized Gradient approximation HF-WC. Relativistic effects of the electrons are considered by including spin-orbit coupling. The comparison of the calculated structural parameters and magnetic properties with the available experimental results confirms the consistency and hence effectiveness of our theoretical tools. The calculated magnetic moments demonstrate that UGa2 and NpGa2 are ferromagnetic while PuGa2 is antiferromagnetic in nature. The EFG of AcGa2 is reported for the first time. The HFF, EFG and quadrupole coupling constant in AcGa2 (Ac = U, Np, Pu) are mainly originated from f-f and p-p contributions of Ac atom and p-p contribution of Ga atom.

Hyperfine induced transition probabilities from 4{f}^{14}5s5p{}^{3}{{\\rm{P}}}_{0,2}^{o} states in Sm-like ions

NASA Astrophysics Data System (ADS)

Zhou, Fuyang; Li, Jiguang; Qu, Yizhi; Wang, Jianguo

2017-11-01

The hyperfine induced 4{f}145s5p{}3{{{P}}}0,2o-4{f}145{s}2{}1{{{S}}}0 transition probabilities for highly charged Sm-like ions are calculated within the framework of the multiconfiguration Dirac-Hartree-Fock method. Electron correlation, the Breit interaction and quantum electrodynamical effects are taken into account. For ions ranging from Z = 79 to Z=94,4{f}145s5p{}3{{{P}}}0o is the first excited state, and the hyperfine induced transition (HIT) is a dominant decay channel. For the 4{f}145s5p{}3{{{P}}}2o state, the HIT rates of Sm-like ions with Z=82-94 are reported as well as the magnetic dipole (M1) {}3{{{P}}}2o-{}3{{{P}}}1o, the electric quadrupole (E2) {}3{{{P}}}2o-{}3{{{P}}}0,1o, and the magnetic quadrupole (M2) {}3{{{P}}}2o-{}1{{{S}}}0 transition probabilities. It is found that M1 transition from the 4{f}145s5p{}3{{{P}}}2o state is the most important decay channel in this range on Z≥slant 82.

CNOT sequences for heterogeneous spin qubit architectures in a noisy environment

NASA Astrophysics Data System (ADS)

Ferraro, Elena; Fanciulli, Marco; de Michielis, Marco

Explicit CNOT gate sequences for two-qubits mixed architectures are presented in view of applications for large-scale quantum computation. Different kinds of coded spin qubits are combined allowing indeed the favorable physical properties of each to be employed. The building blocks for such composite systems are qubit architectures based on the electronic spin in electrostatically defined semiconductor quantum dots. They are the single quantum dot spin qubit, the double quantum dot singlet-triplet qubit and the double quantum dot hybrid qubit. The effective Hamiltonian models expressed by only exchange interactions between pair of electrons are exploited in different geometrical configurations. A numerical genetic algorithm that takes into account the realistic physical parameters involved is adopted. Gate operations are addressed by modulating the tunneling barriers and the energy offsets between different couple of quantum dots. Gate infidelities are calculated considering limitations due to unideal control of gate sequence pulses, hyperfine interaction and unwanted charge coupling. Second affiliation: Dipartimento di Scienza dei Materiali, University of Milano Bicocca, Via R. Cozzi, 55, 20126 Milano, Italy.

Electron Spin Polarization Transfer to ortho-H2 by Interaction of para-H2 with Paramagnetic Species: A Key to a Novel para → ortho Conversion Mechanism.

PubMed

Terenzi, Camilla; Bouguet-Bonnet, Sabine; Canet, Daniel

2015-05-07

We report that at ambient temperature and with 100% enriched para-hydrogen (p-H2) dissolved in organic solvents, paramagnetic spin catalysis of para → ortho hydrogen conversion is accompanied at the onset by a negative ortho-hydrogen (o-H2) proton NMR signal. This novel finding indicates an electron spin polarization transfer, and we show here that this can only occur if the H2 molecule is dissociated upon its transient adsorption by the paramagnetic catalyst. Following desorption, o-H2 is created until the thermodynamic equilibrium is reached. A simple theory confirms that in the presence of a static magnetic field, the hyperfine coupling between unpaired electrons and nuclear spins is responsible for the observed polarization transfer. Owing to the negative electron gyromagnetic ratio, this explains the experimental results and ascertains an as yet unexplored mechanism for para → ortho conversion. Finally, we show that the recovery of o-H2 magnetization toward equilibrium can be simply modeled, leading to the para → ortho conversion rate.

Theoretical research of the spin-Hamiltonian parameters for two rhombic W5+ centers in KTiOPO4 (KTP) crystal through a two-mechanism model

NASA Astrophysics Data System (ADS)

Mei, Yang; Chen, Bo-Wei; Wei, Chen-Fu; Zheng, Wen-Chen

2016-09-01

The high-order perturbation formulas based on the two-mechanism model are employed to calculate the spin-Hamiltonian parameters (g factors gi and hyperfine structure constants Ai, where i=x, y, z) for two approximately rhombic W5+ centers in KTiOPO4 (KTP) crystal. In the model, both the widely-applied crystal-field (CF) mechanism concerning the interactions of CF excited states with the ground state and the generally-neglected charge-transfer (CT) mechanism concerning the interactions of CT excited states with the ground state are included. The calculated results agree with the experimental values, and the signs of constants Ai are suggested. The calculations indicate that (i) for the high valence state dn ions in crystals, the contributions to spin-Hamiltonian parameters should take into account both the CF and CT mechanisms and (ii) the large g-shifts |Δgi | (=|gi-ge |, where ge≈ 2.0023) for W5+ centers in crystals are due to the large spin-orbit parameter of free W5+ ion.

Structure and magnetic behaviors of melt-spun SmFeSiB ribbons and their nitrides

NASA Astrophysics Data System (ADS)

Luo, Y.; Zhang, K.; Li, K. S.; Yu, D. B.; Ling, J. J.; Men, K.; Dou, Q. Y.; Yan, W. L.; Xie, J. J.; Yang, Y. F.

2016-05-01

SmFe9.3+xSi0.2B0.1 (x=0, 0.5, 1.0) ribbons and their nitrides were prepared by melt-spinning, followed by annealing and subsequent nitriding. The structure and magnetic properties have been investigated by means of powder X-ray diffraction, vibrating sample magnetometer and Mossbauer spectroscopy. Rietveld analysis shows that the augment of Fe content gives rise to an increase of the c/a ratio and cell volume. The increasing amount of Fe atoms occupying the 2e sites results in the change of initial structure. It is indicated that the isomer shift of 3g and 6l atom remains quasi-constant while the 2e atom shows a noticeable increase with the increase of iron content, which further conforms the preferential occupation of excessive Fe atoms at this site. Consistent with Tc, the mean hyperfine field 〈Bhf〉 has the highest value of 25.7 T when x=0.5. The hyperfine fields at different Fe sites follow the order H2e>H3g>H6l. The highest curie temperature of 477.68 K and the hyperfine field of 25.7 T in the as-quenched ribbons were obtained when x=0.5. Meanwhile, the highest magnetic properties of Hcj=4.31 kOe, (BH)m=3.5 MGOe in the nitride powders were found.

Diffusion studies on permeable nitroxyl spin probes through bilayer lipid membranes: A low frequency ESR study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meenakumari, V.; Benial, A. Milton Franklin, E-mail: miltonfranklin@yahoo.com; Utsumi, Hideo

2015-06-24

Electron spin resonance (ESR) studies were carried out for permeable 2mM {sup 14}N-labeled deutrated 3 Methoxy carbonyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl (MC-PROXYL) in pure water and 1mM, 2mM, 3mM, 4mM concentration of 14N-labeled deutrated MC-PROXYL in 400mM concentration of liposomal solution by using a 300 MHz ESR spectrometer. The ESR parameters such as linewidth, hyperfine coupling constant, g-factor, partition parameter and permeability were reported for these samples. The line broadening was observed for the nitroxyl spin probe in the liposomal solution. The line broadening indicates that the high viscous nature of the liposomal solution. The partition parameter and permeability values indicate the maximum diffusion ofmore » nitroxyl spin probes in the bilayer lipid membranes at 2 mM concentration of nitroxyl radical. This study illustrates that ESR can be used to differentiate between the intra and extra- membrane water by loading the liposome vesicles with a lipid-permeable nitroxyl spin probe. From the ESR results, the spin probe concentration was optimized as 2mM in liposomal solution for ESR phantom studies/imaging, invivo and invitro experiments.« less

Magnetic defects in chemically converted graphene nanoribbons: electron spin resonance investigation

NASA Astrophysics Data System (ADS)

Singamaneni, Srinivasa Rao; Stesmans, Andre; van Tol, Johan; Kosynkin, D. V.; Tour, James M.

2014-04-01

Electronic spin transport properties of graphene nanoribbons (GNRs) are influenced by the presence of adatoms, adsorbates and edge functionalization. To improve the understanding of the factors that influence the spin properties of GNRs, local (element) spin-sensitive techniques such as electron spin resonance (ESR) spectroscopy are important for spintronics applications. Here, we present results of multi-frequency continuous wave (CW), pulse and hyperfine sublevel correlation (HYSCORE) ESR spectroscopy measurements performed on oxidatively unzipped graphene nanoribbons (GNRs), which were subsequently chemically converted (CCGNRs) with hydrazine. ESR spectra at 336 GHz reveal an isotropic ESR signal from the CCGNRs, of which the temperature dependence of its line width indicates the presence of localized unpaired electronic states. Upon functionalization of CCGNRs with 4-nitrobenzene diazonium tetrafluoroborate, the ESR signal is found to be 2 times narrower than that of pristine ribbons. NH3 adsorption/desorption on CCGNRs is shown to narrow the signal, while retaining the signal intensity and g value. The electron spin-spin relaxation process at 10 K is found to be characterized by slow (163 ns) and fast (39 ns) components. HYSCORE ESR data demonstrate the explicit presence of protons and 13C atoms. With the provided identification of intrinsic point magnetic defects such as proton and 13C has been reported, which are roadblocks to spin travel in graphene-based materials, this work could help in advancing the present fundamental understanding on the edge-spin (or magnetic)-based transport properties of CCGNRs.

Discrimination between spin-dependent charge transport and spin-dependent recombination in π-conjugated polymers by correlated current and electroluminescence-detected magnetic resonance

NASA Astrophysics Data System (ADS)

Kavand, Marzieh; Baird, Douglas; van Schooten, Kipp; Malissa, Hans; Lupton, John M.; Boehme, Christoph

2016-08-01

Spin-dependent processes play a crucial role in organic electronic devices. Spin coherence can give rise to spin mixing due to a number of processes such as hyperfine coupling, and leads to a range of magnetic field effects. However, it is not straightforward to differentiate between pure single-carrier spin-dependent transport processes which control the current and therefore the electroluminescence, and spin-dependent electron-hole recombination which determines the electroluminescence yield and in turn modulates the current. We therefore investigate the correlation between the dynamics of spin-dependent electric current and spin-dependent electroluminescence in two derivatives of the conjugated polymer poly(phenylene-vinylene) using simultaneously measured pulsed electrically detected (pEDMR) and optically detected (pODMR) magnetic resonance spectroscopy. This experimental approach requires careful analysis of the transient response functions under optical and electrical detection. At room temperature and under bipolar charge-carrier injection conditions, a correlation of the pEDMR and the pODMR signals is observed, consistent with the hypothesis that the recombination currents involve spin-dependent electronic transitions. This observation is inconsistent with the hypothesis that these signals are caused by spin-dependent charge-carrier transport. These results therefore provide no evidence that supports earlier claims that spin-dependent transport plays a role for room-temperature magnetoresistance effects. At low temperatures, however, the correlation between pEDMR and pODMR is weakened, demonstrating that more than one spin-dependent process influences the optoelectronic materials' properties. This conclusion is consistent with prior studies of half-field resonances that were attributed to spin-dependent triplet exciton recombination, which becomes significant at low temperatures when the triplet lifetime increases.

Ultrafast time scale X-rotation of cold atom storage qubit using Rubidium clock states

NASA Astrophysics Data System (ADS)

Song, Yunheung; Lee, Han-Gyeol; Kim, Hyosub; Jo, Hanlae; Ahn, Jaewook

2017-04-01

Ultrafast-time-scale optical interaction is a local operation on the electronic subspace of an atom, thus leaving its nuclear state intact. However, because atomic clock states are maximally entangled states of the electronic and nuclear degrees of freedom, their entire Hilbert space should be accessible only with local operations and classical communications (LOCC). Therefore, it may be possible to achieve hyperfine qubit gates only with electronic transitions. Here we show an experimental implementation of ultrafast X-rotation of atomic hyperfine qubits, in which an optical Rabi oscillation induces a geometric phase between the constituent fine-structure states, thus bringing about the X-rotation between the two ground hyperfine levels. In experiments, cold atoms in a magneto-optical trap were controlled with a femtosecond laser pulse from a Ti:sapphire laser amplifier. Absorption imaging of the as-controlled atoms initially in the ground hyperfine state manifested polarization dependence, strongly agreeing with the theory. The result indicates that single laser pulse implementations of THz clock speed qubit controls are feasible for atomic storage qubits. Samsung Science and Technology Foundation [SSTF-BA1301-12].

The millimeter and submillimeter rotational spectrum of the MgCN radical (X (sup 2) Sigma(+))

NASA Technical Reports Server (NTRS)

Anderson, M. A.; Steimle, T. C.; Ziurys, L. M.

1994-01-01

The pure rotational spectrum of the MgCN radical has been recorded in the laboratory using millimeter/submillimeter direct absorption spectroscopy. Twenty-seven rotational transitions of the species were observed in the range 101-376 GHz and indicate that the molecule is linear with a (sup 2)Sigma(+) ground electronic state, as predicted by theory. Spin rotation interactions were resolved in the spectra, but no hyperfine splittings were observed, which would originate with the nitrogen nuclear spin. The rotational and fine-structure constants were determined for this radical from a nonlinear least-squares fit to the data using a (sup 2)Sigma Hamiltonian. MgCN is of astrophysical interest because it is the metastable isomer of MgNC, which recently has been detected toward IRC +10216

Muonium in Stishovite: Implications for the Possible Existence of Neutral Atomic Hydrogen in the Earth's Deep Mantle

PubMed Central

Funamori, Nobumasa; Kojima, Kenji M.; Wakabayashi, Daisuke; Sato, Tomoko; Taniguchi, Takashi; Nishiyama, Norimasa; Irifune, Tetsuo; Tomono, Dai; Matsuzaki, Teiichiro; Miyazaki, Masanori; Hiraishi, Masatoshi; Koda, Akihiro; Kadono, Ryosuke

2015-01-01

Hydrogen in the Earth's deep interior has been thought to exist as a hydroxyl group in high-pressure minerals. We present Muon Spin Rotation experiments on SiO2 stishovite, which is an archetypal high-pressure mineral. Positive muon (which can be considered as a light isotope of proton) implanted in stishovite was found to capture electron to form muonium (corresponding to neutral hydrogen). The hyperfine-coupling parameter and the relaxation rate of spin polarization of muonium in stishovite were measured to be very large, suggesting that muonium is squeezed in small and anisotropic interstitial voids without binding to silicon or oxygen. These results imply that hydrogen may also exist in the form of neutral atomic hydrogen in the deep mantle. PMID:25675890

Collaborative Research: Polymeric Multiferroics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, Shenqiang

2017-04-20

The goal of this project is to investigate room temperature magnetism and magnetoelectric coupling of polymeric multiferroics. A new family of molecular charge-transfer crystals has been emerged as a fascinating opportunity for the development of all-organic electrics and spintronics due to its weak hyperfine interaction and low spin-orbit coupling; nevertheless, direct observations of room temperature magnetic spin ordering have yet to be accomplished in organic charge-transfer solids. Furthermore, room temperature magnetoelectric coupling effect hitherto known multiferroics, is anticipated in organic donor-acceptor complexes because of magnetic field effects on charge-transfer dipoles, yet this is also unexplored. The PI seeks to fundamentalmore » understanding of the control of organic crystals to demonstrate and explore room temperature multiferroicity. The experimental results have been verified through the theoretical modeling.« less

Nanoscale cluster dynamics in the martensitic phase of Ni-Mn-Sn shape-memory alloys

NASA Astrophysics Data System (ADS)

Hoch, Michael; Yuan, Shaojie; Kuhns, Phillip; Reyes, Arneil; Brooks, James; Phelan, Daniel; Srivastava, Vijay; James, Richard; Leighton, Chris

2015-03-01

The martensitic phases of Ni-Mn-Sn magnetic shape memory alloys exhibit interesting low temperature magnetic properties, including intrinsic superparamagnetism and exchange bias effects, which have previously been rationalized in terms of spin clusters. We show here that spin-echo NMR, involving 55Mn hyperfine fields, permits ferromagnetic and antiferromagnetic nanoregions to be directly identified in these materials and yields estimates of their size distributions. Nuclear relaxation rate measurements, made as a function of temperature, provide information on both the dynamics and on the electronic structure of the nanoregions. The relaxation rates are analyzed using a combination of Redfield and Korringa mechanisms, the Korringa procedure providing information on the density of states at the Fermi level. Results will be presented for a number of these alloys. DMR-1309463.

Muonium in Stishovite: Implications for the Possible Existence of Neutral Atomic Hydrogen in the Earth's Deep Mantle

NASA Astrophysics Data System (ADS)

Funamori, Nobumasa; Kojima, Kenji M.; Wakabayashi, Daisuke; Sato, Tomoko; Taniguchi, Takashi; Nishiyama, Norimasa; Irifune, Tetsuo; Tomono, Dai; Matsuzaki, Teiichiro; Miyazaki, Masanori; Hiraishi, Masatoshi; Koda, Akihiro; Kadono, Ryosuke

2015-02-01

Hydrogen in the Earth's deep interior has been thought to exist as a hydroxyl group in high-pressure minerals. We present Muon Spin Rotation experiments on SiO2 stishovite, which is an archetypal high-pressure mineral. Positive muon (which can be considered as a light isotope of proton) implanted in stishovite was found to capture electron to form muonium (corresponding to neutral hydrogen). The hyperfine-coupling parameter and the relaxation rate of spin polarization of muonium in stishovite were measured to be very large, suggesting that muonium is squeezed in small and anisotropic interstitial voids without binding to silicon or oxygen. These results imply that hydrogen may also exist in the form of neutral atomic hydrogen in the deep mantle.

Organic-inorganic proximity effect in the magneto-conductance of vertical organic field effect transistors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khachatryan, B.; Devir-Wolfman, A. H.; Ehrenfreund, E., E-mail: eitane@technion.ac.il

Vertical organic field effect transistors having a patterned source electrode and an a-SiO{sub 2} insulation layer show high performance as a switching element with high transfer characteristics. By measuring the low field magneto-conductance under ambient conditions at room temperature, we show here that the proximity of the inorganic a-SiO{sub 2} insulation to the organic conducting channel affects considerably the magnetic response. We propose that in n-type devices, electrons in the organic conducting channel and spin bearing charged defects in the inorganic a-SiO{sub 2} insulation layer (e.g., O{sub 2} = Si{sup +·}) form oppositely charged spin pairs whose singlet-triplet spin configurations are mixedmore » through the relatively strong hyperfine field of {sup 29}Si. By increasing the contact area between the insulation layer and the conducting channel, the ∼2% magneto-conductance response may be considerably enhanced.« less

Angstrom-Resolution Magnetic Resonance Imaging of Single Molecules via Wave-Function Fingerprints of Nuclear Spins

NASA Astrophysics Data System (ADS)

Ma, Wen-Long; Liu, Ren-Bao

2016-08-01

Single-molecule sensitivity of nuclear magnetic resonance (NMR) and angstrom resolution of magnetic resonance imaging (MRI) are the highest challenges in magnetic microscopy. Recent development in dynamical-decoupling- (DD) enhanced diamond quantum sensing has enabled single-nucleus NMR and nanoscale NMR. Similar to conventional NMR and MRI, current DD-based quantum sensing utilizes the "frequency fingerprints" of target nuclear spins. The frequency fingerprints by their nature cannot resolve different nuclear spins that have the same noise frequency or differentiate different types of correlations in nuclear-spin clusters, which limit the resolution of single-molecule MRI. Here we show that this limitation can be overcome by using "wave-function fingerprints" of target nuclear spins, which is much more sensitive than the frequency fingerprints to the weak hyperfine interaction between the targets and a sensor under resonant DD control. We demonstrate a scheme of angstrom-resolution MRI that is capable of counting and individually localizing single nuclear spins of the same frequency and characterizing the correlations in nuclear-spin clusters. A nitrogen-vacancy-center spin sensor near a diamond surface, provided that the coherence time is improved by surface engineering in the near future, may be employed to determine with angstrom resolution the positions and conformation of single molecules that are isotope labeled. The scheme in this work offers an approach to breaking the resolution limit set by the "frequency gradients" in conventional MRI and to reaching the angstrom-scale resolution.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mao, Zhu; Wang, Fan; Lin, Jung-Fu

In this study, we performed synchrotron X-ray diffraction (XRD) and Mössbauer spectroscopy (SMS) measurements on two single-crystal bridgmanite samples [ Embedded Image and Embedded Image ] to investigate the combined effect of Fe and Al on the hyperfine parameters, lattice parameters, and equation of state (EoS) of bridgmanite up to 130 GPa. Our SMS results show that Fe2+ and Fe3+ in Bm6 and Al-Bm11 are predominantly located in the large pseudo-dodecahedral sites (A-site) at lower-mantle pressures. The observed drastic increase in the hyperfine quadrupole splitting (QS) between 13 and 32 GPa can be associated with an enhanced local distortion ofmore » the A-site Fe2+ in Bm6. In contrast to Bm6, the enhanced lattice distortion and the presence of extremely high QS values of Fe2+ are not observed in Al-Bm11 at high pressures. Our results here support the notion that the occurrence of the extremely high QS component of approximately 4 mm/s in bridgmanite is due to the lattice distortion in the high-spin (HS) A-site Fe2+, instead of the occurrence of the intermediate-spin state. Both A-site Fe2+ and Fe3+ in Bm6 and Al-Bm11 remain in the HS state at lower-mantle pressures. Together with XRD results, we present the first experimental evidence that the enhanced lattice distortion of A-site Fe2+ does not cause any detectable variation in the EoS parameters, but is associated with anomalous variations in the bond length, tilting angle, and shear strain in the octahedra of Bm6. Analysis of the obtained EoS parameters of bridgmanite at lower-mantle pressures indicates that the substitution of Fe in bridgmanite will cause an enhanced density and a reduced bulk sound velocity (VΦ), whereas the Al and Fe substitution has a reduced effect on density and a negligible effect on VΦ. These experimental results provide new insight into the correlation between lattice, hyperfine, and EoS parameters of bridgmanite in the Earth’s lower mantle.« less

Quantum Control and Entanglement of Spins in Silicon Carbide

NASA Astrophysics Data System (ADS)

Klimov, Paul

Over the past several decades silicon carbide (SiC) has matured into a versatile material platform for high-power electronics and optoelectronic and micromechanical devices. Recent advances have also established SiC as a promising host for quantum technologies based on the spin of intrinsic defects, with the potential of leveraging existing device fabrication protocols alongside solid-state quantum control. Among these defects are the divacancies and related color centers, which have ground-state electron-spin triplets with coherence times as long as one millisecond and built-in optical interfaces operating near the telecommunication wavelengths. This rapidly developing field has prompted research into the SiC material host to understand how defect-bound electron spins interact with their surrounding nuclear spin bath. Although nuclear spins are a major source of decoherence in color-center spin systems, they are also a valuable resource since they can have coherence times that are orders of magnitude longer than electron spins. In this talk I will discuss our recent efforts to interface defect-bound electron spins in SiC with the nuclear spins of naturally occurring 29Si and 13C isotopic defects. I will discuss how the hyperfine interaction can be used to strongly initialize them, to coherently control them, to read them out, and to produce genuine electron-nuclear ensemble entanglement, all at ambient conditions. These demonstrations motivate further research into spins in SiC for prospective quantum technologies. In collaboration with A. Falk, D. Christle, K. Miao, H. Seo, V. Ivady, A. Gali, G. Galli, and D. D. Awschalom. This research was supported by the AFOSR, the NSF DMR-1306300, and the NSF Materials Research Science and Engineering Center.

Towards quantum networks of single spins: analysis of a quantum memory with an optical interface in diamond.

PubMed

Blok, M S; Kalb, N; Reiserer, A; Taminiau, T H; Hanson, R

2015-01-01

Single defect centers in diamond have emerged as a powerful platform for quantum optics experiments and quantum information processing tasks. Connecting spatially separated nodes via optical photons into a quantum network will enable distributed quantum computing and long-range quantum communication. Initial experiments on trapped atoms and ions as well as defects in diamond have demonstrated entanglement between two nodes over several meters. To realize multi-node networks, additional quantum bit systems that store quantum states while new entanglement links are established are highly desirable. Such memories allow for entanglement distillation, purification and quantum repeater protocols that extend the size, speed and distance of the network. However, to be effective, the memory must be robust against the entanglement generation protocol, which typically must be repeated many times. Here we evaluate the prospects of using carbon nuclear spins in diamond as quantum memories that are compatible with quantum networks based on single nitrogen vacancy (NV) defects in diamond. We present a theoretical framework to describe the dephasing of the nuclear spins under repeated generation of NV spin-photon entanglement and show that quantum states can be stored during hundreds of repetitions using typical experimental coupling parameters. This result demonstrates that nuclear spins with weak hyperfine couplings are promising quantum memories for quantum networks.

Use of rapid-scan EPR to improve detection sensitivity for spin-trapped radicals.

