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1

Robust control of entanglement in a Nitrogen-vacancy centre coupled to a Carbon-13 nuclear spin in diamond  

E-print Network

We address a problem of generating a robust entangling gate between electronic and nuclear spins in the system of a single nitrogen-vacany centre coupled to a nearest Carbon-13 atom in diamond against certain types of systematic errors such as pulse-length and off-resonance errors. We analyse the robustness of various control schemes: sequential pulses, composite pulses and numerically-optimised pulses. We find that numerically-optimised pulses, produced by the gradient ascent pulse engineering algorithm (GRAPE), are more robust than the composite pulses and the sequential pulses. The optimised pulses can also be implemented in a faster time than the composite pulses.

Said, R S

2009-01-01

2

Robust control of entanglement in a Nitrogen-vacancy centre coupled to a Carbon-13 nuclear spin in diamond  

E-print Network

We address a problem of generating a robust entangling gate between electronic and nuclear spins in the system of a single nitrogen-vacany centre coupled to a nearest Carbon-13 atom in diamond against certain types of systematic errors such as pulse-length and off-resonance errors. We analyse the robustness of various control schemes: sequential pulses, composite pulses and numerically-optimised pulses. We find that numerically-optimised pulses, produced by the gradient ascent pulse engineering algorithm (GRAPE), are more robust than the composite pulses and the sequential pulses. The optimised pulses can also be implemented in a faster time than the composite pulses.

R. S. Said; J. Twamley

2009-03-23

3

Carbon-13 cross-polarization magic-angle-spinning nuclear magnetic resonance investigation of the interactions between maleic anhydride grafted polypropylene and wood polymers.  

PubMed

The chemical interactions between maleic anhydride grafted polypropylene (MAPP) and wood were studied with solid-state carbon-13 cross-polarization magic-angle-spinning nuclear magnetic resonance ((13)C CPMAS NMR) spectroscopy. MAPP was synthesized with 100% (13)C enrichment at the C(1) and C(4) carbons to allow detection of the [1,4-(13)C(2)]MAPP functional groups and was melt blended with cellulose, lignin, and maple wood. In the cellulose/MAPP blend, changes in (13)C CPMAS NMR corrected signal intensities for the anhydride and dicarboxylic maleic acid functionalities suggested that esterification may have occurred predominantly from the more numerous diacid carbons. A single proton longitudinal relaxation in the rotating frame, (H)T(1rho), for the MAPP and the cellulose carbons in the blend suggested that they were spin coupled, i.e., homogeneous on a 10-200 Angstrom scale. Esterification was also suggested in the lignin/MAPP blend. Furthermore, the more significant changes in the intensities of the carbonyl signals and (H)T(1rho) values suggested that lignin may be more reactive to MAPP than cellulose. Finally, when maple was melt blended with MAPP, the same trends in the (13)C CP-MAS NMR spectra and (H)T(1rho) behavior were observed as when MAPP was blended with cellulose or lignin. This study therefore clarifies that during melt compounding of wood with MAPP, esterification occurs with wood polymers, preferentially with lignin. Understanding the interactions of MAPP with wood is of significance for the development of natural-fiber-reinforced thermoplastic composites. PMID:18498698

Rude, Erica; Laborie, Marie-Pierre G

2008-05-01

4

CARBON-13 Nuclear Magnetic Resonance in Solids.  

NASA Astrophysics Data System (ADS)

The rotational resonance phenomena induced by the modulation of the interactions in magnetic angle spinning (MAS) nuclear magnetic resonance (NMR) experiments have been demonstrated for the first time. In the study of chemical shielding, the rotational resonance occurs when a spin-lock field with an amplitude of nomega _{rm r} (n = 1,2) is applied where omega_{rm r} is the spinning speed. The magnetization, which nutates in the rotating frame at a frequency related to the chemical shift anisotropy (CSA), allows for the retrieval of the CSA from MAS NMR spectra at a high spinning speed. In addition, a similar rotational resonance phenomenon was studied in a homonuclear spin coupled system. The resonance occurs when the separation of the isotropic chemical shifts of the two spins equal omega_{ rm r}. The rotational resonance restores a splitting pattern in the MAS spectra and enhances the flip-flop motion of the two spins. Also, the sample spinning NMR of homonuclear coupled systems has been analyzed by a pseudo-spin model. In the case of the ^ {13}C dilabelled phthalic anhydride, the analyses at different spinning speeds lead to the determination of the orientation of the chemical shielding tensor. The quadrupolar effect in ^{13 }C-^{14}N coupled spins is manifested in the ^{13 }C MAS spectra by the appearance of an asymmetric doublet. A simple analytical solution to this quadrupolar effect was developed to study ^{13 }C-^{14}N systems for information on both the electric field gradient (EFG) tensor of the nitrogen and the ^{13 }C-^{14}N bond distance. Furthermore, the variable angle sample spinning technique has been applied to determine of the chemical shielding tensors with their orientation for these systems. The molecules studied include tetramethyl-pyrazine, dimethylglyoxime and triethylenediamine. The effect of relaxation in solid state NMR dipolar spectra was studied. The cross relaxation terms introduce a peak in the center of the expected Pake doublet. The dipolar spectra of methyl phosphonic acid at room temperature and methyl fluoride at low temperature (25 K) were used to study this effect.

Gan, Zhehong

5

Characterization of High-Tannin Fractions from Humus by Carbon-13 Cross-Polarization and Magic-Angle Spinning Nuclear Magnetic Resonance  

E-print Network

Characterization of High-Tannin Fractions from Humus by Carbon-13 Cross-Polarization and Magic in Newfoundland with a permanent con- version from forest to heathland (Titus et al., 1995).Condensed tannins can characterized tannin-rich fractions from humus collected in 1998 from et al., 1998). Incubation experiments

Hemminga, Marcus A.

6

The first observation of Carbon-13 spin noise spectra  

PubMed Central

We demonstrate the first 13C NMR spin noise spectra obtained without any pulse excitation by direct detection of the randomly fluctuating noise from samples in a cryogenically cooled probe. Noise power spectra were obtained from 13C enriched methanol and glycerol samples at 176 MHz without and with 1H decoupling, which increases the sensitivity without introducing radio frequency interference with the weak spin noise. The multiplet amplitude ratios in 1H coupled spectra indicate that, although pure spin noise prevails in these spectra, the influence of absorbed circuit noise is still significant at the high concentrations used. In accordance with the theory heteronuclear Overhauser enhancements are absent from the 1H-decoupled 13C spin noise spectra. PMID:23041799

Schlagnitweit, Judith; Müller, Norbert

2012-01-01

7

Author's personal copy High field dynamic nuclear polarization at 6.7 T: Carbon-13 polarization  

E-print Network

Author's personal copy High field dynamic nuclear polarization at 6.7 T: Carbon-13 polarization s t r a c t In most applications of dissolution-DNP, the polarization of nuclei with low gyromagnetic lines such as Trityl at low temperatures T = 1.2 K in polarizing fields B0 6 5 T. In a field B0 = 6

8

Carbon-13 nuclear magnetic resonance studies of glycolysis in protozoa  

E-print Network

from substrate glucose was found to be incorporated without scrambling irto mannitol. Incu- bations with singly labeled glucoses confirmed this information. Path- ways of mannitol biosynthesis im Euglena gracilis z were found to in- volve a NADPH... OF CONTENTS ABSTRACT ACKNOWLEDGMENTS. TABLE OF CONTENTS. LIST OF TABLES LIST OF FIGURES. CHAPTER I. INTRODUCTION Nuclear Magnetic Resonance Spectroscopy. lh h t hit d E th E ~Et E itits CHAPTER II. EXPERIMENTAL. Growth and Harvest of Euglena gracilis...

Rhoades, Teresa Ann

1986-01-01

9

Solid-Sample Carbon13 Nuclear Magnetic Resonance Spectroscopy of Lignin and Hydroxymethylated Lignin  

Microsoft Academic Search

Solid-sample carbon-13 NMR spectroscopy with cross polarization and magic angle spinning (CP\\/MAS) was employed to study the hydroxymethylation of lignin. Kraft pine and steam-exploded hardwood lignins were reacted with formaldehyde and the resultant structural changes in the lignins evaluated by comparing the spectra of the treated and untreated lignins. The results indicated that hydroxymethylation had occurred at the 5 position

Douglas J. Gardner; Gary D. McGinnis; Larry W. Amos

1989-01-01

10

Nuclear spin circular dichroism  

SciTech Connect

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.

Vaara, Juha, E-mail: juha.vaara@iki.fi [NMR Research Group, Department of Physics, University of Oulu, P.O. Box 3000, FIN-90014 Oulu (Finland)] [NMR Research Group, Department of Physics, University of Oulu, P.O. Box 3000, FIN-90014 Oulu (Finland); Rizzo, Antonio [Istituto per i Processi Chimico-Fisici del Consiglio Nazionale delle Ricerche (IPCF-CNR), Area della Ricerca, via G. Moruzzi 1, I-56124 Pisa (Italy)] [Istituto per i Processi Chimico-Fisici del Consiglio Nazionale delle Ricerche (IPCF-CNR), Area della Ricerca, via G. Moruzzi 1, I-56124 Pisa (Italy); Kauczor, Joanna; Norman, Patrick [Department of Physics, Chemistry and Biology, Linköping University, S-58183 Linköping (Sweden)] [Department of Physics, Chemistry and Biology, Linköping University, S-58183 Linköping (Sweden); Coriani, Sonia, E-mail: coriani@units.it [Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, Via L. Giorgieri 1, I-34127 Trieste (Italy)] [Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, Via L. Giorgieri 1, I-34127 Trieste (Italy)

2014-04-07

11

SUBSTITUENT EFFECTS AND ADDITIVITY IN THE CARBON-13 NUCLEAR MAGNETIC RESONANCE SPECTRA OF CHLORINATED NAPHTHALENES AND THEIR CHLORINATED NAPHTHOL METABOLITES  

EPA Science Inventory

Carbon-13 and proton nuclear magnetic resonance spectra were obtained for 12 chlorinated naphthalenes and six chlorinated naphthols, some of which are metabolites of the naphthalenes. The validity of the use of additivity of chlorine and hydroxyl substituent effects to predict 13...

12

Carbon-13 nuclear magnetic resonance spectra of vitamins D and related compounds.  

PubMed

1. The natural abundance carbon-13 nmr of vitamins D (D2 and D3) and several isomers (5, 6-trans-vitamin D2, isotachysterol2 and isovitamin D2) have been completely assigned by employing off-resonance noise-decoupling, acetylation shifts, and lanthanide-induced shifts experiments. The last two techniques were especially useful for the present study. 2. Carbon-13 nmr spectral characteristics of the three main conjugated triene moieties (SE-Z-SZ, SE-E-SZ, or SE-E-SE), involved in the molecules of vitamin D and its isomers, were revealed. Thus, the striking dependence of the shieldings on molecular geometries and high sensitivity of the resonances to the environments of conjugated systems were surveyed. 3. Conformational preferences in solutions of the hydroxyl groups in vitamins D2 and D3 as well as 5, 6-trans-vitamin D2 were conveniently determined. PMID:178846

Tsukida, K; Akutsu, K; Saiki, K

1975-01-01

13

Sensing remote nuclear spins  

E-print Network

Sensing single nuclear spins is a central challenge in magnetic resonance based imaging techniques. Although different methods and especially diamond defect based sensing and imaging techniques in principle have shown sufficient sensitivity, signals from single nuclear spins are usually too weak to be distinguished from background noise. Here, we present the detection and identification of remote single C-13 nuclear spins embedded in nuclear spin baths surrounding a single electron spins of a nitrogen-vacancy centre in diamond. With dynamical decoupling control of the centre electron spin, the weak magnetic field ~10 nT from a single nuclear spin located ~3 nm from the centre with hyperfine coupling as weak as ~500 Hz is amplified and detected. The quantum nature of the coupling is confirmed and precise position and the vector components of the nuclear field are determined. Given the distance over which nuclear magnetic fields can be detected the technique marks a firm step towards imaging, detecting and cont...

Zhao, Nan; Schmid, Berhard; Isoya, Junichi; Markham, Mathew; Twitchen, Daniel; Jelezko, Fedor; Liu, Ren-Bao; Fedder, Helmut; Wrachtrup, Jörg

2012-01-01

14

Sensing remote nuclear spins  

E-print Network

Sensing single nuclear spins is a central challenge in magnetic resonance based imaging techniques. Although different methods and especially diamond defect based sensing and imaging techniques in principle have shown sufficient sensitivity, signals from single nuclear spins are usually too weak to be distinguished from background noise. Here, we present the detection and identification of remote single C-13 nuclear spins embedded in nuclear spin baths surrounding a single electron spins of a nitrogen-vacancy centre in diamond. With dynamical decoupling control of the centre electron spin, the weak magnetic field ~10 nT from a single nuclear spin located ~3 nm from the centre with hyperfine coupling as weak as ~500 Hz is amplified and detected. The quantum nature of the coupling is confirmed and precise position and the vector components of the nuclear field are determined. Given the distance over which nuclear magnetic fields can be detected the technique marks a firm step towards imaging, detecting and controlling nuclear spin species external to the diamond sensor.

Nan Zhao; Jan Honert; Berhard Schmid; Junichi Isoya; Mathew Markham; Daniel Twitchen; Fedor Jelezko; Ren-Bao Liu; Helmut Fedder; Jörg Wrachtrup

2012-04-29

15

Dynamic Nuclear Polarization CARBON-13 NMR of Diamond Films and Rotating Gradient Mas-Nmr Imaging  

NASA Astrophysics Data System (ADS)

^{13}C NMR, with and without dynamic nuclear polarization and ESR measurements are presented on three chemical vapor deposited diamond films. By microwave irradiation with a frequency close to the Larmor frequency of the unpaired electrons present in the diamond films, the ^{13} C signal is enhanced resulting in ^ {13}C direct and cross polarization spectra that are almost impossible to measure without DNP. The resolution of NMR imaging of solids is hampered by the large NMR linewidths of static solid samples. MAS NMR imaging measurements are presented where MAS removes the linebroadening, while the gradient rotates synchronously with the spinner.

Lock, Herman

16

Determination of alkylbenzenesulfonate surfactants in groundwater using macroreticular resins and carbon-13 nuclear magnetic resonance spectrometry  

USGS Publications Warehouse

Alkylbenzenesulfonate surfactants were determined in groundwater at concentrations as low as 0.3 mg/L. The method uses XAD-8 resin for concentration, followed by elution with methanol, separation of anionic and nonionic surfactants by anion exchange, quantitation by titration, and identification by 13C nuclear magnetic resonance spectrometry. Laboratory standards and field samples containing straight-chain and branched-chain alkylbenzenesulfonates, sodium dodecyl sulfate, and alkylbenzene ethoxylates were studied. The XAD-8 extraction of surfactants from groundwater was completed in the field, which simplified sample preservation and reduced the cost of transporting samples.

Thurman, E.M.; Willoughby, T.; Barber, L.B., Jr.; Thorn, K.A.

1987-01-01

17

CARBON-13 Nuclear Magnetic Resonance Experiments in Powdered and Oriented Materials  

NASA Astrophysics Data System (ADS)

Sample reorientation during the mixing time of a two-dimensional ^{13}C Nuclear Magnetic Resonance (NMR) exchange experiment allows the measurement of the principal values of chemical shift tensors in powdered samples whose one-dimensional powder patterns are too complex to reliably analyze. The experiment is relatively easy to perform, and the experimental artifacts can be accounted for with a straightforward physical model. The process of fitting the powdered sample spectra produces the principal values of the chemical shift tensor, and a function that describes the experimental artifacts in the spectrum. The method is useful for sorting out the principal values of overlapping chemical shift tensor powder patterns, and it also shows promise for characterizing heterogeneous materials. The experiment is useful for characterizing order in partially oriented samples. The orientational distribution of molecular fragments in extruded and drawn polymer samples have been measured. The distribution functions are quite similar to the predictions of a normal probability distribution on a sphere. The function that describes the experimental artifacts in the powder spectrum can be used to correct the analysis of the oriented sample's spectrum, thereby increasing the accuracy of orientational distribution measurements. In certain cases, the local conformation of a macromolecule can be determined from the spectrum of a very highly oriented sample.

Hughes, Craig Dale

18

Isomer Identification of Monohydroxylated Polycyclic Aromatic Hydrocarbon Metabolites by Gas Chromatography\\/Fourier Transform Infrared Spectroscopy and Carbon13 Nuclear Magnetic Resonance Spectroscopy  

Microsoft Academic Search

The foundation for a systematic approach utilizing spectral\\/structural correlations was established for unambiguous identification of monohydroxylated polyaromatic hydrocarbon metabolite (PAHm) isomers. Using elements of a theoretical\\/empirical valence-bond model developed earlier in our laboratory for isomer identification of chlorinated dibenzo- p -dioxin isomers, both gas chromatography\\/Fourier transform infrared spectroscopy (GC\\/FTIR) and carbon-13 nuclear magnetic resonance ( 13 C NMR) spectroscopy were

James Grainger; Zheng Li; Charisse Walcott; Christopher J. Smith; Donald G. Patterson Jr.; Bretta King; Cornelia Gillyard

2002-01-01

19

CP\\/MAS Carbon13 NMR Study of Spin Relaxation Phenomena of Cellulose Containing Crystalline and Noncrystalline Components  

Microsoft Academic Search

Cross-polarization, C rotating frame spin-lattice relaxation and C laboratory frame spin-lattice relaxation processes have been studied for different cellulose samples by CP\\/MAS C NMR spectroscopy. It was found that the CP process can be described by a simple thermodynamic model and relative intensities of the respective resonance lines are consistent with the atomic ratios for the spectra obtained at a

F. Horii; A. Hirai; R. Kitamaru

1984-01-01

20

Nuclear Spins in Quantum Dots  

Microsoft Academic Search

The main theme of this thesis is the hyperfine interaction between the many lattice nuclear spins and electron spins localized in GaAs quantum dots. This interaction is an intrinsic property of the material. Despite the fact that this interaction is rather weak, it can, as shown in this thesis, strongly influence the dynamics of electron spins in quantum dots. In

S. I. Erlingsson

2003-01-01

21

NUCLEAR SPIN RESONANCE  

Microsoft Academic Search

I. Introduction 566 II. NSR energy levels and frequencies 568 1. Energy levels for resonating nuclei with spins 1 or 3\\/2 568 2. NSR energy levels for spin 5\\/2 571 III. Relative intensities of NSR lines 571 1. Relative intensities of Zeeman components in NQR 571 2. Generalized NSR equations 572 3. Relative intensities of NSR lines for spin 1

Vadim S Grechishkin; N. E. Ajnbinder

1964-01-01

22

A Carbon13 Nuclear Magnetic Resonance Spectroscopic Study of Inter-Proton Pair Order Parameters: A New Approach to StudyOrder and Dynamics in Phospholipid Membrane Systems  

Microsoft Academic Search

We report a simple new nuclear magnetic resonance (NMR) spectroscopic method to investigate order and dynamics in phospholipids in which inter-proton pair order parameters are derived by using high resolution 13C cross-polarization\\/magic angle spinning (CP\\/MAS) NMR combined with 1H dipolar echo preparation. The resulting two-dimensional NMR spectra permit determination of the motionally averaged interpair second moment for protons attached to

Julio A. Urbina; Benjamin Moreno; William Arnold; Christopher H. Taron; Peter Orlean; Eric Oldfield

1998-01-01

23

Teleportation in a nuclear spin quantum computer  

Microsoft Academic Search

We present a procedure for quantum teleportation in a nuclear spin quantum computer in which quantum logic gates are implemented by using selective electromagnetic pulses. A sequence of pulses is combined with single-spin measurements in the sigmaz basis for fast transfer of information in a spin quantum computer. We simulated this procedure for quantum teleportation in a nuclear spin chain

Gennady P. Berman; Gustavo V. López; Vladimir I. Tsifrinovich

2002-01-01

24

NUCLEAR SPIN RESONANCE  

Microsoft Academic Search

The first experiments on nuclear quadrupole interactions in crystals ; were carried out by R. V. Pound (Phys. Rev., magnetic resonance lines and by H. ; G. Dehmelt and H. Kruger (Naturwiss., 37: 111(1950)) who observed the absorption ; of radiowaves in a neutral magnetic field. The work was subsequently continued ; in two directions: toward the study of large,

V. S. Grechishkin; N. E. Ainbinder

1963-01-01

25

A carbon-13 nuclear magnetic resonance spectroscopic study of inter-proton pair order parameters: a new approach to study order and dynamics in phospholipid membrane systems.  

PubMed Central

We report a simple new nuclear magnetic resonance (NMR) spectroscopic method to investigate order and dynamics in phospholipids in which inter-proton pair order parameters are derived by using high resolution 13C cross-polarization/magic angle spinning (CP/MAS) NMR combined with 1H dipolar echo preparation. The resulting two-dimensional NMR spectra permit determination of the motionally averaged interpair second moment for protons attached to each resolved 13C site, from which the corresponding interpair order parameters can be deducted. A spin-lock mixing pulse before cross-polarization enables the detection of spin diffusion amongst the different regions of the lipid molecules. The method was applied to a variety of model membrane systems, including 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)/sterol and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/sterol model membranes. The results agree well with previous studies using specifically deuterium labeled or predeuterated phospholipid molecules. It was also found that efficient spin diffusion takes place within the phospholipid acyl chains, and between the glycerol backbone and choline headgroup of these molecules. The experiment was also applied to biosynthetically 13C-labeled ergosterol incorporated into phosphatidylcholine bilayers. These results indicate highly restricted motions of both the sterol nucleus and the aliphatic side chain, and efficient spin exchange between these structurally dissimilar regions of the sterol molecule. Finally, studies were carried out in the lamellar liquid crystalline (L alpha) and inverted hexagonal (HII) phases of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE). These results indicated that phosphatidylethanolamine lamellar phases are more ordered than the equivalent phases of phosphatidylcholines. In the HII (inverted hexagonal) phase, despite the increased translational freedom, there is highly constrained packing of the lipid molecules, particularly in the acyl chain region. PMID:9726938

Urbina, J A; Moreno, B; Arnold, W; Taron, C H; Orlean, P; Oldfield, E

1998-01-01

26

Electron Spin Decoherence in Silicon Carbide Nuclear Spin Bath  

E-print Network

In this paper, we study the electron spin decoherence of single defects in silicon carbide (SiC) nuclear spin bath. We find that, although the natural abundance of $^{29}\\rm{Si}$ ($p_{\\rm{Si}}=4.7\\%$) is about 4 times larger than that of $^{13}{\\rm C}$ ($p_{\\rm{C}}=1.1\\%$), the electron spin coherence time of defect centers in SiC nuclear spin bath in strong magnetic field ($B>300~\\rm{Gauss}$) is longer than that of nitrogen-vacancy (NV) centers in $^{13}{\\rm C}$ nuclear spin bath in diamond. The reason for this counter-intuitive result is the suppression of heteronuclear-spin flip-flop process in finite magnetic field. Our results show that electron spin of defect centers in SiC are excellent candidates for solid state spin qubit in quantum information processing.

Li-Ping Yang; Christian Burk; Mattias Widmann; Sang-Yun Lee; Jörg Wrachtrup; Nan Zhao

2014-09-16

27

Dressed qubits in nuclear spin baths  

SciTech Connect

We present a method to encode a dressed qubit into the product state of an electron spin localized in a quantum dot and its surrounding nuclear spins via a dressing transformation. In this scheme, the hyperfine coupling and a portion of a nuclear dipole-dipole interaction become logic gates, while they are the sources of decoherence in electron-spin qubit proposals. We discuss errors and corrections for the dressed qubits. Interestingly, the effective Hamiltonian of nuclear spins is equivalent to a pairing Hamiltonian, which provides the microscopic mechanism to protect dressed qubits against decoherence.

Wu Lianao [Department of Theoretical Physics and History of Science, Basque Country University (EHU/UPV), Post Office Box 644, ES-48080 Bilbao (Spain) and IKERBASQUE, Basque Foundation for Science, ES-48011 Bilbao (Spain)

2010-04-15

28

Measurement of internuclear distances in polycrystalline solids: Rotationally enhanced transfer of nuclear spin magnetization  

SciTech Connect

A magic angle spinning (MAS) NMR technique for measurement of the distance between two homonuclear sites separated by as much as 0.5 nm is demonstrated. This is achieved by proton decoupling during the magnetization exchange process, greatly attenuating the influence of abundant nuclear spins, selective isotopic labeling of both sites of interest, so that the system may be approximated as a set of magnetically dilute coupled spin pairs, and MAS with matching of the rotational resonance condition. Tyrosine ethyl ester (TEE), carbon 13 labeled at both the -CH{sub 2}- of the ester moiety and at the 4{prime}-OH aromatic carbon is used as a demonstration of the technique. Calculated data is compared to experimental data.

Raleigh, D.P.; Creuzet, F.; Das Gupta, S.K.; Levitt, M.H.; Griffin, R.G. (Massachusetts Institute of Technology, Cambridge (USA))

1989-06-07

29

Electron spin decoherence in silicon carbide nuclear spin bath  

NASA Astrophysics Data System (ADS)

In this Rapid Communication, we study the electron spin decoherence of single defects in silicon carbide (SiC) nuclear spin bath. We find that, although the natural abundance of 29Si (pSi=4.7 % ) is about four times larger than that of 13C (pC=1.1 % ), the electron spin coherence time of defect centers in SiC nuclear spin bath in a strong magnetic field (B >300 G ) is longer than that of nitrogen-vacancy (NV) centers in 13C nuclear spin bath in diamond. In addition to the smaller gyromagnetic ratio of 29Si, and the larger bond length in SiC lattice, a crucial reason for this counterintuitive result is the suppression of the heteronuclear-spin flip-flop process in a finite magnetic field. Our results show that electron spin of defect centers in SiC are excellent candidates for solid state spin qubit in quantum information processing.

Yang, Li-Ping; Burk, Christian; Widmann, Matthias; Lee, Sang-Yun; Wrachtrup, Jörg; Zhao, Nan

2014-12-01

30

The NV center as a quantum actuator: time-optimal control of nuclear spins  

E-print Network

Indirect control of qubits by a quantum actuator has been proposed as an appealing strategy to manipulate qubits that couple only weakly to external fields. While universal quantum control can be easily achieved when the actuator-qubit coupling is anisotropic, the efficiency of this approach is less clear. Here we analyze the time-efficiency of the quantum actuator control. We describe a strategy to find time-optimal control sequence by the quantum actuator and compare their gate times with direct driving, identifying regimes where the actuator control performs faster. As an example, we focus on a specific implementation based on the Nitrogen-Vacancy center electronic spin in diamond (the actuator) and nearby carbon-13 nuclear spins (the qubits).

Clarice D. Aiello; Paola Cappellaro

2014-10-21

31

Nuclear spin conversion in diatomic molecules  

SciTech Connect

A mechanism of the internal interaction in dimers that mixes different nuclear spin modifications has been proposed. It has been shown that the intramolecular current associated with transitions between electronic terms of different parities can generate different magnetic fields on nuclei, leading to transitions between spin modifications and to the corresponding changes in rotational states. In the framework of the known quantum relaxation process, this interaction initiates irreversible conversion of nuclear spin modifications. The estimated conversion rate for nitrogen at atmospheric pressure is quite high (10{sup -3}-10{sup -5} s{sup -1})

Il'ichev, L. V., E-mail: leonid@iae.nsk.su; Shalagin, A. M. [Russian Academy of Sciences, Institute of Automation and Electrometry, Siberian Branch (Russian Federation)] [Russian Academy of Sciences, Institute of Automation and Electrometry, Siberian Branch (Russian Federation)

2013-07-15

32

Optical Orientation of Nuclear Spins  

E-print Network

Stray Field Images of nuclear polarization for 69 Ga as aStray Field Images of nuclear polarization for (a) 71 Gaimages for 69 Ga capture the changing shape of the distribution of nuclear polarization

King, Jonathan Patrick

2012-01-01

33

The spin-temperature theory of dynamic nuclear polarization and nuclear spin-lattice relaxation  

NASA Technical Reports Server (NTRS)

A detailed derivation of the equations governing dynamic nuclear polarization (DNP) and nuclear spin lattice relaxation by use of the spin temperature theory has been carried to second order in a perturbation expansion of the density matrix. Nuclear spin diffusion in the rapid diffusion limit and the effects of the coupling of the electron dipole-dipole reservoir (EDDR) with the nuclear spins are incorporated. The complete expression for the dynamic nuclear polarization has been derived and then examined in detail for the limit of well resolved solid effect transitions. Exactly at the solid effect transition peaks, the conventional solid-effect DNP results are obtained, but with EDDR effects on the nuclear relaxation and DNP leakage factor included. Explicit EDDR contributions to DNP are discussed, and a new DNP effect is predicted.

Byvik, C. E.; Wollan, D. S.

1974-01-01

34

EFFECTS OF NUCLEAR SPIN POLARIZATION ON REACTION DYNAMICS IN PHOTOSYNTHETIC  

E-print Network

- cally induced dynamic nuclear polarization [CIDNP]) (Kaptein and Oosterhoff, 1969; Closs, 1969EFFECTS OF NUCLEAR SPIN POLARIZATION ON REACTION DYNAMICS IN PHOTOSYNTHETIC BACTERIAL REACTION-equilibrium distributions of nuclear spin states (nuclear spin polarization). This polarization will persist until the 3PI

Boxer, Steven G.

35

Decoherence and dynamical decoupling control of nitrogen-vacancy center electron spins in nuclear spin baths  

E-print Network

We theoretically study the decoherence and the dynamical decoupling control of nitrogen-vacancy center electron spins in high-purity diamond, where the hyperfine interaction with $^{13}$C nuclear spins is the dominating decoherence mechanism. The decoherence is formulated as the entanglement between the electron spin and the nuclear spins, which is induced by nuclear spin bath evolution conditioned on the electron spin state. The nuclear spin bath evolution is driven by elementary processes such as single spin precession and pairwise flip-flops. The importance of different elementary processes in the decoherence depends on the strength of the external magnetic field.

Zhao, Nan; Liu, Ren-Bao

2011-01-01

36

Decoherence and dynamical decoupling control of nitrogen-vacancy center electron spins in nuclear spin baths  

E-print Network

We theoretically study the decoherence and the dynamical decoupling control of nitrogen-vacancy center electron spins in high-purity diamond, where the hyperfine interaction with $^{13}$C nuclear spins is the dominating decoherence mechanism. The decoherence is formulated as the entanglement between the electron spin and the nuclear spins, which is induced by nuclear spin bath evolution conditioned on the electron spin state. The nuclear spin bath evolution is driven by elementary processes such as single spin precession and pairwise flip-flops. The importance of different elementary processes in the decoherence depends on the strength of the external magnetic field.

Nan Zhao; Sai-Wah Ho; Ren-Bao Liu

2011-08-11

37

Nuclear spin relaxation in polarized solid xenon  

SciTech Connect

This thesis reports the results of a 3 year study of nuclear spin relaxation in solid [sup 129]Xe using highly polarized nuclei. The spin-1/2 nuclei of gaseous [sup 129]Xe atoms were polarized by spin-exchange with polarized Rb vapor, which was produced by continuous optical pumping of its principal resonance with a circularly polarized Ti:Sapphire laser. The Xe atoms were then frozen within the glass vapor cell by immersing it in liquid nitrogen. Relaxation of the nuclear polarization in the solid was observed by detecting the [sup 129]Xe nuclear magnetic resonance signal repeatedly over a period of time. The characteristic [sup 129]Xe relaxation time has been studied as a function of temperature from 4.2 K to near its boiling point at 161 K, and also as a function of applied magnetic field from near zero to about 2 kGauss. Measured relaxation times ranged from seconds to weeks; the longest time measured was 500 hours. From the results of this research, several different relaxation mechanisms for [sup 129]Xe have been identified. One is produced by internuclear magnetic dipole interactions which are modulated as a result of atomic self-diffusion within the high temperature Xe crystal. Another results from a nuclear spin-rotation interaction which produces a coupling between the nuclear spin-rotation and the thermal vibrations, or phonons, present in the crystal at all temperatures. At 4.2 K, [sup 129]Xe relaxes through a cross relaxation process with [sup 131]Xe, the spin-3/2 isotope of Xe. The relaxation time of [sup 131]Xe has been measured to be only minutes at 4.2 K because of its strong quadrupole coupling to electric field gradients in the crystal. Cross relaxation, which is simply spin-exchange between the two isotopes, therefore results in an effective relaxation mechanism for [sup 129]Xe. Cross relaxation has also been used to generate substantial [sup 131]Xe nuclear spin polarization.

Gatzke, M.A.

1992-01-01

38

Nuclear spin symmetry state relaxation in formaldehyde  

NASA Astrophysics Data System (ADS)

New measurements of the rate constant of the ortho- para conversion in monomeric gaseous formaldehyde (H 2CO) are presented. Separation of the nuclear spin isomers of formaldehyde was obtained by selective UV laser photolysis of ortho-formaldehyde in the natural ortho- para mixture. A first group of experiments is devoted to the question of surface relaxation. Measurements in low pressure formaldehyde gas show fast relaxation at very low pressures, falling to a minimum at pressures of about 1 mbar and then rising linearly with pressure. The fast relaxation at very low pressures is interpreted as surface relaxation and this interpretation is confirmed by the fact that different wall materials of the fluorescence cells yield different relaxation constants. A second group of experiments extended the pressure range of the nuclear spin symmetry state relaxation measurements in formaldehyde by adding H 2 or SF 6 to it up to pressures of 1 bar. The experimental data follow qualitatively the behaviour that is predicted by theory [R.F. Curl Jr, J.V.V. Kasper, K.S. Pitzer, J. Chem. Phys. 46 (1967) 3220]. Quantitative agreement with theory could be reached by taking calculated values of the spin-rotation coupling constants [P.L. Chapovsky, J. Mol. Struct. 599 (2001) 337] about 35% higher and using surprisingly large nuclear spin symmetry state relaxation cross-sections.

Bechtel, Christian; Elias, Elias; Schramm, Bernhard F.

2005-05-01

39

Nuclear spin relaxation in Rashba nanowires  

NASA Astrophysics Data System (ADS)

We study the nuclear spin relaxation in a ballistic nanowire with hyperfine and Rashba spin-orbit interactions (SOI) and in the presence of magnetic field and electron interactions. The relaxation rate shows pronounced peaks as a function of magnetic field and chemical potential due to van Hove singularities in the Rashba bands. As a result, the regimes of weak and strong SOIs can be distinguished by the number of peaks in the rate. The relaxation rate increases with increasing magnetic field if both Rashba subbands are occupied, whereas it decreases if only the lowest one is occupied.

Zyuzin, Alexander A.; Meng, Tobias; Kornich, Viktoriia; Loss, Daniel

2014-11-01

40

Electrically driven nuclear spin resonance in single-molecule magnets.  

PubMed

Recent advances in addressing isolated nuclear spins have opened up a path toward using nuclear-spin-based quantum bits. Local magnetic fields are normally used to coherently manipulate the state of the nuclear spin; however, electrical manipulation would allow for fast switching and spatially confined spin control. Here, we propose and demonstrate coherent single nuclear spin manipulation using electric fields only. Because there is no direct coupling between the spin and the electric field, we make use of the hyperfine Stark effect as a magnetic field transducer at the atomic level. This quantum-mechanical process is present in all nuclear spin systems, such as phosphorus or bismuth atoms in silicon, and offers a general route toward the electrical control of nuclear-spin-based devices. PMID:24904159

Thiele, Stefan; Balestro, Franck; Ballou, Rafik; Klyatskaya, Svetlana; Ruben, Mario; Wernsdorfer, Wolfgang

2014-06-01

41

NUCLEAR SPIN ISOSPIN RESPONSES FOR LOW-ENERGY NEUTRINOS  

E-print Network

NUCLEAR SPIN ISOSPIN RESPONSES FOR LOW-ENERGY NEUTRINOS Hiroyasu EJIRI Nuclear Physics Laboratory@rcnp.osaka-u.ac.jp (H. Ejiri). Physics Reports 338 (2000) 265}351 Nuclear spin isospin responses for low-energy Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka, 567 Japan. E-mail address: ejiri

Washington at Seattle, University of

42

Nuclear spin symmetry state relaxation in formaldehyde  

Microsoft Academic Search

New measurements of the rate constant of the ortho–para conversion in monomeric gaseous formaldehyde (H2CO) are presented. Separation of the nuclear spin isomers of formaldehyde was obtained by selective UV laser photolysis of ortho-formaldehyde in the natural ortho–para mixture. A first group of experiments is devoted to the question of surface relaxation. Measurements in low pressure formaldehyde gas show fast

Christian Bechtel; Elias Elias; Bernhard F. Schramm

2005-01-01

43

Electronic transport through nuclear-spin-polarization-induced quantum wire  

E-print Network

Electron transport in a new low-dimensional structure - the nuclear spin polarization induced quantum wire (NSPI QW) is theoretically studied. In the proposed system the local nuclear spin polarization creates the effective hyperfine field which confines the electrons with the spins opposite to the hyperfine field to the regions of maximal nuclear spin polarization. The influence of the nuclear spin relaxation and diffusion on the electron energy spectrum and on the conductance of the quantum wire is calculated and the experimental feasibility is discussed.

Yu. V. Pershin; S. N. Shevchenko; I. D. Vagner; P. Wyder

2001-09-25

44

Nuclear Spins as Quantum Memory in Semiconductor Nanostructures  

E-print Network

We theoretically consider solid state nuclear spins in a semiconductor nanostructure environment as long-lived, high-fidelity quantum memory. In particular, we calculate, in the limit of a strong applied magnetic field, the fidelity versus time of P donor nuclear spins in random bath environments of Si and GaAs, and the lifetime of excited intrinsic spins in polarized Si and GaAs environments. In the former situation, the nuclear spin dephases due to spectral diffusion induced by the dipolar interaction among nuclei in the bath. We calculate the decay of nuclear spin quantum memory in the context of Hahn and Carr-Purcell-Meiboom-Gill (CPMG) refocused spin echoes using a formally exact cluster expansion technique which has previously been successful in dealing with electron spin dephasing in a solid state nuclear spin bath. With decoherence dominated by transverse dephasing (T2), we find it feasible to maintain high fidelity (losses of less than 10^{-6}) quantum memory on nuclear spins for times of the order of 100 microseconds (GaAs:P) and 1 to 2 milliseconds (natural Si:P) using CPMG pulse sequences of just a few (~2-4) applied pulses. We also consider the complementary situation of a central flipped intrinsic nuclear spin in a bath of completely polarized nuclear spins where decoherence is caused by the direct flip-flop of the central spin with spins in the bath. Exact numerical calculations that include a sufficiently large neighborhood of surrounding nuclei show lifetimes on the order of 1-5 ms for both GaAs and natural Si. Our calculated nuclear spin coherence times may have significance for solid state quantum computer architectures using localized electron spins in semiconductors where nuclear spins have been proposed for quantum memory storage.

W. M. Witzel; S. Das Sarma

2007-01-19

45

Qubit Protection in Nuclear-Spin Quantum Dot Memories  

E-print Network

We present a mechanism to protect quantum information stored in an ensemble of nuclear spins in a semiconductor quantum dot. When the dot is charged the nuclei interact with the spin of the excess electron through the ...

Taylor, J. M.

46

Coherent control of a single ^{29}si nuclear spin qubit.  

PubMed

Magnetic fluctuations caused by the nuclear spins of a host crystal are often the leading source of decoherence for many types of solid-state spin qubit. In group-IV semiconductor materials, the spin-bearing nuclei are sufficiently rare that it is possible to identify and control individual host nuclear spins. This Letter presents the first experimental detection and manipulation of a single ^{29}Si nuclear spin. The quantum nondemolition single-shot readout of the spin is demonstrated, and a Hahn echo measurement reveals a coherence time of T_{2}=6.3(7)??ms-in excellent agreement with bulk experiments. Atomistic modeling combined with extracted experimental parameters provides possible lattice sites for the ^{29}Si atom under investigation. These results demonstrate that single ^{29}Si nuclear spins could serve as a valuable resource in a silicon spin-based quantum computer. PMID:25541792

Pla, Jarryd J; Mohiyaddin, Fahd A; Tan, Kuan Y; Dehollain, Juan P; Rahman, Rajib; Klimeck, Gerhard; Jamieson, David N; Dzurak, Andrew S; Morello, Andrea

2014-12-12

47

Coherent Control of a Single 29Si Nuclear Spin Qubit  

NASA Astrophysics Data System (ADS)

Magnetic fluctuations caused by the nuclear spins of a host crystal are often the leading source of decoherence for many types of solid-state spin qubit. In group-IV semiconductor materials, the spin-bearing nuclei are sufficiently rare that it is possible to identify and control individual host nuclear spins. This Letter presents the first experimental detection and manipulation of a single 29Si nuclear spin. The quantum nondemolition single-shot readout of the spin is demonstrated, and a Hahn echo measurement reveals a coherence time of T2=6.3 (7 ) ms —in excellent agreement with bulk experiments. Atomistic modeling combined with extracted experimental parameters provides possible lattice sites for the 29Si atom under investigation. These results demonstrate that single 29Si nuclear spins could serve as a valuable resource in a silicon spin-based quantum computer.

Pla, Jarryd J.; Mohiyaddin, Fahd A.; Tan, Kuan Y.; Dehollain, Juan P.; Rahman, Rajib; Klimeck, Gerhard; Jamieson, David N.; Dzurak, Andrew S.; Morello, Andrea

2014-12-01

48

Coherent Control of a Single Silicon-29 Nuclear Spin Qubit  

E-print Network

Magnetic fluctuations caused by the nuclear spins of a host crystal are often the leading source of decoherence for many types of solid-state spin qubit. In group-IV materials, the spin-bearing nuclei are sufficiently rare that it is possible to identify and control individual host nuclear spins. This work presents the first experimental detection and manipulation of a single $^{29}$Si nuclear spin. The quantum non-demolition (QND) single-shot readout of the spin is demonstrated, and a Hahn echo measurement reveals a coherence time of $T_2 = 6.3(7)$ ms - in excellent agreement with bulk experiments. Atomistic modeling combined with extracted experimental parameters provides possible lattice sites for the $^{29}$Si atom under investigation. These results demonstrate that single $^{29}$Si nuclear spins could serve as a valuable resource in a silicon spin-based quantum computer.

Jarryd J. Pla; Fahd A. Mohiyaddin; Kuan Y. Tan; Juan P. Dehollain; Rajib Rahman; Gerhard Klimeck; David N. Jamieson; Andrew S. Dzurak; Andrea Morello

2014-08-06

49

Uncovering many-body correlations in nanoscale nuclear spin baths by central spin decoherence  

PubMed Central

Central spin decoherence caused by nuclear spin baths is often a critical issue in various quantum computing schemes, and it has also been used for sensing single-nuclear spins. Recent theoretical studies suggest that central spin decoherence can act as a probe of many-body physics in spin baths; however, identification and detection of many-body correlations of nuclear spins in nanoscale systems are highly challenging. Here, taking a phosphorus donor electron spin in a 29Si nuclear spin bath as our model system, we discover both theoretically and experimentally that many-body correlations in nanoscale nuclear spin baths produce identifiable signatures in decoherence of the central spin under multiple-pulse dynamical decoupling control. We demonstrate that under control by an odd or even number of pulses, the central spin decoherence is principally caused by second- or fourth-order nuclear spin correlations, respectively. This study marks an important step toward studying many-body physics using spin qubits. PMID:25205440

Ma, Wen-Long; Wolfowicz, Gary; Zhao, Nan; Li, Shu-Shen; Morton, John J.L.; Liu, Ren-Bao

2014-01-01

50

Robust control of individual nuclear spins in diamond  

E-print Network

Isolated nuclear spins offer a promising building block for quantum information processing systems, but their weak interactions often impede preparation, control, and detection. Hyperfine coupling to a proximal electronic spin can enhance each of these processes. Using the electronic spin of the nitrogen-vacancy center as an intermediary, we demonstrate robust initialization, single-qubit manipulation, and direct optical readout of 13C, 15N, and 14N nuclear spins in diamond. These results pave the way for nitrogen nuclear spin based quantum information architectures in diamond.

Benjamin Smeltzer; Jean McIntyre; Lilian Childress

2009-09-22

51

Detection and manipulation of nuclear spin states in fermionic strontium  

SciTech Connect

Fermionic {sup 87}Sr has a nuclear spin of I=9/2, higher than any other element with a similar electronic structure. This large nuclear spin has many applications in quantum simulation and computation, for which preparation and detection of the spin state are requirements. For an ultracold {sup 87}Sr cloud, we show two complementary methods to characterize the spin-state mixture: optical Stern-Gerlach state separation and state-selective absorption imaging. We use these methods to optimize the preparation of a variety of spin-state mixtures by optical pumping and to measure an upper bound of the {sup 87}Sr spin-relaxation rate.

Stellmer, Simon; Grimm, Rudolf [Institut fuer Quantenoptik und Quanteninformation (IQOQI), Oesterreichische Akademie der Wissenschaften, A-6020 Innsbruck (Austria); Institut fuer Experimentalphysik und Zentrum fuer Quantenphysik, Universitaet Innsbruck, A-6020 Innsbruck (Austria); Schreck, Florian [Institut fuer Quantenoptik und Quanteninformation (IQOQI), Oesterreichische Akademie der Wissenschaften, A-6020 Innsbruck (Austria)

2011-10-15

52

Feedback control of nuclear spin bath of a single hole spin in a quantum dot  

NASA Astrophysics Data System (ADS)

For a III-V semiconductor quantum dot charged with a single hole, we investigate the feedback control of the nuclear spin bath through dynamical nuclear spin polarization. The scheme utilizes the hole-nuclear flip-flop by their anisotropic hyperfine interaction, where the flip direction of the nuclear spin can be conditioned on the sign of the overall hyperfine field through initialization processes that do not involve explicit measurement. We show that a negative feedback can be implemented to suppress the statistical fluctuations of the nuclear hyperfine field for enhancing the coherence time of the hole spin qubit. Positive feedback can prepare the nuclear spin ensemble into states where the nuclear hyperfine field distribution has two well separated peaks, realizing a quantum heat bath that cannot be described by a single effective temperature.

Pang, Hongliang; Gong, Zhirui; Yao, Wang

2015-01-01

53

Carbon-13 hyperfine structure of the CCCCH radical Wei Chen and Stewart E. Novick  

E-print Network

carbon position along the chain. A summary of the CCCCH spectroscopic results obtained to date is givenCarbon-13 hyperfine structure of the CCCCH radical Wei Chen and Stewart E. Novick Department on the distribution of the unpaired electron spin density along the carbon chain. The Fermi-contact constants, bF 13 C

54

Nuclear magnetometry studies of spin dynamics in quantum Hall systems  

NASA Astrophysics Data System (ADS)

We performed a nuclear magnetometry study on quantum Hall ferromagnet with a bilayer total filling factor of ?tot=2 . We found not only a rapid nuclear relaxation but also a sudden change in the nuclear-spin polarization distribution after a one-second interaction with a canted antiferromagnetic phase. We discuss the possibility of observing cooperative phenomena coming from nuclear-spin ensemble triggered by hyperfine interaction in quantum Hall system.

Fauzi, M. H.; Watanabe, S.; Hirayama, Y.

2014-12-01

55

Squeezing and entangling nuclear spins in helium 3  

E-print Network

We present a realistic model for transferring the squeezing or the entanglement of optical field modes to the collective ground state nuclear spin of $^3$He using metastability exchange collisions. We discuss in detail the requirements for obtaining good quantum state transfer efficiency and study the possibility to readout the nuclear spin state optically.

Gael Reinaudi; Alice Sinatra; Aurelien Dantan; Michel Pinard

2006-01-09

56

Interaction of acoustic waves with nuclear spins in solids  

Microsoft Academic Search

A review of the interactions of high-frequency acoustic waves with nuclear spins in solids is presented here. These interactions result from the modulation of internal magnetic fields and electric field gradients by the impressed acoustic wave. The acoustic technique is especially useful in investigating the coupling of nuclear spins to the lattice vibrations (phonons) of the solid, and in many

D. I. Bolef; R. K. Sundfors

1965-01-01

57

Self-quenching of nuclear spin dynamics in the central spin problem  

NASA Astrophysics Data System (ADS)

We consider, in the framework of the central spin s =1/2 model, driven dynamics of two electrons in a double quantum dot subject to hyperfine interaction with nuclear spins and spin-orbit coupling. The nuclear subsystem dynamically evolves in response to Landau-Zener singlet-triplet transitions of the electronic subsystem controlled by external gate voltages. Without noise and spin-orbit coupling, subsequent Landau-Zener transitions die out after about 104 sweeps, the system self-quenches, and nuclear spins reach one of the numerous glassy dark states. We present an analytical model that captures this phenomenon. We also account for the multi-nuclear-specie content of the dots and numerically determine the evolution of around 107 nuclear spins in up to 2×105 Landau-Zener transitions. Without spin-orbit coupling, self-quenching is robust and sets in for arbitrary ratios of the nuclear spin precession times and the waiting time between Landau-Zener sweeps as well as under moderate noise. In the presence of spin-orbit coupling of a moderate magnitude, and when the waiting time is in resonance with the precession time of one of the nuclear species, the dynamical evolution of nuclear polarization results in stroboscopic screening of spin-orbit coupling. However, small deviations from the resonance or strong spin-orbit coupling destroy this screening. We suggest that the success of the feedback loop technique for building nuclear gradients is based on the effect of spin-orbit coupling.

Brataas, Arne; Rashba, Emmanuel I.

2014-01-01

58

Fast electrical control of single electron spins in quantum dots with vanishing influence from nuclear spins.  

PubMed

We demonstrate fast universal electrical spin manipulation with inhomogeneous magnetic fields. With fast Rabi frequency up to 127 MHz, we leave the conventional regime of strong nuclear-spin influence and observe a spin-flip fidelity >96%, a distinct chevron Rabi pattern in the spectral-time domain, and a spin resonance linewidth limited by the Rabi frequency, not by the dephasing rate. In addition, we establish fast z rotations up to 54 MHz by directly controlling the spin phase. Our findings will significantly facilitate tomography and error correction with electron spins in quantum dots. PMID:25615383

Yoneda, J; Otsuka, T; Nakajima, T; Takakura, T; Obata, T; Pioro-Ladrière, M; Lu, H; Palmstrøm, C J; Gossard, A C; Tarucha, S

2014-12-31

59

Fast Electrical Control of Single Electron Spins in Quantum Dots with Vanishing Influence from Nuclear Spins  

NASA Astrophysics Data System (ADS)

We demonstrate fast universal electrical spin manipulation with inhomogeneous magnetic fields. With fast Rabi frequency up to 127 MHz, we leave the conventional regime of strong nuclear-spin influence and observe a spin-flip fidelity >96 % , a distinct chevron Rabi pattern in the spectral-time domain, and a spin resonance linewidth limited by the Rabi frequency, not by the dephasing rate. In addition, we establish fast z rotations up to 54 MHz by directly controlling the spin phase. Our findings will significantly facilitate tomography and error correction with electron spins in quantum dots.

Yoneda, J.; Otsuka, T.; Nakajima, T.; Takakura, T.; Obata, T.; Pioro-Ladrière, M.; Lu, H.; Palmstrøm, C. J.; Gossard, A. C.; Tarucha, S.

2014-12-01

60

Uncovering many-body correlations in nanoscale nuclear spin baths by central spin decoherence  

E-print Network

Many-body correlations can yield key insights into the nature of interacting systems; however, detecting them is often very challenging in many-particle physics, especially in nanoscale systems. Here, taking a phosphorus donor electron spin in a natural-abundance 29Si nuclear spin bath as our model system, we discover both theoretically and experimentally that many-body correlations in nanoscale nuclear spin baths produce identifiable signatures in the decoherence of the central spin under multiple-pulse dynamical decoupling control. We find that when the number of decoupling -pulses is odd, central spin decoherence is primarily driven by second-order nuclear spin correlations (pairwise flip-flop processes). In contrast, when the number of -pulses is even, fourth-order nuclear spin correlations (diagonal interaction renormalized pairwise flip-flop processes) are principally responsible for the central spin decoherence. Many-body correlations of different orders can thus be selectively detected by central spin decoherence under different dynamical decoupling controls, providing a useful approach to probing many-body processes in nanoscale nuclear spin baths.

Wen-Long Ma; Gary Wolfowicz; Nan Zhao; Shu-Shen Li; John J. L. Morton; Ren-Bao Liu

2014-04-10

61

Protection of centre spin coherence by dynamic nuclear spin polarization in diamond.  

PubMed

We experimentally investigate the protection of electron spin coherence of a nitrogen-vacancy (NV) centre in diamond by dynamic nuclear spin polarization (DNP). The electron spin decoherence of an NV centre is caused by the magnetic field fluctuation of the (13)C nuclear spin bath, which contributes large thermal fluctuation to the centre electron spin when it is in an equilibrium state at room temperature. To address this issue, we continuously transfer the angular momentum from electron spin to nuclear spins, and pump the nuclear spin bath to a polarized state under the Hartmann-Hahn condition. The bath polarization effect is verified by the observation of prolongation of the electron spin coherence time (T). Optimal conditions for the DNP process, including the pumping pulse duration and repeat numbers, are proposed by numerical simulation and confirmed by experiment. We also studied the depolarization effect of laser pulses. Our results provide a new route for quantum information processing and quantum simulation using the polarized nuclear spin bath. PMID:25042514

Liu, Gang-Qin; Jiang, Qian-Qing; Chang, Yan-Chun; Liu, Dong-Qi; Li, Wu-Xia; Gu, Chang-Zhi; Po, Hoi Chun; Zhang, Wen-Xian; Zhao, Nan; Pan, Xin-Yu

2014-09-01

62

Room temperature hyperpolarization of nuclear spins in bulk.  

PubMed

Dynamic nuclear polarization (DNP), a means of transferring spin polarization from electrons to nuclei, can enhance the nuclear spin polarization (hence the NMR sensitivity) in bulk materials at most 660 times for (1)H spins, using electron spins in thermal equilibrium as polarizing agents. By using electron spins in photo-excited triplet states instead, DNP can overcome the above limit. We demonstrate a (1)H spin polarization of 34%, which gives an enhancement factor of 250,000 in 0.40 T, while maintaining a bulk sample (? 0.6 mg, ? 0.7 × 0.7 × 1 mm(3)) containing >10(19) (1)H spins at room temperature. Room temperature hyperpolarization achieved with DNP using photo-excited triplet electrons has potentials to be applied to a wide range of fields, including NMR spectroscopy and MRI as well as fundamental physics. PMID:24821773

Tateishi, Kenichiro; Negoro, Makoto; Nishida, Shinsuke; Kagawa, Akinori; Morita, Yasushi; Kitagawa, Masahiro

2014-05-27

63

Room temperature hyperpolarization of nuclear spins in bulk  

PubMed Central

Dynamic nuclear polarization (DNP), a means of transferring spin polarization from electrons to nuclei, can enhance the nuclear spin polarization (hence the NMR sensitivity) in bulk materials at most 660 times for 1H spins, using electron spins in thermal equilibrium as polarizing agents. By using electron spins in photo-excited triplet states instead, DNP can overcome the above limit. We demonstrate a 1H spin polarization of 34%, which gives an enhancement factor of 250,000 in 0.40 T, while maintaining a bulk sample (?0.6 mg, ?0.7 × 0.7 × 1 mm3) containing >1019 1H spins at room temperature. Room temperature hyperpolarization achieved with DNP using photo-excited triplet electrons has potentials to be applied to a wide range of fields, including NMR spectroscopy and MRI as well as fundamental physics. PMID:24821773

Tateishi, Kenichiro; Negoro, Makoto; Nishida, Shinsuke; Kagawa, Akinori; Morita, Yasushi; Kitagawa, Masahiro

2014-01-01

64

Electron correlation effects on nuclear magnetic resonance spin-spin coupling constant calculations  

SciTech Connect

The chemical shifts and nuclear spin-spin coupling constants measured in nuclear magnetic resonance (NMR) experiments are related to the structure and conformation of molecules and consequently, NMR spectroscopy is an invaluable tool to practicing chemists. Accurate measurement of NMR chemical shifts and correlating spin-spin coupling constants and hence, chemical shifts are more widely used. However, NMR spin-spin coupling constants are also equally valuable. Correlating experimentally determined spin-spin coupling constants are also equally valuable. Correlating experimentally determined spin-spin coupling constants to molecular structures requires theoretical support and consequently having reliable and accurate theoretically calculated NMR spin-spin coupling constants is an important component of using experimentally determined spin-spin coupling constants. This work involves development and implementation of equation-of-motion coupled cluster singles and doubles (EOM-CCSD) quadratic and CI-like methods, in order to carry out quantitative NMR spin-spin coupling constant calculations for medium size molecules. In the calibration studies, we focus on the effects of the quadratic contribution, magnitude of the non Fermi-contact contributions, effects of the atomic basis set employed and electron correlation on NMR spin-spin coupling constant calculations with the EOM-CCSD quadratic and CI-like approximations. The results are found to be generally good, providing 13.9,8.4,7.3 and 7.6 mean absolute percent deviation from experiment, respectively, for DZP, TZP, Chipman and QZP basis sets. The overall mean absolute error of the EOM-CCSD results compared to experiment is 7%. The Fermi-contact contribution usually constitutes the largest portion of the total coupling constant. However, there are instances that the non-contact contributions are dominating, for example, HF and N{sub 2} molecules. Several interesting applications of the EOM-CCSD method have been reported.

