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1

Protein carbon-13 spin systems by a single two-dimensional nuclear magnetic resonance experiment  

SciTech Connect

By applying a two-dimensional double-quantum carbon-13 nuclear magnetic resonance experiment to a protein uniformly enriched to 26% carbon-13, networks of directly bonded carbon atoms were identified by virtue of their one-bond spin-spin couplings and were classified by amino acid type according to their particular single- and double-quantum chemical shift patterns. Spin systems of 75 of the 98 amino acid residues in a protein, oxidized Anabaena 7120 ferredoxin (molecular weight 11,000), were identified by this approach, which represents a key step in an improved methodology for assigning protein nuclear magnetic resonance spectra. Missing spin systems corresponded primarily to residues located adjacent to the paramagnetic iron-sulfur cluster. 25 references, 2 figures.

Oh, B.H.; Westler, W.M.; Darba, P.; Markley, J.L.

1988-05-13

2

Chemical and carbon-13 cross-polarization magic-angle spinning nuclear magnetic resonance characterization of logyard fines from British Columbia.  

PubMed

Phasing out beehive burners and rising costs for landfilling have increased the need to widen options for utilization of the smaller size fractions of woody wastes generated during log handling and sawmilling in British Columbia. We characterized several size classes of logyard fines up to 16 mm sampled from coastal and interior operations. Total C, total N, ash, and condensed tannin concentrations were consistent with properties derived largely from wood, with varying proportions of bark and mixing with mineral soil. Especially for < 3-mm fractions, the latter resulted in high ash contents that would make them unsuitable for fuel. Solid-state 13C cross-polarization magic-angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectra were consistent with the chemical data, with high O-alkyl intensity and similarity to naturally occurring woody forest floor; no samples were high in aromatic or phenolic C. Aqueous extracts of two < 16-mm fines, which accounted for only a small proportion of the total C, were enriched in alkyl C and had low or undetectable tannins. Application to forest sites might cause short-term immobilization of N, but also might include possible longer-term benefits from reduction of N loss after harvesting and restoration of soil organic matter in degraded sites. PMID:15074831

Preston, C M; Forrester, P D

2004-01-01

3

Characterization of high-tannin fractions from humus by carbon-13 cross-polarization and magic-angle spinning nuclear magnetic resonance.  

PubMed

Condensed tannins can be found in various parts of many plants. Unlike lignin there has been little study of their fate as they enter the soil organic matter pool and their influence on nutrient cycling, especially through their protein-binding properties. We extracted and characterized tannin-rich fractions from humus collected in 1998 from a black spruce [Picea mariana (Mill.) Britton et al.] forest in Canada where a previous study (1995) showed high levels (3.8% by weight) of condensed tannins. A reference tannin purified from black spruce needles was characterized by solution 13C nuclear magnetic resonance (NMR) as a pure procyanidin with mainly cis stereochemistry and an average chain length of four to five units. The colorimetric proanthocyanidin (PA) assay, standardized against the black spruce tannin, showed that both extracted humus fractions had higher tannin contents than the original humus (2.84% and 11.17% vs. 0.08%), and accounted for 32% of humus tannin content. Consistent with the results from the chemical assay, the aqueous fraction showed higher tannin signals in the 13C cross-polarization and magic-angle spinning (CPMAS) NMR spectrum than the emulsified one. As both tannin-rich humus fractions were depleted in N and high in structures derived from lignin and cutin, they did not have properties consistent with recaldtrant tannin-protein complexes proposed as a mechanism for N sequestration in humus. Further studies are needed to establish if tannin-protein structures in humus can be detected or isolated, or if tannins contribute to forest management problems observed in these ecosystems by binding to and slowing down the activity of soil enzymes. PMID:11931430

Lorenz, Klaus; Preston, Caroline M

2002-01-01

4

Natural-Abundance Carbon13 FourierTransform Nuclear Magnetic Resonance Spectra and Spin Lattice Relaxation Times of Unfractionated Yeast Transfer-RNA  

Microsoft Academic Search

High-resolution Fourier-transform nuclear magnetic resonance at 15.18 MHz was used to observe the proton-decoupled natural-abundance 13C spectra of aqueous unfractionated tRNA from baker's yeast in the presence of Mg+2 (8 ions per tRNA molecule), as a function of temperature in the range of 27-82 degrees C. The spectrum of thermally denatured tRNA at 82 degrees C showed numerous sharp resonances,

Richard A. Komoroski; Adam Allerhand

1972-01-01

5

Interactions of long-chain aldehydes with luciferase. A carbon-13 nuclear magnetic resonance study.  

PubMed

The interaction of long-chain aldehydes with bacterial luciferase has been studied by 13C NMR spectroscopy of natural-abundance and 13C-enriched 1-dodecanal. At high substrate/enzyme ratios, the spin-spin relaxation rates of C(1)-C(3) are faster than for the other carbons and are in the order C(1) greater than C(2) greater than C(3). The aldehyde is strongly bound in the active site along the entire length of the alkyl chain with the strongest interaction at the CHO group. At low substrate/enzyme ratios, interactions are apparent at C(10), which are removed upon denaturation of the enzyme. Spin-spin and spin-lattice relaxation rates were measured for odd-carbon 13C-enriched 1-dodecanal in the presence of luciferase. From the ratios of T1/T2 a single value of (1.8 +/- 0.7) X 10(-8) s was calculated for the rotational correlation time tc for the complex. PMID:444472

Viswanathan, T S; Campling, M R; Cushley, R J

1979-06-12

6

Quantitative carbon-13 nuclear magnetic resonance spectroscopic study of mobile residues in bacteriorhodopsin  

SciTech Connect

The authors have used quantitative carbon-13 nuclear magnetic resonance (NMR) spectroscopy to study the dynamic structure of the backbone of bacteriorhodopsin in the purple membrane of Halobacterium halobium R/sub 1/ and JW-3. NMR experiments were performed using an internal sucrose quantitation standard on purple membranes in which one of the following /sup 13/C'-labeled amino acids had been biosynthetically incorporated: glycine, isoleucine, lysine, phenylalanine, and valine. The results suggest that the C-terminus of the polypeptide chain backbone, and possibly one of the connecting loops, undergoes rapid, large angle fluctuations. The results are compared with previous NMR and fluorescence spectroscopic data obtained on bacteriorhodopsin.

Bowers, J.L.; Oldfield, E.

1988-07-12

7

Substituent Effects. Vii. Carbon-13 Nuclear Magnetic Resonance of Substituted Cyclopropanes.  

National Technical Information Service (NTIS)

Carbon-13 chemical shifts and directly bonded carbon-hydrogen coupling constants are reported for a series of cyclopropyl compounds. The chemical shifts of the alpha-carbon atoms show a linear correlation with similarly substituted methanes. Carbon-13 shi...

P. H. Weiner E. R. Malinowski

1967-01-01

8

Nuclear spin circular dichroism  

NASA Astrophysics Data System (ADS)

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

2014-04-01

9

Nuclear spin circular dichroism.  

PubMed

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. PMID:24712776

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

2014-04-01

10

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...

11

Carbon-13 nuclear magnetic resonance identification of 2-hydroxy-3-O-methyl-6beta-naltrexol as a minor naltrexone metabolite.  

PubMed

A carbon-13 nuclear magnetic resonance comparison of synthetic and biological samples was used to identify unequivocally 2-hydroxy-3-O-methyl-6beta-naltrexol as a minor naltrexone metabolite in humans. This study points up the increasing usefulness of natural abundance carbon-13 nuclear magnetic resonance techniques in metabolism studies. PMID:734225

Brine, G A; Brine, D R; Welch, C D; Bondeson, V C; Carroll, F I

1978-12-01

12

Characterization of the International Humic Substances Society standard and reference fulvic and humic acids by solution state carbon-13 (13C) and hydrogen-1 (1H) nuclear magnetic resonance spectrometry  

USGS Publications Warehouse

Standard and reference samples of the International Humic Substances Society have been characterized by solution state carbon-13 and hydrogen-1 nuclear magnetic resonance (NMR) spectrometry. Samples included the Suwannee River, soil, and peat standard fulvic and humic acids, the Leonardite standard humic acid, the Nordic aquatic reference fulvic and humic acids, and the Summit Hill soil reference humic acid. Aqueous-solution carbon-13 NMR analyses included the measurement of spin-lattice relaxation times, measurement of nuclear Overhauser enhancement factors, measurement of quantitative carbon distributions, recording of attached proton test spectra, and recording of spectra under nonquantitative conditions. Distortionless enhancement by polarization transfer carbon-13 NMR spectra also were recorded on the Suwannee River fulvic acid in deuterated dimethyl sulfoxide. Hydrogen-1 NMR spectra were recorded on sodium salts of the samples in deuterium oxide. The carbon aromaticities of the samples ranged from 0.24 for the Suwannee River fulvic acid to 0.58 for the Leonardite humic acid.