PubMed

Mitchell, Deborah G; Rosen, Gerald M; Tseitlin, Mark; Symmes, Breanna; Eaton, Sandra S; Eaton, Gareth R

2013-07-16

The short lifetime of superoxide and the low rates of formation expected in vivo make detection by standard continuous wave (CW) electron paramagnetic resonance (EPR) challenging. The new rapid-scan EPR method offers improved sensitivity for these types of samples. In rapid-scan EPR, the magnetic field is scanned through resonance in a time that is short relative to electron spin relaxation times, and data are processed to obtain the absorption spectrum. To validate the application of rapid-scan EPR to spin trapping, superoxide was generated by the reaction of xanthine oxidase and hypoxanthine with rates of 0.1-6.0 μM/min and trapped with 5-tert-butoxycarbonyl-5-methyl-1-pyrroline-N-oxide (BMPO). Spin trapping with BMPO to form the BMPO-OOH adduct converts the very short-lived superoxide radical into a more stable spin adduct. There is good agreement between the hyperfine splitting parameters obtained for BMPO-OOH by CW and rapid-scan EPR. For the same signal acquisition time, the signal/noise ratio is >40 times higher for rapid-scan than for CW EPR. Rapid-scan EPR can detect superoxide produced by Enterococcus faecalis at rates that are too low for detection by CW EPR. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Evidence for a dipolar-coupled AM system in carnosine in human calf muscle from in vivo 1H NMR spectroscopy

NASA Astrophysics Data System (ADS)

Schröder, Leif; Bachert, Peter

2003-10-01

Spin systems with residual dipolar couplings such as creatine, taurine, and lactate in skeletal muscle tissue exhibit first-order spectra in in vivo 1H NMR spectroscopy at 1.5 T because the coupled protons are represented by (nearly) symmetrized eigenfunctions. The imidazole ring protons (H2, H4) of carnosine are suspected to form also a coupled system. The ring's stiffness could enable a connectivity between these anisochronous protons with the consequence of second-order spectra at low field strength. Our purpose was to study whether this deviation from the Paschen-Back condition can be used to detect the H2-H4 coupling in localized 1D 1H NMR spectra obtained at 1.5 T (64 MHz) from the human calf in a conventional whole-body scanner. As for the hydrogen hyperfine interaction, a Breit-Rabi equation was derived to describe the transition from Zeeman to Paschen-Back regime for two dipolar-coupled protons. The ratio of the measurable coupling strength ( Sk) and the difference in resonance frequencies of the coupled spins (Δ ω) induces quantum-state mixing of various degree upon definition of an appropriate eigenbase of the coupled spin system. The corresponding Clebsch-Gordan coefficients manifest in characteristic energy corrections in the Breit-Rabi formula. These additional terms were used to define an asymmetry parameter of the line positions as a function of Sk and Δ ω. The observed frequency shifts of the resonances were found to be consistent with this parameter within the accuracy achievable in in vivo NMR spectroscopy. Thus it was possible to identify the origin of satellite peaks of H2, H4 and to describe this so far not investigated type of residual dipolar coupling in vivo.

Role of different types of subsystems in a doubly driven Λ system in 87Rb

NASA Astrophysics Data System (ADS)

Pandey, Kanhaiya

2013-04-01

The well-known Λ system using two ground-state hyperfine levels, Fg=1 and Fg=2 of 5S1/2, and one hyperfine level, Fe=2 of excited state of 5P3/2 of 87Rb, has been recently studied using two counterpropagating control lasers [Sapam Ranjita Chanu, Kanhaiya Pandey, and Vasant Natarajan, Europhys. Lett.EULEEJ0295-507510.1209/0295-5075/98/44009 98, 44009 (2012)]. The experiment shows conversion of electromagnetically induced transparency into electromagnetically induced absorption because the doubly driven Λ system forms various subsystems. We here present a detailed theoretical study of the different possible subsystems created by this configuration. We also explore the possibility of tuning the strength of individual subsystems by changing the polarization of the control lasers.

Studies of Landé gJ-factors of singly ionized lanthanum by laser-induced fluorescence spectroscopy

NASA Astrophysics Data System (ADS)

Werbowy, S.; Güney, C.; Windholz, L.

2016-08-01

Laser-induced fluorescence spectroscopy, using a cooled hollow cathode discharge lamp as source of ions, was used to observe the Zeeman splitting of 18 lines of La II in the wavelength range 629.6-680.9 nm, in external intermediate magnetic fields up to 800 G. The recorded hyperfine-Zeeman patterns were analyzed in detail using already known accurate hyperfine structure A- and B-constants. From the recordings the Landé gJ-factors for some levels belonging to the 5d2, 5d6s, 5d6p, 4f5d, 4f6s and 4f6p configurations of La II were determined. The obtained experimental gJ-factors are compared with earlier measurements and theoretical calculations.

Interplay of stereoelectronic and enviromental effects in tuning the structural and magnetic properties of a prototypical spin probe: further insights from a first principle dynamical approach.

PubMed

Pavone, Michele; Cimino, Paola; De Angelis, Filippo; Barone, Vincenzo

2006-04-05

The nitrogen isotropic hyperfine coupling constant (hcc) and the g tensor of a prototypical spin probe (di-tert-butyl nitroxide, DTBN) in aqueous solution have been investigated by means of an integrated computational approach including Car-Parrinello molecular dynamics and quantum mechanical calculations involving a discrete-continuum embedding. The quantitative agreement between computed and experimental parameters fully validates our integrated approach. Decoupling of the structural, dynamical, and environmental contributions acting onto the spectral observables allows an unbiased judgment of the role played by different effects in determining the overall experimental observables and highlights the importance of finite-temperature vibrational averaging. Together with their intrinsic interest, our results pave the route toward more reliable interpretations of EPR parameters of complex systems of biological and technological relevance.

The far-infrared laser magnetic resonance spectrum of the SiH radical and determination of ground state parameters

NASA Technical Reports Server (NTRS)

Brown, J. M.; Curl, R. F.; Evenson, K. M.

1984-01-01

The far-infrared laser magnetic resonance spectrum of the SiH radical in the v = O level of its X2Pi state has been recorded. The signals are rather weak. The molecules were generated in the reaction between fluorine atoms and SiH4. Rotational transitions have been detected in both 2Pi1/2 and 2Pi3/2 spin components but no fine structure transitions between the spin components were observed. Proton hyperfine splittings were resolved on some lines. The measurements have been analyzed, subjected to a least-squares fit using an effective Hamiltonian, and the appropriate molecular parameters determined. The weakness of the spectrum and the failure of attempts to power saturate favorable lines are both consistent with a small value for the electric dipole moment for SiH.

Resistively detected NMR line shapes in a quasi-one-dimensional electron system

NASA Astrophysics Data System (ADS)

Fauzi, M. H.; Singha, A.; Sahdan, M. F.; Takahashi, M.; Sato, K.; Nagase, K.; Muralidharan, B.; Hirayama, Y.

2017-06-01

We observe variation in the resistively detected nuclear magnetic resonance (RDNMR) line shapes in quantum Hall breakdown. The breakdown occurs locally in a gate-defined quantum point contact (QPC) region. Of particular interest is the observation of a dispersive line shape occurring when the bulk two-dimensional electron gas (2DEG) set to νb=2 and the QPC filling factor to the vicinity of νQPC=1 , strikingly resemble the dispersive line shape observed on a 2D quantum Hall state. This previously unobserved line shape in a QPC points to a simultaneous occurrence of two hyperfine-mediated spin flip-flop processes within the QPC. Those events give rise to two different sets of nuclei polarized in the opposite direction and positioned at a separate region with different degrees of electronic spin polarization.

The EPR study of Mn(2+) ion doped DADT single crystal produced under high pressure and temperature.

PubMed

Ceylan, Ümit; Tapramaz, Recep

2016-01-05

An EPR study on Cu(2+) and VO(2+) doped di ammonium d-tartrate single crystals has been reported in previous papers, but the same host did not accept Mn(2+) ion at the same reaction conditions in previous trials. In this study EPR study of Mn(2+) ion doped di ammonium d tartrate single crystal, (DADT) [(NH4)2C4H4O6], produced in a reactor under high pressure and high temperature. The electronic transitions were determined by the optical absorption spectrum. Hyperfine splitting and g values of the Mn(2+) ion forming a complex in the lattice were measured from experimental spectra and spin-spin dipolar splitting parameters D and E were found by the spectrum simulation techniques. Copyright © 2015 Elsevier B.V. All rights reserved.

Theoretical investigations of the local distortion and spectral properties for VO2+ in SiO2 Glass

NASA Astrophysics Data System (ADS)

Li, Mu-Neng; Zhang, Zhi-Hong; Wu, Shao-Yi

2017-11-01

The local distortions and the spin Hamiltonian parameters g factors g∥, g⊥ and the hyperfine structure constants A∥ and A⊥ for isolated vanadyl ions VO2+ doped in SiO2 glass at 700°C are theoretically investigated from the perturbation formulas of these parameters for a 3d1 ion in tetragonally compressed octahedra. In these formulas, the relationships between local structure of VO2+ ions center and the tetragonal crystal field parameters are established. As a result, the distortion of the ligand octahedron is attributed to the strong axial crystal-fields associated with the short V4+-O2- bond due to the strong V=O bonding in the silica matrix. The theoretical spin Hamiltonian parameters obtained in this work show reasonable agreement with the experimental data.

Cobalt spin states and hyperfine interactions in LaCoO3 investigated by LDA+U calculations

NASA Astrophysics Data System (ADS)

Leighton, C.; Hsu, H.; Blaha, P.; Wentzcovitch, R. M.

2010-12-01

The spin states of cobalt ions in the bulk and epitaxial-thin-film lanthanum cobaltite (LaCoO3) have been controversial for years. The controversial point is mainly the presence of intermediate-spin (IS) Co in the temperature range of 0-85 K. In this region, bulk LaCoO3 experiences a crossover from a diamagnetic to a paramagnetic phase, and the thin-film LaCoO3 is ferromagnetic and insulator. An approach to probe the Co spin state is thus of interest. With a series of LDA+U calculations, we have demonstrated that the electric field gradient (EFG) at the Co nucleus can be used as a fingerprint to identify the spin state of the Co ion in each case. Therefore, in principle, the spin state of the Co ion can be unambiguously determined from nuclear magnetic resonance (NMR) spectra. Our calculations also suggest that the presence of IS Co in this temperature range is unlikely, based not only on its relatively higher energy, but also on its associated conducting band structure incompatible with the measured insulating conductivity. This work was primarily supported by the MRSEC Program of NSF under Awards Number DMR-0212302 and DMR-0819885, and partially supported by NSF under ATM-0428774 (V-Lab), EAR-1019853, and EAR-0810272. The computations were performed mainly at the Minnesota Supercomputing Institute (MSI).

Permeability studies of redox-sensitive nitroxyl spin probes in corn oil using an L-band ESR spectrometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jebaraj, D. David; Utsumi, Hideo; Asath, R. Mohamed

Electron spin resonance (ESR) studies were carried out for 2mM {sup 14}N labeled {sup 2}H enriched 3-methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl (MC-PROXYL) and 3–carboxy-2,2,5,5,-tetramethyl-1-pyrrolidinyloxy (carboxy-PROXYL) in pure water and various concentrations of corn oil. The ESR parameters, such as the line width, hyperfine coupling constant, g-factor, rotational correlation time, partition parameter and permeability were reported for the samples. The line width broadening was observed for both nitroxyl radicals in corn oil solutions. The partition parameter for permeable MC-PROXYL in corn oil increases with increasing concentration of corn oil, which reveals that the nitroxyl spin probe permeates into the oil phase. From the results, themore » corn oil concentration was optimized as 50 % for phantom studies. The rotational correlation time also increases with increasing concentration of corn oil. The permeable and impermeable nature of nitroxyl spin probes was demonstrated. These results will be useful for the development of ESR/OMR imaging modalities in in vivo and in vitro studies.« less

(Charge separation in photoredox reactions). Informal annual technical progress report, October 1, 1981-October 1, 1982. [N,N,N',N'tetramethylbenzidine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kevan, L.

1982-10-21

During this period work has focused on the structural aspects of photoinduced charge separation in micellar media with initial forays into vesicular media. The primary techniques utilized are electron spin resonance and electron spin echo spectrometry. The analysis of electron spin echo modulation gives a unique handle on very weak hyperfine interactions thus providing a new structural tool for this general problem. Electron spin resonance and electron spin echo studies of the photoionization of N,N,N',N'tetramethylbenzidine (TMB) to give the cation radical have been carried out in anionic, cationic and nonionic micellar solutions frozen to 77/sup 0/K. The photoionization efficiency ofmore » TMB has also been studied in micelles with varying alkyl chain lengths of the surfactant. Stearic acid nitroxide spin probes have also been used to determine some structural aspects of the location of the neutral TMB molecule in anionic micelles before photoionization. The nitroxide work in which the nitroxide is acting as an electron acceptor also shows that a suitable electron acceptor can be located within the micellar structure. The effect of inorganic solutes on the efficiency of the photoionization of TMB in frozen micelles has also been studied. A series of electron scavenger studies have been initiated to study the effect on TMB photoionization efficiency. Electron spin echo detection of laser photogenerated TMB cation in liquid sodium dodecyl sulfate solutions at room temperature has recently been observed.« less

Search for variation of fundamental constants and violations of fundamental symmetries using isotope comparisons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berengut, J. C.; Flambaum, V. V.; Kava, E. M.

2011-10-15

Atomic microwave clocks based on hyperfine transitions, such as the caesium standard, tick with a frequency that is proportional to the magnetic moment of the nucleus. This magnetic moment varies strongly between isotopes of the same atom, while all atomic electron parameters remain the same. Therefore the comparison of two microwave clocks based on different isotopes of the same atom can be used to constrain variation of fundamental constants. In this paper, we calculate the neutron and proton contributions to the nuclear magnetic moments, as well as their sensitivity to any potential quark-mass variation, in a number of isotopes ofmore » experimental interest including {sup 201,199}Hg and {sup 87,85}Rb, where experiments are underway. We also include a brief treatment of the dependence of the hyperfine transitions to variation in nuclear radius, which in turn is proportional to any change in quark mass. Our calculations of expectation values of proton and neutron spin in nuclei are also needed to interpret measurements of violations of fundamental symmetries.« less

The Mössbauer Parameters of the Proximal Cluster of Membrane-Bound Hydrogenase Revisited: A Density Functional Theory Study.

PubMed

Tabrizi, Shadan Ghassemi; Pelmenschikov, Vladimir; Noodleman, Louis; Kaupp, Martin

2016-01-12

An unprecedented [4Fe-3S] cluster proximal to the regular [NiFe] active site has recently been found to be responsible for the ability of membrane-bound hydrogenases (MBHs) to oxidize dihydrogen in the presence of ambient levels of oxygen. Starting from proximal cluster models of a recent DFT study on the redox-dependent structural transformation of the [4Fe-3S] cluster, (57)Fe Mössbauer parameters (electric field gradients, isomer shifts, and nuclear hyperfine couplings) were calculated using DFT. Our results revise the previously reported correspondence of Mössbauer signals and iron centers in the [4Fe-3S](3+) reduced-state proximal cluster. Similar conflicting assignments are also resolved for the [4Fe-3S](5+) superoxidized state with particular regard to spin-coupling in the broken-symmetry DFT calculations. Calculated (57)Fe hyperfine coupling (HFC) tensors expose discrepancies in the experimental set of HFC tensors and substantiate the need for additional experimental work on the magnetic properties of the MBH proximal cluster in its reduced and superoxidized redox states.

Probing and Manipulating Ultracold Fermi Superfluids

NASA Astrophysics Data System (ADS)

Jiang, Lei

Ultracold Fermi gas is an exciting field benefiting from atomic physics, optical physics and condensed matter physics. It covers many aspects of quantum mechanics. Here I introduce some of my work during my graduate study. We proposed an optical spectroscopic method based on electromagnetically-induced transparency (EIT) as a generic probing tool that provides valuable insights into the nature of Fermi paring in ultracold Fermi gases of two hyperfine states. This technique has the capability of allowing spectroscopic response to be determined in a nearly non-destructive manner and the whole spectrum may be obtained by scanning the probe laser frequency faster than the lifetime of the sample without re-preparing the atomic sample repeatedly. Both quasiparticle picture and pseudogap picture are constructed to facilitate the physical explanation of the pairing signature in the EIT spectra. Motivated by the prospect of realizing a Fermi gas of 40K atoms with a synthetic non-Abelian gauge field, we investigated theoretically BEC-HCS crossover physics in the presence of a Rashba spin-orbit coupling in a system of two-component Fermi gas with and without a Zeeman field that breaks the population balance. A new bound state (Rashba pair) emerges because of the spin-orbit interaction. We studied the properties of Rashba pairs using a standard pair fluctuation theory. As the two-fold spin degeneracy is lifted by spin-orbit interaction, bound pairs with mixed singlet and triplet pairings (referred to as rashbons) emerge, leading to an anisotropic superfluid. We discussed in detail the experimental signatures for observing the condensation of Rashba pairs by calculating various physical observables which characterize the properties of the system and can be measured in experiment. The role of impurities as experimental probes in the detection of quantum material properties is well appreciated. Here we studied the effect of a single classical impurity in trapped ultracold Fermi superfluids. Although a non-magnetic impurity does not change macroscopic properties of s-wave Fermi superfluids, depending on its shape and strength, a magnetic impurity can induce single or multiple mid-gap bound states. The multiple mid-gap states could coincide with the development of a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase within the superfluid. As an analog of the Scanning Tunneling Microscope, we proposed a modified radio frequency spectroscopic method to measure the focal density of states which can be employed to detect these states and other quantum phases of cold atoms. A key result of our self consistent Bogoliubov-de Gennes calculations is that a magnetic impurity can controllably induce an FFLO state at currently accessible experimental parameters.

Low-frequency ESR studies on permeable and impermeable deuterated nitroxyl radicals in corn oil solution.

PubMed

David Jebaraj, D; Utsumi, Hideo; Milton Franklin Benial, A

2018-04-01

Low-frequency electron spin resonance studies were performed for 2 mM concentration of deuterated permeable and impermeable nitroxyl spin probes, 3-methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl and 3-carboxy-2,2,5,5,-tetramethyl-1-pyrrolidinyloxy in pure water and various concentrations of corn oil solution. The electron spin resonance parameters such as the line width, hyperfine coupling constant, g factor, rotational correlation time, permeability, and partition parameter were estimated. The broadening of line width was observed for nitroxyl radicals in corn oil mixture. The rotational correlation time increases with increasing concentration of corn oil, which indicates the less mobile nature of spin probe in corn oil mixture. The membrane permeability and partition parameter values were estimated as a function of corn oil concentration, which reveals that the nitroxyl radicals permeate equally into the aqueous phase and oil phase at the corn oil concentration of 50%. The electron spin resonance spectra demonstrate the permeable and impermeable nature of nitroxyl spin probes. From these results, the corn oil concentration was optimized as 50% for phantom studies. In this work, the corn oil and pure water mixture phantom models with various viscosities correspond to plasma membrane, and whole blood membrane with different hematocrit levels was studied for monitoring the biological characteristics and their interactions with permeable nitroxyl spin probe. These results will be useful for the development of electron spin resonance and Overhauser-enhanced magnetic resonance imaging modalities in biomedical applications. Copyright © 2017 John Wiley & Sons, Ltd.

Light hadron spectra in the constituent quark model with the Kobayashi-Kondo-Maskawa-'t Hooft effective U {sub A} (1) symmetry breaking interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dmitrasinovic, V.; Toki, H.; Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047

2006-02-15

We make a critical comparison of several versions of instanton-induced interactions present in the literature, all based on ITEP group's extension to three colours and flavours of 't Hooft's effective lagrangian, with the predictions of the phenomenological Kobayashi-Kondo-Maskawa (KKM) chiral quark lagrangian. We analyze the effects of all versions of the effective U {sub A} (1) symmetry breaking interactions on light hadron spectra in the non-relativistic constituent quark model. We show that the KKMT force, when used as a residual hyperfine interaction reproduces the correct ordering of pseudoscalar and vector mesons even without explicitly taking chiral symmetry into account. Moreover,more » the nucleon spectra are also correctly reproduced, only the Roper resonance remains too high, albeit lower than usual, at 1660 MeV. The latter's lower than expected mass is not due to a small excitation energy, as in the Glozman-Riska (GR) model, but to a combination of colour, flavour, and spatial wave function properties that enhance the relevant matrix elements. The KKMT interaction explicitly depends on flavour and spin of the quarks, but unlike the GR flavour-spin one it has a firm footing in QCD. In the process we provide several technical advances, in particular we show the first explicit derivation of the three-body Fierz transformation and apply it to the KKM interaction. We also discuss the ambiguities associated with the colour degree of freedom.« less

Heavy-ion-induced sucrose radicals investigated using EPR and UV spectroscopy.

PubMed

Nakagawa, Kouichi; Karakirova, Yordanka; Yordanov, Nicola D

2015-05-01

The potential use of a sucrose dosimeter for estimating both linear energy transfer (LET) and the absorbed dose of heavy ion and X-ray radiation was investigated. The stable free radicals were produced when sucrose was irradiated with heavy ions, such as helium, carbon, silicon and neon ions, and when the X-ray radiation was similar to the obtained electron paramagnetic resonance (EPR) spectra, which were ∼7 mT wide and composed of several hyperfine structures. In addition, the total spin concentration resulting from heavy-ion irradiation increased linearly as the absorbed dose increased, and decreased logarithmically as the LET increased. These empirical relations imply that the LET at a certain dose can be determined from the spin concentration. For sucrose and alanine, both cross-sections following C-ion irradiation with a 50 Gy dose were ∼1.3 × 10(-12) [μm(2)], taking into account the molecular size of the samples. The values of these cross-sections imply that multiple ionizing particles were involved in the production of stable radicals. Furthermore, UV absorbance at 267 nm of an aqueous solution of irradiated sucrose was found to linearly increase with increasing absorbed dose. Therefore, the EPR and UV results suggest that sucrose can be a useful dosimeter for heavy-ion irradiation. © The Author 2014. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

EPR, optical and modeling of Mn(2+) doped sarcosinium oxalate monohydrate.

PubMed

Kripal, Ram; Singh, Manju

2015-01-25

Electron paramagnetic resonance (EPR) study of Mn(2+) ions doped in sarcosinium oxalate monohydrate (SOM) single crystal is done at liquid nitrogen temperature (LNT). EPR spectrum shows a bunch of five fine structure lines and further they split into six hyperfine components. Only one interstitial site was observed. With the help of EPR spectra the spin Hamiltonian parameters including zero field splitting (ZFS) parameters are evaluated. The optical absorption study at room temperature is also done in the wavelength range 195-1100 nm. From this study cubic crystal field splitting parameter, Dq=730 cm(-1) and Racah inter-electronic repulsion parameters B=792 cm(-1), C=2278 cm(-1) are determined. ZFS parameters D and E are also calculated using crystal field parameters from superposition model and microscopic spin Hamiltonian theory. The calculated ZFS parameter values are in good match with the experimental values obtained by EPR. Copyright © 2014 Elsevier B.V. All rights reserved.

Macroscopic quantum coherence in ferritin

NASA Astrophysics Data System (ADS)

Garg, Anupam

1996-04-01

In a breakthrough experiment, Awschalom et al. [ Phys. Rev. Lett. 68, 3092 (1992)] have demonstrated that the antiferromagnetic core in ferritin resonates between two states with oppositely directed Néel vectors, making it the first observation of MQC. A theory has been developed for this resonance including the effect of the 100 or so57Fe nuclear spins expected in each ferritin core. Since the hyperfine coupling is known to be ˜68 MHz and the MQC frequency is ˜1 MHz, the degeneracy of the Néel states, and with it, the MQC resonance, is destroyed in all ferritin particles except those with zero total staggered nuclear spin. From the measured size of λ″(ω), the energy being absorbed by the ferritin is at least 4000 times larger than the maximum permissible. Hence, the true importance of these experiments lies not in the narrow issue of MQC, but in the disproof of long cherished theoretical conservation laws.

Evaluation of Spin Hamiltonian Parameters and Local Structure of Cu2+-doped Ion in xK2SO4-(50 - x)Na2SO4-50ZnSO4 Glasses with Various K2SO4 Concentrations

NASA Astrophysics Data System (ADS)

Ding, Ch.-Ch.; Wu, Sh.-Y.; Xu, Y.-Q.; Zhang, L.-J.; He, J.-J.

2018-03-01

The spin Hamiltonian parameters (SHPs), i.e., g factors and hyperfine structure constants, and local structures are theoretically studied by analyzing tetragonally elongated 3d9 clusters for Cu2+ in xK2SO4-(50 - x)Na2SO4-50ZnSO4 glasses with various K2SO4 concentrations x. The concentration dependences of the SHPs are attributed to the parabolic decreases of the cubic field parameter Dq, orbital reduction factor k, relative tetragonal elongation ratio τ, and core polarization constant κ with x. The [CuO6]10- clusters are found to undergo significant elongations of about 17% due to the Jahn-Teller effect. The calculated cubic field splittings and the SHPs at various concentrations agree well with the experimental data.

Investigating the large deformation of the 5 /2+ isomeric state in 73Zn: An indicator for triaxiality

NASA Astrophysics Data System (ADS)

Yang, X. F.; Tsunoda, Y.; Babcock, C.; Billowes, J.; Bissell, M. L.; Blaum, K.; Cheal, B.; Flanagan, K. T.; Garcia Ruiz, R. F.; Gins, W.; Gorges, C.; Grob, L. K.; Heylen, H.; Kaufmann, S.; Kowalska, M.; Krämer, J.; Malbrunot-Ettenauer, S.; Neugart, R.; Neyens, G.; Nörtershäuser, W.; Otsuka, T.; Papuga, J.; Sánchez, R.; Wraith, C.; Xie, L.; Yordanov, D. T.