Perera, A.J.; Bartlett, R.J. [Univ. of Florida, Gainesville, FL (United States)

1996-12-31

65

Long coherence of electron spins coupled to a nuclear spin bath  

E-print Network

Qubits, the quantum mechanical bits required for quantum computing, must retain their fragile quantum states over long periods of time. In many types of electron spin qubits, the primary source of decoherence is the interaction between the electron spins and nuclear spins of the host lattice. For electrons in gate defined GaAs quantum dots, previous spin echo measurements have revealed coherence times of about 1 $\\mu$s at low magnetic fields below 100 mT. Here, we show that coherence in such devices can actually survive to much longer times, and provide a detailed understanding of the measured nuclear spin induced decoherence. At fields above a few hundred millitesla, the coherence time measured using a single-pulse spin echo extends to 30 $\\mu$s. At lower magnetic fields, the echo first collapses, but then revives at later times given by the period of the relative Larmor precession of different nuclear species. This behavior was recently predicted, and as we show can be quantitatively accounted for by a semi-classical model for the electron spin dynamics in the presence of a nuclear spin bath. Using a multiple-pulse Carr-Purcell-Meiboom-Gill echo sequence, the decoherence time can be extended to more than 200 $\\mu$s, which represents an improvement by two orders of magnitude compared to previous measurements. This demonstration of effective methods to mitigate nuclear spin induced decoherence puts the quantum error correction threshold within reach.

Hendrik Bluhm; Sandra Foletti; Izhar Neder; Mark Rudner; Diana Mahalu; Vladimir Umansky; Amir Yacoby

2010-05-17

66

Pulsed Nuclear Magnetic Resonance: Spin Echoes MIT Department of Physics  

E-print Network

Pulsed Nuclear Magnetic Resonance: Spin Echoes MIT Department of Physics (Dated: February 5, 2014) In this experiment, the phenomenon of Nuclear Magnetic Resonance (NMR) is used to determine the magnetic moments-factor in atomic spectroscopy and is given by g = (µ/µN )/I, (2) and µN is the nuclear magneton, e /2mp

Seager, Sara

67

CARBON13 MOLECULAR STRUCTURE PARAMETERS OF RTFOT AGED ASPHALTS: THREE PROPOSED MECHANISMS FOR AROMATIZATION  

Microsoft Academic Search

The determination of average molecular structural parameters of asphalts represents an important step in describing their skeleton. Using a new method based only on the analysis of carbon-13 nuclear magnetic resonance measurements, the average molecular parameters were determined for three asphalts before and after Rolling Thin Film Oven Test aging. From the analysis of the changes in the parameters, three

Laurent Michon; Daniel A. Netzel; Bernard Hanquet; Didier Martin; Jean-Pascal Planche

1999-01-01

68

Reviews of Topical Problems: Nuclear Spin Resonance  

Microsoft Academic Search

I. Introduction 566 II. NSR energy levels and frequencies 568 1. Energy levels for resonating nuclei with spins 1 or 3\\/2 568 2. NSR energy levels for spin 5\\/2 571 III. Relative intensities of NSR lines 571 1. Relative intensities of Zeeman components in NQR 571 2. Generalized NSR equations 572 3. Relative intensities of NSR lines for spin 1

Vadim S. Grechishkin; N. E. Ainbinder

1964-01-01

69

Spin-Orbit Interaction of Nuclear Shell Structure  

E-print Network

Single particle spin-orbit interaction energy problem in nuclear shell structure is solved through negative harmonic oscillator in the self-similar-structure shell model (SSM) [4] and considering quarks' contributions on single particle spin and orbit momentum. The paper demonstrates that single particle motion in normal nuclei is described better by SSM negative harmonic oscillator than conventional shell model positive harmonic oscillator[1][2][3]. The proposed theoretical formula for spin orbit interaction energy agrees well to experiment measurements.

Xiaobin Wang; Zhengda Wang; Xiaochun Wang; Xiaodong Zhang

2012-02-29

70

Nuclear magnetic resonance spectroscopy with single spin sensitivity.  

PubMed

Nuclear magnetic resonance spectroscopy and magnetic resonance imaging at the ultimate sensitivity limit of single molecules or single nuclear spins requires fundamentally new detection strategies. The strong coupling regime, when interaction between sensor and sample spins dominates all other interactions, is one such strategy. In this regime, classically forbidden detection of completely unpolarized nuclei is allowed, going beyond statistical fluctuations in magnetization. Here we realize strong coupling between an atomic (nitrogen-vacancy) sensor and sample nuclei to perform nuclear magnetic resonance on four (29)Si spins. We exploit the field gradient created by the diamond atomic sensor, in concert with compressed sensing, to realize imaging protocols, enabling individual nuclei to be located with Angstrom precision. The achieved signal-to-noise ratio under ambient conditions allows single nuclear spin sensitivity to be achieved within seconds. PMID:25146503

Müller, C; Kong, X; Cai, J-M; Melentijevi?, K; Stacey, A; Markham, M; Twitchen, D; Isoya, J; Pezzagna, S; Meijer, J; Du, J F; Plenio, M B; Naydenov, B; McGuinness, L P; Jelezko, F

2014-01-01

71

Nuclear magnetic resonance spectroscopy with single spin sensitivity  

PubMed Central

Nuclear magnetic resonance spectroscopy and magnetic resonance imaging at the ultimate sensitivity limit of single molecules or single nuclear spins requires fundamentally new detection strategies. The strong coupling regime, when interaction between sensor and sample spins dominates all other interactions, is one such strategy. In this regime, classically forbidden detection of completely unpolarized nuclei is allowed, going beyond statistical fluctuations in magnetization. Here we realize strong coupling between an atomic (nitrogen–vacancy) sensor and sample nuclei to perform nuclear magnetic resonance on four 29Si spins. We exploit the field gradient created by the diamond atomic sensor, in concert with compressed sensing, to realize imaging protocols, enabling individual nuclei to be located with Angstrom precision. The achieved signal-to-noise ratio under ambient conditions allows single nuclear spin sensitivity to be achieved within seconds. PMID:25146503

Müller, C.; Kong, X.; Cai, J.-M.; Melentijevi?, K.; Stacey, A.; Markham, M.; Twitchen, D.; Isoya, J.; Pezzagna, S.; Meijer, J.; Du, J. F.; Plenio, M. B.; Naydenov, B.; McGuinness, L. P.; Jelezko, F.

2014-01-01

72

Engineering Nuclear spin has now been associated with Nobel Prizes  

E-print Network

Chemical Engineering Nuclear spin has now been associated with Nobel Prizes in Physics, Chemistry-2003, Professor Reimer won the Donald Sterling Noyce Prize, the AIChE Northern California Section Award and the UC

73

On the electron scattering and dephasing by the nuclear spins  

Microsoft Academic Search

We show that scattering of the conduction electrons by nuclear spins via the\\u000ahyperfine interaction may lead the upper limit on the mean free path in clean\\u000ametals. Nuclear spins with s >1\\/2 may cause a strong dephasing in dirty limit\\u000adue to the quadrupole coupling to the random potential fluctuations caused by\\u000astatic impurities and lattice imperfections.

A. M. Dyugaev; I. D. Vagner; P. Wyder

2000-01-01

74

Nuclear Spins in a Nanoscale Device for Quantum Information Processing  

E-print Network

Coherent oscillations between any two levels from four nuclear spin states of I=3/2 have been demonstrated in a nanometre-scale NMR semiconductor device, where nuclear spins are all-electrically controlled. Using this device, we discuss quantum logic operations on two fictitious qubits of the I=3/2 system, and propose a quantum state tomography scheme based on the measurement of longitudinal magnetization, $M_z$.

S. K. Ozdemir; A. Miranowicz; T. Ota; G. Yusa; N. Imoto; Y. Hirayama

2006-12-29

75

Quantum simulation of spin ordering with nuclear spins in a solid state lattice  

E-print Network

An experiment demonstrating the quantum simulation of a spin-lattice Hamiltonian is proposed. Dipolar interactions between nuclear spins in a solid state lattice can be modulated by rapid radio-frequency pulses. In this way, the effective Hamiltonian of the system can be brought to the form of an antiferromagnetic Heisenberg model with long range interactions. Using a semiconducting material with strong optical properties such as InP, cooling of nuclear spins could be achieved by means of optical pumping. An additional cooling stage is provided by adiabatic demagnetization in the rotating frame (ADRF) down to a nuclear spin temperature at which we expect a phase transition from a paramagnetic to antiferromagnetic phase. This phase transition could be observed by probing the magnetic susceptibility of the spin-lattice. Our calculations suggest that employing current optical pumping technology, observation of this phase transition is within experimental reach.

Georgios Roumpos; Cyrus P. Master; Yoshihisa Yamamoto

2006-11-21

76

Electron spin dephasing and optical pumping of nuclear spins in GaN  

NASA Astrophysics Data System (ADS)

We have measured the donor-bound electron spin dynamics in cubic GaN by time-resolved Kerr rotation experiments. The ensemble electron spin dephasing time in this quantum-dot-like system characterized by a Bohr radius of 2.5 nm is of the order of 1.5 ns as a result of the interaction with the fluctuating nuclear spins. It increases drastically when an external magnetic field as small as 10 mT is applied. We extract a dispersion of the nuclear hyperfine field ?Bn˜4mT , in agreement with calculations. We also demonstrate for the first time in GaN-based systems the optical pumping of nuclear spin yielding the buildup of a significant nuclear polarization.

Wang, G.; Zhu, C. R.; Liu, B. L.; Ye, H.; Balocchi, A.; Amand, T.; Urbaszek, B.; Yang, H.; Marie, X.

2014-09-01

77

Nuclear spin qubits in a trapped-ion quantum computer  

E-print Network

Physical systems must fulfill a number of conditions to qualify as useful quantum bits (qubits) for quantum information processing, including ease of manipulation, long decoherence times, and high fidelity readout operations. Since these conditions are hard to satisfy with a single system, it may be necessary to combine different degrees of freedom. Here we discuss a possible system, based on electronic and nuclear spin degrees of freedom in trapped ions. The nuclear spin yields long decoherence times, while the electronic spin, in a magnetic field gradient, provides efficient manipulation, and the optical transitions of the ions assure a selective and efficient initialization and readout.

M. Feng; Y. Y. Xu; F. Zhou; D. Suter

2009-04-26

78

Nuclear moments of inertia at high spins  

SciTech Connect

Nuclei with highest angular momentum are discussed. The production of high spin states, and the basic ideas associated with high spin physics are reviewed. Recent developments from continuum ..gamma..-ray studies are presented: the measurement of different average moments of inertia gives new information on the interplay between collective and single particle aspects at high spins. Finally, the exciting possibility of resolving the continuum spectra with new detector systems is examined. 8 references.

Deleplanque, M.A.

1983-12-01

79

Nuclear-spin observation of noise spectra in semiconductors  

SciTech Connect

We propose a systematic method of obtaining the spectra of noises that cause the decoherence of spins in solids. Based on this method, we experimentally show that this method can be applied to nuclear spins in semiconductors. We clarify that the spectral intensity must be derived from the long-time tail of the multiple-echo decay. To obtain higher-frequency noise, the inversion-pulse interval must be as short as possible, which required us to employ the alternating-phase Carr-Purcell sequence instead of the widely used Carr-Purcell Meiboom-Gill. For {sup 75}As nuclear spin in variously-doped GaAs, we observed a Lorentzian spectrum, instead of the commonly observed 1/f spectrum. This indicates that the nuclear spins are indeed in a coherently-controlled state.

Sasaki, Susumu; Nishimori, Masashi; Kawanago, Takashi [Department of Materials Science, Niigata University, Niigata 950-2181 (Japan); Yuge, Tatsuro [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan); Hirayama, Yoshiro [Department of Physics, Tohoku University, Sendai 980-8578, Japan and JST-ERATO Nuclear Spin Electronics Project, Sendai 980-8578 (Japan)

2013-12-04

80

Nuclear-spin observation of noise spectra in semiconductors  

NASA Astrophysics Data System (ADS)

We propose a systematic method of obtaining the spectra of noises that cause the decoherence of spins in solids. Based on this method, we experimentally show that this method can be applied to nuclear spins in semiconductors. We clarify that the spectral intensity must be derived from the long-time tail of the multiple-echo decay. To obtain higher-frequency noise, the inversion-pulse interval must be as short as possible, which required us to employ the alternating-phase Carr-Purcell sequence instead of the widely used Carr-Purcell Meiboom-Gill. For 75As nuclear spin in variously-doped GaAs, we observed a Lorentzian spectrum, instead of the commonly observed 1/f spectrum. This indicates that the nuclear spins are indeed in a coherently-controlled state.

Sasaki, Susumu; Yuge, Tatsuro; Nishimori, Masashi; Kawanago, Takashi; Hirayama, Yoshiro

2013-12-01

81

Spin density matrices for nuclear density functionals with parity violations  

E-print Network

The spin density matrix (SDM) used in atomic and molecular physics is revisited for nuclear physics, in the context of the radial density functional theory. The vector part of the SDM defines a "hedgehog" situation, which exists only if nuclear states contain some amount of parity violation.

B. R. Barrett; B. G. Giraud

2010-04-26

82

Spin squeezing of a cold atomic ensemble with the nuclear spin of one-half  

E-print Network

To establish an applicable system for advanced quantum information processing between light and atoms, we have demonstrated the quantum non-demolition (QND) measurement with a collective spin of cold ytterbium atoms (171Yb), and observed 1.8 (-1.5, +2.4) dB spin squeezing. Since a 171Yb atom has only a nuclear spin of 1/2 in the ground state, the system is the simplest spin ensemble and robust against decoherence. We used very short pulses with the width of 100 ns, so the interaction time became much shorter than the decoherence time, which is important for multi-step quantum information processing.

Takano, T; Namiki, R; Takahashi, Y

2008-01-01

83

Spin squeezing of a cold atomic ensemble with the nuclear spin of one-half  

E-print Network

To establish an applicable system for advanced quantum information processing between light and atoms, we have demonstrated the quantum non-demolition (QND) measurement with a collective spin of cold ytterbium atoms (171Yb), and observed 1.8 (-1.5, +2.4) dB spin squeezing. Since a 171Yb atom has only a nuclear spin of 1/2 in the ground state, the system is the simplest spin ensemble and robust against decoherence. We used very short pulses with the width of 100 ns, so the interaction time became much shorter than the decoherence time, which is important for multi-step quantum information processing.

T. Takano; M. Fuyama; R. Namiki; Y. Takahashi

2008-08-18

84

Calculation of nuclear spin-spin coupling constants using frozen density embedding  

NASA Astrophysics Data System (ADS)

We present a method for a subsystem-based calculation of indirect nuclear spin-spin coupling tensors within the framework of current-spin-density-functional theory. Our approach is based on the frozen-density embedding scheme within density-functional theory and extends a previously reported subsystem-based approach for the calculation of nuclear magnetic resonance shielding tensors to magnetic fields which couple not only to orbital but also spin degrees of freedom. This leads to a formulation in which the electron density, the induced paramagnetic current, and the induced spin-magnetization density are calculated separately for the individual subsystems. This is particularly useful for the inclusion of environmental effects in the calculation of nuclear spin-spin coupling constants. Neglecting the induced paramagnetic current and spin-magnetization density in the environment due to the magnetic moments of the coupled nuclei leads to a very efficient method in which the computationally expensive response calculation has to be performed only for the subsystem of interest. We show that this approach leads to very good results for the calculation of solvent-induced shifts of nuclear spin-spin coupling constants in hydrogen-bonded systems. Also for systems with stronger interactions, frozen-density embedding performs remarkably well, given the approximate nature of currently available functionals for the non-additive kinetic energy. As an example we show results for methylmercury halides which exhibit an exceptionally large shift of the one-bond coupling constants between 199Hg and 13C upon coordination of dimethylsulfoxide solvent molecules.

Götz, Andreas W.; Autschbach, Jochen; Visscher, Lucas

2014-03-01

85

Calculation of nuclear spin-spin coupling constants using frozen density embedding.  

PubMed

We present a method for a subsystem-based calculation of indirect nuclear spin-spin coupling tensors within the framework of current-spin-density-functional theory. Our approach is based on the frozen-density embedding scheme within density-functional theory and extends a previously reported subsystem-based approach for the calculation of nuclear magnetic resonance shielding tensors to magnetic fields which couple not only to orbital but also spin degrees of freedom. This leads to a formulation in which the electron density, the induced paramagnetic current, and the induced spin-magnetization density are calculated separately for the individual subsystems. This is particularly useful for the inclusion of environmental effects in the calculation of nuclear spin-spin coupling constants. Neglecting the induced paramagnetic current and spin-magnetization density in the environment due to the magnetic moments of the coupled nuclei leads to a very efficient method in which the computationally expensive response calculation has to be performed only for the subsystem of interest. We show that this approach leads to very good results for the calculation of solvent-induced shifts of nuclear spin-spin coupling constants in hydrogen-bonded systems. Also for systems with stronger interactions, frozen-density embedding performs remarkably well, given the approximate nature of currently available functionals for the non-additive kinetic energy. As an example we show results for methylmercury halides which exhibit an exceptionally large shift of the one-bond coupling constants between (199)Hg and (13)C upon coordination of dimethylsulfoxide solvent molecules. PMID:24628152

Götz, Andreas W; Autschbach, Jochen; Visscher, Lucas

2014-03-14

86

Calculation of nuclear spin-spin coupling constants using frozen density embedding  

SciTech Connect

We present a method for a subsystem-based calculation of indirect nuclear spin-spin coupling tensors within the framework of current-spin-density-functional theory. Our approach is based on the frozen-density embedding scheme within density-functional theory and extends a previously reported subsystem-based approach for the calculation of nuclear magnetic resonance shielding tensors to magnetic fields which couple not only to orbital but also spin degrees of freedom. This leads to a formulation in which the electron density, the induced paramagnetic current, and the induced spin-magnetization density are calculated separately for the individual subsystems. This is particularly useful for the inclusion of environmental effects in the calculation of nuclear spin-spin coupling constants. Neglecting the induced paramagnetic current and spin-magnetization density in the environment due to the magnetic moments of the coupled nuclei leads to a very efficient method in which the computationally expensive response calculation has to be performed only for the subsystem of interest. We show that this approach leads to very good results for the calculation of solvent-induced shifts of nuclear spin-spin coupling constants in hydrogen-bonded systems. Also for systems with stronger interactions, frozen-density embedding performs remarkably well, given the approximate nature of currently available functionals for the non-additive kinetic energy. As an example we show results for methylmercury halides which exhibit an exceptionally large shift of the one-bond coupling constants between {sup 199}Hg and {sup 13}C upon coordination of dimethylsulfoxide solvent molecules.

Götz, Andreas W., E-mail: agoetz@sdsc.edu [San Diego Supercomputer Center, University of California San Diego, 9500 Gilman Dr MC 0505, La Jolla, California 92093-0505 (United States); Autschbach, Jochen [Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260-3000 (United States)] [Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260-3000 (United States); Visscher, Lucas, E-mail: visscher@chem.vu.nl [Amsterdam Center for Multiscale Modeling (ACMM), VU University Amsterdam, Theoretical Chemistry, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands)] [Amsterdam Center for Multiscale Modeling (ACMM), VU University Amsterdam, Theoretical Chemistry, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands)

2014-03-14

87

Nuclear-spin dependent parity violation in diatomic molecular ions  

E-print Network

Nuclear-spin-dependent (NSD) parity violating (PV) effects can be strongly enhanced in diatomic molecules containing heavy atoms. Future measurements are anticipated to provide nuclear anapole moments and strength constants for PV nuclear forces. In light molecules, the NSD electroweak electron-nucleus interaction may also be detected. Here we calculate NSD PV effects for molecular ions. Our calculations are motivated by rapid developments in trapping techniques for such systems at low temperatures.

Borschevsky, A; Dzuba, V A; Beloy, K; Flambaum, V V; Schwerdtfeger, P A

2012-01-01

88

Spin constraints on nuclear energy density functionals  

NASA Astrophysics Data System (ADS)

The Gallagher-Moszkowski rule in the spectroscopy of odd-odd nuclei imposes a new spin constraint on the energy functionals for self-consistent mean field theory. The commonly used parametrization of the effective three-body interaction in the Gogny and Skyrme families of energy functionals is ill suited to satisfy the spin constraint. In particular, the Gogny parametrization of the three-body interaction has the spin dependence opposite to that required by the observed spectra. The two-body part has a correct sign, but in combination the rule is violated as often as not. We conclude that a new functional form is needed for the effective three-body interaction that can take into better account the different spin-isospin channels of the interaction.

Robledo, L. M.; Bernard, R. N.; Bertsch, G. F.

2014-02-01

89

The Nuclear Cusp Condition in Spin-Polarized Thomas - Theory.  

NASA Astrophysics Data System (ADS)

Thomas-Fermi theory, which was introduced in the 1920s, was developed into rigorous mathematics in the 1970s by Lieb, Simon, Benilan, Brezis, and others. Later, Goldstein and Rieder extended rigorous Thomas-Fermi theory to a spin polarized context, to include the nuclear cusp condition, and to the case where a magnetic field is present. But they did not investigate incorporating the nuclear cusp condition into the spin polarized context. The purpose of my thesis is to do precisely that. I proved the existence and uniqueness of the problem of minimizing the energy functional by solving a non-linear elliptic partial differential equation on { bf R}^3 which arose from the Euler -Lagrange equation. A topological argument then related the Lagrange multipliers to the numbers of spin up and spin down electrons.

Lung, Chien-An.

90

Fast room-temperature phase gate on a single nuclear spin in diamond.  

PubMed

Nuclear spins support long lived quantum coherence due to weak coupling to the environment, but are difficult to rapidly control using nuclear magnetic resonance as a result of the small nuclear magnetic moment. We demonstrate a fast ?500??ns nuclear spin phase gate on a (14)N nuclear spin qubit intrinsic to a nitrogen-vacancy center in diamond. The phase gate is enabled by the hyperfine interaction and off-resonance driving of electron spin transitions. Repeated applications of the phase gate bang-bang decouple the nuclear spin from the environment, locking the spin state for up to ?140???s. PMID:25062156

Sangtawesin, S; Brundage, T O; Petta, J R

2014-07-11

91

Imaging mesoscopic nuclear spin noise with a diamond magnetometer  

E-print Network

Magnetic Resonance Imaging (MRI) can characterize and discriminate among tissues using their diverse physical and biochemical properties. Unfortunately, submicrometer screening of biological specimens is presently not possible, mainly due to lack of detection sensitivity. Here we analyze the use of a nitrogen-vacancy center in diamond as a magnetic sensor for nanoscale nuclear spin imaging and spectroscopy. We examine the ability of such a sensor to probe the fluctuations of the "classical" dipolar field due to a large number of neighboring nuclear spins in a densely protonated sample. We identify detection protocols that appropriately take into account the quantum character of the sensor and find a signal-to-noise ratio compatible with realistic experimental parameters. Through various example calculations we illustrate different kinds of image contrast. In particular, we show how to exploit the comparatively long nuclear spin correlation times to reconstruct a local, high-resolution sample spectrum.

C. A. Meriles; L. Jiang; G. Goldstein; J. S. Hodges; J. R. Maze; M. D. Lukin; P. Cappellaro

2010-04-30

92

Single shot NMR on single, dark nuclear spins  

E-print Network

The electron and nuclear spins associated with the nitrogen-vacancy (NV) center in diamond are supposed to be building blocks for quantum computing devices and nanometer scale magnetometry operating under ambient conditions. For every such building block precise knowledge of the involved quantum states is crucial. Especially for solid state systems the corresponding hilbert space can be large. Here, we experimentally show that under usual operating conditions the NV color center exists in an equilibrium of two charge states (i.e. 70% in the usually used negative (NV-) and 30% in the neutral one (NV0)). Projective quantum non-demolition measurement of the nitrogen nuclear spin enables the detection even of the additional, optically inactive state. It turns out that the nuclear spin can be coherently driven also in NV0. However, its T1 ~ 90 ms and T2 ~ 6micro-s times are much shorter than in NV-, supposedly because of the dynamic Jahn-Teller effect.

Waldherr, G; Steiner, M; Neumann, P; Gali, A; Jelezko, F; Wrachtrup, J

2010-01-01

93

Local manipulation of nuclear spin in a semiconductor quantum well.  

PubMed

The shaping of nuclear spin polarization profiles and the induction of nuclear resonances are demonstrated within a parabolic quantum well using an externally applied gate voltage. Voltage control of the electron and hole wave functions results in nanometer-scale sheets of polarized nuclei positioned along the growth direction of the well. Applying rf voltages across the gates induces resonant spin transitions of selected isotopes. This depolarizing effect depends strongly on the separation of electrons and holes, suggesting that a highly localized mechanism accounts for the observed behavior. PMID:14683395

Poggio, M; Steeves, G M; Myers, R C; Kato, Y; Gossard, A C; Awschalom, D D

2003-11-14

94

Electrical injection of spin-polarized electrons and electrical detection of dynamic nuclear polarization using a Heusler alloy spin source  

NASA Astrophysics Data System (ADS)

We demonstrated electrical spin injection from a half-metallic Heusler alloy Co2MnSi electrode into a GaAs channel through observation of a spin-valve signal and a Hanle signal in the four-terminal nonlocal geometry. Furthermore, we electrically detected a nuclear field acting on electron spins, which was produced by the dynamic nuclear polarization, through observation of transient oblique Hanle signals. Samples with a Co2MnSi spin source exhibited higher spin-injection efficiency and a larger nuclear field compared to samples with a Co50Fe50 spin source, suggesting that the spin polarization of Co2MnSi is higher. This higher polarization is promising for realizing future spintronic devices and for understanding spin interactions as well as spin-dependent transport properties in a semiconductor channel.

Akiho, Takafumi; Shan, Jinhai; Liu, Hong-xi; Matsuda, Ken-ichi; Yamamoto, Masafumi; Uemura, Tetsuya

2013-06-01

95

Long coherence of electron spins coupled to a nuclear spin bath  

E-print Network

Qubits, the quantum mechanical bits required for quantum computing, must retain their fragile quantum states over long periods of time. In many types of electron spin qubits, the primary source of decoherence is the interaction between the electron spins and nuclear spins of the host lattice. For electrons in gate defined GaAs quantum dots, previous spin echo measurements have revealed coherence times of about 1 $\\mu$s at low magnetic fields below 100 mT. Here, we show that coherence in such devices can actually survive to much longer times, and provide a detailed understanding of the measured nuclear spin induced decoherence. At fields above a few hundred millitesla, the coherence time measured using a single-pulse spin echo extends to 30 $\\mu$s. At lower magnetic fields, the echo first collapses, but then revives at later times given by the period of the relative Larmor precession of different nuclear species. This behavior was recently predicted, and as we show can be quantitatively accounted for by a semi...

Bluhm, Hendrik; Neder, Izhar; Rudner, Mark; Mahalu, Diana; Umansky, Vladimir; Yacoby, Amir

2010-01-01

96

Dynamics of a mesoscopic nuclear spin ensemble interacting with an optically driven electron spin  

NASA Astrophysics Data System (ADS)

The ability to discriminate between simultaneously occurring noise sources in the local environment of semiconductor InGaAs quantum dots, such as electric and magnetic field fluctuations, is key to understanding their respective dynamics and their effect on quantum dot coherence properties. We present a discriminatory approach to all-optical sensing based on two-color resonance fluorescence of a quantum dot charged with a single electron. Our measurements show that local magnetic field fluctuations due to nuclear spins in the absence of an external magnetic field are described by two correlation times, both in the microsecond regime. The nuclear spin bath dynamics show a strong dependence on the strength of resonant probing, with correlation times increasing by a factor of 4 as the optical transition is saturated. We interpret the behavior as motional averaging of both the Knight field of the resident electron spin and the hyperfine-mediated nuclear spin-spin interaction due to optically induced electron spin flips.

Stanley, M. J.; Matthiesen, C.; Hansom, J.; Le Gall, C.; Schulte, C. H. H.; Clarke, E.; Atatüre, M.

2014-11-01

97

Quantum Information Transport in Nuclear Spin Chains  

Microsoft Academic Search

In many solid-state proposals for quantum computers, the transport of information over relatively short distances inside the quantum processor itself is an essential task, and one for which relying on photons, and therefore on a frequent exchanging of information between solid-state and light qubits, could be too costly. Quantum wires based on spins could be a viable alternative leading to

Paola Cappellaro; David Cory

2007-01-01

98

Coherent control of hyperfine-coupled electron and nuclear spins for quantum information processing  

E-print Network

Coupled electron-nuclear spins are promising physical systems for quantum information processing: By combining the long coherence times of the nuclear spins with the ability to initialize, control, and measure the electron ...

Yang, Jamie Chiaming

2008-01-01

99

Quantum read-out and fast initialization of nuclear spin qubits with electric currents  

E-print Network

Nuclear spin qubits have the longest coherence times in the solid state, but their quantum read-out and initialization is a great challenge. We present a theory for the interaction of an electric current with the nuclear spins of donor impurities in semiconductors. The theory yields a sensitivity criterion for quantum detection of nuclear spin states using electrically detected magnetic resonance, as well as an all electrical method for fast nuclear spin qubit initialization.

Noah Stemeroff; Rogerio de Sousa

2011-08-02

100

A silicon-based nuclear spin quantum computer  

Microsoft Academic Search

Quantum computers promise to exceed the computational efficiency of ordinary classical machines because quantum algorithms allow the execution of certain tasks in fewer steps. But practical implementation of these machines poses a formidable challenge. Here I present a scheme for implementing a quantum-mechanical computer. Information is encoded onto the nuclear spins of donor atoms in doped silicon electronic devices. Logical

B. E. Kane

1998-01-01

101

Nuclear Spin Gyroscope Based on an Atomic Comagnetometer  

SciTech Connect

We describe a nuclear spin gyroscope based on an alkali-metal-noble-gas comagnetometer. Optically pumped alkali-metal vapor is used to polarize the noble-gas atoms and detect their gyroscopic precession. Spin precession due to magnetic fields as well as their gradients and transients can be cancelled in this arrangement. The sensitivity is enhanced by using a high-density alkali-metal vapor in a spin-exchange relaxation free regime. With a K-{sup 3}He comagnetometer we demonstrate rotation sensitivity of 5x10{sup -7} rad s{sup -1} Hz{sup -1/2}, equivalent to a magnetic field sensitivity of 2.5 fT/Hz{sup 1/2}. The rotation signal can be increased by a factor of 10 using {sup 21}Ne with a smaller magnetic moment. The comagnetometer is also a promising tool in searches for anomalous spin couplings beyond the standard model.

Kornack, T.W.; Ghosh, R.K.; Romalis, M.V. [Department of Physics, Princeton University, Princeton, New Jersey 08550 (United States)

2005-12-02

102

Nuclear spin gyroscope based on an atomic comagnetometer.  

PubMed

We describe a nuclear spin gyroscope based on an alkali-metal-noble-gas comagnetometer. Optically pumped alkali-metal vapor is used to polarize the noble-gas atoms and detect their gyroscopic precession. Spin precession due to magnetic fields as well as their gradients and transients can be cancelled in this arrangement. The sensitivity is enhanced by using a high-density alkali-metal vapor in a spin-exchange relaxation free regime. With a K-3He comagnetometer we demonstrate rotation sensitivity of 5 x 10(-7) rad s(-1) Hz(-1/2), equivalent to a magnetic field sensitivity of 2.5 fT/Hz(1/2). The rotation signal can be increased by a factor of 10 using 21Ne with a smaller magnetic moment. The comagnetometer is also a promising tool in searches for anomalous spin couplings beyond the standard model. PMID:16384290

Kornack, T W; Ghosh, R K; Romalis, M V

2005-12-01

103

Nuclear spin dynamics in parabolic quantum wells Ionel Tifrea* and Michael E. Flatte  

E-print Network

Nuclear spin dynamics in parabolic quantum wells Ionel T¸ifrea* and Michael E. Flatte´ Department March 2004 We present a detailed analytical and numerical analysis of the nuclear spin dynamics of the electronic wave function in small electric fields. The nuclear spin relaxation via the hyperfine interaction

Flatte, Michael E.

104

Nuclear spin selection rules in chemical reactions by angular momentum algebra  

E-print Network

Nuclear spin selection rules in chemical reactions by angular momentum algebra Takeshi Oka of the representations of the permutation­inversion group for both nuclear spin and rovibronic coordinate wavefunctions, those of the rotation group for nuclear spin wavefunction only are used. The method allows more

Oka, Takeshi

105

Dynamics of the Measurement of Nuclear Spins in a Solid-State Quantum Computer  

Microsoft Academic Search

We study numerically the process of nuclear spin measurement in a solid-state quantum computer of the type proposed by Kane by modeling the quantum dynamics of two coupled nuclear spins on $^{31}$P donors implanted in silicon. We estimate the minimum measurement time necessary for the reliable transfer of quantum information from the nuclear spin subsystem to the electronic subsystem. We

Gennady P. Berman; David K. Campbell; Gary D. Doolen; Kirill E. Nagaev

1999-01-01

106

Electron-nuclear spin dynamics in a mesoscopic solid-state quantum computer  

Microsoft Academic Search

We numerically simulate the process of nuclear spin measurement in Kane's quantum computer. For this purpose, we model the quantum dynamics of two coupled nuclear spins on 31P donors implanted in Si. We estimate the minimum time of measurement necessary for the reliable transfer of quantum information from the nuclear spin subsystem to the electronic subsystem. We also calculate the

Gennady P. Berman; David K. Campbell; Gary D. Doolen; Kirill E. Nagaev

1999-01-01

107

High-dynamic-range magnetometry with a single nuclear spin in diamond  

E-print Network

High-dynamic-range magnetometry with a single nuclear spin in diamond G. Waldherr1 *, J. Beck1 , P, we implement a quantum phase estimation algorithm6­8 on a single nuclear spin in diamond to combine coherence times4 , even at ambient conditions, and coherent coupling to nearby nuclear spins11,12 . Its

Pfeifer, Holger

108

Theory of long-lived nuclear spin states in solution nuclear magnetic resonance. II. Singlet spin locking  

NASA Astrophysics Data System (ADS)

In a previous paper [M. Carravetta and M. H. Levitt, J. Chem. Phys. 122, 214505 (2005)], we presented the theory of long-lived nuclear spin singlet states in low magnetic field. In this paper, we consider the spin locking of long-lived singlet states in high magnetic field by the application of resonant radio frequency irradiation. We present theoretical results for unmodulated irradiation, including approximate analytical expressions for the singlet decay rate constants. We show the results of numerical simulations, which indicate that modulated radio frequency fields may be used to achieve broadband spin locking of singlet states but only in the case of a small difference in Larmor frequencies between the members of the spin pair.

Pileio, Giuseppe; Levitt, Malcolm H.

2009-06-01

109

Probing the dynamics of a nuclear spin bath in diamond through time-resolved central spin magnetometry.  

PubMed

Using fast electron spin resonance spectroscopy of a single nitrogen-vacancy defect in diamond, we demonstrate real-time readout of the Overhauser field produced by its nuclear spin environment under ambient conditions. These measurements enable narrowing the Overhauser field distribution by postselection, corresponding to a conditional preparation of the nuclear spin bath. Correlations of the Overhauser field fluctuations are quantitatively inferred by analyzing the Allan deviation over consecutive measurements. This method allows us to extract the dynamics of weakly coupled nuclear spins of the reservoir. PMID:25302916

Dréau, A; Jamonneau, P; Gazzano, O; Kosen, S; Roch, J-F; Maze, J R; Jacques, V

2014-09-26

110

Room-temperature optical manipulation of nuclear spin polarization in GaAsN  

NASA Astrophysics Data System (ADS)

The effect of hyperfine interaction on the room-temperature defect-enabled spin filtering effect in GaAsN alloys is experimentally investigated and theoretically interpreted through a master equation approach based on the hyperfine and Zeeman interaction between electron and nuclear spin of the Gai2+ interstitial spin filtering defect. We show that the nuclear spin polarization of the gallium defect can be tuned through the optically induced spin polarization of conduction band electrons.

Sandoval-Santana, C.; Balocchi, A.; Amand, T.; Harmand, J. C.; Kunold, A.; Marie, X.

2014-09-01

111

Hyperfine switching triggered by resonant tunneling for the detection of a single nuclear spin qubit  

Microsoft Academic Search

A novel detection mechanism and a robust control of a single nuclear spin-flip by hyperfine interactions between the nuclear spin and tunneling electron spin are proposed on the basis of ab initio non-equilibrium Green's function calculations. The calculated relaxation times of the nuclear spin of proton in a nano-contact system, Pd(electrode)–H2–Pd(electrode), show that ON\\/OFF switching of hyperfine interactions is effectively

Tomofumi Tada

2008-01-01

112

RF instrumentation and system design for coherent control of anisotropic hyperfine-coupled electron/nuclear spin qubits  

E-print Network

Coherent control is a fundamental challenge in quantum information processing (QIP). Our system of interest employs a local, isolated electron spin to coherently control nuclear spins. Coupled electron/nuclear spins are a ...

Abutaleb, Mohamed Osama

2010-01-01

113

Spin Density Matrices for Nuclear Density Functionals with Parity Violation  

NASA Astrophysics Data System (ADS)

Within the context of the radial density functional [1], we apply the spin density matrix (SDM) used in atomic and molecular physics [2] to nuclear physics. The vector part of the SDM defines a ``hedgehog'' situation, which exists only if nuclear states contain some amount of parity violation. Thus, looking for the vector profile of the SDM could be used as a test for parity violation in nuclei. The difference between the scalar profile and the vector profile of the SDM will be illustrated by a toy model. [4pt] [1] B. G. Giraud, Phys. Rev. C 78, 014307 (2008).[0pt] [2] A. Goerling, Phys. Rev. A 47, 2783 (1993).

Barrett, Bruce; Giraud, Bertrand

2010-11-01

114

Single shot NMR on single, dark nuclear spins  

Microsoft Academic Search

The electron and nuclear spins associated with the nitrogen-vacancy (NV)\\u000acenter in diamond are supposed to be building blocks for quantum computing\\u000adevices and nanometer scale magnetometry operating under ambient conditions.\\u000aFor every such building block precise knowledge of the involved quantum states\\u000ais crucial. Especially for solid state systems the corresponding hilbert space\\u000acan be large. Here, we experimentally

G. Waldherr; J. Beck; M. Steiner; P. Neumann; A. Gali; F. Jelezko; J. Wrachtrup

2010-01-01

115

$?$-nuclear spin-orbit coupling from two-pion exchange  

E-print Network

Using SU(3) chiral perturbation theory we calculate the density-dependent complex-valued spin-orbit coupling strength $U_{\\Sigma ls}(k_f)+ i W_{\\Sigma ls}(k_f)$ of a $\\Sigma$ hyperon in the nuclear medium. The leading long-range $\\Sigma N$ interaction arises from iterated one-pion exchange with a $\\Lambda$ or a $\\Sigma$ hyperon in the intermediate state. We find from this unique long-range dynamics a sizeable ``wrong-sign'' spin-orbit coupling strength of $U_{\\Sigma ls}(k_{f0}) \\simeq -20$ MeVfm$^2$ at normal nuclear matter density $\\rho_0 = 0.16 $fm$^{-3}$. The strong $\\Sigma N\\to \\Lambda N$ conversion process contributes at the same time an imaginary part of $W_{\\Sigma ls}(k_{f0}) \\simeq -12$ MeVfm$^2$. When combined with estimates of the short-range contribution the total $\\Sigma$-nuclear spin-orbit coupling becomes rather weak.

N. Kaiser

2007-11-14

116

Manipulation of the nuclear spin ensemble in a quantum dot with chirped magnetic resonance pulses.  

PubMed

The nuclear spins in nanostructured semiconductors play a central role in quantum applications. The nuclear spins represent a useful resource for generating local magnetic fields but nuclear spin noise represents a major source of dephasing for spin qubits. Controlling the nuclear spins enhances the resource while suppressing the noise. NMR techniques are challenging: the group III and V isotopes have large spins with widely different gyromagnetic ratios; in strained material there are large atom-dependent quadrupole shifts; and nanoscale NMR is hard to detect. We report NMR on 100,000 nuclear spins of a quantum dot using chirped radiofrequency pulses. Following polarization, we demonstrate a reversal of the nuclear spin. We can flip the nuclear spin back and forth a hundred times. We demonstrate that chirped NMR is a powerful way of determining the chemical composition, the initial nuclear spin temperatures and quadrupole frequency distributions for all the main isotopes. The key observation is a plateau in the NMR signal as a function of sweep rate: we achieve inversion at the first quantum transition for all isotopes simultaneously. These experiments represent a generic technique for manipulating nanoscale inhomogeneous nuclear spin ensembles and open the way to probe the coherence of such mesoscopic systems. PMID:25150719

Munsch, Mathieu; Wüst, Gunter; Kuhlmann, Andreas V; Xue, Fei; Ludwig, Arne; Reuter, Dirk; Wieck, Andreas D; Poggio, Martino; Warburton, Richard J

2014-09-01

117

Manipulation of the nuclear spin ensemble in a quantum dot with chirped magnetic resonance pulses  

NASA Astrophysics Data System (ADS)

The nuclear spins in nanostructured semiconductors play a central role in quantum applications. The nuclear spins represent a useful resource for generating local magnetic fields but nuclear spin noise represents a major source of dephasing for spin qubits. Controlling the nuclear spins enhances the resource while suppressing the noise. NMR techniques are challenging: the group III and V isotopes have large spins with widely different gyromagnetic ratios; in strained material there are large atom-dependent quadrupole shifts; and nanoscale NMR is hard to detect. We report NMR on 100,000 nuclear spins of a quantum dot using chirped radiofrequency pulses. Following polarization, we demonstrate a reversal of the nuclear spin. We can flip the nuclear spin back and forth a hundred times. We demonstrate that chirped NMR is a powerful way of determining the chemical composition, the initial nuclear spin temperatures and quadrupole frequency distributions for all the main isotopes. The key observation is a plateau in the NMR signal as a function of sweep rate: we achieve inversion at the first quantum transition for all isotopes simultaneously. These experiments represent a generic technique for manipulating nanoscale inhomogeneous nuclear spin ensembles and open the way to probe the coherence of such mesoscopic systems.

Munsch, Mathieu; Wüst, Gunter; Kuhlmann, Andreas V.; Xue, Fei; Ludwig, Arne; Reuter, Dirk; Wieck, Andreas D.; Poggio, Martino; Warburton, Richard J.

2014-09-01

118

Algebraic-diagrammatic construction polarization propagator approach to indirect nuclear spin-spin coupling constants  

NASA Astrophysics Data System (ADS)

A new polarization propagator approach to indirect nuclear spin-spin coupling constantans is formulated within the framework of the algebraic-diagrammatic construction (ADC) approximation and implemented at the level of the strict second-order approximation scheme, ADC(2). The ADC approach possesses transparent computational procedure operating with Hermitian matrix quantities defined with respect to physical excitations. It is size-consistent and easily extendable to higher orders via the hierarchy of available ADC approximation schemes. The ADC(2) method is tested in the first applications to HF, N2, CO, H2O, HCN, NH3, CH4, C2H2, PH3, SiH4, CH3F, and C2H4. The calculated indirect nuclear spin-spin coupling constants are in good agreement with the experimental data and results of the second-order polarization propagator approximation method. The computational effort of the ADC(2) scheme scales as n5 with respect to the number of molecular orbitals n, which makes this method promising for applications to larger molecules.

Rusakova, I. L.; Krivdin, L. B.; Rusakov, Yu. Yu.; Trofimov, A. B.

2012-07-01

119

The Mirror Charge Exchange Reaction CARBON-13  

NASA Astrophysics Data System (ADS)

Differential cross sections have been measured near 0^circ for the dominant channels in the mirror reaction ^ {13}C(^{13}N,^{13 }C)^{13}N at E/A = 57 and 105 MeV. The cross sections of the peaks in the excitation spectrum are discussed in terms of the Gamow-Teller and Fermi transition strengths in the target and the projectile. The cross section per unit Gamow-Teller strength is found to be enhanced relative to that for unit Fermi strength when compared with previous results from (p,n) reactions. The use of heavy ions as probes for weak-interaction strengths in radioactive nuclei is discussed. The present work represents the first use of mirror symmetry to study heavy-ion charge exchange as well as the first application of the developing radioactive nuclear beam field to this area.

Steiner, Mathias

120

Solid effect in magic angle spinning dynamic nuclear polarization  

NASA Astrophysics Data System (ADS)

For over five decades, the solid effect (SE) has been heavily utilized as a mechanism for performing dynamic nuclear polarization (DNP). Nevertheless, it has not found widespread application in contemporary, high magnetic field DNP experiments because SE enhancements display an ? _0 ^{ - 2} field dependence. In particular, for nominally forbidden zero and double quantum SE transitions to be partially allowed, it is necessary for mixing of adjacent nuclear spin states to occur, and this leads to the observed field dependence. However, recently we have improved our instrumentation and report here an enhancement of ? = 91 obtained with the organic radical trityl (OX063) in magic angle spinning experiments performed at 5 T and 80 K. This is a factor of 6-7 higher than previous values in the literature under similar conditions. Because the solid effect depends strongly on the microwave field strength, we attribute this large enhancement to larger microwave field strengths inside the sample volume, achieved with more efficient coupling of the gyrotron to the sample chamber. In addition, we develop a theoretical model to explain the dependence of the buildup rate of enhanced nuclear polarization and the steady-state enhancement on the microwave power. Buildup times and enhancements were measured as a function of 1H concentration for both trityl and Gd-DOTA. Comparison of the results indicates that for trityl the initial polarization step is the slower, rate-determining step. However, for Gd-DOTA the spread of nuclear polarization via homonuclear 1H spin diffusion is rate-limiting. Finally, we discuss the applicability of the solid effect at fields > 5 T and the requirements to address the unfavorable field dependence of the solid effect.

Corzilius, Björn; Smith, Albert A.; Griffin, Robert G.

2012-08-01

121

Single crystal nuclear magnetic resonance in spinning powders  

NASA Astrophysics Data System (ADS)

We present a method for selectively exciting nuclear magnetic resonances (NMRs) from well-defined subsets of crystallites from a powdered sample under magic angle spinning. Magic angle spinning induces a time dependence in the anisotropic interactions, which results in a time variation of the resonance frequencies which is different for different crystallite orientations. The proposed method exploits this by applying selective pulses, which we refer to as XS (for crystallite-selective) pulses, that follow the resonance frequencies of nuclear species within particular crystallites, resulting in the induced flip angle being orientation dependent. By selecting the radiofrequency field to deliver a 180 ? pulse for the target orientation and employing a train of such pulses combined with cogwheel phase cycling, we obtain a high degree of orientational selectivity with the resulting spectrum containing only contributions from orientations close to the target. Typically, this leads to the selection of between 0.1% and 10% of the crystallites, and in extreme cases to the excitation of a single orientation resulting in single crystal spectra of spinning powders. Two formulations of this method are described and demonstrated with experimental examples on [1 - 13C]-alanine and the paramagnetic compound Sm2Sn2O7.

Pell, Andrew J.; Pintacuda, Guido; Emsley, Lyndon

2011-10-01

122

Nuclear Spin Maser at Highly Stabilized Low Magnetic Field and Search for Atomic EDM  

SciTech Connect

A nuclear spin maser is operated at a low static field through an active feedback scheme based on an optical nuclear spin detection and succeeding spin control by a transverse field application. The frequency stability of this optical-coupling spin maser is improved by installation of a low-noise current source for a solenoid magnet producing a static magnetic field in the maser operation. Experimental devices for application of the maser to EDM experiment are being developed.

Yoshimi, A. [RIKEN Nishina Center, Hirosawa 2-1, Wako, Saitama 351-0198 (Japan); Asahi, K.; Inoue, T.; Uchida, M.; Hatakeyama, N.; Tsuchiya, M.; Kagami, S. [Department of Physics, Tokyo Institute of Technology, Oh-okayama 2-12-1, Meguro, Tokyo 152-8551 (Japan)

2009-08-04

123

Fully relativistic calculation of nuclear magnetic shieldings and indirect nuclear spin-spin couplings in group-15 and -16 hydrides  

NASA Astrophysics Data System (ADS)

Fully relativistic calculations of the isotropic and anisotropic parts of both indirect nuclear spin-spin couplings 1)J(X-H and 2)J(H-H and nuclear magnetic shieldings sigma(X) and sigma(H) for the group-15 and -16 hydrides are presented. Relativistic calculations were performed with Dirac-Fock wave functions and the random phase approximation method. Results are compared to its nonrelativistic counterpart. Paramagnetic and diamagnetic contributions to the nuclear magnetic shielding constants are also reported. We found very large relativistic corrections to both properties in the sixth-row hydrides (BiH3 and PoH2). Our calculations of the relativistic corrections to the isotropic part of sigma at the heavy nucleus X show that it is roughly proportional to Z3.2 in both series of molecules. Paramagnetic term sigmap is more sensitive to the effects of relativity than the diamagnetic one sigmad, even though both have a behavior proportional to third power of the nuclear charge Z.

Gomez, Sergio S.; Romero, Rodolfo H.; Aucar, Gustavo A.

2002-11-01

124

Carbon-13 magnetic resonance spectroscopy of drugs III: penicillins.  

PubMed

The natural abundance 13C-NMR spectra of a series of penicillins (penicillin V methyl ester, penicillin V, penicillin G, methicillin, oxacillin, cloxacillin, and dicloxacillin) were studied. The chemical shifts were assigned using the pulse Fourier transform technique with the aid of long-range carbon-13 hydrogen coupling. The previous assignments of pencillin V methyl ester were revised. PMID:758467

Chang, C J; Hem, S L

1979-01-01

125

Stable Three-Axis Nuclear Spin Gyroscope in Diamond  

E-print Network

We propose a sensitive and stable three-axis gyroscope in diamond. We achieve high sensitivity by exploiting the long coherence time of the N14 nuclear spin associated with the Nitrogen-Vacancy center in diamond, and the efficient polarization and measurement of its electronic spin. While the gyroscope is based on a simple Ramsey interferometry scheme, we use coherent control of the quantum sensor to improve its coherence time as well as its robustness against long-time drifts, thus achieving a very robust device with a resolution of 0.5mdeg/s/(Hz mm^3)^(1/2). In addition, we exploit the four axes of delocalization of the Nitrogen-Vacancy center to measure not only the rate of rotation, but also its direction, thus obtaining a compact three-axis gyroscope.

Ajoy, Ashok

2012-01-01

126

Stable Three-Axis Nuclear Spin Gyroscope in Diamond  

E-print Network

We propose a sensitive and stable three-axis gyroscope in diamond. We achieve high sensitivity by exploiting the long coherence time of the N14 nuclear spin associated with the Nitrogen-Vacancy center in diamond, and the efficient polarization and measurement of its electronic spin. While the gyroscope is based on a simple Ramsey interferometry scheme, we use coherent control of the quantum sensor to improve its coherence time as well as its robustness against long-time drifts, thus achieving a very robust device with a resolution of 0.5mdeg/s/(Hz mm^3)^(1/2). In addition, we exploit the four axes of delocalization of the Nitrogen-Vacancy center to measure not only the rate of rotation, but also its direction, thus obtaining a compact three-axis gyroscope.

Ashok Ajoy; Paola Cappellaro

2012-05-07

127

Nuclear spin conversion of water inside fullerene cages detected by low-temperature nuclear magnetic resonance  

SciTech Connect

The water-endofullerene H{sub 2}O@C{sub 60} provides a unique chemical system in which freely rotating water molecules are confined inside homogeneous and symmetrical carbon cages. The spin conversion between the ortho and para species of the endohedral H{sub 2}O was studied in the solid phase by low-temperature nuclear magnetic resonance. The experimental data are consistent with a second-order kinetics, indicating a bimolecular spin conversion process. Numerical simulations suggest the simultaneous presence of a spin diffusion process allowing neighbouring ortho and para molecules to exchange their angular momenta. Cross-polarization experiments found no evidence that the spin conversion of the endohedral H{sub 2}O molecules is catalysed by {sup 13}C nuclei present in the cages.

Mamone, Salvatore, E-mail: s.mamone@soton.ac.uk; Concistrè, Maria; Carignani, Elisa; Meier, Benno; Krachmalnicoff, Andrea; Johannessen, Ole G.; Denning, Mark; Carravetta, Marina; Whitby, Richard J.; Levitt, Malcolm H., E-mail: mhl@soton.ac.uk [School of Chemistry, University of Southampton, Southampton SO17 1BJ (United Kingdom); Lei, Xuegong; Li, Yongjun [Department of Chemistry, Columbia University, New York, New York 10027 (United States)] [Department of Chemistry, Columbia University, New York, New York 10027 (United States); Goh, Kelvin; Horsewill, Anthony J. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)] [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

2014-05-21

128

Dynamics of the Measurement of Nuclear Spins in a Solid-State Quantum Computer  

Microsoft Academic Search

We study numerically the process of nuclear spin measurement in a solid-state\\u000aquantum computer of the type proposed by Kane by modeling the quantum dynamics\\u000aof two coupled nuclear spins on $^{31}$P donors implanted in silicon. We\\u000aestimate the minimum measurement time necessary for the reliable transfer of\\u000aquantum information from the nuclear spin subsystem to the electronic\\u000asubsystem. We

Gennady P. Berman; David K. Campbell; Gary D. Doolen; Kirill E. Nagaev

1999-01-01

129

Electron-Nuclear Spin Dynamics in a Mesoscopic Solid-State Quantum Computer  

SciTech Connect

We numerically simulate the process of nuclear spin measurement in Kane's quantum computer. For this purpose, we model the quantum dynamics of two coupled nuclear spins located on {sup 31}P donors implanted in Si. We estimate the minimum time of measurement necessary for the reliable transfer of quantum information from the nuclear spin subsystem to the electronic one and the probability of error for typical values of external noise.

Berman, G.P.; Campbell, D.K.; Doolen, G.D.; Nagaev, K.E.

1998-12-07

130

Nuclear spin-spin coupling in a van der Waals-bonded system: xenon dimer.  