Thorn, Kevin A.; Folan, Daniel W.; MacCarthy, Patrick

1989-01-01

13

Carbon-13 nuclear magnetic resonance studies of a solid inclusion complex  

SciTech Connect

A solid inclusion complex containing n-hexane as the mobile guest component was studied via cross polarization nuclear magnetic resonance techniques. The hexane is found to yield a cross polarization spectrum, demonstrating that its motion in the lattice is anisotropic. The hexane also yields a relatively sharp spectrum with the proton decoupler off, showing reduced /sup 1/H-/sup 13/C scalar splittings. A theory developed by Sack and Pople to account for the effect of /sup 14/N relaxation on the appearance of the /sup 1/H spectrum of NH/sub 3/ is applied here to account for the reduced splitting in terms of a proton-proton flip-flop mechanism. A flip-flop rate of 110-135 s/sup -1/ is determined for the methylene groups. The /sup 13/C spin-spin relaxation time is used in a rough characterization of rotational motion of the hexane. The qualitative correlation time obtained is intermediate between that for a liquid and that for a rigid solid. 7 figures.

Early, T.A. (Colorado State Univ., Fort Collins); Haw, J.F.; Bax, A.; Maciel, G.E.; Puar, M.S.

1984-01-19

14

Characterization of sewage sludge organic matter using solid-state carbon-13 nuclear magnetic resonance spectroscopy.  

PubMed

Six sewage sludges from five sewage treatment plants in Australia were characterized using solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Spectra were acquired both before and after removal of mineral components through treatment with hydrofluoric acid (HF). Carbon mass balance indicated that little organic matter was lost on HF treatment, which significantly improved NMR sensitivity and spectral resolution, and decreased acquisition time and hence cost of NMR analysis. Two NMR techniques were used, the standard cross polarization (CP) technique and Bloch decay (BD). The BD technique had not been applied previously to the analysis of sewage sludge. For each sludge sample, both before and after HF treatment, the BD spectrum contained significantly more alkyl carbon. Spin counting, another technique applied to sewage sludge here for the first time, showed that the BD spectra of the HF-treated sludges were quantitative, while approximately 30% of the CP NMR signal went undetected. The discrepancy between CP and BD spectra was attributed to the presence of alkyl carbon with such high molecular mobility that the efficiency of cross polarization is affected. This study shows that sewage sludge organic matter is significantly different in chemistry to soil organic matter and has implications for the application of sewage sludge to agricultural land. PMID:12931909

Smernik, Ronald J; Oliver, Ian W; Merrington, Graham

2003-01-01

15

Carbon-13 nuclear magnetic resonance spectra of potassium (ethylenediaminetetraacetato)cobaltate(III) in organic solvents  

SciTech Connect

The carbon-13 NMR spectra of the (Co(edta))/sup /minus// (edta = ethylenediaminetetraacetate) anion were observed in water and a variety of organic solvents: ethylene glycol, methanol, formamide, ethanol, 2-propanol, chloroform, dichloromethane, dimethyl sulfoxide, acetonitrile, dimethylformamide, benzonitrile, and dimethylacetamide. The spectra in organic solvents were obtained after 1-2-h accumulations for the concentrated solutions (0.5 M) of the complex anion that were prepared by the addition of a macrobicyclic polyether, cryptand 222, to the solvents. The /sup 13/C NMR signals of the coordinated carboxylates are markedly shifted downfield in protic solvents in comparison with aprotic solvent (the greatest difference in chemical shift is 3.9 ppm), while the NMR chemical shifts of methylene carbons of ligands are not significantly influenced by solvent molecules. The magnitudes (/sigma/ values) of this downfield shift of the coordinated carboxylate /sup 13/C signals are found to be correlated linearly with the electrophilic ability of the solvent molecules. This finding leads to the conclusion that the (Co(edta))/sup /minus// anion interacts with solvent molecules through the hydrogen-bonding between solvent hydrogens and carboxyl oxygens of the complex anion. 10 references, 4 figures, 1 table.

Taura, Toshiaki

1988-08-10

16

Solid-State Carbon13 Nuclear Magnetic Resonance of Humic Acids at High Magnetic Field Strengths  

Microsoft Academic Search

13 C NMR spectra of humic acids at high magnetic width of the chemical shift anisotropy (CSA) at this low field and spinning frequency. We examine the cross polarization (CP) magnetic field strength. dynamics under both traditional and ramp CP conditions on Cedar Creek humic acid. Fitted equilibrium intensities from these CP dy- Since the establishment of these conditions for

Karl J. Dria; Joseph R. Sachleben; Patrick G. Hatcher

2002-01-01

17

A carbon-13 and proton nuclear magnetic resonance study of some experimental referee broadened-specification /ERBS/ turbine fuels  

NASA Technical Reports Server (NTRS)

Preliminary results of a nuclear magnetic resonance (NMR) spectroscopy study of alternative jet fuels are presented. A referee broadened-specification (ERBS) aviation turbine fuel, a mixture of 65 percent traditional kerosene with 35 percent hydrotreated catalytic gas oil (HCGO) containing 12.8 percent hydrogen, and fuels of lower hydrogen content created by blending the latter with a mixture of HCGO and xylene bottoms were studied. The various samples were examined by carbon-13 and proton NMR at high field strength, and the resulting spectra are shown. In the proton spectrum of the 12.8 percent hydrogen fuel, no prominent single species is seen while for the blending stock, many individual lines are apparent. The ERBS fuels were fractionated by high-performance liquid chromatography and the resulting fractions analyzed by NMR. The species found are identified.

Dalling, D. K.; Pugmire, R. J.

1982-01-01

18

Characteristic spectral patterns in the carbon-13 nuclear magnetic resonance spectra of hexagonal and crenellated graphene fragments.  

PubMed

Nuclear magnetic resonance (NMR) spectroscopy is an important molecular characterisation method that may aid the synthesis and production of graphenes, especially the molecular-scale graphene nanoislands that have gathered significant attention due to their potential electronic and optical applications. Herein, carbon-13 NMR chemical shifts were calculated using density functional theory methods for finite, increasing-size fragments of graphene, hydrogenated graphene (graphane) and fluorinated graphene (fluorographene). Both concentric hexagon-shaped (zigzag boundary) and crenellated (armchair) fragments were investigated to gain information on the effect of different types of flake boundaries. Convergence trends of the (13) C chemical shift with respect to increasing fragment size and the boundary effects were found and rationalised in terms of low-lying electronically excited states. The results predict characteristic behaviour in the (13) C NMR spectra. Particular attention was paid to the features of the signals arising from the central carbon atoms of the fragments, for graphene and crenellated graphene on the one hand and graphane and fluorographene on the other hand, to aid the interpretation of the overall spectral characteristics. In graphene, the central nuclei become more shielded as the system size increases whereas the opposite behaviour is observed for graphane and fluorographene. The (13) C signals from some of the perimeter nuclei of the crenellated fragments obtain smaller and larger chemical shift values than central nuclei for graphene and graphane/fluorographene, respectively. The diameter of the graphenic quantum dots with zigzag boundary correlates well with the predicted carbon-13 chemical shift range, thus enabling estimation of the size of the system by NMR spectroscopy. The results provide data of predictive quality for future NMR analysis of the graphene nanoflake materials. PMID:24807480

Ozcan, Nergiz; Vähäkangas, Jarkko; Lantto, Perttu; Vaara, Juha

2014-06-23

19

Nonheuristic Computer Determination of Molecular Structure Based Upon Carbon-13 Nuclear Magnetic Resonance Data. Branched Alkanes  

PubMed Central

A computer-based system for elucidation of molecular structure is described for the branched alkanes, based upon 13C nuclear magnetic resonance data. All possible structures of a given carbon content are exhaustively generated in a DENDRAL-like manner, and scored according to the fit of their predicted spectral characteristics to those of the “unknown” alkane. The technique may be generalized to any class of organic compounds for which 13C chemical-shift additivity parameters are reliable, and shows promise for stereochemical elucidation.

Burlingame, A. L.; Mcpherron, R. V.; Wilson, D. M.

1973-01-01

20

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, Jr. , L. B.; Thorn, K. A.

1987-01-01

21

Characterization of Substituted Phenol-Formaldehyde Resins Using Solid-State Carbon-13 NMR (Nuclear Magnetic Resonance).  

National Technical Information Service (NTIS)

Crosslinked substituted phenol-formaldehyde resins were synthesized from cashew nut shell liquid, 3-n-pentadecylphenol and phenol with formaldehyde. The resulting resins were crosslinked and then investigated using carbon-13 NMR in the solid state using c...

B. R. Sinha D. O'Connor F. D. Blum

1988-01-01

22

Characterization of Substituted Phenol-Formaldehyde Resins Using Solid-State Carbon-13 NMR (Nuclear Magnetic Resonance).  

National Technical Information Service (NTIS)

Crosslinked substituted phenol formaldehyde resins were synthesized from cashew nut shell liquid, 3-n-pentadecylphenol and phenol with formaldehyde. The resulting resins were crosslinked and then investigated using carbon-13 NMR in the solid state using c...

B. R. Sinha D. O'Connor F. D. Blum

1989-01-01

23

A carbon-13 NMR spin-lattice relaxation study of the molecular conformation of the nootropic drug 2-oxopyrrolidin-1-ylacetamide  

NASA Astrophysics Data System (ADS)

The spin-lattice relaxation times ( T1) of carbon-13 resonances of the drug 2-oxopyrrolidin- 1-ylacetamide ( 2OPYAC) were determined in CDCl 3 + DMSO and H 2O solutions to investigate the internal conformational flexibility. The measured T1s for the hydrogen-bearing carbon atoms of the 2-pyrrolidone ring fragment were diagnostic of a rigid conformation with respect to the acetamide linked moiety. The model of anisotropic reorientation of a rigid body was used to analyse the measured relaxation data in terms of a single conformation. Owing to the small number of T1 data available the fitting procedure for each of the possible conformations failed. The structure corresponding to the rigid conformation was therefore considered to be the one that is strongly stabilized by internal hydrogen bonding as predicted on the basis of theoretical MO ab initio quantum chemical calculations.