2018-04-01

Recently reported nuclear spins and moments of neutron-rich Zn isotopes measured at ISOLDE-CERN [C. Wraith et al., Phys. Lett. B 771, 385 (2017), 10.1016/j.physletb.2017.05.085] show an uncommon behavior of the isomeric state in 73Zn. Additional details relating to the measurement and analysis of the Znm73 hyperfine structure are addressed here to further support its spin-parity assignment 5 /2+ and to estimate its half-life. A systematic investigation of this 5 /2+ isomer indicates that significant collectivity appears due to proton/neutron E 2 excitations across the proton Z = 28 and neutron N = 50 shell gaps. This is confirmed by the good agreement of the observed quadrupole moments with large scale Monte Carlo shell model calculations. In addition, potential energy surface calculations in combination with T plots reveal a triaxial shape for this isomeric state.

Demonstration of the Jaynes-Cummings ladder with Rydberg-dressed atoms

DOE PAGES

Lee, Jongmin; Martin, Michael J.; Jau, Yuan-Yu; ...

2017-04-06

Here, we observe the nonlinearity of the Jaynes-Cummings (JC) ladder in the Autler-Townes spectroscopy of the hyperfine ground states for a Rydberg-dressed two-atom system. The role of the two-level system in the JC model is played by the presence or absence of a collective Rydberg excitation, and the bosonic mode manifests as the number n of single-atom spin flips, symmetrically distributed between the atoms. We also measure the normal-mode splitting and √ n nonlinearity as a function of detuning and Rabi frequency, thereby experimentally establishing the isomorphism with the JC model.

Corrections to hyperfine splitting and Lamb shift induced by diagrams with second order radiative insertions in the electron line

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eides, M.I.; Karshenboim, S.G.; Shelyuto, V.A.

1994-12-31

Contributions to HFS and to the Lamb shift intervals of order a{sup 2}(Za){sup 5} induced by gauge invariant set of nineteen topologically different graphs with two radiative photons inserted in the electron line are considered. Corrections both to HFS and Lamb shift induced by nine diagrams are calculated in the Fried-Yennie gauge.

Theoretical proposal for a magnetic resonance study of charge transport in organic semiconductors

NASA Astrophysics Data System (ADS)

Mkhitaryan, Vagharsh

Charge transport in disordered organic semiconductors occurs via carrier incoherent hops in a band of localized states. In the framework of continuous-time random walk the carrier on-site waiting time distribution (WTD) is one of the basic characteristics of diffusion. Besides, WTD is fundamentally related to the density of states (DOS) of localized states, which is a key feature of a material determining the optoelectric properties. However, reliable first-principle calculations of DOS in organic materials are not yet available and experimental characterization of DOS and WTD is desirable. We theoretically study the spin dynamics of hopping carriers and propose measurement schemes directly probing WTD, based on the zero-field spin relaxation and the primary (Hahn) spin echo. The proposed schemes are possible because, as we demonstrate, the long-time behavior of the zero-field relaxation and the primary echo is determined by WTD, both for the hyperfine coupling dominated and the spin-orbit coupling dominated spin dynamics. We also examine the dispersive charge transport, which is a non-Markovian sub-diffusive process characterized by non-stationarity. We show that the proposed schemes unambiguously capture the effects of non-stationarity, e.g., the aging behavior of random walks. This work was supported by the Department of Energy-Basic Energy Sciences under Contract No. DE-AC02-07CH11358.

Tadpole renormalization and relativistic corrections in lattice NRQCD

NASA Astrophysics Data System (ADS)

Shakespeare, Norman H.; Trottier, Howard D.

1998-08-01

We make a detailed comparison of two tadpole renormalization schemes in the context of the quarkonium hyperfine splittings in lattice NRQCD. We renormalize improved gauge-field and NRQCD actions using the mean-link u0,L in the Landau gauge, and using the fourth root of the average plaquette u0,P. Simulations are done for the three quarkonium systems cc¯, bc¯, and bb¯. The hyperfine splittings are computed both at leading [O(MQv4)] and at next-to-leading [O(MQv6)] order in the relativistic expansion, where MQ is the renormalized quark mass, and v2 is the mean-squared velocity. Results are obtained at a large number of lattice spacings, in the range of about 0.14-0.38 fm. A number of features emerge, all of which favor tadpole renormalization using u0,L. This includes a much better scaling behavior of the hyperfine splittings in the three quarkonium systems when u0,L is used. We also find that relativistic corrections to the spin splittings are smaller when u0,L is used, particularly for the cc¯ and bc¯ systems. We also see signs of a breakdown in the NRQCD expansion when the bare quark mass falls below about 1 in lattice units. Simulations with u0,L also appear to be better behaved in this context: the bare quark masses turn out to be larger when u0,L is used, compared to when u0,P is used on lattices with comparable spacings. These results also demonstrate the need to go beyond tree-level tadpole improvement for precision simulations.

Nuclear magnetic resonance studies of high-spin ferric hemoproteins.

PubMed

Morishmima, I; Ogawa, S; Inubushi, T; Iizuka, T

1978-01-01

220 MHz proton Fourier transform (FT) NMR with quadrature phase detection (QPD) technique is applied to observe largely hyperfine-shifted signals of various hemoproteins and hemoenzymes in ferric high-spin state. The binding of F-, OCN-, SCN-, and CH3OH to the ferric heme iron in high-spin state in various hemoproteins has been studied by the use of FT/QPD technique at 220 MHz. The binding of formate ion to metmyoglobin (metMb) has also been studied. The spectrum of the formate complex was compared with that of hemoglobin M Milwaukee where carboxylate groups are bound to the hemes of the beta subunits. The acid-base transition of ferric myoglobin (Mb) was confirmed by monitoring the pH-dependent shift of the heme side methyl signals with the reflection point at pH 9.1. This finding is analyzed on the basis of rapid exchange between alkaline (low spin) and acidic (high spin) forms accompanied by the dissociation and association of one proton in the ferric Mb. The structure of the heme environment of ferric horseradish peroxidase (HRP) was studied. The pH-dependent features of NMR spectra of the ferric enzyme and its complexes with cyanide and azide were discussed in terms of heme environmental structures, comparing with the case of metMb. The results were interpreted as follows: There exists an ionizable amino group near the heme responsible for the ligand binding reactions of the enzyme, which modulates the entry of external azide to the heme iron through protolytic equilibrium of this group. The pK value of this group was determined to be 5.9 by monitoring the pH-dependent shift of the heme peripheral methyl signals of the native enzyme, indicating that the group is probably a histidyl residue. Acid-alkaline transition of metMb was confirmed to associate with the proton dissociation of an iron-bound water molecule, whereas in HRP, pH-dependent spin state change characterized by pK 11 is attributed not to the simple protolytic reaction of the iron-bound water but to the direct coordination of an amino acid residue of the polypeptide chain to the ferric heme iron. Histidyl imidazole is a possible candidate for the new sixth iron ligand in alkaline peroxidase above pH 11. Interaction of HRP with electron donor(indolepropionic acid, IPA) was also studied. The hyperfine-shifted proton signals of the heme peripheral groups of the enzyme showed a small but significant shift with stepwise additions of IPA, indicating that the donor binds at a specific site of HRP. There results are interpreted in terms of the interaction between the enzyme and the donor at the heme edge site.

Iron Atoms in Cr-Mn Antiferromagnetic Matrix

NASA Astrophysics Data System (ADS)

Szymański, K.; Satuła, D.; Dobrzyński, L.; Biernacka, M.; Perzyńska, K.; Zaleski, P.

2002-06-01

The results of the Mössbauer effect measurements on bcc Cr rich Cr-Fe-Mn alloys in temperature range 12-296 K in zero- and in applied magnetic fields are reported. Monochromatic, circularly polarized radiation was used for investigation of iron moments alignment. Strong enhancement of internal hyperfine magnetic field induced by the applied magnetic field was detected and explained as due to dynamical effects. At high temperatures alignment of iron moments in antiferromagnetic phase is weakly magnetic field-dependent. At low temperatures the average hyperfine magnetic field is antiparallel to the net magnetization showing that iron moments are partly ordered by the applied field.

Spin Polarization of Rb and Cs n p P2 3/2 (n =5 , 6) Atoms by Circularly Polarized Photoexcitation of a Transient Diatomic Molecule

NASA Astrophysics Data System (ADS)

Mironov, A. E.; Hewitt, J. D.; Eden, J. G.

2017-03-01

We report the selective population of Rb or Cs n p P2 3/2 (n =5 , 6; F =4 , 5) hyperfine states by the photodissociation of a transient, alkali-rare gas diatomic molecule. Circularly polarized (σ-), amplified spontaneous emission (ASE) on the D2 line of Rb or Cs (780.0 and 852.1 nm, respectively) is generated when Rb-Xe or Cs-Xe ground state collision pairs are photoexcited by a σ+-polarized optical field having a wavelength within the D2 blue satellite continuum, associated with the B Σ2 1/2 +←X Σ2 1/2 + (free←free ) transition of the diatomic molecule. The degree of spin polarization of Cs (6 p P3/2 2 ), specifically, is found to be dependent on the interatomic distance (R ) at which the excited complex is born, a result attributed to the structure of the B Σ2 1/2 + state. For Cs-Xe atomic pairs, tuning the wavelength of the optical field from 843 to 848 nm varies the degree of circular polarization of the ASE from 63% to almost unity because of the perturbation, in the 5 ≤R ≤6 Å interval, of the Σ2 1/2 + potential by a d σ molecular orbital associated with a higher Λ 2 electronic state. Monitoring only the Cs 6 p P3/2 2 spin polarization reveals a previously unobserved interaction of CsXe (B Σ2 1/2 + ) with the lowest vibrational levels of a Λ 2 state derived from Cs (5 d )+Xe . By inserting a molecular intermediate into the alkali atom excitation mechanism, these experiments realize electronic spin polarization through populating no more than two n p P2 3/2 hyperfine states, and demonstrate a sensitive spectroscopic probe of R -dependent state-state interactions and their impact on interatomic potentials.

Optical and Terahertz Measurements of Spintronic Materials

NASA Astrophysics Data System (ADS)

Bas, Derek A.

Terahertz time-domain spectroscopy (THz-TDS) is a versatile method to determine lattice, electronic charge and spin dynamics. This dissertation employs THz-TDS to study the spin and charge dynamics in topological insulator and antiferromagnetic systems. Observing time-domain effects on the scale of picoseconds gives unprecedented control over optoelectronic properties. Methods and challenges of THz generation, detection, and transmission are outlined. The wealth of light-matter interactions present in all nonlinear optical experiments are discussed, including primarily optical rectification, shift currents, and injection currents. Each of these gives valuable insight into the carrier dynamics of a material type. Conventional electronics can be improved in their speed and efficiency by taking advantage of an additional degree of freedom- electron spin. Therefore, we consider material types which exhibit great potential to replace common electronic materials while simultaneously employing electron spin for information storage or transport. Antiferromagnets show a type of spin-order that has the ability to store bits without unwanted interactions between neighboring particles. In antiferromagnetic MnF2 which has a Neel temperature of TN = 67 K, THz-TDS is performed on one-magnon and two-magnon resonances in the 0.1-2.3 THz range while varying the temperature from 6 to 295 K. The behavior of the one-magnon resonance is modeled by modified molecular field theory with an additional coupling term j set as a free parameter to fit the data. The resulting best fit value j = 1.1 provides the first experimental evidence indicating that neighboring spins in MnF 2 are only weakly coupled, closely approximating mean-field theory. Time-of-flight analysis was performed on the transmitted THz pulses to measure the temperature-dependent THz refractive index, which was modeled by phonon energy in the T > TN regime and magnetic energy in the T < TN regime. In the range T < 10 K, measured data deviates from this theory, and can be modeled by internal energy from hyperfine interactions, providing the first direct observation of hyperfine interactions in THz spectroscopy. Topological insulators exhibit the ability to transport spin-polarized currents along their surfaces with high mobilities. Phase-related pulses at photon energies 0.8 and 1.6 eV are used to simultaneously inject shift and injection currents into thin-films of the prototypical topological insulator Bi2Se3, and the foundation is laid out for an extensive study of the novel carrier properties in topological surface states. A method of symmetry analysis based on the crystal lattice is developed for isolation and individual study of the surfaceonly shift currents, which are threefold symmetric with equal components parallel and perpendicular to the pump polarization, and bulk/surface injection currents, which are isotropic parallel to the pump polarization and vanishing perpendicular to it. Pump energies can be tuned through the Dirac point, a capability which holds promise for the search of smoking gun evidence for the novel topological insulator surface state behavior that has been theorized.

Spin coherence and 14N ESEEM effects of nitrogen-vacancy centers in diamond with X-band pulsed ESR

NASA Astrophysics Data System (ADS)

Rose, B. C.; Weis, C. D.; Tyryshkin, A. M.; Schenkel, T.; Lyon, S. A.

2017-02-01

Pulsed ESR experiments are reported for ensembles of negatively-charged nitrogen-vacancy centers (NV$^-$) in diamonds at X-band magnetic fields (280-400 mT) and low temperatures (2-70 K). The NV$^-$ centers in synthetic type IIb diamonds (nitrogen impurity concentration $<1$~ppm) are prepared with bulk concentrations of $2\\cdot 10^{13}$ cm$^{-3}$ to $4\\cdot 10^{14}$ cm$^{-3}$ by high-energy electron irradiation and subsequent annealing. We find that a proper post-radiation anneal (1000$^\\circ$C for 60 mins) is critically important to repair the radiation damage and to recover long electron spin coherence times for NV$^-$s. After the annealing, spin coherence times of T$_2 = 0.74$~ms at 5~K are achieved, being only limited by $^{13}$C nuclear spectral diffusion in natural abundance diamonds. At X-band magnetic fields, strong electron spin echo envelope modulation (ESEEM) is observed originating from the central $^{14}$N nucleus. The ESEEM spectral analysis allows for accurate determination of the $^{14}$N nuclear hypefine and quadrupole tensors. In addition, the ESEEM effects from two proximal $^{13}$C sites (second-nearest neighbor and fourth-nearest neighbor) are resolved and the respective $^{13}$C hyperfine coupling constants are extracted.

Magneto-photocurrent in organic photovoltaic cells; the effect of short-lived charge transfer states

NASA Astrophysics Data System (ADS)

Ehrenfreund, Eitan; Devir-Wolfman, A.; Khachatryan, B.; Gautam, B.; Tessler, N.; Vardeny, Z. V.

2014-03-01

The spin degrees of freedom are responsible for the magnetic field effects in organic devices at low magnetic fields. The MFE is formed via a variety of spin-mixing mechanisms, such as the hyperfine (typical strength: Bhf<0.003 T), triplet-polaron or triplet-triplet (Btrip<0.1 T) interactions, that limit the response by their respective strength. We report on magneto-photocurrent (MPC) response of bulk hetero-junction organic photovoltaic cells in an extended field range B =0.00005 - 8 Tesla, and found that spin mixing mechanisms are still operative even at the highest fields. In fact, the response MPC(B) can be divided into three main regions, each with a different sign: sharp response that increases with B up to B1 ~ 0.04 T; broad response that decreases with B in the range from B1 to B2 ~ 0.3-0.7 T; and even broader response that increases above B2; this response does not saturate even at 8.5 T. We attribute the latter MPC component to short-lived charge transfer excitons (CTE) where spin-mixing is caused by the difference of the donor/acceptor g factors; a mechanism that is increasingly more effective at high magnetic field. Supported by the US-Israel BSF.

Identification of the altered pyrrole in the isomeric sulfmyoglobins: hyperfine shift patterns as indicators of ring saturation in ferric chlorins.

PubMed

Chatfield, M J; La Mar, G N; Smith, K M; Leung, H K; Pandey, R K

1988-03-08

Analysis of the 1H NMR hyperfine shift patterns of isomeric sulfmyoglobins is carried out in the met-aquo and met-cyano states to determine the site of saturation in each protein. The utility of the patterns for structure elucidation is established by specific deuterium labeling of the heme methyls of the terminal base product. On the basis of the known saturation of ring B in this isomer [Chatfield, M.J., La Mar, G.N., Lecomte, J.T.J., Balch, A.L., Smith, K.M., & Langry, K.C. (1986) J. Am. Chem. Soc. 108, 7108-7110], the methyl resonance of the saturated ring is found to have strongly attenuated contact shift. Thus, the heme methyl contact shift pattern is diagnostic for the saturated pyrrole in the high-spin state. This rationale is then applied to analyze the assigned NMR spectra of the initial and terminal acid sulfmyoglobin products, revealing that the same ring B is saturated in each isomer. In contrast, the heme methyl contact shift pattern in low-spin ferric complexes reveals that the methyls both on the affected pyrrole and on the trans pyrrole are influenced similarly on sulfmyoglobin formation, precluding the use of this methyl shift pattern as a unique indicator of the site of saturation. Identification of exchangeable proximal histidine resonances for met-aquo sulfmyoglobin complexes with shifts similar to that in native myoglobin dictates inconsequential axial alterations in the sulfmyoglobins, while location of downfield meso proton resonances analogous to those of the native protein demonstrates the retention of the coordinate water in the active site of met-sulfmyoglobin.

Effect of WO3 on EPR, structure and electrical conductivity of vanadyl doped WO3·M2O·B2O3 (M=Li, Na) glasses

NASA Astrophysics Data System (ADS)

Sheoran, A.; Agarwal, A.; Sanghi, S.; Seth, V. P.; Gupta, S. K.; Arora, M.

2011-12-01

Glasses with composition xWO3·(30-x)M2O·70B2O3 (M=Li, Na; 0≤x≤15) doped with 2 mol% V2O5 have been prepared using the melt-quench technique. The electron paramagnetic resonance spectra have been recorded in X-band (ν≈9.14 GHz) at room temperature (RT). The spin Hamiltonian parameters, dipolar hyperfine coupling parameter and Fermi contact interaction parameter have been calculated. It is observed that the resultant resonance spectra contain hyperfine structures (hfs) only due to V4+ ions, which exist as VO2+ ions in octahedral coordination with a tetragonal compression in the present glass system. The tetragonality increases with WO3:M2O ratio and also there is an expansion of 3dxy orbit of unpaired electron in the vanadium ion. The study of IR transmission spectra over a range 400-4000 cm-1 depicts the presence of WO6 group. The DC conductivity (σ) has been measured in the temperature range 423-623 K and is found to be predominantly ionic.

DFT and ENDOR Study of Bixin Radical Cations and Neutral Radicals on Silica-Alumina.

PubMed

Tay-Agbozo, Sefadzi S; Krzyaniak, Matthew D; Bowman, Michael K; Street, Shane; Kispert, Lowell D

2015-06-18

Bixin, a carotenoid found in annatto (Bixa orellana), is unique among natural carotenoids by being water-soluble. We stabilized free radicals from bixin on the surface of silica-alumina (Si-Al) and characterized them by pulsed electron-nuclear double resonance (ENDOR). DFT calculations of unpaired electron spin distribution for various bixin radicals predict the EPR hyperfine couplings. Least-square fitting of experimental ENDOR spectra by spectra calculated from DFT hyperfine couplings characterized the radicals trapped on Si-Al. DFT predicts that the trans bixin radical cation is more stable than the cis bixin radical cation by 1.26 kcal/mol. This small energy difference is consistent with the 26% trans and 23% cis radical cations in the ENDOR spectrum. The remainder of the ENDOR spectrum is due to several neutral radicals formed by loss of a H(+) ion from the 9, 9', 13, or 13' methyl group, a common occurrence in all water-insoluble carotenoids previously studied. Although carboxyl groups of bixin strongly affect its solubility relative to other natural carotenoids, they do not alter properties of its free radicals based on DFT calculations and EPR measurements which remain similar to typical water-insoluble carotenoids.

Magnetism of the 35 K superconductor CsEuFe4As4

NASA Astrophysics Data System (ADS)

Albedah, Mohammed A.; Nejadsattari, Farshad; Stadnik, Zbigniew M.; Liu, Yi; Cao, Guang-Han

2018-04-01

The results of ab initio hyperfine-interaction parameters calculations, and of x-ray diffraction and 57Fe and 151Eu Mössbauer spectroscopy study of the new 35 K superconductor CsEuFe4As4 are reported. The superconductor crystallizes in the tetragonal space group P4/mmm with the lattice parameters a = 3.8956(1) Å and c = 13.6628(5) Å. It is demonstrated unequivocally that there is no magnetic order of the Fe magnetic moments down to 2.1 K and that the ferromagnetic order is associated with the Eu magnetic moments. The Curie temperature TC = 15.97(8) K determined from the temperature dependence of the hyperfine magnetic field at 151Eu nuclei is shown to be compatible with the temperature dependence of the transferred hyperfine magnetic field at 57Fe nuclei that is induced by the ferromagnetically ordered Eu sublattice. The Eu magnetic moments are shown to be perpendicular to the crystallographic c-axis. The temperature dependence of the principal component of the electric field gradient tensor, both at Fe and Eu sites, is well described by a T 3/2 power-law relation. Good agreement between the calculated and measured hyperfine-interaction parameters is observed. The Debye temperature of CsEuFe4As4 is found to be 295(3) K.

Mössbauer spectroscopy measurements on the 35.5 K superconductor Rb1 -δEuFe4As4

NASA Astrophysics Data System (ADS)

Albedah, Mohammed A.; Nejadsattari, Farshad; Stadnik, Zbigniew M.; Liu, Yi; Cao, Guang-Han

2018-04-01

The results of x-ray diffraction and 57Fe and 151Eu Mössbauer spectroscopy measurements, supplemented with ab initio hyperfine-interaction parameter calculations, on the new 35.5 K superconductor Rb1 -δEuFe4As4 are presented. The superconductor crystallizes in the tetragonal space group P 4 /m m m with the lattice parameters a =3.8849 (1 ) Å and c =13.3370 (3 ) Å. It is shown that there is no magnetic order of the Fe magnetic moments down to 2.1 K and that the ferromagnetic order is associated solely with the Eu magnetic moments. The Curie temperature TC=16.54 (8 ) K is determined from the temperature dependence of both the hyperfine magnetic field at 151Eu nuclei and the transferred hyperfine magnetic field at 57Fe nuclei that is induced by the ferromagnetically ordered Eu sublattice. The Eu magnetic moments are demonstrated to be perpendicular to the crystallographic c axis. The temperature dependence of the principal component of the electric field gradient tensor, at both Fe and Eu sites, is well described by a T3 /2 power-law relation. Good agreement between the calculated and measured hyperfine-interaction parameters is observed. The Debye temperature of Rb1 -δEuFe4As4 is found to be 391(8) K.

Double quantum coherence ESR spectroscopy and quantum chemical calculations on a BDPA biradical.

PubMed

Haeri, Haleh Hashemi; Spindler, Philipp; Plackmeyer, Jörn; Prisner, Thomas

2016-10-26

Carbon-centered radicals are interesting alternatives to otherwise commonly used nitroxide spin labels for dipolar spectroscopy techniques because of their narrow ESR linewidth. Herein, we present a novel BDPA biradical, where two BDPA (α,α,γ,γ-bisdiphenylene-β-phenylallyl) radicals are covalently tethered by a saturated biphenyl acetylene linker. The inter-spin distance between the two spin carrier fragments was measured using double quantum coherence (DQC) ESR methodology. The DQC experiment revealed a mean distance of only 1.8 nm between the two unpaired electron spins. This distance is shorter than the predictions based on a simple modelling of the biradical geometry with the electron spins located at the central carbon atoms. Therefore, DFT (density functional theory) calculations were performed to obtain a picture of the spin delocalization, which may give rise to a modified dipolar interaction tensor, and to find those conformations that correspond best to the experimentally observed inter-spin distance. Quantum chemical calculations showed that the attachment of the biphenyl acetylene linker at the second position of the fluorenyl ring of BDPA did not affect the spin population or geometry of the BDPA radical. Therefore, spin delocalization and geometry optimization of each BDPA moiety could be performed on the monomeric unit alone. The allylic dihedral angle θ 1 between the fluorenyl rings in the monomer subunit was determined to be 30° or 150° using quantum chemical calculations. The proton hyperfine coupling constant calculated from both energy minima was in very good agreement with literature values. Based on the optimal monomer geometries and spin density distributions, the dipolar coupling interaction between both BDPA units could be calculated for several dimer geometries. It was shown that the rotation of the BDPA units around the linker axis (θ 2 ) does not significantly influence the dipolar coupling strength when compared to the allylic dihedral angle θ 1 . A good agreement between the experimental and calculated dipolar coupling was found for θ 1 = 30°.

Hydrogen bonding and spin density distribution in the QB semiquinone of bacterial reaction centers and comparison with the QA site

PubMed Central

Martin, Erik; Samoilova, Rimma I.; Narasimhulu, Kupala V.; Lin, Tzu-Jen; O’Malley, Patrick J.; Wraight, Colin A.; Dikanov, Sergei A.