PubMed

Nuclear spin-spin coupling over van der Waals bond has recently been observed via the frequency shift of solute protons in a solution containing optically hyperpolarized (129)Xe nuclei. We carry out a first-principles computational study of the prototypic van der Waals-bonded xenon dimer, where the spin-spin coupling between two magnetically non-equivalent isotopes, J((129)Xe - (131)Xe), is observable. We use relativistic theory at the four-component Dirac-Hartree-Fock and Dirac-density-functional theory levels using novel completeness-optimized Gaussian basis sets and choosing the functional based on a comparison with correlated ab initio methods at the nonrelativistic level. J-coupling curves are provided at different levels of theory as functions of the internuclear distance in the xenon dimer, demonstrating cross-coupling effects between relativity and electron correlation for this property. Calculations on small Xe clusters are used to estimate the importance of many-atom effects on J((129)Xe - (131)Xe). Possibilities of observing J((129)Xe - (131)Xe) in liquid xenon are critically examined, based on molecular dynamics simulation. A simplistic spherical model is set up for the xenon dimer confined in a cavity, such as in microporous materials. It is shown that the on the average shorter internuclear distance enforced by the confinement increases the magnitude of the coupling as compared to the bulk liquid case, rendering J((129)Xe - (131)Xe) in a cavity a feasible target for experimental investigation. PMID:23514495

Vaara, Juha; Hanni, Matti; Jokisaari, Jukka

2013-03-14

131

Radioactive nuclear beams and the North American IsoSpin Laboratory (ISL) initiative  

SciTech Connect

Radioactive nuclear beams (RNBs) offer exciting new research opportunities in fields as diverse as nuclear structure, nuclear reactions, astrophysics atomic, materials, and applied science. Their realization in new accelerator complexes also offers important technical challenges. Some of the nuclear physics possibilities afforded by RNBs, with emphasis on low spin nuclear structure, are discussed, accompanied by an outline of the ISL initiative and its status.

Casten, R.F.

1992-12-01

132

Radioactive nuclear beams and the North American IsoSpin Laboratory (ISL) initiative  

SciTech Connect

Radioactive nuclear beams (RNBs) offer exciting new research opportunities in fields as diverse as nuclear structure, nuclear reactions, astrophysics atomic, materials, and applied science. Their realization in new accelerator complexes also offers important technical challenges. Some of the nuclear physics possibilities afforded by RNBs, with emphasis on low spin nuclear structure, are discussed, accompanied by an outline of the ISL initiative and its status.

Casten, R.F.

1992-01-01

133

Spin-Wave Contribution to the Nuclear Spin-Lattice Relaxation in Triplet Superconductors Timofey Rostunov,1  

E-print Network

of hyperfine interactions between nuclear spins and conduction electrons, gN is a gyromagnetic ratio of the nucleus, geff is an effective gyromagnetic ratio of conducting electrons, B is a Bohr magneton, and 00 ?Hq

Demler, Eugene

134

Quantum state tomography for strongly coupled nuclear spin systems  

NASA Astrophysics Data System (ADS)

We perform quantum state tomography (QST) in a three-qubit system consisting of strongly coupled nuclear spins, known in the NMR literature as A B X systems. We find that the number of experiments necessary to perform QST in such systems can be reduced with respect to those containing three qubits weakly coupled, which reduces the experimental effort required for the complete density-matrix reconstruction. To test the procedure we implement the full protocol for quantum teleportation. The tomographic results demonstrate that the density matrix can be reconstructed with fewer operations and high fidelity.

Vind, Fatemeh Anvari; Souza, A. M.; Sarthour, R. S.; Oliveira, I. S.

2014-12-01

135

NMR response of nuclear-spin helix in quantum wires with hyperfine and spin-orbit interaction  

NASA Astrophysics Data System (ADS)

We calculate the nuclear magnetic resonance (NMR) response of a quantum wire where at low temperature a self-sustained electron-nuclear spin order is created. Our model includes the electron mediated Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange, electron spin-orbit interactions, nuclear dipolar interactions, and the static and oscillating NMR fields, all of which play an essential role. The paramagnet to helimagnet transition in the nuclear system is reflected in an unusual response: it absorbs at a frequency given by the internal RKKY exchange field, rather than the external static field, whereas the latter leads to a splitting of the resonance peak.

Stano, Peter; Loss, Daniel

2014-11-01

136

Dynamical decoupling design for identifying weakly coupled nuclear spins in a bath  

NASA Astrophysics Data System (ADS)

Identifying weakly coupled nuclear spins around single electron spins is a key step toward implementing quantum information processing using coupled electron-nuclei spin systems or sensing like single-spin nuclear magnetic resonance detection using diamond defect spins. Dynamical decoupling control of the center electron spin with periodic pulse sequences [e.g., the Carre-Purcell-Meiboom-Gill (CPMG) sequence] has been successfully used to identify single nuclear spins and to resolve structure of nuclear spin clusters. Here, we design a type of pulse sequence by replacing the repetition unit (a single ? pulse) of the CPMG sequence with a group of nonuniformly spaced ? pulses. Using the nitrogen-vacancy center system in diamond, we theoretically demonstrate that the designed pulse sequence improves the resolution of nuclear spin noise spectroscopy, and more information about the surrounding nuclear spins is extracted. The principle of dynamical decoupling design proposed in this paper is useful in many systems (e.g., defect spin qubit in solids, trapped ion, and superconducting qubit) for high-resolution noise spectroscopy.

Zhao, Nan; Wrachtrup, Jörg; Liu, Ren-Bao

2014-09-01

137

J-recoupling patterns arising from two chemically equivalent nuclear spins in magic-angle spinning spectra of solids  

NASA Astrophysics Data System (ADS)

A general description of magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectra arising from a pair of chemically equivalent nuclear spins is presented in terms of average Hamiltonian theory (AHT). In general, the MAS NMR spectra of such a spin-pair exhibit a spinning frequency dependent four-line pattern from which it is possible to extract the indirect spin-spin coupling constant, J, involving the ``equivalent'' spin pair. Explicit expressions for the spinning frequency dependence of the four-line pattern have been derived using AHT. In principle, correction terms to any order can be included; however, consideration of correction terms up to and including third order appear to be sufficient to interpret the most important features characteristic of J-recoupled spectra involving chemically equivalent spin pairs. The average Hamiltonian theory predicts three different general types of recoupling patterns. The type of recoupling pattern observed for a particular chemically equivalent spin pair is predicted to depend on the relative magnitudes of the indirect homonuclear coupling constant, J, the direct homonuclear dipolar coupling constant, R, the magnitude of the instantaneous chemical shift difference between the ``equivalent'' spins in frequency units, and the MAS spinning frequency. All reported examples of spinning frequency dependent MAS NMR spectra arising from a pair of chemically equivalent spins can be understood using the theoretical expressions derived here. As an example, we interpret the unusual J-recoupling pattern observed in 31P MAS NMR spectra of Hg(PPh3)2(NO3)2. The recoupling pattern is unusual in that 2J(P,P) is given by the separation of alternate lines in the four-line pattern. Similar unusual J-recoupling patterns were first reported by Eichele, Wu, and Wasylishen.

Wu, Gang; Wasylishen, Roderick E.

1993-04-01

138

Nuclear Spin Relaxation of Polycrystalline ^129Xe at Low Fields  

NASA Astrophysics Data System (ADS)

Through spin exchange techniques, it is possible to achieve upwards of 30% nuclear spin polarization in ^129Xe with an NMR signal enhancement of some 5 orders of magnitude over typical thermal signals. Hyperpolarized ^129Xe has thus found application in several leading-edge technologies. At 1 T and 4.2 K the characteristic relaxation time of enriched polycrystalline ^129Xe (86% ^129Xe, 0.1% ^131Xe) is well over 200 hours, sufficient for long-term storage and transport. At more convenient fields from 1 to 500 G, significant structure in relaxation times vs. magnetic field is seen; the most prominent being a sharp local maximum of 800 min at ? 4 G. Such structure has not been observed in previous measurements of natural Xe. Below 20 K, relaxation can be attributed either to cross relaxation with ^131Xe, mediated by spin diffusion (Gatzke, et al., PRL 70, 690 (1993)) or to paramagnetic impurities. We report measurements of ^129Xe relaxation as a function of magnetic field, temperature and Xe isotopic content and compare with expected theoretical behaviors.

Samuelson, G.; Su, T.; Saam, B.

2003-05-01

139

Nuclear Spin Orientation Dependence of Magnetoconductance: A New Method for Measuring the Spin of Charged Excitations in the QHE  

SciTech Connect

A new method for measuring the spin of the electrically charged ground state excitations m the Q$j~j quantum Hall effect ia proposed and demonstmted for the tirst time in GaAs/AIGaAs nndtiquantum wells. The method is &sed on the nuclear spin orientation dependence of" the 2D dc conductivity y in the quantum Hall regime due to the nuclear hyperfine interaction. As a demonstration of this method the spin of the electrically charged excitations of the ground state is determined at filling factor v = 1.

Bowers, C.R.; Reno, J.L.; Simmons, J.A.; Vitkalov, S.A.

1998-12-01

140

Interplay of spin-orbit and hyperfine interactions in dynamical nuclear polarization in semiconductor quantum dots  

NASA Astrophysics Data System (ADS)

We theoretically study the interplay of spin-orbit and hyperfine interactions in dynamical nuclear polarization in two-electron semiconductor double quantum dots near the singlet-triplet (S -T+ ) anticrossing. The goal of the scheme under study is to extend the singlet-triplet (S -T0 ) qubit decoherence time T2* by dynamically transferring the polarization from the electron spins to the nuclear spins. This polarization transfer is achieved by cycling the electron spins over the S -T+ anticrossing. Here, we investigate, both quantitatively and qualitatively, how this hyperfine-mediated dynamical polarization transfer is influenced by the Rashba and Dresselhaus spin-orbit interaction. In addition to T2*, we determine the singlet return probability Ps, a quantity that can be measured in experiments. Our results suggest that the spin-orbit interaction establishes a mechanism that can polarize the nuclear spins in the direction opposite to that of hyperfine-mediated nuclear spin polarization. In materials with relatively strong spin-orbit coupling, this interplay of spin-orbit and hyperfine-mediated nuclear spin polarizations prevents any notable increase in the S -T0 qubit decoherence time T2*.

Ran?i?, Marko J.; Burkard, Guido

2014-12-01

141

Experimental demonstration of a stimulated polarization wave in a chain of nuclear spins  

NASA Astrophysics Data System (ADS)

A stimulated wave of polarization, which implements a simple mechanism of quantum amplification, is experimentally demonstrated in a chain of four J-coupled nuclear spins, irradiated by a weak radio-frequency transverse field. The 'quantum domino' dynamics, a wave of flipped spins triggered by a flip of the first spin, has been observed in fully 13C-labelled sodium butyrate.

Lee, Jae-Seung; Adams, Travis; Khitrin, A. K.

2007-04-01

142

Anomalous-filling-factor-dependent nuclear-spin polarization in a 2D electron system.  

PubMed

Spin-related electronic phase transitions in the fractional quantum Hall regime are accompanied by a large change in resistance. Combined with their sensitivity to spin orientation of nuclei residing in the same plane as the 2D electrons, they offer a convenient electrical probe to carry out nuclear magnetometry. Despite conditions which should allow both electronic and nuclear-spin subsystems to approach thermodynamic equilibrium, we uncover for the nuclei a remarkable and strongly electronic filling-factor-dependent deviation from the anticipated thermal nuclear-spin polarization. PMID:14995804

Smet, J H; Deutschmann, R A; Ertl, F; Wegschei der, W; Abstreiter, G; von Klitzing, K

2004-02-27

143

Optical pump-probe measurements of local nuclear spin coherence in semiconductor quantum wells.  

PubMed

We demonstrate local manipulation and detection of nuclear spin coherence in semiconductor quantum wells by an optical pump-probe technique combined with pulse rf NMR. The Larmor precession of photoexcited electron spins is monitored by time-resolved Kerr rotation (TRKR) as a measure of nuclear magnetic field. Under the irradiation of resonant pulsed rf magnetic fields, Rabi oscillations of nuclear spins are traced by TRKR signals. The intrinsic coherence time evaluated by a spin-echo technique reveals the dependence on the orientation of the magnetic field with respect to the crystalline axis as expected by the nearest neighbor dipole-dipole interaction. PMID:16606048

Sanada, H; Kondo, Y; Matsuzaka, S; Morita, K; Hu, C Y; Ohno, Y; Ohno, H

2006-02-17

144

Nuclear spin structure in dark matter search: The finite momentum transfer limit  

E-print Network

Spin-dependent elastic scattering of weakly interacting massive dark matter particles (WIMP) off nuclei is reviewed. All available, within different nuclear models, structure functions S(q) for finite momentum transfer (q>0) are presented. These functions describe the recoil energy dependence of the differential event rate due to the spin-dependent WIMP-nucleon interactions. This paper, together with the previous paper ``Nuclear spin structure in dark matter search: The zero momentum transfer limit'', completes our review of the nuclear spin structure calculations involved in the problem of direct dark matter search.

V. A. Bednyakov; F. Simkovic

2006-08-09

145

Coherent dynamics of coupled electron and nuclear spin qubits in diamond.  

PubMed

Understanding and controlling the complex environment of solid-state quantum bits is a central challenge in spintronics and quantum information science. Coherent manipulation of an individual electron spin associated with a nitrogen-vacancy center in diamond was used to gain insight into its local environment. We show that this environment is effectively separated into a set of individual proximal 13C nuclear spins, which are coupled coherently to the electron spin, and the remainder of the 13C nuclear spins, which cause the loss of coherence. The proximal nuclear spins can be addressed and coupled individually because of quantum back-action from the electron, which modifies their energy levels and magnetic moments, effectively distinguishing them from the rest of the nuclei. These results open the door to coherent manipulation of individual isolated nuclear spins in a solid-state environment even at room temperature. PMID:16973839

Childress, L; Gurudev Dutt, M V; Taylor, J M; Zibrov, A S; Jelezko, F; Wrachtrup, J; Hemmer, P R; Lukin, M D

2006-10-13

146

Dynamic Nuclear Polarization with Single Electron Spins J. R. Petta,1,2  

E-print Network

polarization driven by scattering between spin-polarized edge states induced hys- teresis in conductanceDynamic Nuclear Polarization with Single Electron Spins J. R. Petta,1,2 J. M. Taylor,1,3 A. C Barbara, California 93106, USA (Received 6 September 2007; published 11 February 2008) We polarize nuclear

Petta, Jason

147

Dynamics of nuclear spin measurement in a mesoscopic solid-state quantum computer  

Microsoft Academic Search

We study numerically the process of nuclear spin measurement in a solid-state quantum computer of the type proposed by Kane, by calculating the quantum dynamics of two coupled nuclear spins on 31 P donors implanted in 28 Si. We estimate the time of the `quantum swap operation' - the minimum measurement time required for the reliable transfer of quantum information

Gennady P. Berman; David K. Campbell; Gary D. Doolen; Kirill E. Nagaev

2000-01-01

148

Coherent control of two nuclear spins using the anisotropic hyperfine interaction  

E-print Network

We demonstrate coherent control of two nuclear spins mediated by the magnetic resonance of a hyperfine-coupled electron spin. This control is used to create a double nuclear coherence in one of the two electron spin manifolds, starting from an initial thermal state, in direct analogy to the creation of an entangled (Bell) state from an initially pure unentangled state. We identify challenges and potential solutions to obtaining experimental gate fidelities useful for quantum information processing in this type of system.

Yingjie Zhang; Colm A. Ryan; Raymond Laflamme; Jonathan Baugh

2011-09-02

149

High-fidelity readout and control of a nuclear spin qubit in silicon.  

PubMed

Detection of nuclear spin precession is critical for a wide range of scientific techniques that have applications in diverse fields including analytical chemistry, materials science, medicine and biology. Fundamentally, it is possible because of the extreme isolation of nuclear spins from their environment. This isolation also makes single nuclear spins desirable for quantum-information processing, as shown by pioneering studies on nitrogen-vacancy centres in diamond. The nuclear spin of a (31)P donor in silicon is very promising as a quantum bit: bulk measurements indicate that it has excellent coherence times and silicon is the dominant material in the microelectronics industry. Here we demonstrate electrical detection and coherent manipulation of a single (31)P nuclear spin qubit with sufficiently high fidelities for fault-tolerant quantum computing. By integrating single-shot readout of the electron spin with on-chip electron spin resonance, we demonstrate quantum non-demolition and electrical single-shot readout of the nuclear spin with a readout fidelity higher than 99.8 percent-the highest so far reported for any solid-state qubit. The single nuclear spin is then operated as a qubit by applying coherent radio-frequency pulses. For an ionized (31)P donor, we find a nuclear spin coherence time of 60 milliseconds and a one-qubit gate control fidelity exceeding 98 percent. These results demonstrate that the dominant technology of modern electronics can be adapted to host a complete electrical measurement and control platform for nuclear-spin-based quantum-information processing. PMID:23598342

Pla, Jarryd J; Tan, Kuan Y; Dehollain, Juan P; Lim, Wee H; Morton, John J L; Zwanenburg, Floris A; Jamieson, David N; Dzurak, Andrew S; Morello, Andrea

2013-04-18

150

A 3D-Printed High Power Nuclear Spin Polarizer  

PubMed Central

Three-dimensional printing with high-temperature plastic is used to enable spin exchange optical pumping (SEOP) and hyperpolarization of xenon-129 gas. The use of 3D printed structures increases the simplicity of integration of the following key components with a variable temperature SEOP probe: (i) in situ NMR circuit operating at 84 kHz (Larmor frequencies of 129Xe and 1H nuclear spins), (ii) <0.3 nm narrowed 200 W laser source, (iii) in situ high-resolution near-IR spectroscopy, (iv) thermoelectric temperature control, (v) retroreflection optics, and (vi) optomechanical alignment system. The rapid prototyping endowed by 3D printing dramatically reduces production time and expenses while allowing reproducibility and integration of “off-the-shelf” components and enables the concept of printing on demand. The utility of this SEOP setup is demonstrated here to obtain near-unity 129Xe polarization values in a 0.5 L optical pumping cell, including ~74 ± 7% at 1000 Torr xenon partial pressure, a record value at such high Xe density. Values for the 129Xe polarization exponential build-up rate [(3.63 ± 0.15) × 10?2 min?1] and in-cell 129Xe spin?lattice relaxation time (T1 = 2.19 ± 0.06 h) for 1000 Torr Xe were in excellent agreement with the ratio of the gas-phase polarizations for 129Xe and Rb (PRb ~ 96%). Hyperpolarization-enhanced 129Xe gas imaging was demonstrated with a spherical phantom following automated gas transfer from the polarizer. Taken together, these results support the development of a wide range of chemical, biochemical, material science, and biomedical applications. PMID:24400919

Nikolaou, Panayiotis; Coffey, Aaron M.; Walkup, Laura L.; Gust, Brogan M.; LaPierre, Cristen D.; Koehnemann, Edward; Barlow, Michael J.; Rosen, Matthew S.; Goodson, Boyd M.; Chekmenev, Eduard Y.

2015-01-01

151

Spin-dependent modes in nuclei and nuclear forces  

NASA Astrophysics Data System (ADS)

Spin-dependent modes in nuclei are studied and important roles of tensor and three-body forces on nuclear structure are discussed. New shell model Hamiltonians, which have proper tensor components, are shown to explain spin properties of both stable and exotic nuclei. Gamow-Teller (GT) strengths in Ni isotopes, especially in 56Ni, are found to be well described by pf-shell Hamiltonian GXPF1J, which leads to a remarkable improvement in the evaluation of electron capture rates in stellar environmnets. GT strength in 40Ar obtained with VMU (monopole-based universal interaction) is found to be consistent with the experimental strength, and neutrino capture reaction cross sections for solar neutrinos from 8B are found to be enhanced compared with previous calculations. The repulsive monopole corrections to the microscopic two-body interactions in isospin T=1 channel are important for the proper shell evolutions in neutron-rich isotopes. The three-body force, in particular the Fujita-Miyazawa force induced by ? excitations, is pointed out to be responsible for the repulsive corrections among the valence neutrons. The important roles of the three-body force on the energies of exotic calcium isotopes as well as on the closed-shell nature of 48Ca and M1 transition in 48Ca are demonstrated.

Suzuki, Toshio; Otsuka, Takaharu; Honma, Michio

2012-10-01

152

Frequency selective detection of nuclear quadrupole resonance (NQR) spin echoes  

NASA Astrophysics Data System (ADS)

Nuclear Quadrupole Resonance (NQR) is a radio frequency (RF) technique that can be used to detect the presence of quadrupolar nuclei, such as the 14N nucleus prevalent in many explosives and narcotics. The technique has been hampered by low signal-to-noise ratios and is further aggravated by the presence of RF interference (RFI). To ensure accurate detection, proposed detectors should exploit the rich form of the NQR signal. Furthermore, the detectors should also be robust to any remaining residual interference, left after suitable RFI mitigation has been employed. In this paper, we propose a new NQR data model, particularly for the realistic case where multiple pulse sequences are used to generate trains of spin echoes. Furthermore, we refine two recently proposed approximative maximum likelihood (AML) detectors, enabling the algorithm to optimally exploit the data model of the entire echo train and also incorporate knowledge of the temperature dependent spin-echo decay time. The AML-based detectors ensure accurate detection and robustness against residual RFI, even when the temperature of the sample is not precisely known, by exploiting the dependencies of the NQR resonant lines on temperature. Further robustness against residual interference is gained as the proposed detector is frequency selective; exploiting only those regions of the spectrum where the NQR signal is expected. Extensive numerical evaluations based on both simulated and measured NQR data indicate that the proposed Frequency selective Echo Train AML (FETAML) detector offers a significant improvement as compared to other existing detectors.

Somasundaram, Samuel D.; Jakobsson, Andreas; Smith, John A. S.; Althoefer, Kaspar A.

2006-05-01

153

Dephasing and relaxation of central hole spins by nuclear spin baths in InGaAs quantum dots: role of nuclear quadrupolar coupling  

NASA Astrophysics Data System (ADS)

Single electron or hole spins in III-V semiconductor quantum dots (QDs) are promising candidates for solid-state qubits. Their coherence properties are typically governed by the hyperfine coupling between these ``central'' electronic spins and the dense surrounding bath of lattice nuclear spins. Theoretically this is a challenging problem due to its many-body and strongly-correlated nature. Here we measure the spin dynamics of holes in InGaAs quantum dots by detecting their intrinsic, random spin fluctuations while in thermal equilibrium, which reveals the spin correlation time scales ?h and the functional form of bath-induced spin relaxation. In zero magnetic field, ?h is very long (˜400 ns) and decays exponentially, in marked contrast with recent theories. ?h increases to ˜5 ?s in small (100 G) longitudinal fields, and the spin dynamics evolve to a very slow ˜1/ln(t) decay [1]. We model the influence of nuclear quadrupolar coupling on spin dynamics in these strained QDs for both electrons and holes [2], and find a good agreement with experimental data when the quadrupolar coupling exceeds the hyperfine coupling strength. [1] Yan Li, N. Sinitsyn, et al., PRL 108, 186603 (2012). [2] N. Sinitsyn, Yan Li, et al., PRL 109, 166605 (2012).

Li, Yan; Sinitsyn, N. A.; Saxena, A.; Smith, D. L.; Reuter, D.; Wieck, A. D.; Yakovlev, D. R.; Manfred, B.; Crooker, S. A.

2013-03-01

154

Nuclear magnetic double resonance based on strong rf magnetic-field-induced coupling between spin systems  

Microsoft Academic Search

The origin of the rf magnetic-field-induced coupling between spin systems is discussed. A new nuclear-double-resonance technique employing this coupling is proposed, which has particular value in measuring pure nuclear-quadrupole-resonance spectra of integer-spin nuclei by nuclear double resonance. The sensitivity of the new technique is discussed for the case of 1H-14N double resonance in zero static magnetic field, as well as

J. Seliger; R. Blinc; M. Mali; R. Osredkar; A. Prelesnik

1975-01-01

155

Atomic-Scale Nuclear Spin Imaging Using Quantum-Assisted Sensors in Diamond  

NASA Astrophysics Data System (ADS)

Nuclear spin imaging at the atomic level is essential for the understanding of fundamental biological phenomena and for applications such as drug discovery. The advent of novel nanoscale sensors promises to achieve the long-standing goal of single-protein, high spatial-resolution structure determination under ambient conditions. In particular, quantum sensors based on the spin-dependent photoluminescence of nitrogen-vacancy (NV) centers in diamond have recently been used to detect nanoscale ensembles of external nuclear spins. While NV sensitivity is approaching single-spin levels, extracting relevant information from a very complex structure is a further challenge since it requires not only the ability to sense the magnetic field of an isolated nuclear spin but also to achieve atomic-scale spatial resolution. Here, we propose a method that, by exploiting the coupling of the NV center to an intrinsic quantum memory associated with the nitrogen nuclear spin, can reach a tenfold improvement in spatial resolution, down to atomic scales. The spatial resolution enhancement is achieved through coherent control of the sensor spin, which creates a dynamic frequency filter selecting only a few nuclear spins at a time. We propose and analyze a protocol that would allow not only sensing individual spins in a complex biomolecule, but also unraveling couplings among them, thus elucidating local characteristics of the molecule structure.

Ajoy, A.; Bissbort, U.; Lukin, M. D.; Walsworth, R. L.; Cappellaro, P.

2015-01-01

156

Atomic-scale nuclear spin imaging using quantum-assisted sensors in diamond  

E-print Network

Nuclear spin imaging at the atomic level is essential for the understanding of fundamental biological phenomena and for applications such as drug discovery. The advent of novel nano-scale sensors has given hope of achieving the long-standing goal of single-protein, high spatial-resolution structure determination in their natural environment and ambient conditions. In particular, quantum sensors based on the spin-dependent photoluminescence of Nitrogen Vacancy (NV) centers in diamond have recently been used to detect nanoscale ensembles of external nuclear spins. While NV sensitivity is approaching single-spin levels, extracting relevant information from a very complex structure is a further challenge, since it requires not only the ability to sense the magnetic field of an isolated nuclear spin, but also to achieve atomic-scale spatial resolution. Here we propose a method that, by exploiting the coupling of the NV center to an intrinsic quantum memory associated with the Nitrogen nuclear spin, can reach a tenfold improvement in spatial resolution, down to atomic scales. The spatial resolution enhancement is achieved through coherent control of the sensor spin, which creates a dynamic frequency filter selecting only a few nuclear spins at a time. We propose and analyze a protocol that would allow not only sensing individual spins in a complex biomolecule, but also unraveling couplings among them, thus elucidating local characteristics of the molecule structure.

Ashok Ajoy; Ulf Bissbort; Mikhail D. Lukin; Ronald L. Walsworth; Paola Cappellaro

2014-07-11

157

High-fidelity readout and control of a nuclear spin qubit in silicon  

E-print Network

A single nuclear spin holds the promise of being a long-lived quantum bit or quantum memory, with the high fidelities required for fault-tolerant quantum computing. We show here that such promise could be fulfilled by a single phosphorus (31P) nuclear spin in a silicon nanostructure. By integrating single-shot readout of the electron spin with on-chip electron spin resonance, we demonstrate the quantum non-demolition, electrical single-shot readout of the nuclear spin, with readout fidelity better than 99.8% - the highest for any solid-state qubit. The single nuclear spin is then operated as a qubit by applying coherent radiofrequency (RF) pulses. For an ionized 31P donor we find a nuclear spin coherence time of 60 ms and a 1-qubit gate control fidelity exceeding 98%. These results demonstrate that the dominant technology of modern electronics can be adapted to host a complete electrical measurement and control platform for nuclear spin-based quantum information processing.

Jarryd J. Pla; Kuan Y. Tan; Juan P. Dehollain; Wee H. Lim; John J. L. Morton; Floris A. Zwanenburg; David N. Jamieson; Andrew S. Dzurak; Andrea Morello

2013-02-01

158

Energy levels and decoherence properties of single electron and nuclear spins in a defect center in diamond  

E-print Network

The coherent behavior of the single electron and single nuclear spins of a defect center in diamond and a 13C nucleus in its vicinity, respectively, are investigated. The energy levels associated with the hyperfine coupling of the electron spin of the defect center to the 13C nuclear spin are analyzed. Methods of magnetic resonance together with optical readout of single defect centers have been applied in order to observe the coherent dynamics of the electron and nuclear spins. Long coherence times, in the order of microseconds for electron spins and tens of microseconds for nuclear spins, recommend the studied system as a good experimental approach for implementing a 2-qubit gate.

I. Popa; T. Gaebel; M. Domhan; C. Wittmann; F. Jelezko; J. Wrachtrup

2004-09-12

159

Investigation of the Leggett-Garg Inequality for Precessing Nuclear Spins  

NASA Astrophysics Data System (ADS)

We report experimental implementation of a protocol for testing the Leggett-Garg inequality (LGI) for nuclear spins precessing in an external magnetic field. The implementation involves certain controlled operations, performed in parallel on pairs of spin-1/2 nuclei (target and probe) from molecules of a nuclear magnetic resonance ensemble, which enable evaluation of temporal correlations from an LG string. Our experiment demonstrates violation of the LGI for time intervals between successive measurements, over which the effects of relaxation on the quantum state of target spin are negligible. Further, it is observed that the temporal correlations decay, and the same target spin appears to display macrorealistic behavior consistent with LGI.

Athalye, Vikram; Roy, Soumya Singha; Mahesh, T. S.

2011-09-01

160

Recursive polarization of nuclear spins in diamond at arbitrary magnetic fields  

NASA Astrophysics Data System (ADS)

We introduce an alternate route to dynamically polarize the nuclear spin host of nitrogen-vacancy (NV) centers in diamond. Our approach articulates optical, microwave, and radio-frequency pulses to recursively transfer spin polarization from the NV electronic spin. Using two complementary variants of the same underlying principle, we demonstrate nitrogen nuclear spin initialization approaching 80% at room temperature both in ensemble and single NV centers. Unlike existing schemes, our approach does not rely on level anti-crossings and is thus applicable at arbitrary magnetic fields. This versatility should prove useful in applications ranging from nanoscale metrology to sensitivity-enhanced NMR.

Pagliero, Daniela; Laraoui, Abdelghani; Henshaw, Jacob D.; Meriles, Carlos A.

2014-12-01

161

Spin distribution in low-energy nuclear level schemes  

SciTech Connect

The spin-cutoff parameter {sigma} has been determined for experimental spin distributions at low excitation energies of 310 nuclei between {sup 18}F and {sup 251}Cf (more than 8000 levels with their spin). The results indicate a weak dependence on the mass number A of the spin-cutoff parameter {sigma}{sup 2}{approx}A{sup 0.28}, and an even-odd spin staggering in the spin distribution of the even-even nuclei, with a strong enhancement of the number of states with spin zero. A modification of the spin-cutoff distribution formula is proposed in order to describe the even-even nuclei data. These findings are in good agreement with recent predictions of shell-model Monte Carlo calculations.

Egidy, T. von [Physik-Department, Technische Universitaet Muenchen, D-85748 Garching (Germany); Bucurescu, D. [Horia Hulubei National Institute of Physics and Nuclear Engineering, R-76900 Bucharest (Romania)

2008-11-15

162

Conditional control of donor nuclear spins in silicon using stark shifts.  

PubMed

Electric fields can be used to tune donor spins in silicon using the Stark shift, whereby the donor electron wave function is displaced by an electric field, modifying the hyperfine coupling between the electron spin and the donor nuclear spin. We present a technique based on dynamic decoupling of the electron spin to accurately determine the Stark shift, and illustrate this using antimony donors in isotopically purified silicon-28. We then demonstrate two different methods to use a dc electric field combined with an applied resonant radio-frequency (rf) field to conditionally control donor nuclear spins. The first method combines an electric-field induced conditional phase gate with standard rf pulses, and the second one simply detunes the spins off resonance. Finally, we consider different strategies to reduce the effect of electric field inhomogeneities and obtain above 90% process fidelities. PMID:25375741

Wolfowicz, Gary; Urdampilleta, Matias; Thewalt, Mike L W; Riemann, Helge; Abrosimov, Nikolai V; Becker, Peter; Pohl, Hans-Joachim; Morton, John J L

2014-10-10

163

Extraordinarily slow nuclear spin relaxation in frozen laser-polarized 129Xe  

Microsoft Academic Search

We studied the very slow nuclear spin-lattice relaxation of solid 129Xe as a function of temperature and magnetic field using laser-polarized nuclei. Relaxation times in excess of 500 h were measured. We present evidence for a new relaxation mechanism which results from a Raman spin-phonon scattering process involving the spin-rotation interaction. We also establish the existence of cross relaxation between

M. Gatzke; G. D. Cates; B. Driehuys; D. Fox; W. Happer; B. Saam

1993-01-01

164

Cryogenic sample exchange NMR probe for magic angle spinning dynamic nuclear polarization  

E-print Network

We describe a cryogenic sample exchange system that dramatically improves the efficiency of magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments by reducing the time required to change samples and by ...

Barnes, Alexander B.

165

Infrared spectroscopy of chloromethyl radical in solid parahydrogen and its nuclear spin conversion.  

PubMed

We present high-resolution infrared absorption spectra of chloromethyl radical produced by in situ UV photolysis of chloroiodomethane isolated in solid parahydrogen. The radicals were stable over a few days in solid parahydrogen kept at 3.6 K. Analysis of the rotation-vibration spectra revealed that the radical exhibited quantized one-dimensional rotational motion about the C-Cl bond, while the ortho and para nuclear spin species were still clearly distinguishable in the spectra. Temporal change of the spectra indicated that the nuclear spin conversion between the ortho and para nuclear spin species of the radical in solid parahydrogen occurred in a time scale of a few hours at 3.6 K. It was also found that the nuclear spin conversion became significantly slower in a higher concentration of chloroiodomethane. PMID:23506119

Miyamoto, Yuki; Tsubouchi, Masaaki; Momose, Takamasa

2013-10-01

166

Nuclear-Spin Gyroscope Based on an Atomic Co-Magnetometer  

NASA Technical Reports Server (NTRS)

An experimental nuclear-spin gyroscope is based on an alkali-metal/noblegas co-magnetometer, which automatically cancels the effects of magnetic fields. Whereas the performances of prior nuclear-spin gyroscopes are limited by sensitivity to magnetic fields, this gyroscope is insensitive to magnetic fields and to other external perturbations. In addition, relative to prior nuclear-spin gyroscopes, this one exhibits greater sensitivity to rotation. There is commercial interest in development of small, highly sensitive gyroscopes. The present experimental device could be a prototype for development of nuclear spin gyroscopes suitable for navigation. In comparison with fiber-optic gyroscopes, these gyroscopes would draw less power and would be smaller, lighter, more sensitive, and less costly.

Romalis, Michael; Komack, Tom; Ghost, Rajat

2008-01-01

167

Atomic-Scale Nuclear Spin Imaging Using Quantum-Assisted Sensors in Diamond  

E-print Network

Nuclear spin imaging at the atomic level is essential for the understanding of fundamental biological phenomena and for applications such as drug discovery. The advent of novel nanoscale sensors promises to achieve the ...

Bissbort, U.

168

The determination of the in situ structure by nuclear spin contrast variation  

SciTech Connect

Polarized neutron scattering from polarized nuclear spins in hydrogenous substances opens a new way of contrast variation. The enhanced contrast due to proton spin polarization was used for the in situ structure determination of tRNA of the functional complex of the E.coli ribosome.

Stuhrmann, H.B. [GKSS Forschungszentrum, Geesthacht (Germany); Nierhaus, K.H. [Max-Planch-Institut fuer Molekulare Genetik, Berlin (Germany)

1994-12-31

169

Measurement of single electron and nuclear spin states based on optically detected magnetic resonance  

Microsoft Academic Search

A novel approach for measurement of single electron and nuclear spin states is suggested. Our approach is based on optically detected magnetic resonance in a nano-probe located at the apex of an AFM tip. The method provides single electron spin sensitivity with nano-scale spatial resolution.

Gennady P Berman; Alan R Bishop; Boris M Chernobrod; Marilyn E Hawley; Geoffrey W Brown; Vladimir I Tsifrinovich

2006-01-01

170

Transverse Relaxation of Cu Nuclear Spins in YBa2Cu3O6.98  

Microsoft Academic Search

We have measured the transverse relaxation of the planar Cu(2) nuclear spins in an oriented powder sample of YBa2Cu3O6.98 (Tc{=}92 K) by using the nuclear quadrupole resonance (NQR) technique. Above Tc, after subtraction of the Tl process, the spin echo envelope decay follows a Gaussian form, and its time constant is almost independent of temperature. In the vicinity of Tc,

Yutaka Itoh; Hiroshi Yasuoka; Yutaka Ueda

1990-01-01

171

Multi-scales nuclear spin relaxation of liquids in porous media  

Microsoft Academic Search

The magnetic field dependence of the nuclear spin–lattice relaxation rate 1\\/T1(?0) is a rich source of dynamical information for characterizing the molecular dynamics of liquids in confined environments. Varying the magnetic field changes the Larmor frequency ?0, and thus the fluctuations to which the nuclear spin relaxation is sensitive. Moreover, this method permits a more complete characterization of the dynamics

Jean-Pierre Korb

2010-01-01

172

Nuclear Spin Gyroscope Based on an Atomic Comagnetometer T. W. Kornack, R. K. Ghosh, and M. V. Romalis  

E-print Network

Nuclear Spin Gyroscope Based on an Atomic Comagnetometer T. W. Kornack, R. K. Ghosh, and M. V; published 29 November 2005) We describe a nuclear spin gyroscope based on an alkali their gyroscopic precession. Spin precession due to magnetic fields as well as their gradients and transients can

Romalis, Mike

173

Diagnostics of a spatial spin-modulated structure using nuclear magnetic resonance and Mössbauer spectroscopy  

NASA Astrophysics Data System (ADS)

Methods of the diagnostics of the spatial spin-modulated structure of the cycloidal type in multiferroics based on nuclear magnetic resonance and Mössbauer spectroscopy have been considered. It has been established that Mössbauer spectroscopy makes it possible to determine the anharmonicity parameter of the spatial spin-modulated structure of the cycloidal type with no worse accuracy than nuclear magnetic resonance with higher resolution. Mössbauer spectroscopy, being sensitive to the hyperfine quadrupole interaction of the nucleus in the excited state, makes it possible to obtain additional information on the features of the spatial spin-modulated structure.

Rusakov, V. S.; Pokatilov, V. S.; Sigov, A. S.; Matsnev, M. E.; Gubaidulina, T. V.

2014-12-01

174

Search for electric dipole moment in 129Xe atom using active nuclear spin maser  

NASA Astrophysics Data System (ADS)

An experimental search for an electric dipole moment in the diamagnetic atom 129Xe is in progress through the precision measurement of spin precession frequency using an active nuclear spin maser. A 3He comagnetometer has been incorporated into the active spin maser system in order to cancel out the long-term drifts in the external magnetic field. Also, a double-cell geometry has been adopted in order to suppress the frequency shifts due to interaction with polarized Rb atoms. The first EDM measurement with the 129Xe active spin maser and the 3He comagnetometer has been conducted.

Ichikawa, Y.; Chikamori, M.; Ohtomo, Y.; Hikota, E.; Sakamoto, Y.; Suzuki, T.; Bidinosti, C. P.; Inoue, T.; Furukawa, T.; Yoshimi, A.; Suzuki, K.; Nanao, T.; Miyatake, H.; Tsuchiya, M.; Yoshida, N.; Shirai, H.; Ino, T.; Ueno, H.; Matsuo, Y.; Fukuyama, T.; Asahi, K.

2014-03-01

175

Description of 158Er at Ultrahigh Spin in Nuclear Density Functional Theory  

SciTech Connect

Rotational bands in 158Er at ultrahigh spin have been studied in the framework of relativistic and nonrelativistic nuclear density-functional theories. Consistent results are obtained across the theoretical models used but some puzzles remain when confronted with experiment. Namely, the many-body configurations which provide good description of experimental transition quadrupole moments and dynamic moments of inertia require substantial increase of the spins of observed bands as compared with experimental estimates, which are still subject to large uncertainties. If, however, the theoretical spin assignments turned out to be correct, experimental band 1 in 158Er would be the highest spin structure ever observed.

Afanasjev, A. V. [Mississippi State University/JIHIR, ORNL; Shi, Yue [Peking University; Nazarewicz, Witold [UTK/ORNL/University of Warsaw

2012-01-01

176

Dynamical magnetic and nuclear polarization in complex spin systems: semi-magnetic II-VI quantum dots  

NASA Astrophysics Data System (ADS)

Dynamical magnetic and nuclear polarization in complex spin systems is discussed on the example of transfer of spin from exciton to the central spin of magnetic impurity in a quantum dot in the presence of a finite number of nuclear spins. The exciton is described in terms of electron and heavy-hole spins interacting via exchange interaction with magnetic impurity, via hyperfine interaction with a finite number of nuclear spins and via dipole interaction with photons. The time evolution of the exciton, magnetic impurity and nuclear spins is calculated exactly between quantum jumps corresponding to exciton radiative recombination. The collapse of the wavefunction and the refilling of the quantum dot with a new spin-polarized exciton is shown to lead to the build up of magnetization of the magnetic impurity as well as nuclear spin polarization. The competition between electron spin transfer to magnetic impurity and to nuclear spins simultaneous with the creation of dark excitons is elucidated. The technique presented here opens up the possibility of studying optically induced dynamical magnetic and nuclear polarization in complex spin systems.

Abolfath, Ramin M.; Trojnar, Anna; Roostaei, Bahman; Brabec, Thomas; Hawrylak, Pawel

2013-06-01

177

PUBLISHED ONLINE: 1 JULY 2012 | DOI: 10.1038/NPHYS2353 Ultrafast entangling gates between nuclear spins  

E-print Network

using SWAP operations3,6,18 , or incoherently using a family of dynamic nuclear 1Department of Materials nuclear spins using photoexcited triplet states Vasileia Filidou1 , Stephanie Simmons1 , Steven D. Karlen11,2 . Although nuclear spins are advantageous as quantum bits (qubits) because of their long

Loss, Daniel

178

Spin-asymmetry energy of nuclear matter Physik-Department T39, Technische Universitt Mnchen, D-85747 Garching, Germany  

E-print Network

Spin-asymmetry energy of nuclear matter N. Kaiser Physik-Department T39, Technische Universität the density-dependent spin-asymmetry energy S kf of isospin-symmetric nuclear matter in the three of freedom in the description of the nuclear many- body dynamics. The contributions to the energy per

Weise, Wolfram

179

Universal control and error correction in multi-qubit spin registers in diamond.  

PubMed

Quantum registers of nuclear spins coupled to electron spins of individual solid-state defects are a promising platform for quantum information processing. Pioneering experiments selected defects with favourably located nuclear spins with particularly strong hyperfine couplings. To progress towards large-scale applications, larger and deterministically available nuclear registers are highly desirable. Here, we realize universal control over multi-qubit spin registers by harnessing abundant weakly coupled nuclear spins. We use the electron spin of a nitrogen-vacancy centre in diamond to selectively initialize, control and read out carbon-13 spins in the surrounding spin bath and construct high-fidelity single- and two-qubit gates. We exploit these new capabilities to implement a three-qubit quantum-error-correction protocol and demonstrate the robustness of the encoded state against applied errors. These results transform weakly coupled nuclear spins from a source of decoherence into a reliable resource, paving the way towards extended quantum networks and surface-code quantum computing based on multi-qubit nodes. PMID:24487650

Taminiau, T H; Cramer, J; van der Sar, T; Dobrovitski, V V; Hanson, R

2014-03-01

180

Two-dimensional spatially selective spin inversion and spin-echo refocusing with a single nuclear magnetic resonance pulse  

NASA Astrophysics Data System (ADS)

A new class of nuclear magnetic resonance (NMR) pulses that provides simultaneous spatially selective inversion of nuclear spins in two dimensions following a single pulse application is described and demonstrated. The two-dimensional selective pulses consist of a single square- or amplitude-modulated ? rf pulse applied in the presence of an amplitude-modulated magnetic field gradient that reorients through the two dimensions during the rf pulse. For example, square and Gaussian rf pulses produce sharply peaked sombrero-, egg-carton-, and stalagmite-shaped profiles of spin inversion in the xz plane when applied in the presence of a gradient that rotates or describes a figure eight in the xz plane. The theoretical profiles, computed by numerical integration of the Bloch equation, are in good agreement with experimental results obtained by incorporating the pulses into a conventional NMR imaging sequence. The pulses are directly applicable to restricted field-of-view high-resolution imaging for the amelioration of aliasing signal artifacts, and when combined with one-dimensional localized phosphorus (31P) chemical shift spectroscopy techniques that employ surface detection coils, should permit complete three-dimensionally localized 31P NMR spectroscopy. The ? pulses provide similar two-dimensional spatial selectivity of the transverse nuclear magnetization when used for refocusing Hahn spin echoes.

Bottomley, Paul A.; Hardy, Christopher J.

1987-11-01

181

Solid-State Nuclear Spin Quantum Computer Based on Magnetic Resonance Force Microscopy  

E-print Network

We propose a nuclear spin quantum computer based on magnetic resonance force microscopy (MRFM). It is shown that an MRFM single-electron spin measurement provides three essential requirements for quantum computation in solids: (a) preparation of the ground state, (b) one- and two- qubit quantum logic gates, and (c) a measurement of the final state. The proposed quantum computer can operate at temperatures up to 1K.

G. P. Berman; G. D. Doolen; P. C. Hammel; V. I. Tsifrinovich

1999-09-09

182

Hahn-echo decay for exchange-coupled nuclear spins in solids.  

PubMed

In this paper we present a simple model to calculate the Hahn-echo decay of the exchange-coupled nuclear spins in solids. Satisfactory agreement between the calculated and experimentally observed echo decay of the exchange-coupled spins of T203l and T205l isotopes in thallium chloride TlCl and thallium tantalum sulfide TlTaS(3) is obtained. PMID:22463816

Sergeev, N A; Panich, A M

2012-01-01

183

Nuclear-Spin Selection Rules in the Chemistry of Interstellar Nitrogen Hydrides  

NASA Astrophysics Data System (ADS)

Nitrogen hydrides are at the root of the nitrogen chemistry in interstellar space. The detailed modeling of their gas phase formation, however, requires the knowledge of nuclear-spin branching ratios for chemical reactions involving multiprotonated species. We investigate in this work the nuclear-spin selection rules in both exothermic and near thermoneutral ion-molecule reactions involved in the synthesis of ammonia, assuming full scrambling of protons in the reaction complexes. The formalism of Oka [ J. Mol. Spectrosc. 2004, 228, 635 ] is employed for highly exothermic ion-molecule and dissociative recombination reactions. For thermoneutral reactions, a simple state-to-state statistical approach is suggested, which is in qualitative agreement with both quantum scattering and microcanonical statistical calculations. This model is applied to the seven atom reaction NH4+ + H2, of possible importance in the nuclear-spin thermalization of ammonia.

Rist, Claire; Faure, Alexandre; Hily-Blant, Pierre; Le Gal, Romane

2013-10-01

184

Nuclear-spin selection rules in the chemistry of interstellar nitrogen hydrides.  

PubMed

Nitrogen hydrides are at the root of the nitrogen chemistry in interstellar space. The detailed modeling of their gas phase formation, however, requires the knowledge of nuclear-spin branching ratios for chemical reactions involving multiprotonated species. We investigate in this work the nuclear-spin selection rules in both exothermic and near thermoneutral ion–molecule reactions involved in the synthesis of ammonia, assuming full scrambling of protons in the reaction complexes. The formalism of Oka [ J. Mol. Spectrosc. 2004, 228, 635] is employed for highly exothermic ion–molecule and dissociative recombination reactions. For thermoneutral reactions, a simple state-to-state statistical approach is suggested, which is in qualitative agreement with both quantum scattering and microcanonical statistical calculations. This model is applied to the seven atom reaction NH4(+) + H2, of possible importance in the nuclear-spin thermalization of ammonia. PMID:23461639

Rist, Claire; Faure, Alexandre; Hily-Blant, Pierre; Le Gal, Romane

2013-10-01

185

Perturbation of nuclear spin polarizations in solid state NMR of nitroxide-doped samples by magic-angle spinning without microwaves  

SciTech Connect

We report solid state {sup 13}C and {sup 1}H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, {sup 1}H and cross-polarized {sup 13}C NMR signals from {sup 15}N,{sup 13}C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T{sub 1e} is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations.

Thurber, Kent R., E-mail: thurberk@niddk.nih.gov; Tycko, Robert [Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520 (United States)] [Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520 (United States)

2014-05-14

186

Nuclear states and shapes at high spin. [Good review  

SciTech Connect

As angular momentum is added to a nucleus, the balance of forces acting upon it to determine its shape, moment of inertia, mode of rotation, and type of level structure may undergo a series of changes. At relatively low spins a deformed nucleus will rotate collectively, and one may see the effect of Coriolis antipairing in gradually increasing the moment of inertia. Around spin 12 to 16 h-bar there may be an abrupt change (backbending) when a pair of high-j nucleons unpairs and the nucleons align with the axis of rotation; this process allows the nucleus to slow its collective rotation. This process, the start of a sharing of angular momentum between single-particle motion and the collective rotation, gives a lower total energy and corresponds to a change toward triaxiality in the shape of the nucleus. At much higher spins discrete ..gamma..-ray transitions can no longer be observed. This is the regime of continuum spectra; all the information on these high-spin states (to 65 h-bar) is contained in these continuum cascades. Knowledge is accumulating on how to study these spectra, experimentally and theoretically, and new techniques offer promise of revealing a great deal of information about the shapes and properties of very high spin states. 71 references, 34 figures.

Diamond, R.M.

1980-08-01

187

Optical pumping of the electronic and nuclear spin of single charge-tunable quantum dots.  

PubMed

We present a comprehensive examination of optical pumping of spins in individual GaAs quantum dots as we change the net charge from positive to neutral to negative with a charge-tunable heterostructure. Negative photoluminescence polarization memory is enhanced by optical pumping of ground state electron spins, which we prove with the first measurements of the Hanle effect on an individual quantum dot. We use the Overhauser effect in a high longitudinal magnetic field to demonstrate efficient optical pumping of nuclear spins for all three charge states of the quantum dot. PMID:15783594

Bracker, A S; Stinaff, E A; Gammon, D; Ware, M E; Tischler, J G; Shabaev, A; Efros, Al L; Park, D; Gershoni, D; Korenev, V L; Merkulov, I A

2005-02-01

188

Interaction induced deformation in momentum distribution of spin polarized nuclear matter  

E-print Network

Effects of spin polarization on the structure of symmetric nuclear matter and pure neutron matter are investigated. We show that the spin polarization induces a deformation of the Fermi spheres for nucleons with spin parallel and opposite to the polarization axes. This feature can be related to the structure of the one pion exchange contribution to a realistic nucleon-nucleon interaction. While the anisotropies in the momentum distribution lower the energy of the system by small amount, the associated variations of the single particle energies with the angle between the polarization axis and the particle momentum are significant.

T. Frick; H. Müther; A. Sedrakian

2002-03-19

189

Effect of electron spin dynamics on solid-state dynamic nuclear polarization performance.  

PubMed

For the broadest dissemination of solid-state dynamic nuclear polarization (ssDNP) enhanced NMR as a material characterization tool, the ability to employ generic mono-nitroxide radicals as spin probes is critical. A better understanding of the factors contributing to ssDNP efficiency is needed to rationally optimize the experimental condition for the practically accessible spin probes at hand. This study seeks to advance the mechanistic understanding of ssDNP by examining the effect of electron spin dynamics on ssDNP performance at liquid helium temperatures (4-40 K). The key observation is that bi-radicals and mono-radicals can generate comparable nuclear spin polarization at 4 K and 7 T, which is in contrast to the observation for ssDNP at liquid nitrogen temperatures (80-150 K) that finds bi-radicals to clearly outperform mono-radicals. To rationalize this observation, we analyze the change in the DNP-induced nuclear spin polarization (Pn) and the characteristic ssDNP signal buildup time as a function of electron spin relaxation rates that are modulated by the mono- and bi-radical spin concentration. Changes in Pn are consistent with a systematic variation in the product of the electron spin-lattice relaxation time and the electron spin flip-flop rate that constitutes an integral saturation factor of an inhomogeneously broadened EPR spectrum. We show that the comparable Pn achieved with both radical species can be reconciled with a comparable integral EPR saturation factor. Surprisingly, the largest Pn is observed at an intermediate spin concentration for both mono- and bi-radicals. At the highest radical concentration, the stronger inter-electron spin dipolar coupling favors ssDNP, while oversaturation diminishes Pn, as experimentally verified by the observation of a maximum Pn at an intermediate, not the maximum, microwave (?w) power. At the maximum ?w power, oversaturation reduces the electron spin population differential that must be upheld between electron spins that span a frequency difference matching the (1)H NMR frequency-characteristic of the cross effect DNP. This new mechanistic insight allows us to rationalize experimental conditions where generic mono-nitroxide probes can offer competitive ssDNP performance to that of custom designed bi-radicals, and thus helps to vastly expand the application scope of ssDNP for the study of functional materials and solids. PMID:24968276

Siaw, Ting Ann; Fehr, Matthias; Lund, Alicia; Latimer, Allegra; Walker, Shamon A; Edwards, Devin T; Han, Song-I

2014-09-21

190

Simultaneous sub-second hyperpolarization of the nuclear and electron spins of phosphorus in silicon  

E-print Network

We demonstrate a method which can hyperpolarize both the electron and nuclear spins of 31P donors in Si at low field, where both would be essentially unpolarized in equilibrium. It is based on the selective ionization of donors in a specific hyperfine state by optically pumping donor bound exciton hyperfine transitions, which can be spectrally resolved in 28Si. Electron and nuclear polarizations of 90% and 76%, respectively, are obtained in less than a second, providing an initialization mechanism for qubits based on these spins, and enabling further ESR and NMR studies on dilute 31P in 28Si.

A. Yang; M. Steger; T. Sekiguchi; M. L. W. Thewalt; T. D. Ladd; K. M. Itoh; H. Riemann; N. V. Abrosimov; P. Becker; H. -J. Pohl

2009-08-12

191

Transverse Relaxation of Cu Nuclear Spins in YBa2Cu3O6.98  

NASA Astrophysics Data System (ADS)

We have measured the transverse relaxation of the planar Cu(2) nuclear spins in an oriented powder sample of YBa2Cu3O6.98 (Tc{=}92 K) by using the nuclear quadrupole resonance (NQR) technique. Above Tc, after subtraction of the Tl process, the spin echo envelope decay follows a Gaussian form, and its time constant is almost independent of temperature. In the vicinity of Tc, however, the Gaussian line shape is gradually narrowed. The calculated value (TG{=}149 ?sec) for the Gaussian time constant based on the direct nuclear dipole-dipole interaction is comparable to the experimental one (TG{=}131± 2 ?sec) at 297 K. Hence, the nuclear indirect coupling proposed previously may not be needed. Below Tc, the Gaussian line shape was found to be narrowed depending on Hl, and especially, it is sharply narrowed at 35 K and 87 K.

Itoh, Yutaka; Yasuoka, Hiroshi; Ueda, Yutaka

1990-10-01

192

Study of spin polarized nuclear matter and finite nuclei with finite range simple effective interaction  

E-print Network

The properties of spin polarized pure neutron matter and symmetric nuclear matter are studied using the finite range simple effective interaction, upon its parametrization revisited. Out of the total twelve parameters involved, we now determine ten of them from nuclear matter, against the nine parameters in our earlier calculation, as required in order to have predictions in both spin polarized nuclear matter and finite nuclei in unique manner being free from uncertainty found using the earlier parametrization. The information on the effective mass splitting in polarized neutron matter of the microscopic calculations is used to constrain the one more parameter, that was earlier determined from finite nucleus, and in doing so the quality of the description of finite nuclei is not compromised. The interaction with the new set of parameters is used to study the possibilities of ferromagnetic and antiferromagnetic transitions in completely polarized symmetric nuclear matter. Emphasis is given to analyze the resul...