Baldo, M.; Grassi, A.; Guidoni, L.; Nicolini, M.; Pappalardo, G. C.; Viti, V.

24

Carbon-13 nuclear magnetic resonance spectroscopy of lipids: Differential line broadening due to cross-correlation effects as a probe of membrane structure  

SciTech Connect

The authors have obtained proton-coupled carbon-13 nuclear magnetic resonance (NMR) spectra of a variety of lipid-water and lipid-drug-water systems, at 11.7 T, as a function of temperature, using the 'magic-angle' sample-spinning (MAS) NMR technique. The resulting spectra show a wide range of line shapes, due to interferences between dipole-dipole and dipole-chemical shielding anisotropy interactions. The differential line-broadening effects observed are particularly large for aromatic and olefinic (sp{sup 2}) carbon atom sites. Coupled spectra of the tricyclic antidepressants desipramine and imipramine, in 1,2-dimyristoyl-sn-glycero-3-phosphocholine-water mesophases, show well-resolved doublets having different line shapes for each of the four aromatic methine groups, due to selective averaging of the four C-H dipolar interactions due to rapid motion about the director (or drug C{sub 2}) axis. {sup 2}H NMR spectra of (2,4,6,8-{sup 2}H{sub 4})desipramine (and imipramine) in the same 1,2-dimyristoyl-sn-glycero-3-phosphocholine-water mesophase exhibit quadrupole splittings of {approximately}0-2 and {approximately}20 kHz, indicating an approximate magic-angle orientation of the C2-{sup 2}H({sup 1}H) and C8-{sup 2}H({sup 1}H) vectors with respect to an axis of motional averaging, in accord with the {sup 13}C NMR results. The good qualitative agreement between {sup 13}C and {sup 2}H NMR results suggests that useful orientational ({sup 2}H NMR like) information can be deduced from natural-abundance {sup 13}C NMR spectra of a variety of mobile solids.

Oldfield, E.; Adebodun, F.; Chung, J.; Montez, B.; Ki Deok Park; Hongbiao Le; Phillips, B. (Univ. of Illinois, Urbana (United States))

1991-11-19

25

Application of solid state silicone-29 and carbon-13 nuclear magnetic resonance spectroscopy to the characterization of inorganic matter-humic complexes in Athabasca oil sands  

SciTech Connect

The ease of bitumen recovery from oil sand by hot or cold water separation techniques depends upon the surface properties of the components, especially water wet character of the clay and sand particles. Oil wetting of some of the oils and sand solids is believed to be caused by the presence of humic matter-non-crystalline inorganic complexes. Characterization of these complexes using solid state carbon-13 and silicon-29 magic spinning angle (MAS) NMR spectroscopy was the purpose of the present work.

Kotlyar, L.S.; Ripmeester, J.A.

1988-06-01

26

Characterization of the International Humic Substances Society Standard and Reference Fulvic and Humic Acids by Solution State Carbon-13 (13C) and Hydrogen-1 (1H) Nuclear Magnetic Resonance Spectrometry.  

National Technical Information Service (NTIS)

Standard and reference samples of the International Humic Substances Society have been characterized by solution state carbon-13 and hydrogen-1 nuclear magnetic resonance (NMR) spectrometry. Samples included the Suwannee River, soil, and peat standard ful...

K. A. Thorn D. W. Folan P. MacCarthy

1989-01-01

27

Characterization of isotopically labeled coal liquefaction solvents and products by deuterium and carbon-13 nuclear magnetic resonance spectrometry  

SciTech Connect

Primary and secondary deuterium isotope shifts are observed in the carbon-13 NMR spectrum of partially deuterated tetralin and naphthalene. These shifts are used to quantitate the extent of deuteration at each carbon site. Deuterium exchange at the tetralin ..cap alpha.. position is faster than coal liquefaction. A deuterium NMR method, using the natural abundance signal of the solvent as an internal standard, shows not only the relative distribution of deuterium in coal liquid products produced from deuterated tetralin as the donor solvent but also the absolute amount of deuterium in nonvolatile products. Some carbon-carbon coupling constants are reported for (1-/sup 13/C)tetralin, (1-/sup 13/C)octahydrophenathrene, and (4-/sup 13/C)-2,6-dimethyltetralin. The carbon-13 compounds verify that thermal ring opening is a negligible process under coal liquefaction conditions unless a catalyst is present. Ring contraction remains constant at about 5% of the thermal products with or without a catalyst. Deuterium NMR is used to follow the deuterium exchange between partially deuterated tetralin and mestylene. The deuterium label goes to the mesitylene methyls as expected. 13 references, 8 figures, 6 tables.

Young, D.C.; McNeil, R.I.; Cronauer, D.C.; Ruberto, R.G.; Galya, L.G.

1984-03-01

28

Carbon-13 and proton nuclear magnetic resonance analysis of shale-derived refinery products and jet fuels and of experimental referee broadened-specification jet fuels  

NASA Technical Reports Server (NTRS)

A proton and carbon-13 nuclear magnetic resonance (NMR) study was conducted of Ashland shale oil refinery products, experimental referee broadened-specification jet fuels, and of related isoprenoid model compounds. Supercritical fluid chromatography techniques using carbon dioxide were developed on a preparative scale, so that samples could be quantitatively separated into saturates and aromatic fractions for study by NMR. An optimized average parameter treatment was developed, and the NMR results were analyzed in terms of the resulting average parameters; formulation of model mixtures was demonstrated. Application of novel spectroscopic techniques to fuel samples was investigated.

Dalling, D. K.; Bailey, B. K.; Pugmire, R. J.

1984-01-01

29

Nuclear spin pumping and electron spin susceptibilities  

NASA Astrophysics Data System (ADS)

In this work we present a new formalism to evaluate the nuclear spin dynamics driven by hyperfine interaction with nonequilibrium electron spins. To describe the dynamics up to second order in the hyperfine coupling it suffices to evaluate the susceptibility and fluctuations of the electron spin. Our approach does not rely on a separation of electronic energy scales or the specific choice of electronic basis states, thereby overcoming practical problems which may arise in certain limits when using a more traditional formalism based on rate equations.

Danon, J.; Nazarov, Yu. V.

2011-06-01

30

Spin observables and nuclear geometry  

NASA Astrophysics Data System (ADS)

The new measurements of polarization P and spin rotation function Q in 500 MeV p-40Ca elastic scattering require geometric differences among the various parts of the p-nucleus interaction. We present a general analytic formalism which defines these differences and shows how the new experiments can be interpreted as interferometric determinations of them. NUCLEAR REACTIONS Closed form spin-dependent p-nucleus scattering amplitudes. Data-to-data relations for polarization and spin rotation.

McNeil, J. A.; Sparrow, D. A.; Amado, R. D.

1982-09-01

31

Carbon-13 nuclear magnetic resonance analysis, lignin content and carbohydrate composition of humic substances from salt marsh estuaries  

NASA Astrophysics Data System (ADS)

13C nuclear magnetic resonance spectroscopy, CuO oxidation products of lignin and hydrolyzable carbohydrates were measured for fulvic and humic acids extracted from living and dead Spartina alterniflora and salt marsh sediments. With these methods, there was little evidence for early diagenetic alteration of the humic materials. No trends consistent for fulvic and humic acids were observed for either hydrolyzable carbohydrates or lignin derived phenols, and chemical measurements of these fractions did not agree with spectral estimates. Humic acids appear to contain secondary amide linkages typical of proteins and peptides.

Alberts, James J.; Hatcher, Patrick G.; Price, Mary T.; Filip, Zdenek

32

Paramagnetic spin lattice relaxations in solid-state nuclear magnetic resonance spectroscopy  

SciTech Connect

Information on molecular structure and dynamics of solids is provided by nuclear magnetic resonance (NMR) spin lattice (T[sub 1]) relaxation experiments. The presence of an unpaired electron can significantly decrease T[sub 1]s and potentially provide details about molecular structure. This dissertation studied the influence of an unpaired spin on intramolecular carbon-13 solid-state spin lattice relaxation parameters. Porphyrins were chosen as model compounds since they can complex metals and can be synthesized with carbon-13 labels. Five carbon-13 labeled N-alkylated tetrapyridyl porphyrin tetraiodide salts were synthesized and complexed with copper(II) as the paramagnetic metal. A novel porphyrin, tetra-6[N-methyl([sup 13]C)]-quinoline porphyrin tetraiodide salt was also synthesized and complexed with copper(II). The unique approach taken in this work was to eliminate the intermolecular paramagnetic relaxation component by adsorption of the porphyrin as a surface sub-monolayer on a silica based cationic-exchange resin. Various amounts of the tetra-4-[N-methyl([sup 13]C)]-pyridyl porphyrin were adsorbed to the silica surface. This varied the average distance between porphyrin molecules. The carbon-13 spin-lattice relaxation times of the adsorbed porphyrins decreased as a function of the decreasing amounts of adsorbed porphyrin. At low porphyrin loadings (<4 [mu]moles porphyrin/g silica gel), only the intramolecular unpaired spin influence remained in the observed relaxation rate. The copper(II)-porphyrin complexes were adsorbed to the silica gel surface at the loading concentration where only intramolecular paramagnetic effects are observed. Spin lattice relaxation rates for the N-methyl carbon-13 labels on each porphyrin were measured and compared with those predicted by theory. Excellent quantitative agreement was found between the experimental and predicted relaxation times.