2011-01-01

In the photosynthetic reaction center from Rhodobacter sphaeroides, the primary (QA) and secondary (QB) electron acceptors are both ubiquinone-10, but with very different properties and functions. To investigate the protein environment that imparts these functional differences, we have applied X-band HYSCORE, a 2D pulsed EPR technique, to characterize the exchangeable protons around the semiquinone (SQ) in the QA and QB sites, using samples of 15N-labeled reaction centers, with the native high spin Fe2+ exchanged for diamagnetic Zn2+, prepared in 1H2O and 2H2O solvent. The powder HYSCORE method is first validated against the orientation-selected Q-band ENDOR study of the QA SQ by Flores et al. (Biophys. J. 2007, 92, 671–682), with good agreement for two exchangeable protons with anisotropic hyperfine tensor components, T, both in the range 4.6–5.4 MHz. HYSCORE was then applied to the QB SQ where we found proton lines corresponding to T~5.2, 3.7 MHz and T~1.9 MHz. Density functional-based quantum mechanics/molecular mechanics (QM/MM) calculations, employing a model of the QB site, were used to assign the observed couplings to specific hydrogen bonding interactions with the QB SQ. These calculations allow us to assign the T=5.2 MHz proton to the His-L190 NδH…O4 (carbonyl) hydrogen bonding interaction. The T =3.7 MHz spectral feature most likely results from hydrogen bonding interactions of O1 (carbonyl) with both Gly-L225 peptide NH and Ser-L223 hydroxyl OH, which possess calculated couplings very close to this value. The smaller 1.9 MHz coupling is assigned to a weakly bound peptide NH proton of Ile-L224. The calculations performed with this structural model of the QB site show less asymmetric distribution of unpaired spin density over the SQ than seen for the QA site, consistent with available experimental data for 13C and 17O carbonyl hyperfine couplings. The implications of these interactions for QB function and comparisons with the QA site are discussed. PMID:21417328

Radiative transfer of HCN: interpreting observations of hyperfine anomalies

NASA Astrophysics Data System (ADS)

Mullins, A. M.; Loughnane, R. M.; Redman, M. P.; Wiles, B.; Guegan, N.; Barrett, J.; Keto, E. R.

2016-07-01

Molecules with hyperfine splitting of their rotational line spectra are useful probes of optical depth, via the relative line strengths of their hyperfine components. The hyperfine splitting is particularly advantageous in interpreting the physical conditions of the emitting gas because with a second rotational transition, both gas density and temperature can be derived. For HCN however, the relative strengths of the hyperfine lines are anomalous. They appear in ratios which can vary significantly from source to source, and are inconsistent with local thermodynamic equilibrium (LTE). This is the HCN hyperfine anomaly, and it prevents the use of simple LTE models of HCN emission to derive reliable optical depths. In this paper, we demonstrate how to model HCN hyperfine line emission, and derive accurate line ratios, spectral line shapes and optical depths. We show that by carrying out radiative transfer calculations over each hyperfine level individually, as opposed to summing them over each rotational level, the anomalous hyperfine emission emerges naturally. To do this requires not only accurate radiative rates between hyperfine states, but also accurate collisional rates. We investigate the effects of different sets of hyperfine collisional rates, derived via the proportional method and through direct recoupling calculations. Through an extensive parameter sweep over typical low-mass star-forming conditions, we show the HCN line ratios to be highly variable to optical depth. We also reproduce an observed effect whereby the red-blue asymmetry of the hyperfine lines (an infall signature) switches sense within a single rotational transition.

Spin-dependent polarizabilities of hydrogenic atoms in magnetic fields of arbitrary strength

NASA Astrophysics Data System (ADS)

Castner, T. G.; Dexter, D. L.; Druger, S. D.

1981-12-01

Utilizing the magnetic field-dependent spin-orbit interaction, the relativistic correction to the Zeeman energy, and the usual diamagnetic interaction, we have calculated spin-dependent electrical polarizabilities of hydrogenic atoms using the Hassé variational approach. The polarizabilities α(↑) and α(↓) for the two spin directions have been obtained for the electric field both parallel and perpendicular to the magnetic field Hz in the weak-field (γ<<1), intermediate-field (γ~1), and strong-field (γ>>1) limits, where γ=(ɛ2ℏ3Hzm*2e3c), with ɛ a static dielectric constant and m* an isotropic effective mass. The results for hydrogen atoms (ɛ=1 and m*=m) in the weak-field limit yield [α(↓)-α(↑)]α(0)~2.31α2fsγ (αfs=1137) with a negligible anisotropy. In the strong-field limit [α⊥(↓)-α⊥(↑)] falls precipitously while [α∥(↓)-α∥(↑)] continues to increase up to at least γ=104, but more slowly than linearly with γ. The spin-independent quantities [α∥(↓)+α∥(↑)] and [α⊥(↓)+α⊥(↑)] are discussed in the intermediate- and high-field limits and represent an extension of the earlier low-field results obtained by Dexter. The implications of these results for shallow-donor impurity atoms in semiconductors and for hydrogen-atom atmospheres of magnetic white dwarfs and neutron stars are briefly considered. The effects of the dramatic shrinkage of the electron's wave function on the spin Zeeman energy and the electron-proton hyperfine interaction are also discussed.

Approaches to Measuring Entanglement in Chemical Magnetometers

PubMed Central

2013-01-01

Chemical magnetometers are radical pair systems such as solutions of pyrene and N,N-dimethylaniline (Py–DMA) that show magnetic field effects in their spin dynamics and their fluorescence. We investigate the existence and decay of quantum entanglement in free geminate Py–DMA radical pairs and discuss how entanglement can be assessed in these systems. We provide an entanglement witness and propose possible observables for experimentally estimating entanglement in radical pair systems with isotropic hyperfine couplings. As an application, we analyze how the field dependence of the entanglement lifetime in Py–DMA could in principle be used for magnetometry and illustrate the propagation of measurement errors in this approach. PMID:24372396

Conventional electron paramagnetic resonance of Mn2+ in synthetic hydroxyapatite at different concentrations of the doped manganese

NASA Astrophysics Data System (ADS)

Murzakhanov, F.; Mamin, G.; Voloshin, A.; Klimashina, E.; Putlyaev, V.; Doronin, V.; Bakhteev, S.; Yusupov, R.; Gafurov, M.; Orlinskii, S.

2018-05-01

Powders of synthetic hydroxyapatite doped with Mn2+ ions in concentrations from 0.05 till 5 wt. % were investigated by conventional electron paramagnetic resonance (EPR). The parameters of the spin-Hamiltonian are derived. Partially resolved hyperfine structure in the magnetic fields corresponding to g ≈ 4.3 and g ≈ 9.4 is observed. The narrowing of the central peak with concentration is reported. A possibility to use the linewidth and intensity of the central peak for concentration measurements are discussed. The results could be used for the identification and qualification of Mn2+ in oil, mining and ore formations.

High-resolution molecular-beam spectroscopy of NaCN and Na 13CN

NASA Astrophysics Data System (ADS)

van Vaals, J. J.; Meerts, W. Leo; Dymanus, A.

The sodium cyanide molecule was studied by molecular-beam electric-resonance spectroscopy in the microwave region. We used the seeded-beam technique to produce a supersonic beam with strong translational, rotational and vibrational cooling. In the frequency range 9.5-40 GHz we observed and identified for NaCN 186 and for Na 13CN 107 hyperfine transitions in 20 and 16 rotational transitions, respectively, all in the ground vibrational state. The rotational, the five quartic and three sextic centrifugal distortion constants of NaCN are: A″ = 57921.954(7) MHz; B″ = 8369.312(2) MHz, C″ = 7272.712(2) MHz. All quadrupole and several spin-rotation coupling constants for the hyperfine interaction were evaluated. The quadrupole coupling constants (in MHz) for NaCN are: eQq12(Na) = -5.344(5), eQq12 = 2.397(7). eQq12(N) = 2.148(4), eQq12(N) = -4.142(5). From these constants and those of Na 13CN we have determined the principal components of the quadrupole coupling tensor for potassium and nitrogen. The structure of sodium cyanide evaluated from the rotational constants of NaCN and Na 13CN was found to be T shaped, similar to the structure of KCN but completely different from the linear isocyanide configuration of LiNC. The effective structural parameters for sodium cyanide in the ground vibrational state are: rCN = 1.170(4) Å, rNaC = 2.379(15) Å, rN12N = 2.233(15) Å, in gratifying agreement with ab initio calculations. Both the geometrical structure and the hyperfine coupling justify the conclusion that the CN group in gaseous sodium cyanide approximately can be considered as a free CN - ion.

Spectroscopic Measurement of LEAD-204 Isotope Shift and LEAD-205 Nuclear Spin.

NASA Astrophysics Data System (ADS)

Schonberger, Peter

The isotope shift of ('204)Pb and the nuclear spin of 1.4 x 10('7)-y ('205)Pb was determined from a high -resolution optical measurement of the 6p('2) ('3)P(,o) -6p7s('3)P(,1)('o) 283.3-nm resonance line. The value of the shift, relative to ('208)Pb is -140.2(8) x 10('-3)cm(' -1), the negative sign indicating a shift to lower wave numbers. The precision is 3-4 times greater than that of previous measurements. The spin of ('205)Pb l = 5/2 was obtained from the measurement of the relative intensities of its three hyperfine components. This method of absorption spectroscopy determination of ground state nuclear spin is applicable to any stable or longlived isotope. High resolution optical absorption spectra were obtained with a 25.4cm diffraction grating in a 9.1m focal length Czerny-Turner spectrometer. A signal-averaging scanning technique was used to record the spectra. Increased precision in the isotope shift measurement was attained by using separated isotope samples of ('204)Pb and ('207)Pb. A controlled amount of the later was incorporated in the absorption cell to provide internal calibration by its 6p7s ('3)P(,1)('o) hfs separation. Absorption spectra were recorded for several optical thicknesses of the absorber. A single spin value of increased precision was derived from the entire set of combined data.

Ab Initio Theory of Nuclear Magnetic Resonance Shifts in Metals

NASA Astrophysics Data System (ADS)

D'Avezac, Mayeul; Marzari, Nicola; Mauri, Francesco

2005-03-01

A comprehensive approach for the first-principles determination of all-electron NMR shifts in metallic systems is presented. Our formulation is based on a combination of density-functional perturbation theory and all-electron wavefunction reconstruction, starting from periodic-boundary calculations in the pseudopotential approximation. The orbital contribution to the NMR shift (the chemical shift) is obtained by combining the gauge-including projector augmented-wave approach (GIPAW), originally developed for the case of insulatorsootnotetextC. J. Pickard, Francesco Mauri, Phys. Rev. B, 63, 245101(2001), with the extension of linear-response theory to the case of metallic systemsootnotetextS. de Gironcoli, Phys. Rev. B, 51, 6773(1995). The spin contribution (the Knight shift) is obtained as a response to a finite uniform magnetic field, and through reconstructing the hyperfine interaction between the electron-spin density and the nuclear spins with the projector augmented-wave method (PAWootnotetextC. G. Van de Walle, P. E. Blöchl, Phys. Rev. B, 47, 4244(1993)). Our method is validated with applications to the case of the homogeneous electron gas and of simple metals. (Work supported by MURI grant DAAD 19-03-1-0169 and MIT-France)

Experimental demonstration of radicaloid character in a RuV=O intermediate in catalytic water oxidation

PubMed Central

Moonshiram, Dooshaye; Alperovich, Igor; Concepcion, Javier J.; Meyer, Thomas J.; Pushkar, Yulia

2013-01-01

Water oxidation is the key half reaction in artificial photosynthesis. An absence of detailed mechanistic insight impedes design of new catalysts that are more reactive and more robust. A proposed paradigm leading to enhanced reactivity is the existence of oxyl radical intermediates capable of rapid water activation, but there is a dearth of experimental validation. Here, we show the radicaloid nature of an intermediate reactive toward formation of the O-O bond by assessing the spin density on the oxyl group by Electron Paramagnetic Resonance (EPR). In the study, an 17O-labeled form of a highly oxidized, short-lived intermediate in the catalytic cycle of the water oxidation catalyst cis,cis-[(2,2-bipyridine)2(H2O)RuIIIORuIII(OH2)(bpy)2]4+ was investigated. It contains Ru centers in oxidation states [4,5], has at least one RuV = O unit, and shows |Axx| = 60G 17O hyperfine splittings (hfs) consistent with the high spin density of a radicaloid. Destabilization of π-bonding in the d3 RuV = O fragment is responsible for the high spin density on the oxygen and its high reactivity. PMID:23417296

Development of a polarized 31Mg+ beam as a spin-1/2 probe for BNMR

NASA Astrophysics Data System (ADS)

Levy, C. D. P.; Pearson, M. R.; Dehn, M. H.; Karner, V. L.; Kiefl, R. F.; Lassen, J.; Li, R.; MacFarlane, W. A.; McFadden, R. M. L.; Morris, G. D.; Stachura, M.; Teigelhöfer, A.; Voss, A.

2016-12-01

A 28 keV beam of 31Mg+ ions was extracted from a uranium carbide, proton-beam-irradiated target coupled to a laser ion source. The ion beam was nuclear-spin polarized by collinear optical pumping on the 2it {S}_{1/2}-2it {P}_{1/2} transition at 280 nm. The polarization was preserved by an extended 1 mT guide field as the beam was transported via electrostatic bends into a 2.5 T longitudinal magnetic field. There the beam was implanted into a single crystal MgO target and the beta decay asymmetry was measured. Both hyperfine ground states were optically pumped with a single frequency light source, using segmentation of the beam energy, which boosted the polarization by approximately 50 % compared to pumping a single ground state. The total decay asymmetry of 0.06 and beam intensity were sufficient to provide a useful spin-1/2 beam for future BNMR experiments. A variant of the method was used previously to optically pump the full Doppler-broadened absorption profile of a beam of 11Be+ with a single-frequency light source.

Investigation of irradiated 1H-Benzo[b]pyrrole by ESR, thermal methods and learning algorithm

NASA Astrophysics Data System (ADS)

Algul, Gulay; Ceylan, Yusuf; Usta, Keziban; Yumurtaci Aydogmus, Hacer; Usta, Ayhan; Asik, Biray

2016-05-01

1H-Benzo[b]pyrrole samples were irradiated in the air with gamma source at 0.969 kGy per hour at room temperature for 24, 48 and 72 h. After irradiation, electron spin resonance, thermogravimetry analysis (TGA) and differential thermal analysis (DTA) measurements were immediately carried out on the irradiated and unirradiated samples. The ESR measurements were performed between 320 and 400 K. ESR spectra were recorded from the samples irradiated for 48 and 72 h. The obtained spectra were observed to be dependent on temperature. Two radical-type centres were detected on the sample. Detected radiation-induced radicals were attributed to R-+•NH and R=•CC2H2. The g-values and hyperfine constants were calculated by means of the experimental spectra. It was also determined from TGA spectrum that both the unirradiated and irradiated samples were decomposed at one step with the rising temperature. Moreover, a theoretical study was presented. Success of the machine learning methods was tested. It was found that bagging techniques, which are widely used in the machine learning literature, could optimise prediction accuracy noticeably.

Complete Monitoring of Coherent and Incoherent Spin Flip Domains in the Recombination of Charge-Separated States of Donor-Iridium Complex-Acceptor Triads.

PubMed

Klein, Johannes H; Schmidt, David; Steiner, Ulrich E; Lambert, Christoph

2015-09-02

The spin chemistry of photoinduced charge-separated (CS) states of three triads comprising one or two triarylamine donors, a cyclometalated iridium complex sensitizer and a naphthalene diimide (NDI) acceptor, was investigated by transient absorption spectroscopy in the ns-μs time regime. Strong magnetic-field effects (MFE) were observed for two triads with a phenylene bridge between iridium complex sensitizer and NDI acceptor. For these triads, the lifetimes of the CS states increased from 0.6 μs at zero field to 40 μs at about 2 T. Substituting the phenylene by a biphenyl bridge causes the lifetime of the CS state at zero field to increase by more than 2 orders of magnitude (τ = 79 μs) and the MFE to disappear almost completely. The kinetic MFE was analyzed in the framework of a generalized Hayashi-Nagakura scheme describing coherent (S, T0 ↔ T±) as well as incoherent (S, T0 ⇌ T±) processes by a single rate constant k±. The magnetic-field dependence of k± of the triads with phenylene bridge spans 2 orders of magnitude and exhibits a biphasic behavior characterized by a superposition of two Lorentzians. This biphasic MFE is observed for the first time and is clearly attributable to the coherent (B < 10 mT) and incoherent (10 mT < B < 2 T) domains of spin motion induced by isotropic and anisotropic hyperfine coupling. The parameters of both domains are well understood in terms of the structural properties of the two triads, including the effect of electron hopping in the triad with two donor moieties. The kinetic model also accounts for the reduction of the MFE on reducing the rate constant of charge recombination in the triad with the biphenyl bridge.

Esr Spectra of Alkali-Metal Atoms on Helium Nanodroplets: a Theoretical Model for the Prediction of Helium Induced Hyperfine Structure Shifts

NASA Astrophysics Data System (ADS)

Hauser, Reas W.; Filatov, Michael; Ernst, Wolfgang E.

2013-06-01

We predict He-droplet-induced changes of the isotropic HFS constant a_{HFS} of the alkali-metal atoms M = Li, Na, K and Rb on the basis of a model description. Optically detected electron spin resonance spectroscopy has allowed high resolution measurements that show the influence of the helium droplet and its size on the unpaired electron spin density at the alkali nucleus. Our theoretical approach to describe this dependence is based on a combination of two well established techniques: Results of relativistic coupled-cluster calculations on the alkali-He dimers (energy and HFS constant as functions of the binding length) are mapped onto the doped-droplet-situation with the help of helium-density functional theory. We simulate doped droplets He_{N} with N ranging from 50 to 10000, using the diatomic alkali-He-potential energy curves as input. From the obtained density profiles we evaluate average distances between the dopant atom and its direct helium neighborhood. The distances are then set in relation to the variation of the HFS constant with binding length in the simplified alkali-He-dimer model picture. This method yields reliable relative shifts but involves a systematic absolute error. Hence, the absolute values of the shifts are tied to one experimentally determined HFS constant for ^{85}Rb-He_{N = 2000}. With this parameter choice we obtain results in good agreement with the available experimental data for Rb and K^{a,b} confirming the predicted 1/N trend of the functional dependence^{c}. M. Koch, G. Auböck, C. Callegari, and W. E. Ernst, Phys. Rev. Lett. 103, 035302-1-4 (2009) M. Koch, C. Callegari, and W. E. Ernst, Mol. Phys. 108 (7), 1005-1011 (2010) A. W. Hauser, T. Gruber, M. Filatov, and W. E. Ernst, ChemPhysChem (2013) online DOI: 10.1002/cphc.201200697

Spin-Orbit-Coupled Interferometry with Ring-Trapped Bose-Einstein Condensates

NASA Astrophysics Data System (ADS)

Helm, J. L.; Billam, T. P.; Rakonjac, A.; Cornish, S. L.; Gardiner, S. A.

2018-02-01

We propose a method of atom interferometry using a spinor Bose-Einstein condensate with a time-varying magnetic field acting as a coherent beam splitter. Our protocol creates long-lived superpositional counterflow states, which are of fundamental interest and can be made sensitive to both the Sagnac effect and magnetic fields on the sub-μ G scale. We split a ring-trapped condensate, initially in the mf=0 hyperfine state, into superpositions of internal mf=±1 states and condensate superflow, which are spin-orbit coupled. After interrogation, the relative phase accumulation can be inferred from a population transfer to the mf=±1 states. The counterflow generation protocol is adiabatically deterministic and does not rely on coupling to additional optical fields or mechanical stirring techniques. Our protocol can maximize the classical Fisher information for any rotation, magnetic field, or interrogation time and so has the maximum sensitivity available to uncorrelated particles. Precision can increase with the interrogation time and so is limited only by the lifetime of the condensate.

Laboratory detection of the C3N an C4H free radicals

NASA Technical Reports Server (NTRS)

Gottlieb, C. A.; Gottlieb, E. W.; Thaddeus, P.; Kawamura, H.

1983-01-01

The millimeter-wave spectra of the linear carbon chain free radicals C3N and C4H, first identified in IRC + 10216 and hitherto observed only in a few astronomical sources, have been detected with a Zeeman-modulated spectrometer in laboratory glow discharges through low pressure flowing mixtures of N2 + HC3N and He + HCCH, respectively. Four successive rotational transitions between 168 and 198 GHz have been measured for C3N, and five rotational transitions between 143 and 200 GHz for C4H; each is a well-resolved spin doublet owing to the unpaired electron present in both species. Precise values for the rotational, centrifugal distortion, and spin doubling constants have been obtained, which, with hyperfine constants derived from observations of the lower rotational transitions in the astronomical source TMC 1, allow all the rotational transitions of C3N and C4H at frequencies less than 300 GHz to be calculated to an absolute accuracy exceeding 1 ppm.

An electron spin resonance study of gamma-ray irradiated ginseng.

PubMed

Nakamura, Hideo; Ukai, Mitsuko; Shimoyama, Yuhei

2006-03-13

Using electron spin resonance (ESR) spectroscopy, we revealed the presence of four radical species in gamma-ray irradiated ginseng (Agaliaceae). Before irradiation, the representative ESR spectrum of ginseng is composed of a sextet centered at g = 2.0, a sharp singlet at the same g-value, and a singlet at about g = 4.0. The first one is attributable to a hyperfine (hf) signal of Mn2+ ion (hf constant: 7.4 mT). The second one is due to an organic free radical. The third one is originated from Fe3+. Upon gamma-ray irradiation, a new ESR (the fourth) signal was detectable in the vicinity of g = 2.0 region. The progressive saturation behaviors of the ESR signals at various microwave power levels were indicative of different relaxation time for those radicals. The anisotropic ESR spectra were detected by the angular rotation of the sample tube. This is due to the existence of anisotropic microcrystalline in the ginseng powder sample.

An electron spin resonance study of γ-ray irradiated ginseng

NASA Astrophysics Data System (ADS)

Nakamura, Hideo; Ukai, Mitsuko; Shimoyama, Yuhei

2006-03-01

Using electron spin resonance (ESR) spectroscopy, we revealed the presence of four radical species in γ-ray irradiated ginseng ( Agaliaceae). Before irradiation, the representative ESR spectrum of ginseng is composed of a sextet centered at g = 2.0, a sharp singlet at the same g-value, and a singlet at about g = 4.0. The first one is attributable to a hyperfine (hf) signal of Mn 2+ ion (hf constant: 7.4 mT). The second one is due to an organic free radical. The third one is originated from Fe 3+. Upon γ-ray irradiation, a new ESR (the fourth) signal was detectable in the vicinity of g = 2.0 region. The progressive saturation behaviors of the ESR signals at various microwave power levels were indicative of different relaxation time for those radicals. The anisotropic ESR spectra were detected by the angular rotation of the sample tube. This is due to the existence of anisotropic microcrystalline in the ginseng powder sample.

Systematics of nuclear ground state properties in 78-100Sr by laser spectroscopy

NASA Astrophysics Data System (ADS)

Buchinger, F.; Ramsay, E. B.; Arnold, E.; Neu, W.; Neugart, R.; Wendt, K.; Silverans, R. E.; Lievens, P.; Vermeeren, L.; Berdichevsky, D.; Fleming, R.; Sprung, D. W. L.; Ulm, G.

1990-06-01

Hyperfine structures and isotope shifts of strontium isotopes with A=78 to A=98 and A=100 were measured by collinear fast beam laser spectroscopy. Nuclear spins, moments and changes in mean square charge radii are extracted from the data. The spins and moments of most of the odd isotopes are explained in the framework of the single particle model. The changes in mean square charge radii are compared with predictions of the droplet model and of Hartree-Fock-plus-BCS calculations. For the isotopes in the transitional regions below and above the N=50 shell closure, the inclusion of quadrupole zero point motion in the Droplet model describes part of the observed shell effect. An additional change in the surface region of the charge distribution at spherical shape is suggested by the microscopic model. Furthermore, we propose that the isotopes 78Sr and 80Sr may show an unusual shape-sharing structure, with different mean deformations in the ground and 2+1 excited states.

Potential description of charmonium and charmed-strange mesons from lattice QCD

NASA Astrophysics Data System (ADS)

Kawanai, Taichi; Sasaki, Shoichi

2015-11-01

We present spin-independent and spin-spin interquark potentials for the charmonium and charmed-strange mesons, which are calculated in 2 +1 flavor lattice QCD simulations using the PACS-CS gauge configurations generated at the lightest pion mass (Mπ≈156 (7 ) MeV ) with a lattice cutoff of a-1≈2.2 GeV and a spatial volume of (3 fm )3 . For the charm quark, we use a relativistic heavy quark (RHQ) action with fine tuned RHQ parameters, which closely reproduce both the experimental spin-averaged mass and hyperfine splitting of the 1 S charmonium. The interquark potential and the quark kinetic mass, both of which are key ingredients within the potential description of heavy-heavy and heavy-light mesons, are determined from the equal-time Bethe-Salpeter (BS) amplitude. The charmonium potentials are obtained from the BS wave function of 1 S charmonia (ηc and J /ψ mesons), while the charmed-strange potential are calculated from the Ds and Ds* heavy-light mesons. We then use resulting potentials and quark masses as purely theoretical inputs so as to solve the nonrelativistic Schrödinger equation for calculating accessible energy levels of charmonium and charmed-strange mesons without unknown parameters. The resultant spectra below the D D ¯ and D K thresholds excellently agree with well-established experimental data.

High-Frequency EPR and ENDOR Spectroscopy on Semiconductor Quantum Dots.