Behera, B; Routray, T R; Centelles, M

2015-01-01

193

Interaction of Acoustic Phonons with Nuclear Spins in KTaO3  

Microsoft Academic Search

The nuclear spin resonance of 181Ta in a single crystal of KTaO3 has been studied using the technique of direct ultrasonic excitation. Nuclear resonances have been observed for transitions where Deltam=+\\/-1 and +\\/-2, where m is the magnetic quantum number. Longitudinal and both polarizations of transverse waves, set up along the [100] axis of the cubic crystal, were used to

E. H. Gregory

1968-01-01

194

Realization of quantum non-demolition measurement of nuclear spin 1\\/2 of cold ytterbium atom  

Microsoft Academic Search

We have demonstrated a quantum non-demolition (QND) measurement with a collective spin of cold ytterbium atoms (171Yb) via Faraday rotation interaction, and have observed 1.8-1.5+2.4 dB spin squeezing. Since 171Yb atoms have only a nuclear spin of one-half in the ground state, the system constitutes the simplest spin ensemble and is thus robust against decoherence. Furthermore, we have considered the

T. Takano; R. Namiki; Y. Takahashi

2009-01-01

195

Coherent storage of microwave excitations in rare-earth nuclear spins  

E-print Network

Interfacing between various elements of a computer - from memory to processors to long range communication - will be as critical for quantum computers as it is for classical computers today. Paramagnetic rare earth doped crystals, such as Nd$^{3+}$:Y$_2$SiO$_5$ (YSO), are excellent candidates for such a quantum interface: they are known to exhibit long optical coherence lifetimes (for communication via optical photons), possess a nuclear spin (memory) and have in addition an electron spin that can offer hybrid coupling with superconducting qubits (processing). Here we study two of these three elements, demonstrating coherent storage and retrieval between electron and $^{145}$Nd nuclear spin states in Nd$^{3+}$:YSO. We find nuclear spin coherence times can reach 9 ms at $\\approx 5$ K, about two orders of magnitude longer than the electron spin coherence, while quantum state and process tomography of the storage/retrieval operation reveal an average state fidelity of 0.86. The times and fidelities are expected to further improve at lower temperatures and with more homogeneous radio-frequency excitation.

Gary Wolfowicz; Hannes Maier-Flaig; Robert Marino; Alban Ferrier; Hervé Vezin; John J. L. Morton; Philippe Goldner

2014-12-23

196

Korringa-Like Nuclear Spin-Lattice Relaxation in a 2DES at ?= 1/2  

NASA Astrophysics Data System (ADS)

Via a resistively-detected NMR technique, the nuclear spin lattice relaxation time T1 of ^71Ga at low temperatures has been measured in a GaAs/AlGaAs heterostructure containing two weakly-coupled 2D electron systems (2DES), each at Landau level filling ?= 1/2. Incomplete electronic spin polarization, which has been reported previously [1,2] for low density 2DESs at ?= 1/2, should facilitate hyperfine- coupled nuclear spin relaxation owing to the presence of both electron spin states at the Fermi level. Within composite fermion theory, a Korringa law temperature dependence: T1T = constant, is expected for temperatures T<1 K. Our measurements made at temperatures in the range 35 mK nuclear spin relaxation mechanisms in this system.[1] I. V. Kukushkin, K. v. Klitzing, and K. Eberl. Phys. Rev. Lett. 82, 3665 (1999); A. E. Dementyev, et al., Phys. Rev. Lett. 83, 5074 (1999); S. Melinte, et al., Phys. Rev. Lett. 84, 354 (2000).[2] I.B. Spielman, L.A. Tracy, J.P. Eisenstein, L.N. Pfeiffer, K.W. West, condmat/0410092.This work was supported by the DOE, NSF, and NDSEG.

Tracy, L. A.; Pfeiffer, L. N.

2005-03-01

197

Role of dual nuclear baths on spin blockade leakage current bistabilities.  

PubMed

Spin-blockaded electronic transport across a double quantum dot (DQD) system represents an important advancement in the area of spin-based quantum information. The basic mechanism underlying the blockade is the formation of a blocking triplet state. The bistability of the leakage current as a function of the applied magnetic field in this regime is believed to arise from the effect of nuclear Overhauser fields on spin-flip transitions between the blocking triplet and the conducting singlet states. The objective of this paper is to present the nuances of considering a two bath model on the experimentally observed current bistability by employing a self consistent simulation of the nuclear spin dynamics coupled with the electronic transport of the DQD set up. In doing so, we first discuss the important subtleties involved in the microscopic derivation of the hyperfine mediated spin flip rates. We then give insights as to how the differences between the two nuclear baths and the resulting difference Overhauser field affect the two-electron states of the DQD and their connection with the experimentally observed current hysteresis curve. PMID:25374371

Buddhiraju, Siddharth; Muralidharan, Bhaskaran

2014-12-01

198

Indirect detection of nuclear spins of low gyromagnetic ratio coupled to spins of high gyromagnetic ratio  

SciTech Connect

In a heteronuclear system, the indirect detection of nuclei S, of weak gyromagnetic ratio, coupled to nuclei I, of strong gyromagnetic ratio, is accomplished by generation of zero and double quantum coherence between the I and S spin systems, during a preparatory period, TP. The zero and double quantum transitions are then interchanged at the midpoint of the evolution period, T1, producing an echo modulated only by S and I-I interactions at the end of the period T1, at which time the zero and double quantum coherence is then converted to I spin single quantum coherence yielding a free induction decay wave form S(T2) for given T1. The period, T1, is then varied to obtain a two-dimensional function S(T1, T2) which is then fully transformed to the frequency domain obtaining S(..omega..1,..omega..2) whereby the chemical shift of the coupled S spin is obtained along the ..omega..1 axis and the chemical shift of the I spin is obtained along the ..omega..2 axis.

Muller, L.

1980-12-09

199

The nuclear spin-isospin response to quasifree nucleon scattering  

SciTech Connect

The Neutron-Time-of-Flight (NTOF) facility at LAMPF has been used to measure complete sets of polarization-transfer coefficients for quasifree ({rvec p},{rvec n}) scattering from {sup 2}H, {sup 12}C, and {sup 40}Ca at 494 MeV and scattering angles of 12.5{degrees}, 18{degrees}, and 27{degrees} (q = 1.2, 1.7, 2.5 fm{sup {minus}1}). These measurements yield separated transverse ({sigma} {times} q) and longitudinal ({sigma}{center_dot}q) isovector spin responses. Comparison of the separated responses to calculations and to electron-scattering responses reveals a strong enhancement in the spin transverse channel. This excess transverse strength masks the effect of pionic correlations in the response ratio.

Taddeucci, T.N.

1995-12-31

200

Nuclear Spin Relaxation Characteristic of Submonolayer He Films in Nanochannels  

NASA Astrophysics Data System (ADS)

In order to obtain information on dynamics of helium films in the nondegenerate fluid region, we have performed a pulsed-NMR experiment at 3.29 MHz on He films adsorbed in straight 2.4 nm channels of FSM silicates down to 0.54 K. In general, the spin-lattice and spin-spin relaxation times and were explained in terms of the two-dimensional Bloembergen-Purcell-Pound model for dipolar relaxation. Temperature dependences of in submonolayer He films show a minimum, indicating that the dipolar-field correlation time is about s. The temperature of the minimum monotonically lowers with increasing coverage, suggesting that He adatoms become more mobile at higher coverages. The low-dimensional property of He adatoms is observed as the separation of and above where . On the other hand, several features specific to films in the nanochannel geometry were also found. Especially, the temperature dependence of becomes very small just below and shows a shoulder at lower temperatures. This anomaly has not been observed in He adsorbed in wider pores or on flat surfaces, so that it is considered to be characteristic of He films confined in narrow channels with a diameter of a few nm.

Matsushita, Taku; Kawai, Ryosuke; Kuze, Atsushi; Hieda, Mitsunori; Wada, Nobuo

2014-04-01

201

RESONANCE RELAXAT/ON DANS LES ISOLANTS NUCLEAR RELAXATION, SPIN ECHO  

E-print Network

of the nuclear echo signal (hl)was observed, when microwave pulse with the power more than spin-wave threshold was applied at any time between the first radio pulse and the signal echo (Fig. 1). If the pair of 900 radio-pulse. Such behaviour of the echo signal intensity can be explaned supposing existenceof

Boyer, Edmond

202

Coherent transfer of nuclear spin polarization in field-cycling NMR experiments  

SciTech Connect

Coherent polarization transfer effects in a coupled spin network have been studied over a wide field range. The transfer mechanism is based on exciting zero-quantum coherences between the nuclear spin states by means of non-adiabatic field jump from high to low magnetic field. Subsequent evolution of these coherences enables conversion of spin order in the system, which is monitored after field jump back to high field. Such processes are most efficient when the spin system passes through an avoided level crossing during the field variation. The polarization transfer effects have been demonstrated for N-acetyl histidine, which has five scalar coupled protons; the initial spin order has been prepared by applying RF-pulses at high magnetic field. The observed oscillatory transfer kinetics is taken as a clear indication of a coherent mechanism; level crossing effects have also been demonstrated. The experimental data are in very good agreement with the theoretical model of coherent polarization transfer. The method suggested is also valid for other types of initial polarization in the spin system, most notably, for spin hyperpolarization.

Pravdivtsev, Andrey N.; Yurkovskaya, Alexandra V.; Ivanov, Konstantin L., E-mail: ivanov@tomo.nsc.ru [International Tomography Center, Siberian Branch of the Russian Academy of Science, Institutskaya 3a, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Pirogova 2, Novosibirsk 630090 (Russian Federation); Vieth, Hans-Martin [Institut für Experimental Physik, Freie Universität Berlin, Arnimallee 14, Berlin 14195 (Germany)] [Institut für Experimental Physik, Freie Universität Berlin, Arnimallee 14, Berlin 14195 (Germany)

2013-12-28

203

Nuclear orientation of radon isotopes by spin-exchange optical pumping  

SciTech Connect

This paper reports the first demonstration of nuclear orientation of radon atoms. The method employed was spin exchange with potassium atoms polarized by optical pumping. The radon isotopes were produced at the ISOLDE isotope separator of CERN. The nuclear alignment of /sup 209/Rn and /sup 223/Rn has been measured by observation of ..gamma..-ray anisotropies and the magnetic dipole moment for /sup 209/Rn has been measured by the nuclear-magnetic-resonance method to be chemically bond..mu..chemically bond = 0.838 81(39)..mu../sub N/.

Kitano, M.; Calaprice, F.P.; Pitt, M.L.; Clayhold, J.; Happer, W.; Kadar-Kallen, M.; Musolf, M.; Ulm, G.; Wendt, K.; Chupp, T.

1988-05-23

204

Experimental and computational techniques in carbon-13 NMR  

NASA Astrophysics Data System (ADS)

An efficient method for calculating NMR lineshapes from anisotropic second rank tensor interactions is presented. The algorithm produces lineshapes from asymmetric tensors by summing those from symmetric tensors. This approach significantly reduces the calculation time, greatly facilitating iterative nonlinear least squares fitting of experimental spectra. This algorithm has been modified to produce partially relaxed lineshapes and spectra of partially ordered samples. Calculations for rapidly spinning samples show that spin-lattice relaxation time ( T1Z ) anisotropy varies with the angle between the spinning axis and the external field. When the rate of molecular motion is in the extreme narrowing limit, measurement of T1Z anisotropies for two different values of the spinning angle allows the determination of two linear combinations of the three static spectral densities, J0(0), J1(0) and J2(0). Experimental results for ferrocene demonstrate the utility of these linear combinations in the investigation of molecular dynamics with natural abundance 13C NMR. For ferrocene-d 10, deuteron T1Z and quadrupolar order relaxation time ( T1Q ) anisotropies, along with the relaxation time of the 13C magic angle spinning (MAS) peak, provide sufficient information to determine the orientation dependence of all three individual spectral densities. The experimental results include the first determination of J 0(0) in a solid sample. A variety of experimental techniques were used in an investigation of the polyimides LaRC-IA, LaRC-TPI and LaRC-SI and related model compounds. Magic angle spinning was used to acquire 13C isotropic chemical shift spectra of these materials. The spectra were assigned as completely as possible. In addition, the principal components of some shielding tensors were measured using variable angle correlation spectroscopy. Of those studied, LaRC-SI is the only polymer that is soluble. However, after it is heated past its glass transition temperature, LaRC-SI becomes insoluble. Experiments were performed in an attempt to identify causes of this behavior. 1H and 13C NMR spectra of soluble and insoluble LaRC-SI are significantly different when magnetization from nuclei in rigid regions of the polymer is suppressed. Hydration studies of LaRC-SI and LaRC-IA show that absorbed water plasticizes these polymers.

Varner, Samuel John

205

Preserving hyperpolarised nuclear spin order to study cancer metabolism  

E-print Network

: Gyromagnetic ratio of the nucleus of interest (in rad/Ts) • ?: Chemical shift of the nucleus of interest (in ppm) • B0: Magnetic field strength (in Tesla) xii LIST OF MAIN ABBREVIATIONS • ?0: Larmor frequency of the nucleus of interest (in rad/s); ?0 = ??B0 • I... concepts The magnetic moment, ~µ, indicates that a particle can interact with an external magnetic field and is defined as the product of the gyromagnetic ratio of the isotope, ?, with its spin: ~µ = ?~I. (1.1) The gyromagnetic ratio can be either positive...

Marco-Rius, Irene

2014-06-10

206

Model for optically-induced nuclear spin polarization in gallium arsenide  

NASA Astrophysics Data System (ADS)

New technologies and corresponding research fields have recently emerged that aim to develop solid-state devices based on large polarizations of electron and/or nuclear spins. These include spin-based strategies for parallel information processing through quantum entanglement ("quantum computing") and semi-classical electronic devices controlled via the spin degree of freedom ("spintronics"). A new rule of thumb - polarization has application - makes the optically pumped semiconductor an interesting system, as it exhibits both large electron and nuclear polarizations. However, several aspects of the process by which nuclear polarization is generated through optical pumping were not understood prior to this thesis, even for the most well studied semiconductor, GaAs. These include the dependence of the nuclear polarization on laser power, irradiation time, and especially on photon energy, which exhibits a dramatic peak near 1.5 eV. This thesis presents a quantitative model for optical nuclear polarization in GaAs. The model makes predictions for all quantities observable in a hulk optically pumped NMR (OPNMR) spectrum: the OPNMR signal magnitude, the hyperfine shift of the NMR frequency, and the nuclear spin temperature. The model may help researchers to optimize experimental conditions for maximizing nuclear polarization in spintronics or quantum computing architectures. A clear correlation is shown between the OPNMR signal and the photoconductivity. A photoconductivity model is developed herein that accounts for the varying penetration depth of the light with photon energy and for the presence of band-to-band and band-to-defect recombination of charge carriers. The model's predictions agree well with the photoconductivity data. The photoconductivity model is then combined with a nuclear polarization model. The resulting picture for near-band-gap (1.495 eV ? by ? 1.6 eV) optical nuclear polarization is as follows. Optical absorption generates free, non-equilibrium electron spins, whose polarization depends on the light polarization. During their excited-state lifetime, these electrons may relax into shallow-donor-bound states, where they experience a strong hyperfine interaction and can cross-relax with nuclear spins. The nuclear polarization near shallow donor defects then evolves over space and time according to a diffusion equation that accounts for localized generation and loss. This model predicts the photon-energy dependence and laser-power dependence of the OPNMR signal very well. The peak at 1.5 eV is predicted to arise from an optimal balance between a high nuclear polarization and a large irradiation volume. Both theory and experiment exhibit a deviation from linear growth of OPNMR signal with laser power at high powers and an earlier onset of non-linear growth for higher photon energy. Finally, the model predicts a time-dependent hyperfine shift of the NMR frequency that fits the data with quantitative agreement. All free parameters within the model are constrained through the fitting of these various data sets. With this model, analytical expressions are derived for helicity asymmetries in OPNMR spectra. These asymmetries are related simply enough to electron spin parameters that they provide a methodology for extracting the initially-excited and steady-state electron spin polarizations from OPNMR spectra, allowing the dependence of these polarizations on temperature and photon-energy to be investigated herein. The OPNMR asymmetry is furthermore used as a local thermometer of the irradiated volume, which provides experimental verification of a quantitative model for laser heating. Several unusual effects in optically pumped GaAs are characterized. Perhaps the most dramatic is a bi-exponential decay of the photoconductivity with irradiation time, observed at all near-band-gap photon energies. This serves as clear evidence of photoquenching of the deep defect known as EL2 under the conditions typical of OPNMR measurements. Further experiments are suggested to complete the studies in this

Coles, Patrick Joseph

207

Experimental demonstration of stimulated polarization wave in a chain of nuclear spins  

NASA Astrophysics Data System (ADS)

A one-dimensional Ising chain irradiated by weak resonant transverse field is the simplest model of quantum amplifier [Phys. Rev. A 71, 062338 (2005)]. The quantum state of the chain is stationary when all the qubits (spins) are in the same state. However, when the first qubit is flipped, it triggers a stimulated wave of flipped qubits, propagating through the chain. Such ``quantum domino" dynamics induces huge change in the total polarization, a macroscopic observable. Here we present the experimental demonstration of this quantum amplification process on a four-qubit system by using nuclear magnetic resonance technique. The physical system is a linear chain of four ^13C nuclear spins in a molecule of fully ^ 13C-labeled sodium butyrate dissolved in D2O. The pseudopure ground state (with all spins up) is prepared by multi-frequency partial saturation. The wave of flipped spins has been clearly observed when the first spin of the chain is flipped. We define a coefficient of amplification as the relative enhancement of the total polarization change. In our experimental system, the measured coefficient of amplification is about 3.

Lee, Jae-Seung; Adams, Travis; Khitrin, Anatoly

2007-03-01

208

Rabi and Larmor nuclear quadrupole double resonance of spin-1 nuclei.  

PubMed

We demonstrate the creation of two novel double-resonance conditions between spin-1 and spin-1/2 nuclei in a crystalline solid. Using a magnetic field oscillating at the spin-1/2 Larmor frequency, the nuclear quadrupole resonance (NQR) frequency is matched to the Rabi or Rabi plus Larmor frequency, as opposed to the Larmor frequency as is conventionally done. We derive expressions for the cross-polarization rate for all three conditions in terms of the relevant secular dipolar Hamiltonian, and demonstrate with these expressions how to measure the strength of the heterogenous dipolar coupling using only low magnetic fields. In addition, the combination of different resonance conditions permits the measurement of the spin-1/2 angular momentum vector using spin-1 NQR, opening up an alternate modality for the monitoring of low-field nuclear magnetic resonance. We use ammonium nitrate to explore these resonance conditions, and furthermore use the oscillating field to increase the signal-to-noise ratio per time by a factor of 3.5 for NQR detection of this substance. PMID:23231223

Prescott, D W; Malone, M W; Douglass, S P; Sauer, K L

2012-12-01

209

Rabi and Larmor nuclear quadrupole double resonance of spin-1 nuclei  

NASA Astrophysics Data System (ADS)

We demonstrate the creation of two novel double-resonance conditions between spin-1 and spin-1/2 nuclei in a crystalline solid. Using a magnetic field oscillating at the spin-1/2 Larmor frequency, the nuclear quadrupole resonance (NQR) frequency is matched to the Rabi or Rabi plus Larmor frequency, as opposed to the Larmor frequency as is conventionally done. We derive expressions for the cross-polarization rate for all three conditions in terms of the relevant secular dipolar Hamiltonian, and demonstrate with these expressions how to measure the strength of the heterogenous dipolar coupling using only low magnetic fields. In addition, the combination of different resonance conditions permits the measurement of the spin-1/2 angular momentum vector using spin-1 NQR, opening up an alternate modality for the monitoring of low-field nuclear magnetic resonance. We use ammonium nitrate to explore these resonance conditions, and furthermore use the oscillating field to increase the signal-to-noise ratio per time by a factor of 3.5 for NQR detection of this substance.

Prescott, D. W.; Malone, M. W.; Douglass, S. P.; Sauer, K. L.

2012-12-01

210

All-optical NMR in semiconductors provided by resonant cooling of nuclear spins interacting with electrons in the resonant spin amplification regime  

NASA Astrophysics Data System (ADS)

Resonant cooling of different nuclear isotopes manifested in optically induced nuclear magnetic resonances (NMR) is observed in n-doped CdTe/(Cd,Mg)Te and ZnSe/(Zn,Mg)Se quantum wells and for donor-bound electrons in ZnSe:F and GaAs epilayers. By time-resolved Kerr rotation used in the regime of resonant spin amplification, we can expand the range of magnetic fields where the effect can be observed up to nuclear Larmor frequencies of 170 kHz. The mechanism of the resonant cooling of the nuclear spin system is analyzed theoretically. The developed approach allows us to model the resonant spin amplification signals with NMR features.

Zhukov, E. A.; Greilich, A.; Yakovlev, D. R.; Kavokin, K. V.; Yugova, I. A.; Yugov, O. A.; Suter, D.; Karczewski, G.; Wojtowicz, T.; Kossut, J.; Petrov, V. V.; Dolgikh, Yu. K.; Pawlis, A.; Bayer, M.

2014-08-01

211

Investigation of a new model of dipolar-coupled nuclear spin relaxation and applications of dynamic nuclear polarization  

NASA Astrophysics Data System (ADS)

This work presents the results of various investigations using various techniques of hyperpolarizing the nuclei of atoms. Hyperpolarization implies magnetic order in excess of the thermal order obtained naturally as described by Curie's law. The main portion of this work presents the results of a detailed experimental exploration of predictions arising from a new model of transverse nuclear spin relaxation in quantum systems, based on possible manifestations of microscopic chaos in quantum systems. Experiments have been carried out on a number of hyperpolarized xenon samples, each differing in its relative percentage of xenon isotopes in order to vary the homonuclear and heteronuclear dipole couplings in the spin system. The experiments were performed under a variety of conditions in an attempt to observe the behaviors predicted by the model. Additionally, much more extensive measurements were made on a number of samples of solid CaF2 in both single crystal and powder forms. These samples, although thermally polarized, were observed with superior signal to noise ratios than even the hyperpolarized xenon solids, allowing for more precise measurements for comparison to the theory. This work thus contains the first experimental evidence for the majority of the model's predictions. Additionally, this work contains the first precise measurements of the frequency-shift enhancement parameters for 129Xe and krypton in the presence of spin-polarized Rb. The determination of these important numbers will be useful to many groups who utilize spin-exchange optical pumping in their labs. This work built on the prior knowledge of a precise number for the frequency-shift enhancement parameter of 3He in Rb vapor. Finally, I detail work using NMR to detect nuclear-spin polarization enhancement in silicon phosphorus by a novel, photo-induced hyperpolarization technique developed by the Boehme research group at the University of Utah. Significant nuclear polarization enhancements were observed by the Boehme group due to electron-photon interactions in semiconductor soilds; these enhancements were observed by their effects on the ambient electrons and measured with electron spin resonance techniques. The work described here details experiments to observe the enhanced nuclear polarization by directly measuring the intensity increase in an NMR measurement. I will conclude this dissertation with a brief appendix giving a summary of one additional project involving the use of high pressure fluorinated gas NMR to measure the internal topology and characteristics of energy-rich oil shales.

Sorte, Eric G.

212

Natural reference for nuclear high-spin states  

SciTech Connect

We suggest two new representations of the data on rotational nuclei. The first is reference-free and the second arises from a natural reference related to the variable moment of inertia model parameters of the ground-state band of the system. As such, neither representation contains any free parameters. By defining a 'configuration spin' we show how a new ground-state band reference can be applied. Its use allows a complete description of the changes associated with the first, and higher, band crossings. We apply these new representations to discuss the nature of the first band crossing along even-even isotopic chains in the erbium and osmium isotopes and to odd-even nuclei in the vicinity of {sup 158}Er.

Rowley, Neil; Ollier, James; Simpson, John [UMR 8608, Universite de Paris Sud/IN2P3, Division de Physique Theorique, Institut de Physique Nucleaire, F-91406 Orsay Cedex (France); STFC Daresbury Laboratory, Daresbury, Warrington WA44AD (United Kingdom)

2009-08-15

213

Active nuclear spin maser oscillation with double cell  

NASA Astrophysics Data System (ADS)

Uncertainty in the frequency precision of the planned experiment to search for a 129Xe atomic electric dipole moment is dominated by drifts in the frequency shift due to contact interaction of 129Xe with polarized Rb valence electrons. In order to suppress the frequency shift, a double-cell geometry has been adopted for the confinement of 129Xe gas. A new process has been identified to take part in the optical detection of spin precession. The parameters controlling the oscillation of the maser in this new double-cell arrangement were optimized. As a result, the frequency shift has been reduced by a factor of 10 or more from the former single-cell geometry.

Hikota, E.; Chikamori, M.; Ichikawa, Y.; Ohtomo, Y.; Sakamoto, Y.; Suzuki, T.; Bidinosti, C. P.; Inoue, T.; Furukawa, T.; Yoshimi, A.; Suzuki, K.; Nanao, T.; Miyatake, H.; Tsuchiya, M.; Yoshida, N.; Shirai, H.; Ino, T.; Ueno, H.; Matsuo, Y.; Fukuyama, T.; Asahi, K.

2014-03-01

214

Spin  

Microsoft Academic Search

According to quantum mechanics, spin—the intrinsic angular momentum of an electron, nucleus, or elementary particle at rest—is\\u000a a decidedly nonclassical concept. The ? spin statistics theorem of ? quantum statistics distinguishes bosons and fermions\\u000a obeying ? Bose-Einstein statistics or ? Fermi-Dirac statistics, respectively, depending on whether the particle's spin is\\u000a an even or odd multiple of h\\/2, with h =

Klaus Hentschel

215

Observation of high-temperature spin fluctuations in UBe13 by nuclear-spin relaxation  

NASA Astrophysics Data System (ADS)

We report the extension of measurements of the 9Be spin-lattice relaxation rate in UBe13 from 300 up to 1000 K. They reflect the fluctuating local magnetic field at the site of the 9Be nuclei. Above about 100 K, there appears a new contribution in addition to the rate observed at lower temperatures. The high temperature contribution is modeled in terms of the thermal excitation of low-lying states of the U3+ ion along lines used by Felton et al. to explain their measurements of the specific heat. Our results indicate a splitting of 200±20 K between the ground and excited states of the system, and a lifetime of 8×10-14 s for the excited states (width =95 K).

Clark, W. G.; Wong, W. H.; Hines, W. A.; Lan, M. D.; MacLaughlin, D. E.; Fisk, Z.; Smith, J. L.; Ott, H. R.

1988-04-01

216

Theoretical model for enrichment of CH{sub 3}F nuclear-spin isomers by resonant microwave radiation  

SciTech Connect

A theoretical model of coherent control of nuclear-spin isomers by microwave radiation has been developed. The model accounts the M degeneracy of molecular states and molecular center-of-mass motion. The model has been applied to the {sup 13}CH{sub 3}F molecules. Microwave radiation excites the para state (J=11, K=1) which is mixed by the nuclear-spin-spin interaction with the ortho state (9,3). Dependences of the isomer enrichment and conversion rates on the radiation frequency have been calculated. Both spectra consist of two resonances situated at the centers of nuclear-spin-allowed and -forbidden transitions of the molecule. Larger enrichment, up to 7%, can be produced by strong radiation resonant to the forbidden transition. The spin conversion rate can be increased by two orders of magnitude at this resonance.

Permyakova, O.I.; Ilisca, E.; Chapovsky, P.L. [Institute of Semiconductor Physics, Russian Academy of Sciences, 630090 Novosibirsk (Russian Federation); Laboratoire de Physique Theorique de la Matiere Condensee, Universite Paris 7-Denis Diderot, 2, Place Jussieu, 75251 Paris Cedex 05 (France); Institute of Automation and Electrometry, Russian Academy of Sciences, 630090 Novosibirsk (Russian Federation)

2003-03-01

217

Nuclear Spin-Echo Fourier-Transform Mapping Spectroscopy for Broad NMR Lines in Solids  

NASA Astrophysics Data System (ADS)

A basic theoretical description of nuclear spin-echo Fourier-transform mapping spectroscopy (NSEFTMS) for broad NMR lines was derived from the well-established time-domain spin-echo theory. It has been shown that when the mapping step is less than the radiation field strength under typical conditions of spin-echo experiments, the NSEFTMS mimics precisely the original NMR spectrum. Most important, the NSEFTMS present a more efficient alternative in practice to the conventional point-by-point scanning technique that is, in general, time consuming in studying broad NMR lines in solids, especially when there exist some sharp features. A preliminary 31P NMR study of an iron (II) diphosphate (Fe 2P 2O 7) sample, which is one kind of precursor for the heterogeneous catalytic ferri-phosphate system (FePO), has been taken as an example of the application of the theory.

Tong, Y. Y.

218

Room-temperature high-speed nuclear-spin quantum memory in diamond  

E-print Network

Quantum memories provide intermediate storage of quantum information until it is needed for the next step of a quantum algorithm or a quantum communication process. Relevant figures of merit are therefore the fidelity with which the information can be written and retrieved, the storage time, and also the speed of the read-write process. Here, we present experimental data on a quantum memory consisting of a single $^{13}$C nuclear spin that is strongly coupled to the electron spin of a nitrogen-vacancy (NV) center in diamond. The strong hyperfine interaction of the nearest-neighbor carbon results in transfer times of 300 ns between the register qubit and the memory qubit, with an overall fidelity of 88 % for the write - storage - read cycle. The observed storage times of 3.3 ms appear to be limited by the T$_1$ relaxation of the electron spin. We discuss a possible scheme that may extend the storage time beyond this limit.

J. H. Shim; I. Niemeyer; J. Zhang; D. Suter

2013-01-03

219

Optical and Nuclear Spin Spectroscopy in PRASEODYMIUM(3+):LANTHANUM Fluoride by Optical Pumping  

NASA Astrophysics Data System (ADS)

A Stark Modulated Optical Pumping (SMOP) technique was used as a sensitive probe of optical hole-burning to study the effects of nuclear spin interactions in Pr ^{3+}:LaF_3. The results of two experiments are reported. In the first experiment, the SMOP technique is applied for optical detection of the NQR spectrum of the Pr^{3+} optical ground state. Frequency and linewidth variations of the Pr ^{3+} ground state hyperfine levels for different positions within the main ^3 H_4(Gamma1) -^1D_2(Gamma 1) inhomogeneous optical line and satellite transitions of Pr^{3+}:LaF _3 are observed. A linear increase in the broadening of the Pr^{3+} hyperfine transitions, without a shift of central frequency, is measured as the laser is tuned toward the wings of the inhomogeneous optical transition. The linear variation is attributed to electric quadrupole broadening caused by changes in local density of point defects across the Stark broadened optical transition. The optically detected NQR spectra of the satellite transitions associated with Pr ion pairs are shifted in frequency, and for most satellites are narrower in width than the NQR spectra found in the wings of the main inhomogeneous optical line. In the second experiment, direct evidence for the presence of a spin diffusion barrier or "frozen core" in Pr^{3+}:LaF _3 is observed by examining the cross relaxation between the Pr and F nuclei in a magnetic field chosen so that a pair of the optical ground state Pr^ {3+} hyperfine energy levels matches the F splitting or a multiple of the F splitting. This level crossing condition allows resonant flip-flop interactions with the nearest neighbor frozen core fluorine spins to re-populate Pr^{3+} hyperfine levels emptied by laser hole-burning, and is detected as enhanced absorption of the laser beam. The coupling of core fluorine spins to bulk fluorine spins during Pr-F cross-relaxation is measured by NMR of the bulk fluorine spin magnetization. The rate of cross relaxation between the Pr spins and the bulk F spins measured in this way is at least three to four orders of magnitude slower than that expected in the absence of a spin diffusion barrier. This reduction of coupling indicates nearly complete de-tuning of the frozen core F spins immediately surrounding the Pr^{3+} ion, cutting off resonant coupling with the bulk F spins.

Wald, Lawrence Leroy

220

(1)H nuclear spin relaxation of liquid water from molecular dynamics simulations.  

PubMed

We have investigated the nuclear spin relaxation properties of (1)H in liquid water with the help of molecular dynamics simulations. We have computed the (1)H nuclear spin relaxation times T1 and T2 and determined the contribution of the different interactions to the relaxation at different temperatures and for different classical water models (SPC/E, TIP3P, TIP4P, and TIP4P/2005). Among the water models considered, the TIP4P/2005 model exhibits the best agreement with the experiment. The same analysis was performed with Car-Parrinello ab initio molecular dynamics simulations of bulk water at T = 330 K, which provided results close to the experimental values at room temperature. To complete the study, we have successfully accounted for the temperature-dependence of T1 and T2 in terms of a simplified model, which considers the reorientation in finite angle jumps and the diffusive translation of water molecules. PMID:25584483

Calero, C; Martí, J; Guàrdia, E

2015-02-01

221

Asymmetry and Spin-Orbit Effects in Binding Energy in the Effective Nuclear Surface Approximation  

E-print Network

Isoscalar and isovector particle densities are derived analytically by using the approximation of a sharp edged nucleus within the local energy density approach with the proton-neutron asymmetry and spin-orbit effects. Equations for the effective nuclear-surface shapes as collective variables are derived up to the higher order corrections in the form of the macroscopic boundary conditions. The analytical expressions for the isoscalar and isovector tension coefficients of the nuclear surface binding energy and the finite-size corrections to the $\\beta $ stability line are obtained.

A. G. Magner; A. I. Sanzhur; A. M. Gzhebinsky

2008-12-19

222

Relativistic theory of nuclear spin-rotation tensor with kinetically balanced rotational London orbitals  

NASA Astrophysics Data System (ADS)

Both kinetically balanced (KB) and kinetically unbalanced (KU) rotational London orbitals (RLO) are proposed to resolve the slow basis set convergence in relativistic calculations of nuclear spin-rotation (NSR) coupling tensors of molecules containing heavy elements [Y. Xiao and W. Liu, J. Chem. Phys. 138, 134104 (2013)]. While they perform rather similarly, the KB-RLO Ansatz is clearly preferred as it ensures the correct nonrelativistic limit even with a finite basis. Moreover, it gives rise to the same "direct relativistic mapping" between nuclear magnetic resonance shielding and NSR coupling tensors as that without using the London orbitals [Y. Xiao, Y. Zhang, and W. Liu, J. Chem. Theory Comput. 10, 600 (2014)].

Xiao, Yunlong; Zhang, Yong; Liu, Wenjian

2014-10-01

223

Optical and Nuclear Spin Spectroscopy in PRASEODYMIUM(3+):LANTHANUM Fluoride by Optical Pumping  

Microsoft Academic Search

A Stark Modulated Optical Pumping (SMOP) technique was used as a sensitive probe of optical hole-burning to study the effects of nuclear spin interactions in Pr ^{3+}:LaF_3. The results of two experiments are reported. In the first experiment, the SMOP technique is applied for optical detection of the NQR spectrum of the Pr^{3+} optical ground state. Frequency and linewidth variations

Lawrence Leroy Wald

1992-01-01

224

Nuclear structure aspects of spin-independent WIMP scattering off xenon  

E-print Network

We study the structure factors for spin-independent WIMP scattering off xenon based on state-of-the-art large-scale shell-model calculations, which are shown to yield a good spectroscopic description of all experimentally relevant isotopes. Our results are based on the leading scalar one-body currents only. At this level and for the momentum transfers relevant to direct dark matter detection, the structure factors are in very good agreement with the phenomenological Helm form factors used to give experimental limits for WIMP-nucleon cross sections. In contrast to spin-dependent WIMP scattering, the spin-independent channel, at the one-body level, is less sensitive to nuclear structure details. In addition, we explicitly show that the structure factors for inelastic scattering are suppressed by ~ 10^{-4} compared to the coherent elastic scattering response. This implies that the detection of inelastic scattering will be able to discriminate clearly between spin-independent and spin-dependent scattering. Finally, we provide fits for all calculated structure factors.

L. Vietze; P. Klos; J. Menéndez; W. C. Haxton; A. Schwenk

2014-12-05

225

Nuclear structure aspects of spin-independent WIMP scattering off xenon  

E-print Network

We study the structure factors for spin-independent WIMP scattering off xenon based on state-of-the-art large-scale shell-model calculations, which are shown to yield a good spectroscopic description of all experimentally relevant isotopes. Our results are based on the leading scalar one-body currents only. At this level and for the momentum transfers relevant to direct dark matter detection, the structure factors are in very good agreement with the phenomenological Helm form factors used to give experimental limits for WIMP-nucleon cross sections. In contrast to spin-dependent WIMP scattering, the spin-independent channel, at the one-body level, is less sensitive to nuclear structure details. In addition, we explicitly show that the structure factors for inelastic scattering are suppressed by ~ 10^{-4} compared to the coherent elastic scattering response. This implies that the detection of inelastic scattering will be able to discriminate clearly between spin-independent and spin-dependent scattering. Finall...

Vietze, L; Menéndez, J; Haxton, W C; Schwenk, A

2014-01-01

226

Solid-state nuclear-spin quantum computer based on magnetic resonance force microscopy G. P. Berman and G. D. Doolen  

E-print Network

Solid-state nuclear-spin quantum computer based on magnetic resonance force microscopy G. P. Berman September 1999 We propose a nuclear-spin quantum computer based on magnetic resonance force microscopy MRFM for a small number of spins.6­8 Magnetic resonance force microscopy MRFM has ma- tured over the past few years

Hammel, P. Chris

227

A NEW METHOD FOR EXTRACTING SPIN-DEPENDENT NEUTRON STRUCTURE FUNCTIONS FROM NUCLEAR DATA  

SciTech Connect

High-energy electrons are currently the best probes of the internal structure of nucleons (protons and neutrons). By collecting data on electrons scattering off light nuclei, such as deuterium and helium, one can extract structure functions (SFs), which encode information about the quarks that make up the nucleon. Spin-dependent SFs, which depend on the relative polarization of the electron beam and the target nucleus, encode quark spins. Proton SFs can be measured directly from electron-proton scattering, but those of the neutron must be extracted from proton data and deuterium or helium-3 data because free neutron targets do not exist. At present, there is no reliable method for accurately determining spin-dependent neutron SFs in the low-momentum-transfer regime, where nucleon resonances are prominent and the functions are not smooth. The focus of this study was to develop a new method for extracting spin-dependent neutron SFs from nuclear data. An approximate convolution formula for nuclear SFs reduces the problem to an integral equation, for which a recursive solution method was designed. The method was then applied to recent data from proton and deuterium scattering experiments to perform a preliminary extraction of spin-dependent neutron SFs in the resonance region. The extraction method was found to reliably converge for arbitrary test functions, and the validity of the extraction from data was verifi ed using a Bjorken integral, which relates integrals of SFs to a known quantity. This new information on neutron structure could be used to assess quark-hadron duality for the neutron, which requires detailed knowledge of SFs in all kinematic regimes.

Kahn, Y.F.; Melnitchouk, W.

2009-01-01

228

Study of spin polarized nuclear matter and finite nuclei with finite range simple effective interaction  

E-print Network

The properties of spin polarized pure neutron matter and symmetric nuclear matter are studied using the finite range simple effective interaction, upon its parametrization revisited. Out of the total twelve parameters involved, we now determine ten of them from nuclear matter, against the nine parameters in our earlier calculation, as required in order to have predictions in both spin polarized nuclear matter and finite nuclei in unique manner being free from uncertainty found using the earlier parametrization. The information on the effective mass splitting in polarized neutron matter of the microscopic calculations is used to constrain the one more parameter, that was earlier determined from finite nucleus, and in doing so the quality of the description of finite nuclei is not compromised. The interaction with the new set of parameters is used to study the possibilities of ferromagnetic and antiferromagnetic transitions in completely polarized symmetric nuclear matter. Emphasis is given to analyze the results analytically, as far as possible, to elucidate the role of the interaction parameters involved in the predictions.

B. Behera; X. Viñas; T. R. Routray; M. Centelles

2015-01-12

229

Nuclear-spin-induced cotton-mouton effect in a strong external magnetic field.  

PubMed

Novel, high-sensitivity and high-resolution spectroscopic methods can provide site-specific nuclear information by exploiting nuclear magneto-optic properties. We present a first-principles electronic structure formulation of the recently proposed nuclear-spin-induced Cotton-Mouton effect in a strong external magnetic field (NSCM-B). In NSCM-B, ellipticity is induced in a linearly polarized light beam, which can be attributed to both the dependence of the symmetric dynamic polarizability on the external magnetic field and the nuclear magnetic moment, as well as the temperature-dependent partial alignment of the molecules due to the magnetic fields. Quantum-chemical calculations of NSCM-B were conducted for a series of molecular liquids. The overall order of magnitude of the induced ellipticities is predicted to be 10(-11) -10(-6) rad?T(-1) ?M(-1) ?cm(-1) for fully spin-polarized nuclei. In particular, liquid-state heavy-atom systems should be promising for experiments in the Voigt setup. PMID:24862946

Fu, Li-Juan; Vaara, Juha

2014-08-01

230

Realization of quantum non-demolition measurement of nuclear spin 1/2 of cold ytterbium atom  

NASA Astrophysics Data System (ADS)

We have demonstrated a quantum non-demolition (QND) measurement with a collective spin of cold ytterbium atoms (171Yb) via Faraday rotation interaction, and have observed 1.8-1.5+2.4 dB spin squeezing. Since 171Yb atoms have only a nuclear spin of one-half in the ground state, the system constitutes the simplest spin ensemble and is thus robust against decoherence. Furthermore, we have considered the atomic quantum swapping gate as a quantum information device using multiple Faraday rotation interactions, and have found that we can realize the quantum-domain performance for a realistic experimental condition.

Takano, T.; Namiki, R.; Takahashi, Y.

2009-04-01

231

New nuclear-spin-induced Cotton-Mouton effect in fluids at high DC magnetic field.  

PubMed

Based on Buckingham and Pople's theory of magnetic double refraction, a theoretical expression is derived for a new Cotton-Mouton effect ?(C-M)((IB)) in liquid induced by the crossed effect between the high dc magnetic field B(0) and the nuclear magnetic moment m(z)((l)). It contains temperature-independent and -dependent parts. The latter is proportional to the product between anisotropy of polarizability and the nuclear magnetic shielding tensor. For this new effect ?(C-M)((IB)), its order in magnitude for a molecule with large polarizability anisotropy is estimated to be comparable to the nuclear-spin-induced optical Faraday rotation (NSOFR). In the multipass approach, ?(C-M)((IB)) can be eliminated by time-reversal symmetry arguments, but NSOFR is enhanced. PMID:22344831

Yao, Guo-hua; He, Ming; Chen, Dong-ming; He, Tian-jing; Liu, Fan-chen

2012-04-10

232

Rotor design for high pressure magic angle spinning nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

High pressure magic angle spinning (MAS) nuclear magnetic resonance (NMR) with a sample spinning rate exceeding 2.1 kHz and pressure greater than 165 bar has never been realized. In this work, a new sample cell design is reported, suitable for constructing cells of different sizes. Using a 7.5 mm high pressure MAS rotor as an example, internal pressure as high as 200 bar at a sample spinning rate of 6 kHz is achieved. The new high pressure MAS rotor is re-usable and compatible with most commercial NMR set-ups, exhibiting low 1H and 13C NMR background and offering maximal NMR sensitivity. As an example of its many possible applications, this new capability is applied to determine reaction products associated with the carbonation reaction of a natural mineral, antigorite ((Mg,Fe2+)3Si2O5(OH)4), in contact with liquid water in water-saturated supercritical CO2 (scCO2) at 150 bar and 50 °C. This mineral is relevant to the deep geologic disposal of CO2, but its iron content results in too many sample spinning sidebands at low spinning rate. Hence, this chemical system is a good case study to demonstrate the utility of the higher sample spinning rates that can be achieved by our new rotor design. We expect this new capability will be useful for exploring solid-state, including interfacial, chemistry at new levels of high-pressure in a wide variety of fields.

Turcu, Romulus V. F.; Hoyt, David W.; Rosso, Kevin M.; Sears, Jesse A.; Loring, John S.; Felmy, Andrew R.; Hu, Jian Zhi

2013-01-01

233

Rotor Design for High Pressure Magic Angle Spinning Nuclear Magnetic Resonance  

SciTech Connect

High pressure magic angle spinning (MAS) nuclear magnetic resonance (NMR) with a sample spinning rate exceeding 2.1 kHz and pressure greater than 165 bar has never been realized. In this work, a new sample cell design is reported, suitable for constructing cells of different sizes. Using a 7.5 mm high pressure MAS rotor as an example, internal pressure as high as 200 bar at a sample spinning rate of 6 kHz is achieved. The new high pressure MAS rotor is re-usable and compatible with most commercial NMR set-ups, exhibiting low 1H and 13C NMR background and offering maximal NMR sensitivity. As an example of its many possible applications, this new capability is applied to determine reaction products associated with the carbonation reaction of a natural mineral, antigorite ((Mg,Fe2+)3Si2O5(OH)4), in contact with liquid water in water-saturated supercritical CO2 (scCO2) at 150 bar and 50 deg C. This mineral is relevant to the deep geologic disposal of CO2, but its iron content results in too many sample spinning sidebands at low spinning rate. Hence, this chemical system is a good case study to demonstrate the utility of the higher sample spinning rates that can be achieved by our new rotor design. We expect this new capability will be useful for exploring solid-state, including interfacial, chemistry at new levels of high-pressure in a wide variety of fields.

Turcu, Romulus V.F.; Hoyt, David W.; Rosso, Kevin M.; Sears, Jesse A.; Loring, John S.; Felmy, Andrew R.; Hu, Jian Z.

2013-01-01

234

Quadrupolar spectra of nuclear spins in strained InxGa1-xAs quantum dots  

NASA Astrophysics Data System (ADS)

Self-assembled quantum dots (QDs) are born out of lattice mismatched ingredients where strain plays an indispensable role. Through the electric quadrupolar coupling, strain affects the magnetic environment as seen by the nuclear spins. To guide prospective single-QD nuclear magnetic resonance (NMR), as well as dynamic nuclear spin polarization experiments, an atomistic insight to the strain and quadrupolar field distributions is presented. A number of implications of the structural and compositional profile of the QD have been identified. A high aspect ratio of the QD geometry enhances the quadrupolar interaction. The inclined interfaces introduce biaxiality and the tilting of the major quadrupolar principal axis away from the growth axis; the alloy mixing of gallium into the QD enhances both of these features while reducing the quadrupolar energy. Regarding the NMR spectra, both Faraday and Voigt geometries are investigated, unraveling in the first place the extend of inhomogeneous broadening and the appearance of the normally forbidden transitions. Moreover, it is shown that from the main extend of the NMR spectra the alloy mole fraction of a single QD can be inferred. By means of the element-resolved NMR intensities it is found that In nuclei has a factor of 5 dominance over those of As. In the presence of an external magnetic field, the borderlines between the quadrupolar and Zeeman regimes are extracted as 1.5 T for In and 1.1 T for As nuclei. At these values the nuclear spin depolarization rates of the respective nuclei get maximized due to the noncollinear secular hyperfine interaction with a resident electron in the QD.

Bulutay, Ceyhun

2012-03-01

235

Nuclear spin--lattice relaxation measurements in small superconducting aluminum partilces  

SciTech Connect

The /sup 27/Al nuclear spin-lattice relaxation times T/sub 1/ have been measured in the normal and superconducting states of small aluminum particles with average particle diameters ranging from 170 to 750 A. Experiments were performed in magnetic fields between 0 and 1200 Oe and at temperatures between 0.5 and 4.2 K. The nuclear spin-lattice relaxation rate 1/T/sub 1/ at zero and low magnetic fields is characterized by a sum of a Korringa rate (due to conduction-electron spin-flip scattering) and an additonal rate, which is attributed to a crossfield (1200 Oe), where the Zeeman energy either dominates in larger particles or play an important role in smaller particles, measured rates for all three samples are in good agrreement with the microscopic theory of Sone. At low fields (H< or =150 Oe) our T/sub 1/ results, which show a strong field dependence and less effect of superconducting fluctuations near T/sub c/, are in disagreement with Sone. We suggest that the theory has overestimated the effects of fluctuations on quasiparticle excitations at these low fields.

Tse, P.K.; MacLaughlin, D.E.

1980-05-01

236

Ab initio nuclear shielding parameters and spin-rotation coupling constants of FBO, ClBO and FBS  

NASA Astrophysics Data System (ADS)

Ab initio nuclear shielding parameters and nuclear spin-rotation coupling constants of FBO, ClBO and FBS have been calculated using the multi-configuration self consistent field (MCSCF) method. The dependence of these parameters upon the basis set and active space employed in the calculation was investigated. The results are compared with the experimental values obtained from microwave spectra.

Gatehouse, Bethany

1998-05-01

237

J coupling in chemically equivalent spin pairs as studied by solid-state nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

The presence of J coupling was observed in the solid-state nuclear magnetic resonance (NMR) spectrum of the 31P spin pair in polycrystalline 1,2-bis (2,4,6-tri-tert-butylphenyl)-diphosphene (TBPDP) using the magic-angle spinning (MAS) technique. This represents the first example of J coupling in a spin-pair system with nuclei having identical isotropic chemical shifts. Average Hamiltonian theory is used to derive the time-independent eigenstates for the system. It is shown that a second-order perturbation term, which is dependent on the difference between the chemical-shift tensor orientations in addition to the strength of the dipolar coupling, allows the recoupling of the J interaction for the two chemically equivalent 31P nuclei. In the absence of the perturbation term, the system is reduced to an A2 case in solution-state NMR for which, of course, no J coupling may be observed. The magnitude of the J coupling, namely, 580±20 Hz obtained from two-dimensional (2D) J-resolved experiments was found to be in excellent agreement with the value of 577±15 Hz estimated using the abovementioned theory and experimental data from the one-dimensional (1D) spectra measured as a function of the rotor spinning frequency.

Challoner, Robin; Nakai, Toshihito; McDowell, Charles A.

1991-06-01

238

Parity mixing of pair at nuclear surface due to spin-orbit potential in $^{18}$F  

E-print Network

We investigate the structure of $^{18}$F with the microscopic wave function based on the three-body $^{16}$O+$p$+$n$ model. In the calculation of the generator coordinate method (GCM) of the three-body model, $T=0$ energy spectra of $J^\\pi=1^+$, $3^+$, and $5^+$ states and $T=1$ spectra of $J^\\pi=0^+$, $2^+$ states in $^{18}$F are described reasonably. Based on the dinucleon picture, the effect of the spin-orbit force on the $T=0$ and $T=1$ $pn$ pairs around the $^{16}$O core is discussed. The $T=1$ pair in the $J^\\pi=0^+$ state gains the spin-orbit potential energy involving the odd-parity mixing in the pair. The spin-orbit potential energy gain with the parity mixing is not so efficient for the $T=0$ pair in the $J^\\pi=1^+$ state. The parity mixing in the pair is regarded as the internal symmetry breaking of the pair in the spin-orbit potential at the nuclear surface.

Yoshiko Kanada-En'yo; Fumiharu Kobayashi

2014-07-01

239

Carbon13 Depletion in a Hydrothermal Vent Mussel: Suggestion of a Chemosynthetic Food Source  

Microsoft Academic Search

Tissues of a mytilid mussel from the Clambake I hydrothermal vent in the Galapagos Rift zone are strikingly depleted in carbon-13 relative to the tissues of other marine organisms. The stable carbon isotope composition of this mussel suggests that chemoautotrophic bacteria present in the hydrothermal waters are a major food source for filter-feeding organisms in this abyssal environment.

Greg H. Rau; John I. Hedges

1979-01-01

240

The Carbon-13 Pockets in AGB Stars and Their Fingerprints in Mainstream SiC Grains  

NASA Astrophysics Data System (ADS)

Strontium, Zr, and Ba isotopic compositions of mainstream presolar SiC grains are used to constrain the concentration and distribution of carbon-13, the main neutron source for the s-process, in the intershell region of asymptotic giant branch stars.

Liu, N.; Davis, A. M.; Gallino, R.; Savina, M. R.; Bisterzo, S.; Gyngard, F.; Dauphas, N.; Pellin, M. J.

2014-09-01

241

Understanding electron and nuclear spin dynamics in Cr^5+ doped K3NbO8  

NASA Astrophysics Data System (ADS)

Chromium(V) doped in the diamagnetic host potassium niobate, a simple spin S=.5ex1-.1em/ -.15em.25ex2 , I = 0 system, has been proposed as an alternative standard for field calibration and g-standard for high-field EPR [1]. This system constitutes a dilute two-level model relevant for use as a electron spin qubit [2] and as such coherent electron spin manipulation at X-band (˜9.5 GHz) was observed over a wide range temperature. Rabi oscillations are observed for the first time in a spin system based on transition metal oxides up to room temperature. At 4 K, a Rabi frequency ?R of 20 MHz together with the phase coherence relaxation (spin-spin relaxation) time, T2 of ˜10 ?s results in the single qubit figure of merit QM (=?RT2/?) as about 500, showing that a diluted ensemble of Cr(V) (S = 1/2) doped K3NbO8 is a potential candidate for solid-state quantum information processing. Also, the field and temperature dependence of the T1 (spin-lattice relaxation) and T2 times was investigated [3] for a further understanding of the relaxation mechanisms governing the phase decoherence in this system. These studies show that the coupling of the electron spin with the neighboring ^39K nuclei (I = 3/2) is one of the prominent T2 mechanisms. The hyperfine and quadrupole interactions with ^39K nuclei was resolved by using the high-frequency (240 GHz) pulsed electron nuclear double resonance (ENDOR). [3pt] [1]. B. Cage, A. Weekley, L. -C. Brunel and N. S. Dalal, Anal. Chem. 71, 1951 (1999). [0pt] [2]. S. Nellutla, K.-Y. Choi, M. Pati, J. van Tol, I. Chiroescu and N. S. Dalal, Phys. Rev. Lett. 99, 137601 (2007). [0pt] [3]. S. Nellutla, G. W. Morley, M. Pati, N. S. Dalal and J. van Tol, Phys. Rev. B. 78, 054426 (2008).

Nellutla, Saritha

2009-03-01

242

Optical Measurement of the Effect of Electric Fields on the Nuclear Spin Coherence of Rare-Earth Ions in Solids  

NASA Astrophysics Data System (ADS)

We show that the coherence properties of the nuclear spin states of rare-earth ions in solids can be manipulated by small applied electric fields. This was done by measuring the Stark effect on the nuclear quadrupole transitions of Eu151 in Y2SiO5 (YSO) using a combination of Raman heterodyne optical detection and Stark modulated quadrupole echoes to achieve high sensitivity. The measured Stark coefficients were 0.42 and 1.0 Hz cm /V for the two quadrupole transitions at 34.54 and 46.20 MHz, respectively. The long decoherence time of the nuclear spin states (25 ms) allowed us to make the measurements in very low electric fields of ˜10 V/cm, which produced 100% modulation of the nuclear spin echo, and to measure Stark shifts of ˜1 Hz or 20 ppm of the inhomogeneous linewidth.

Macfarlane, R. M.; Arcangeli, A.; Ferrier, A.; Goldner, Ph.

2014-10-01

243

Long-lived nuclear spin states in methyl groups and quantum-rotor-induced polarization.  