McCurry, J.D.

1993-01-01

33

Phosphorus-31 and carbon-13 nuclear magnetic resonance study of glucose and xylose metabolism in agarose-immobilized Candida tropicalis.  

PubMed Central

Candida tropicalis can ferment both hexose and pentose sugars. Here, we have used 31P and 13C nuclear magnetic resonance spectroscopy to study the capacity of this yeast species to metabolize glucose or xylose when immobilized in small (< 1-mm-diameter) agarose beads. Immobilized C. tropicalis metabolizing glucose showed rapid initial growth within the beads. A corresponding drop in the intracellular pH (from 7.8 to 7.25) and hydrolysis of intracellular polyphosphate stores were observed. Although the initial rate of glucose metabolism with immobilized C. tropicalis was similar to the rate observed previously in cell suspensions, a decrease by a factor of 2.5 occurred over 24 h. In addition to ethanol, a significant amount of glycerol was also produced. When immobilized C. tropicalis consumed xylose, cell growth within the beads was minimal. The intracellular pH dropped rapidly by 1.05 pH units to 6.4. Intracellular ATP levels were lower and intracellular Pi levels were higher than observed with glucose-perfused cells. Consumption of xylose by immobilized C. tropicalis was slower than was previously observed for oxygen-limited cell suspensions, and xylitol was the only fermentation product.

Lohmeier-Vogel, E M; Hahn-Hagerdal, B; Vogel, H J

1995-01-01

34

Electron spin decoherence in nuclear spin baths and dynamical decoupling  

SciTech Connect

We introduce the quantum theory of the electron spin decoherence in a nuclear spin bath and the dynamical decoupling approach for protecting the electron spin coherence. These theories are applied to various solid-state systems, such as radical spins in molecular crystals and NV centers in diamond.

Zhao, N.; Yang, W.; Ho, S. W.; Hu, J. L.; Wan, J. T. K.; Liu, R. B. [Department of Physics, Chinese University of Hong Kong, Shatin, New Territories (Hong Kong)

2011-12-23

35

Nuclear spin effects in semiconductor quantum dots  

NASA Astrophysics Data System (ADS)

The interaction of an electronic spin with its nuclear environment, an issue known as the central spin problem, has been the subject of considerable attention due to its relevance for spin-based quantum computation using semiconductor quantum dots. Independent control of the nuclear spin bath using nuclear magnetic resonance techniques and dynamic nuclear polarization using the central spin itself offer unique possibilities for manipulating the nuclear bath with significant consequences for the coherence and controlled manipulation of the central spin. Here we review some of the recent optical and transport experiments that have explored this central spin problem using semiconductor quantum dots. We focus on the interaction between 104-106 nuclear spins and a spin of a single electron or valence-band hole. We also review the experimental techniques as well as the key theoretical ideas and the implications for quantum information science.

Chekhovich, E. A.; Makhonin, M. N.; Tartakovskii, A. I.; Yacoby, A.; Bluhm, H.; Nowack, K. C.; Vandersypen, L. M. K.

2013-06-01

36

A Short Set of Carbon 13-NMR Correlation Tables.  

ERIC Educational Resources Information Center

Presents a short set of carbon-13 nuclear magnetic resonance (NMR) tables. These tables not only serve pedagogic purposes but also allow students to do calculations rapidly and with acceptable accuracy for a wide variety of compounds. (JN)

Brown, D. W.

1985-01-01

37

Molecular determinants for drug-receptor interactions. 8. Anisotropic and internal motions in morphine, nalorphine, oxymorphone, naloxone and naltrexone in aqueous solution by carbon-13 NMR spin-lattice relaxation times  

NASA Astrophysics Data System (ADS)

Carbon-13 NMR spin-lattice relaxation times ( T1) were measured for morphine, oxymorphone, nalorphine, naloxone and naltrexone as hydrochloride salts in 2H 2O solution. The data refer to the molecules in the N-equatorial configuration. The experimental T1 values were interpreted using a model of anisotropic reorientation of a rigid body with superimposed internal motions of the flexible N-methyl, N-methyl-allyl and N-methyl-cyclopropyl fragments. The calculated internal motional rates were found to markedly decrease on passing from agonists to mixed (nalorphine) and pure (naloxone, naltrexone) antagonists. For these latter the observed trend of the internal flexibility about N?C and C?C bonds of the N-substituents is discussed in terms of a correlation with their relative antagonistic potencies. In fact, such an evidence of decreasing internal conformational dynamics in the order nalorphine, naloxone, naltrexone, appeared interestingly in line with the "two-state" model of opiate receptor operation mode proposed by Snyder.

Grassi, Antonio; Perly, Bruno; Pappalardo, Giuseppe C.

1989-02-01

38

Spin excitations in di-nuclear systems  

SciTech Connect

The spin excitations of products from two-body reactions have two sources: transfer of orbital motion into intrinsic spins via tangential friction and thermal excitations of di-nuclear spin modes. The relative importance of these two mechanisms is discussed for deep inelastic scattering, quasi-fission and spontaneous fission processes. The results of simple model calculations are compared to measured {gamma}-multiplicities in {sup 238}U induced quasi-fission reactions and it is concluded that the spin-excitation are only partially equilibrated during the interaction. 11 refs., 5 figs.

Back, B.B.

1990-01-01

39

Nuclear Spin Dipolar Relaxation in Paramagnetic Systems Undergoing Multiple Internal Motions.  

National Technical Information Service (NTIS)

A theoretical treatment is proposed for the relaxation induced by the dipolar interaction between two spins separated by several bonds. The influence of the internal and overall molecular motions upon the carbon 13 longitudinal relaxation is discussed on ...

A. Tsutsumi J. P. Quaegebeur C. Chachaty

1979-01-01

40

The physical state of osmoregulatory solutes in unicellular algae. A natural-abundance carbon-13 nuclear-magnetic-resonance relaxation study.  

PubMed Central

Natural-abundance 13C n.m.r. spin-lattice relaxation-time measurements have been carried out on intact cells of the unicellular blue--green alga Synechococcus sp. and the unicellular green alga Dunaliella salina, with the aim of characterizing the environments of the organic osmoregulatory solutes in these salt-tolerant organisms. In Synechococcus sp., all of the major organic osmoregulatory solute, 2-O-alpha-D-glucopyranosylglycerol, is visible in spectra of intact cells. Its rotational motion in the cell is slower by a factor of approx. 2.4 than in aqueous solution, but the molecule is still freely mobile and therefore able to contribute to the osmotic balance. In D. salina, only about 60% of the osmoregulatory solute glycerol is visible in spectra of intact cells. The rotational mobility of this observable fraction is approximately half that found in aqueous solution, but the data also indicate that there is a significant concentration of some paramagnetic species in D. salina which contributes to the overall spin-lattice relaxation of the glycerol carbon atoms. The non-observable fraction, which must correspond to glycerol molecules that have very broad 13C resonances and that are in slow exchange with bulk glycerol, has not been properly characterized as yet, but may represent glycerol in the chloroplast. The implications of these findings in relation to the physical state of the cytoplasm and the mechanism of osmoregulation in these cells are discussed.

Norton, R S; MacKay, M A; Borowitzka, L J

1982-01-01

41

Assignments in the Carbon-13 Nuclear Magnetic Resonance Spectra of Vitamin B12, Coenzyme B12, and Other Corrinoids: Application of Partially-Relaxed Fourier Transform Spectroscopy  

PubMed Central

High-resolution Fourier transform NMR at 15.08 MHz was used to observe the proton-decoupled natural-abundance 13C spectra of aqueous solutions of cobinamide dicyanide (0.067 M), cyanocobalamin (0.024 M), dicyanocobalamin (0.14 M), and coenzyme B12 (0.038 M). Assignments were made with the aid of chemical shift comparisons, off-resonance single-frequency proton decoupling, partially-relaxed Fourier transform spectra, and splittings arising from 13C-31P coupling. As expected, the 13C spectra of the coronoids were appreciably more informative than the corresponding proton spectra. Nearly all the lines in the 13C spectra of the corrinoids were well-resolved single-carbon resonances, in spite of the structural complexity. Partially relaxed 13C Fourier transform NMR spectra, which yield spin-lattice relaxation times of each resolved resonance, were found to be a very useful addition to the arsenal of NMR techniques.

Doddrell, David; Allerhand, Adam

1971-01-01

42

Detection and Control of Individual Nuclear Spins Using a Weakly Coupled Electron Spin  

SciTech Connect

We experimentally isolate, characterize, and coherently control up to six individual nuclear spins that are weakly coupled to an electron spin in diamond. Our method employs multipulse sequences on the electron spin that resonantly amplify the interaction with a selected nuclear spin and at the same time dynamically suppress decoherence caused by the rest of the spin bath. We are able to address nuclear spins with interaction strengths that are an order of magnitude smaller than the electron spin dephasing rate. Our results provide a route towards tomography with single-nuclear-spin sensitivity and greatly extend the number of available quantum bits for quantum information processing in diamond.