PubMed

Baranov, Pavel G; Orlinskii, Sergei B; de Mello Donegá, Celso; Schmidt, Jan

2010-10-01

It is shown that high-frequency electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy are excellent tools for the investigation of the electronic properties of semiconductor quantum dots (QDs). The great attractions of these techniques are that, in contrast to optical methods, they allow the identification of the dopants and provide information about the spatial distribution of the electronic wave function. This latter aspect is particularly attractive because it allows for a quantitative measurement of the effect of confinement on the shape and properties of the wave function. In this contribution EPR and ENDOR results are presented on doped ZnO QDs. Shallow donors (SDs), related to interstitial Li and Na and substitutional Al atoms, have been identified in this material by pulsed high-frequency EPR and ENDOR spectroscopy. The shallow character of the wave function of the donors is evidenced by the multitude of ENDOR transitions of the (67)Zn nuclear spins and by the hyperfine interaction of the (7)Li, (23)Na and (27)Al nuclear spins that are much smaller than for atomic lithium, sodium and aluminium. The EPR signal of an exchange-coupled pair consisting of a shallow donor and a deep Na-related acceptor has been identified in ZnO nanocrystals with radii smaller than 1.5 nm. From ENDOR experiments it is concluded that the deep Na-related acceptor is located at the interface of the ZnO core and the Zn(OH)(2) capping layer, while the shallow donor is in the ZnO core. The spatial distribution of the electronic wave function of a shallow donor in ZnO semiconductor QDs has been determined in the regime of quantum confinement by using the nuclear spins as probes. Hyperfine interactions as monitored by ENDOR spectroscopy quantitatively reveal the transition from semiconductor to molecular properties upon reduction of the size of the nanoparticles. In addition, the effect of confinement on the g-factor of SDs in ZnO as well as in CdS QDs is observed. Finally, it is shown that an almost complete dynamic nuclear polarization (DNP) of the (67)Zn nuclear spins in the core of ZnO QDs and of the (1)H nuclear spins in the Zn(OH)(2) capping layer can be obtained. This DNP is achieved by saturating the EPR transition of SDs present in the QDs with resonant high-frequency microwaves at low temperatures. This nuclear polarization manifests itself as a hole and an antihole in the EPR absorption line of the SD in the QDs and a shift of the hole (antihole). The enhancement of the nuclear polarization opens the possibility to study semiconductor nanostructures with nuclear magnetic resonance techniques.

High-Frequency EPR and ENDOR Spectroscopy on Semiconductor Quantum Dots

PubMed Central

Baranov, Pavel G.; de Mello Donegá, Celso; Schmidt, Jan

2010-01-01

It is shown that high-frequency electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy are excellent tools for the investigation of the electronic properties of semiconductor quantum dots (QDs). The great attractions of these techniques are that, in contrast to optical methods, they allow the identification of the dopants and provide information about the spatial distribution of the electronic wave function. This latter aspect is particularly attractive because it allows for a quantitative measurement of the effect of confinement on the shape and properties of the wave function. In this contribution EPR and ENDOR results are presented on doped ZnO QDs. Shallow donors (SDs), related to interstitial Li and Na and substitutional Al atoms, have been identified in this material by pulsed high-frequency EPR and ENDOR spectroscopy. The shallow character of the wave function of the donors is evidenced by the multitude of ENDOR transitions of the 67Zn nuclear spins and by the hyperfine interaction of the 7Li, 23Na and 27Al nuclear spins that are much smaller than for atomic lithium, sodium and aluminium. The EPR signal of an exchange-coupled pair consisting of a shallow donor and a deep Na-related acceptor has been identified in ZnO nanocrystals with radii smaller than 1.5 nm. From ENDOR experiments it is concluded that the deep Na-related acceptor is located at the interface of the ZnO core and the Zn(OH)2 capping layer, while the shallow donor is in the ZnO core. The spatial distribution of the electronic wave function of a shallow donor in ZnO semiconductor QDs has been determined in the regime of quantum confinement by using the nuclear spins as probes. Hyperfine interactions as monitored by ENDOR spectroscopy quantitatively reveal the transition from semiconductor to molecular properties upon reduction of the size of the nanoparticles. In addition, the effect of confinement on the g-factor of SDs in ZnO as well as in CdS QDs is observed. Finally, it is shown that an almost complete dynamic nuclear polarization (DNP) of the 67Zn nuclear spins in the core of ZnO QDs and of the 1H nuclear spins in the Zn(OH)2 capping layer can be obtained. This DNP is achieved by saturating the EPR transition of SDs present in the QDs with resonant high-frequency microwaves at low temperatures. This nuclear polarization manifests itself as a hole and an antihole in the EPR absorption line of the SD in the QDs and a shift of the hole (antihole). The enhancement of the nuclear polarization opens the possibility to study semiconductor nanostructures with nuclear magnetic resonance techniques. PMID:20936163

Power spectra and auto correlation analysis of hyperfine-induced long period oscillations in the tunneling current of coupled quantum dots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harack, B.; Leary, A.; Coish, W. A.

2013-12-04

We outline power spectra and auto correlation analysis performed on temporal oscillations in the tunneling current of coupled vertical quantum dots. The current is monitored for ∼2325 s blocks as the magnetic field is stepped through a high bias feature displaying hysteresis and switching: hallmarks of the hyperfine interaction. Quasi-periodic oscillations of ∼2 pA amplitude and of ∼100 s period are observed in the current inside the hysteretic feature. Compared to the baseline current outside the hysteretic feature the power spectral density is enhanced by up to three orders of magnitude and the auto correlation displays clear long lived oscillationsmore » about zero.« less

Ultrafast Pulse Sequencing for Fast Projective Measurements of Atomic Hyperfine Qubits

NASA Astrophysics Data System (ADS)

Ip, Michael; Ransford, Anthony; Campbell, Wesley

2015-05-01

Projective readout of quantum information stored in atomic hyperfine structure typically uses state-dependent CW laser-induced fluorescence. This method requires an often sophisticated imaging system to spatially filter out the background CW laser light. We present an alternative approach that instead uses simple pulse sequences from a mode-locked laser to affect the same state-dependent excitations in less than 1 ns. The resulting atomic fluorescence occurs in the dark, allowing the placement of non-imaging detectors right next to the atom to improve the qubit state detection efficiency and speed. We also discuss methods of Doppler cooling with mode-locked lasers for trapped ions, where the creation of the necessary UV light is often difficult with CW lasers.

Exact Mapping from Many-Spin Hamiltonians to Giant-Spin Hamiltonians.

PubMed

Ghassemi Tabrizi, Shadan; Arbuznikov, Alexei V; Kaupp, Martin

2018-03-26

Thermodynamic and spectroscopic data of exchange-coupled molecular spin clusters (e.g. single-molecule magnets) are routinely interpreted in terms of two different models: the many-spin Hamiltonian (MSH) explicitly considers couplings between individual spin centers, while the giant-spin Hamiltonian (GSH) treats the system as a single collective spin. When isotropic exchange coupling is weak, the physical compatibility between both spin Hamiltonian models becomes a serious concern, due to mixing of spin multiplets by local zero-field splitting (ZFS) interactions ('S-mixing'). Until now, this effect, which makes the mapping MSH→GSH ('spin projection') non-trivial, had only been treated perturbationally (up to third order), with obvious limitations. Here, based on exact diagonalization of the MSH, canonical effective Hamiltonian theory is applied to construct a GSH that exactly matches the energies of the relevant (2S+1) states comprising an effective spin multiplet. For comparison, a recently developed strategy for the unique derivation of effective ('pseudospin') Hamiltonians, now routinely employed in ab initio calculations of mononuclear systems, is adapted to the problem of spin projection. Expansion of the zero-field Hamiltonian and the magnetic moment in terms of irreducible tensor operators (or Stevens operators) yields terms of all ranks k (up to k=2S) in the effective spin. Calculations employing published MSH parameters illustrate exact spin projection for the well-investigated [Ni(hmp)(dmb)Cl] 4 ('Ni 4 ') single-molecule magnet, which displays weak isotropic exchange (dmb=3,3-dimethyl-1-butanol, hmp - is the anion of 2-hydroxymethylpyridine). The performance of the resulting GSH in finite field is assessed in terms of EPR resonances and diabolical points. The large tunnel splitting in the M=± 4 ground doublet of the S=4 multiplet, responsible for fast tunneling in Ni 4 , is attributed to a Stevens operator with eightfold rotational symmetry, marking the first quantification of a k=8 term in a spin cluster. The unique and exact mapping MSH→GSH should be of general importance for weakly-coupled systems; it represents a mandatory ultimate step for comparing theoretical predictions (e.g. from quantum-chemical calculations) to ZFS, hyperfine or g-tensors from spectral fittings. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lifetime and relative g factor measurements in 104 , 106 , 108Pd isotopes

NASA Astrophysics Data System (ADS)

Ilie, G.; Werner, V.; Radeck, D.; Ahn, T.; Beausang, C. W.; Bettermann, L.; Casperson, R. J.; Chevrier, R.; Cooper, N.; Bonniwell, T. C.; Heinz, A.; Holland, E.; McCarthy, D.; Pauerstein, B.; Smith, M. K.; Terry, J. R.; Williams, E.

2011-10-01

The purpose of this research was the proof-of-principle for the new g-plunger technique to measure the deorientation and the lifetime of a state after an inverse kinematics reaction. The deorientation effect is due to the hyperfine interaction between the nuclear spin and the surrounding electron configurations. The attenuation of γ-ray angular distributions has been measured for the 21+ and 41+ states of 104Pd, 106Pd and 108Pd. The beams with energies of 324 MeV, 330 MeV and 336 MeV, respectively, were Coulomb excited into their 21+ state on a 24Mg target. Forward scattered Mg was detected after passing a Cu foil, which served as a stopper for the beam. We measured the time-dependence of the attenuation as a function of distance, in parallel to measuring the lifetimes of the 21+ and 41+ states. This attenuation is used to measure the g factor of the decaying states relative to each other. In this work, hyperfine parameters have been calibrated for the Pd isotopes. The results of this work and a discussion of the parameterization used to fit the data in this work will be presented. Research was supported by the U.S. Department of Energy under Grant No. DE-FG02-91ER-40609.

Enzymatic mechanisms of biological magnetic sensitivity.

PubMed

Letuta, Ulyana G; Berdinskiy, Vitaly L; Udagawa, Chikako; Tanimoto, Yoshifumi

2017-10-01

Primary biological magnetoreceptors in living organisms is one of the main research problems in magnetobiology. Intracellular enzymatic reactions accompanied by electron transfer have been shown to be receptors of magnetic fields, and spin-dependent ion-radical processes can be a universal mechanism of biological magnetosensitivity. Magnetic interactions in intermediate ion-radical pairs, such as Zeeman and hyperfine (HFI) interactions, in accordance with proposed strict quantum mechanical theory, can determine magnetic-field dependencies of reactions that produce biologically important molecules needed for cell growth. Hyperfine interactions of electrons with nuclear magnetic moments of magnetic isotopes can explain the most important part of biomagnetic sensitivities in a weak magnetic field comparable to the Earth's magnetic field. The theoretical results mean that magnetic-field dependencies of enzymatic reaction rates in a weak magnetic field that can be independent of HFI constant a, if H < a, and are determined by the rate constant of chemical transformations in the enzyme active site. Both Zeeman and HFI interactions predict strong magnetic-field dependence in weak magnetic fields and magnetic-field independence of enzymatic reaction rate constants in strong magnetic fields. The theoretical results can explain the magnetic sensitivity of E. coli cell and demonstrate that intracellular enzymatic reactions are primary magnetoreceptors in living organisms. Bioelectromagnetics. 38:511-521, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Structural investigation and electron paramagnetic resonance of vanadyl doped alkali niobium borate glasses.

PubMed

Agarwal, A; Sheoran, A; Sanghi, S; Bhatnagar, V; Gupta, S K; Arora, M

2010-03-01

Glasses with compositions xNb(2)O(5).(30-x)M(2)O.69B(2)O(3) (where M=Li, Na, K; x=0, 4, 8 mol%) doped with 1 mol% V(2)O(5) have been prepared using normal melt quench technique. The IR transmission spectra of the glasses have been studied over the range 400-4000 cm(-1). The changes caused by the addition of Nb(2)O(5) on the structure of these glasses have been reported. The electron paramagnetic resonance spectra of VO(2+) ions in these glasses have been recorded in X-band (9.14 GHz) at room temperature (300 K). The spin Hamiltonian parameters, dipolar hyperfine coupling parameter and Fermi contact interaction parameter have been calculated. It is observed that the resultant resonance spectra contain hyperfine structures (hfs) due to V(4+) ions which exist as VO(2+) ions in octahedral coordination with a tetragonal compression in the present glasses. The tetragonality of V(4+)O(6) complex decreases with increasing concentration of Nb(2)O(5). The 3d(xy) orbit contracts with increase in Nb(2)O(5):M(2)O ratio. Values of the theoretical optical basicity, Lambda(th), have also been reported. Copyright 2009 Elsevier B.V. All rights reserved.

Study of atomic coherence effects in multi-level V+Ξ system involving Rydberg state

NASA Astrophysics Data System (ADS)

Kaur, Amanjot; Singh, Neeraj; Kaur, Paramjit

2018-06-01

We present theoretical model to investigate the influence of hyperfine levels on the atomic coherences of V+Ξ Rydberg system. Using density matrix formulation, an analytical expression of atomic coherence for weak probe field is derived. The closely spaced hyperfine levels cause asymmetry and red shift while wavelength mismatching induced due to Rydberg state leads to reduction in magnitude and broadening of group index, absorption and dispersion profiles for moving atoms. Our system shows both Rydberg Electromagnetically induced transparency (EIT) with subluminal behavior and Rydberg Electromagnetically induced absorption (EIA) with superluminal propagation by adjusting the strengths of control and switching fields. Variation of group index with probe detuning reveals anomalous dispersion regions at Autler-Townes doublet positions. Group index for Doppler-broadened atoms at resonance condition has lower magnitude as compared to the stationary atoms and hence the group delay time of the pulse is also reduced. We also explore in-depth non-degenerate four-wave mixing (FWM) which is ignited due to the presence of three electromagnetic (e.m.) fields and concurrently, establish relationship between FWM and multi-photon atomic coherence. The transient behavior is also studied for practical realization of our considered system as optical switch.

Spin-orbit-torque-induced skyrmion dynamics for different types of spin-orbit coupling

NASA Astrophysics Data System (ADS)

Lee, Seung-Jae; Kim, Kyoung-Whan; Lee, Hyun-Woo; Lee, Kyung-Jin

2018-06-01

We investigate current-induced skyrmion dynamics in the presence of Dzyaloshinskii-Moriya interaction and spin-orbit spin-transfer torque corresponding to various types of spin-orbit coupling. We determine the symmetries of Dzyaloshinskii-Moriya interaction and spin-orbit spin-transfer torque based on linear spin-orbit coupling model. We find that like interfacial Dzyaloshinskii-Moriya interaction (Rashba spin-orbit coupling) and bulk Dzyaloshinskii-Moriya interaction (Weyl spin-orbit coupling), Dresselhaus spin-orbit coupling also has a possibility for stabilizing skyrmion and current-induced skyrmion dynamics.

Diode laser spectroscopy of the MnD radical ( 7Σ) and the determination of mass-independent parameters

NASA Astrophysics Data System (ADS)

Urban, Rolf-Dieter; Jones, Harold

1991-03-01

The infrared spectrum of the manganese deuteride radical has been observed in its ground electronic state ( 7Σ) using a diode-laser spectrometer. The hyperfine structure of a number of infrared transitions in the bands ν=1←0, ν=2←1 and ν=3←2 were measured with a nominal accuracy of ±0.001 cm -1. In all cases, the complete structure was easily resolved. Dunham parameters, spin—rotation and spin—spin coupling parameters were determined from the MnD data. A simultaneous fit of these data with those determined previously for MnH was carried out to determine mass-independent parameters and mass-scaling coefficients.

Fine- and hyperfine structure investigations of even configuration system of atomic terbium

NASA Astrophysics Data System (ADS)

Stefanska, D.; Elantkowska, M.; Ruczkowski, J.; Furmann, B.

2017-03-01

In this work a parametric study of the fine structure (fs) and the hyperfine structure (hfs) for the even-parity configurations of atomic terbium (Tb I) is presented, based in considerable part on the new experimental results. Measurements on 134 spectral lines were performed by laser induced fluorescence (LIF) in a hollow cathode discharge lamp; on this basis, the hyperfine structure constants A and B were determined for 52 even-parity levels belonging to the configurations 4f85d6s2, 4f85d26s or 4f96s6p; in all the cases those levels were involved in the transitions investigated as the lower levels. For 40 levels the hfs was examined for the first time, and for the remaining 12 levels the new measurements supplement our earlier results. As a by-product, also preliminary values of the hfs constants for 84 odd-parity levels were determined (the investigations of the odd-parity levels system in the terbium atom are still in progress). This huge amount of new experimental data, supplemented by our earlier published results, were considered for the fine and hyperfine structure analysis. A multi-configuration fit of 7 configurations was performed, taking into account second-order of perturbation theory, including the effects of closed shell-open shell excitations. Predicted values of the level energies, as well as of magnetic dipole and electric quadrupole hyperfine structure constants A and B, are quoted in cases when no experimental values are available. By combining our experimental data with our own semi-empirical procedure it was possible to identify correctly the lower and upper level of the line 544.1440 nm measured by Childs with the use of the atomic-beam laser-rf double-resonance technique (Childs, J Opt Soc Am B 9;1992:191-6).

Local magnetic moment formation at 119Sn Mössbauer impurity in RFe2 ( R=rare-earth metals) Laves phases compounds

NASA Astrophysics Data System (ADS)

de Oliveira, A. L.; de Oliveira, N. A.; Troper, A.

2010-05-01

The purpose of the present work is to theoretically study the local magnetic moment formation and the systematics of the magnetic hyperfine fields at a non-magnetic s-p Mössbauer 119Sn impurity diluted on R sites ( R=rare-earth metals) of the cubic Laves phases intermetallic compounds RFe2. One considers that the magnetic hyperfine field has two contributions (i) the contribution from R ions, calculated via an extended Daniel-Friedel [J. Phys. Chem. Solids 24 (1963) 1601] model and (ii) the contribution from the induced magnetic moments arising from the Fe neighboring sites. We have in this case a two-center Blandin-Campbell-like [Phys. Rev. Lett. 31 (1973) 51; J. Magn. Magn. Mater. 1 (1975) 1] problem, where a magnetic 3d-element located at a distance from the 119Sn impurity gives an extra magnetization to a polarized electron gas which is strongly charge perturbed at the 119Sn impurity site. We also include in the model, the nearest-neighbor perturbation due to the translational invariance breaking introduced by the impurity. Our self-consistent total magnetic hyperfine field calculations are in a very good agreement with recent experimental data.

Magnetic excitation and local magnetic susceptibility of the excitonic insulator Ta2NiSe5 investigated by 77Se NMR

NASA Astrophysics Data System (ADS)

Li, Shang; Kawai, Shunsuke; Kobayashi, Yoshiaki; Itoh, Masayuki

2018-04-01

77Se NMR measurements were made on polycrystalline and single-crystalline samples to elucidate local magnetic susceptibility and magnetic excitation of Ta2NiSe5 , which is proposed to undergo an exciton condensation accompanied by a structural transition at Tc=328 K . We determine the 77Se Knight shift tensors for the three Se sites and analyze their anisotropy based on the site symmetry. The temperature dependence of the Knight shift is discussed on the basis of spin and orbital susceptibilities calculated for two-chain and two-dimensional three-band models. The large fraction of the Se 4 p orbital polarization due to the mixing between Ni 3 d and Se 4 p orbitals is estimated from the analysis of the transferred hyperfine coupling constant. Also the nuclear spin-lattice relaxation rate 1 /T1 is found not to show a coherent peak just below Tc and to obey the thermally activated temperature dependence with a spin gap energy of 1770 ±40 K . This behavior of 1 /T1 monitors the exciton condensation as proposed by the theoretical study of 1 /T1 based on the three-chain Hubbard model for the excitonic insulator.

Sub-millisecond 125Te NMR spin-lattice relaxation times and large Knight shifts in complex tellurides: Validation of a quadratic relation across the spectrum

DOE PAGES

Levin, E. M.; Iowa State Univ., Ames, IA; Cui, J. -F.; ...

2016-07-16

125Te NMR spectra and spin-lattice relaxation times, T 1, have been measured for several GeTe-based materials with Te excess. In this paper, the spectra show inhomogeneous broadening by several thousand ppm and a systematic variation in T 1 relaxation time with resonance frequency. The quadratic dependence of the spin-lattice relaxation rate, 1/T 1, on the Knight shift in the Korringa relation is found to be valid over a wide range of Knight shifts. This result confirms that T 1 relaxation in GeTe-based materials is mostly dominated by hyperfine interaction between nuclei and free charge carriers. In GeTe with 2.5% excessmore » of Te, about 15% of the material exhibits a Knight shift of ≥4500 ppm and a T 1 of only 0.3 ms, indicating a high hole concentration that could correspond to close to 50% vacancies on the Ge sublattice in this component. Lastly, our findings provide a basis for determining the charge carrier concentration and its distribution in complex thermoelectric and phase-change tellurides, which should lead to a better understanding of electronic and thermal transport properties as well as chemical bonding in these materials.« less

Isomer Shift and Magnetic Moment of the Long-Lived 1/2^{+} Isomer in _{30}^{79}Zn_{49}: Signature of Shape Coexistence near ^{78}Ni.

PubMed

Yang, X F; Wraith, C; Xie, L; Babcock, C; Billowes, J; Bissell, M L; Blaum, K; Cheal, B; Flanagan, K T; Garcia Ruiz, R F; Gins, W; Gorges, C; Grob, L K; Heylen, H; Kaufmann, S; Kowalska, M; Kraemer, J; Malbrunot-Ettenauer, S; Neugart, R; Neyens, G; Nörtershäuser, W; Papuga, J; Sánchez, R; Yordanov, D T

2016-05-06

Collinear laser spectroscopy is performed on the _{30}^{79}Zn_{49} isotope at ISOLDE-CERN. The existence of a long-lived isomer with a few hundred milliseconds half-life is confirmed, and the nuclear spins and moments of the ground and isomeric states in ^{79}Zn as well as the isomer shift are measured. From the observed hyperfine structures, spins I=9/2 and I=1/2 are firmly assigned to the ground and isomeric states. The magnetic moment μ (^{79}Zn)=-1.1866(10)μ_{N}, confirms the spin-parity 9/2^{+} with a νg_{9/2}^{-1} shell-model configuration, in excellent agreement with the prediction from large scale shell-model theories. The magnetic moment μ (^{79m}Zn)=-1.0180(12)μ_{N} supports a positive parity for the isomer, with a wave function dominated by a 2h-1p neutron excitation across the N=50 shell gap. The large isomer shift reveals an increase of the intruder isomer mean square charge radius with respect to that of the ground state, δ⟨r_{c}^{2}⟩^{79,79m}=+0.204(6)  fm^{2}, providing first evidence of shape coexistence.

Clarification of the different roles of surface anisotropy for thermal spin waves and FMR modes

NASA Astrophysics Data System (ADS)

Rado, G. T.; Walker, J. C.

1982-11-01

Measurements by Mössbauer spectroscopy of the position dependence of the hyperfine field in monocrystalline iron films show that the fractional deviation of the spontaneous magnetization at temperature T from its value at T=0 K is larger by a factor of about two at a film surface than in the film's interior. This result agrees with an early theoretical prediction of a factor of exactly two which is based on the assumption that the surface anisotropy is zero. In contrast, the results of recent ferromagnetic resonance experiments on ultra-thin films of monocrystalline iron were shown to be dominated by a surface anistropy which is nonzero. This discrepancy is reconciled for measurements at T=300 K by making use of the general boundary condition which contains the exchange stiffness A and some component(s) of the surface anisotropy Ksurf. The crucial argument is that at 300 K the thermally excited spin wavelengths are so short that at the film surfaces the normal derivative 2A∂m↘/∂n of the oscillating magnetization m↘ is very much larger than Ksurfm↘. Thus Ksurfm↘ is neglible for thermal spin waves even though it is comparable to 2A∂m↘/∂n for the long decay distances (or wavelengths) occurring in ferromagnetic resonance.

Continuous Diffusion Model for Concentration Dependence of Nitroxide EPR Parameters in Normal and Supercooled Water.

PubMed

Merunka, Dalibor; Peric, Miroslav

2017-05-25

Electron paramagnetic resonance (EPR) spectra of radicals in solution depend on their relative motion, which modulates the Heisenberg spin exchange and dipole-dipole interactions between them. To gain information on radical diffusion from EPR spectra demands both reliable spectral fitting to find the concentration coefficients of EPR parameters and valid expressions between the concentration and diffusion coefficients. Here, we measured EPR spectra of the 14 N- and 15 N-labeled perdeuterated TEMPONE radicals in normal and supercooled water at various concentrations. By fitting the EPR spectra to the functions based on the modified Bloch equations, we obtained the concentration coefficients for the spin dephasing, coherence transfer, and hyperfine splitting parameters. Assuming the continuous diffusion model for radical motion, the diffusion coefficients of radicals were calculated from the concentration coefficients using the standard relations and the relations derived from the kinetic equations for the spin evolution of a radical pair. The latter relations give better agreement between the diffusion coefficients calculated from different concentration coefficients. The diffusion coefficients are similar for both radicals, which supports the presented method. They decrease with lowering temperature slower than is predicted by the Stokes-Einstein relation and slower than the rotational diffusion coefficients, which is similar to the diffusion of water molecules in supercooled water.

The qqqqq components and hidden flavor contributions to the baryon magnetic moments

DOE Office of Scientific and Technical Information (OSTI.GOV)

An, C. S.; Li, Q. B.; Riska, D. O.

2006-11-15

The contributions from the qqqqq components to the magnetic moments of the octet as well as the {delta}{sup ++} and {omega}{sup -} decuplet baryons are calculated for the configurations that are expected to have the lowest energy if the hyperfine interaction depends on both spin and flavor. The contributions from the uu,dd, and the ss components are given separately. It is shown that addition of qqqqq admixtures to the ground state baryons can improve the overall description of the magnetic moments of the baryon octet and decuplet in the quark model without SU(3) flavor symmetry breaking, beyond that of themore » different constituent masses of the strange and light-flavor quarks. The explicit flavor (and spin) wave functions for all the possible configurations of the qqqqq components with light and strange qq pairs are given for the baryon octet and decuplet. Admixtures of {approx}10% of the qqqqq configuration where the flavor-spin symmetry is [4]{sub FS}[22]{sub F}[22]{sub S}, which is likely to have the lowest energy, in particular reduces the deviation from the empirical values of the magnetic moments {sigma}{sup -} and the {xi}{sup 0} compared with the static qqq quark model.« less

Current-induced spin polarization in InGaAs and GaAs epilayers with varying doping densities

NASA Astrophysics Data System (ADS)

Luengo-Kovac, M.; Huang, S.; Del Gaudio, D.; Occena, J.; Goldman, R. S.; Raimondi, R.; Sih, V.