PubMed

Substances containing rapidly rotating methyl groups may exhibit long-lived states (LLSs) in solution, with relaxation times substantially longer than the conventional spin-lattice relaxation time T1. The states become long-lived through rapid internal rotation of the CH3 group, which imposes an approximate symmetry on the fluctuating nuclear spin interactions. In the case of very low CH3 rotational barriers, a hyperpolarized LLS is populated by thermal equilibration at liquid helium temperature. Following dissolution, cross-relaxation of the hyperpolarized LLS, induced by heteronuclear dipolar couplings, generates strongly enhanced antiphase NMR signals. This mechanism explains the NMR signal enhancements observed for (13)C-?-picoline (Icker, M.; Berger, S. J. Magn. Reson. 2012, 219, 1-3). PMID:24252212

Meier, Benno; Dumez, Jean-Nicolas; Stevanato, Gabriele; Hill-Cousins, Joseph T; Roy, Soumya Singha; Håkansson, Pär; Mamone, Salvatore; Brown, Richard C D; Pileio, Giuseppe; Levitt, Malcolm H

2013-12-18

244

Nuclear magnetic resonance study of spin relaxation and magnetic field gradients in maple leaves.  

PubMed

1H Nuclear magnetic resonance techniques were used to measure the distributions of spin-spin relaxation times, T2, and of magnetic field gradients in both the chloroplast and nonchloroplast water compartments of maple leaves (Acer platanoides). Results showed that encounters between water molecules and membranes inside chloroplasts provide an inefficient relaxation mechanism; i.e., chloroplast membranes interact weakly with water molecules. Gradient measurements indirectly measured the sizes of chloroplasts by showing that water in the chloroplasts is confined to small compartments a few microns in diameter. A comparison between measured gradients and gradients calculated for a model leaf indicated that chloroplasts are somewhat more likely to occupy positions along cell walls adjacent to air spaces, but also they may be found in the interiors of cells. PMID:8519965

McCain, D C

1995-09-01

245

Impact of hadronic and nuclear corrections on global analysis of spin-dependent parton distributions  

SciTech Connect

We present the first results of a new global next-to-leading order analysis of spin-dependent parton distribution functions from the most recent world data on inclusive polarized deep-inelastic scattering, focusing in particular on the large-x and low-Q^2 regions. By directly fitting polarization asymmetries we eliminate biases introduced by using polarized structure function data extracted under nonuniform assumptions for the unpolarized structure functions. For analysis of the large-x data we implement nuclear smearing corrections for deuterium and 3He nuclei, and systematically include target mass and higher twist corrections to the g_1 and g_2 structure functions at low Q^2. We also explore the effects of Q^2 and W^2 cuts in the data sets, and the potential impact of future data on the behavior of the spin-dependent parton distributions at large x.

Jimenez-Delgado, Pedro [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Accardi, Alberto [Hampton University, Hampton, VA (United States); Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Melnitchouk, Wally [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)

2014-02-01

246

Size dependence of (13)C nuclear spin-lattice relaxation in micro- and nanodiamonds.  

PubMed

Size dependence of physical properties of nanodiamond particles is of crucial importance for various applications in which defect density and location as well as relaxation processes play a significant role. In this work, the impact of defects induced by milling of micron-sized synthetic diamonds was studied by magnetic resonance techniques as a function of the particle size. EPR and (13)C NMR studies of highly purified commercial synthetic micro- and nanodiamonds were done for various fractions separated by sizes. Noticeable acceleration of (13)C nuclear spin-lattice relaxation with decreasing particle size was found. We showed that this effect is caused by the contribution to relaxation coming from the surface paramagnetic centers induced by sample milling. The developed theory of the spin-lattice relaxation for such a case shows good compliance with the experiment. PMID:25646270

Panich, A M; Sergeev, N A; Shames, A I; Osipov, V Yu; Boudou, J-P; Goren, S D

2015-02-25

247

EDM measurement in 129Xe atom using dual active feedback nuclear spin maser  

NASA Astrophysics Data System (ADS)

The technique of an active nuclear spin maser is adopted in the search for electric dipole moment in a diamagnetic atom 129Xe. In order to reduce systematic uncertainties arising from long-term drifts of the external magnetic field and from the contact interaction between longitudinal polarized Rb atoms and 129Xe spin, a 3He comagnetometer with a double-cell geometry was employed. The remaining shift, which turned out to show some correlation with the cell temperature, was mitigated by stabilizing the cell temperature. As a result, the frequency drift of the 129Xe maser was reduced from 12 mHz to 700 ?Hz, and the determination precision of frequency of 8.7 nHz was obtained for a 2×104 s measurement time using the double-cell geometry cell.

Sato, T.; Ichikawa, Y.; Ohtomo, Y.; Sakamoto, Y.; Kojima, S.; Funayama, C.; Suzuki, T.; Chikamori, M.; Hikota, E.; Tsuchiya, M.; Furukawa, T.; Yoshimi, A.; Bidinosti, C. P.; Ino, T.; Ueno, H.; Matsuo, Y.; Fukuyama, T.; Asahi, K.

2014-12-01

248

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

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

249

Nuclear spin-lattice relaxation from fractional wobbling in a cone  

E-print Network

We consider nuclear spin-lattice relaxation rate resulted from a fractional diffusion equation for anomalous rotational wobbling in a cone. The mechanism of relaxation is assumed to be due to dipole-dipole interaction of nuclear spins and is treated within the framework of the standard Bloemberger, Purcell, Pound - Solomon scheme. We consider the general case of arbitrary orientation of the cone axis relative the magnetic field. The BPP-Solomon scheme is shown to remain valid for systems with the distribution of the cone axes depending only on the tilt relative the magnetic field but otherwise being isotropic. We consider the case of random isotropic orientation of cone axes relative the magnetic field taking place in powders. Also we consider the case of their predominant orientation along or opposite the magnetic field and that of their predominant orientation transverse to the magnetic field which may be relevant for, e.g., liquid crystals. Besides we treat in details the model case of the cone axis directed along the magnetic field. The latter provides direct comparison of the limiting case of our formulas with the textbook formulas for ordinary isotropic rotational diffusion. We show that the present model enables one to obtain naturally the well known power law for Larmor frequency dependence of the spin-lattice relaxation rate. The latter is observed in some complex systems. From this law the dependence of the fractional diffusion coefficient on the fractional index is obtained to have a rather simple functional form. The dependence of the spin-lattice relaxation rate on the cone half-width for the case of ordinary rotational diffusion yields results similar to those predicted by the model-free approach.

A. E. Sitnitsky

2011-06-29

250

Multi-scales nuclear spin relaxation of liquids in porous media  

NASA Astrophysics Data System (ADS)

The magnetic field dependence of the nuclear spin-lattice relaxation rate 1/T(?) is a rich source of dynamical information for characterizing the molecular dynamics of liquids in confined environments. Varying the magnetic field changes the Larmor frequency ?, and thus the fluctuations to which the nuclear spin relaxation is sensitive. Moreover, this method permits a more complete characterization of the dynamics than the usual measurements as a function of temperature at fixed magnetic field strength, because many common solvent liquids have phase transitions that may alter significantly the character of the dynamics over the temperature range usually studied. Further, the magnetic field dependence of the spin-lattice relaxation rate, 1/T(?), provides a good test of the theories that relate the measurement to the microdynamical behavior of the liquid. This is especially true in spatially confined systems where the effects of reduced dimensionality may force more frequent reencounters of the studied proton spin-bearing molecules with paramagnetic impurities at the pore surfaces that may alter the correlation functions that enter the relaxation equations in a fundamental way. We show by low field NMR relaxation that changing the amount of surface paramagnetic impurities leads to striking different pore-size dependences of the relaxation times T and T of liquids in pores. Here, we focus mainly on high surface area porous materials including calibrated porous silica glasses, granular packings, heterogeneous catalytic materials, cement-based materials and natural porous materials such as clay minerals and rocks. Recent highlights NMR relaxation works are reviewed for these porous materials, like continuous characterization of the evolving microstructure of various cementitious materials and measurement of wettability in reservoir carbonate rocks. Although, the recent applications of 2-dimensional T-T and T-z-store-T correlation experiments for characterization of water exchange in connected micropores of cement pastes are also outlined.

Korb, Jean-Pierre

2010-03-01

251

Interlayer transport of nuclear spin polarization in ? = 2/3 quantum Hall states  

SciTech Connect

We investigated the interlayer diffusion of nuclear spin polarization (NSP) by using the phase transition point of quantum Hall states at a Landau level filling factor of ? ? 2/3 in a double quantum well sample. When the NSP is current-pumped in one layer, the magnetoresistance in the other layer is enhanced after a delay of 150 s and the raising speed of this layer is lower than that of the pumped layer. The delay and lower value of the raising speed are explained by the diffusion of NSP.

Tsuda, S.; Nguyen, M. H. [Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Terasawa, D.; Fukuda, A. [Department of Physics, Hyogo College of Medicine, Nishinomiya, Hyogo 663-8501 (Japan); Zheng, Y. D.; Arai, T.; Sawada, A. [Research Center for Low Temperatures and Materials Sciences, Kyoto University, Kyoto 606-8501 (Japan)

2013-12-04

252

Studies of Phospholipid Hydration by High-Resolution Magic-Angle Spinning Nuclear Magnetic Resonance  

Microsoft Academic Search

A sample preparation method using spherical glass ampoules has been used to achieve 1.5-Hz resolution in 1H magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of aqueous multilamellar dispersions of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), serving to differentiate between slowly exchanging interlamellar and bulk water and to reveal new molecular-level information about hydration phenomena in these model biological membranes. The

Zhe Zhou; Brian G. Sayer; Donald W. Hughes; Ruth E. Stark; Richard M. Epand

1999-01-01

253

Nuclear spin--lattice relaxation rate in Kondo superconductors in the gapless state  

SciTech Connect

The host nuclear spin--lattice relaxation rates in Kondo superconductors in the gapless state are derived within the framework of the Matsuura, chinose, and Nagaoka (MIN) theory of the Kondo effect. The relaxation rates for both low-T/sub K/ and high-T/sub K/ Kondo superconductors are obtained. The temperature dependence of the relaxation rate in low-T/sub K/ Kondo superconductors in the gapless state arising from the pair breaking by the Kondo impurity is obtained. The dependence of the relaxation rate for high-T/sub K/ Kondo superconductors in the gapless state on the external magnetic field producing the gapless state is also obtained.

Tang, I.M.

1985-12-01

254

Spinning-rate dependence of 31P magic-angle-spinning nuclear magnetic resonance spectra in condensed phosphates  

NASA Astrophysics Data System (ADS)

Two spins with anisotropic chemical shifts and dipolar coupling show spinning-rate dependent resonance positions in magic-angle spinning NMR spectra. We have measured the spinning-rate dependence of the resonance position in 31P magic-angle-spinning NMR spectra ofcondensed phosphates such as Na 4P 2O 7· 10H 2O, Na 4P 2O 7, Ag 4P 2O 7, Mg 2P 2O 7· 3H 2O, Na 5P 3O 10, (KPO 3) n, and K 4P 2O 7. We have also calculated the spinning-rate-dependent position theoretically, and the agreements between the calculated and experimental results are very good. This phenomenon can be used to identify dipolarly coupled spin pairs, and we have applied it to the peak assignment in the spectra of K 4P 2O 7.

Hayashi, Shigenobu; Hayamizu, Kikuko

1991-11-01

255

Dipolar recoupling in magic angle spinning solid-state nuclear magnetic resonance.  

PubMed

Solid-state nuclear magnetic resonance (SSNMR) magic angle spinning (MAS) can be used to record high-resolution data dominated by site-specific information. Although MAS introduces high resolution by attenuating the anisotropic broadening, it also suppresses the nuclear dipole-dipole distance information that is the source of most structural data in the spectra. Such information can be reintroduced coherently and thus selectively by the application of a carefully chosen sequence of radiofrequency pulses, an approach that was introduced 20 years ago and is referred to as dipolar recoupling. This review presents the establishment of recoupling techniques in SSNMR and recalls the major steps achieved by the community throughout the last two decades. This review also presents emerging techniques and their corresponding new concepts. Finally, we present some recent developments based on second-order recoupling mechanisms and discuss their implications regarding dipolar truncation and the possibility to extract structural constraints in uniformly labeled systems. PMID:22404583

De Paëpe, Gaël

2012-01-01

256

Forbidden nuclear magnetic resonance transitions between singlet and triplet states in spin- 1/2 pair systems in rotating solids  

NASA Astrophysics Data System (ADS)

Forbidden transitions between singlet and triplet nuclear spin states in chemically equivalent spin- 1/2 pair systems were observed in the 31P cross-polarization magic-angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectrum of 1,2-bis (2,4,6-tri-tert-butylphenyl) diphosphene (TBPDP). The fine structure of the resonance lines changed dramatically with rotor spinning frequency. Using the average Hamiltonian theory, the origin of these singular phenomena was revealed to be due to high-order anisotropic interactions in the solid state. From analysis of the spectra, the value of the J coupling between the chemically equivalent 31P nuclei in TBPDP was estimated to be 577 ± 15 Hz.

Nakai, Toshihito; Challoner, Robin; McDowell, Charles A.

1991-05-01

257

The effect of spin-orbit nuclear charge density corrections due to the anomalous magnetic moment on halonuclei  

E-print Network

In this paper we consider the contribution of the anomalous magnetic moments of protons and neutrons to the nuclear charge density. We show that the spin-orbit contribution to the mean-square charge radius, which has been neglected in recent nuclear calculations, can be important in light halonuclei. We estimate the size of the effect in helium, lithium, and beryllium nuclei. It is found that the spin-orbit contribution represents a ~2% correction to the charge density at the center of the Be-7 nucleus. We derive a simple expression for the correction to the mean-square charge radius due to the spin-orbit term and find that in light halonuclei it may be larger than the Darwin-Foldy term and comparable to finite size corrections. A comparison of experimental and theoretical mean-square radii including the spin-orbit contribution is presented.

A. Ong; J. C. Berengut; V. V. Flambaum

2010-06-29

258

Effect of spin-orbit nuclear charge density corrections due to the anomalous magnetic moment on halonuclei  

SciTech Connect

In this paper we consider the contribution of the anomalous magnetic moments of protons and neutrons to the nuclear charge density. We show that the spin-orbit contribution to the mean-square charge radius, which has been neglected in recent nuclear calculations, can be important in light halonuclei. We estimate the size of the effect in helium, lithium, and beryllium nuclei. It is found that the spin-orbit contribution represents a approx2% correction to the charge density at the center of the {sup 7}Be nucleus. We derive a simple expression for the correction to the mean-square charge radius due to the spin-orbit term and find that in light halonuclei it may be larger than the Darwin-Foldy term and comparable to finite size corrections. A comparison of experimental and theoretical mean-square radii including the spin-orbit contribution is presented.

Ong, A.; Berengut, J. C.; Flambaum, V. V. [School of Physics, University of New South Wales, Sydney 2052 (Australia)

2010-07-15

259

Nuclear spin relaxation of sodium cations in bacteriophage Pf1 solutions D. N. Sobieski, N. R. Krueger, S. Vyas,a  

E-print Network

Nuclear spin relaxation of sodium cations in bacteriophage Pf1 solutions D. N. Sobieski, N. R The nuclear magnetic resonance NMR spectra for the I=3/2 23 Na cation dissolved into filamentous bacteriophage

Augustine, Mathew P.

260

Linear response theory in asymmetric nuclear matter for Skyrme functionals including spin-orbit and tensor terms  

E-print Network

The formalism of linear response theory for a Skyrme functional including spin-orbit and tensor terms is generalized to the case of infinite nuclear matter with arbitrary isospin asymmetry. Response functions are obtained by solving an algebraic system of equations, which is explicitly given. Spin-isospin strength functions are analyzed varying the conditions of density, momentum transfer, asymmetry and temperature. The presence of instabilities, including the spinodal one, is studied by means of the static susceptibility.

D. Davesne; A. Pastore; J. Navarro

2014-02-18

261

Frequency-stepped acquisition in nuclear magnetic resonance spectroscopy under magic angle spinning  

NASA Astrophysics Data System (ADS)

The nuclear magnetic resonance of paramagnetic solids is usually characterized by the presence of large chemical shifts and shift anisotropies due to hyperfine interactions. Frequently the resulting spectra cover a frequency range of several megahertz, which is greater than the bandwidth of commercially available radio-frequency (RF) probes, making it impossible to acquire the whole spectrum in a single experiment. In these cases it common to record a series of spectra, in which the probe is tuned to a different frequency for each, and then sum the results to give the "true" spectrum. While this method is very widely used on static samples, the application of frequency stepping under magic-angle spinning (MAS) is less common, owing to the increased complexity of the spin dynamics when describing the interplay of the RF irradiation with the mechanical rotation of the shift tensor. In this paper, we present a theoretical description, based on the jolting frame formalism of Caravatti et al. [J. Magn. Reson. 55, 88 (1983), 10.1016/0022-2364(83)90279-2], for describing the spin dynamics of a powder sample under MAS when subjected to a selective pulse of low RF-field amplitude. The formalism is used to describe the frequency stepping method under MAS, and under what circumstances the true spectrum is reproduced. We also present an experimental validation of the methodology under ultra-fast MAS with the paramagnetic materials LiMnPO4 and TbCsDPA.

Pell, Andrew J.; Clément, Raphaële J.; Grey, Clare P.; Emsley, Lyndon; Pintacuda, Guido

2013-03-01

262

A high-performance Fortran code to calculate spin- and parity-dependent nuclear level densities  

NASA Astrophysics Data System (ADS)

A high-performance Fortran code is developed to calculate the spin- and parity-dependent shell model nuclear level densities. The algorithm is based on the extension of methods of statistical spectroscopy and implies exact calculation of the first and second Hamiltonian moments for different configurations at fixed spin and parity. The proton-neutron formalism is used. We have applied the method for calculating the level densities for a set of nuclei in the sd-, pf-, and pf+g- model spaces. Examples of the calculations for 28Si (in the sd-model space) and 64Ge (in the pf+g-model space) are presented. To illustrate the power of the method we estimate the ground state energy of 64Ge in the larger model space pf+g, which is not accessible to direct shell model diagonalization due to the prohibitively large dimension, by comparing with the nuclear level densities at low excitation energy calculated in the smaller model space pf. Program summaryProgram title: MM Catalogue identifier: AENM_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AENM_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 193181 No. of bytes in distributed program, including test data, etc.: 1298585 Distribution format: tar.gz Programming language: Fortran 90, MPI. Computer: Any architecture with a Fortran 90 compiler and MPI. Operating system: Linux. RAM: Proportional to the system size, in our examples, up to 75Mb Classification: 17.15. External routines: MPICH2 (http://www.mcs.anl.gov/research/projects/mpich2/) Nature of problem: Calculating of the spin- and parity-dependent nuclear level density. Solution method: The algorithm implies exact calculation of the first and second Hamiltonian moments for different configurations at fixed spin and parity. The code is parallelized using the Message Passing Interface and a master-slaves dynamical load-balancing approach. Restrictions: The program uses two-body interaction in a restricted single-level basis. For example, GXPF1A in the pf-valence space. Running time: Depends on the system size and the number of processors used (from 1 min to several hours).

Sen'kov, R. A.; Horoi, M.; Zelevinsky, V. G.

2013-01-01

263

Radiative Lifetime for Nuclear Spin Conversion of Water-Ion H_2O^+  

NASA Astrophysics Data System (ADS)

Nuclear spin conversion interaction of the water ion, H_2O^+, has been studied to derive the spontaneous emission lifetime between the ortho- and para-levels. The H_2O^+ ion is a radical with ^2 B _1 electronic ground state and the off-diagonal electron spin-nuclear spin interaction term, T_{ab} (S_a? I_b + S_b? I_a), connects para and ortho levels, because ? {I} = {I}_1 - {I}_2 has nonvanishing matrix elements between I = 0 and 1. The T_{ab} coupling constant, derived by an ab initio calculation in MRD-CI/Bk level to be 72 MHz, is larger than that of H_2O by 4 orders of magnitude, makes the ortho to para conversion of H_2O^+ faster than that of H_2O by 8 orders of magnitude and possibly competitive with other astrophysical processes. Last year we reported ortho and para coupling channels below 900 cm^{-1} caused by accidental near degeneracy of rotational levels. For example, hyperfine components of the 4_{2,2}(o) and 3_{3,0}(p) levels mix each other by 1.2 x 10^{-3} due to the near degeneracy (? E = 0.417 cm^{-1}), but the lower lying 1_{0,1}(p) and 1_{1,1}(o) levels mix only by 8.9 x 10^{-5} because of their large separation (? E = 16.27 cm^{-1}). In the present study, we solved the radiative rate equations including all the rotational levels below 900 cm^{-1} to give the o-p conversion lifetime to be 0.451, 3.27, 398 and 910 years for the equilibrium o/p ratio of 3.00, 3.00, 4.52, and 406 when the radiation temperature T_r is 100, 60, 20 and 5 K. These results qualitatively help to understand the observed high o/p ratio of 4.8 ± 0.5 (corresponding to the nuclear spin temperature of 21 K) toward Sgr B2, but they are too slow to compete with the reaction by collision unless the number of density of H_2 in the region is very low (n˜1 cm^{-3}) or the radiative temperature is very high (T_r > 50K). K. Tanaka, K. Harada, and T. Oka, the 67th OSU Symposium MG06, 2012. P. Schilke, et al., A&A 521, L11 (2010). K. Tanaka, K. Harada, and T. Oka, J. Phys. Chem. A, in press.

Tanaka, Keiichi; Harada, Kensuke; Oka, Takeshi

2013-06-01

264

Limits on New Long Range Nuclear Spin-Dependent Forces Set with a K-{sup 3}He Comagnetometer  

SciTech Connect

A magnetometer using spin-polarized K and {sup 3}He atoms occupying the same volume is used to search for anomalous nuclear spin-dependent forces generated by a separate {sup 3}He spin source. We measure changes in the {sup 3}He spin precession frequency with a resolution of 18 pHz and constrain anomalous spin forces between neutrons to be less than 2x10{sup -8} of their magnetic or less than 2x10{sup -3} of their gravitational interactions on a length scale of 50 cm. We present new limits on neutron coupling to light pseudoscalar and vector particles, including torsion, and constraints on recently proposed models involving unparticles and spontaneous breaking of Lorentz symmetry.

Vasilakis, G.; Brown, J. M.; Kornack, T. W.; Romalis, M. V. [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States)

2009-12-31

265

A High-Performance Fortran Code to Calculate Spin- and Parity-Dependent Nuclear Level Densities  

E-print Network

A high-performance Fortran code is developed to calculate the spin- and parity-dependent shell model nuclear level densities.The algorithm is based on the extension of methods of statistical spectroscopy and implies exact calculation of the first and second Hamiltonian moments for different configurations at fixed spin and parity. The proton-neutron formalism is used. We have applied the method for calculating the level densities for a set of nuclei in the sd-, pf-, and pf+g9/2 - model spaces. Examples of the calculations for 28Si (in the sd-model space) and 64Ge (in the pf+g9/2-model space) are presented. To illustrate the power of the method we estimate the ground state energy of 64Ge in the larger model space pf+g9/2, which is not accessible to direct shell model diagonalization due to the prohibitively large dimension, by comparing with the nuclear level densities at low excitation energy calculated in the smaller model space pf.

R. Sen'kov; M. Horoi; V. G. Zelevinsky

2012-06-20

266

Prediction of nuclear spin based on the behavior of ?-particle preformation probability  

NASA Astrophysics Data System (ADS)

A realistic density-dependent nucleon-nucleon (NN) interaction with a finite-range exchange part which produces the nuclear matter saturation curve and the energy dependence of the nucleon-nucleus optical model potential is used to calculate the microscopic ?-nucleus potential in the well-established double-folding model. The main effect of antisymmetrization under exchange of nucleons between the ? and daughter nuclei has been included in the folding model through the finite-range exchange part of the NN interaction. The ?-decay half-lives have been determined using a microscopic potential within the semiclassical Wentzel-Kramers-Brillouin approximation in combination with the Bohr-Sommerfeld quantization condition. We systematically studied the preformation probability, S?, for ten even-even and odd mass heavy nuclei from Po to No isotopes. We found that S? has a regular behavior with N if the ? particle emitted from adjacent isotopes comes from the same energy levels or from a group of levels, assuming that the order of levels in this group is not changed. Sudden increase in S? is found when protons and neutrons holes exist below the Fermi levels. Based on the similarity in the behavior of S? with the neutron number for two adjacent nuclei, we try to determine the unknown or doubted nuclear spins and parities or at least correlate spins of adjacent nuclei.

Ismail, M.; Adel, A.

2013-11-01

267

Spin projection in the shell model Monte Carlo method and the spin distribution of nuclear level densities  

E-print Network

We introduce spin projection methods in the shell model Monte Carlo approach and apply them to calculate the spin distribution of level densities for iron-region nuclei using the complete $(pf+g_{9/2})$-shell. We compare the calculated distributions with the spin-cutoff model and extract an energy-dependent moment of inertia. For even-even nuclei and at low excitation energies, we observe a significant suppression of the moment of inertia and odd-even staggering in the spin dependence of level densities.

Y. Alhassid; S. Liu; H. Nakada

2006-07-27

268

Resonant microwave cavity for 8.512 GHz optically detected electron spin resonance with simultaneous nuclear magnetic resonance  

E-print Network

Resonant microwave cavity for 8.5­12 GHz optically detected electron spin resonance with simultaneous nuclear magnetic resonance J. S. Colton1,a and L. R. Wienkes2 1 Department of Physics online 16 March 2009 We present a newly developed microwave resonant cavity for use in optically detected

Hart, Gus

269

Ortho-para mixing hyperfine interaction in the H2O+ ion and nuclear spin equilibration.  

PubMed

The ortho to para conversion of water ion, H2O(+), due to the interaction between the magnetic moments of the unpaired electron and protons has been theoretically studied to calculate the spontaneous emission lifetime between the ortho- and para-levels. The electron spin-nuclear spin interaction term, Tab(Sa?Ib + Sb?Ia) mixes ortho (I = 1) and para (I = 0) levels to cause the "forbidden" ortho to para |?I| = 1 transition. The mixing term with Tab = 72.0 MHz is 4 orders of magnitude higher for H2O(+) than for its neutral counterpart H2O where the magnetic field interacting with proton spins is by molecular rotation rather than the free electron. The resultant 10(8) increase of ortho to para conversion rate possibly makes the effect of conversion in H2O(+) measurable in laboratories and possibly explains the anomalous ortho to para ratio recently reported by Herschel heterodyne instrument for the far-infrared (HIFI) observation. Results of our calculations show that the ortho ? para mixings involving near-degenerate ortho and para levels are high (?10(-3)), but they tend to occur at high energy levels, ?300 K. Because of the rapid spontaneous emission, such high levels are not populated in diffuse clouds unless the radiative temperature of the environment is very high. The low-lying 101 (para) and 111 (ortho) levels of H2O(+) are mixed by ?10(-4) making the spontaneous emission lifetime for the para 101 ? ortho 000 transition 520 years and 5200 years depending on the F value of the hyperfine structure. Thus the ortho ? para conversion due to the unpaired electron is not likely to seriously affect thermalization of interstellar H2O(+) unless either the radiative temperature is very high or number density of the cloud is very low. PMID:23530629

Tanaka, Keiichi; Harada, Kensuke; Oka, Takeshi

2013-10-01

270

Ortho-Para Mixing Hyperfine Interaction in the H2O+ Ion and Nuclear Spin Equilibration  

NASA Astrophysics Data System (ADS)

The ortho to para conversion of water ion, H2O+, due to the interaction between the magnetic moments of the unpaired electron and protons has been theoretically studied to calculate the spontaneous emission lifetime between the ortho- and para-levels. The electron spin-nuclear spin interaction term, Tab(Sa-Ib + Sb-Ia) mixes ortho (I = 1) and para (I = 0) levels to cause the -forbidden- ortho to para |-I| = 1 transition. The mixing term with Tab = 72.0 MHz is 4 orders of magnitude higher for H2O+ than for its neutral counterpart H2O where the magnetic field interacting with proton spins is by molecular rotation rather than the free electron. The resultant 108 increase of ortho to para conversion rate possibly makes the effect of conversion in H2O+ measurable in laboratories and possibly explains the anomalous ortho to para ratio recently reported by Herschel heterodyne instrument for the far-infrared (HIFI) observation. Results of our calculations show that the ortho - para mixings involving near-degenerate ortho and para levels are high (-10-3), but they tend to occur at high energy levels, -300 K. Because of the rapid spontaneous emission, such high levels are not populated in diffuse clouds unless the radiative temperature of the environment is very high. The low-lying 101 (para) and 111 (ortho) levels of H2O+ are mixed by -10-4 making the spontaneous emission lifetime for the para 101 - ortho 000 transition 520 years and 5200 years depending on the F value of the hyperfine structure. Thus the ortho - para conversion due to the unpaired electron is not likely to seriously affect thermalization of interstellar H2O+ unless either the radiative temperature is very high or number density of the cloud is very low.

Tanaka, Keiichi; Harada, Kensuke; Oka, Takeshi

2013-10-01

271

Possible evidence for helical nuclear spin order in GaAs quantum wires.  

PubMed

We present transport measurements of cleaved edge overgrowth GaAs quantum wires. The conductance of the first mode reaches 2e(2)/h at high temperatures T?10 K, as expected. As T is lowered, the conductance is gradually reduced to 1e(2)/h, becoming T independent at T?0.1 K, while the device cools far below 0.1 K. This behavior is seen in several wires, is independent of density, and not altered by moderate magnetic fields B. The conductance reduction by a factor of 2 suggests lifting of the electron spin degeneracy in the absence of B. Our results are consistent with theoretical predictions for helical nuclear magnetism in the Luttinger liquid regime. PMID:24580700

Scheller, C P; Liu, T-M; Barak, G; Yacoby, A; Pfeiffer, L N; West, K W; Zumbühl, D M

2014-02-14

272

Signal interferences from turbulent spin dynamics in solution nuclear magnetic resonance spectroscopy  

NASA Astrophysics Data System (ADS)

Artifacts arising from aperiodic turbulent spin dynamics in gradient-based nuclear magnetic resonance (NMR) applications are comprehensively surveyed and numerically simulated by a nonlinear Bloch equation. The unexpected dynamics, triggered by the joint action of radiation damping and the distant dipolar field, markedly deteriorate the performance of certain pulse sequences incorporating weak pulsed-field gradients and long evolution times. The effects are demonstrated in three general classes of gradient NMR applications: solvent signal suppression, diffusion measurements, and coherence pathway selection. Gradient-modulated solvent transverse magnetization can be partially rephased in a series of self-refocusing gradient echoes that blank out solute resonances in the CHESS (chemical-shift-selective spectroscopy) and WATERGATE (gradient-tailored water suppression) solvent suppression schemes. In addition, the discovered dynamics contribute to erratic echo attenuation in pulsed gradient spin echo (PGSE) and PGSE stimulated echo diffusion measurements and produce coherence leakage in gradient-selected DQFCOSY and HMQC experiments. Specific remedies for minimizing unwanted effects are presented.

Huang, Susie Y.; Lin, Yung-Ya; Lisitza, Natalia; Warren, Warren S.

2002-06-01

273

Nuclear spin imaging with hyperpolarized nuclei created by brute force method  

NASA Astrophysics Data System (ADS)

We have been developing a polarized HD target for particle physics at the SPring-8 under the leadership of the RCNP, Osaka University for the past 5 years. Nuclear polarizaton is created by means of the brute force method which uses a high magnetic field (~17 T) and a low temperature (~ 10 mK). As one of the promising applications of the brute force method to life sciences we started a new project, "NSI" (Nuclear Spin Imaging), where hyperpolarized nuclei are used for the MRI (Magnetic Resonance Imaging). The candidate nuclei with spin ½hslash are 3He, 13C, 15N, 19F, 29Si, and 31P, which are important elements for the composition of the biomolecules. Since the NMR signals from these isotopes are enhanced by orders of magnitudes, the spacial resolution in the imaging would be much more improved compared to the practical MRI used so far. Another advantage of hyperpolarized MRI is that the MRI is basically free from the radiation, while the problems of radiation exposure caused by the X-ray CT or PET (Positron Emission Tomography) cannot be neglected. In fact, the risk of cancer for Japanese due to the radiation exposure through these diagnoses is exceptionally high among the advanced countries. As the first step of the NSI project, we are developing a system to produce hyperpolarized 3He gas for the diagnosis of serious lung diseases, for example, COPD (Chronic Obstructive Pulmonary Disease). The system employs the same 3He/4He dilution refrigerator and superconducting solenoidal coil as those used for the polarized HD target with some modification allowing the 3He Pomeranchuk cooling and the following rapid melting of the polarized solid 3He to avoid the depolarization. In this report, the present and future steps of our project will be outlined with some latest experimental results.

Tanaka, Masayoshi; Kunimatsu, Takayuki; Fujiwara, Mamoru; Kohri, Hideki; Ohta, Takeshi; Utsuro, Masahiko; Yosoi, Masaru; Ono, Satoshi; Fukuda, Kohji; Takamatsu, Kunihiko; Ueda, Kunihiro; Didelez, Jean-P.; Prossati, Giorgio; de Waard, Arlette

2011-05-01

274

Optically addressable nuclear spins in a solid with a six-hour coherence time.  

PubMed

Space-like separation of entangled quantum states is a central concept in fundamental investigations of quantum mechanics and in quantum communication applications. Optical approaches are ubiquitous in the distribution of entanglement because entangled photons are easy to generate and transmit. However, extending this direct distribution beyond a range of a few hundred kilometres to a worldwide network is prohibited by losses associated with scattering, diffraction and absorption during transmission. A proposal to overcome this range limitation is the quantum repeater protocol, which involves the distribution of entangled pairs of optical modes among many quantum memories stationed along the transmission channel. To be effective, the memories must store the quantum information encoded on the optical modes for times that are long compared to the direct optical transmission time of the channel. Here we measure a decoherence rate of 8 × 10(-5) per second over 100 milliseconds, which is the time required for light transmission on a global scale. The measurements were performed on a ground-state hyperfine transition of europium ion dopants in yttrium orthosilicate ((151)Eu(3+):Y2SiO5) using optically detected nuclear magnetic resonance techniques. The observed decoherence rate is at least an order of magnitude lower than that of any other system suitable for an optical quantum memory. Furthermore, by employing dynamic decoupling, a coherence time of 370 ± 60 minutes was achieved at 2 kelvin. It has been almost universally assumed that light is the best long-distance carrier for quantum information. However, the coherence time observed here is long enough that nuclear spins travelling at 9 kilometres per hour in a crystal would have a lower decoherence with distance than light in an optical fibre. This enables some very early approaches to entanglement distribution to be revisited, in particular those in which the spins are transported rather than the light. PMID:25567283

Zhong, Manjin; Hedges, Morgan P; Ahlefeldt, Rose L; Bartholomew, John G; Beavan, Sarah E; Wittig, Sven M; Longdell, Jevon J; Sellars, Matthew J

2015-01-01

275

Optically addressable nuclear spins in a solid with a six-hour coherence time  

NASA Astrophysics Data System (ADS)

Space-like separation of entangled quantum states is a central concept in fundamental investigations of quantum mechanics and in quantum communication applications. Optical approaches are ubiquitous in the distribution of entanglement because entangled photons are easy to generate and transmit. However, extending this direct distribution beyond a range of a few hundred kilometres to a worldwide network is prohibited by losses associated with scattering, diffraction and absorption during transmission. A proposal to overcome this range limitation is the quantum repeater protocol, which involves the distribution of entangled pairs of optical modes among many quantum memories stationed along the transmission channel. To be effective, the memories must store the quantum information encoded on the optical modes for times that are long compared to the direct optical transmission time of the channel. Here we measure a decoherence rate of 8 × 10-5 per second over 100 milliseconds, which is the time required for light transmission on a global scale. The measurements were performed on a ground-state hyperfine transition of europium ion dopants in yttrium orthosilicate (151Eu3+:Y2SiO5) using optically detected nuclear magnetic resonance techniques. The observed decoherence rate is at least an order of magnitude lower than that of any other system suitable for an optical quantum memory. Furthermore, by employing dynamic decoupling, a coherence time of 370 +/- 60 minutes was achieved at 2 kelvin. It has been almost universally assumed that light is the best long-distance carrier for quantum information. However, the coherence time observed here is long enough that nuclear spins travelling at 9 kilometres per hour in a crystal would have a lower decoherence with distance than light in an optical fibre. This enables some very early approaches to entanglement distribution to be revisited, in particular those in which the spins are transported rather than the light.

Zhong, Manjin; Hedges, Morgan P.; Ahlefeldt, Rose L.; Bartholomew, John G.; Beavan, Sarah E.; Wittig, Sven M.; Longdell, Jevon J.; Sellars, Matthew J.

2015-01-01

276

Solid-State Carbon-13 Nuclear Magnetic Resonance of Humic Acids at High Magnetic Field Strengths  

E-print Network

for cross state 13 C NMR spectra obtained with modern high-field spectrometers, polarization (CP). Similarly magnetic resonance (NMR) spectros- 1 H, 25 MHz 13 C) and low sample reorientation frequen-copy has become NMR spectra of humic acids at high magnetic width of the chemical shift anisotropy (CSA

Hemminga, Marcus A.

277

Carbon-13 nuclear magnetic resonance studies of cobalt transferrin and selected model compounds  

E-print Network

modified form of hen serum transferrin (10)). Mason and Heremans 3+ (26) showed that similar events accompany the binding of Fe 2+ and Cu to lactoferrin, the iron binding protein of milk. Warner and Weber (10) also did some of the earliest quanti... by ultraviolet difference spectroscopy for conalbumin, transferrin, and lactoferrin (17, 34, 35). Tyrosyl groups were considered to be the most likely ligands that were perturbed, and lost protons upon coordination with iron. Electron paramagnetic resonance...

Philen, Rossanne McElroy

2012-06-07

278

Carbon-13 nuclear magnetic resonance studies of metabolism in Crithidia fasciculata  

E-print Network

, the end products of glucose metabolism by C. fasciculara have been reported to be succinate, ethanol, pyruvate and carbon dioxide (CO, ) [67, 6S], with acetic acid mentioned also in one report [70]. Despite the fact that not all of the necessary enzymes.... The first reports of investigations of anaerobic glucose metabolism by C. fascrculara listed ethanol, succinate, lactate and carbon dioxide as the end products [72]. It vras also stated at that time, that glycerol and acetic acid were not present during...

McCloskey, Diane Elizabeth

1986-01-01

279

Carbon-13 nuclear magnetic resonance study of mixed micelles. Variation of interchain distances and conformational equilibria  

SciTech Connect

Observed /sup 13/C NMR chemical shift changes with respect to their single micelles upon mixed-micelle formation of potassium dodecanoate and short-chain potassium carboxylates (hexanoate up to and including decanoate) are described in all but one case to increasing distances between the apolar ends of the long amphiphile chains as compared with its single micelle. Only for dodecanoate-hexanoate micellar systems can a different conformational equilibrium of the dodecanoate chain not be excluded. Furthermore, recently observed solvent effects upon mixing of n-alkanes of different chain lengths are compared with both the decanoate and nonanoate chemical shift changes upon mixing with the dodecanoate amphiphiles. This leads to the conclusion that the former detergents are mainly subject to increased intermolecular chain packing. Observed effects for the octanoate and heptanoate are not as pronounced, and these surfactants should be considered as borderline cases, while the hexanoate undergoes conformational changes toward more extended forms. 46 references.

De Weerd, R.J.E.M.; De Hann, J.W.; Van de Ven, L.J.M.; Achten, M.; Buck, H.M.

1982-06-24

280

A Solid-State Study of a Novel 31P Spin Pair Using Magic-Angle-Spinning Nuclear Magnetic Resonance Spectroscopy  

NASA Astrophysics Data System (ADS)

The present investigation concerns the solid-state nuclear magnetic resonance spectroscopy of the 31P spin pair in the novel three-membered heterocyclic compound 3-(dichloromethylene)- trans-1,2-bis( 2,4,6-tri- tert-butylphenyl)- 1,2-diphosphirane using the magic-angle-spinning (MAS) technique. The homogeneous 31P lineshapes are analyzed to extract the principal components of the shielding tensors using the Maricq and Waugh description of homonuclear spin-pair systems by average-Hamiltonian theory, modified to encompass the n = 0 rotational resonance situation. The experimental values of the shielding-tensor components are compared with those obtained from ab initio calculations performed on the model molecule P 2C 2H 4 to aid further the interpretation of the 31P MAS NMR spectrum of the chloromethylene-diphosphirane. The magnitudes and orientations of calculated shielding-tensor components of the model compound methylene-diphosphirane P 2C 2H 4 are compared with those for the phosphorus spin pair in the molecular environments of P 2, P 2H 2, and P 2H 4. The electronic structures and bonding in all of those molecular species are discussed.

Challoner, R.; Mcdowell, C. A.; Yoshifuji, M.; Toyota, K.; Tossell, J. A.

281

Limitations to carbon 13-labeled urea breath testing for Helicobacter pylori in infants.  

PubMed

We determined the validity of the carbon 13-labeled urea breath test in young children. We found that although the 13C-labeled urea breath test had a specificity greater than 90%, borderline or false positive results occurred more frequently in children younger than 2 years compared with older children. False positive results may be caused by oral-urease-producing organisms because direct intragastric administration of 13C urea reduced the excess delta 13CO2. Care is urged in interpreting one positive 13C-labeled urea breath test in children younger than 2 years. PMID:11713455

Imrie, C; Rowland, M; Bourke, B; Drumm, B

2001-11-01

282

Propagation of dynamic nuclear polarization across the xenon cluster boundaries: elucidation of the spin-diffusion bottleneck.  

PubMed

Earlier Dynamic Nuclear Polarization (DNP) experiments with frozen xenon/1-propanol/trityl mixtures have demonstrated spontaneous formation of pure xenon clusters above 120 K, enabling spectrally-resolved real-time measurements of (129)Xe nuclear magnetization in the clusters and in the surrounding radical-rich matrix. A spin-diffusion bottleneck was postulated to explain the peculiar time evolution of (129)Xe signals in the clusters as well as the apparent discontinuity of (129)Xe polarization across the cluster boundaries. A self-contained ab initio model of nuclear spin diffusion in heterogeneous systems is developed here, incorporating the intrinsic T1 relaxation towards the temperature-dependent equilibrium polarization and the spin-diffusion coefficients based on the measured NMR line widths and the known atomic densities in each compartment. This simple model provides the physical basis for the observed spin-diffusion bottleneck and is in a good quantitative agreement with the earlier measurements. A simultaneous fit of the model to the time-dependent NMR data at two different DNP frequencies provides excellent estimates of the cluster size, the intrinsic sample temperature, and (129)Xe T1 constants. The model was also applied to the NMR data acquired during relaxation towards the thermal equilibrium after the microwaves were turned off, to estimate T1 relaxation time constants inside and outside the clusters. Fitting the model to the data during and after DNP provides consistent estimates of the cluster size. PMID:23981341

Pourfathi, M; Kuzma, N N; Kara, H; Ghosh, R K; Shaghaghi, H; Kadlecek, S J; Rizi, R R

2013-10-01

283

Novel nuclear laser spectroscopy method using superfluid helium for measurement of spins and moments of exotic nuclei  

NASA Astrophysics Data System (ADS)

We have been developing a novel nuclear laser spectroscopy method “OROCHI” for determining spins and moments of exotic radioisotopes. In this method, we use superfluid helium as a stopping material of energetic radioisotope beams and then stopped radioisotope atoms are subjected to in situ laser spectroscopy in superfluid helium. To confirm the feasibility of this method for rare radioisotopes, we carried out a test experiment using a 85Rb beam. In this experiment, we have successfully measured the Zeeman resonance signals from the 85Rb atoms stopped in superfluid helium by laser-RF double resonance spectroscopy. This method is efficient for the measurement of spins and moments of more exotic nuclei.

Furukawa, Takeshi; Wakui, Takashi; Yang, Xiaofei; Fujita, Tomomi; Imamura, Kei; Yamaguchi, Yasuhiro; Tetsuka, Hiroki; Tsutsui, Yoshiki; Mitsuya, Yosuke; Ichikawa, Yuichi; Ishibashi, Yoko; Yoshida, Naoki; Shirai, Hazuki; Ebara, Yuta; Hayasaka, Miki; Arai, Shino; Muramoto, Sosuke; Hatakeyama, Atsushi; Wada, Michiharu; Sonoda, Tetsu; Ito, Yuta; Kobayashi, Tohru; Nishimura, Shunji; Nishimura, Mitsuki; Kondo, Yosuke; Yoneda, Ken-ichiro; Kubono, Shigeru; Ohshiro, Yoshimitsu; Ueno, Hideki; Shinozuka, Tsutomu; Shimoda, Tadashi; Asahi, Koichiro; Matsuo, Yukari

2013-12-01

284

Suppression of nuclear spin diffusion at a GaAs/AlGaAs interface measured with a single quantum dot nano-probe  

E-print Network

Nuclear spin polarization dynamics are measured in optically pumped individual GaAs/AlGaAs interface quantum dots by detecting the time-dependence of the Overhauser shift in photoluminescence (PL) spectra. Long nuclear polarization decay times of ~ 1 minute have been found indicating inefficient nuclear spin diffusion from the GaAs dot into the surrounding AlGaAs matrix in externally applied magnetic field. A spin diffusion coefficient two orders lower than that previously found in bulk GaAs is deduced.

A. E. Nikolaenko; E. A. Chekhovich; M. N. Makhonin; I. W. Drouzas; A. B. Vankov; J. Skiba-Szymanska; M. S. Skolnick; P. Senellart; A. Lemaitre; A. I. Tartakovskii

2009-01-15

285

Microwave field distribution in a magic angle spinning dynamic nuclear polarization NMR probe.  

PubMed

We present a calculation of the microwave field distribution in a magic angle spinning (MAS) probe utilized in dynamic nuclear polarization (DNP) experiments. The microwave magnetic field (B(1S)) profile was obtained from simulations performed with the High Frequency Structure Simulator (HFSS) software suite, using a model that includes the launching antenna, the outer Kel-F stator housing coated with Ag, the RF coil, and the 4mm diameter sapphire rotor containing the sample. The predicted average B(1S) field is 13?T/W(1/2), where S denotes the electron spin. For a routinely achievable input power of 5W the corresponding value is ?(S)B(1S)=0.84MHz. The calculations provide insights into the coupling of the microwave power to the sample, including reflections from the RF coil and diffraction of the power transmitted through the coil. The variation of enhancement with rotor wall thickness was also successfully simulated. A second, simplified calculation was performed using a single pass model based on Gaussian beam propagation and Fresnel diffraction. This model provided additional physical insight and was in good agreement with the full HFSS simulation. These calculations indicate approaches to increasing the coupling of the microwave power to the sample, including the use of a converging lens and fine adjustment of the spacing of the windings of the RF coil. The present results should prove useful in optimizing the coupling of microwave power to the sample in future DNP experiments. Finally, the results of the simulation were used to predict the cross effect DNP enhancement (?) vs. ?(1S)/(2?) for a sample of (13)C-urea dissolved in a 60:40 glycerol/water mixture containing the polarizing agent TOTAPOL; very good agreement was obtained between theory and experiment. PMID:21382733

Nanni, Emilio A; Barnes, Alexander B; Matsuki, Yoh; Woskov, Paul P; Corzilius, Björn; Griffin, Robert G; Temkin, Richard J

2011-05-01

286

Two dimensional 31P nuclear magnetic resonance coherence transfer experiments under magic-angle sample spinning  

NASA Astrophysics Data System (ADS)

In this paper, we report on two dimensional (2D) 31P cross polarization (CP) magic angle spinning (MAS) nuclear magnetic resonance (NMR) experiments on the coupled two-spin systems, sodium pyrophosphate decahydrate, Na4P2O7, 1OH2O (SP) and tetraphenyldiphosphine-1-oxide, (C6H5)2PP(O) (C6H5)2 (TPPO), including antiecho (COSY), double-quantum NMR, and zero-quantum NMR experiments. These experiments are generalizations of the absolute mode 2D Fourier transform antiecho COSY performed under MAS condition by Kentgens, de Boer, and Veeman [J. Chem. Phys. 87, 6859 (1987)]. The 2D sideband intensities for these experiments on polycrystalline samples are shown theoretically to be real. There are two mechanisms of coherence transfer; homonuclear J coupling and dipolar coupling. Theory shows that the zero-quantum signal for the coupled two spins can not be observed by using a (CPx-?-(?)x-?-(?/2)x-t1-(?/2)-t2 pulse sequence, when the coherence transfer is due to J coupling. When, however, the coherence transfer is induced by the flip-flop term of the dipolar coupling Hamiltonian, the zero-quantum signal can be observed by that pulse sequence. The preparation time dependences of the double-quantum and the zero-quantum sideband patterns, are expected, when the coherence transfer is induced by dipolar coupling. The zero-quantum signal was very weak for TPPO, while it was strong for SP. The apparent preparation time dependence of the zero-quantum sideband pattern was observed for SP. These results suggest that the coherence transfer is mainly due to J coupling in TPPO, where the two 31P nuclei have different isotropic chemical shifts. While, on the other hand, the dipolar coupling is more important in SP, where the two 31P nuclei have the same isotropic chemical shifts but different orientations of the chemical shift tensors. The 2D sideband intensities of the antiecho COSY spectrum of TPPO were calculated, and the relative orientation of the two chemical shift tensors was determined.

Kubo, Atsushi; Root, Andrew; McDowell, Charles A.

1990-10-01

287

Optical Hyperpolarization and Detection of Electron and Nuclear Spins of Phosphorus Donors in Highly Enriched Silicon-28  

NASA Astrophysics Data System (ADS)

The linewidths of optical transitions associated with shallow impurities have been shown in recent studies to be much narrower in isotopically enriched 28Si as compared to natural Si. This is true of the no-phonon P donor bound exciton transition in 28Si, and using photoluminescence excitation spectroscopy, fine structure previously not seen in natural Si is revealed. Under a small external magnetic field, the P bound exciton transition shows a complicated structure consisting of six sets of doublets, with the doublet splitting being due to the splitting of the donor ground state by the hyperfine interaction between the spin of the donor electron and that of the 31P nucleus. The electron spin populations and the 31P nuclear spin populations can be determined by measuring the relative intensities of the hyperfine components in the photoluminescence excitation spectrum. Additionally, the predominant Auger recombination channel of these bound excitons is used to observe the same resolved hyperfine components in the photocurrent spectrum. By selectively ionizing donors in a specific hyperfine state via optical pumping of a specific hyperfine component, large polarizations of the electron and nuclear spins of 31P donors can be achieved at low field. Electron and nuclear polarizations of 90% and 76%, respectively, are obtained in less than a second, providing an initialization mechanism for qubits based on these spins, and enabling further ESR and NMR studies on dilute 31P in 28Si. A measurement of the homogeneous linewidth of the transitions associated with the 31P bound exciton, determined by spectral hole burning, is also presented. The observed 10 neV linewidth is only four times the limit set by the bound exciton lifetime.

Yang, Albion

288

Hyperfine transitions in He-like ions as a tool for nuclear-spin-dependent parity-nonconservation studies  

SciTech Connect

In this paper a scheme is proposed for measuring nuclear-spin-dependent parity-nonconservation effects in highly charged ions. The idea is to employ circularly polarized laser light for inducing the transition between the level (1s2s){sup 1}S{sub 0} and the hyperfine sublevels of (1s2s){sup 3}S{sub 1} in He-like ions with nonzero nuclear spin. We argue that an interference between the allowed magnetic dipole M1 and the parity-violating electric dipole E1 decay channel leads to an observable asymmetry of order 10{sup -7} in the transition cross section, in the atomic range 28{<=}Z{<=}35. Experimental requirements for asymmetry measurements are discussed in the case of He-like {sub 34}{sup 77}Se.

Ferro, Fabrizio; Surzhykov, Andrey [Physikalisches Institut, Universitaet Heidelberg (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Stoehlker, Thomas [Physikalisches Institut, Universitaet Heidelberg (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung, Darmstadt (Germany); Helmholtz-Institut Jena, Jena (Germany)

2011-05-15

289

Controlling and exploiting phases in multi-spin systems using electron spin resonance and nuclear magnetic resonance.  

PubMed

The phase of a superposition state is a quintessential characteristic that differentiates a quantum bit of information from a classical one. This phase can be manipulated dynamically or geometrically, and can be exploited to sensitively estimate Hamiltonian parameters, perform faithful quantum state tomography and encode quantum information into multiple modes of an ensemble. Here we discuss the methods that we have employed to manipulate and exploit the phase information of single-, two-, multi-qubit and multi-mode spin systems. PMID:22946041

Simmons, Stephanie; Wu, Hua; Morton, John J L

2012-10-13

290

Development of Unstable Nuclear Beam 17N to Search for High-Spin Isomers in N=51 Isotones  

NASA Astrophysics Data System (ADS)

In order to search for high-spin isomers in N=51 isotones, an unstable nuclear beam 17N was developed using the low-energy radioisotope beam separator(CRIB) of the Center for Nuclear Study(CNS), University of Tokyo, in RIKEN. High-spin isomers in N=83 isotones have been systematically studied. These isomers are of stretch coupled configurations and oblate shape. High-spin isomers of N=51 isotones are expected to be stemmed from the same isomerism appeared in N=83 isotones. Since the nuclei with Z <40 of N=51 isotones are close to the stability line, it is difficult to produce high-spin states in these nuclei using reactions by combinations of stable beams and targets. Therefore, it is very effective to use the radioisotope beam. Experiment was carried out by means of the ? spectroscopy method, Seven ?-rays emitted from Nb nuclei which were produced by the secondary fusion reaction of 82Se + 17N were observed.

Odahara, A.; Gono, Y.; Wakabayashi, Y.; Hokoiwa, N.; Kibe, M.; Fukuchi, T.; Teranishi, T.; Kubono, S.; Notani, M.; Michimasa, S.; He, J. J.; Shimoura, S.; Ideguchi, E.; Yanagisawa, Y.; Watanabe, H.; Kishida, T.; Nishimura, S.; Nishimura, M.; Baba, H.; Iwasaki, H.; Moon, J. Y.; Kato, S.; Sagawa, H.