Taminiau, T.H.; Wagenaar, J.J.T.; van der Sar, T.; Jelezko, F.; Dobrovitski, Viatcheslav V.; Hanson, R.

2012-09-28

43

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

44

Single-nuclear-spin cavity QED  

SciTech Connect

We constructed a cavity QED system with a diamagnetic atom of {sup 171}Yb and performed projective measurements on a single nuclear spin. Since Yb has no electronic spin and has 1/2 nuclear spin, the procedure of spin polarization and state verification can be dramatically simplified compared with the pseudo-spin-1/2 system. By enhancing the photon emission rate of the {sup 1}S{sub 0}-{sup 3}P{sub 1} transition, projective measurement is implemented for an atom with the measurement time of T{sub meas}=30 {mu}s. Unwanted spin flip and dark counts of the detector lead to systematic error when the present technique is applied for the determination of diagonal elements of an unknown spin state, which is {delta}|{beta}|{sup 2{<=}}2x10{sup -2}. Fast measurement on a long-lived qubit is key to the realization of large-scale one-way quantum computing.

Takeuchi, Makoto; Takei, Nobuyuki; Zhang Peng [ERATO Macroscopic Quantum Control Project, JST, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan); Doi, Kodai; Kozuma, Mikio [ERATO Macroscopic Quantum Control Project, JST, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan); Department of Physics, Tokyo Institute of Technology, 2-12-1 O-Okayama, Meguro-ku, Tokyo 152-8550 (Japan); Ueda, Masahito [ERATO Macroscopic Quantum Control Project, JST, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan); Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2010-06-15

45

Density functional theory study of indirect nuclear spin-spin coupling constants with spin-orbit corrections  

Microsoft Academic Search

This work outlines the calculation of indirect nuclear spin-spin coupling constants with spin-orbit corrections using density functional response theory. The nonrelativistic indirect nuclear spin-spin couplings are evaluated using the linear response method, whereas the relativistic spin-orbit corrections are computed using quadratic response theory. The formalism is applied to the homologous systems H2X (X=O,S,Se,Te) and XH4 (X=C,Si,Ge,Sn,Pb) to calculate the indirect

Corneliu I. Oprea; Zilvinas Rinkevicius; Olav Vahtras; Hans Gren; Kenneth Ruud

2005-01-01

46

Spin observables and nuclear geometry  

SciTech Connect

The new measurements of polarization P and spin rotation function Q in 500 MeV p- /sup 40/Ca elastic scattering require geometric differences among the various parts of the p-nucleus interaction. We present a general analytic formalism which defines these differences and shows how the new experiments can be interpreted as interferometric determinations of them.

McNeil, J.A.; Sparrow, D.A.; Amado, R.D.

1982-09-01

47

Nuclear Spin Effect in a Metallic Spin Valve  

NASA Astrophysics Data System (ADS)

We study electronic transport through a ferromagnet normal-metal ferromagnet system and we investigate the effect of hyperfine interaction between electrons and nuclei in the normal-metal part. A switching of the magnetization directions of the ferromagnets causes nuclear spins to precess. We show that the effect of this precession on the current through the system is large enough to be observed in experiment.

Danon, J.; Nazarov, Yu. V.

2006-10-01

48

Optical switching of nuclear spin-spin couplings in semiconductors  

PubMed Central

Two-qubit operation is an essential part of quantum computation. However, solid-state nuclear magnetic resonance quantum computing has not been able to fully implement this functionality, because it requires a switchable inter-qubit coupling that controls the time evolutions of entanglements. Nuclear dipolar coupling is beneficial in that it is present whenever nuclear–spin qubits are close to each other, while it complicates two-qubit operation because the qubits must remain decoupled to prevent unwanted couplings. Here we introduce optically controllable internuclear coupling in semiconductors. The coupling strength can be adjusted externally through light power and even allows on/off switching. This feature provides a simple way of switching inter-qubit couplings in semiconductor-based quantum computers. In addition, its long reach compared with nuclear dipolar couplings allows a variety of options for arranging qubits, as they need not be next to each other to secure couplings.

Goto, Atsushi; Ohki, Shinobu; Hashi, Kenjiro; Shimizu, Tadashi

2011-01-01

49

Nuclear binding energy at high spin  

SciTech Connect

A method to calculate absolute values of the total nuclear binding energy in the high-spin regime is briefly described. Applications to test the position of specific orbitals are examplified on Z = 36 Kr isotopes with N 36 - 38. Calculated binding energies of possible configurations for one dipole band in 199Pb are compared with experiment.

Carlsson, B. G.; Ragnarsson, I. [Div. of Mathematical Physics, LTH, Lund University, P.O. Box 118, SE-221 00 Lund (Sweden)

2006-04-26

50

Nuclear spin state relaxation in formaldehyde  

NASA Astrophysics Data System (ADS)

Measurements of ortho- to para-formaldehyde conversion rate constants are described. They are based on the fact that a clean photolysis of one nuclear spin modification is possible in the natural mixture with the help of narrow band UV laser radiation. Rate constants are of the order of k1 = 5 × 10 -3 s -1 under the experimental conditions used in our measurements.

Kern, J.; Schwahn, H.; Schramm, B.

1989-01-01

51

Nuclear Spin Ordering Observed by Neutron Diffraction.  

National Technical Information Service (NTIS)

A review is given of recent neutron scattering experiments which have been carried out at milli-Kelvin temperatures to study the hyperfine-enhanced nuclear-spin ordering in the singlet electronic ground state compounds PrSn sub 3 , PrCu sub 2 , and HoVO s...

R. M. Nicklow R. M. Moon S. Kawarazaki N. Kunitomi H. Suzuki

1984-01-01

52

Nuclear spin physics in quantum dots: An optical investigation  

NASA Astrophysics Data System (ADS)

The mesoscopic spin system formed by the 104-106 nuclear spins in a semiconductor quantum dot offers a unique setting for the study of many-body spin physics in the condensed matter. The dynamics of this system and its coupling to electron spins is fundamentally different from its bulk counterpart or the case of individual atoms due to increased fluctuations that result from reduced dimensions. In recent years, the interest in studying quantum-dot nuclear spin systems and their coupling to confined electron spins has been further fueled by its importance for possible quantum information processing applications. The fascinating nonlinear (quantum) dynamics of the coupled electron-nuclear spin system is universal in quantum dot optics and transport. In this article, experimental work performed over the last decade in studying this mesoscopic, coupled electron-nuclear spin system is reviewed. Here a special focus is on how optical addressing of electron spins can be exploited to manipulate and read out the quantum-dot nuclei. Particularly exciting recent developments in applying optical techniques to efficiently establish nonzero mean nuclear spin polarizations and using them to reduce intrinsic nuclear spin fluctuations are discussed. Both results critically influence the preservation of electron-spin coherence in quantum dots. This overall recently gained understanding of the quantum-dot nuclear spin system could enable exciting new research avenues such as experimental observations of spontaneous spin ordering or nonclassical behavior of the nuclear spin bath.

Urbaszek, Bernhard; Marie, Xavier; Amand, Thierry; Krebs, Olivier; Voisin, Paul; Maletinsky, Patrick; Högele, Alexander; Imamoglu, Atac

2013-01-01

53

Ultralong spin decoherence times in graphene quantum dots with a small number of nuclear spins  

NASA Astrophysics Data System (ADS)

We study the dynamics of an electron spin in a graphene quantum dot, which is interacting with a bath of less than ten nuclear spins via the anisotropic hyperfine interaction. Due to substantial progress in the fabrication of graphene quantum dots, the consideration of such a small number of nuclear spins is experimentally relevant. This choice allows us to use exact diagonalization to calculate the long-time average of the electron spin as well as its decoherence time. We investigate the dependence of spin observables on the initial states of nuclear spins and on the position of nuclear spins in the quantum dot. Moreover, we analyze the effects of the anisotropy of the hyperfine interaction for different orientations of the spin quantization axis with respect to the graphene plane. Interestingly, we then predict remarkable long decoherence times of more than 10 ms in the limit of few nuclear spins.

Fuchs, Moritz; Schliemann, John; Trauzettel, Björn

2013-12-01

54

Spin-isospin nuclear response  

SciTech Connect

The scattering of protons off individual nucleons in the nucleus, known as 'quasi-free' scattering, gives information on the modification of the nuclear force inside the nuclear medium. In order to extract this information, we need to know the nucleon-nucleon (N-N) interaction in free space, and the propagation of the proton through the nucleus (from elastic scattering). Direct comparison of the analyzing powers and polarizations for quasi-free scattering as opposed to N-N scattering show large (40%) differences. Conventional (non-relativistic) calculations are unable to reproduce this effect. Relativistic calculations, which use large, opposing vector and scalar potentials reproduce this effect for both isoscalar and isovector inclusive reactions and for exclusive (p, 2p) reactions.

Hicks, K.H.