2017-11-01

The current-induced spin polarization and momentum-dependent spin-orbit field were measured in InxGa1 -xAs epilayers with varying indium concentrations and silicon doping densities. Samples with higher indium concentrations and carrier concentrations and lower mobilities were found to have larger electrical spin generation efficiencies. Furthermore, current-induced spin polarization was detected in GaAs epilayers despite the absence of measurable spin-orbit fields, indicating that the extrinsic contributions to the spin-polarization mechanism must be considered. Theoretical calculations based on a model that includes extrinsic contributions to the spin dephasing and the spin Hall effect, in addition to the intrinsic Rashba and Dresselhaus spin-orbit coupling, are found to reproduce the experimental finding that the crystal direction with the smaller net spin-orbit field has larger electrical spin generation efficiency and are used to predict how sample parameters affect the magnitude of the current-induced spin polarization.

Optical Magnetometer Incorporating Photonic Crystals

NASA Technical Reports Server (NTRS)

Kulikov, Igor; Florescu, Lucia

2007-01-01

According to a proposal, photonic crystals would be used to greatly increase the sensitivities of optical magnetometers that are already regarded as ultrasensitive. The proposal applies, more specifically, to a state-of-the-art type of quantum coherent magnetometer that exploits the electromagnetically-induced-transparency (EIT) method for determining a small change in a magnetic field indirectly via measurement of the shift, induced by that change, in the hyperfine levels of resonant atoms exposed to the field.

Hyperfine Fields of 181Ta in UFe4Al8

NASA Astrophysics Data System (ADS)

Marques, J. G.; Barradas, N. P.; Alves, E.; Ramos, A. R.; Gonçalves, A. P.; da Silva, M. F.; Soares, J. C.

2001-11-01

The γ γ Perturbed Angular Correlation technique was used to study the hyperfine interaction of 181Ta at the Hf site(s) in UFe4Al8 at room temperature and 12 K. The data at room temperature are well described by two electric field gradients, while at low temperature two combined hyperfine interactions have to be considered, one with the magnetic hyperfine field collinear with the c-axis and another with the magnetic hyperfine field in the basal plane. The results are compared with previous Mössbauer and neutron diffraction experiments and the lattice site of Hf is discussed.

Lamb shifts and hyperfine structure in 6Li+ and 7Li+: Theory and experiment

NASA Astrophysics Data System (ADS)

Riis, E.; Sinclair, A. G.; Poulsen, O.; Drake, G. W. F.; Rowley, W. R. C.; Levick, A. P.

1994-01-01

High-precision laser-resonance measurements accurate to +/-0.5 MHz or better are reported for transitions among the 1s2s 3S1-1s2p 3PJ hyperfine manifolds for each of J=0, 1, and 2 in both 6Li+ and 7Li+. A detailed analysis of hyperfine structure is performed for both the S and P states, using newly calculated values for the magnetic dipole and electric quadrupole coupling constants, and the hyperfine shifts subtracted from the measurements. The resulting transition frequencies are then analyzed on three different levels. First, the isotope shifts in the fine-structure splittings are calculated from the relativistic reduced mass and recoil terms in the Breit interaction, and compared with experiment at the +/-0.5-MHz level of accuracy. This comparison is particularly significant because J-independent theoretical uncertainties reduce through cancellation to the +/-0.01-MHz level. Second, the isotope shifts in the full transition frequencies are used to deduce the difference in rms nuclear radii. The result is Rrms(6Li)-Rrms(7Li)=0.15+/-0.01 fm, in agreement with nuclear scattering data, but with substantially improved accuracy. Third, high-precision calculations of the low-order non-QED contributions to the transition frequencies are subtracted from the measurements to obtain the residual QED shifts. The isotope-averaged and spin-averaged effective shift for 7Li+ is 37 429.40+/-0.39 MHz, with an additional uncertainty of +/-1.5 MHz due to finite nuclear size corrections. The accuracy of 11 parts per million is the best two-electron Lamb shift measurement in the literature, and is comparable to the accuracies achieved in hydrogen. Theoretical contributions to the two-electron Lamb shift are discussed, including terms of order (αZ)4 recently obtained by Chen, Cheng, and Johnson [Phys. Rev. A 47, 3692 (1993)], and the results used to extract a QED shift for the 2 3S1 state. The result of 30 254+/-12 MHz is shown to be in good accord with theory (30 250+/-30 MHz) when two-electron corrections to the Bethe logarithm are taken into account by a 1/Z expansion method.

Theoretical study of hyperfine coupling constants and electron spin g factors for X2Σ diatomics from Groups 1 and 2

NASA Astrophysics Data System (ADS)

Bruna, Pablo J.; Grein, Friedrich

The ESR parameters of the cations Be 2 + , Mg 2 + , Ca 2 + , BeMg + , BeCa + , MgCa + and the mixed radicals ZBe, ZMg, ZCa (Z = Li, Na, K), all having a X 2 Σu + (1 σg 2 1 σu )/X 2 Sigma + (1 σ2 2 σ) ground state, have been studied theoretically. The A iso and A dip constants have been calculated with UHF, CISD, MP2, B3LYP, PW91PW91 wavefunctions, and 6-311+G(2df) basis sets. The electron spin g factors (magnetic moment μs) have been evaluated from correlated (MRDCI) wavefunctions, using a Hamiltonian based on Breit-Pauli theory with perturbation expansions up to second order, and 6-311+ G(2d) basis sets. As expected for s-rich radicals, the hyperfine spectra are governed by the A iso terms. Both Δg|| and Δg Υ̂values are negative, but Δg|| lies close to zero. For Δg Υ̂, the coupling with 1 2 Π(u) dominates the sum-over-states expansions. Although the singly occupied MOs (SOMO) are mostly of s character, the | Δg Υ̂| are relatively large, up to 5200 ppm for cationic, and up to 7850 ppm for neutral radicals. These large values are caused by low excitation energies and high magnetic transition moments, the latter due to the fact that the σ*( s - s ) SOMO has the same nodal properties as a p σorbital. Of the radicals considered here, an ESR spectrum is available only for Mg2+. Our theoretical A iso of-287 MHz reproduces well the matrix result (-291 MHz). Calculated values of-10 ppm for Deltag|| and of-1280 ppm for Deltag Υ̂give an average < Δg> =-860 ppm that lies within the experimental range of-600( ±300) ppm in Ne, and of-1300( ±500) ppm in Ar matrices.

Rotation Dynamics Do Not Determine the Unexpected Isotropy of Methyl Radical EPR Spectra.

PubMed

Benetis, Nikolas P; Dmitriev, Yurij; Mocci, Francesca; Laaksonen, Aatto

2015-09-03

A simple first-principles electronic structure computation, further qc (quantum chemistry) computation, of the methyl radical gives three equal hf (hyperfine) couplings for the three protons with the unpaired electron. The corresponding dipolar tensors were notably rhombic and had different orientations and regular magnitude components, as they should, but what the overall A-tensor was seen by the electron spin is a different story! The final g = (2.002993, 2.002993, 2.002231) tensor and the hf coupling results obtained in vacuum, at the B3LYP/EPRIII level of theory clearly indicate that in particular the above A = (-65.19, -65.19, 62.54) MHz tensor was axial to a first approximation without considering any rotational dynamics for the CH3. This approximation was not applicable, however, for the trifluoromethyl CF3 radical, a heavier and nonplanar rotor with very anisotropic hf coupling, used here for comparison. Finally, a derivation is presented explaining why there is actually no need for the CH3 radicals to consider additional rotational dynamics in order for the electron to obtain an axially symmetric hf (hyperfine) tensor by considering the simultaneous dipolar couplings of the three protons. An additional consequence is an almost isotropic A-tensor for the electron spin of the CH3 radical. To the best of our knowledge, this point has not been discussed in the literature before. The unexpected isotropy of the EPR parameters of CH3 was solely attributed to the rotational dynamics and was not clearly separated from the overall symmetry of the species. The present theoretical results allowed a first explanation of the "forbidden" satellite lines in the CH3 EPR spectrum. The satellites are a fingerprint of the radical rotation, helping thus in distinguishing the CH3 reorientation from quantum rotation at very low temperatures.

Current-induced spin polarization in InGaAs and GaAs epilayers with varying doping densities

DOE PAGES

Luengo-Kovac, Marta; Huang, Simon; Del Gaudio, Davide; ...

2017-11-16

Here, the current-induced spin polarization and momentum-dependent spin-orbit field were measured in In xGa 1-xAs epilayers with varying indium concentrations and silicon doping densities. Samples with higher indium concentrations and carrier concentrations and lower mobilities were found to have larger electrical spin generation efficiencies. Furthermore, current-induced spin polarization was detected in GaAs epilayers despite the absence of measurable spin-orbit fields, indicating that the extrinsic contributions to the spin-polarization mechanism must be considered. Theoretical calculations based on a model that includes extrinsic contributions to the spin dephasing and the spin Hall effect, in addition to the intrinsic Rashba and Dresselhaus spin-orbitmore » coupling, are found to reproduce the experimental finding that the crystal direction with the smaller net spin-orbit field has larger electrical spin generation efficiency and are used to predict how sample parameters affect the magnitude of the current-induced spin polarization.« less

Current-induced spin polarization in InGaAs and GaAs epilayers with varying doping densities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luengo-Kovac, Marta; Huang, Simon; Del Gaudio, Davide

Here, the current-induced spin polarization and momentum-dependent spin-orbit field were measured in In xGa 1-xAs epilayers with varying indium concentrations and silicon doping densities. Samples with higher indium concentrations and carrier concentrations and lower mobilities were found to have larger electrical spin generation efficiencies. Furthermore, current-induced spin polarization was detected in GaAs epilayers despite the absence of measurable spin-orbit fields, indicating that the extrinsic contributions to the spin-polarization mechanism must be considered. Theoretical calculations based on a model that includes extrinsic contributions to the spin dephasing and the spin Hall effect, in addition to the intrinsic Rashba and Dresselhaus spin-orbitmore » coupling, are found to reproduce the experimental finding that the crystal direction with the smaller net spin-orbit field has larger electrical spin generation efficiency and are used to predict how sample parameters affect the magnitude of the current-induced spin polarization.« less

Emergent spin electromagnetism induced by magnetization textures in the presence of spin-orbit interaction (invited)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tatara, Gen, E-mail: gen.tatara@riken.jp; Nakabayashi, Noriyuki; Graduate School of Science and Engineering, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397 Japan

2014-05-07

Emergent electromagnetic field which couples to electron's spin in ferromagnetic metals is theoretically studied. Rashba spin-orbit interaction induces spin electromagnetic field which is in the linear order in gradient of magnetization texture. The Rashba-induced effective electric and magnetic fields satisfy in the absence of spin relaxation the Maxwell's equations as in the charge-based electromagnetism. When spin relaxation is taken into account besides spin dynamics, a monopole current emerges generating spin motive force via the Faraday's induction law. The monopole is expected to play an important role in spin-charge conversion and in the integration of spintronics into electronics.

Fine- and hyperfine-structure effects in molecular photoionization. II. Resonance-enhanced multiphoton ionization and hyperfine-selective generation of molecular cations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Germann, Matthias; Willitsch, Stefan, E-mail: stefan.willitsch@unibas.ch

2016-07-28

Resonance-enhanced multiphoton ionization (REMPI) is a widely used technique for studying molecular photoionization and producing molecular cations for spectroscopy and dynamics studies. Here, we present a model for describing hyperfine-structure effects in the REMPI process and for predicting hyperfine populations in molecular ions produced by this method. This model is a generalization of our model for fine- and hyperfine-structure effects in one-photon ionization of molecules presented in Paper I [M. Germann and S. Willitsch, J. Chem. Phys. 145, 044314 (2016)]. This generalization is achieved by covering two main aspects: (1) treatment of the neutral bound-bound transition including the hyperfine structuremore » that makes up the first step of the REMPI process and (2) modification of our ionization model to account for anisotropic populations resulting from this first excitation step. Our findings may be used for analyzing results from experiments with molecular ions produced by REMPI and may serve as a theoretical background for hyperfine-selective ionization experiments.« less

Quantum-Chemical Approach to NMR Chemical Shifts in Paramagnetic Solids Applied to LiFePO4 and LiCoPO4.

PubMed

Mondal, Arobendo; Kaupp, Martin

2018-04-05

A novel protocol to compute and analyze NMR chemical shifts for extended paramagnetic solids, accounting comprehensively for Fermi-contact (FC), pseudocontact (PC), and orbital shifts, is reported and applied to the important lithium ion battery cathode materials LiFePO 4 and LiCoPO 4 . Using an EPR-parameter-based ansatz, the approach combines periodic (hybrid) DFT computation of hyperfine and orbital-shielding tensors with an incremental cluster model for g- and zero-field-splitting (ZFS) D-tensors. The cluster model allows the use of advanced multireference wave function methods (such as CASSCF or NEVPT2). Application of this protocol shows that the 7 Li shifts in the high-voltage cathode material LiCoPO 4 are dominated by spin-orbit-induced PC contributions, in contrast with previous assumptions, fundamentally changing interpretations of the shifts in terms of covalency. PC contributions are smaller for the 7 Li shifts of the related LiFePO 4 , where FC and orbital shifts dominate. The 31 P shifts of both materials finally are almost pure FC shifts. Nevertheless, large ZFS contributions can give rise to non-Curie temperature dependences for both 7 Li and 31 P shifts.

New developments of the in-source spectroscopy method at RILIS/ISOLDE

NASA Astrophysics Data System (ADS)

Marsh, B. A.; Andel, B.; Andreyev, A. N.; Antalic, S.; Atanasov, D.; Barzakh, A. E.; Bastin, B.; Borgmann, Ch.; Capponi, L.; Cocolios, T. E.; Day Goodacre, T.; Dehairs, M.; Derkx, X.; De Witte, H.; Fedorov, D. V.; Fedosseev, V. N.; Focker, G. J.; Fink, D. A.; Flanagan, K. T.; Franchoo, S.; Ghys, L.; Huyse, M.; Imai, N.; Kalaninova, Z.; Köster, U.; Kreim, S.; Kesteloot, N.; Kudryavtsev, Yu.; Lane, J.; Lecesne, N.; Liberati, V.; Lunney, D.; Lynch, K. M.; Manea, V.; Molkanov, P. L.; Nicol, T.; Pauwels, D.; Popescu, L.; Radulov, D.; Rapisarda, E.; Rosenbusch, M.; Rossel, R. E.; Rothe, S.; Schweikhard, L.; Seliverstov, M. D.; Sels, S.; Sjödin, A. M.; Truesdale, V.; Van Beveren, C.; Van Duppen, P.; Wendt, K.; Wienholtz, F.; Wolf, R. N.; Zemlyanoy, S. G.

2013-12-01

At the CERN ISOLDE facility, long isotope chains of many elements are produced by proton-induced reactions in target materials such as uranium carbide. The Resonance Ionization Laser Ion Source (RILIS) is an efficient and selective means of ionizing the reaction products to produce an ion beam of a chosen isotope. Coupling the RILIS with modern ion detection techniques enables highly sensitive studies of nuclear properties (spins, electromagnetic moments and charge radii) along an isotope chain, provided that the isotope shifts and hyperfine structure splitting of the atomic transitions can be resolved. At ISOLDE the campaign to measure the systematics of isotopes in the lead region (Pb, Bi, Tl and Po) has been extended to include the gold and astatine isotope chains. Several developments were specifically required for the feasibility of the most recent measurements: new ionization schemes (Po, At); a remote controlled narrow line-width mode of operation for the RILIS Ti:sapphire laser (At, Au, Po); isobar free ionization using the Laser Ion Source Trap, LIST (Po); isobar selective particle identification using the multi-reflection time-of-flight mass separator (MR-ToF MS) of ISOLTRAP (Au, At). These are summarized as part of an overview of the current status of the in-source resonance ionization spectroscopy setup at ISOLDE.

Analysis of Bose system in spin-orbit coupled Bose-Fermi mixture to induce a spin current of fermions

NASA Astrophysics Data System (ADS)

Sakamoto, R.; Ono, Y.; Hatsuda, R.; Shiina, K.; Arahata, E.; Mori, H.

2018-03-01

We found that a spin current of fermions could be induced in spin-orbit coupled Bose-Fermi mixture at zero temperature. Since spatial change of the spin structure of the bosons is necessary to induce the spin current of the fermions, we analyzed the ground state of the bosons in the mixture system, using a variational method. The obtained phase diagram indicated the presence of a bosonic phase that allowed the fermions to have a spin current.

Designing defect-based qubit candidates in wide-gap binary semiconductors for solid-state quantum technologies

NASA Astrophysics Data System (ADS)

Seo, Hosung; Ma, He; Govoni, Marco; Galli, Giulia

2017-12-01

The development of novel quantum bits is key to extending the scope of solid-state quantum-information science and technology. Using first-principles calculations, we propose that large metal ion-vacancy pairs are promising qubit candidates in two binary crystals: 4 H -SiC and w -AlN. In particular, we found that the formation of neutral Hf- and Zr-vacancy pairs is energetically favorable in both solids; these defects have spin-triplet ground states, with electronic structures similar to those of the diamond nitrogen-vacancy center and the SiC divacancy. Interestingly, they exhibit different spin-strain coupling characteristics, and the nature of heavy metal ions may allow for easy defect implantation in desired lattice locations and ensure stability against defect diffusion. To support future experimental identification of the proposed defects, we report predictions of their optical zero-phonon line, zero-field splitting, and hyperfine parameters. The defect design concept identified here may be generalized to other binary semiconductors to facilitate the exploration of new solid-state qubits.

Distinguishing polymorphs of the semiconducting pigment copper phthalocyanine by solid-state NMR and Raman spectroscopy.

PubMed

Shaibat, Medhat A; Casabianca, Leah B; Siberio-Pérez, Diana Y; Matzger, Adam J; Ishii, Yoshitaka

2010-04-08

Cu(II)(phthalocyanine) (CuPc) is broadly utilized as an archetypal molecular semiconductor and is the most widely used blue printing pigment. CuPc crystallizes in six different forms; the chemical and physical properties are substantially modulated by its molecular packing among these polymorphs. Despite the growing importance of this system, spectroscopic identification of different polymorphs for CuPc has posed difficulties. This study presents the first example of spectroscopic distinction of alpha- and beta-forms of CuPc, the most widely used polymorphs, by solid-state NMR (SSNMR) and Raman spectroscopy. (13)C high-resolution SSNMR spectra of alpha- and beta-CuPc using very-fast magic angle spinning (VFMAS) at 20 kHz show that hyperfine shifts sensitively reflect polymorphs of CuPc. The experimental results were confirmed by ab initio chemical shift calculations. (13)C and (1)H SSNMR relaxation times of alpha- and beta-CuPc under VFMAS also showed marked differences, presumably because of the difference in electronic spin correlation times in the two forms. Raman spectroscopy also provided another reliable method of differentiation between the two polymorphs.

N-VSi-related center in non-irradiated 6H SiC nanostructure

NASA Astrophysics Data System (ADS)

Bagraev, Nikolay; Danilovskii, Eduard; Gets, Dmitrii; Kalabukhova, Ekaterina; Klyachkin, Leonid; Malyarenko, Anna; Savchenko, Dariya; Shanina, Bella

2014-02-01

We present the first findings of the vacancy-related centers identified by the electron spin resonance (ESR) and electrically-detected (ED) ESR method in the non-irradiated 6H-SiC nanostructure. This planar 6H-SiC nanostructure represents the ultra-narrow p-type quantum well confined by the δ-barriers heavily doped with boron on the surface of the n-type 6H-SiC (0001) wafer. The EDESR method by measuring the only magnetoresistance of the 6H SiC nanostructure under the high frequency generation from the δ-barriers appears to allow the identification of the silicon vacancy centers as well as the triplet center with spin state S=1. The same triplet center that is characterized by the larger value of the zero-field splitting constant D and anisotropic g-factor is revealed by the ESR (X-band) method. The hyperfine (hf) lines in the ESR and EDESR spectra originating from the hf interaction with the 14N nucleus allow us to attribute this triplet center to the N-VSi defect.

Mass spectra and decay properties of the c\\bar{c} meson

NASA Astrophysics Data System (ADS)

Chaturvedi, Raghav; Kumar Rai, Ajay

2018-06-01

In this article we present the result of c\\bar{c} meson mass calculation by solving the Schrödinger equation numerically considering the Coulomb plus linear potential. The spin-hyperfine, spin-orbit and tensor components of one-gluon-exchange interactions are employed to obtain the mass spectra of c\\bar{c} meson. The calculated mass spectra are compared with the latest results of PDG and are found to be in good accordance. The Regge trajectories of the calculated mass spectra have also been constructed. The values of the wave function are extracted and employed to calculate the leptonic decay constant, γγ, gg, e+e-, light hadron (LH) and γγγ decay widths of S-wave 0^{-+} and 1^{- -} states of c\\bar{c} meson, the widths have been calculated by Van Royen-Weisskopf formula and by NRQCD mechanism incorporating relativistic corrections of order ν2. The γγ and gg decay widths of χ0 and χ2 states of c\\bar{c} meson have also been calculated. The calculated decay constants and widths have been compared with the experimental results.

Silicon vacancy-related centers in non-irradiated 6H-SiC nanostructure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bagraev, N. T., E-mail: Impurity.Dipole@mail.ioffe.ru; Danilovskii, E. Yu.; Gets, D. S.

2015-05-15

We present the first findings of the silicon vacancy related centers identified in the non-irradiated 6H-SiC nanostructure using the electron spin resonance (ESR) and electrically-detected (ED) ESR technique. This planar 6H-SiC nanostructure represents the ultra-narrow p-type quantum well confined by the δ-barriers heavily doped with boron on the surface of the n-type 6H-SiC(0001) wafer. The new EDESR technique by measuring the only magnetoresistance of the 6H-SiC nanostructure under the high frequency generation from the δ-barriers appears to allow the identification of the isolated silicon vacancy centers as well as the triplet center with spin state S = 1. The samemore » triplet center that is characterized by the large value of the zero-field splitting constant D and anisotropic g-factor is revealed by the ESR (X-band) method. The hyperfine (HF) lines in the ESR and EDESR spectra originating from the HF interaction with the {sup 14}N nucleus seem to attribute this triplet center to the N-V{sub Si} defect.« less

Spin Polarization Spectroscopy of Alkali-Noble Gas Interatomic Potentials

NASA Astrophysics Data System (ADS)

Mironov, Andrey E.; Goldshlag, William; Eden, J. Gary

2017-06-01

We report a new laser spectroscopic technique capable of detecting weak state-state interactions in diatomic molecules. Specifically, a weak interaction has been observed between the 6pσ antibonding orbital of the CsXe (B ^2Σ^+_{1/2}) state and a 5dσ MO associated with a 5dΛ (Λ = 0, 1) state. Thermal Cs-rare gas collision pairs are photoexcited by a circularly-polarized optical field having a wavelength within the B ^2Σ^+_{1/2} \\longleftarrow X ^2Σ^+_{1/2} (free\\longleftarrowfree) continuum. Subsequent dissociation of the B ^2Σ^+_{1/2} transient diatomic selectively populates the F= 4, 5 hyperfine levels of the Cs 6p ^2P_{3/2} state, and circularly-polarized (σ^+) amplified spontaneous emission (ASE) is generated on the Cs D_2 line. The dependence of Cs 6p spin polarization on the Cs(6p)-Xe internuclear separation (R), clearly shows an interaction between the CsXe(B ^2Σ^+_{1/2}) state and a 5dΛ (Λ = 0, 1) potential of the diatomic molecule.

Nuclear resonant forward scattering of synchrotron radiation by randomly oriented iron complexes which exhibit nuclear Zeeman interaction

NASA Astrophysics Data System (ADS)

Haas, M.; Realo, E.; Winkler, H.; Meyer-Klaucke, W.; Trautwein, A. X.; Leupold, O.; Rüter, H. D.

1997-12-01

An expression for the amplitude of a pulse of synchrotron radiation (SR) coherently scattered in forward direction by a randomly oriented Mössbauer absorber is derived from the theory of γ optics. It is assumed that the hyperfine splittings present in the Mössbauer nuclei can be described in the framework of the spin-Hamiltonian formalism. In the general case of a thick Mössbauer sample, which consists of randomly oriented paramagnetic iron-containing molecules (for example, a frozen solution of a 57Fe protein) in an applied magnetic field, the response of this sample on an incident monochromatic and fully polarized SR beam cannot be given analytically because of the integrations involved. The way to evaluate nuclear forward-scattering spectra for this general case numerically is outlined and results of calculations with a corresponding program package called SYNFOS are shown and compared with experimental results obtained by measurements of the high-spin iron (II) ``picket-fence'' porphyrin [Fe(CH3COO)TPpivP]- in an applied field of 6 T.

Intermediates in the reaction of substrate-free cytochrome P450cam with peroxy acetic acid.

PubMed

Schünemann, V; Jung, C; Trautwein, A X; Mandon, D; Weiss, R

2000-08-18

Freeze-quenched intermediates of substrate-free cytochrome 57Fe-P450(cam) in reaction with peroxy acetic acid as oxidizing agent have been characterized by EPR and Mossbauer spectroscopy. After 8 ms of reaction time the reaction mixture consists of approximately 90% of ferric low-spin iron with g-factors and hyperfine parameters of the starting material; the remaining approximately 10% are identified as a free radical (S' = 1/2) by its EPR and as an iron(IV) (S= 1) species by its Mossbauer signature. After 5 min of reaction time the intermediates have disappeared and the Mossbauer and EPR-spectra exhibit 100% of the starting material. We note that the spin-Hamiltonian analysis of the spectra of the 8 ms reactant clearly reveals that the two paramagnetic species, e.g. the ferryl (iron(IV)) species and the radical, are not exchanged coupled. This led to the conclusion that under the conditions used, peroxy acetic acid oxidized a tyrosine residue (probably Tyr-96) into a tyrosine radical (Tyr*-96), and the iron(III) center of substrate-free P450(cam) to iron(IV).