2004-10-01

291

-Supplementary Material -Electrical read-out of individual nuclear spin trajectories in a single-molecule magnet  

E-print Network

. Terbium Double-Decker 1 S3. Nuclear Spin Read-Out 2 S4. Quantum Tunnelling of Magnetization 3 S5. Quantum magnetic field sweeps in three dimensions at field sweep rates up to 0.2 T/s. S2. TERBIUM DOUBLE-DECKER We used a Terbium (III) bis-phthalocyanine single molecule magnet (SMM), which is a metal-organic com

292

Experimental Investigation of Nuclear Spin Conversion in Interstellar Pre-Cometary Ices  

NASA Astrophysics Data System (ADS)

High resolution infrared spectroscopy of the H2O upsilon(sub)3 band in Comets P/Halley and Wilson has permitted measurement of individual rotational line intensities (Larson et al. 1989). Mumma et al. (1988) suggested that cosmogonic information is preserved in the relative abundances of the nuclear spin species. The H2O molecule is organized into ortho and para species. In order that the total wave function remain symmetric with respect to H atom exchange, o-species have only asymmetric rotational levels, while p-species have only symmetric levels. The lowest ortho level lies 24 cm^-1 (34 degrees K) above the lowest para level, so the ortho/para ratio will be temperature dependent. Above 60 degrees K, o/p achieves the constant statistical equilibrium value of 3/1. Spin species conversion is prohibited by collisional and radiative processes, and requires a strong nonuniform magnetic field. It is hypothesized that cometary water began as a thin layer of ice condensed on grains in cold interstellar molecular clouds. This ice was subject to UV radiation <200 nm, which initially set o/p at ~25 degrees K or below. The grains subsequently accreted to form comets and this o/p was carried into the nucleus and remained unaltered. When the comet becomes active, outbursts emanate from the interior, where the overburden has provided protection from cosmic ray damage. While in the Oort cloud, the outer layers of a comet experience cosmic ray processing that is capable of resetting o/p to the high temperature limit. Thus, a dynamically new comet, such as Wilson, might be expected to show a statistically equilibrated o/p, whereas a short-period comet, such as P/Halley, might show o/p characteristic of its formation. It also appears that D/H in cometary ice was established in interstellar cloud cores, and did not later equilibrate with nebular gas. D/H for Comet P/Halley lies in the range 6-48 x 10^-5 (Eberhardt et al. 1987), much higher than the diffuse ISM, protosolar, Jupiter, and Saturn values (0.5-3.6 x 10^-5). The cometary range is comparable to D/H for Earth (16 x 10^-5) as well as Uranus, Neptune, and Titan, indicating that these bodies acquired their hydrogen in the form of ices as opposed to nebular H2. Similarly, the D/H range for carbonaceous and ordinary chondrites is high (8-105 x 10^-5), and is thought to reflect incorporation of insterstellar material into meteorites (Zinner, 1988). We have developed a novel experimental apparatus to study nuclear spin conversion during formation and processing of thin mantles of water-based ices. Vapor is condensed in a specially designed cryogenic spectroscopy cell that has no paramagnetic surfaces. The cell is attached to the cold head of a closed-cycle He refrigerator, and the entire refrigerator shroud is placed inside an evacuable FTIR spectrometer. Ice samples are held at ~10 degrees K, and irradiated with VUV, thus simulating conditions in the intermediate density regions of interstellar clouds. The ice is then rapidly heated to the sublimation point; temperature during warm up and cool down is controllable to within 1 degree K. The resultant vapor is captured in the cell and the infrared spectrum collected with the FTS. First results from the experimental program will be presented. References: Eberhardt P. et al. (1987) Astron. Astrophys. 187, 481-184. Larson H.P. et al. (1989) Ap. J. 338, 1106-1114. Mumma et al. (1988) Proc. STScI Conference on Origins and Evolution of Planetary Systems. Zinner E. (1988) in Meteorites in the Early Solar System (eds. J.F. Kerridge and M.S. Matthews) pp. 956-983. Univ. Arizona Press, Tucson. AZ.

Broadhurst, C. L.; Mumma, M. J.

1992-07-01

293

Nuclear spin dependence of the reaction of H3+ with H2. II. Experimental measurements  

NASA Astrophysics Data System (ADS)

The nuclear spin dependence of the chemical reaction H_3^+ + H2 ? H2 + H_3^+ has been studied in a hollow cathode plasma cell. Multipass infrared direct absorption spectroscopy has been employed to monitor the populations of several low-energy rotational levels of ortho- and para-H_3^+ (o-H_3^+ and p-H_3^+) in hydrogenic plasmas of varying para-H2 (p-H2) enrichment. The ratio of the rates of the proton hop (kH) and hydrogen exchange (kE) reactions ? ? kH/kE is inferred from the observed p-H_3^+ fraction as a function of p-H2 fraction using steady-state chemical models. Measurements have been performed both in uncooled (Tkin ˜ 350 K) and in liquid-nitrogen-cooled (Tkin ˜ 135 K) plasmas, marking the first time this reaction has been studied at low temperature. The value of ? has been found to decrease from 1.6 ± 0.1 at 350 K to 0.5 ± 0.1 at 135 K.

Crabtree, Kyle N.; Kauffman, Carrie A.; Tom, Brian A.; Beçka, Eftalda; McGuire, Brett A.; McCall, Benjamin J.

2011-05-01

294

Nuclear spin dependence of the reaction of H(3)+ with H2. II. Experimental measurements.  

PubMed

The nuclear spin dependence of the chemical reaction H(3)(+)+ H(2) ? H(2)?+ H(3)(+) has been studied in a hollow cathode plasma cell. Multipass infrared direct absorption spectroscopy has been employed to monitor the populations of several low-energy rotational levels of ortho- and para-H(3)(+) (o-H(3)(+) and p-H(3)(+)) in hydrogenic plasmas of varying para-H(2) (p-H(2)) enrichment. The ratio of the rates of the proton hop (k(H)) and hydrogen exchange (k(E)) reactions ? ? k(H)/k(E) is inferred from the observed p-H(3)(+) fraction as a function of p-H(2) fraction using steady-state chemical models. Measurements have been performed both in uncooled (T(kin) ? 350 K) and in liquid-nitrogen-cooled (T(kin) ? 135 K) plasmas, marking the first time this reaction has been studied at low temperature. The value of ? has been found to decrease from 1.6 ± 0.1 at 350 K to 0.5 ± 0.1 at 135 K. PMID:21599063

Crabtree, Kyle N; Kauffman, Carrie A; Tom, Brian A; Beçka, Eftalda; McGuire, Brett A; McCall, Benjamin J

2011-05-21

295

Magic angle sample spinning sup 13 C nuclear magnetic resonance of isotopically labeled bacteriorhodopsin  

SciTech Connect

Bacteriorhodopsin (bR), the light-driven proton pump protein from Halobacterium halobium, was biosynthetically labeled with (4-{sup 13}C)Asp. The incorporation yield was 48%. The magic angle sample spinning (MASS) {sup 13}C nuclear magnetic resonance (NMR) spectrum of this sample revealed six different peaks superimposed on a broad band of naturally abundant peptide-bond {sup 13}C. Two of the six carbonyl signals can be attributed to internal-protonated Asp carboxyl groups, one of which might be Asp115. An additional resonance at 110 ppm can be associated with the C-11 carbon of Trp, indicating an unusual biosynthetic pathway of this amino acid in Halobacterium halobium. Similar measurements performed on papain-treated purple membrane which lacks the C-terminal tail display two new intense signals at 178 and 178.9 ppm. If the same spectrum is taken without cross-polarization, these signals do not decrease or disappear. On the basis of their intensities and their chemical shifts, one can assign in addition to the C-terminal Asp four Asp residues facing the cytoplasmic phase. In native bR, at least two of these form a salt-bridge-like bond which also might include the C-terminal tail. These experiments not only provide data about the chemical environment of the Asp residues within the hydrophobic core of bacteriorhodopsin but also yield information about the interactions between surface components.

Engelhard, M.; Hess, B.; Emeis, D.; Metz, G.; Kreutz, W.; Siebert, F. (Max-Planck-Institut fuer Ernaehrungsphysiologie, Dortmund (Germany, F.R.))

1989-05-02

296

Intermediate Energy Proton Scattering Studies of CARBON-12 and CARBON-13.  

NASA Astrophysics Data System (ADS)

The ('12)C(p,p') and ('13)C(p,p') reactions have been studied by taking advantage of the high-resolution intermediate energy beams available at the Indiana University Cyclotron Facility. Both reactions were measured at 135 MeV incident energy, and differential cross sections were obtained for ten states of ('12)C between 0 and 19 MeV in excitation, and for thirty-three states of ('13)C between 0 and 23 MeV in excitation. Measurements of the ('13)C((')p,p') reaction at 119 MeV enabled analysing powers to be obtained for some states of ('13)C below 10 MeV in excitation. Phenomenological optical model potentials were obtained to fit the elastic scattering data, both the differential cross sections and analysing powers. The inelastic scattering data were analysed by microscopic distorted-wave calculations, utilizing both free and density dependent parametrizations of the nucleon-nucleon inter- action. A number of nuclear structure models of the normal and non-normal parity states of ('12)C and ('13)C were used. Improved fits to the data were found when a density dependent t-matrix was used. Density dependent effects were particularly evident for the isoscalar natural parity states of ('12)C, in particular the 2('+), T = 0 state at 4.44 MeV for which reliable (large-basis) models of nuclear structure were available. Thus this state provided the best evidence of the necessity to include nuclear medium effects if inelastic proton scattering is to be used as a reliable probe of nuclear structure properties at these energies. By studying different transitions in ('12)C various components of the two-nucleon interaction could be studied. Inadequacies in the small-basis descriptions of the excited states of ('12)C and ('13)C were noted, making plain the need for large-basis shell model calculations of both nuclei. The differential(, )cross sections for the 1/2('-) states of ('13)C(' )at(' )8.86 and 11.08 MeV were very poorly(' )described by the shell model prescription. It is suggested that their structure is predomi- nantly that of a 1p(,1/2) neutron coupled to the 0('+), T = 0 state of ('12)C at 7.65 MeV. For states above 11.5 MeV in excitation in ('13)C, interest was turned to seeking spins and parities where these were unknown. The state at 11.85 MeV was assigned 7/2('+).

Collins, Stephen Frederick

297

Flexible nuclear screening approximation to the two-electron spin–orbit coupling based on ab initio parameterization  

SciTech Connect

The derivation, implementation, and validation of a new approximation to the two-electron spin–orbit coupling (SOC) terms is reported. The approximation, referred to as flexible nuclear screening spin–orbit, is based on the effective one-electron spin–orbit operator and accounts for two-electron SOC effects by screening nuclear charges. A highly flexible scheme for the nuclear screening is developed, mainly using parameterization based on ab initio atomic SOC calculations. Tabulated screening parameters are provided for contracted and primitive Gaussian-type basis functions of the ANO-RCC basis set for elements from H to Cm. The strategy for their adaptation to any other Gaussian basis set is presented and validated. A model to correct for the effect of splitting of transition metal d orbitals on their SOC matrix elements is introduced. The method is applied to a representative set of molecules, and compared to exact treatment and other approximative approaches at the same level of relativistic theory. The calculated SOC matrix elements are in very good agreement with their “exact” values; deviation below 1% is observed on average. The presented approximation is considered to be generally applicable, simple to implement, highly efficient, and accurate.

Chalupský, Jakub, E-mail: jakub@ims.ac.jp; Yanai, Takeshi [Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, Okazaki, Aichi 444-8585 (Japan)] [Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, Okazaki, Aichi 444-8585 (Japan)

2013-11-28

298

Quantum state tomography of large nuclear spins in a semiconductor quantum well: Robustness against errors as quantified by condition numbers  

E-print Network

We discuss methods of quantum state tomography for solid-state systems with a large nuclear spin $I=3/2$ in nanometer-scale semiconductors devices based on a quantum well. Due to quadrupolar interactions, the Zeeman levels of these nuclear-spin devices become nonequidistant, forming a controllable four-level quantum system (known as quartit or ququart). The occupation of these levels can be selectively and coherently manipulated by multiphoton transitions using the techniques of nuclear magnetic resonance (NMR) [Yusa et al., Nature (London) 434, 101 (2005)]. These methods are based on an unconventional approach to NMR, where the longitudinal magnetization $M_z$ is directly measured. This is in contrast to the standard NMR experiments and tomographic methods, where the transverse magnetization $M_{xy}$ is detected. The robustness against errors in the measured data is analyzed by using condition numbers. We propose several methods with optimized sets of rotations. The optimization is applied to decrease the number of NMR readouts and to improve the robustness against errors, as quantified by condition numbers. An example of state reconstruction, using Monte Carlo methods, is presented. Tomographic methods for quadrupolar nuclei with higher-spin numbers (including $I=7/2$) are also described.

Adam Miranowicz; Sahin K. Ozdemir; Jiri Bajer; Go Yusa; Nobuyuki Imoto; Yoshiro Hirayama; Franco Nori

2014-10-09

299

Theoretical prediction of nuclear magnetic shieldings and indirect spin-spin coupling constants in 1,1-, cis-, and trans-1,2-difluoroethylenes  

SciTech Connect

A theoretical prediction of nuclear magnetic shieldings and indirect spin-spin coupling constants in 1,1-, cis- and trans-1,2-difluoroethylenes is reported. The results obtained using density functional theory (DFT) combined with large basis sets and gauge-independent atomic orbital calculations were critically compared with experiment and conventional, higher level correlated electronic structure methods. Accurate structural, vibrational, and NMR parameters of difluoroethylenes were obtained using several density functionals combined with dedicated basis sets. B3LYP/6-311++G(3df,2pd) optimized structures of difluoroethylenes closely reproduced experimental geometries and earlier reported benchmark coupled cluster results, while BLYP/6-311++G(3df,2pd) produced accurate harmonic vibrational frequencies. The most accurate vibrations were obtained using B3LYP/6-311++G(3df,2pd) with correction for anharmonicity. Becke half and half (BHandH) density functional predicted more accurate {sup 19}F isotropic shieldings and van Voorhis and Scuseria's ?-dependent gradient-corrected correlation functional yielded better carbon shieldings than B3LYP. A surprisingly good performance of Hartree-Fock (HF) method in predicting nuclear shieldings in these molecules was observed. Inclusion of zero-point vibrational correction markedly improved agreement with experiment for nuclear shieldings calculated by HF, MP2, CCSD, and CCSD(T) methods but worsened the DFT results. The threefold improvement in accuracy when predicting {sup 2}J(FF) in 1,1-difluoroethylene for BHandH density functional compared to B3LYP was observed (the deviations from experiment were ?46 vs. ?115 Hz)

Nozirov, Farhod, E-mail: teobaldk@gmail.com, E-mail: farhod.nozirov@gmail.com [Department of Physics, 4513 Manhattan College Parkway Riverdale, New York 10471 (United States)] [Department of Physics, 4513 Manhattan College Parkway Riverdale, New York 10471 (United States); Stachów, Micha?, E-mail: michal.stachow@gmail.com [Faculty of Chemistry, Opole University, 48, Oleska Street, 45-052 Opole (Poland)] [Faculty of Chemistry, Opole University, 48, Oleska Street, 45-052 Opole (Poland); Kupka, Teobald, E-mail: teobaldk@gmail.com, E-mail: farhod.nozirov@gmail.com

2014-04-14

300

Nuclear Spin-Lattice Relaxation Times from Continuous Wave NMR Spectroscopy.  

ERIC Educational Resources Information Center

The experiment described, suitable for undergraduate physical chemistry laboratories, illustrates the general principles of relaxation and introduces the nmr concepts of saturation and spin-inversion. (BB)

Wooten, Jan B.; And Others

1979-01-01

301

Chain configuration and flexibility gradient in phospholipid membranes. Comparison between spin-label electron spin resonance and deuteron nuclear magnetic resonance, and identification of new conformations.  

PubMed Central

The electron spin resonance spectra of 1-myristoyl-2-[n-(4,4-dimethyloxazolidine-N-oxyl)myristoyl]-sn- glycero-3-phosphocholine spin-label positional isomers (n = 6, 10, and 13) have been studied in oriented, fully hydrated bilayers of dimyristoylphosphatidylcholine, as a function of temperature and magnetic field orientation. The spectra have been simulated using a line-shape model which incorporates chain rotational isomerism, as well as restricted anisotropic motion of the lipid molecules as a whole, and which is valid in all motional regimes of conventional spin-label electron spin resonance (ESR) spectroscopy. At least one component of the lipid motion is found to lie in the slow-motion regime for all label positions, even in the fluid liquid crystalline phase, well above the phase transition. In the gel phase, the chain isomerism lies in the slow-motional regime, and the overall motions are at the rigid-limit. In the fluid phase, the chain isomerism is in the fast-motional regime, and the chain axis motions are in the slow regime. This indicates that the commonly used motional-narrowing theory is not appropriate for the interpretation of spin-label spectra in biological membranes. The simulation parameters yield a consistent description for the chain order and dynamics for all label positions. The correlation times and order parameters for the overall motion are the same at all positions down the chain, whereas the chain conformation and trans-gauche isomerism rate display a characteristic flexibility gradient, with increasing motion towards the terminal methyl end of the chain. Significantly, it is found that all six distinct tetrahedral orientations of the hyperfine tensor at the labeled segment are required for a consistent description of the chain isomerism. For the C-6 segment only the 0 degree (trans) and two 60 degrees (gauche) orientations are significantly populated, for the C-10 position two further 60 degrees orientations are populated, and for the C-13 position all orientations have non-vanishing populations. Detailed comparisons have been made with the results of 2H nuclear magnetic resonance (NMR) measurements on dimyristoylphosphatidylcholine labeled at the same position in the sn-2 chain, and using an identical motional model. The parameters of overall reorientation, both order parameter and correlation times, have very similar values as determined by ESR and NMR. The major difference between the results from the two methods lies in the conformational populations at the labeled chain segment and the trans-gauche isomerization rate in the gel phase. The conformational order is much lower for the spin-labeled chain segments than for the corresponding deuterium-labeled segments, and the isomer interconversion rates in the gel phase(although displaying a mobility gradient in both cases) are found to be much slower in the former case. In addition the spin-label measurements provide information on the macro order (chain tilt), which is only available from oriented samples. These results are consistent between the different spin label positions and are in agreement with the findings from x-ray diffraction. PMID:2539207

Moser, M.; Marsh, D.; Meier, P.; Wassmer, K. H.; Kothe, G.

1989-01-01

302

Landau-Zener tunneling of a single Tb3+ magnetic moment allowing the electronic read-out of a nuclear spin  

NASA Astrophysics Data System (ADS)

A multiterminal device based on a carbon nanotube quantum dot was used at very low temperature to probe a single electronic and nuclear spin embedded in a bis-(phthalocyaninato) terbium (III) complex (TbPc2). A spin-valve signature with large conductance jumps was found when two molecules were strongly coupled to the nanotube. The application of a transverse field separated the magnetic signal of both molecules and enabled single-shot read-out of the terbium nuclear spin. The Landau-Zener (LZ) quantum tunneling probability was studied as a function of field sweep rate, establishing a good agreement with the LZ equation and yielding the tunnel splitting ?. It was found that ? increased linearly as a function of the transverse field. These studies are an essential prerequisite for the coherent manipulation of a single nuclear spin in TbPc2.

Urdampilleta, M.; Klyatskaya, S.; Ruben, M.; Wernsdorfer, W.

2013-05-01

303

Theory of long-lived nuclear spin states in methyl groups and quantum-rotor induced polarisation  

NASA Astrophysics Data System (ADS)

Long-lived nuclear spin states have a relaxation time much longer than the longitudinal relaxation time T1. Long-lived states extend significantly the time scales that may be probed with magnetic resonance, with possible applications to transport and binding studies, and to hyperpolarised imaging. Rapidly rotating methyl groups in solution may support a long-lived state, consisting of a population imbalance between states of different spin exchange symmetries. Here, we expand the formalism for describing the behaviour of long-lived nuclear spin states in methyl groups, with special attention to the hyperpolarisation effects observed in 13CH3 groups upon rapidly converting a material with low-barrier methyl rotation from the cryogenic solid state to a room-temperature solution [M. Icker and S. Berger, J. Magn. Reson. 219, 1 (2012)]. We analyse the relaxation properties of methyl long-lived states using semi-classical relaxation theory. Numerical simulations are supplemented with a spherical-tensor analysis, which captures the essential properties of methyl long-lived states.

Dumez, Jean-Nicolas; Hâkansson, Pär; Mamone, Salvatore; Meier, Benno; Stevanato, Gabriele; Hill-Cousins, Joseph T.; Roy, Soumya Singha; Brown, Richard C. D.; Pileio, Giuseppe; Levitt, Malcolm H.

2015-01-01

304

Theory of long-lived nuclear spin states in methyl groups and quantum-rotor induced polarisation.  

PubMed

Long-lived nuclear spin states have a relaxation time much longer than the longitudinal relaxation time T1. Long-lived states extend significantly the time scales that may be probed with magnetic resonance, with possible applications to transport and binding studies, and to hyperpolarised imaging. Rapidly rotating methyl groups in solution may support a long-lived state, consisting of a population imbalance between states of different spin exchange symmetries. Here, we expand the formalism for describing the behaviour of long-lived nuclear spin states in methyl groups, with special attention to the hyperpolarisation effects observed in (13)CH3 groups upon rapidly converting a material with low-barrier methyl rotation from the cryogenic solid state to a room-temperature solution [M. Icker and S. Berger, J. Magn. Reson. 219, 1 (2012)]. We analyse the relaxation properties of methyl long-lived states using semi-classical relaxation theory. Numerical simulations are supplemented with a spherical-tensor analysis, which captures the essential properties of methyl long-lived states. PMID:25637994

Dumez, Jean-Nicolas; Håkansson, Pär; Mamone, Salvatore; Meier, Benno; Stevanato, Gabriele; Hill-Cousins, Joseph T; Roy, Soumya Singha; Brown, Richard C D; Pileio, Giuseppe; Levitt, Malcolm H

2015-01-28

305

Nuclear spin-dependent interactions: Searches for WIMP, Axion and Topological Defect Dark Matter, and Tests of Fundamental Symmetries  

E-print Network

We calculate the proton and neutron spin contributions for nuclei using semi-empirical methods, as well as a novel hybrid \\emph{ab initio}/semi-empirical method, for interpretation of experimental data. We demonstrate that core-polarisation corrections to \\emph{ab initio} nuclear shell model calculations generally reduce discrepancies in proton and neutron spin expectation values from different calculations. We derive constraints on the spin-dependent P,T-violating interaction of a bound proton with nucleons, which for certain ranges of exchanged pseudoscalar boson masses improve on the most stringent laboratory limits by several orders of magnitude. We derive a limit on the CPT and Lorentz-invariance-violating parameter $|\\tilde{b}_{\\perp}^p| analysis of nuclear anapole moment data for Cs to obtain new limits on several other CPT and Lorentz-invariance-violating parameters: $\\left|b_0^p \\right| < 7 \\times 10^{-8}$ GeV, $\\left|d_{00}^p \\right| < 8 \\times 10^{-8}$, $\\left|b_0^n \\right| < 3 \\times 10^{-7}$ GeV and $\\left|d_{00}^n \\right| < 3 \\times 10^{-7}$.

Y. V. Stadnik; V. V. Flambaum

2015-01-22

306

High-resolution nuclear magnetic resonance spectroscopy of biological tissues using projected magic angle spinning.  

PubMed

High-resolution NMR spectra of materials subject to anisotropic broadening are usually obtained by rotating the sample about the magic angle, which is 54.7 degrees to the static magnetic field. In projected magic angle spinning (p-MAS), the sample is spun about two angles, neither of which is the magic angle. This provides a method of obtaining isotropic spectra while spinning at shallow angles. The p-MAS experiment may be used in situations where spinning the sample at the magic angle is not possible due to geometric or other constraints, allowing the choice of spinning angle to be determined by factors such as the shape of the sample, rather than by the spin physics. The application of this technique to bovine tissue samples is demonstrated as a proof of principle for future biological or medical applications. PMID:16032677

Martin, Rachel W; Jachmann, Rebecca C; Sakellariou, Dimitris; Nielsen, Ulla Gro; Pines, Alexander

2005-08-01

307

Unraveling multi-spin effects in rotational resonance nuclear magnetic resonance using effective reduced density matrix theory  

SciTech Connect

A quantum-mechanical model integrating the concepts of reduced density matrix and effective Hamiltonians is proposed to explain the multi-spin effects observed in rotational resonance (R{sup 2}) nuclear magnetic resonance (NMR) experiments. Employing this approach, the spin system of interest is described in a reduced subspace inclusive of its coupling to the surroundings. Through suitable model systems, the utility of our theory is demonstrated and verified with simulations emerging from both analytic and numerical methods. The analytic results presented in this article provide an accurate description/interpretation of R{sup 2} experimental results and could serve as a test-bed for distinguishing coherent/incoherent effects in solid-state NMR.

SivaRanjan, Uppala; Ramachandran, Ramesh, E-mail: rramesh@iisermohali.ac.in [Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Manauli, P.O. Box-140306, Mohali, Punjab (India)] [Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector 81, Manauli, P.O. Box-140306, Mohali, Punjab (India)

2014-02-07

308

Spin density wave and superconductivity in CaFe1-xCoxAsF studied by nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

We performed nuclear magnetic resonance measurements to investigate the evolution of spin-density-wave (SDW) and superconducting (SC) states upon electron doping in CaFe1-xCoxAsF, which exhibits an intermediate phase diagram between those of LaFeAsO1-xFx and Ba(Fe1-xCox)2As2. We found that homogeneous coexistence of the incommensurate SDW and SC states occurs only in a narrow doping region around the crossover regime, which supports S+--wave symmetry. However, only the structural phase transition survives upon further doping, which agrees with predictions from orbital fluctuation theory. The transitional features upon electron doping imply that both spin and orbital fluctuations are involved in the superconducting mechanism.

Tsutsumi, S.; Fujiwara, N.; Matsuishi, S.; Hosono, H.

2012-08-01

309

Growth of semiconductor nanostructures by MBE for the study of electron and nuclear spin enhancement and other physical phenomena  

NASA Astrophysics Data System (ADS)

Molecular beam epitaxy (MBE) is an extremely versatile thin film technique, which can produce single-crystal layers with atomic dimensional controls and thus permit the preparation of novel structures and devices tailored to meet specific needs. Spin relaxation time ts is one of the key features in spin-related phenomena and thus of great importance for spintronics. In this work, we prepare high quality samples, mainly of CdTe epilayers, by MBE, characterize their spin relaxation dynamics, and discuss the results theoretically. First, with the goal of understanding the mechanisms of electron relaxation dynamics and nuclear spin enhancement, we focus on the growth and characterization of CdTe epilayers. By changing the shutter sequences and inserting ZnSe buffer layer, we have reproducibly grown (111) and (100) CdTe epilayers of high crystalline qualities by MBE, despite the large lattice mismatch between CdTe and GaAs substrate. Then we investigate ts for the (111) and (100) CdTe epilayers. It is found that for the (111) CdTe, spin relaxation rate t-1s is significantly enhanced and shows no temperature dependence through 130K to 300K, while t-1s for the (100) CdTe is strongly affected by the temperature. It is also found that t-1s is dependent on material quality for both (111) and (100) CdTe. We theoretically discuss the effect of strain and defect on spin relaxation time of CdTe. It is the first experimental observation of the effect of strain on t-1s in a II-VI semiconductor material. Second, the growth and characterization of ZnTe/ZnSe related type II quantum structures, or quantum dots (QDs), are also presented in this work. The PL of Zn-Se-Te related type II quantum structures show blue shifts with higher intensities of exciting laser, an indication of type II QDs. Besides being an attractive method to p-type dope wide bandgap materials, the resulting material may be a promising structure for spin enhancement properties. Third, we present the study of the enhancement of nuclear spin polarization through pumping laser. We find strong enhancement both in bulk CdTe as well as in CdTe epilayers, independent of the helicity of the laser, which is on the contrary to the prior reports by others. Compared with GaAs crystal, we ascribe this independence to the surface spin-dependent recombination. GaAs/AlAs and GaAs/GaAlAs multiple coupled double quantum wells (QWs), and CdTe/CdMgTe QW have also been grown and explored. The measurements show good quality of the material and are consistent with the designed structures. Last, we summary the work and propose the future directions. Samples are in-situ monitored by reflection high energy electron diffraction (RHEED). Post growth characterization techniques, such as time resolved Kerr rotation (TRKR), X-ray diffraction (XRD), photoluminescence (PL), and optical pumping nuclear magnetic resonance (OPNMR), are introduced and applied to the samples.

Zhang, Qiang

310

Anisotropic 2H-nuclear magnetic resonance spin-lattice relaxation in cerebroside- and phospholipid-cholesterol bilayer membranes.  

PubMed Central

The axially symmetric powder pattern 2H-nuclear magnetic resonance (NMR) lineshapes observed in the liquid crystalline phase of pure lipid or lipid/cholesterol bilayers are essentially invariant to temperature, or, equivalently, to variations in the correlation times characterizing C-2H bond reorientations. In either of these melted phases, where correlation times for C-2H bond motions are shorter than 10(-7) s, information on the molecular dynamics of the saturated hydrocarbon chain would be difficult to obtain using lineshape analyses alone, and one must resort to other methods, such as the measurement of 2H spin-lattice relaxation rates, in order to obtain dynamic information. In pure lipid bilayers, the full power of the spin-lattice relaxation technique has yet to be realized, since an important piece of information, namely the orientation dependence of the 2H spin-lattice relaxation rates is usually lost due to orientational averaging of T1 by rapid lateral diffusion. Under more favorable circumstances, such as those encountered in the lipid/cholesterol mixtures of this study, the effects of orientational averaging by lateral diffusion are nullified, due to either a marked reduction (by at least an order of magnitude) in the diffusion rate, or a marked increase in the radii of curvature of the liposomes. In either case, the angular dependence of 2H spin-lattice relaxation is accessible to experimental study, and can be used to test models of molecular dynamics in these systems. Simulations of the partially recovered lineshapes indicate that the observed T1 anisotropies are consistent with large amplitude molecular reorientation of the C-2H bond among a finite number of sites. Furthermore, from the observed orientation dependence of the 2H spin-lattice relaxation rates, we conclude that order director fluctuations cannot provide the dominant relaxation pathway for acyl chain deuterons. PMID:3207831

Siminovitch, D. J.; Ruocco, M. J.; Olejniczak, E. T.; Das Gupta, S. K.; Griffin, R. G.

1988-01-01

311

Relativistic nuclear corrections to the spin structure function of the deuteron in the light-cone variables  

SciTech Connect

The relativistic deuteron has been considered in the light-cone formalism as a system of two strongly interacting nucleons (two-nucleon approximation). The technique for the calculation of the average helicity of the proton in the deuteron has been considered in the light-cone variables. A receipt has been pro-posed for the consistent calculation of relativistic nuclear corrections to the average helicity of the proton in the deuteron and to the spin structure function of the deuteron g{sub 1}{sup D}. Relativistic-correction-induced change in the Bjorken sum rule has been discussed.

Pavlov, F. F., E-mail: f.pavlov@tuexph.stu.neva.ru [St. Petersburg State Polytechnic University (Russian Federation)

2012-06-15

312

Body-fixed relativistic molecular Hamiltonian and its application to nuclear spin-rotation tensor: Linear molecules  

NASA Astrophysics Data System (ADS)

The relativistic molecular Hamiltonian written in the body-fixed frame of reference is the basis for high-precision calculations of spectroscopic parameters involving nuclear vibrations and/or rotations. Such a Hamiltonian that describes electrons fully relativistically and nuclei quasi-relativistically is just developed for semi-rigid nonlinear molecules [Y. Xiao and W. Liu, J. Chem. Phys. 138, 134104 (2013)], 10.1063/1.4797496. Yet, the formulation should somewhat be revised for linear molecules thanks to some unusual features arising from the redundancy of the rotation around the molecular axis. Nonetheless, the resulting isomorphic Hamiltonian is rather similar to that for nonlinear molecules. Consequently, the relativistic formulation of nuclear spin-rotation (NSR) tensor for linear molecules is very much the same as that for nonlinear molecules. So is the relativistic mapping between experimental NSR and NMR.

Xiao, Yunlong; Liu, Wenjian

2013-07-01

313

Curing chemistry of phenylethynyl-terminated imide oligomers: Model compounds, carbon-13 labeling and cure analysis  

NASA Astrophysics Data System (ADS)

Phenylethynyl-terminated imide oligomers (PETI) are currently considered the state-of-the-art high performance resins for aerospace applications. The processing of these resins is more facile because of their low molecular weight, but PETI's cure to form a tough, solvent-resistant material. However, the final cure structure was a complete mystery. Hence, the present study was set forth with three essential goals. The determination of the final structure of the crosslinked polymer is of obvious importance. Second, the crosslinking mechanism and controlling factors is also of interest. Lastly, the final structure of the crosslinked polymers was correlated with mechanical and thermal properties, thereby helping to establish the structure-processing-properties relationships for PETI resins. These goals were accomplished by using a combination of synthesis of model compounds synthesis and proposed cure products, sp{13}C labeling of the ethynyl endgroup in PETI's, monitoring of the thermal cure using solid state sp{13}C NMR and ESR and molecular modeling techniques. Phenylethynyl endcapping agents, 4-(phenylethynyl)phthalic anhydride (PEPA) and 3-(phenylethynyl)aniline (3PEA), were synthesized via the palladium-catalyzed coupling of phenylacetylene with 4-bromophthalic anhydride or 3-iodonitrobenzene followed by reduction to 3PEA, respectively. Isolated yields of 41 and 86% for 3PEA and PEPA were obtained, respectively. Model compounds were synthesized from 3PEA and PEPA by reacting with them the appropriate aniline or phthalic anhydride derivative. Model compounds included N-pentafluorophenyl-4-(phenylethynyl)phthalimide (PEPA/F5An), N-(4-trifluoromethyl-phenyl)4-(phenylethynyl)phthalimide (PEPA/F3CAn), N-lbrack 3-(phenylethynyl)phenylrbrack\\ phthalimide (3PEA/PA), N-phenyl-4-(phenylethynyl)phthalimide (PEPA/An), N-(4-phenoxyphenyl)4-(phenylethynyl)phthalimide (PEPA/POAn), and N-(1-naphthyl)-4-(phenylethynyl)phthalimide (PEPA/Anaph). Proposed cure products such as cyclotrimers and linear oligomers (polyenes) were also synthesized from PEPA/An and analyzed in terms of spectroscopic and thermal properties. The conversion of alpha,beta-sp{13}C-acetophenone to alpha,beta-sp{13}C-phenylacetylene using a LDA/phosphate ester procedure was readily accomplished, and following a silver salt purification, the labeled enylacetylene was immediately reacted with 4-bromophthalic anhydride under Heck coupling conditions. A 29% yield of recrystallized 4-(phenylethynyl-alpha,beta-sp{13}Csb2)phthalic anhydride was obtained based on acetophenone. By adjusting the stoichiometry, sp{13}C labeled phenylethynyl-terminated imide oligomers (PETI) were synthesized with Msb{n} of 2,000 to 9,000 daltons. The thermal curing of PETI's and model compounds was monitored via solid state sp{13}C nuclear magnetic resonance, electron spin resonance spectroscopy and differential scanning calorimetry. Using solid state sp{13}C NMR, several cure products were identified. The effects of post-curing and oligomer chain length on the final structure of the cured resins were also examined. Electron spin resonance spectra were obtained on unlabeled PETI's before and after heating at 250-410sp°C. ESR signals suggest that the curing of these resins involves a carbon centered radical. The cure parameters of model compounds as determined by DSC were tabulated and compared. Molecular mechanics and semi-empirical calculations were employed to calculate theoretical bond orders, ionization potentials, HOMO-LUMO gaps, point charges and molecular volumes. The cure profiles of the model compounds were rationalized using these molecular parameters. All of the present data is consistent with the proposed curing mechanisms and cure products. The dominant factors include the chain length of the reactive oligomer, the backbone structure and steric hindrance around the ethynyl group. Although less defined, the electronics and flexibility around the ethynyl group also appear to be factors in determining the structure of the cured resin. In addition, several relationships between the fina

Roberts, Christopher Chad

1998-11-01

314

Rotor-driven spin diffusion in natural-abundance 13C spin systems  

NASA Astrophysics Data System (ADS)

A novel method for enhancing carbon spin diffusion in magic-angle spinning NMR experiments of solid samples is presented. The energy balance for the flip-flop process of two carbon-13 spins is provided by coupling to the mechanical rotation of the sample. Thus requires that the rotor frequency is adjusted to an integer fraction of the isotropic chemical shift difference between two particular carbon resonances. The spin-diffusion rate constant is found to be enhanced by more than two orders of magnitude in threonine with natural isotopic abundance.

Colombo, M. G.; Meier, B. H.; Ernst, R. R.

1988-05-01

315

The importance of nuclear spin diffusion as an angularly independent relaxation mechanism controlling the matrix ENDOR response of radicals in molecular crystals  

SciTech Connect

In the generalized matrix ENDOR line shape model (P.A. Narayana et al., J. Chem. Phys., 67, 1990 (1977)) the ENDOR intensity is controlled by the nuclear spin lattice relaxation rate formulated as an angularly dependent electron-nuclear dipolar contribution and an angularly independent intrinsic bulk nuclear relaxation contribution. Comparison of this model with single crystal data (L. Kevan et al., J. Chem. Phys., 70, 5006 (1979)) showed that the angularly independent relaxation rate must be more rapid than the intrinsic bulk nuclear relaxation rate. Here we identify the angularly independent relaxation rate with nuclear spin diffusion and apply this interpretation quantitatively to data on methyl radicals in lithium acetate dihydrate crystals and to the radiation generated CH/sub 3/CH(NH/sub 3/)COOH/sup -/ radical in alanine at 77 K.

Schlick, S.; Kevan, L.; Toriyama, K.; Iwasaki, M.

1981-01-01

316

Utilization of site-directed spin labeling and high-resolution heteronuclear nuclear magnetic resonance for global fold determination of large proteins with limited nuclear overhauser effect data.  

PubMed

To test whether distances derived from paramagnetic broadening of (15)N heteronuclear single quantum coherence (HSQC) resonances could be used to determine the global fold of a large, perdeuterated protein, we used site-directed spin-labeling of 5 amino acids on the surface of (15)N-labeled eukaryotic translation initiation factor 4E (eIF4E). eIF4E is a 25 kDa translation initiation protein, whose solution structure was previously solved in a 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate hydrate (CHAPS) micelle of total molecular mass approximately 45-50 kDa. Distance-dependent line broadening consistent with the three-dimensional structure of eIF4E was observed for all spin-label substitutions. The paramagnetic broadening effects (PBEs) were converted into distances for modeling by a simple method comparing peak heights in (15)N-HSQC spectra before and after reduction of the nitroxide spin label with ascorbic acid. The PBEs, in combination with HN-HN nuclear Overhauser effects (NOEs) and chemical shift index (CSI) angle restraints, correctly determined the global fold of eIF4E with a backbone precision of 2.3 A (1.7 A for secondary structure elements). The global fold was not correctly determined with the HN-HN NOEs and CSI angles alone. The combination of PBEs with simulated restraints from another nuclear magnetic resonance (NMR) method for global fold determination of large proteins (methyl-protonated, highly deuterated samples) improved the quality of calculated structures. In addition, the combination of the two methods simulated from a crystal structure of an all alpha-helical protein (40 kDa farnesyl diphoshphate synthase) correctly determined the global fold where neither method individually was successful. These results show the potential feasibility of obtaining medium-resolution structures for proteins in the 40-100 kDa range via NMR. PMID:10820006

Battiste, J L; Wagner, G

2000-05-01

317

31P nuclear magnetic resonance studies of crayfish (Orconectes virilis). The use of inversion spin transfer to monitor enzyme kinetics in vivo.  

PubMed

31P nuclear-magnetic resonance (NMR) has been used to observed in vivo the steady-state levels of phosphorus-containing metabolites in the crayfish Orconectes virilis and the intracellular pH of the abdominal muscle was determined. Measurement of spin-lattice relaxation times and spin transfer experiments have enabled calculation of unidirectional rate constants and activation energies for the arginine kinase reaction in vivo. PMID:3996405

Butler, K W; Deslauriers, R; Geoffrion, Y; Storey, J M; Storey, K B; Smith, I C; Somorjai, R L

1985-05-15

318

Solid state 31P cross-polarization/magic angle sample spinning nuclear magnetic resonance studies of crystalline glycogen phosphorylase b  

PubMed Central

31P cross-polarization/magic angle sample spinning nuclear magnetic resonance spectra have been obtained for pyridoxal 5?-phosphate (PLP) bound to glycogen phosphorylase b (GPb) in two different crystalline forms, monoclinic and tetragonal. Analysis of the intensities of the spinning sidebands in the nuclear magnetic resonance spectra has enabled estimates of the principal values of the 31P chemical shift tensors to be obtained. Differences between the two sets of values suggest differences in the environment of the phosphate moiety of the pyridoxal phosphate in the two crystalline forms. The tensor for the tetragonal crystalline form, T state GPb, is fully consistent with those found for dianionic phosphate groups in model compounds. The spectrum for the monoclinic crystalline form, R state GPb, although closer to that of dianionic than monoanionic model phosphate compounds, deviates significantly from that expected for a simple dianion or monoanion. This is likely to result from specific interactions between the PLP phosphate group and residues in its binding site in the protein. A possible explanation for the spectrum of the monoclinic crystals is that the shift tensor is averaged by a proton exchange process between different ionization states of the PLP associated with the presence of a sulfate ion bound in the vicinity of the PLP. PMID:8457673

Taguchi, Jocelyn E.; Heyes, Stephen J.; Barford, David; Johnson, Louise N.; Dobson, Christopher M.

1993-01-01

319

Density functional theory calculations of the nuclear magnetic resonance spin-Hamiltonian parameters for two polyamines of prostate tissue: spermidine and spermine  

NASA Astrophysics Data System (ADS)

1H nuclear magnetic resonance (NMR) spin-Hamiltonian parameters: chemical shifts ? and spin-spin coupling constants J have been calculated for the two polyamines: spermidine and spermine present in prostate tissue. Molecules in the gas phase as well as in solution in water have been investigated using density functional theory calculations. From calculated ? and J values, NMR spectra have been simulated and compared to the experimental ones we acquired at 400 MHz for each polyamine in solution in D2O. From these comparisons, reliable NMR parameters are proposed for spermidine and spermine, among which the J constants were until now unknown for these two molecules.

Atieh, Z.; Allouche, A. R.; Graveron-Demilly, D.; Fauvelle, F.; Aubert-Frécon, M.

2009-10-01

320

Dynamic carbon 13 breath tests for the study of liver function and gastric emptying.  

PubMed

In gastroenterological practice, breath tests (BTs) are diagnostic tools used for indirect, non-invasive assessment of several pathophysiological metabolic processes, by monitoring the appearance in breath of a metabolite of a specific substrate. Labelled substrates originally employed radioactive carbon 14 ((14)C) and, more recently, the stable carbon 13 isotope ((13)C) has been introduced to label specific substrates. The ingested (13)C-substrate is metabolized, and exhaled (13)CO2 is measured by mass spectrometry or infrared spectroscopy. Some (13)C-BTs evaluate specific (microsomal, cytosolic, and mitochondrial) hepatic metabolic pathways and can be employed in liver diseases (i.e. simple liver steatosis, non-alcoholic steato-hepatitis, liver fibrosis, cirrhosis, hepatocellular carcinoma, drug and alcohol effects). Another field of clinical application for (13)C-BTs is the assessment of gastric emptying kinetics in response to liquids ((13)C-acetate) or solids ((13)C-octanoic acid in egg yolk or in a pre-packed muffin or the (13)C-Spirulina platensis given with a meal or a biscuit). Studies have shown that (13)C-BTs, used for gastric emptying studies, yield results that are comparable to scintigraphy and can be useful in detecting either delayed- (gastroparesis) or accelerated gastric emptying or changes of gastric kinetics due to pharmacological effects. Thus, (13)C-BTs represent an indirect, cost-effective and easy method of evaluating dynamic liver function and gastric kinetics in health and disease, and several other potential applications are being studied. PMID:25339354

Bonfrate, Leonilde; Grattagliano, Ignazio; Palasciano, Giuseppe; Portincasa, Piero

2014-10-21

321

Carbon-13 variations in fluids from the Cerro Prieto geothermal system  

SciTech Connect

The carbon isotope compositions of CO/sub 2/ in steam from Cerro Prieto production well have been measured for 1977, 1979, and 1982. Variations in the delta/sup 13/C values are caused by production-related changes in the chemical and physical parameters of the geothermal system. In 1977, most CO/sub 2/ in the reservoir was isotopically light (delta/sup 13/C = -6.4 +/- 0.4). Heavier CO/sub 2/ was produced from wells in the center of the field (M5,M26,M27) due to deposition of isotopically light calcite caused by near-well boiling. In 1979 nearly all well showed relatively heavy CO/sub 2/, probably due to expansion of aquifer boiling and calcite precipitation. In 1982, many wells in the central part of the field were shut in. The amount of drawndown decreased and as temperatures and pressures near the wells increased, the boiling zones collapsed. The CO/sub 2/ in the fluid then exchanged with the precipitated calcite and became isotopically lighter. The sensitivity of carbon isotopes to calcite precipitations caused by aquifer boiling and to reequilibration with this deposited calcite upon decrease of boiling suggests use as an indicator of these aquifer processes. Surficial CO/sub 2/ of thermal origin was collected in 1981. Generally, the carbon-13 contents were close to CO/sub 2/ from production wells except for high-temperature mud pots and fumaroles containing isotopically light CO/sub 2/ derived from near surface alteration of organic matter.

Janik, C.J.; Nehring, N.L.; Huebner, M.A.; Truesdell, A.H.

1982-08-10

322

Temperature-dependent dynamical nuclear polarization bistabilities in double quantum dots in the spin-blockade regime  

E-print Network

The interplay of dynamical nuclear polarization (DNP) and leakage current through a double quantum dot in the spin-blockade regime is analyzed. A finite DNP is built up due to a competition between hyperfine (HF) spin-flip transitions and another inelastic escape mechanism from the triplets, which block transport. We focus on the temperature dependence of the DNP for zero energy-detuning (i.e. equal electrostatic energy of one electron in each dot and a singlet in the right dot). Our main result is the existence of a transition temperature, below which the DNP is bistable, so a hysteretic leakage current versus external magnetic field B appears. This is studied in two cases: (i) Close to the crossing of the three triplet energy levels near B=0, where spin-blockade is lifted due to the inhomogeneity of the effective magnetic field from the nuclei. (ii) At higher B-fields, where the two spin-polarized triplets simultaneously cross two different singlet energy levels. We develop simplified models leading to different transition temperatures T_TT and T_ST for the crossing of the triplet levels and the singlet-triplet level crossings, respectively. We find T_TT analytically to be given solely by the HF couplings, whereas T_ST depends on various parameters and T_ST>T_TT. The key idea behind the existence of the transition temperatures at zero energy-detuning is the suppression of energy absorption compared to emission in the inelastic HF transitions. Finally, by comparing the rate equation results with Monte Carlo simulations, we discuss the importance of having both HF interaction and another escape mechanism from the triplets to induce a finite DNP.

Anders Mathias Lunde; Carlos López-Monís; Ioanna A. Vasiliadou; Luis L. Bonilla; Gloria Platero

2012-11-29

323

Electron spin resonance and electron nuclear double resonance of photogenerated polarons in polyfluorene and its fullerene composite  

NASA Astrophysics Data System (ADS)

Electron spin resonance (ESR) and electron-nuclear double resonance (ENDOR) of photogenerated polarons in poly(9,9-dioctylfluorene) (PFO) and its composite with fullerene (C60) using variable photoexcitation energy up to 4.1 eV are reported. For PFO, a light-induced ESR (LESR) signal (g=2.003) is observed below 60 K, and its transient response and excitation spectrum indicate that the observed spins are photogenerated polarons on PFO. For the PFO-C60 composite, two LESR signals of photogenerated positive polarons on PFO (g1=2.003) and radical anions on C60 (g2=1.999) , respectively, are observed below 120 K, which are caused by photoinduced electron transfer from PFO to C60 . A remarkable enhancement of the LESR signals in the excitation spectrum at ˜2.8eV is observed compared with the case of pure PFO. The bimolecular-recombination kinetics of photogenerated charge carriers in the composite are confirmed by the dependence of the LESR on excitation-light intensity and by the decay dynamics. Light-induced ENDOR (LENDOR) signals are clearly observed for excitation around 2.8 eV owing to the highly efficient photoinduced electron transfer in the composite. Broad LENDOR shifts directly reflect the spin-density distribution of the polarons in PFO. We have determined its maximum shift using LENDOR-induced ESR, and have evaluated the maximum spin density on the carbon site coupled to the proton as 0.032. This value is consistent with the theoretical result obtained by Pariser-Parr-Pople (PPP) model, where the spatial extent of the polarons is calculated as ˜3 monomer units of PFO. The calculated LESR spectra of PFO based on the PPP model are consistent with the experimental spectra, which confirm the above spatial extension of the polaron in PFO.

Marumoto, K.; Kato, M.; Kondo, H.; Kuroda, S.; Greenham, N. C.; Friend, R. H.; Shimoi, Y.; Abe, S.

2009-06-01

324

Applications of carbon-13 and sodium-23 NMR in the study of plants, animal, and human cells  

SciTech Connect

Carbon-13 and sodium-23 NMR have been applied to the study of a variety of plant, animal and human cell types. Sodium NMR, in combination with dysprosium shift reagents, has been used to monitor sodium transport kinetics in salt-adapted, and non-adapted cells of P. milliaceum and whole D. spicata plants. The sodium content of human erythrocytes and leukemic macrophages was measured. Carbon-13 NMR was used to determine the structure and metabolism of rat epididymal fat pad adipocytes in real time. Insulin and isoproterenol-stimulated triacylglycerol turnover could be monitored in fat cell suspensions. (1-/sup 13/C) glucose was used as a substrate to demonstrate futile metabolic cycling from glucose to glycerol during lypolysis. Cell wall polysaccharide synthesis was followed in suspensions of P. milliaceum cells using (1-/sup 13/C) glucose as a precursor. These results illustrate the wide range of living systems which are amenable to study with NMR. 14 refs., 21 figs.

Sillerud, L.O.; Heyser, J.W.; Han, C.H.; Bitensky, M.W.

1984-01-01

325

Rovibronic species, overall allowed species, and nuclear spin statistical weights for symmetric top molecules. II. Point groups Cnv and Cnh (n <= 6)  

NASA Astrophysics Data System (ADS)

The method described in I [A. Weber, J. Chem. Phys. 73, 1952 (1980); 74, 4754 (1981)] has been used to derive the rovibronic species, overall allowed species, and the nuclear spin statistical weights for symmetric top molecules belonging to the point groups Cnv or Cnh with n?6. Rules are presented by means of which the rovibronic species of Cnv and Cnh molecules are obtained from the results given in I. The overall species and the nuclear spin statistical weights are given in a new set of tables.

Weber, Alfons

1982-04-01

326

NUCLEAR AND HEAVY ION PHYSICS: Decomposition of the equation of state of asymmetric nuclear matter into different spin-isospin channels  

NASA Astrophysics Data System (ADS)

We investigate the equation of state of asymmetric nuclear matter and its isospin dependence in various spin-isospin ST channels within the framework of the Brueckner-Hartree-Fock approach extended to include a microscopic three-body force (TBF). It is shown that the potential energy per nucleon in the isospin-singlet T = 0 channel is mainly determined by the contribution from the tensor SD coupled channel. At high densities, the TBF effect on the isospin-triplet T = 1 channel contribution turns out to be much larger than that on the T = 0 channel contribution. At low densities around and below the normal nuclear matter density, the isospin dependence is found to come essentially from the isospin-singlet SD channel and the isospin-triplet T = 1 component is almost independent of isospin asymmetry. As the density increases, the T = 1 channel contribution becomes sensitive to the isospin asymmetry and at high enough densities its isospin dependence may even become more pronounced than that of the T = 0 contribution. The present results may provide some microscopic constraints for improving effective nucleon-nucleon interactions in a nuclear medium and for constructing new functionals of effective nucleon-nucleon interaction based on microscopic many-body theories.

Zuo, Wei; Zhou, Shan-Gui; Li, Jun-Qing; Zhao, En-Guang; Scheid, W.

2009-07-01

327

On the origin of high- spin states in nuclear fission fragments  

E-print Network

In the "nucleon-phase" model of binary fission, the transfer of nucleons between an A =126 {\\guillemotleft} nucleon core {\\guillemotright} and the primordial "cluster" can explain both the formation of high- spin states and the saw-tooth behavior of the variation, as a function of fragment mass, of the average angular momentum.

G. Mouze; C. Ythier; S. Hachem

2011-03-28

328

On the origin of high- spin states in nuclear fission fragments  

E-print Network

In the "nucleon-phase" model of binary fission, the transfer of nucleons between an A =126 {\\guillemotleft} nucleon core {\\guillemotright} and the primordial "cluster" can explain both the formation of high- spin states and the saw-tooth behavior of the variation, as a function of fragment mass, of the average angular momentum.

Mouze, G; Hachem, S

2011-01-01

329

Nuclear spin-orbit interaction and T-odd angular correlations in ternary fission  

E-print Network

T-odd angular correlations in ternary fission of 233-U and 235-U nuclei by slow polarized neutrons are not related to TRI (time reversal invariance) violation, but are caused by an effective spin-orbit interaction in the final state.

A. L. Barabanov

2014-07-08

330

Dipolar nuclear spin relaxation in liquids and plane fluids undergoing chemical reactions  

NASA Astrophysics Data System (ADS)

We describe the correlated translational and rotational relative brownian motions of two reacting groups of atoms, alternatively bound and free, by the normalized solutions of a set of coupled diffusion equations. Under equilibrium conditions we calculate the spectral densities j(?) characteristic of the fluctuations of the intermolecular dipolar coupling between spins of these diffusing groups of atoms. When ?? << 1, where ? is the translational correlation time, the form of the spectral density j2(?) in three-dimensional liquids is j2(0) - ?3?1/2. The coefficient ?3 is independent of the molecular local order, of the diffusional rotation speed of the spin-carrying groups of atoms and of their association and dissociation rates. In plane fluids, when ?? << 1, the spectral density j(0)(?) may be written as -a2 ln (??) where the dependence of a2 on the average relative distribution of the interacting spins varies with the rate of the chemical reactions. In both three- and two-dimensional fluids spectral densities show an ?-3/2 or ?-2 behaviour for ?? >> 1 according to the magnitude of the association rate of the reacting groups of atoms. In liquid glycerol we analyse the low- and high-frequency limits of the experimental proton relaxation rate 1/T1 and 1/T1? measured by Harmon, Harmon and Burnett, and Lenk. We also discuss the proton spin-lattice relaxation times measured by Kleinberg and Silbernagel in layered intercalation compounds TiS2-NH3 and TaS2-NH3.

Fries, P. H.

331

Devices and process for high-pressure magic angle spinning nuclear magnetic resonance  

DOEpatents

A high-pressure magic angle spinning (MAS) rotor is detailed that includes a high-pressure sample cell that maintains high pressures exceeding 150 bar. The sample cell design minimizes pressure losses due to penetration over an extended period of time.