1988-11-20

55

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

56

Dynamic nuclear spin polarization in an all-semiconductor spin injection device with (Ga,Mn)As/n-GaAs spin Esaki diode  

NASA Astrophysics Data System (ADS)

We investigate the dynamic nuclear spin polarization in an n-GaAs lateral channel induced by electrical spin injection from a (Ga,Mn)As/n-GaAs spin Esaki diode. Signatures of nuclear spin polarization are studied in both three-terminal and non-local voltage signals, where a strong electron spin depolarization feature is observed close to zero magnetic field. This is due to the large nuclear field induced in the channel through hyperfine interaction between injected electron spins and localized nuclear spins. We study the time evolution of the dynamic nuclear spin polarization and evaluate polarization and relaxation times of nuclear spins in the channel.

Shiogai, J.; Ciorga, M.; Utz, M.; Schuh, D.; Arakawa, T.; Kohda, M.; Kobayashi, K.; Ono, T.; Wegscheider, W.; Weiss, D.; Nitta, J.

2012-11-01

57

Spin phase coherence of donor nuclear spins in silicon: the influence of electrical readout  

NASA Astrophysics Data System (ADS)

Storing information in spin underpins the operation of a wide range of emerging technologies. However, the ability to interact with, and thus control electron spin implies a reasonable coupling to the environment, and a correspondingly limited spin coherence time. This problem can be overcome by using nuclear spins for long term information storage, and significant experimental progress in this direction has been seen recently. Readout of stored information can be achieved in a variety of ways, with electrical approaches offering substantial benefit with regard to integration of spintronic and classical electronic applications. Here, we discuss electrical readout of coherent nuclear spin states of donor nuclei in silicon. By utilizing nuclear Hahn echo sequences, we are able to demonstrate that nuclear spin phase coherence can exceed 3 ms with electrical readout. We find that the spin phase coherence is in this case limited by the spin lifetime of the donor electron which mediates our readout scheme, and discuss approaches to ameliorate this effect.

McCamey, Dane; van Tol, Johan; Morley, Gavin; Boehme, Christoph

2012-02-01

58

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

59

Electron spin dephasing due to hyperfine interactions with a nuclear spin bath.  

PubMed

We investigate pure dephasing decoherence (free induction decay and spin echo) of a spin qubit interacting with a nuclear spin bath. While for infinite magnetic field B the only decoherence mechanism is spectral diffusion due to dipolar flip-flops of nuclear spins, with decreasing B the hyperfine-mediated interactions between the nuclear spins become important. We give a theory of decoherence due to these interactions which takes advantage of their long-range nature. For a thermal uncorrelated bath we show that our theory is applicable down to B approximately 10 mT, allowing for comparison with recent experiments in GaAs quantum dots. PMID:19257553

Cywi?ski, Lukasz; Witzel, Wayne M; Das Sarma, S

2009-02-01

60

Adiabatic refocusing of nuclear spins in Tm3+:YAG  

NASA Astrophysics Data System (ADS)

We show that the optical absorbance detection of nuclear spin echo gives direct access to the spin concentration, unlike most coherent signal detection techniques where the signal intensity/amplitude is difficult to connect experimentally with the spin concentration. This way we measure the spin-refocusing efficiency in a crystal of Tm3+:YAG. Given the large inhomogeneous broadening of the spin transition in this material, rephasing the spins with the usual hard pulse procedure would require excessively high radiofrequency power. Instead we resort to an adiabatic pulse sequence that perfectly returns the spins to their initial common orientation, at low power cost.

Lauro, R.; Chanelière, T.; Le Gouët, J.-L.

2011-01-01

61

Nuclear spin polarized H and D by means of spin-exchange optical pumping  

NASA Astrophysics Data System (ADS)

Optically pumped spin-exchange sources for polarized hydrogen and deuterium atoms have been demonstrated to yield high atomic flow and high electron spin polarization. For maximum nuclear polarization the source has to be operated in spin temperature equilibrium, which has already been demonstrated for hydrogen. In spin temperature equilibrium the nuclear spin polarization PI equals the electron spin polarization PS for hydrogen and is even larger than PS for deuterium. We discuss the general properties of spin temperature equilibrium for a sample of deuterium atoms. One result are the equations PI=4PS/(3+PS2) and Pzz=PS.PI, where Pzz is the nuclear tensor polarization. Furthermore we demonstrate that the deuterium atoms from our source are in spin temperature equilibrium within the experimental accuracy.

Stenger, Jörn; Grosshauser, Carsten; Kilian, Wolfgang; Nagengast, Wolfgang; Ranzenberger, Bernd; Rith, Klaus; Schmidt, Frank

1998-01-01

62

Increasing the electron spin coherence time by coherent optical control of the nuclear spin fluctuations  

NASA Astrophysics Data System (ADS)

A single electron spin plays a central role for spin-based quantum information science and electronic devices. One crucial requirement for the future success is to have a long quantum coherence time. It has been demonstrated that in III-V materials, the electron spin coherence time deteriorates rapidly due to the hyperfine coupling with the nuclear environment. Here, we report the increase of the electron spin coherence time by optical controlled suppression of nuclear spin fluctuations through coherent dark-state spectroscopy. The experiment is performed in a single negatively charged InAs self assembled quantum dot (SAQD). The dynamic nuclear spin polarization manifests itself as a hysteresis in the probe absorption spectrum and in the spectral position of the dark state as a function of the frequency scanning direction of the probe field. We demonstrated that the nuclear field can be locked to the maximum trion excitation by observing a flat-top of the trion absorption lineshape, and the switching of the nuclei from unstable to stable configurations by fixing the laser frequencies and monitoring the coherent optical response as a function of time. The optically controlled locking of the nuclear field leads to an enhancement of the electron spin coherence time, which is measured through dark state spectroscopy. The suppression of the nuclear field fluctuations result from a hole spin assisted dynamic nuclear spin polarization feed-back process. We further demonstrated the electron spin coherence enhancement by a three-beam measurement, where two-pump beams lock the nuclear field and the third probe measures the coherence time through the dark state. The inferred spin coherence time is increased by nearly 3 orders of magnitude compared to its thermal value. Our work lays the groundwork for the reproducible preparation of the nuclear spin environment for repetitive control and measurement of a single spin with minimal statistical broadening.

Xu, Xiaodong

2010-03-01

63

Electron Spin Dephasing and Decoherence by Interaction with Nuclear Spins in Self-Assembled Quantum Dots  

NASA Technical Reports Server (NTRS)

Electron spin dephasing and decoherence by its interaction with nuclear spins in self-assembled quantum dots are investigated in the framework of the empirical tight-binding model. Electron spin dephasing in an ensemble of dots is induced by the inhomogeneous precession frequencies of the electron among dots, while electron spin decoherence in a single dot arises from the inhomogeneous precession frequencies of nuclear spins in the dot. For In(x)Ga(1-x) As self-assembled dots containing 30000 nuclei, the dephasing and decoherence times are predicted to be on the order of 100 ps and 1 (micro)s.

Lee, Seungwon; vonAllmen, Paul; Oyafuso, Fabiano; Klimeck, Gerhard; Whale, K. Birgitta

2004-01-01

64

Single-Shot Readout of a Single Nuclear Spin  

NASA Astrophysics Data System (ADS)

Projective measurement of single electron and nuclear spins has evolved from a gedanken experiment to a problem relevant for applications in atomic-scale technologies like quantum computing. Although several approaches allow for detection of a spin of single atoms and molecules, multiple repetitions of the experiment that are usually required for achieving a detectable signal obscure the intrinsic quantum nature of the spin’s behavior. We demonstrated single-shot, projective measurement of a single nuclear spin in diamond using a quantum nondemolition measurement scheme, which allows real-time observation of an individual nuclear spin’s state in a room-temperature solid. Such an ideal measurement is crucial for realization of, for example, quantum error correction protocols in a quantum register.

Neumann, Philipp; Beck, Johannes; Steiner, Matthias; Rempp, Florian; Fedder, Helmut; Hemmer, Philip R.; Wrachtrup, Jörg; Jelezko, Fedor

2010-07-01

65

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

66

Optically enhanced nuclear spin polarization in InP  

NASA Astrophysics Data System (ADS)

Optically induced nuclear spin polarization is studied via time-resolved magnetooptical Kerr effect in Voigt configuration in n-doped InP. The hyperfine field acting on electrons is detected via a phase shift of the electron spin precession. The dependence of the hyperfine field on external field and the polarization time of the nuclei are discussed within a simple model neglecting nuclear spin diffusion.

Brunetti, A.; Vladimirova, M.; Scalbert, D.; Folliot, H.; Lecorre, A.

2007-04-01

67

Repetitive readout of a single electronic spin via quantum logic with nuclear spin ancillae.  