Study of nanostructural organization of ionic liquids by electron paramagnetic resonance spectroscopy.

PubMed

Merunka, Dalibor; Peric, Mirna; Peric, Miroslav

2015-02-19

The X-band electron paramagnetic resonance spectroscopy (EPR) of a stable, spherical nitroxide spin probe, perdeuterated 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (pDTO) has been used to study the nanostructural organization of a series of 1-alkyl-3-methylimidazolium tetrafluoroborate ionic liquids (ILs) with alkyl chain lengths from two to eight carbons. By employing nonlinear least-squares fitting of the EPR spectra, we have obtained values of the rotational correlation time and hyperfine coupling splitting of pDTO to high precision. The rotational correlation time of pDTO in ILs and squalane, a viscous alkane, can be fit very well to a power law functionality with a singular temperature, which often describes a number of physical quantities measured in supercooled liquids. The viscosity of the ILs and squalane, taken from the literature, can also be fit to the same power law expression, which means that the rotational correlation times and the ionic liquid viscosities have similar functional dependence on temperature. The apparent activation energy of both the rotational correlation time of pDTO and the viscous flow of ILs and squalane increases with decreasing temperature; in other words, they exhibit strong non-Arrhenius behavior. The rotational correlation time of pDTO as a function of η/T, where η is the shear viscosity and T is the temperature, is well described by the Stokes-Einstein-Debye (SED) law, while the hydrodynamic probe radii are solvent dependent and are smaller than the geometric radius of the probe. The temperature dependence of hyperfine coupling splitting is the same in all four ionic liquids. The value of the hyperfine coupling splitting starts decreasing with increasing alkyl chain length in the ionic liquids in which the number of carbons in the alkyl chain is greater than four. This decrease together with the decrease in the hydrodynamic radius of the probe indicates a possible existence of nonpolar nanodomains.

Demonstration of the production of oxygen-centered free radicals during electrolysis using E.S.R. spin-trapping techniques: effects on cardiac function in the isolated rat heart.

PubMed

Lecour, S; Baouali, A B; Maupoil, V; Chahine, R; Abadie, C; Javouhey-Donzel, A; Rochette, L; Nadeau, R

1998-03-01

The present study was designed to identify the free radicals generated during the electrolysis of the solution used to perfuse isolated rat heart Langendorff preparations. The high reactivity and very short half-life of oxygen free radicals make their detection and identification difficult. A diamagnetic organic molecule (spin trap) can be used to react with a specific radical to produce a more stable secondary radical or "spin adduct" detected by electron spin resonance (ESR). Isovolumic left ventricular systolic pressure (LVSP) and left ventricular end diastolic pressure (LVEDP) were measured by a fluid-filled latex balloon inserted into the left ventricle. The coronary flow was measured by effluent collection. Electrolysis was performed with constant currents of 0.5, 1, 1.5, 3, 5, 7.5, and 10 mA generated by a Grass stimulator and applied to the perfusion solution for 1 min. A group of experiments was done using a 1.5 mA current and a Krebs-Henseleit (K-H) solution containing free radical scavengers (superoxide dismutase (SOD): 100 IU/ml or mannitol: 50 mM). Heart function rapidly declined in hearts perfused with K-H buffer that had been electrolyzed for 1 min. The addition of mannitol (50 mM) to the perfusion solution had no effect on baseline cardiac function before electrolysis while SOD (100 IU/ml) increased the coronary flow. However, SOD was more effective than the mannitol in protecting the heart against decreased of cardiac function, 5 min after the end of electrolysis. Samples of the K-H medium subjected to electrolysis were collected in cuvettes containing a final concentration of 125 mM 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and analyzed by spectroscopy. The ESR spectrum consisted of a quartet signal (hyperfine couplings aN = aH = 14.9 G) originating from the hydroxyl adduct signal, DMPO-OH. The intensity of the DMPO-OH signal remained stable during the 60 s of electrolysis and the quantity of free radicals induced by electrolysis was directly proportional to the intensity of the current. The addition of mannitol and SOD to the perfusate scavenged the hydroxyl radicals present in the solution, suggesting that both hydroxyl and superoxide radicals were formed during electrolysis.

Monovacancy paramagnetism in neutron-irradiated graphite probed by 13C NMR

NASA Astrophysics Data System (ADS)

Zhang, Z. T.; Xu, C.; Dmytriieva, D.; Molatta, S.; Wosnitza, J.; Wang, Y. T.; Helm, M.; Zhou, Shengqiang; Kühne, H.

2017-11-01

We report on the magnetic properties of monovacancy defects in neutron-irradiated graphite, probed by 13C nuclear magnetic resonance spectroscopy. The bulk paramagnetism of the defect moments is revealed by the temperature dependence of the NMR frequency shift and spectral linewidth, both of which follow a Curie behavior, in agreement with measurements of the macroscopic magnetization. Compared to pristine graphite, the fluctuating hyperfine fields generated by the defect moments lead to an enhancement of the 13C nuclear spin-lattice relaxation rate 1/T1 by about two orders of magnitude. With an applied magnetic field of 7.1 T, the temperature dependence of 1/T1 below about 10 K can well be described by a thermally activated form, \

Superconductivity in LaCu 6 and possible applications

NASA Astrophysics Data System (ADS)

Herrmannsdörfer, Thomas; Pobell, Frank; Sebek, Josef; Svoboda, Pavel

2003-05-01

We have measured the ac susceptibility and resistivity of highly pure samples of the intermetallic compound LaCu6 down to ultralow temperatures. We have prepared the samples by arc melting of stoichiometric amounts of 99.99% La and 99.9999% Cu in a water-cooled copper crucible under Ar protective atmosphere and analysed them by X-ray diffraction and SQUID magnetometry. At T⩽Tc=0.16 K we observe a superconducting transition. Due to the manifold physical properties of isostructural ReCu6 compounds (e.g. RE = Ce: heavy fermion system, RE=Pr: hyperfine enhanced nuclear spin system, RE = Nd: electronic antiferromagnet), numerous studies of interplay phenomena may become possible in the quasibinary compounds RE1-xLaxCu6, respectively.

Collisional excitation of interstellar PO(X2Π) by He: new ab initio potential energy surfaces and scattering calculations

NASA Astrophysics Data System (ADS)

Lique, François; Jiménez-Serra, Izaskun; Viti, Serena; Marinakis, Sarantos

2018-01-01

We present the first ab initio potential energy surfaces (PESs) for the PO(X2Π)-He van der Waals system. The PESs were obtained using the open-shell partially spin-restricted coupled cluster approach with single, double and perturbative triple excitations [UCCSD(T)]. The augmented correlation-consistent polarized valence triple-zeta (aug-cc-pVTZ) basis set was employed supplemented by mid-bond functions. Integral and differential cross sections for the rotational excitation in PO-He collisions were calculated using the new PES and compared with results in similar systems. Finally, our work presents the first hyperfine-resolved cross sections for this system that are needed for accurate modelling in astrophysical environments.

Investigation of giant magnetoconductance in organic devices based on hopping mechanism

NASA Astrophysics Data System (ADS)

Yang, F. J.; Qin, W.; Xie, S. J.

2014-04-01

We suggest a spin-dependent hopping mechanism which includes the effect of the external magnetic field as well as hyperfine interaction (HFI) to explain the observed giant magnetoconductance (MC) in non-magnetic organic devices. Based on the extended Marcus theory, we calculate the MC by using the master equation. It is found that a MC value as large as 91% is obtained under a low driving voltage. For suitable parameters, the theoretical results are in good agreement with the experimental data. Influences of the carrier density, HFI, and the carrier localization on the MC value are investigated. Especially, it is found that a low-dimensional structure of the organic materials is favorable to get a large MC value.

Investigation of giant magnetoconductance in organic devices based on hopping mechanism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, F. J.; Qin, W.; Xie, S. J., E-mail: xsj@sdu.edu.cn

2014-04-14

We suggest a spin-dependent hopping mechanism which includes the effect of the external magnetic field as well as hyperfine interaction (HFI) to explain the observed giant magnetoconductance (MC) in non-magnetic organic devices. Based on the extended Marcus theory, we calculate the MC by using the master equation. It is found that a MC value as large as 91% is obtained under a low driving voltage. For suitable parameters, the theoretical results are in good agreement with the experimental data. Influences of the carrier density, HFI, and the carrier localization on the MC value are investigated. Especially, it is found thatmore » a low-dimensional structure of the organic materials is favorable to get a large MC value.« less

The Nc dependencies of baryon masses: Analysis with Lattice QCD and Effective Theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calle Cordon, Alvaro C.; DeGrand, Thomas A.; Goity, Jose L.

Baryon masses at varying values of Nc and light quark masses are studied with Lattice QCD and the results are analyzed in a low energy effective theory based on a combined framework of the 1/Nc and Heavy Baryon Chiral Perturbation Theory expansions. Lattice QCD results for Nc=3, 5 and 7 obtained in quenched calculations, as well as results for unquenched calculations for Nc=3, are used for the analysis. The results are consistent with a previous analysis of Nc=3 LQCD results, and in addition permit the determination of sub-leading in 1/Nc effects in the spin-flavor singlet component of the baryon massesmore » as well as in the hyperfine splittings.« less

Suppression of Zeeman gradients by nuclear polarization in double quantum dots.

PubMed

Frolov, S M; Danon, J; Nadj-Perge, S; Zuo, K; van Tilburg, J W W; Pribiag, V S; van den Berg, J W G; Bakkers, E P A M; Kouwenhoven, L P

2012-12-07

We use electric dipole spin resonance to measure dynamic nuclear polarization in InAs nanowire quantum dots. The resonance shifts in frequency when the system transitions between metastable high and low current states, indicating the presence of nuclear polarization. We propose that the low and the high current states correspond to different total Zeeman energy gradients between the two quantum dots. In the low current state, dynamic nuclear polarization efficiently compensates the Zeeman gradient due to the g-factor mismatch, resulting in a suppressed total Zeeman gradient. We present a theoretical model of electron-nuclear feedback that demonstrates a fixed point in nuclear polarization for nearly equal Zeeman splittings in the two dots and predicts a narrowed hyperfine gradient distribution.

Ion-Atom Cold Collisions and Atomic Clocks

NASA Technical Reports Server (NTRS)

Prestage, John D.; Maleki, Lute; Tjoelker, Robert L.

1997-01-01

Collisions between ultracold neutral atoms have for some time been the subject of investigation, initially with hydrogen and more recently with laser cooled alkali atoms. Advances in laser cooling and trapping of neutral atoms in a Magneto-Optic Trap (MOT) have made cold atoms available as the starting point for many laser cooled atomic physics investigations. The most spectacularly successful of these, the observation of Bose-Einstein Condensation (BEC) in a dilute ultra-cold spin polarized atomic vapor, has accelerated the study of cold collisions. Experimental and theoretical studies of BEC and the long range interaction between cold alkali atoms is at the boundary of atomic and low temperature physics. Such studies have been difficult and would not have been possible without the development and advancement of laser cooling and trapping of neutral atoms. By contrast, ion-atom interactions at low temperature, also very difficult to study prior to modern day laser cooling, have remained largely unexplored. But now, many laboratories worldwide have almost routine access to cold neutral atoms. The combined technologies of ion trapping, together with laser cooling of neutrals has made these studies experimentally feasible and several very important, novel applications might come out of such investigations . This paper is an investigation of ion-atom interactions in the cold and ultra-cold temperature regime. Some of the collisional ion-atom interactions present at room temperature are very much reduced in the low temperature regime. Reaction rates for charge transfer between unlike atoms, A + B(+) approaches A(+) + B, are expected to fall rapidly with temperature, approximately as T(sup 5/2). Thus, cold mixtures of atoms and ions are expected to coexist for very long times, unlike room temperature mixtures of the same ion-atom combination. Thus, it seems feasible to cool ions via collisions with laser cooled atoms. Many of the conventional collisional interactions, exploited as a useful tool at room temperature and higher, are greatly enhanced at low energy. For example, collisional spin transfer from one species of polarized atoms to another has long been a useful method for polarizing a sample of atoms where no other means was available. Because optical pumping cannot be used to polarize the nuclear spin of Xe-129 or He-3 (for use in nmr imaging of the lungs), the nuclear spins are polarized via collisions with an optically pumped Rb vapor in a cell containing both gases. In another case, a spin polarized thermal Cs beam was used to polarize the hyperfine states of trapped He(+)-3 ions in order to measure their hyperfine clock transition frequency. The absence of an x-ray light source to optically pump the ground state of the He(+)-3 ion necessitated this alternative state preparation. Similarly, Cd(+) and Sr(+) ions were spin-oriented via collisions in a cell with optically pumped Rb vapor. Resonant RF spin changing transitions in the ground state of the ions were detected by changes in the Rb resonance light absorption. Because cold collision spin exchange rates scale with temperature as T(sup -1/2) this technique is expected to be a far more powerful tool than the room temperature counterpart. This factor of 100 or more enhancement in spin exchange reaction rates at low temperatures is the basis for a novel trapped ion clock where laser cooled neutrals will cool, state select and monitor the ion clock transition. The advantage over conventional direct laser cooling of trapped ions is that the very expensive and cumbersome UV laser light sources, required to excite the ionic cooling transition, are effectively replaced by simple diode lasers.

Electron paramagnetic resonance study of radiation-induced paramagnetic centers in succinic anhydride single crystal

NASA Astrophysics Data System (ADS)

Caliskan, Betul; Caliskan, Ali Cengiz; Er, Emine

2017-09-01

Succinic anhydride single crystals were exposed to 60Co-gamma irradiation at room temperature. The irradiated single crystals were investigated at 125 K by Electron Paramagnetic Resonance (EPR) Spectroscopy. The investigation of EPR spectra of irradiated single crystals of succinic anhydride showed the presence of two succinic anhydride anion radicals. The anion radicals observed in gamma-irradiated succinic anhydride single crystal were created by the scission of the carbon-oxygen double bond. The structure of EPR spectra demonstrated that the hyperfine splittings arise from the same radical species. The reduction of succinic anhydride was identified which is formed by the addition of an electron to oxygen of the Csbnd O bond. The g values, the hyperfine structure constants and direction cosines of the radiation damage centers observed in succinic anhydride single crystal were obtained.

The orbital ground state of the azide-substrate complex of human heme oxygenase is an indicator of distal H-bonding: implications for the enzyme mechanism.

PubMed

Ogura, Hiroshi; Evans, John P; Peng, Dungeng; Satterlee, James D; Ortiz de Montellano, Paul R; La Mar, Gerd N

2009-04-14

The active site electronic structure of the azide complex of substrate-bound human heme oxygenase 1 (hHO) has been investigated by (1)H NMR spectroscopy to shed light on the orbital/spin ground state as an indicator of the unique distal pocket environment of the enzyme. Two-dimensional (1)H NMR assignments of the substrate and substrate-contact residue signals reveal a pattern of substrate methyl contact shifts that places the lone iron pi-spin in the d(xz) orbital, rather than the d(yz) orbital found in the cyanide complex. Comparison of iron spin relaxivity, magnetic anisotropy, and magnetic susceptibilities argues for a low-spin, (d(xy))(2)(d(yz),d(xz))(3), ground state in both azide and cyanide complexes. The switch from singly occupied d(yz) for the cyanide to d(xz) for the azide complex of hHO is shown to be consistent with the orbital hole determined by the azide pi-plane in the latter complex, which is approximately 90 degrees in-plane rotated from that of the imidazole pi-plane. The induction of the altered orbital ground state in the azide relative to the cyanide hHO complex, as well as the mean low-field bias of methyl hyperfine shifts and their paramagnetic relaxivity relative to those in globins, indicates that azide exerts a stronger ligand field in hHO than in the globins, or that the distal H-bonding to azide is weaker in hHO than in globins. The Asp140 --> Ala hHO mutant that abolishes activity retains the unusual WT azide complex spin/orbital ground state. The relevance of our findings for other HO complexes and the HO mechanism is discussed.

The orbital ground state of the azide-substrate complex of human heme oxygenase is an indicator of distal H-bonding: Implications for the enzyme mechanism‡

PubMed Central

Ogura, Hiroshi; Evans, John P.; Peng, Dungeng; Satterlee, James D.; de Montellano, Paul R. Ortiz; Mar, Gerd N. La

2009-01-01

The active site electronic structure of the azide complex of substrate-bound human heme oxygenase-1, (hHO) has been investigated by 1H NMR spectroscopy to shed light on the orbital/spin ground state as an indicator of the unique distal pocket environment of the enzyme. 2D 1H NMR assignments of the substrate and substrate-contact residue signals reveal a pattern of substrate methyl contact shifts, that places the lone iron π-spin in the dxz orbital, rather than the dyz orbital found in the cyanide complex. Comparison of iron spin relaxivity, magnetic anisotropy and magnetic susceptibilities argues for a low-spin, (dxy)2(dyz,dxz)3, ground state in both azide and cyanide complexes. The switch from singly-occupied dyz for the cyanide to dxz for the azide complex of hHO is shown to be consistent with the orbital hole determined by the azide π-plane in the latter complex, which is ∼90° in-plane rotated from that of the imidazole π-plane. The induction of the altered orbital ground state in the azide relative to the cyanide hHO complex, as well as the mean low-field bias of methyl hyperfine shifts and their paramagnetic relaxivity relative to those in globins, indicate that azide exerts a stronger ligand field in hHO than in the globins, or that the distal H-bonding to azide is weaker in hHO than in globins. The Asp140 → Ala hHO mutant that abolishes activity retains the unusual WT azide complex spin/orbital ground state. The relevance of our findings for other HO complexes and the HO mechanism is discussed. PMID:19243105

OPTESIM, a Versatile Toolbox for Numerical Simulation of Electron Spin Echo Envelope Modulation (ESEEM) that Features Hybrid Optimization and Statistical Assessment of Parameters

PubMed Central

Sun, Li; Hernandez-Guzman, Jessica; Warncke, Kurt

2009-01-01

Electron spin echo envelope modulation (ESEEM) is a technique of pulsed-electron paramagnetic resonance (EPR) spectroscopy. The analyis of ESEEM data to extract information about the nuclear and electronic structure of a disordered (powder) paramagnetic system requires accurate and efficient numerical simulations. A single coupled nucleus of known nuclear g value (gN) and spin I=1 can have up to eight adjustable parameters in the nuclear part of the spin Hamiltonian. We have developed OPTESIM, an ESEEM simulation toolbox, for automated numerical simulation of powder two- and three-pulse one-dimensional ESEEM for arbitrary number (N) and type (I, gN) of coupled nuclei, and arbitrary mutual orientations of the hyperfine tensor principal axis systems for N>1. OPTESIM is based in the Matlab environment, and includes the following features: (1) a fast algorithm for translation of the spin Hamiltonian into simulated ESEEM, (2) different optimization methods that can be hybridized to achieve an efficient coarse-to-fine grained search of the parameter space and convergence to a global minimum, (3) statistical analysis of the simulation parameters, which allows the identification of simultaneous confidence regions at specific confidence levels. OPTESIM also includes a geometry-preserving spherical averaging algorithm as default for N>1, and global optimization over multiple experimental conditions, such as the dephasing time ( ) for three-pulse ESEEM, and external magnetic field values. Application examples for simulation of 14N coupling (N=1, N=2) in biological and chemical model paramagnets are included. Automated, optimized simulations by using OPTESIM lead to a convergence on dramatically shorter time scales, relative to manual simulations. PMID:19553148

Electromagnetically Induced Absorption (EIA) and a ``Twist'' on Nonlinear Magneto-optical Rotation (NMOR) with Cold Atoms

NASA Astrophysics Data System (ADS)

Kunz, Paul; Meyer, David; Quraishi, Qudsia

2015-05-01

Within the class of nonlinear optical effects that exhibit sub-natural linewidth features, electromagnetically induced transparency (EIT) and nonlinear magneto-optical rotation (NMOR) stand out as having made dramatic impacts on various applications including atomic clocks, magnetometry, and single photon storage. A related effect, known as electromagnetically induced absorption (EIA), has received less attention in the literature. Here, we report on the first observation of EIA in cold atoms using the Hanle configuration, where a single laser beam is used to both pump and probe the atoms while sweeping a magnetic field through zero along the beam direction. We find that, associated with the EIA peak, a ``twist'' appears in the corresponding NMOR signal. A similar twist has been previously noted by Budker et al., in the context of warm vapor optical magnetometry, and was ascribed to optical pumping through nearby hyperfine levels. By studying this feature through numerical simulations and cold atom experiments, thus rendering the hyperfine levels well resolved, we enhance the understanding of the optical pumping mechanism behind it, and elucidate its relation to EIA. Finally, we demonstrate a useful application of these studies through a simple and rapid method for nulling background magnetic fields within our atom chip apparatus.

Hyperfine interactions and electric dipole moments in the [16.0]1.5(v = 6), [16.0]3.5(v = 7), and X2Δ(5/2) states of iridium monosilicide, IrSi.

PubMed

Le, Anh; Steimle, Timothy C; Morse, Michael D; Garcia, Maria A; Cheng, Lan; Stanton, John F

2013-12-19

The (6,0)[16.0]1.5-X(2)Δ(5/2) and (7,0)[16.0]3.5-X(2)Δ(5/2) bands of IrSi have been recorded using high-resolution laser-induced fluorescence spectroscopy. The field-free spectra of the (191)IrSi and (193)IrSi isotopologues were modeled to generate a set of fine, magnetic hyperfine, and nuclear quadrupole hyperfine parameters for the X(2)Δ(5/2)(v = 0), [16.0]1.5(v = 6), and [16.0]3.5 (v = 7) states. The observed optical Stark shifts for the (193)IrSi and (191)IrSi isotopologues were analyzed to produce the permanent electric dipole moments, μ(el), of -0.414(6) D and 0.782(6) D for the X(2)Δ(5/2) and [16.0]1.5 (v = 6) states, respectively. Properties of the X(2)Δ(5/2) state computed using relativistic coupled-cluster methods clearly indicate that electron correlation plays an essential role. Specifically, inclusion of correlation changes the sign of the dipole moment and is essential for achieving good accuracy for the nuclear quadrupole coupling parameter eQq0.

NMR studies of field induced magnetism in CeCoIn5

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graf, Matthias; Curro, Nicholas J; Young, Ben - Li

2009-01-01

Recent Nuclear Magnetic Resonance and elastic neutron scattering experiments have revealed conclusively the presence of static incommensurate magnetism in the field-induced B phase of CeCoIns, We analyze the NMR data assuming the hyperfine coupling to the 1n(2) nuclei is anisotropic and simulate the spectra for several different magnetic structures, The NMR data are consistent with ordered Ce moments along the [001] direction, but are relatively insensitive to the direction of the incommensurate wavevector.

Hyperfine structure in 229gTh3+ as a probe of the 229gTh→ 229mTh nuclear excitation energy.

PubMed

Beloy, K

2014-02-14

We identify a potential means to extract the 229gTh→ 229mTh nuclear excitation energy from precision microwave spectroscopy of the 5F(5/2,7/2) hyperfine manifolds in the ion 229gTh3+. The hyperfine interaction mixes this ground fine structure doublet with states of the nuclear isomer, introducing small but observable shifts to the hyperfine sublevels. We demonstrate how accurate atomic structure calculations may be combined with the measurement of the hyperfine intervals to quantify the effects of this mixing. Further knowledge of the magnetic dipole decay rate of the isomer, as recently reported, allows an indirect determination of the nuclear excitation energy.

III-V semiconductor Quantum Well systems: Physics of Gallium Arsenide two-dimensional hole systems and engineering of mid-infrared Quantum Cascade lasers

NASA Astrophysics Data System (ADS)

Chiu, YenTing

This dissertation examines two types of III-V semiconductor quantum well systems: two-dimensional holes in GaAs, and mid-infrared Quantum Cascade lasers. GaAs holes have a much reduced hyperfine interaction with the nuclei due to the p-like orbital, resulting in a longer hole spin coherence time comparing to the electron spin coherence time. Therefore, holes' spins are promising candidates for quantum computing qubits, but the effective mass and the Lande g-factor, whose product determines the spin-susceptibility of holes, are not well known. In this thesis, we measure the effective hole mass through analyzing the temperature dependence of Shubnikov-de Haas oscillations in a relatively strong interacting two-dimensional hole systems confined to a 20 nm-wide, (311)A GaAs quantum well. The holes in this system occupy two nearly-degenerate spin subbands whose effective mass we measure to be ˜ 0.2 me. We then apply a sufficiently strong parallel magnetic field to fully depopulate one of the spin subbands, and the spin susceptibility of the two-dimensional hole system is deduced from the depopulation field. We also confine holes in closely spaced bilayer GaAs quantum wells to study the interlayer tunneling spectrum as a function of interlayer bias and in-plane magnetic field, in hope of probing the hole's Fermi contour. Quantum Cascade lasers are one of the major mid-infrared light sources well suited for applications in health and environmental sensing. One of the important factors that affect Quantum Cascade laser performance is the quality of the interfaces between the epitaxial layers. What has long been neglected is that interface roughness causes intersubband scattering, and thus affecting the relation between the lifetimes of the upper and lower laser states, which determines if population inversion is possible. We first utilize strategically added interface roughness in the laser design to engineer the intersubband scattering lifetimes. We further experimentally prove the importance of interface roughness on intersubband scattering by measuring the electron transit time of different quantum cascade lasers and comparing them to the calculated upper laser level lifetimes with and without taking into account interface roughness induced intersubband scattering. A significantly better correlation is found between the experimental results and the calculation when the interface roughness scattering is included. Lastly, we study the effect of growth asymmetry on scattering mechanisms in mid-infrared Quantum Cascade lasers. Due to the dopant migration of around 10 nm along the growth direction of InGaAs/InAlAs Quantum Cascade laser structures, ionized impurity scattering is found to have a non-negligible influence on the lifetime of the upper laser level when the laser is biased in the polarity that electrons flow along the growth direction, in sharp contrast to the situation for the opposite polarity.