Hoyt, David W; Sears, Jr., Jesse A; Turcu, Romulus V.F.; Rosso, Kevin M; Hu, Jian Zhi

2014-04-08

332

Enhancing the Superconducting Transition Temperature of CeRh1-xIrxIn5 due to the Strong-Coupling Effects of Antiferromagnetic Spin Fluctuations: An In115 Nuclear Quadrupole Resonance Study  

Microsoft Academic Search

We report on systematic evolutions of antiferromagnetic (AFM) spin fluctuations and unconventional superconductivity (SC) in heavy-fermion (HF) compounds CeRh1-xIrxIn5 via an In115 nuclear-quadrupole-resonance experiment. The nuclear spin-lattice relaxation rate 1\\/T1 has revealed the marked development of AFM spin fluctuations as approaching an AFM ordered state. Concomitantly, the superconducting transition temperature Tc and the energy gap Delta0 increase drastically from Tc=0.4K

Shinji Kawasaki; Mitsuharu Yashima; Yoichi Mugino; Hidekazu Mukuda; Yoshio Kitaoka; Hiroaki Shishido; Yoshichika Onuki

2006-01-01

333

Cost-effectiveness of the Carbon-13 Urea Breath Test for the Detection of Helicobacter Pylori  

PubMed Central

Objectives This analysis aimed to evaluate the cost-effectiveness of various testing strategies for Helicobacter pylori in patients with uninvestigated dyspepsia and to calculate the budgetary impact of these tests for the province of Ontario. Data Sources Data on the sensitivity and specificity were obtained from the clinical evidence-based analysis. Resource items were obtained from expert opinion, and costs were applied on the basis of published sources as well as expert opinion. Review Methods A decision analytic model was constructed to compare the costs and outcomes (false-positive results, false-negative results, and misdiagnoses avoided) of the carbon-13 (13C) urea breath test (UBT), enzyme-linked immunosorbent assay (ELISA) serology test, and a 2-step strategy of an ELISA serology test and a confirmatory 13C UBT based on the sensitivity and specificity of the tests and prevalence estimates. Results The 2-step strategy is more costly and more effective than the ELISA serology test and results in $210 per misdiagnosis case avoided. The 13C UBT is dominated by the 2-step strategy, i.e., it is more costly and less effective. The budget impact analysis indicates that it will cost $7.9 million more to test a volume of 129,307 patients with the 13C UBT than with ELISA serology, and $4.7 million more to test these patients with the 2-step strategy. Limitations The clinical studies that were pooled varied in the technique used to perform the breath test and in reference standards used to make comparisons with the breath test. However, these parameters were varied in a sensitivity analysis. The economic model was designed to consider intermediate outcomes only (i.e., misdiagnosed cases) and was not a complete model with final patient outcomes (e.g., quality-adjusted life years). Conclusions Results indicate that the 2-step strategy could be economically attractive for the testing of H. pylori. However, testing with the 2-step strategy will cost the Ministry of Health and Long-Term Care $4.7 million more than with the ELISA serology test. PMID:24228083

Masucci, L; Blackhouse, G; Goeree, R

2013-01-01

334

Quantitation of a spin polarization-induced nuclear Overhauser effect (SPINOE) between a hyperpolarized 13C-labeled cell metabolite and water protons  

PubMed Central

The spin polarization-induced nuclear Overhauser effect (SPINOE) describes the enhancement of spin polarization of solvent nuclei by the hyperpolarized spins of a solute. In this communication we demonstrate that SPINOEs can be observed between [1,4-13C2]fumarate, hyperpolarized using the dissolution dynamic nuclear polarization technique, and solvent water protons. We derive a theoretical expression for the expected enhancement and demonstrate that this fits well with experimental measurements. Although the magnitude of the effect is relatively small (around 2% measured here), the SPINOE increases at lower field strengths, so that at clinically relevant magnetic fields (1.5–3?T) it may be possible to track the passage through the circulation of a bolus containing a hyperpolarized 13C-labeled substrate through the increase in solvent water 1H signal. © 2014 The Authors. Contrast Media & Molecular Imaging published by John Wiley and Sons, Ltd. PMID:24523064

Marco-Rius, Irene; Bohndiek, Sarah E; Kettunen, Mikko I; Larkin, Timothy J; Basharat, Meer; Seeley, Colm; Brindle, Kevin M

2014-01-01

335

Anti-symmetric spin-orbit force in the effective interaction for the shell model and its effect on nuclear structure  

SciTech Connect

Anti-symmetric spin-orbit force (ALS) in the effective interaction for the shell model and its effect on nuclear structure is discussed. We investigate possible origins of the ALS and the effects on the level schemes of several nuclei.

Tsunoda, N.; Shimizu, N. [Department of Science, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, I-80126 (Japan); Otsuka, T. [Department of Science, University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, I-80126 (Japan); Center for Nuclear Study, University of Tokyo, Hongo, Bunkyo-ku Tokyo, 113-0033 (Japan) and National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI (United States); Suzuki, T. [Department of Physics, College of Humanities and Sciences, Nihon University, Sakurajosui 3, Tokyo 156-8550 (Japan)

2011-05-06

336

Group theory, nuclear spin statistics and tunneling splittings of 1,3,5-triamino-2,4,6-trinitrobenzene  

NASA Astrophysics Data System (ADS)

The symmetry group of the non-rigid 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is constructed for the internal rotations of the nitro groups that exhibit low rotation barriers of 5 kcal/mole. The permutation group has 48 operations characterized by the wreath product S 3[S 2]. The nuclear spin statistical weights for TATB with 17O, 14N and 1H species are computed and the tunneling splitting patterns of the rotational and rovibronic levels of TATB are constructed for the first time. It is shown that the ground rovibronic state of TATB is split into A 1, A 3, T 1 and T 3 levels.

Balasubramanian, Krishnan

2004-11-01

337

Study of Nuclear Bound States Using Mean-Field Woods-Saxon and Spin-Orbit Potentials  

NASA Astrophysics Data System (ADS)

The neutron single-particle bound states as solutions of radial Schrödinger equation for the central Woods-Saxon potential together with spin-orbit interaction and centrifugal terms have been obtained analytically. By introducing new variable and using Taylor expansion, the differential equation has been transformed to solvable hypergeometric type. This differential equation has also been solved using Nikiforov-Uvarov (NU) method. Neutron single-particle states have been derived as self-adjoint form of hypergeometric series. By means of boundary conditions, which implies eigenvalue condition as complicated relation between energy eigenvalues and parameters of nuclear potential, the neutron single-particle energy eigenvalues have been derived using graphical method. To examine method, numerical results in special cases of S states are evaluated. Results obtained using this method are in satisfactory agreements with available numerical solutions.

Pahlavani, M. R.; Alavi, S. A.

2012-09-01

338

Laser cooling and real-time measurement of the nuclear spin environment of a solid-state qubit.  

PubMed

Control over quantum dynamics of open systems is one of the central challenges in quantum science and engineering. Coherent optical techniques, such as coherent population trapping involving dark resonances, are widely used to control quantum states of isolated atoms and ions. In conjunction with spontaneous emission, they allow for laser cooling of atomic motion, preparation and manipulation of atomic states, and rapid quantum optical measurements that are essential for applications in metrology. Here we show that these techniques can be applied to monitor and control individual atom-like impurities, and their local environment, in the solid state. Using all-optical manipulation of the electronic spin of an individual nitrogen-vacancy colour centre in diamond, we demonstrate optical cooling, real-time measurement and conditional preparation of its nuclear spin environment by post-selection. These methods offer potential applications ranging from all-optical nanomagnetometry to quantum feedback control of solid-state qubits, and may lead to new approaches for quantum information storage and processing. PMID:22031442

Togan, E; Chu, Y; Imamoglu, A; Lukin, M D

2011-10-27

339

Nuclear magnetic relaxation induced by exchange-mediated orientational randomization: Longitudinal relaxation dispersion for a dipole-coupled spin-1/2 pair  

NASA Astrophysics Data System (ADS)

In complex biological or colloidal samples, magnetic relaxation dispersion (MRD) experiments using the field-cycling technique can characterize molecular motions on time scales ranging from nanoseconds to microseconds, provided that a rigorous theory of nuclear spin relaxation is available. In gels, cross-linked proteins, and biological tissues, where an immobilized macromolecular component coexists with a mobile solvent phase, nuclear spins residing in solvent (or cosolvent) species relax predominantly via exchange-mediated orientational randomization (EMOR) of anisotropic nuclear (electric quadrupole or magnetic dipole) couplings. The physical or chemical exchange processes that dominate the MRD typically occur on a time scale of microseconds or longer, where the conventional perturbation theory of spin relaxation breaks down. There is thus a need for a more general relaxation theory. Such a theory, based on the stochastic Liouville equation (SLE) for the EMOR mechanism, is available for a single quadrupolar spin I = 1. Here, we present the corresponding theory for a dipole-coupled spin-1/2 pair. To our knowledge, this is the first treatment of dipolar MRD outside the motional-narrowing regime. Based on an analytical solution of the spatial part of the SLE, we show how the integral longitudinal relaxation rate can be computed efficiently. Both like and unlike spins, with selective or non-selective excitation, are treated. For the experimentally important dilute regime, where only a small fraction of the spin pairs are immobilized, we obtain simple analytical expressions for the auto-relaxation and cross-relaxation rates which generalize the well-known Solomon equations. These generalized results will be useful in biophysical studies, e.g., of intermittent protein dynamics. In addition, they represent a first step towards a rigorous theory of water 1H relaxation in biological tissues, which is a prerequisite for unravelling the molecular basis of soft-tissue contrast in clinical magnetic resonance imaging.

Chang, Zhiwei; Halle, Bertil

2013-10-01

340

Solid-State Dynamic Nuclear Polarization at 263 GHz: Spectrometer Design and Experimental Results  

E-print Network

Dynamic Nuclear Polarization (DNP) experiments transfer polarization from electron spins to nuclear spins with microwave irradiation of the electron spins for enhanced sensitivity in nuclear magnetic resonance (NMR) ...

Rosay, Melanie

341

Normal state spin susceptibility in YBa 2Cu 3O 6.92 single crystal from 63Cu and 89Y nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

We present an extensive nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) study of the normal state ( T> Tc) of an YBa 1.93Sr 0.07Cu 3O 6.92 single crystal ( Tc=90 K). The NMR data is interpreted using a model for the imaginary part of the dynamical electron spin susceptibility ??( q, ?) that is consistent with the inelastic neutron scattering (INS) experiments (carried out on the same sample investigated here): the q-dependence is assumed to be Gaussian (commensurate), with short and T independent coherence length ?. This model enabled us to perform a quantitative analysis of the planar copper spin-lattice and spin-spin relaxation rates which evidenced that a spin pseudogap starts to open at T*?130 K, confirming the INS results. Moreover, we show that the AF fluctuations contribution to yttrium relaxation is not negligible due to the dipolar coupling of the yttrium with the neighboring copper spins. The main signature of this feature is that a relation K??T1T=const does not hold for the yttrium site at higher temperatures. Our main conclusion is that, in order to explain the yttrium (and the planar oxygen) relaxation coherently with the INS results and the widely accepted one-band picture, the characteristic energy ?0 of the spin dynamics near q=0 must be strongly T dependent, otherwise the one-band description is not feasible. All the NMR results are interpreted within the ionic model of the hyperfine Hamiltonian taking into account the anisotropy of the g-factor and the static spin susceptibility ?s.

Auler, T.; Horvatic, M.; Gillet, J. A.; Berthier, C.; Berthier, Y.; Carretta, P.; Kitaoka, Y.; Ségransan, P.; Henry, J. Y.

1999-02-01

342

Search of non-standard strong gravity at nuclear scale using electron spin geodetic precession  

NASA Astrophysics Data System (ADS)

The MTV-G project was started in 2011 to explore a strong gravitational field at a nuclear scale in an electron double scattering experiment, utilizing an experimental technique of the MTV experiment, which searches a electron's T-Violating transverse polarization in nuclear beta decay at TRIUMF-ISAC. In addition to this new experiment, we have also performed a re-analysis of spectroscopic data of exotic atoms, in a gravitational point of view. From these two studies, we set new constraints on possible new Yukawa interaction at sub-mm scale, as a test of gravitational inverse square law.

Tanaka, Saki; Nakaya, Yusuke; Narikawa, Reiya; Ninomiya, Kazufumi; Onishi, Junichi; Pearson, Matthew; Openshaw, Robert; Saiba, Shuntaro; Tanuma, Ryosuke; Totsuka, Yumi; Murata, Jiro

2014-03-01

343

Nuclear magnetic resonance data of C3H9ClSi  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

344

Nuclear magnetic resonance data of C18H15ClSi  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

345

Nuclear magnetic resonance data of C13H13ClSi  

NASA Astrophysics Data System (ADS)

This document is part of Part 6 `Organic Metalloid Compounds' of Subvolume D 'Chemical Shifts and Coupling Constants for Carbon-13' of Landolt-Börnstein III/35 'Nuclear Magnetic Resonance Data', Group III 'Condensed Matter'.

Mikhova, B. M.

346

Intermolecular potentials from nuclear spin lattice relaxation in pure gases with octahedral symmetry  

NASA Astrophysics Data System (ADS)

Fluorine spin lattice relaxation times per unit density T1/? in pure SF6, MoF6, WF6 and UF6 gases are experimentally found to be proportional to T-1·5 where T is the temperature. These data can be analysed to obtain information on the anisotropic part of the intermolecular potential in these systems. Hard sphere, Lennard-Jones (6-12) and modified Buckingham (exp-6) potentials were used for the isotropic part of the intermolecular interaction. The analysis is made using the Bloom-Oppenheim theory, assuming that the correlation time of the spin rotation interaction can be approximated by the average lifetime of a molecule in the given J state. We have obtained the strengths of the repulsive and attractive terms in the anisotropic potential. From the strength of the attractive term in the anisotropic potential, the hexadecapole moments of all the four molecules are obtained. The hexadecapole moment of SF6 obtained by us using the Lennard-Jones model is in good agreement with the values reported earlier, based on other techniques, while the values for MoF6, WF6 and UF6 are reported for the first time.

Ursu, I.; Bogdan, M.; Balibanu, F.; Fitori, P.; Mihailescu, G.; Demco, D. E.

347

Nuclear spin relaxation by translational diffusion of hydrogen in BCC metals: the effect of hopping to second-nearest neighbors  

Microsoft Academic Search

Quantities relevant to the theoretical determination of D\\/T1 are calculated, where D is the tracer diffusion coefficient and T1 is the spin-lattice relaxation time for relaxation due to magnetic dipolar coupling between diffusing hydrogen spins. Calculations are performed for hydrogen spins diffusing on the tetrahedral interstitial sites of a BCC host metal and both the like-spin (hydrogen-hydrogen) and unlike-spin (metal-hydrogen)

D. A. Faux

1991-01-01

348

Observation of Optical Chemical Shift by Precision Nuclear Spin Optical Rotation Measurements and Calculations  

E-print Network

and Calculations Junhui Shi, Suvi Ikalainen, Juha Vaara,¶ and Michael V. Romalis*,§ Department of Chemistry The rotation of light polarization is similar to the Faraday effect caused by a nuclear magnetic field to Faraday rotation changes by more than a factor of 2 for the simple chemicals studied. We apply the recent

Romalis, Mike

349

Effect of nuclear spin on chemical reactions and internal molecular rotation  

SciTech Connect

Part I of this dissertation is a study of the magnetic isotope effect, and results are presented for the separation of /sup 13/C and /sup 12/C isotopes. Two models are included in the theoretical treatment of the effect. In the first model the spin states evolve quantum mechanically, and geminate recombination is calculated by numerically integrating the collision probability times the probability the radical pair is in a singlet state. In the second model the intersystem crossing is treated via first-order rate constants which are average values of the hyperfine couplings. Using these rate constants and hydrodynamic diffusion equations, an analytical solution, which accounts for all collisions, is obtained for the geminate recombination. The two reactions studied are photolysis of benzophenone and toluene and the photolytic decomposition of dibenzylketone (1,3-diphenyl-2-propanone). No magnetic isotope effect was observed in the benzophenone reaction. /sup 13/C enrichment was observed for the dibenzylketone reaction, and this enrichment was substantially enhanced at intermediate viscosities and low temperatures. Part II of this dissertation is a presentation of theory and results for the use of Zeeman spin-lattice relaxation as a probe of methyl group rotation in the solid state. Experimental results are presented for the time and angular dependences of rotational polarization, the methyl group magnetic moment, and methyl-methyl steric interactions. The compounds studied are 2,6-dimethylphenol, methyl iodide, 1,4,5,8-tetramethylanthracene, 1,4,5,8-tetramethylnaphthalene, 1,2,4,5-tetramethylbenzene, and 2,3-dimethylmaleicanhydride.

Sterna, L.L.

1980-12-01

350

Nuclear shadowing in polarized deep inelastic scattering on 6Li D at small x and its effect on the extraction of the deuteron spin structure function gd1(x,Q2)  

NASA Astrophysics Data System (ADS)

We consider the effect of nuclear shadowing in polarized deep inelastic scattering (DIS) on 6Li D at small Bjorken x and its relevance for the extraction of the deuteron spin structure function gd1(x,Q2). Using models, which describe nuclear shadowing in unpolarized DIS, we demonstrate that the nuclear shadowing correction to gd1(x,Q2) is significant.

Guzey, V.

2001-10-01

351

Influence of intramolecular f-f interactions on nuclear spin driven quantum tunneling of magnetizations in quadruple-decker phthalocyanine complexes containing two terbium or dysprosium magnetic centers.  

PubMed

Nuclear spin driven quantum tunneling of magnetization (QTM) phenomena, which arise from admixture of more than two orthogonal electronic spin wave functions through the couplings with those of the nuclear spins, are one of the important magnetic relaxation processes in lanthanide single molecule magnets (SMMs) in the low temperature range. Although recent experimental studies have indicated that the presence of the intramolecular f-f interactions affects their magnetic relaxation processes, little attention has been given to their mechanisms and, to the best of our knowledge, no rational theoretical models have been proposed for the interpretations of how the nuclear spin driven QTMs are influenced by the f-f interactions. Since quadruple-decker phthalocyanine complexes with two terbium or dysprosium ions as the magnetic centers show moderate f-f interactions, these are appropriate to investigate the influence of the f-f interactions on the dynamic magnetic relaxation processes. In the present paper, a theoretical model including ligand field (LF) potentials, hyperfine, nuclear quadrupole, magnetic dipolar, and the Zeeman interactions has been constructed to understand the roles of the nuclear spins for the QTM processes, and the resultant Zeeman plots are obtained. The ac susceptibility measurements of the magnetically diluted quadruple-decker monoterbium and diterbium phthalocyanine complexes, [Tb-Y] and [Tb-Tb], have indicated that the presence of the f-f interactions suppresses the QTMs in the absence of the external magnetic field (H(dc)) being consistent with previous reports. On the contrary, the faster magnetic relaxation processes are observed for [Tb-Tb] than [Tb-Y] at H(dc) = 1000 Oe, clearly demonstrating that the QTMs are rather enhanced in the presence of the external magnetic field. Based on the calculated Zeeman diagrams, these observations can be attributed to the enhanced nuclear spin driven QTMs for [Tb-Tb]. At the H(dc) higher than 2000 Oe, the magnetic relaxations become faster with increasing Hdc for both complexes, which are possibly ascribed to the enhanced direct processes. The results on the dysprosium complexes are also discussed as the example of a Kramers system. PMID:24003906

Fukuda, Takamitsu; Matsumura, Kazuya; Ishikawa, Naoto

2013-10-10

352

Mesoporous Silica Nanoparticles Loaded with Surfactant: Low Temperature Magic Angle Spinning 13C and 29Si NMR Enhanced by Dynamic Nuclear Polarization  

SciTech Connect

We show that dynamic nuclear polarization (DNP) can be used to enhance NMR signals of 13C and 29Si nuclei located in mesoporous organic/inorganic hybrid materials, at several hundreds of nanometers from stable radicals (TOTAPOL) trapped in the surrounding frozen disordered water. The approach is demonstrated using mesoporous silica nanoparticles (MSN), functionalized with 3-(N-phenylureido)propyl (PUP) groups, filled with the surfactant cetyltrimethylammonium bromide (CTAB). The DNP-enhanced proton magnetization is transported into the mesopores via 1H–1H spin diffusion and transferred to rare spins by cross-polarization, yielding signal enhancements ?on/off of around 8. When the CTAB molecules are extracted, so that the radicals can enter the mesopores, the enhancements increase to ?on/off ? 30 for both nuclei. A quantitative analysis of the signal enhancements in MSN with and without surfactant is based on a one-dimensional proton spin diffusion model. The effect of solvent deuteration is also investigated.

Lafon, Olivier [Universite de Lille Nord de France; Thankamony, Aany S. Lilly [Universite de Lille Nord de France; Kokayashi, Takeshi [Ames Laboratory; Carnevale, Diego [Ecole Polytechnique Federale de Lausanne; Vitzthum, Veronika [Ecole Polytechnique Federale de Lausanne; Slowing, Igor I. [Ames Laboratory; Kandel, Kapil [Ames Laboratory; Vezin, Herve [Universite de Lille Nord de France; Amoureux, Jean-Paul [Universite de Lille Nord de France; Bodenhausen, Geoffrey [Ecole Polytechnique Federale de Lausanne; Pruski, Marek [Ames Laboratory

2012-12-21

353

Indole alkaloids of Rauwolfia reflexa. Carbon-13 nuclear magnetic resonance structural analysis of the bis(indole) alkaloid flexicorine  

SciTech Connect

The /sup 13/C NMR spectra analysis of the new bis(indole) alkaloid flexicorine and of its chemically modified derivatives were used to determine the structure of the natural base. Flexicorine is, apparently, the first 10'-hydroxy N'-unsubstituted indoline which preferentially exists in the original iminoquinone form. 2 tables.

Chatterjee, A. (Univ. College of Science, Calcutta, India); Ghosh, A.K.; Hagaman, E.W.

1982-01-01

354

CARBON-13 NUCLEAR MAGNETIC RESONANCE. 13C CHEMICAL SHIFTS AND 13C-199HG COUPLING CONSTANTS FOR SOME ORGANOMERCURY COMPOUNDS  

EPA Science Inventory

The (13)C shieldings and (13)C-(199)Hg coupling constants of fourteen phenyl- and seven alkyl- and alkenyl-mercury compounds have been obtained. Substituent effects on the (13)C shieldings are similar to those in nonmercurated phenyl compounds, with a similar relationship between...

355

STRUCTURES OF SOME KEPONE PHOTOPRODUCTS AND RELATED CHLORINATED PENTACYCLODECANES BY CARBON-13 AND PROTON NUCLEAR MAGNETIC RESONANCE  

EPA Science Inventory

The pesticide Kepone, 1,1a,3,3a,4,5,5a,5b,6-decachlorooctahydro-1,3,4-metheno-2H-cyclobuta(cd)pentalen-2-one, the related compounds mirex, kelevan, a monohydro photoproduct of kelevan, kepone alcohol, kepone hydrate, and the mono- and dihydro photoproducts of Kepone hydrate and t...

356

Enhancement of nuclear-spin cross-relaxation in metal-hydrogen systems  

SciTech Connect

A cross-relaxation model has previously been proposed to explain the anomalous frequency dependence of proton relaxation rates {ital R}{sub 1} in several metal-hydrogen systems at low temperatures. We report two experiments that test and unambiguously confirm the cross-relaxation model. The first experiment uses large-amplitude field modulation to sweep the proton resonance through the inhomogeneously broadened spectrum of metal resonances. The second involves rotation of the sample to sweep the metal resonances through the proton line. In both experiments, the protons are brought into spin thermal contact with an increased number of metal nuclei. Sample rotation rates of only 10 Hz increase the proton {ital R}{sub 1} by a factor of 50 for the TaH{sub {ital x}} system. A simple model explains the variation of {ital R}{sub 1} with rotation speed. Both techniques reveal increased proton relaxation rates {ital R}{sub 1}, unique signatures of the cross-relaxation model. A model is presented that explains the weaker than linear temperature dependence of {ital R}{sub 1}. The role of disorder on a length scale of 500 A or less is emphasized.

Baker, D.B.; Conradi, M.S.; Fedders, P.A.; Norberg, R.E. (Department of Physics, Washington University, St. Louis, Missouri 63130 (United States)); Torgeson, D.R.; Barnes, R.G. (Ames Laboratory and Department of Physics, Iowa State University, Ames, Iowa 50011 (United States)); Bowman, R.C. Jr. (Aerojet Electronic Systems Division, P.O. Box 296, Azusa, California 91702 (United States))

1991-12-01

357

Parallel implementation of the MAGPACK package for the analysis of high-nuclearity spin clusters  

NASA Astrophysics Data System (ADS)

Molecular clusters are formed by a finite number of exchange-coupled paramagnetic centers and they are model systems between molecules and extended solids. In order to simulate their properties and extrapolate to solids, the size of the systems to be treated should be as large as possible. In this context, the use of efficient parallel codes is essential. We present the parallel programs PARANI and PARISO, for anisotropic and isotropic models, that enable the calculation of large energy matrices in parallel and the subsequent computation of the relevant spectral information. The evaluation of the matrix elements is based on the serial package MAGPACK that uses the irreducible tensor operators technique and takes into account all kinds of anisotropic and isotropic magnetic interactions. To obtain the eigenvalues, the energy matrix is partially diagonalized by means of the SLEPc library. The calculation of eigenvalues and eigenvectors of these spin clusters enables us to evaluate the bulk magnetic properties (magnetic susceptibility and magnetization) as well as the spectroscopic properties (inelastic neutron scattering spectra). The results are encouraging in terms of parallel efficiency and open the way to address very challenging problems.

Ramos, E.; Roman, J. E.; Cardona-Serra, S.; Clemente-Juan, J. M.

2010-12-01

358

Long-time behavior of nuclear spin decays in various lattices  

SciTech Connect

The transverse NMR decays of {sup 129}Xe in polycrystalline xenon were recently shown to have a universal property: in the long-time regime these decays all converge to the same sinusoidally modulated exponential function irrespective of the initial transverse spin configuration prepared by a sequence of one or more radio frequency pulses. The present work constitutes a more comprehensive survey of this phenomenon. It examines transverse decays for several different isotopic concentrations of {sup 129}Xe, employs additional pulse sequences, and performs similar measurements in a different material: {sup 19}F in single-crystal and polycrystalline CaF{sub 2}. With the possible exception of polycrystalline CaF{sub 2} where the observation of the long-time behavior is limited by the experimental resolution, all these systems display the long-time universal behavior characterized by particular values of the exponential decay coefficient and beat frequency that were unique for each lattice. This behavior has been theoretically predicted based on the notion of microscopic chaos.

Sorte, E. G.; Saam, B. [Department of Physics, University of Utah, 115 South 1400 East, Salt Lake City, UT 84112-0830 (United States); Fine, B. V. [Institute of Theoretical Physics, University of Heidelberg, Philosophenweg 19, 69120 Heidelberg (Germany)

2011-02-01

359

Bulk Sound Velocity Measurements At High P,T Using Nuclear Inelastic Scattering: Influence Of Spin Transitions On Mantle Velocity Profiles  

NASA Astrophysics Data System (ADS)

Comparison of laboratory measurements of sound and shear wave velocities of mantle minerals with seismic data constitutes one of the foundations upon which knowledge of the Earth’s interior is based. In situ measurements are important, because some transitions (for example, spin transitions) are not quenchable, and may influence the elastic properties of iron-containing minerals. Nuclear inelastic scattering (NIS) offers the possibility to determine bulk sound velocities of iron-containing minerals in the diamond anvil cell through direct measurement of the partial density of states. Both dominant lower mantle phases, silicate perovskite and ferropericlase, have been reported to undergo spin transitions at pressure and temperature conditions of the Earth’s lower mantle, although their nature remains controversial. The resulting uncertainty regarding their influence on mantle properties is bypassed, however, by making direct bulk sound velocity measurements at high pressure and temperature that can be compared with seismic data. Using a newly developed approach, we performed NIS measurements in laser-heated diamond anvil cells, coupled with nuclear forward scattering to determine spin populations and X-ray diffraction to observe crystal structures. All nuclear resonance synchrotron experiments were performed on beamline ID18 at the European Synchrotron Radiation Facility. To investigate the effect of spin transitions on bulk sound velocities of lower mantle minerals, we carried out high pressure and temperature NIS measurements on both silicate perovskite and ferropericlase. The phonon density of states extracted from the NIS data of both phases show that the main peak is shifted to higher energies with increasing temperature, contrary to the general expectation that higher temperatures cause softening of the lattice. Such behaviour might result from changing spin populations due to temperature, and would influence the interpretation of seismic data. We will present the implications of our data for modelling of lower mantle compositions and temperatures, and discuss the consequences for dynamic mantle processes.

McCammon, C. A.; Dubrovinsky, L. S.; Narygina, O.; Glazyrin, K.; Wu, X.; Kantor, I.; Sergueev, I.; Chumakov, A.

2009-12-01

360

Evaluation of nitrogen nuclear hyperfine and quadrupole coupling parameters for the proximal imidazole in myoglobin-azide, -cyanide, and -mercaptoethanol complexes by electron spin echo envelope modulation spectroscopy.  

PubMed

Electron spin echo envelope modulation (ESEEM) spectroscopy and computer simulation of spectra has been used to evaluate the nitrogen nuclear hyperfine and quadrupole coupling parameters for the proximal imidazole nitrogen directly coordinated to iron in three low-spin heme complexes, myoglobin-azide, -cyanide, and -mercaptoethanol (MbN3, MbCN, and MbRS). The variability in the weak electron-nuclear coupling parameters reveals the electronic flexibility within the heme group that depends on properties of the exogenous ligands. For example, the isotropic component of the nitrogen nuclear hyperfine coupling ranges from 4.4 MHz for MbN3 to 2.2 MHz for both MbCN and MbRS. The weaker coupling in MbCN and MbRS is taken as evidence for delocalization of unpaired electron spin from iron into the exogenous anionic ligands. The value of e2Qq, the nuclear quadrupole coupling constant for the axial imidazole nitrogen in MbCN and MbRS, was 2.5 MHz but was significantly larger, 3.2 MHz, in MbN3. This large value is considered evidence for a weakened sigma bond between the proximal imidazole and ferric iron in this form, and for a feature contributing to the origin of the high spin-low spin equilibrium exhibited by MbN3 [Beetlestone, J., & George, P. (1964) Biochemistry 5, 707-714]. The ESEEM results have allowed a correlation to be made between the orientation of the g tensor axes, the orientation of the p-pi orbital of the proximal imidazole nitrogen, and sigma- and pi-bonding features of the axial ligands. Furthermore, the proximal imidazole is suggested to act as a pi-acceptor in low-spin heme complexes in order to support strong sigma electron donation from the lone pair orbital to iron. An evaluation of the nitrogen nuclear hyperfine coupling parameters for the porphyrin pyrrole sites in MbRS reveals a large inequivalence in isotropic components consistent with an orientation of rhombic axes (and g tensor axes) that eclipses the Fe-Npyrrole vector directions. PMID:8395204

Magliozzo, R S; Peisach, J

1993-08-24

361

Radiation-induced oxidation and reduction of guanine: Electron spin resonance--electron nuclear double resonance studies of irradiated guanosine cyclic monophosphate  

SciTech Connect

Two free radicals are identified by electron spin resonance--electron nuclear double resonance (ESR-ENDOR) spectroscopy in single crystals of guanosine 3',5'-cyclic monophosphate x irradiated at 4.2 K. The two absorptions are attributed to the anion and cation formed on the guanine moiety. The characteristics of the cation absorption are consistent with those postulated previously for guanine cation presumed to form in irradiated DNA.

Kim, H.; Budzinski, E.E.; Box, H.C.

1989-02-01

362

Cross-polarization/magic-angle spinning 13C nuclear magnetic resonance study of cellulose I-ethylenediamine complex.  

PubMed

Complete assignments of the cross-polarization/magic-angle spinning (CP/MAS) 13C nuclear magnetic resonance (NMR) spectrum of the cellulose I-ethylenediamine (EDA) complex, which is the intermediate of the reaction from cellulose I to cellulose III(I), were performed. In this paper, we used the 13C-enriched cellulose that was biosynthesized by Acetobacter xylinum ATCC10245 strain from culture medium containing D-(2-13C), D-(3-13C), or D-(5-13C)glucose as a carbon source. After conversion into cellulose I-EDA complex by sufficient EDA treatment, the CP/MAS 13C NMR spectra of the 13C-enriched cellulose I-EDA complexes were measured. As a result, 13C resonance lines of each carbon of the cellulose moiety in the complex appeared as a singlet, suggesting that all glucose residues of the complex are magnetically equivalent. The difference in chemical shifts for each carbon between cellulose I-EDA and cellulose I(alpha), I(beta), and III(I), respectively, suggests that the conformation of the cellulose chains for cellulose I-EDA differs from that for cellulose I(alpha), I(beta), and III(I). In addition, fitting analysis of the 13C spectrum of Valonia cellulose I-EDA complex revealed that the complex contains one EDA molecule per two glucose residues in the cellulose chain. PMID:16233556

Numata, Yukari; Kono, Hiroyuki; Kawano, Shin; Erata, Tomoki; Takai, Mitsuo

2003-01-01

363

Nuclear spin dependence of the reaction of H{sub 3}{sup +} with H{sub 2}. II. Experimental measurements  

SciTech Connect

The nuclear spin dependence of the chemical reaction H{sub 3}{sup +}+ H{sub 2}{yields} H{sub 2} +H{sub 3}{sup +} has been studied in a hollow cathode plasma cell. Multipass infrared direct absorption spectroscopy has been employed to monitor the populations of several low-energy rotational levels of ortho- and para-H{sub 3}{sup +} (o-H{sub 3}{sup +} and p-H{sub 3}{sup +}) in hydrogenic plasmas of varying para-H{sub 2} (p-H{sub 2}) enrichment. The ratio of the rates of the proton hop (k{sup H}) and hydrogen exchange (k{sup E}) reactions {alpha}{identical_to}k{sup H}/k{sup E} is inferred from the observed p-H{sub 3}{sup +} fraction as a function of p-H{sub 2} fraction using steady-state chemical models. Measurements have been performed both in uncooled (T{sub kin}{approx} 350 K) and in liquid-nitrogen-cooled (T{sub kin}{approx} 135 K) plasmas, marking the first time this reaction has been studied at low temperature. The value of {alpha} has been found to decrease from 1.6 {+-} 0.1 at 350 K to 0.5 {+-} 0.1 at 135 K.

Crabtree, Kyle N.; Kauffman, Carrie A.; Tom, Brian A.; Becka, Eftalda; McGuire, Brett A. [Department of Chemistry, University of Illinois, Urbana, Illinois 61801 (United States); McCall, Benjamin J. [Departments of Chemistry, Astronomy, and Physics, University of Illinois, Urbana, Illinois 61801 (United States)

2011-05-21

364

Method for accurate measurements of nuclear-spin optical rotation for applications in correlated optical-NMR spectroscopy  

NASA Astrophysics Data System (ADS)

The nuclear-spin optical rotation (NSOR) effect recently attracted much attention due to potential applications in combined optical-NMR spectroscopy and imaging. Currently, the main problem with applications of NSOR is low SNR and accuracy of measurements. In this work we demonstrate a new method for data acquisition and analysis based on a low-power laser and an emphasis on software based processing. This method significantly reduces cost and is suitable for application in most NMR spectroscopy laboratories for exploration of the NSOR effect. Despite the use of low laser power, SNR can be substantially improved with fairly simple strategies including the use of short wavelength and a multi-pass optical cell with in-flow pre-polarization in a 7 T magnet. Under these conditions, we observed that NSOR signal can be detected in less than 1 min and discuss strategies for further improvement of signal. With higher SNR than previously reported, NSOR constants can be extracted with improved accuracy. On the example of water, we obtained measurements at a level of accuracy of 5%. We include a detailed theoretical analysis of the geometrical factors of the experiment, which is required for accurate quantification of NSOR. This discussion is particularly important for relatively short detection cells, which will be necessary to use in spectroscopy or imaging applications that impose geometrical constraints.

Savukov, I. M.; Chen, H.-Y.; Karaulanov, T.; Hilty, C.

2013-07-01

365

Electron spin relaxation by nuclei in semiconductor quantum dots  

Microsoft Academic Search

We have studied theoretically electron spin relaxation in semiconductor quantum dots via interaction with nuclear spins. The relaxation is shown to be determined by three processes: (i) the precession of the electron spin in the hyperfine field of the frozen fluctuation of the nuclear spins; (ii) the precession of the nuclear spins in the hyperfine field of the electron; and

I. A. Merkulov; Al. L. Efros; M. Rosen

2002-01-01

366

Homogeneous linewidth narrowing of the charged exciton via nuclear spin screening in an InAs/GaAs quantum dot ensemble  

NASA Astrophysics Data System (ADS)

In semiconductor quantum dots, the electron hyperfine interaction with the nuclear spin bath is the leading source of spin decoherence at cryogenic temperature. Using high-resolution two-color differential transmission spectroscopy, we demonstrate that such electron-nuclear coupling also imposes a lower limit for the positively charged exciton dephasing rate, ? , in an ensemble of InAs/GaAs quantum dots. We find that ? is sensitive to the energetic overlap of the charged exciton spin states, which can be controlled through the application of an external magnetic field in the Faraday configuration. At zero applied field, electron-nuclear coupling induces additional dephasing beyond the radiative limit and ? =230 MHz (0.95 ? eV ). Screening of the hyperfine interaction is achieved for an external field of ?1 T, resulting in ? =172 MHz (0.71 ? eV ) limited only by spontaneous recombination along the dipole-allowed transition. These results are reproduced with a simple and intuitive model that captures the essential features of the electron hyperfine interaction and its influence on ? .

Moody, G.; Feng, M.; McDonald, C.; Mirin, R. P.; Silverman, K. L.

2014-11-01

367

Effects of strain and quantum confinement in optically pumped nuclear magnetic resonance in GaAs: Interpretation guided by spin-dependent band structure calculations  

NASA Astrophysics Data System (ADS)

A combined experimental-theoretical study of optically pumped nuclear magnetic resonance (OPNMR) has been performed in a GaAs /A l0.1G a0.9As quantum well film epoxy bonded to a Si substrate with thermally induced biaxial strain. The photon energy dependence of the Ga OPNMR signal was recorded at magnetic fields of 4.9 and 9.4 T at a temperature of 4.8-5.4 K. The data were compared to the nuclear spin polarization calculated from the electronic structure and differential absorption to spin-up and spin-down states of the electron conduction band using a modified k .p model based on the Pidgeon-Brown model. Comparison of theory with experiment facilitated the assignment of features in the OPNMR energy dependence to specific interband Landau level transitions. The results provide insight into how effects of strain and quantum confinement are manifested in optical nuclear polarization in semiconductors.

Wood, R. M.; Saha, D.; McCarthy, L. A.; Tokarski, J. T.; Sanders, G. D.; Kuhns, P. L.; McGill, S. A.; Reyes, A. P.; Reno, J. L.; Stanton, C. J.; Bowers, C. R.

2014-10-01

368

Using Bio-Functionalized Magnetic Nanoparticles and Dynamic Nuclear Magnetic Resonance to Characterize the Time-Dependent Spin-Spin Relaxation Time for Sensitive Bio-Detection  

PubMed Central

In this work, we report the use of bio-functionalized magnetic nanoparticles (BMNs) and dynamic magnetic resonance (DMR) to characterize the time-dependent spin-spin relaxation time for sensitive bio-detection. The biomarkers are the human C-reactive protein (CRP) while the BMNs are the anti-CRP bound onto dextran-coated Fe3O4 particles labeled as Fe3O4-antiCRP. It was found the time-dependent spin-spin relaxation time, T2, of protons decreases as time evolves. Additionally, the ?T2 of of protons in BMNs increases as the concentration of CRP increases. We attribute these to the formation of the magnetic clusters that deteriorate the field homogeneity of nearby protons. A sensitivity better than 0.1 ?g/mL for assaying CRP is achieved, which is much higher than that required by the clinical criteria (0.5 mg/dL). The present MR-detection platform shows promise for further use in detecting tumors, viruses, and proteins. PMID:25397920

Liao, Shu-Hsien; Chen, Kuen-Lin; Wang, Chun-Min; Chieh, Jen-Jie; Horng, Herng-Er; Wang, Li-Min; Wu, C. H.; Yang, Hong-Chang

2014-01-01

369

Wheat bran biodegradation by Pleurotus ostreatus: a solid-state carbon-13 NMR study.  

PubMed

Solid-state (13)C nuclear magnetic resonance (NMR) and elemental analysis techniques were used to monitor the degradation of wheat bran by the white-rot fungus Pleurotus ostreatus during a 62-day cultivation period. The weight loss and in vitro organic matter digestibility of the substrate were also evaluated after fungal treatment. The (13)C NMR spectra of degraded wheat bran samples showed a lower content in carbohydrates and a higher content in aliphatic and carboxylic groups than the untreated control sample. In parallel, changes in the wheat bran elemental composition evidenced a decrease in carbon content and a concomitant increase in nitrogen and oxygen content during mycelium growth. These results clearly indicate the occurrence of progressive changes in the composition of wheat bran during fungal treatment and are interpreted in terms of preferential degradation of amorphous vs. crystalline polysaccharides by the fungal mycelium and accumulation of proteins in the substrate. At the end of the cultivation period, the treated samples experienced an average weight loss of 20% and an increase in organic matter digestibility of 17%. PMID:17920878

Locci, Emanuela; Laconi, Samuela; Pompei, Raffaello; Scano, Paola; Lai, Adolfo; Marincola, Flaminia Cesare

2008-07-01

370

Design of a triple resonance magic angle sample spinning probe for high field solid state nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

Standard design and construction practices used in building nuclear magnetic resonance (NMR) probes for the study of solid state samples become difficult if not entirely impractical to implement as the 1H resonance frequency approaches the self resonance frequency of commercial capacitors. We describe an approach that utilizes short variable transmission line segments as tunable reactances. Such an approach effectively controls stray reactances and provides a higher Q alternative to ceramic chip capacitors. The particular probe described is built to accommodate a 2.5 mm magic angle spinning rotor system, and is triply tuned to 13C, 15N, and 1H frequencies for use at 18.8 T (200, 80, and 800 MHz, respectively). Isolation of the three radio frequency (rf) channels is achieved using both a rejection trap and a transmission line notch filter. The compact geometry of this design allows three channels with high power handling capability to fit in a medium bore (63 mm) magnet. Extended time variable temperature operation is integral to the mechanical design, enabling the temperature control necessary for investigation of biological macromolecules. Accurate measurement of the air temperature near the sample rotor is achieved using a fiber optic thermometer, which does not interfere with the rf electronics. We also demonstrate that acceptable line shapes are only readily achieved using zero magnetic susceptibility wire in construction of the sample coil. Computer simulation of the circuit aided in the physical design of the probe. Representative data illustrating the efficiency, rf homogeneity, and signal to noise factor of the probe are presented.

Martin, Rachel W.; Paulson, Eric K.; Zilm, Kurt W.

2003-06-01

371

Mixing of parity of a nucleon pair at the nuclear surface due to the spin-orbit potential in 18F  

NASA Astrophysics Data System (ADS)

We investigate the structure of 18F with the microscopic wave function based on the three-body 16O+p +n model. In the calculation of the generator coordinate method of the three-body model, T =0 energy spectra of J?=1+ ,3+, and 5+ states and T =1 spectra of J?=0+ ,2+ states in 18F are described reasonably. Based on the dinucleon picture, the effect of the spin-orbit force on the T =0 and T =1 p n pairs around the 16O core is discussed. The T =1 pair in the J?=0+ state gains the spin-orbit potential energy involving the odd-parity mixing in the pair. The spin-orbit potential energy gain with the parity mixing is not so efficient for the T =0 pair in the J?=1+ state. The parity mixing in the pair is regarded as the internal symmetry breaking of the pair in the spin-orbit potential at the nuclear surface.

Kanada-En'yo, Yoshiko; Kobayashi, Fumiharu

2014-11-01

372

Slow Magic Angle Sample Spinning: A Non- or Minimally Invasive Method for High- Resolution 1H Nuclear Magnetic Resonance (NMR) Metabolic Profiling  

SciTech Connect

High resolution 1H magic angle spinning nuclear magnetic resonance (NMR), using a sample spinning rate of several kHz or more (i.e., high resolution-magic angle spinning (hr-MAS)), is a well established method for metabolic profiling in intact tissues without the need for sample extraction. The only shortcoming with hr-MAS is that it is invasive and is thus unusable for non-destructive detections. Recently, a method called slow-MAS, using the concept of two dimensional NMR spectroscopy, has emerged as an alternative method for non- or minimal invasive metabolomics in intact tissues, including live animals, due to the slow or ultra-slow-sample spinning used. Although slow-MAS is a powerful method, its applications are hindered by experimental challenges. Correctly designing the experiment and choosing the appropriate slow-MAS method both require a fundamental understanding of the operation principles, in particular the details of line narrowing due to the presence of molecular diffusion. However, these fundamental principles have not yet been fully disclosed in previous publications. The goal of this chapter is to provide an in depth evaluation of the principles associated with slow-MAS techniques by emphasizing the challenges associated with a phantom sample consisting of glass beads and H2O, where an unusually large magnetic susceptibility field gradient is obtained.

Hu, Jian Z.

2011-05-01

373

Nuclear spin relaxation driven by intermolecular dipolar interactions: the role of solute-solvent pair correlations in the modeling of spectral density functions.  

PubMed

Nuclear spin relaxation provides useful information related to the dynamics of molecular systems. When relaxation is driven by intermolecular dipolar interactions, the relevant spectral density functions (SDFs) also have significant contributions, in principle, from distant spins all over the dynamic range typically probed by NMR experiments such as NOESY. In this work, we investigate the intermolecular dipolar spin relaxation as driven by the relative diffusion of solvent and solute molecules taking place under a central force field, and we examine the relevant implications for (preferential) solvation studies. For this purpose, we evaluate the SDFs by employing a numerical approach based on spatial discretization of the time-propagation equation, and we supply an analytical solution for the simplest case of a steplike mean-field potential. Several situations related to different solute-solvent pair correlation functions are examined in terms of static/dynamic effects and relaxation modes, and some conclusions are drawn about the interpretation of NOE measurements. While we confirm previous results concerning the spoiling effect of long-range spins (Halle, B. J. Chem. Phys. 2003, 119, 12372), we also show that SDFs are sufficiently sensitive to pair correlation functions that useful, yet rather complicated, inferences can be made on the nature of the solvation shell. PMID:16539513

Frezzato, Diego; Rastrelli, Federico; Bagno, Alessandro

2006-03-23

374

Salinity-induced Patterns of Natural Abundance Carbon-13 and Nitrogen-15 in Plant Jan-Willem van Groenigen* and Chris van Kessel  

E-print Network

Salinity-induced Patterns of Natural Abundance Carbon-13 and Nitrogen-15 in Plant and Soil Jan, and the amount of fossil fuel derived CO2 in the atmosphere (ShearerAlthough it is estimated that salinity stress from the air, modeling 13 C concentrations in the plant terize the impact of salinity stress on natural

van Kessel, Chris

375

One- and two-dimensional 31P cross-polarization magic-angle-spinning nuclear magnetic resonance studies on two-spin systems with homonuclear dipolar coupling and J coupling  

NASA Astrophysics Data System (ADS)

The effect of dipolar interactions on the solid state 31P cross-polarization magic-angle-spinning (CP-MAS) nuclear magnetic resonance (NMR) line shapes for the coupled two-spin systems, sodium pyrophosphate decahydrate, Na4P2O7?10H2O, and tetraphenyl diphosphine-1-oxide, (C6H5)2PP(O)(C6H5)2, has been investigated. The one-dimensional (1D)CP-MAS spectra of Na4P2O7?10H2O shows spinning frequency dependent sideband splittings. A theory was developed to permit the calculation of the MAS NMR line shapes of the dipolar and J-coupled two-spin systems. An exact solution of the periodic Hamiltonian was obtained by the use of Floquet Hamiltonian theory. The experimental spectra of Na4P2O7?10H2O are well reproduced by the theoretical ones calculated from the present theory, in which the homonuclear dipolar interaction between the two 31P nuclei in the P2O74- group was taken into consideration. Our Hamiltonian also leads to calculated spectra which are in good agreement with the experimental observations even at low rotor spinning speeds. The two-dimensional J-resolved experiments, with rotationally synchronized acquisition in the t1 dimension, were performed for both Na4P2O7?10H2O and (C6H5)2PP(O)(C6H5)2. These experiments were found to be useful in distinguishing between the different mechanisms of the rotational sideband splitting of 1D spectra, as well as the dipolar interactions between spins with the same isotropic chemical shift, but different orientations of chemical shift tensors. These studies also allowed the identification of splittings caused by homonuclear J-coupled interactions, because the resolution of the 2D J-resolved spectra was greater than that of the 1D spectra.

Kubo, Atsushi; McDowell, Charles A.

1990-06-01

376

The structure of the complex of cellulose I with ethylenediamine by X-ray crystallography and cross-polarization\\/magic angle spinning 13 C nuclear magnetic resonance  

Microsoft Academic Search

X-ray crystallographic and cross-polarization\\/magic angle spinning 13C nuclear magnetic resonance techniques have been used to study an ethylenediamine (EDA)-cellulose I complex, a transient\\u000a structure in the cellulose I to cellulose IIII conversion. The crystal structure (space group P2\\u000a \\u000a 1\\u000a ; a = 4.546 Å, b = 11.330 Å, c = 10.368 Å and ? = 94.017°) corresponds to a one-chain unit cell with one glucosyl residue in the asymmetric unit, a

Masahisa Wada; Laurent Heux; Yoshiharu Nishiyama; Paul Langan

2009-01-01

377

Solid-state ‘‘magic-angle’’ sample-spinning nuclear magnetic resonance spectroscopic study of group III–V (13–15) semiconductors  

Microsoft Academic Search

We have obtained 27 Al, 69 Ga, 71 Ga, 113 In, and 115 In static and ‘‘magic-angle’’ sample-spinning (MASS) solid-state nuclear magnetic resonance (NMR) spectra of a series of polycrystalline III–V semiconductors (AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, and InSb) at magnetic field strengths of 8.45 and 11.7 T. Line-broadening mechanisms have been identified by

Oc Hee Han; Hye Kyung C. Timken; Eric Oldfield

1988-01-01

378

13C-13C Homonuclear Recoupling in Solid-State Nuclear Magnetic Resonance at a Moderately High Magic-Angle-Spinning Frequency  

PubMed Central

Two-dimensional 13C-13C correlation experiments are widely employed in structure determination of protein assemblies using solid-state nuclear magnetic resonance. Here, we investigate the process of 13C-13C magnetisation transfer at a moderate magic-angle-spinning frequency of 30 kHz using some of the prominent second-order dipolar recoupling schemes. The effect of isotropic chemical-shift difference and spatial distance between two carbons and amplitude of radio frequency on 1H channel on the magnetisation transfer efficiency of these schemes is discussed in detail. PMID:23326308

Mithu, Venus Singh; Bakthavatsalam, Subha; Madhu, Perunthiruthy K.

2013-01-01

379

THE EFFECTS OF PARAMAGNETIC RELAXATION REAGENTS ON 15N SPIN RELAXATION AND THE USE OF GD(DPM)3 AS A NITROGEN-15 NUCLEAR MAGNETIC RESONANCE SPIN LABEL  

EPA Science Inventory

Electron-nuclear relaxation times (T(1) sup e's) for (15)N and (13)C in natural abundance are measured for a series of amines of a wide range of pK(a)s using four paramagnetic relaxation reagents that are soluable in organic solutions. Cr(acac)3 and Cr(dpm)3 are seen to affect th...

380

Enhancing the Superconducting Transition Temperature of CeRh1-xIrxIn5 due to the Strong-Coupling Effects of Antiferromagnetic Spin Fluctuations: An In115 Nuclear Quadrupole Resonance Study  

NASA Astrophysics Data System (ADS)

We report on systematic evolutions of antiferromagnetic (AFM) spin fluctuations and unconventional superconductivity (SC) in heavy-fermion (HF) compounds CeRh1-xIrxIn5 via an In115 nuclear-quadrupole-resonance experiment. The nuclear spin-lattice relaxation rate 1/T1 has revealed the marked development of AFM spin fluctuations as approaching an AFM ordered state. Concomitantly, the superconducting transition temperature Tc and the energy gap ?0 increase drastically from Tc=0.4K and 2?0/kBTc=5 in CeIrIn5 up to Tc=1.2K and 2?0/kBTc=8.3 in CeRh0.3Ir0.7In5, respectively. The present work suggests that the AFM spin fluctuations in close proximity to the AFM quantum critical point are indeed responsible for the strong-coupling unconventional SC in HF compounds.

Kawasaki, Shinji; Yashima, Mitsuharu; Mugino, Yoichi; Mukuda, Hidekazu; Kitaoka, Yoshio; Shishido, Hiroaki; ?nuki, Yoshichika

2006-04-01

381

Carbon13 NMR spectroscopy  

Microsoft Academic Search

Features in this edition are references (over 1,000), profuse illustration, a discussion of modern pulse techniques for spectral analysis, and extensive and thorough cataloguing of chemical shift data (over 200 pages) in readily accessible form. An attractive feature is the use of structural formulae with shifts inscribed in the structure. This new edition has been completely revised to take into

E. Breitmaier; W. Voelter

1987-01-01

382

Use of carbon-13 as a population marker for Anopheles arabiensis in a sterile insect technique (SIT) context  

PubMed Central

Background Monitoring of sterile to wild insect ratios in field populations can be useful to follow the progress in genetic control programmes such as the Sterile Insect Technique (SIT). Of the numerous methods for marking insects most are not suitable for use in mass rearing and mass release. Suitable ones include dye marking, genetic marking and chemical marking. Methods The feasibility of using the stable isotope of carbon, 13C, as a potential chemical marker for Anopheles arabiensis was evaluated in the laboratory. Labeled-13C glucose was incorporated into the larval diet in a powder or liquid form. The contribution of adult sugar feeding to the total mosquito carbon pool and the metabolically active carbon pool was determined by tracing the decline of the enrichment of the adult male mosquito as it switched from a labeled larval diet to an unlabeled adult diet. This decline in the adult was monitored by destructive sampling of the whole mosquito and analyzed using isotope ratio mass spectrometry. Results A two-pool model was used to describe the decline of the 13C-enrichment of adult mosquitoes. The proportion of the total adult carbon pool derived from the adult sugar diet over the life span of mosquitoes was determined and the ratio of structural carbon, with a low turnover rate to metabolically active non-structural carbon was assessed. The uptake and turnover of sugar in the metabolically active fraction suggests that after 3 days >70% of the active fraction carbon is derived from sugar feeding (increasing to >90% by day 7), indicating the high resource demand of male mosquitoes. Conclusion It was possible to "fix" the isotopic label in adult An. arabiensis and to detect the label at an appropriate concentration up to 21 days post-emergence. The optimum labeling treatment would cost around 250 US$ per million mosquitoes. Stable isotope marking may thus aid research on the fate of released insects besides other population-based ecological studies. PMID:16445865

Hood-Nowotny, Rebecca; Mayr, Leo; Knols, Bart GJ

2006-01-01

383

Spatial and Temporal Variations in Stable Carbon (?13C) and Nitrogen (?15N) Isotopic Composition of Symbiotic Scleractinian Corals  

PubMed Central

Tropical scleractinian corals are considered autotrophic as they rely mainly on photosynthesis-derived nutrients transferred from their photosymbionts. Corals are also able to capture and ingest suspended particulate organic matter, so heterotrophy can be an important supplementary trophic pathway to optimize coral fitness. The aim of this in situ study was to elucidate the trophic status of 10 coral species under contrasted environmental conditions in a French Polynesian lagoon. Carbon (?13C) and nitrogen (?15N) isotopic compositions of coral host tissues and photosymbionts were determined at 3 different fringing reefs during wet and dry seasons. Our results highlighted spatial variability in stable isotopic compositions of both coral host tissues and photosymbionts. Samples from the site with higher level of suspended particulate matter were 13C-depleted and 15N-enriched relative to corals and photosymbionts from less turbid sites. However, differences in both ?13C and ?15N between coral host tissues and their photosymbionts (?host-photosymbionts 13C and ?host-photosymbionts 15N) were small (0.27 ± 0.76‰ and 1.40 ± 0.90‰, respectively) and similar at all sites, thus indicating no general increases in the heterotrophic pathway. Depleted ?13C and enriched ?15N values of coral host tissues measured at the most turbid site were explained by changes in isotopic composition of the inorganic nutrients taken up by photosymbionts and also by changes in rate of isotopic fractionation with environmental conditions. Our results also highlighted a lack of significant temporal variations in ?13C and ?15N values of coral host and photosymbiont tissues and in ?host-photosymbionts 13C and ?host-photosymbionts 15N values. This temporal stability indicated that corals remained principally autotrophic even during the wet season when photosymbiont densities were lower and the concentrations of phytoplankton were higher. Increased coral heterotrophy with higher food availability thus appears to be species-specific. PMID:24312542

Nahon, Sarah; Richoux, Nicole B.; Kolasinski, Joanna; Desmalades, Martin; Ferrier Pages, Christine; Lecellier, Gael; Planes, Serge; Berteaux Lecellier, Véronique

2013-01-01

384

Twelve-spin "Schrodinger cat"  

E-print Network

Pseudopure "cat" state, a superposition of quantum states with all spins up and all spins down, is experimentally demonstrated for a system of twelve dipolar-coupled nuclear spins of fully 13C-labeled benzene molecule oriented in a liquid-crystalline matrix.