PubMed

Robust measurement of single quantum bits plays a key role in the realization of quantum computation and communication as well as in quantum metrology and sensing. We have implemented a method for the improved readout of single electronic spin qubits in solid-state systems. The method makes use of quantum logic operations on a system consisting of a single electronic spin and several proximal nuclear spin ancillae in order to repetitively readout the state of the electronic spin. Using coherent manipulation of a single nitrogen vacancy center in room-temperature diamond, full quantum control of an electronic-nuclear system consisting of up to three spins was achieved. We took advantage of a single nuclear-spin memory in order to obtain a 10-fold enhancement in the signal amplitude of the electronic spin readout. We also present a two-level, concatenated procedure to improve the readout by use of a pair of nuclear spin ancillae, an important step toward the realization of robust quantum information processors using electronic- and nuclear-spin qubits. Our technique can be used to improve the sensitivity and speed of spin-based nanoscale diamond magnetometers. PMID:19745117

Jiang, L; Hodges, J S; Maze, J R; Maurer, P; Taylor, J M; Cory, D G; Hemmer, P R; Walsworth, R L; Yacoby, A; Zibrov, A S; Lukin, M D

2009-10-01

68

Spin Modes in Nuclei and Nuclear Forces  

SciTech Connect

Spin modes in stable and unstable exotic 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 shell evolutions toward drip-lines and spin properties of both stable and exotic nuclei, for example, Gamow-Teller transitions in {sup 12}C and {sup 14}C and an anomalous M1 transition in {sup 17}C. The importance and the necessity of the repulsive monopole corrections in isospin T = 1 channel to the microscopic two-body interactions are pointed out. The corrections are shown to lead to the proper shell evolutions in neutron-rich isotopes. The three-body force, in particular the Fujita-Miyazawa force induced by {Delta} 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 and transitions in exotic oxygen and calcium isotopes are demonstrated.

Suzuki, Toshio [Department of Physics and Graduate School of Integrated Basic Sciences, College of Humanities and Sciences, Nihon University, Sakurajosui 3-25-40, Setagaya-ku, Tokyo 156-8550 (Japan) and Center for Nuclear Study, University of Tokyo, Hirosawa, Wako-shi, Saitama, 351-0198 (Japan); Otsuka, Takaharu [Department of Physics and Center for Nuclear Study, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2011-05-06

69

Electronic read-out of a single nuclear spin using a molecular spin transistor  

NASA Astrophysics Data System (ADS)

Thanks to recent advances of nanofabrication techniques, molecular electronics devices can address today the ultimate probing of electronic transport flowing through a single molecule. Not only this electronic current can show signatures of the molecular quantum levels but it can also detect the magnetic state of the molecule. As a consequence, an entirely novel research field called molecular spintronics in which quantum magnetism of molecular systems can be interfaced to nanoelectronics is now emerging. One of the recent challenges of this field was to probe by this current, not the only spin state of an electron, but the state of a single nuclear spin. Such an achievement was experimentally unimaginable a few years ago. Indeed, the magnetic signal carried by a single nuclear spin is a thousand times less than that of a single electron spin ... Using a Single Molecular Magnet (TbPc2) as a molecular spin transistor in a three terminals configuration, the experiment consists in measuring the current changes when ones sweep the external magnetic field applied to the molecule. When the magnetic spin of the molecule changes its quantum state, a change of current is recorded. Because of the well-defined relationship that exists between the electron spin and nuclear spin carried by the nuclei of the Terbium atom, it is possible to perform the electronic read-out of the electronic spin state which, in turn give information on the state of a single nuclear spin. Application of this effect for quantum information manipulation and storage can be envisioned, as the observation of energy level lifetimes on the order of tens of seconds opens the way to coherent manipulations of a single nuclear spin.[4pt] Reference:[0pt] ``Electronic read-out of a single nuclear spin using a molecular spin transistor,'' R. Vincent, S. Klyatskaya, M. Ruben, W. Wernsdorfer, F. Balestro, Nature, Vol. 488, p.357, (2012).

Balestro, Franck

2013-03-01

70

Sensitive magnetic control of ensemble nuclear spin hyperpolarization in diamond  

NASA Astrophysics Data System (ADS)

Dynamic nuclear polarization, which transfers the spin polarization of electrons to nuclei, is routinely applied to enhance the sensitivity of nuclear magnetic resonance. This method is particularly useful when spin hyperpolarization can be produced and controlled optically or electrically. Here we show complete polarization of nuclei located near optically polarized nitrogen-vacancy centres in diamond. Close to the ground-state level anti-crossing condition of the nitrogen-vacancy electron spins, 13C nuclei in the first shell are polarized in a pattern that depends sensitively upon the magnetic field. Based on the anisotropy of the hyperfine coupling and of the optical polarization mechanism, we predict and observe a reversal of the nuclear spin polarization with only a few millitesla change in the magnetic field. This method of magnetic control of high nuclear polarization at room temperature can be applied in sensitivity enhanced nuclear magnetic resonance of bulk nuclei, nuclear-based spintronics, and quantum computation in diamond.

Wang, Hai-Jing; Shin, Chang S.; Avalos, Claudia E.; Seltzer, Scott J.; Budker, Dmitry; Pines, Alexander; Bajaj, Vikram S.

2013-06-01

71

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

72

Preparation of nuclear spin singlet states using spin-lock induced crossing.  

PubMed

We introduce a broadly applicable technique to create nuclear spin singlet states in organic molecules and other many-atom systems. We employ a novel pulse sequence to produce a spin-lock induced crossing (SLIC) of the spin singlet and triplet energy levels, which enables triplet-singlet polarization transfer and singlet-state preparation. We demonstrate the utility of the SLIC method by producing a long-lived nuclear spin singlet state on two strongly coupled proton pairs in the tripeptide molecule phenylalanine-glycine-glycine dissolved in D(2)O and by using SLIC to measure the J couplings, chemical shift differences, and singlet lifetimes of the proton pairs. We show that SLIC is more efficient at creating nearly equivalent nuclear spin singlet states than previous pulse sequence techniques, especially when triplet-singlet polarization transfer occurs on the same time scale as spin-lattice relaxation. PMID:24206484

DeVience, Stephen J; Walsworth, Ronald L; Rosen, Matthew S

2013-10-25

73

Preparation of Nuclear Spin Singlet States Using Spin-Lock Induced Crossing  

NASA Astrophysics Data System (ADS)

We introduce a broadly applicable technique to create nuclear spin singlet states in organic molecules and other many-atom systems. We employ a novel pulse sequence to produce a spin-lock induced crossing (SLIC) of the spin singlet and triplet energy levels, which enables triplet-singlet polarization transfer and singlet-state preparation. We demonstrate the utility of the SLIC method by producing a long-lived nuclear spin singlet state on two strongly coupled proton pairs in the tripeptide molecule phenylalanine-glycine-glycine dissolved in D2O and by using SLIC to measure the J couplings, chemical shift differences, and singlet lifetimes of the proton pairs. We show that SLIC is more efficient at creating nearly equivalent nuclear spin singlet states than previous pulse sequence techniques, especially when triplet-singlet polarization transfer occurs on the same time scale as spin-lattice relaxation.

DeVience, Stephen J.; Walsworth, Ronald L.; Rosen, Matthew S.

2013-10-01

74

Single-shot readout of a single nuclear spin.  

PubMed

Projective measurement of single electron and nuclear spins has evolved from a gedanken experiment to a problem relevant for applications in atomic-scale technologies like quantum computing. Although several approaches allow for detection of a spin of single atoms and molecules, multiple repetitions of the experiment that are usually required for achieving a detectable signal obscure the intrinsic quantum nature of the spin's behavior. We demonstrated single-shot, projective measurement of a single nuclear spin in diamond using a quantum nondemolition measurement scheme, which allows real-time observation of an individual nuclear spin's state in a room-temperature solid. Such an ideal measurement is crucial for realization of, for example, quantum error correction protocols in a quantum register. PMID:20595582

Neumann, Philipp; Beck, Johannes; Steiner, Matthias; Rempp, Florian; Fedder, Helmut; Hemmer, Philip R; Wrachtrup, Jörg; Jelezko, Fedor

2010-07-30

75

Nuclear Spin Gyroscope Based on an Atomic Comagnetometer  

Microsoft Academic Search

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

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

2005-01-01

76

Polarization of nuclear spins by a cold nanoscale resonator  

NASA Astrophysics Data System (ADS)

A cold nanoscale resonator coupled to a system of nuclear spins can induce spin relaxation. In the low-temperature limit where spin-lattice interactions are “frozen out,” spontaneous emission by nuclear spins into a resonant mechanical mode can become the dominant mechanism for cooling the spins to thermal equilibrium with their environment. We provide a theoretical framework for the study of resonator-induced cooling of nuclear spins in this low-temperature regime. Relaxation equations are derived from first principles, in the limit where energy donated by the spins to the resonator is quickly dissipated into the cold bath that damps it. A physical interpretation of the processes contributing to spin polarization is given. For a system of spins that have identical couplings to the resonator, the interaction Hamiltonian conserves spin angular momentum, and the resonator cannot relax the spins to thermal equilibrium unless this symmetry is broken by the spin Hamiltonian. The mechanism by which such a spin system becomes “trapped” away from thermal equilibrium can be visualized using a semiclassical model, which shows how an indirect spin-spin interaction arises from the coupling of multiple spins to one resonator. The internal spin Hamiltonian can affect the polarization process in two ways: (1) By modifying the structure of the spin-spin correlations in the energy eigenstates, and (2) by splitting the degeneracy within a manifold of energy eigenstates, so that zero-frequency off-diagonal terms in the density matrix are converted to oscillating coherences. Shifting the frequencies of these coherences sufficiently far from zero suppresses the development of resonator-induced correlations within the manifold during polarization from a totally disordered state. Modification of the spin-spin correlations by means of either mechanism affects the strength of the fluctuating spin dipole that drives the resonator. In the case where product states can be chosen as energy eigenstates, spontaneous emission from eigenstate populations into the resonant mode can be interpreted as independent emission by individual spins, and the spins relax exponentially to thermal equilibrium if the development of resonator-induced correlations is suppressed. When the spin Hamiltonian includes a significant contribution from the homonuclear dipolar coupling, the energy eigenstates entail a correlation specific to the coupling network. Simulations of dipole-dipole coupled systems of up to five spins suggest that these systems contain weakly emitting eigenstates that can trap a fraction of the population for time periods ?100/R0, where R0 is the rate constant for resonator-enhanced spontaneous emission by a single spin 1/2. Much of the polarization, however, relaxes with rates comparable to R0. A distribution of characteristic high-field chemical shifts tends to increase the relaxation rates of weakly emitting states, enabling transitions to states that can quickly relax to thermal equilibrium. The theoretical framework presented in this paper is illustrated with discussions of spin polarization in the contexts of force-detected nuclear-magnetic-resonance spectroscopy and magnetic-resonance force microscopy.