Mass Dependency of Isotope Fractionation of Gases Under Thermal Gradient and Its Possible Implications for Planetary Atmosphere Escaping Process

NASA Technical Reports Server (NTRS)

Sun, Tao; Niles, Paul; Bao, Huiming; Socki, Richard

2014-01-01

Physical processes that unmix elements/isotopes of gas molecules involve phase changes, diffusion (chemical or thermal), effusion and gravitational settling. Some of those play significant roles for the evolution of chemical and isotopic compositions of gases in planetary bodies which lead to better understanding of surface paleoclimatic conditions, e.g. gas bubbles in Antarctic ice, and planetary evolution, e.g. the solar-wind erosion induced gas escaping from exosphere on terrestrial planets.. A mass dependent relationship is always expected for the kinetic isotope fractionations during these simple physical processes, according to the kinetic theory of gases by Chapman, Enskog and others [3-5]. For O-bearing (O16, -O17, -O18) molecules the alpha O-17/ alpha O-18 is expected at 0.5 to 0.515, and for S-bearing (S32,-S33. -S34, -S36) molecules, the alpha S-33/ alpha S-34 is expected at 0.5 to 0.508, where alpha is the isotope fractionation factor associated with unmixing processes. Thus, one isotope pair is generally proxied to yield all the information for the physical history of the gases. However, we recently] reported the violation of mass law for isotope fractionation among isotope pairs of multiple isotope system during gas diffusion or convection under thermal gradient (Thermal Gradient Induced Non-Mass Dependent effect, TGI-NMD). The mechanism(s) that is responsible to such striking observation remains unanswered. In our past studies, we investigated polyatomic molecules, O2 and SF6, and we suggested that nuclear spin effect could be responsible to the observed NMD effect in a way of changing diffusion coefficients of certain molecules, owing to the fact of negligible delta S-36 anomaly for SF6.. On the other hand, our results also showed that for both diffusion and convection under thermal gradient, this NMD effect is increased by lower gas pressure, bigger temperature gradient and lower average temperature, which indicate that the nuclear spin effect may not be the significant contributor as the energies involved in the hyperfine effect are much smaller than those with molecular collisions, especially under convective conditions.

Nuclear-spin optical rotation in xenon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Savukov, Igor Mykhaylovich

We report that the nuclear-spin optical rotation (NSOR) effect, which has potential applications in correlated nuclear-spin-resonance optical spectroscopy, has previously been explored experimentally and theoretically in liquid Xe. Calculations of the Xe NSOR constant are very challenging because the result is sensitive to correlations, relativistic effects, and the choice of basis, with strong cancellation between contributions from lowest and remaining states. The relativistic configuration-interaction many-body-theory approach, presented here, is promising because this approach has been successful in predicting various properties of noble-gas atoms, such as energies, oscillator strengths (OSs), Verdet constants, and photoionization cross sections. However, correlations become stronger alongmore » the sequence of noble-gas atoms and the theoretical accuracy in Xe is not as high as, for example, in neon and argon. To improve the accuracy of the Xe Verdet and NSOR constants, which are calculated as explicit sums over the excited states, theoretical values for the several lowest levels are replaced with empirical values of energies, OSs, and hyperfine structure constants. We found that the Xe Verdet constant is in excellent agreement with accurate measurements. To take into account liquid effects, empirical data for energy shifts were also used to correct the NSOR constant. In conclusion, the resulting Xe NSOR constant is in a good agreement with experiment, although the liquid-state effect is treated quite approximately.« less

Nuclear-spin optical rotation in xenon

DOE PAGES

Savukov, Igor Mykhaylovich

2015-10-29

We report that the nuclear-spin optical rotation (NSOR) effect, which has potential applications in correlated nuclear-spin-resonance optical spectroscopy, has previously been explored experimentally and theoretically in liquid Xe. Calculations of the Xe NSOR constant are very challenging because the result is sensitive to correlations, relativistic effects, and the choice of basis, with strong cancellation between contributions from lowest and remaining states. The relativistic configuration-interaction many-body-theory approach, presented here, is promising because this approach has been successful in predicting various properties of noble-gas atoms, such as energies, oscillator strengths (OSs), Verdet constants, and photoionization cross sections. However, correlations become stronger alongmore » the sequence of noble-gas atoms and the theoretical accuracy in Xe is not as high as, for example, in neon and argon. To improve the accuracy of the Xe Verdet and NSOR constants, which are calculated as explicit sums over the excited states, theoretical values for the several lowest levels are replaced with empirical values of energies, OSs, and hyperfine structure constants. We found that the Xe Verdet constant is in excellent agreement with accurate measurements. To take into account liquid effects, empirical data for energy shifts were also used to correct the NSOR constant. In conclusion, the resulting Xe NSOR constant is in a good agreement with experiment, although the liquid-state effect is treated quite approximately.« less

Experimental determination of the field shift factor and the mass shift coefficient for the 1S0-3P1 spin-forbidden transition at 791 nm in neutral barium

NASA Astrophysics Data System (ADS)

Yu, Geng-Hua; Yan, Hui; Zhong, Jia-Qi; Liu, Hong; Zhu, Xiao-Ling; Yang, Wei

2018-01-01

The experimental measurements of the isotope shifts (ISs) for the 1S0-3P1 spin-forbidden transition at 791 nm in neutral barium have been carried out with a thermal barium atom beam. The hyperfine structure (HFS) constants a and b of the odd isotopes 137Ba and 135Ba for this transition have been extracted from the experimental results: a(137Ba) = 1149.9(1.0) MHz, b(137Ba)= -41.6(0.5) MHz, a(135Ba) = 1028.0(1.0) MHz, b(135Ba) = -27.5(0.5) MHz. The measured IS results with the reference isotope 138Ba are 183.7(1.0) MHz (137Ba-138Ba), 108.5(0.3) MHz (136Ba-138Ba) and 218.9(1.0) MHz (135Ba-138Ba). Our IS measurements are in good agreement with the previous experiments. The field shift (FS) factor Fk and the mass shift (MS) coefficient ΔKMS for this spin-forbidden transition have be determined experimentally as -3.19(4) GHz ṡ fm-2 and -242(20) GHz ṡ amu, respectively. The results provided herein could be used for further checks theoretically and experimentally, and could also contribute to the study on the nuclear structure of the barium isotopic nuclei.

Inverse scattering transform and soliton solutions for square matrix nonlinear Schrödinger equations with non-zero boundary conditions

NASA Astrophysics Data System (ADS)

Prinari, Barbara; Demontis, Francesco; Li, Sitai; Horikis, Theodoros P.

2018-04-01

The inverse scattering transform (IST) with non-zero boundary conditions at infinity is developed for an m × m matrix nonlinear Schrödinger-type equation which, in the case m = 2, has been proposed as a model to describe hyperfine spin F = 1 spinor Bose-Einstein condensates with either repulsive interatomic interactions and anti-ferromagnetic spin-exchange interactions (self-defocusing case), or attractive interatomic interactions and ferromagnetic spin-exchange interactions (self-focusing case). The IST for this system was first presented by Ieda et al. (2007) , using a different approach. In our formulation, both the direct and the inverse problems are posed in terms of a suitable uniformization variable which allows to develop the IST on the standard complex plane, instead of a two-sheeted Riemann surface or the cut plane with discontinuities along the cuts. Analyticity of the scattering eigenfunctions and scattering data, symmetries, properties of the discrete spectrum, and asymptotics are derived. The inverse problem is posed as a Riemann-Hilbert problem for the eigenfunctions, and the reconstruction formula of the potential in terms of eigenfunctions and scattering data is provided. In addition, the general behavior of the soliton solutions is analyzed in detail in the 2 × 2 self-focusing case, including some special solutions not previously discussed in the literature.

Saturation recovery EPR and ELDOR at W-band for spin labels

PubMed Central

Froncisz, Wojciech; Camenisch, Theodore G.; Ratke, Joseph J.; Anderson, James R.; Subczynski, Witold K.; Strangeway, Robert A.; Sidabras, Jason W.; Hyde, James S.

2008-01-01

A reference-arm W-band (94 GHz) microwave bridge with two sample-irradiation arms for saturation recovery (SR) EPR and ELDOR experiments is described. Frequencies in each arm are derived from 2 GHz synthesizers that have a common time-base and are translated to 94 GHz in steps of 33 and 59 GHz. Intended applications are to nitroxide radical spin labels and spin probes in the liquid phase. An enabling technology is the use of a W-band loop-gap resonator (LGR) (J.W. Sidabras et al., Rev. Sci. Instrum. 78 (2007) 034701). The high efficiency parameter (8.2 GW−1/2 with sample) permits the saturating pump pulse level to be just 5 mW or less. Applications of SR EPR and ELDOR to the hydrophilic spin labels 3-carbamoyl-2,2,5,5-tetra-methyl-3-pyrroline-1-yloxyl (CTPO) and 2,2,6,6,-tetramethyl-4-piperidone-1-oxyl (TEMPONE) are described in detail. In the SR ELDOR experiment, nitrogen nuclear relaxation as well as Heisenberg exchange transfer saturation from pumped to observed hyperfine transitions. SR ELDOR was found to be an essential method for measurements of saturation transfer rates for small molecules such as TEMPONE. Free induction decay (FID) signals for small nitroxides at W-band are also reported. Results are compared with multifrequency measurements of T1e previously reported for these molecules in the range of 2 to 35 GHz (J.S. Hyde et al., J. Phys. Chem. B 108 (2004) 9524–9529). The values of T1e decrease at 94 GHz relative to values at 35 GHz. PMID:18547848

Magnetic and transport properties of heat-treated polyparaphenylene-based carbons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matthews, M.J.; Kobayashi, N.; Dresselhaus, M.S.

1998-07-01

Electron spin resonance (ESR), magnetic susceptibility, and transport measurements were recently performed on a set of heat-treated polyparaphenylene (PPP)-based carbon samples, which are of significant interest as novel carbon-based anode electrodes in Li-ion batteries. Attention is focused on the evolution of the carbonaceous structures formed at low heat-treatment temperatures (T{sub HT}) in the regime of 600 C {le} T{sub HT} {le} 800 C, where percolative transport behavior is observed. At the percolation threshold, T{sub HT}{sup c} {approx} 700 C the coexistence of two spin centers with peak-to-peak Lorentzian linewidths of {Delta}H{sub pp}(300K) = 0.5 and 5.0 G is observed. Themore » relatively high ratio of hydrogen carbon (H/C) near T{sub HT}{sup c} is believed to influence the ESR results through an unresolved hyperfine interaction. Curie-Weiss temperatures are found from measurements of [I{sub pp}({Delta}H{sub pp}){sup 2}]{sup {minus}1}, where I{sub pp} is the peak-to-peak lineheight, yielding results that are in agreement with static susceptibility, {chi}(T), measurements. At low T{sub HT}, PPP-based materials exhibit a large amount of disorder and this is evidenced by the high density of localized spins, N{sub C}, which is obtained from a Curie-Weiss fit to {chi}(T), assuming a spin quantum number of S = {1/2}. A model explaining the microstructure and high electrochemical doping capacity of PPP samples heat-treated to 700 C can be related to Li-ion battery performance.« less

Spin-transfer torque induced spin waves in antiferromagnetic insulators

DOE PAGES

Daniels, Matthew W.; Guo, Wei; Stocks, George Malcolm; ...

2015-01-01

We explore the possibility of exciting spin waves in insulating antiferromagnetic films by injecting spin current at the surface. We analyze both magnetically compensated and uncompensated interfaces. We find that the spin current induced spin-transfer torque can excite spin waves in insulating antiferromagnetic materials and that the chirality of the excited spin wave is determined by the polarization of the injected spin current. Furthermore, the presence of magnetic surface anisotropy can greatly increase the accessibility of these excitations.

Induced Currents in Multiple Resonant Scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruby, Stanley L

We will describe here some results from a MRS scattering model designed to be appropriate for slow resonant scattering. This temporal model is based squarely in induced currents in individual nuclei; a natural consequence is that reradiation into 4{pi} is natural, and does not involve special mechanisms like spin-flips or imperfections of the lattice. Driven by these ideas, we have been able to do experiments where the 4{pi}-shine decay rate around the scattering (FS) slabs is measured simultaneously with the FS rate. Our SS scattering slabs are simple as possible--no hyperfine fields, no crystal structure, and quite static in time.more » Get mainly the one important set of currents jp, an associated FS field Ep, and finally an associated beamlike intensity R{sub fs}(t). But in addition, each current, even jp, contributes to the 4{pi}-shine intensity. This gives quantitative agreement with R{sub 4{pi}}(t), which is rather more complicated than the simple e{sup {minus}t} one might first expect. MRS predicts another set of currents ju, with an associated 4{pi} intensity R{sub 4{pi}}(t). The modifiers refer to unphased and phased. With static SS slabs, this branch is weak, and can be neglected. Driven by these ideas, we have prepared scattering samples where the atoms holding the currents are being stirred about (by diffusion) rather rapidly. This provides a method for dephasing the jp, but also provides a generation rate for ju. The experimental data is not of great quality at this early stage. But the present rough MRS calculations fit easily.« less

Interaction-induced decay of a heteronuclear two-atom system

PubMed Central

Xu, Peng; Yang, Jiaheng; Liu, Min; He, Xiaodong; Zeng, Yong; Wang, Kunpeng; Wang, Jin; Papoular, D. J.; Shlyapnikov, G. V.; Zhan, Mingsheng

2015-01-01

Two-atom systems in small traps are of fundamental interest for understanding the role of interactions in degenerate cold gases and for the creation of quantum gates in quantum information processing with single-atom traps. One of the key quantities is the inelastic relaxation (decay) time when one of the atoms or both are in a higher hyperfine state. Here we measure this quantity in a heteronuclear system of 87Rb and 85Rb in a micro optical trap and demonstrate experimentally and theoretically the presence of both fast and slow relaxation processes, depending on the choice of the initial hyperfine states. This experimental method allows us to single out a particular relaxation process thus provides an extremely clean platform for collisional physics studies. Our results have also implications for engineering of quantum states via controlled collisions and creation of two-qubit quantum gates. PMID:26199051

Theory of in-plane current induced spin torque in metal/ferromagnet bilayers

NASA Astrophysics Data System (ADS)

Sakanashi, Kohei; Sigrist, Manfred; Chen, Wei

2018-05-01

Using a semiclassical approach that simultaneously incorporates the spin Hall effect (SHE), spin diffusion, quantum well states, and interface spin–orbit coupling (SOC), we address the interplay of these mechanisms as the origin of the spin–orbit torque (SOT) induced by in-plane currents, as observed in the normal metal/ferromagnetic metal bilayer thin films. Focusing on the bilayers with a ferromagnet much thinner than its spin diffusion length, such as Pt/Co with  ∼10 nm thickness, our approach addresses simultaneously the two contributions to the SOT, namely the spin-transfer torque (SHE-STT) due to SHE-induced spin injection, and the inverse spin Galvanic effect spin–orbit torque (ISGE-SOT) due to SOC-induced spin accumulation. The SOC produces an effective magnetic field at the interface, hence it modifies the angular momentum conservation expected for the SHE-STT. The SHE-induced spin voltage and the interface spin current are mutually dependent and, hence, are solved in a self-consistent manner. The result suggests that the SHE-STT and ISGE-SOT are of the same order of magnitude, and the spin transport mediated by the quantum well states may be an important mechanism for the experimentally observed rapid variation of the SOT with respect to the thickness of the ferromagnet.

Molecular hyperfine fields in organic magnetoresistance devices

NASA Astrophysics Data System (ADS)

Giro, Ronaldo; Rosselli, Flávia P.; dos Santos Carvalho, Rafael; Capaz, Rodrigo B.; Cremona, Marco; Achete, Carlos A.

2013-03-01

We calculate molecular hyperfine fields in organic magnetoresistance (OMAR) devices using ab initio calculations. To do so, we establish a protocol for the accurate determination of the average hyperfine field Bhf and apply it to selected molecular ions: NPB, TPD, and Alq3. Then, we make devices with precisely the same molecules and perform measurements of the OMAR effect, in order to address the role of hole-transport layer in the characteristic magnetic field B0 of OMAR. Contrary to common belief, we find that molecular hyperfine fields are not only caused by hydrogen nuclei. We also find that dipolar contributions to the hyperfine fields can be comparable to the Fermi contact contributions. However, such contributions are restricted to nuclei located in the same molecular ion as the charge carrier (intramolecular), as extramolecular contributions are negligible.

The nuclear magnetic moment of 208Bi and its relevance for a test of bound-state strong-field QED

NASA Astrophysics Data System (ADS)

Schmidt, S.; Billowes, J.; Bissell, M. L.; Blaum, K.; Garcia Ruiz, R. F.; Heylen, H.; Malbrunot-Ettenauer, S.; Neyens, G.; Nörtershäuser, W.; Plunien, G.; Sailer, S.; Shabaev, V. M.; Skripnikov, L. V.; Tupitsyn, I. I.; Volotka, A. V.; Yang, X. F.

2018-04-01

The hyperfine structure splitting in the 6p3 3/2 4S → 6p2 7 s 1/2 4P transition at 307 nm in atomic 208Bi was measured with collinear laser spectroscopy at ISOLDE, CERN. The hyperfine A and B factors of both states were determined with an order of magnitude improved accuracy. Based on these measurements, theoretical input for the hyperfine structure anomaly, and results from hyperfine measurements on hydrogen-like and lithium-like 209Bi80+,82+, the nuclear magnetic moment of 208Bi has been determined to μ (208Bi) = + 4.570 (10)μN. Using this value, the transition energy of the ground-state hyperfine splitting in hydrogen-like and lithium-like 208Bi80+,82+ and their specific difference of -67.491(5)(148) meV are predicted. This provides a means for an experimental confirmation of the cancellation of nuclear structure effects in the specific difference in order to exclude such contributions as the cause of the hyperfine puzzle, the recently reported 7-σ discrepancy between experiment and bound-state strong-field QED calculations of the specific difference in the hyperfine structure splitting of 209Bi80+,82+.

Hyperfine structure parametrisation in Maple

NASA Astrophysics Data System (ADS)

Gaigalas, G.; Scharf, O.; Fritzsche, S.

2006-02-01

In hyperfine structure examinations, routine high resolution spectroscopy methods have to be combined with exact fine structure calculations. The so-called magnetic A and electric B factor of the fine structure levels allow to check for a correct fine structure analysis, to find errors in the level designation, to find new levels and to probe the electron wavefunctions and its mixing coefficients. This is done by parametrisation of these factors into different contributions of the subshell electrons, which are split further into their radial and spin-angular part. Due to the routine with which hyperfine structure measurements are done, a tool for keeping the necessary information together, performing checks online with the experiment and deriving standard quantities is of great help. MAPLE [Maple is a registered trademark of Waterloo Maple Inc.] is a highly-developed symbolic programming language, often referred to as the pocket calculator of the future. Packages for theoretical atomic calculation exist ( RACAH and JUCYS) and the language meets all the requirements to keep and present information accessible for the user in a fast and practical way. We slightly extended the RACAH package [S. Fritzsche, Comput. Phys. Comm. 103 (1997) 51] and set up an environment for experimental hyperfine structure calculations, the HFS package. Supplying the fine structure and nuclear data, one is in the position to obtain information about the hyperfine spectrum, the different contributions to the splitting and to perform a least square fit of the radial parameters based on the semiempirical method. Experimentalist as well as theoretical physicist can do a complete hyperfine structure analysis using MAPLE. Program summaryTitle of program: H FS Catalogue number: ADXD Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADXD Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions: none Computers for which the program is designed: All computers with a license of the computer algebra package MAPLE Installations: University of Kassel (Germany) Operating systems under which the program has been tested: Linux 9.0 Program language used:MAPLE, Release 7, 8 and 9 Memory required to execute with typical data: 5 MB No. of lines in distributed program, including test data, etc.: 34 300 No. of bytes in distributed program, including test data, etc.: 954 196 Distribution format: tar.gz Nature of the physical problem: Atomic state functions of an many configuration many electron atom with several open shells are defined by a number of quantum numbers, by their coupling and selection rules such as the Pauli exclusion principal or parity conservation. The matrix elements of any one-particle operator acting on these wavefunctions can be analytically integrated up to the radial part [G. Gaigalas, O. Scharf, S. Fritzsche, Central European J. Phys. 2 (2004) 720]. The decoupling of the interacting electrons is general, the obtained submatrix element holds all the peculiarities of the operator in question. These so-called submatrix elements are the key to do hyperfine structure calculations. The interaction between the electrons and the atomic nucleus leads to an additional splitting of the fine structure lines, the hyperfine structure. The leading components are the magnetic dipole interaction defining the so-called A factor and the electric quadrupole interaction, defining the so-called B factor. They express the energetic splitting of the spectral lines. Moreover, they are obtained directly by experiments and can be calculated theoretically in an ab initio approach. A semiempirical approach allows the fitting of the radial parts of the wavefunction to the experimentally obtained A and B factors. Method of solution: Extending the existing csf_LS() and asf_LS() to several open shells and implementing a data structure level_LS() for the fine structure level, the atomic environment is defined in MAPLE. It is used in a general approach to decouple the interacting shells for any one-particle operator. Further submatrix elements for the magnetic dipole and electric quadrupole interaction are implemented, allowing to calculate the A and B factors up to the radial part. Several procedures for standard quantities of the hyperfine structure are defined, too. The calculations are accelerated by using a hyper-geometric approach for three, six and nine symbols. Restrictions onto the complexity of the problem: Only atomic state functions in nonrelativistic LS-coupling with states having l⩽3 are supported. Typical running time: The program replies promptly on most requests. The least square fit depends heavily on the number of levels and can take a few minutes.

HYPERFINE-DEPENDENT gf-VALUES OF Mn I LINES IN THE 1.49-1.80 μm H BAND

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andersson, M.; Hutton, R.; Zou, Y.

2015-01-01

The three Mn I lines at 17325, 17339, and 17349 Å are among the 25 strongest lines (log (gf) > 0.5) in the H band. They are all heavily broadened due to hyperfine structure, and the profiles of these lines have so far not been understood. Earlier studies of these lines even suggested that they were blended. In this work, the profiles of these three infrared (IR) lines have been studied theoretically and compared to experimental spectra to assist in the complete understanding of the solar spectrum in the IR. It is shown that the structure of these lines cannot be describedmore » in the conventional way using the diagonal A and B hyperfine interaction constants. The off-diagonal hyperfine interaction not only has a large impact on the energies of the hyperfine levels, but also introduces a large intensity redistribution among the hyperfine lines, changing the line profiles dramatically. By performing large-scale calculations of the diagonal and off-diagonal hyperfine interaction and the gf-values between the upper and lower hyperfine levels and using a semi-empirical fitting procedure, we achieved agreement between our synthetic and experimental spectra. Furthermore, we compare our results with observations of stellar spectra. The spectra of the Sun and the K1.5 III red giant star Arcturus were modeled in the relevant region, 1.73-1.74 μm, using our theoretically predicted gf-values and energies for each individual hyperfine line. Satisfactory fits were obtained and clear improvements were found using our new data compared with the old available Mn I data. A complete list of energies and gf-values for all the 3d {sup 5}4s({sup 7} S)4d e{sup 6}D - 3d {sup 5}4s({sup 7} S)4f w{sup 6}F hyperfine lines are available as supporting material, whereas only the stronger lines are presented and discussed in detail in this paper.« less

Moessbauer studies in zinc-manganese ferrites for use in measuring small velocities and accelerations with great precision

NASA Technical Reports Server (NTRS)

Escue, W. T.; Gupta, R. G.; Mendiratta, R. G.

1975-01-01

Mossbauer spectroscopy was used for a systematic study of the magnetic behavior of manganese and zinc in mixed ferrites. It was observed that Zn2+ has preference to substitute Mn2+ at interstitial sites where the metal ions are tetrahedrally coordinated with four oxygen neighbors. The internal magnetic hyperfine field at the tetrahedral iron site is larger than that at the octahedral site. The relaxation effects were observed to play an important role as the zinc contents were increased, while the spin-correlation time and the magnetic field were observed to decrease in strength. It is concluded that Mossbauer effect data on complex materials, when used in conjunction with other data, can provide useful insight into the origin of the microscopic properties of magnetic materials.

Charge-induced spin torque in Weyl semimetals

NASA Astrophysics Data System (ADS)

Kurebayashi, Daichi; Nomura, Kentaro

In this work, we present phenomenological and microscopic derivations of spin torques in magnetically doped Weyl semimetals. As a result, we obtain the analytical expression of the spin torque generated, without a flowing current, when the chemical potential is modulated. We also find that this spin torque is a direct consequence of the chiral anomaly. Therefore, observing this spin torque in magnetic Weyl semimetals might be an experimental evidence of the chiral anomaly. This spin torque has also a great advantage in application. In contrast to conventional current-induced spin torques such as the spin-transfer torques, this spin torque does not accompany a constant current flow. Thus, devices using this operating principle is free from the Joule heating and possibly have higher efficiency than devices using conventional current-induced spin torques. This work was supported by JSPS KAKENHI Grant Number JP15H05854 and JP26400308.