Jae-Seung Lee; A. K. Khitrin

2005-08-01

385

Carbon13 solid state NMR investigation and modeling of the morphological reorganization in regenerated cellulose fibres induced by controlled acid hydrolysis  

Microsoft Academic Search

CPMAS carbon-13 NMR has been used to follow structural changes affecting regenerated cellulose fibres during hydrolysis by\\u000a mineral acids. The C4 envelope of regenerated cellulose was deconvoluted into separate peaks, for ordered (crystal), part-ordered\\u000a (surface) and disordered (non-crystal) polymer, which allowed calculation of average crystal lateral sizes, in good agreement\\u000a with WAXD data. A geometrical model has been used to

Roger Ibbett; Dimitra Domvoglou; Franz Wortmann; K. Christian Schuster

2010-01-01

386

Correlation between. beta. -hydrogen isotope effects on carbon-13 NMR chemical shifts in unsaturated systems and the strength of hyperconjugative interactions  

Microsoft Academic Search

beta..-Hydrogen isotope effects on the carbon-13 NMR chemical shifts of the trigonal carbon in CLâC(R)=X (L = H or D) are reported for 15 substances in which the positive charge density at the trigonal carbon is regulated through systematic variation of R and X. A linear relationship is found between these isotope effects and the chemical shifts of the trigonal

Cheryl H. Arrowsmith; A. Jerry. Kresge

1986-01-01

387

Nuclear spin Hall and Klein tunneling effects during oxidation with electric and magnetic field inductions in graphene.  

PubMed

The recent observation of the explosive oxidation of graphene with enhancement for decreasing temperature and the requirements for synchronizing oxidants for collective oxidation-reduction (redox) reactions presented a chemical scenario for the thermal harvesting by the magnetic spin Hall Effect. More experimental data are presented to demonstrate such spin Hall Effect by determining the influence of spins of so-called spectator fermionic cations. Furthermore, the so-called spectator bosonic cations are discovered to cause a Klein tunneling effect during the redox reaction of graphene. The Na(+) and K(+), fermionic cations and the Mg(2+) and Ca(2+), bosonic cations were observed and compared under a variety of experimental conditions: adiabatic reactions with initial temperatures (18-22 °C); reactions toward infinite dilution; isothermal reactions under nonadiabatic conditions at low temperature of 18 °C; reactions under paramagnetic O(2) or diamagnetic N(2) atmospheres of different permeabilities; reactions in applied and no applied external magnetic field; and reactions toward excess concentrations of common and uncommon Na(+) and Mg(2+) cations. The observed reaction kinetics and dynamics under these various, diverse conditions are consistent with the spin Hall mechanism, energy harvesting and short time violation of Second Law of Thermodynamics for redox reactions of graphene by the Na(+)K(+) mixture and are consistent with the Klein tunnel mechanism for the redox reactions of graphene by the Mg(2+)Ca(2+) mixture. Mixed spin Hall and Klein tunnel mechanisms are discovered to slow and modulate explosive redox reactions. Such spin Hall Effect also gives explanation of recent tunneling of electrons through boron nitride. PMID:23108034

Little, Reginald B; McClary, Felicia; Rice, Bria; Jackman, Corine; Mitchell, James W

2012-12-14

388

Nuclear  

NSDL National Science Digital Library

What part does nuclear energy play in satisfying energy demands? This informational piece, part of a series about the future of energy, introduces students to the uranium atom as an energy source. Here students read about the history of nuclear energy, how energy is derived from uranium, and benefits of nuclear energy. Information is also provided about limitations, particularly disposal problems and radioactivity, and geographical considerations of nuclear power in the United States. Thought-provoking questions afford students chances to reflect on what they've read about the uses of nuclear power. Articles and information on new nuclear plant design and nuclear accidents are available from a sidebar. Five energy-related PBS NewsHour links are provided. A web link to the U.S. Nuclear Regulatory Commission is included. Copyright 2005 Eisenhower National Clearinghouse

Iowa Public Television. Explore More Project

2004-01-01

389

(1)H-(13)C Hetero-nuclear dipole-dipole couplings of methyl groups in stationary and magic angle spinning solid-state NMR experiments of peptides and proteins.  

PubMed

(13)C NMR of isotopically labeled methyl groups has the potential to combine spectroscopic simplicity with ease of labeling for protein NMR studies. However, in most high resolution separated local field experiments, such as polarization inversion spin exchange at the magic angle (PISEMA), that are used to measure (1)H-(13)C hetero-nuclear dipolar couplings, the four-spin system of the methyl group presents complications. In this study, the properties of the (1)H-(13)C hetero-nuclear dipolar interactions of (13)C-labeled methyl groups are revealed through solid-state NMR experiments on a range of samples, including single crystals, stationary powders, and magic angle spinning of powders, of (13)C(3) labeled alanine alone and incorporated into a protein. The spectral simplifications resulting from proton detected local field (PDLF) experiments are shown to enhance resolution and simplify the interpretation of results on single crystals, magnetically aligned samples, and powders. The complementarity of stationary sample and magic angle spinning (MAS) measurements of dipolar couplings is demonstrated by applying polarization inversion spin exchange at the magic angle and magic angle spinning (PISEMAMAS) to unoriented samples. PMID:19896874

Wu, Chin H; Das, Bibhuti B; Opella, Stanley J

2010-02-01

390

1H- 13C hetero-nuclear dipole-dipole couplings of methyl groups in stationary and magic angle spinning solid-state NMR experiments of peptides and proteins  

NASA Astrophysics Data System (ADS)

13C NMR of isotopically labeled methyl groups has the potential to combine spectroscopic simplicity with ease of labeling for protein NMR studies. However, in most high resolution separated local field experiments, such as polarization inversion spin exchange at the magic angle (PISEMA), that are used to measure 1H- 13C hetero-nuclear dipolar couplings, the four-spin system of the methyl group presents complications. In this study, the properties of the 1H- 13C hetero-nuclear dipolar interactions of 13C-labeled methyl groups are revealed through solid-state NMR experiments on a range of samples, including single crystals, stationary powders, and magic angle spinning of powders, of 13C 3 labeled alanine alone and incorporated into a protein. The spectral simplifications resulting from proton detected local field (PDLF) experiments are shown to enhance resolution and simplify the interpretation of results on single crystals, magnetically aligned samples, and powders. The complementarity of stationary sample and magic angle spinning (MAS) measurements of dipolar couplings is demonstrated by applying polarization inversion spin exchange at the magic angle and magic angle spinning (PISEMAMAS) to unoriented samples.

Wu, Chin H.; Das, Bibhuti B.; Opella, Stanley J.

2010-02-01

391

27 Al and 29 Si magic angle spinning nuclear magnetic resonance spectroscopy of Al-substituted tobermorites  

Microsoft Academic Search

Solid-state27Al and29Si NMR spectroscopy with magic angle spinning (MAS) of samples was used to study several 1.13 nm tobermorites, most of which were deliberately substituted with aluminium.27Al MASNMR clearly showed that aluminium is tetrahedrally co-ordinated in tobermorite structures. In addition two different aluminium environments resonating at ~ 57 and 64 ppm from [Al(H2O)6]3+ were detected.29Si MASNMR of pure, anomalous tobermorites

Sridhar Komarneni; Rustum Roy; Della M. Roy; Colin A. Fyfe; Gordon J. Kennedy; Aksel A. Bothner-By; Josef Dadok; A Scott Chesnick

1985-01-01

392

Control of Non-Resonant Effects in a Nuclear Spin Quantum Computer with a Large Number of Qubits  

E-print Network

We discuss how to simulate simple quantum logic operations with a large number of qubits. These simulations are needed for experimental testing of scalable solid-state quantum computers. Quantum logic for remote qubits is simulated in a spin chain. Analytical estimates are presented for possible correlated errors caused by non-resonant transitions. A range of parameters is given in which non-resonant effects can be minimized.

G. P. Berman; G. D. Doolen; D. I. Kamenev; V. I. Tsifrinovich

2001-03-03

393

Spin-noise correlations and spin-noise exchange driven by low-field spin-exchange collisions  

NASA Astrophysics Data System (ADS)

The physics of spin-exchange collisions have fueled several discoveries in fundamental physics and numerous applications in medical imaging and nuclear magnetic resonance. We report on the experimental observation and theoretical justification of spin-noise exchange, the transfer of spin noise from one atomic species to another. The signature of spin-noise exchange is an increase of the total spin-noise power at low magnetic fields, on the order of 1 mG, where the two-species spin-noise resonances overlap. The underlying physical mechanism is the two-species spin-noise correlation induced by spin-exchange collisions.

Dellis, A. T.; Loulakis, M.; Kominis, I. K.

2014-09-01

394

Recent developments in solid-state magic-angle spinning, nuclear magnetic resonance of fully and significantly isotopically labelled peptides and proteins.  

PubMed Central

In recent years, a large number of solid-state nuclear magnetic resonance (NMR) techniques have been developed and applied to the study of fully or significantly isotopically labelled ((13)C, (15)N or (13)C/(15)N) biomolecules. In the past few years, the first structures of (13)C/(15)N-labelled peptides, Gly-Ile and Met-Leu-Phe, and a protein, Src-homology 3 domain, were solved using magic-angle spinning NMR, without recourse to any structural information obtained from other methods. This progress has been made possible by the development of NMR experiments to assign solid-state spectra and experiments to extract distance and orientational information. Another key aspect to the success of solid-state NMR is the advances made in sample preparation. These improvements will be reviewed in this contribution. Future prospects for the application of solid-state NMR to interesting biological questions will also briefly be discussed. PMID:15306412

Straus, Suzana K

2004-01-01

395

Orientation of functional groups of soil organic matter on the surface of water repellent soils determined by pulse saturation magic angle spinning (PSTMAS) nuclear magnetic resonance (NMR) spectroscopy  

NASA Astrophysics Data System (ADS)

Orientation of functional groups of soil organic matter on soil particles plays a crucial role in the occurrence of soil water repellency. In addition to a general method to characterize soil organic matter using cross polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR) technique, we determined the surface orientation of functional groups in water repellent soils by using pulse saturation magic angle spinning (PSTMAS) NMR technique. A preliminary experiment confirmed that the PSTMAS NMR spectrum successfully determined the high mobility of methyl group of octadecylsilylated silica gels when a comparison was made with that of CPMAS NMR. This means that the methyl group oriented towards the outside of the silica gel particle. Similarly, for an experimental system consisting of mixtures of octadecylsilylated silica gel and dimethyl sulfoxide (DMSO), the extremely high mobility of methyl group derived from DMSO was detected using the same methodology. For water repellent soils from Japan and New Zealand, it was found that the methyl and methylene groups were highly mobile. In contrast, the NMR signals of aromatic moiety, another hydrophobic moiety of soil organic matter, were not as intense in PSTMAS compared with CPMAS. From these results, we conclude that alkyl moiety (methyl and methylene groups) would be oriented towards the outside of the soil particle and would play an important role in the appearance of water repellency of soils.

Hiradate, Syuntaro; Kawamoto, Ken; Senani Wijewardana, Nadeeka; Müller, Karin; Møldrup, Per; Clothier, Brent; Komatsu, Toshiko

2014-05-01

396

NMR multiple quantum coherences in quasi-one-dimensional spin systems: Comparison with ideal spin-chain dynamics  

E-print Network

The [superscript 19]F spins in a crystal of fluorapatite have often been used to experimentally approximate a one-dimensional spin system. Under suitable multipulse control, the nuclear-spin dynamics may be modeled to first ...

Zhang, Wenxian

397

Leading Edge Spinning the Web of Cell Fate  

E-print Network

Leading Edge Minireview Spinning the Web of Cell Fate Kevin Van Bortle1 and Victor G. Corces1,* 1 involved in spinning the web of cell fate. Chromatin at the Nuclear Lamina The nuclear lamina is a thin

Corces, Victor G.

398

Carbon-13 Urea Breath Test for Helicobacter Pylori Infection in Patients with Uninvestigated Ulcer-Like Dyspepsia  

PubMed Central

Background Dyspepsia is a condition defined by chronic pain or discomfort in the upper gastrointestinal tract that can be caused by Helicobacter pylori. The carbon-13 urea breath test (13C UBT) is a non-invasive test to detect H. pylori. Objectives We aimed to determine the diagnostic accuracy and clinical utility of the 13C UBT in adult patients with ulcer-like dyspepsia who have no alarm features. Data Sources A literature search was performed using Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid Embase, the Wiley Cochrane Library, and the Centre for Reviews and Dissemination database, for studies published between 2003 and 2012. Review Methods We abstracted the sensitivity and specificity, which were calculated against a composite reference standard. Summary estimates were obtained using bivariate random effects regression analysis. Results From 19 diagnostic studies, the 13C UBT summary estimates were 98.1% (95% confidence interval [CI], 96.3–99.0) for sensitivity and 95.1% (95% CI, 90.3–97.6) for specificity. In 6 studies that compared the 13C UBT with serology, the 113C UBT sensitivity was 95.0% (95% CI, 90.1–97.5) and specificity was 91.6 % (95% CI, 81.3–96.4). The sensitivity and specificity for serology were 92.9% (95% CI, 82.6–97.3) and 71.1% (95% CI, 63.8–77.5), respectively. In 1 RCT, symptom resolution, medication use, and physician visits were similar among the 13C UBT, serology, gastroscopy, or empirical treatment arms. However, patients tested with 13C UBT reported higher dyspepsia-specific quality of life scores. Limitations Processing of the 13C UBT results can vary according to many factors. Further, the studies showed significant heterogeneity and used different composite reference standards. Conclusions The 13C UBT is an accurate test with high sensitivity and specificity. Compared with serology, it has higher specificity. There is a paucity of data on the 13C UBT beyond test accuracy. Plain Language Summary Breath test for detecting bacteria in patients with ulcer-like symptoms Dyspepsia is a condition that causes long-term pain or discomfort in the upper abdomen. Symptoms can include heartburn, burping, bloating, nausea, or slow digestion. Dyspepsia can be caused by a bacterium that also causes ulcers and stomach cancer. Half of the world’s people are believed to be infected with these bacteria. A test has been developed to detect the bacteria in a breath sample. Our review determined the accuracy of this breath test in adults with ulcer-like symptoms. From 19 studies, the breath test correctly identified 98% of patients with the bacteria and 95% of patients without the bacteria, as determined by a reference standard. Six studies compared the breath test to a blood test that is currently used. Both the breath and blood tests performed well in correctly identifying patients with the bacteria. However, the blood test was incorrectly positive in 20 more patients who did not have the bacteria according to the breath test. This means that more patients would have received unnecessary treatment. Thus, the breath test is an accurate test to detect the bacteria in adult patients who have ulcer-like symptoms. But the many differences among the studies in our review included several steps taken to perform the breath test and the reference standards used to compare a blood test with the breath test. PMID:24228082

Ling, D

2013-01-01

399

The PI4+ cation has an extremely large negative 31P nuclear magnetic resonance chemical shift, due to spin-orbit coupling: A quantum-chemical prediction and its confirmation by solid-state nuclear magnetic resonance spectroscopy  

NASA Astrophysics Data System (ADS)

We have used density-functional methods including explicit spin-orbit corrections, to calculate the 31P nuclear magnetic resonance (NMR) chemical shifts of the tetrahalophosphonium cations PX4+ (X=F, Cl, Br, I). The agreement between theory and experimental literature data for PF4+, PCl4+, and PBr4+ is good. For PI4+, the calculations predict an extremely negative (high-field) shift of approximately -520 ppm, due to particularly large spin-orbit contributions from the four heavy iodine substituents, transmitted to the phosphorus nucleus by a very effective Fermi-contact mechanism. No experimental data were available for PI4+. We have, therefore, prepared the compounds PI4AsF6, PI4SbF6, PI4AlI4, and PI4GaI4 and recorded their solid-state 31P NMR spectra, both with and without magic-angle spinning of the sample. Using the noncoordinating AsF6- and SbF6- anions, the measured isotropic shifts are -519 and -517 ppm, respectively, in good agreement with the predicted extreme value for the isolated cation. In contrast, ?31P values of only -304 and -295 ppm are found for PI4AlI4 and PI4GaI4, respectively. The large deviation from the isolated-cation limit in the latter two compounds is probably related to significant I⋯I secondary bonding interactions, as found in the solid-state structure of PI4AlI4. The observed solid-state shift tensors are discussed. The present results disagree clearly with previous claims for the synthesis of PI5.

Kaupp, Martin; Aubauer, Christoph; Engelhardt, Günter; Klapötke, Thomas M.; Malkina, Olga L.

1999-02-01

400

Microtesla MRI with dynamic nuclear polarization  

PubMed Central

Magnetic resonance imaging at microtesla fields is a promising imaging method that combines the pre-polarization technique and broadband signal reception by superconducting quantum interference device (SQUID) sensors to enable in vivo MRI at microtesla-range magnetic fields similar in strength to the Earth magnetic field. Despite significant advances in recent years, the potential of microtesla MRI for biomedical imaging is limited by its insufficient signal-to-noise ratio due to a relatively low sample polarization. Dynamic nuclear polarization (DNP) is a widely used approach that allows polarization enhancement by two-four orders of magnitude without an increase in the polarizing field strength. In this work, the first implementation of microtesla MRI with Overhauser DNP and SQUID signal detection is described. The first measurements of carbon-13 NMR spectra at microtesla fields are also reported. The experiments were performed at the measurement field of 96 microtesla, corresponding to Larmor frequency of 4 kHz for protons and 1 kHz for carbon-13. The Overhauser DNP was carried out at 3.5 –5.7 mT field using rf irradiation at 120 MHz. Objects for imaging included water phantoms and a cactus plant. Aqueous solutions of metabolically relevant sodium bicarbonate, pyruvate, alanine, and lactate, labeled with carbon-13, were used for NMR studies. All the samples were doped with TEMPO free radicals. The Overhauser DNP enabled nuclear polarization enhancement by factor as high as ?95 for protons and as high as ?200 for carbon-13, corresponding to thermal polarizations at 0.33 T and 1.1 T fields, respectively. These results demonstrate that SQUID-based microtesla MRI can be naturally combined with Overhauser DNP in one system, and that its signal-to-noise performance is greatly improved in this case. They also suggest that microtesla MRI can become an efficient tool for in vivo imaging of hyperpolarized carbon-13, produced by the low-temperature dissolution DNP. PMID:20843715

Zotev, Vadim S.; Owens, Tuba; Matlashov, Andrei N.; Savukov, Igor M.; Gomez, John J.; Espy, Michelle A.

2010-01-01

401

Microtesla MRI with dynamic nuclear polarization  

NASA Astrophysics Data System (ADS)

Magnetic resonance imaging at microtesla fields is a promising imaging method that combines the pre-polarization technique and broadband signal reception by superconducting quantum interference device (SQUID) sensors to enable in vivo MRI at microtesla-range magnetic fields similar in strength to the Earth magnetic field. Despite significant advances in recent years, the potential of microtesla MRI for biomedical imaging is limited by its insufficient signal-to-noise ratio due to a relatively low sample polarization. Dynamic nuclear polarization (DNP) is a widely used approach that allows polarization enhancement by 2-4 orders of magnitude without an increase in the polarizing field strength. In this work, the first implementation of microtesla MRI with Overhauser DNP and SQUID signal detection is described. The first measurements of carbon-13 NMR spectra at microtesla fields are also reported. The experiments were performed at the measurement field of 96 ?T, corresponding to Larmor frequency of 4 kHz for protons and 1 kHz for carbon-13. The Overhauser DNP was carried out at 3.5-5.7 mT fields using rf irradiation at 120 MHz. Objects for imaging included water phantoms and a cactus plant. Aqueous solutions of metabolically relevant sodium bicarbonate, pyruvate, alanine, and lactate, labeled with carbon-13, were used for NMR studies. All the samples were doped with TEMPO free radicals. The Overhauser DNP enabled nuclear polarization enhancement by factor as large as -95 for protons and as large as -200 for carbon-13, corresponding to thermal polarizations at 0.33 T and 1.1 T fields, respectively. These results demonstrate that SQUID-based microtesla MRI can be naturally combined with Overhauser DNP in one system, and that its signal-to-noise performance is greatly improved in this case. They also suggest that microtesla MRI can become an efficient tool for in vivo imaging of hyperpolarized carbon-13, produced by low-temperature dissolution DNP.

Zotev, Vadim S.; Owens, Tuba; Matlashov, Andrei N.; Savukov, Igor M.; Gomez, John J.; Espy, Michelle A.

2010-11-01

402

Spin Echo Modulation Caused by the Quadrupole Interaction and Multiple Spin Echoes  

Microsoft Academic Search

A spin echo amplitude for a spin system consisting of one nuclear species of spin I with a large Zeeman energy and a small quadrupole interaction has been calculated for the case the excitation is carried out by two succeeding arbitrary rf pulses. The spin echo amplitude shows an oscillatory behavior which depends on the time interval between the first

Hisashi Abe; Hiroshi Yasuoka; Akira Hirai

1966-01-01

403

Many-body singlets by dynamic spin polarization  

E-print Network

We show that dynamic spin polarization by collective raising and lowering operators can drive a spin ensemble from arbitrary initial state to many-body singlets, the zero-collective-spin states with large scale entanglement. For an ensemble of $N$ arbitrary spins, both the variance of the collective spin and the number of unentangled spins can be reduced to O(1) (versus the typical value of O(N)), and many-body singlets can be occupied with a population of $\\sim 20 %$ independent of the ensemble size. We implement this approach in a mesoscopic ensemble of nuclear spins through dynamic nuclear spin polarization by an electron. The result is of two-fold significance for spin quantum technology: (1) a resource of entanglement for nuclear spin based quantum information processing; (2) a cleaner surrounding and less quantum noise for the electron spin as the environmental spin moments are effectively annihilated.

Wang Yao

2011-01-20

404

Synthesis of empagliflozin, a novel and selective sodium-glucose co-transporter-2 inhibitor, labeled with carbon-14 and carbon-13.  

PubMed

Empagliflozin, (2S,3R,4R,5S,6R)-2-[4-chloro-3-[[4-[(3S)-oxolan-3-yl]oxyphenyl]methyl]phenyl]-6-(hydroxymethyl)oxane-3,4,5-triol was recently approved by the FDA for the treatment of chronic type 2 diabetes mellitus. Herein, we report the synthesis of carbon-13 and carbon-14 labeled empagliflozin. Carbon-13 labeled empagliflozin was prepared in five steps and in 34% overall chemical yield starting from the commercially available ?-D-glucose-[(13)C6]. For the radiosynthesis, the carbon-14 atom was introduced in three different positions of the molecule. In the first synthesis, Carbon-14 D-(+)-gluconic acid ?-lactone was used to prepare specifically labeled empagliflozin in carbon-1 of the sugar moiety in four steps and in 19% overall radiochemical yield. Carbon-14 labeled empagliflozin with the radioactive atom in the benzylic position was obtained in eight steps and in 7% overall radiochemical yield. In the last synthesis carbon-14 uniformly labeled phenol was used to give [(14)C]empagliflozin in eight steps and in 18% overall radiochemical yield. In all these radiosyntheses, the specific activities of the final compounds were higher than 53?mCi/mmol, and the radiochemical purities were above 98.5%. PMID:25332189

Hrapchak, Matt; Latli, Bachir; Wang, Xiao-Jun; Lee, Heewon; Campbell, Scot; Song, Jinhua J; Senanayake, Chris H

2014-10-01

405

Low Energy Nuclear Reaction Cross Sections for a Secondary High-Spin Isomeric Nuclear Beam (^18F^m) in Silicon  

Microsoft Academic Search

A 30 MeV\\/u primary ^17O primary beam has been used to produce a 22.3 MeV\\/u ^18F^m ( J^pi=5^+, E_x=1.1 MeV) isomeric secondary beam via the single nucleon transfer reaction ^17O(^12C,^11B)^18F. The total nuclear reaction cross section for ^18F^m , ^18F_g.s and ^16O in silicon were measured, and will be presented, in an X-Y-DeltaE-E detector telescope consisting of seven thin silicon

D. A. Roberts; F. D. Becchetti; J. Janecke; M. Y. Lee; T. W. O'Donnell; K. Pham; R. E. Warner; R. M. Ronningen; H. W. Wilschut

1996-01-01

406

Photochemically induced nuclear spin polarization in reaction centers of photosystem II observed by 13C-solid-state NMR reveals a strongly asymmetric electronic structure of the P680.+ primary donor chlorophyll  

PubMed Central

We report 13C magic angle spinning NMR observation of photochemically induced dynamic nuclear spin polarization (photo- CIDNP) in the reaction center (RC) of photosystem II (PS2). The light-enhanced NMR signals of the natural abundance 13C provide information on the electronic structure of the primary electron donor P680 (chlorophyll a molecules absorbing around 680 nm) and on the pz spin density pattern in its oxidized form, P680?. Most centerband signals can be attributed to a single chlorophyll a (Chl a) cofactor that has little interaction with other pigments. The chemical shift anisotropy of the most intense signals is characteristic for aromatic carbon atoms. The data reveal a pronounced asymmetry of the electronic spin density distribution within the P680?. PS2 shows only a single broad and intense emissive signal, which is assigned to both the C-10 and C-15 methine carbon atoms. The spin density appears shifted toward ring III. This shift is remarkable, because, for monomeric Chl a radical cations in solution, the region of highest spin density is around ring II. It leads to a first hypothesis as to how the planet can provide itself with the chemical potential to split water and generate an oxygen atmosphere using the Chl a macroaromatic cycle. A local electrostatic field close to ring III can polarize the electronic charge and associated spin density and increase the redox potential of P680 by stabilizing the highest occupied molecular orbital, without a major change of color. This field could be produced, e.g., by protonation of the keto group of ring V. Finally, the radical cation electronic structure in PS2 is different from that in the bacterial RC, which shows at least four emissive centerbands, indicating a symmetric spin density distribution over the entire bacteriochlorophyll macrocycle. PMID:10944191

Matysik, Jörg; Alia; Gast, Peter; van Gorkom, Hans J.; Hoff, Arnold J.; de Groot, Huub J. M.

2000-01-01

407

BLACK HOLE-NEUTRON STAR MERGERS WITH A HOT NUCLEAR EQUATION OF STATE: OUTFLOW AND NEUTRINO-COOLED DISK FOR A LOW-MASS, HIGH-SPIN CASE  

SciTech Connect

Neutrino emission significantly affects the evolution of the accretion tori formed in black hole-neutron star mergers. It removes energy from the disk, alters its composition, and provides a potential power source for a gamma-ray burst. To study these effects, simulations in general relativity with a hot microphysical equation of state (EOS) and neutrino feedback are needed. We present the first such simulation, using a neutrino leakage scheme for cooling to capture the most essential effects and considering a moderate mass (1.4 M{sub ?} neutron star, 5.6 M{sub ?} black hole), high-spin (black hole J/M {sup 2} = 0.9) system with the K{sub 0} = 220 MeV Lattimer-Swesty EOS. We find that about 0.08 M{sub ?} of nuclear matter is ejected from the system, while another 0.3 M{sub ?} forms a hot, compact accretion disk. The primary effects of the escaping neutrinos are (1) to make the disk much denser and more compact, (2) to cause the average electron fraction Y{sub e} of the disk to rise to about 0.2 and then gradually decrease again, and (3) to gradually cool the disk. The disk is initially hot (T ? 6 MeV) and luminous in neutrinos (L{sub ?} ? 10{sup 54} erg s{sup –1}), but the neutrino luminosity decreases by an order of magnitude over 50 ms of post-merger evolution.

Deaton, M. Brett; Duez, Matthew D. [Department of Physics and Astronomy, Washington State University, Pullman, WA 99164 (United States); Foucart, Francois; O'Connor, Evan [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, Ontario M5S 3H8 (Canada); Ott, Christian D.; Scheel, Mark A.; Szilagyi, Bela [TAPIR, MC 350-17, California Institute of Technology, Pasadena, CA 91125 (United States); Kidder, Lawrence E.; Muhlberger, Curran D., E-mail: mbdeaton@wsu.edu, E-mail: m.duez@wsu.edu [Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853 (United States)

2013-10-10

408

THz Dynamic Nuclear Polarization NMR  

E-print Network

Dynamic nuclear polarization (DNP) increases the sensitivity of nuclear magnetic resonance (NMR) spectroscopy by using high frequency microwaves to transfer the polarization of the electrons to the nuclear spins. The ...

Nanni, Emilio Alessandro

409

Nonergodic nuclear depolarization in nanocavities  

Microsoft Academic Search

Recently, it has been observed that the effective dipolar interactions between nuclear spins of spin-carrying molecules of a gas in a closed nano-cavities are independent of the spacing between all spins. We derive exact time-dependent polarization for all spins in spin-1\\/2 ensemble with spatially independent effective dipolar interactions. If the initial polarization is on a single (first) spin,$P_1(0)= 1$ then

E. B. Fel'Dman; M. G. Rudavets

2004-01-01

410

CARBON-13 NMR Studies of Liquid Crystals: Nematic Ordering and the Dynamics of Non-Equilibrium Systems  

NASA Astrophysics Data System (ADS)

This dissertation describes the study of three aspects of liquid crystal behavior by the use of ^{13}C NMR. One area concerned theories of nematic ordering. The deGennes theory of nematic to smectic A liquid crystal phase transitions was investigated experimentally, and the results confirmed the theoretical work. Also, several functional forms for the temperature dependence of the ordering of nematic liquid crystal were derived and investigated experimentally. The second topic was the development of a technique to study the ordering of fluorosubstituted liquid crystals. The technique was first used to determine the order parameters of a monofluorosubstituted ring, and the results compared favorably to existing methods. The technique was extended, and, for the first time, three order parameters of a 1,3,4 -trisubstituted phenyl ring were determined. The final area was an investigation of the dynamic reorientation of liquid crystals forced away from equilibrium. To study this, the method of rapidly decelerated sample spinning was developed, which allows precise computer control of the sample deceleration and data acquisition. It was determined that different molecular segments macroscopically reoriented at different rates, and when the system was driven far from equilibrium, the results were consistent with dual alignment of the liquid crystal directors.

Magnuson, Matthew L.

411

Assessment of the specific absorption rate and calibration of decoupling parameters for proton decoupled carbon-13 MR spectroscopy at 3.0 T.  

PubMed

A strategy for proton decoupled carbon-13 MR spectroscopy ((1H)-13C MRS) with a strong static magnetic field (3.0 T) in vivo was investigated. The proton decoupling improves the signal-to-noise ratio, however, the effect of the decoupling power on the human body, especially in strong magnetic fields, should be considered. In order to establish a technique for monitoring the metabolism of glucose in the liver using (1H)-13C MRS at 3.0 T, two phantom experiments were performed. To assess whether the decoupling energy conformed to SAR limits defined by the IEC, temperature rises inside an agar gel phantom were monitored during a (1H)-13C MRS experiment. Then, the decoupling conditions of a glucose solution phantom were systematically optimized with combinations of decoupling bandwidth and power. The reliability of this procedure was discussed in conjunction with IEC guidelines. PMID:16036162

Saito, Moyoko; Matsuda, Tsuyoshi; Tropp, James; Inubushi, Toshiro; Nakai, Toshiharu

2005-08-01

412

Spinning angle optical calibration apparatus  

DOEpatents

An optical calibration apparatus is provided for calibrating and reproducing spinning angles in cross-polarization, nuclear magnetic resonance spectroscopy. An illuminated magnifying apparatus enables optical setting an accurate reproducing of spinning "magic angles" in cross-polarization, nuclear magnetic resonance spectroscopy experiments. A reference mark scribed on an edge of a spinning angle test sample holder is illuminated by a light source and viewed through a magnifying scope. When the "magic angle" of a sample material used as a standard is attained by varying the angular position of the sample holder, the coordinate position of the reference mark relative to a graduation or graduations on a reticle in the magnifying scope is noted. Thereafter, the spinning "magic angle" of a test material having similar nuclear properties to the standard is attained by returning the sample holder back to the originally noted coordinate position.

Beer, Stephen K. (Morgantown, WV); Pratt, II, Harold R. (Morgantown, WV)

1991-01-01

413

Determination of the position of the N-O function in substituted pyrazine N-oxides by chemometric analysis of carbon-13 nuclear magnetic resonance data  

NASA Astrophysics Data System (ADS)

Investigations were carried out applying NMR spectroscopy for the unambiguous determination of the position of the N-oxide function in a set of 2-substituted pyrazine N-oxides synthesized in our group. Applying chemometric techniques of multivariate analysis to the 13C NMR chemical shifts data set, useful relationships for identifying the position of the N-oxide group relative to the substituent were unraveled. The relationships obtained were rationalized in terms of the molecular structures and refined. As a result, an index of N-oxidation (INOx) was defined, computed simply contrasting the average 13C NMR chemical shifts of each pair of carbon atoms bonded to a nitrogen atom. The effect of the substituent was included through a factor x (subscript of INO) close to unity, multiplying the average containing the substituted carbon atom. The approach was successful in recognizing the position of the N-oxide in all the cases studied, as revealed by the sign of INOx (positive for 1-N-oxides and negative for 4-N-oxides). The scope of the methodology was further tested using the 13C NMR chemical shifts of disubstituted pyrazine N-oxides from the literature data.

Butler, Matias; Cabrera, Gabriela M.

2013-07-01

414

Enzymatic synthesis and carbon-13 nuclear magnetic resonance conformational studies of disaccharides containing. beta. -D-galactopyranosyl and. beta. -D-(1-/sup 13/C)Galactopyranosyl residues  

SciTech Connect

Partially purified UDPgalactosyltransferase (EC 2.4.1.22) from bovine milk has been used to synthesize millimolar amounts of compounds such as Gal..beta..(1..-->..4)Glc, Gal..beta..(1..-->..4)GlcNAc-..beta..-hexanolamine, and Gal..beta..(1..-->..4)-GlcNAc..beta..(1..-->..4)GlcNAc. The same method has been used to prepare similar compounds containing /sup 13/C-enriched galactopyranosyl moieties. Gal..beta..(1..-->..4)GlcNAc-..beta..-hexanolamine was also synthesized in a solid-phase system in which the GlcNAc-..beta..-hexanolamine glycoside was covalently linked to agarose beads. At pH 7.0 and at 1 to 5 mM Mn/sup 2 + +/ the yields of the galactosyl saccharides are greater than 90% by using 10% excess of UDPGal donor. The use of a 90% enriched (1-/sup 13/C)galactosyl residue allowed the determination of the most abundant conformer about the galactopyranosyl-glycoside linkage by analysis of the carbon-carbon coupling constants from Cl to Gal to the C3', C4', and C5' of GlcNAc or Glc. 3 figures, 1 table.

Nunez, H.A.; Barker, R.

1980-02-05

415

Carbon-13 NMR studies of salt shock-induced carbohydrate turnover in the marine cyanobacterium Agmenellum quadruplicatum  

NASA Technical Reports Server (NTRS)

Carbon turnover in response to abrupt changes in salinity, including the mobilization of glycogen for use in osmoregulation was studied with pulse-chase strategies utilizing nuclear magnetic resonance (NMR)-silent and NMR-detectable 12C and 13C isotopes, respectively. Growth of Agmenellum quadruplicatum in 30%-enriched 13C bicarbonate provided sufficient NMR-detectability of intracellular organic osmoregulants for these studies. A comparison of NMR spectra of intact cells and their ethanol extracts showed that the intact cell data were suitable for quantitative work, and, when combined with ESR measurements of cell volumes, yielded intracellular glucosylglycerol concentrations without disrupting the cells. NMR pulse-chase experiments were used to show that 13C-enriched glycogen, which had previously been accumulated by the cells under nitrogen-limited growth at low salinities, could be utilized for the synthesis of glucosylglycerol when the cells were abruptly transferred to hypersaline media, but only in the light. It was also shown that the accumulation of glucosylglycerol in the light occurred on a time scale similar to that of cell doubling. Depletion of glucosylglycerol when cells abruptly transferred to lower salinities appeared to be rapid--the intracellular pool of this osmoregulant was decreased 2-fold within 2 hours of hypotonic shock.

Tel-Or, E.; Spath, S.; Packer, L.; Mehlhorn, R. J.

1986-01-01

416

Electron Spin Dynamics in Semiconductor Quantum Dots  

SciTech Connect

An electron spin confined to a semiconductor quantum dot is not subject to the classical spin relaxation mechanisms known for free carriers but it strongly interacts with the nuclear spin system via the hyperfine interaction. We show in time resolved photoluminescence spectroscopy experiments on ensembles of self assembled InAs quantum dots in GaAs that this interaction leads to strong electron spin dephasing.

Marie, X.; Belhadj, T.; Urbaszek, B.; Amand, T. [Universite de Toulouse, LPCNO, INSA-CNRS-UPS, 135 avenue de Rangueil, 31077 Toulouse (France); Krebs, O.; Lemaitre, A.; Voisin, P. [Laboratoire de Photonique et Nanostructures, route de Nozay, 91460 Marcoussis (France)

2011-07-15

417

Efficient Transformation of Parahydrogen Spin Order into Heteronuclear Magnetization  

PubMed Central

Spin order obtained in the strong coupling regime of protons from parahydrogen-induced hyperpolarization (PHIP) is initially captured as an ensemble of singlet states. For biomedical applications of PHIP, locking this spin order on long-lived heteronuclear storage nuclei increases spectral dispersion, reduces background interference from water protons, and eliminates the need to synchronize subsequent detection pulse sequences to accrued singlet-state evolution. A variety of traditional sequences such as INEPT or HMQC are available to interconvert heteronuclear single quantum coherences at high field, but new approaches are required for converting singlet states into heteronuclear single quantum coherences at low field in the strong coupling regime of protons. Described here is a consolidated pulse sequence that achieves this transformation of singlet-state spin order into heteronuclear magnetization across a wide range of scalar couplings in AA?X spin systems. Analytic solutions to the spin evolution are presented, and performance was validated experimentally in the parahydrogen addition product, 2-hydroxyethyl 1-13C-propionate-d3. Hyperpolarized carbon-13 signals were enhanced by a factor of several million relative to Boltzmann polarization in a static magnetic field of 47.5 mT (~13% polarization). We anticipate that this pulse sequence will provide efficient conversion of parahydrogen spin order over a broad range of emerging PHIP agents that feature AA?X spin systems. PMID:23214962

Cai, Chong; Coffey, Aaron M.; Shchepin, Roman V.; Chekmenev, Eduard Y.; Waddell, Kevin W.

2015-01-01

418

Magic angle spinning nuclear magnetic resonance characterization of voltage-dependent anion channel gating in two-dimensional lipid crystalline bilayers.  

PubMed

The N-terminus of the voltage-dependent anion channel (VDAC) has been proposed to contain the mechanistically important gating helices that modulate channel opening and closing. In this study, we utilize magic angle spinning nuclear magnetic resonance (MAS NMR) to determine the location and structure of the N-terminus for functional channels in lipid bilayers by measuring long-range (13)C-(13)C distances between residues in the N-terminus and other domains of VDAC reconstituted into DMPC lipid bilayers. Our structural studies show that the distance between A14 C? in the N-terminal helix and S193 C? is ?4-6 Å. Furthermore, VDAC phosphorylation by a mitochondrial kinase at residue S193 has been claimed to delay mitochondrial cell death by causing a conformational change that closes the channel, and a VDAC-Ser193Glu mutant has been reported to show properties very similar to those of phosphorylated VDAC in a cellular context. We expressed VDAC-S193E and reconstituted it into DMPC lipid bilayers. Two-dimensional (13)C-(13)C correlation experiments showed chemical shift perturbations for residues located in the N-terminus, indicating possible structural perturbations to that region. However, electrophysiological data recorded on VDAC-S193E showed that channel characteristics were identical to those of wild type samples, indicating that phosphorylation of S193 does not directly affect channel gating. The combination of NMR and electrophysiological results allows us to discuss the validity of proposed gating models. PMID:25545271

Eddy, Matthew T; Andreas, Loren; Teijido, Oscar; Su, Yongchao; Clark, Lindsay; Noskov, Sergei Y; Wagner, Gerhard; Rostovtseva, Tatiana K; Griffin, Robert G

2015-02-01

419

Analysis of metabolic characteristics in a rat model of chronic pancreatitis using high-resolution magic-angle spinning nuclear magnetic resonance spectroscopy  

PubMed Central

Pathological and metabolic alterations co-exist and co-develop in the progression of chronic pancreatitis (CP). The aim of the present study was to investigate the metabolic characteristics and disease severity of a rat model of CP in order to determine associations in the observed pathology and the metabolites of CP using high-resolution magic-angle spinning nuclear magnetic resonance spectroscopy (HR-MAS NMR). Wistar rats (n=36) were randomly assigned into 6 groups (n=6 per group). CP was established by administering dibutyltin dichloride solution into the tail vein. After 0, 7, 14, 21, 28 and 35 days, the pancreatic tissues were collected for pathological scoring or for HR-MAS NMR. Correlation analyses between the major pathological scores and the integral areas of the major metabolites were determined. The most representative metabolites, aspartate, betaine and fatty acids, were identified as possessing the greatest discriminatory significance. The Spearman’s rank correlation coefficients between the pathology and metabolites of the pancreatic tissues were as follows: Betaine and fibrosis, 0.454 (P=0.044); betaine and inflammatory cell infiltration, 0.716 (P=0.0001); aspartate and fibrosis, ?0.768 (P=0.0001); aspartate and inflammatory cell infiltration, ?0.394 (P=0.085); fatty acid and fibrosis, ?0.764 (P=0.0001); and fatty acid and inflammatory cell infiltration, ?0.619 (P=0.004). The metabolite betaine positively correlated with fibrosis and inflammatory cell infiltration in CP. In addition, aspartate negatively correlated with fibrosis, but exhibited no significant correlation with inflammatory cell infiltration. Furthermore, the presence of fatty acids negatively correlated with fibrosis and inflammatory cell infiltration in CP. HR-MAS NMR may be used to analyze metabolic characteristics in a rat model of different degrees of chronic pancreatitis. PMID:25338744

TIAN, BING; MA, CHAO; WANG, JIAN; PAN, CHUN-SHU; YANG, GEN-JIN; LU, JIAN-PING

2015-01-01

420

Solid State CARBON-13 NMR and Thermal Analysis of Conformational Motion and Disorder in Small and Large Molecules  

NASA Astrophysics Data System (ADS)

In this work it is attempted to explore the conformational motion and disorder through a large number of examples of molecular systems differing in shape, rigidity, and molecular weight: a series of tetra-n-alkylammonium bromides and iodides, a liquid-crystal-forming molecule, N,N ^'-bis(4-n-octyloxybenzal)-1,4 -phenylenediamine (OOBPD), and polymers, poly (oxy-1,4-(3 -methylphenylene)ethylene-1,4-phenyleneoxy-nonamethylene ] (MBPE-9) and poly (oxy-1,4 -(3-methylphenylene)ethylene-1,4-phenyleneoxypentamethylene ] (MBPE-5). The techniques used to study the conformational motion and disorder are mainly solid state ^{13}C nuclear magnetic resonance (NMR) spectroscopy and thermal analysis. The results of this work show that conformational disordered states (condis crystals) exist indeed in these molecules containing flexible chemical bonds (single bonds) or more than one accessible conformer. The unique characteristics of the condis crystal and the phase transitions to a condis crystal and to isotropic state have been studied in detail. It could be shown that motifs in condis crystals show only conformational disorder but maintaining orientational and positional order, while liquid and plastic crystals show conformational motion in addition to their characteristic positional and orientational disorder and motion, respectively. The molecular motion in the condis state is slow compared to well-known plastic and liquid crystals. Besides the large -amplitude motion in a first-order transition, it is documented that gradual start of motion is possible increasing the conformational entropy over a broad temperature range.

Cheng, Jinlong

421

Initialization and readout of spin chains for quantum information transport  

Microsoft Academic Search

Linear chains of spins acting as quantum wires are a promising approach for achieving scalable quantum information processors. Nuclear spins in apatite crystals provide an ideal test bed for the experimental study of quantum information transport, as they closely emulate a one-dimensional spin chain, while magnetic resonance techniques can be used to drive the spin chain dynamics and probe the

Gurneet Kaur; Paola Cappellaro

2012-01-01

422

Multifrequency spin resonance in diamond  

SciTech Connect

Magnetic resonance techniques provide a powerful tool for controlling spin systems, with applications ranging from quantum information processing to medical imaging. Nevertheless, the behavior of a spin system under strong excitation remains a rich dynamical problem. In this paper, we examine spin resonance of the nitrogen-vacancy center in diamond under conditions outside the regime where the usual rotating-wave approximation applies, focusing on effects of multifrequency excitation and excitation with orientation parallel to the spin quantization axis. Strong-field phenomena such as multiphoton transitions and coherent destruction of tunneling are observed in the spectra and analyzed via numerical and analytic theory. In addition to illustrating the response of a spin system to strong multifrequency excitation, these observations may inform techniques for manipulating electron-nuclear spin quantum registers.

Childress, Lilian; McIntyre, Jean [Department of Physics and Astronomy, Bates College, 44 Campus Ave, Lewiston, Maine 04240 (United States)

2010-09-15

423

Quantitative Determination of Chemical Processes by Dynamic Nuclear Polarization Enhanced Nuclear Magnetic Resonance Spectroscopy  

E-print Network

Dissolution dynamic nuclear polarization (DNP) provides several orders of magnitude of NMR signal enhancement by converting the much larger electron spin polarization to nuclear spin polarization. Polarization occurs at low temperature (1.4K...

Zeng, Haifeng

2012-07-16

424

Conformation and Orientation of Gramicidin a in Oriented Phospholipid Bilayers Measured by Solid State Carbon-13 NMR  

PubMed Central

Three analogues of the helical ionophore gramicidin A have been synthesized with 13C-labeled carbonyls (13C=O) incorporated at either Gly2, Ala3, or Val7. A fourth compound incorporated 13C at both the carbonyl and ?-carbon of Gly2 within the same molecule. These labels were studied using solid-state, proton-enhanced, 13C nuclear magnetic resonance (NMR) in hydrated dispersions of dimyristoylphosphatidylcholine (DMPC)-gramicidin A. The dispersions were aligned on glass coverslips whose orientation to the magnetic field could be varied through 180°. The orientation dependence of the NMR spectrum was used to obtain an accurate measurement of the 13C chemical shift anisotropy (CSA), and in the case of the fourth compound, the 13C—13C dipolar coupling constant. From the measured CSA and estimates of the orientation of the 13C shielding tensor, we are able to determine the direction of the 13C=O bonds and to compare these with the predictions of the various reported models for the configuration of gramicidin A in phospholipid bilayers. Our results are consistent with the left-handed ??6.3LD single-stranded helix (Urry, D. W., J. T. Walker, and T. L. Trapane. 1982. J. Membr. Biol. 69:225-231). The right-handed ??6.3LD single-stranded helix observed for gramicidin A in sodium dodecyl sulfate micelles (Arseniev, A. S., I. L. Barsukov, V. F. Bystrov, A. L. Loize, and Yu A. Ovchinnikov. 1985. FEBS (Fed. Eur. Biochem. Soc.) Lett. 186:168-174) yields a poorer fit to the data. However, the width of the carbonyl resonances suggests a distribution of molecular geometries possibly resulting from a spread in the helix pitch and handedness. Double-stranded helices and ? sheet structures are excluded. In dispersions in which the lipid is in the L? phase, the gramicidin A undergoes rapid reorientation about an axis which is centered on the normal to the plane of the coverslips. When the supporting lipid is in the L?? phase the helices are rigid on the timescale of 13C-NMR. The configuration of gramicidin A is unaltered by L?-L?? phase transition of the bilayer lipid. PMID:19431717

Cornell, Bruce A.; Separovic, Frances; Baldassi, Attilio J.; Smith, Ross

1988-01-01

425

Long time evolution of a spin interacting with a spin bath in arbitrary magnetic field  

NASA Astrophysics Data System (ADS)

We introduce a completely different method to calculate the evolution of a spin interacting with a sufficient large spin bath, especially suitable for treating the central spin model in a quantum dot (QD). With only an approximation on the envelope of central spin, the symmetry can be exploited to reduce a huge Hilbert space which cannot be calculated with computers to many small ones which can be solved exactly. This method can be used to calculate spin-bath evolution for a spin bath containing many (say, 1000) spins, without a perturbative limit such as strong magnetic field condition, and works for long-time regime with sufficient accuracy. As the spin-bath evolution can be calculated for a wide range of time and magnetic field, an optimal dynamic of spin flip-flop can be found, and more sophisticated approaches to achieve extremely high polarization of nuclear spins in a QD could be developed.

Zhao, YuKang; Zhao, MeiSheng; Chen, ZengBing

2014-07-01

426

Initialization and readout of spin chains for quantum information transport  

E-print Network

Linear chains of spins acting as quantum wires are a promising approach for achieving scalable quantum information processors. Nuclear spins in apatite crystals provide an ideal test bed for the experimental study of quantum ...

Kaur, Gurneet

427

Limits on Anomalous Spin-Spin Couplings between Neutrons  

SciTech Connect

We report experimental limits on new spin-dependent macroscopic forces between neutrons. We measured the nuclear Zeeman frequencies of a {sup 3}He/{sup 129}Xe maser while modulating the nuclear spin polarization of a nearby {sup 3}He ensemble in a separate glass cell. We place limits on the coupling strength of neutron spin-spin interactions mediated by light pseudoscalar particles like the axion [g{sub p}g{sub p}/(4{pi}({Dirac_h}/2{pi})c)] at the 3x10{sup -7} level for interaction ranges longer than about 40 cm. This limit is about 10{sup -5} the size of the magnetic dipole-dipole interaction between neutrons.

Glenday, Alexander G.; Walsworth, Ronald L. [Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States); Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); Cramer, Claire E.; Phillips, David F. [Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States)

2008-12-31

428

High-resolution mono- and multidimensional magic angle spinning 1H nuclear magnetic resonance of membrane peptides in nondeuterated lipid membranes and H2O.  

PubMed Central

High-speed (14 kHz) solid-state magic angle spinning (MAS) 1H NMR has been applied to several membrane peptides incorporated into nondeuterated dilauroyl or dimyristoylphosphatidylcholine membranes suspended in H2O. It is shown that solvent suppression methods derived from solution NMR, such as presaturation or jump-return, can be used to reduce water resonance, even at relatively high water content. In addition, regioselective excitation of 1H peptide resonances promotes an efficient suppression of lipid resonances, even in cases where these are initially two orders of magnitude more intense. As a consequence, 1H MAS spectra of the peptide low-field region are obtained without interference from water and lipid signals. These display resonances from amide and other exchangeable 1H as well as from aromatic nonexchangeable 1H. The spectral resolution depends on the specific types of resonance and membrane peptide. For small amphiphilic or hydrophobic oligopeptides, resolution of most individual amide resonance is achieved, whereas for the transmembrane peptide gramicidin A, an unresolved amide spectrum is obtained. Partial resolution of aromatic 1H occurs in all cases. Multidimensional 1H-MAS spectra of membrane peptides can also be obtained by using water suppression and regioselective excitation. For gramicidin A, F2-regioselective 2D nuclear Overhauser effect spectroscopy (NOESY) spectra are dominated by intermolecular through-space connectivities between peptide aromatic or formyl 1H and lipid 1H. These appear to be compatible with the known structure and topography of the gramicidin pore. On the other hand, for the amphiphilic peptide leucine-enkephalin, F2-regioselective NOESY spectra mostly display cross-peaks originating from though-space proximities of amide or aromatic 1H with themselves and with aliphatic 1H. F3-regioselective 3D NOESY-NOESY spectra can be used to obtain through-space correlations within aliphatic 1H. Such intrapeptide proximities should allow determination of the conformation of the peptide in membranes. It is suggested that high-speed MAS multidimensional 1H NMR of peptides in nondeuterated membranes and in H2O can be used for studies of both peptide structure and lipid-peptide interactions. Images FIGURE 8 PMID:8913601

Le Guernevé, C; Seigneuret, M

1996-01-01

429

Quantum measurement of a mesoscopic spin ensemble  

SciTech Connect

We describe a method for precise estimation of the polarization of a mesoscopic spin ensemble by using its coupling to a single two-level system. Our approach requires a minimal number of measurements on the two-level system for a given measurement precision. We consider the application of this method to the case of nuclear-spin ensemble defined by a single electron-charged quantum dot: we show that decreasing the electron spin dephasing due to nuclei and increasing the fidelity of nuclear-spin-based quantum memory could be within the reach of present day experiments.

Giedke, G. [Institut fuer Quantenelektronik, ETH Zuerich, Wolfgang-Pauli-Strasse 16, 8093 Zurich (Switzerland); Max-Planck-Institut fuer Quantenoptik, H.-Kopfermann-Str., 85748 Garching (Germany); Taylor, J. M.; Lukin, M. D. [Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); D'Alessandro, D. [Department of Mathematics, Iowa State University, Ames, Iowa 50011 (United States); Imamoglu, A. [Institut fuer Quantenelektronik, ETH Zuerich, Wolfgang-Pauli-Strasse 16, 8093 Zurich (Switzerland)

2006-09-15

430

Coherence of Donor Electron Spins in Isotopically Enriched Silicon  

NASA Astrophysics Data System (ADS)

Silicon is promising for spin-based quantum computing because nuclear spins, a source of magnetic noise, may be nearly eliminated through enrichment. However, any Si device is expected to contain some phosphorus donor impurities. These donors generate magnetic noise through spin dynamics, induced by dipolar interactions, that conserve Zeeman and hyperfine energies. Ironically, increasing the number of nuclear spins will suppress this decoherence mechanism by effecting more hyperfine energy variation (i.e., Overhauser shifts). We study spin coherence decay as a function of donor concentration, ^29Si concentration, and temperature using cluster expansion techniques specifically adapted to the problem of a sparse electron spin bath.

Witzel, Wayne; Muller, Richard; Carroll, Malcolm; Morello, Andrea; Cywinski, Lukasz; Das Sarma, Sankar

2010-03-01

431

Protecting a Solid-State Spin from Decoherence Using Dressed Spin States  

NASA Astrophysics Data System (ADS)

We report experimental studies of dressing an electron spin in diamond with resonant and continuous microwave fields to protect the electron spin from magnetic fluctuations induced by the nuclear spin bath. We use optical coherent population trapping (CPT) to probe the energy level structure, optically induced spin transitions, and spin decoherence rates of the dressed spin states. Dressing an electron spin with resonant microwaves at a coupling rate near 1 MHz leads to a 50 times reduction in the linewidth of the spin transition underlying the CPT process, limited by transit-time broadening. Compared with dynamical decoupling, where effects of the bath are averaged out at specific times, the dressed spin state provides a continuous protection from decoherence.

Golter, D. Andrew; Baldwin, Thomas K.; Wang, Hailin

2014-12-01

432

Spin dynamics simulation of electron spin relaxation in Ni2 +(aq)  

NASA Astrophysics Data System (ADS)

The ability to quantitatively predict and analyze the rate of electron spin relaxation of open-shell systems is important for electron paramagnetic resonance and paramagnetic nuclear magnetic resonance spectroscopies. We present a combined molecular dynamics (MD), quantum chemistry (QC), and spin dynamics simulation method for calculating such spin relaxation rates. The method is based on the sampling of a MD trajectory by QC calculations, to produce instantaneous parameters of the spin Hamiltonian used, in turn, to numerically solve the Liouville-von Neumann equation for the time evolution of the spin density matrix. We demonstrate the approach by simulating the relaxation of electron spin in an aqueous solution of Ni2 + ion. The spin-lattice (T1) and spin-spin (T2) relaxation rates are extracted directly from the simulations of the time dependence of the longitudinal and transverse magnetization, respectively. Good agreement with the available, indirectly obtained experimental data is obtained by our method.

Rantaharju, Jyrki; Mareš, Ji?í; Vaara, Juha

2014-07-01

433