Butler, Mark C.; Weitekamp, Daniel P.

2011-12-01

77

Spin Saturation and Thermal Properties of Nuclear Matter.  

National Technical Information Service (NTIS)

The binding energy and the incompressibility of nuclear matter with degree of spin saturation D is calculated using the Skyrme interaction and two forms of a velocity dependent effective potential. The effect of the degree of spin saturation D on the ther...

M. Y. M. Hassan S. Ramadan

1983-01-01

78

Electronic readout of a single nuclear spin using a molecular spin transistor  

NASA Astrophysics Data System (ADS)

Quantum control of individual spins in condensed matter devices is an emerging field with a wide range of applications ranging from nanospintronics to quantum computing [1,2]. The electron, with its spin and orbital degrees of freedom, is conventionally used as carrier of the quantum information in the devices proposed so far. However, electrons exhibit a strong coupling to the environment leading to reduced relaxation and coherence times. Indeed quantum coherence and stable entanglement of electron spins are extremely difficult to achieve. We propose a new approach using the nuclear spin of an individual metal atom embedded in a single-molecule magnet (SMM). In order to perform the readout of the nuclear spin, the quantum tunneling of the magnetization (QTM) of the magnetic moment of the SMM in a transitor-like set-up is electronically detected. Long spin lifetimes of an individual nuclear spin were observed and the relaxation characteristics were studied. The manipulation of the nuclear spin state of individual atoms embedded in magnetic molecules opens a completely new world, where quantum logic may be integrated.[4pt] [1] L. Bogani, W. Wernsdorfer, Nature Mat. 7, 179 (2008).[0pt] [2] M. Urdampilleta, S. Klyatskaya, J.P. Cleuziou, M. Ruben, W. Wernsdorfer, Nature Mat. 10, 502 (2011).

Vincent, R.; Klyastskaya, S.; Ruben, M.; Wernsdorfer, W.; Balestro, F.

2012-02-01

79

Electronic read-out of a single nuclear spin using a molecular spin transistor.  

PubMed

Quantum control of individual spins in condensed-matter devices is an emerging field with a wide range of applications, from nanospintronics to quantum computing. The electron, possessing spin and orbital degrees of freedom, is conventionally used as the carrier of quantum information in proposed devices. However, electrons couple strongly to the environment, and so have very short relaxation and coherence times. It is therefore extremely difficult to achieve quantum coherence and stable entanglement of electron spins. Alternative concepts propose nuclear spins as the building blocks for quantum computing, because such spins are extremely well isolated from the environment and less prone to decoherence. However, weak coupling comes at a price: it remains challenging to address and manipulate individual nuclear spins. Here we show that the nuclear spin of an individual metal atom embedded in a single-molecule magnet can be read out electronically. The observed long lifetimes (tens of seconds) and relaxation characteristics of nuclear spin at the single-atom scale open the way to a completely new world of devices in which quantum logic may be implemented. PMID:22895342

Vincent, Romain; Klyatskaya, Svetlana; Ruben, Mario; Wernsdorfer, Wolfgang; Balestro, Franck

2012-08-16

80

Probing individual environmental nuclear spins coupled to electronic spin defects with dynamical decoupling pulse sequences  

NASA Astrophysics Data System (ADS)

Solid-state spin qubits are promising candidates for quantum computation and quantum communication applications, for which long coherence times are a prerequisite. In the case of single Nitrogen-Vacancy (NV) centers, the coherence times are often limited by interactions with the surrounding nuclear environment. In this poster we present recent experimental results demonstrating the detection of individual nuclear spins weakly coupled to single electronic spin defects beyond the ``T2-star'' limit using dynamical decoupling pulse sequences. We take advantage of the coherent nature of the hyperfine interaction to probe the nuclear environment of individual NV centers, and to identify the nearby nuclear spins and determine their coupling strengths and relative positions to the NV. We observe coupling strengths ranging from 2 MHz down to 46 kHz, well below the limit imposed by ``T2-star,'' and observe multiple nuclei coupled to a single NV. We discuss potential applications of this technique in magnetometry and quantum information science.

Unterreithmeier, Quirin; Kolkowitz, Shimon; Bennett, Steven; Lukin, Mikhail

2012-06-01

81

Distinction of Nuclear Spin States with the Scanning Tunneling Microscope  

NASA Astrophysics Data System (ADS)

We demonstrate rotational excitation spectroscopy with the scanning tunneling microscope for physisorbed H2 and its isotopes HD and D2. The observed excitation energies are very close to the gas phase values and show the expected scaling with the moment of inertia. Since these energies are characteristic for the molecular nuclear spin states we are able to identify the para and ortho species of hydrogen and deuterium, respectively. We thereby demonstrate nuclear spin sensitivity with unprecedented spatial resolution.

Natterer, Fabian Donat; Patthey, François; Brune, Harald

2013-10-01

82

Towards understanding global variability in ocean carbon-13  

Microsoft Academic Search

We include a prognostic parameterization of carbon-13 into a global ocean-biogeochemistry model to investigate the spatiotemporal variability in ocean carbon-13 between 1860 and 2000. Carbon-13 was included in all 10 existing carbon pools, with dynamic fractionations occurring during photosynthesis, gas exchange and carbonate chemistry. We find that ocean distributions of ?13CDIC at any point in time are controlled by the

Alessandro Tagliabue; Laurent Bopp

2008-01-01

83

Nuclear spin qubits in a trapped-ion quantum computer  

SciTech Connect

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.

Feng, M. [State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Center for Cold Atom Physics, Chinese Academy of Sciences, Wuhan 430071 (China); Xu, Y. Y.; Zhou, F. [State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071 (China); Center for Cold Atom Physics, Chinese Academy of Sciences, Wuhan 430071 (China); Graduate School, Chinese Academy of Sciences, Beijing 100039 (China); Suter, D. [Fakultaet Physik, Technische Universitaet Dortmund, 44221 Dortmund (Germany)

2009-05-15

84

Nuclear spin relaxation induced by a mechanical resonator.  

PubMed

We report on measurements of the spin lifetime of nuclear spins strongly coupled to a micromechanical cantilever as used in magnetic resonance force microscopy. We find that the rotating-frame correlation time of the statistical nuclear polarization is set by the magnetomechanical noise originating from the thermal motion of the cantilever. Evidence is based on the effect of three parameters: (1) the magnetic field gradient (the coupling strength), (2) the Rabi frequency of the spins (the transition energy), and (3) the temperature of the low-frequency mechanical modes. Experimental results are compared to relaxation rates calculated from the spectral density of the magnetomechanical noise. PMID:18517996

Degen, C L; Poggio, M; Mamin, H J; Rugar, D

2008-04-01

85

An endohedral fullerene-based nuclear spin quantum computer  

NASA Astrophysics Data System (ADS)

We propose a new scalable quantum computer architecture based on endohedral fullerene molecules. Qubits are encoded in the nuclear spins of the endohedral atoms, which posses even longer coherence times than the electron spins which are used as the qubits in previous proposals. To address the individual qubits, we use the hyperfine interaction, which distinguishes two modes (active and passive) of the nuclear spin. Two-qubit quantum gates are effectively implemented by employing the electronic dipolar interaction between adjacent molecules. The electron spins also assist in the qubit initialization and readout. Our architecture should be significantly easier to implement than earlier proposals for spin-based quantum computers, such as the concept of Kane [B.E. Kane, Nature 393 (1998) 133].

Ju, Chenyong; Suter, Dieter; Du, Jiangfeng

2011-03-01

86

NMR spectroscopic studies on chalcogen compounds. 4. Carbon-13 isotope effect on selenium-77 and tellurium-125 nuclear shielding and its correlation with C-Se bond distances. Tellurium-123 isotope effect on tellurium-125 nuclear shielding  

SciTech Connect

A one-bond isotope effect of /sup 13/C on the nuclear shielding of /sup 77/Se and /sup 125/Te was observed for the first time. Thirty values for Se(II) and Se(IV) compounds containing sp/sup 3/-, sp/sup 2/-, and sp-hybridized carbon were measured, and a wide range of low frequency shifts was found between -0.012 and -1.099 ppM. A correlation was established between the isotope shift and the C-Se bond distance for CF/sub 3/- and CH/sub 3/-substituted selenium compounds. The isotope shift of the linear molecules SeCO, SeCS, and SeCSe is inversely dependent on the force constant of the C=Se bond. This is attributed to different vibrational amplitudes. The CSe bond order plays an important role for the isotope shift and appreciable substituent effects were observed. Five Te(II) and Te(IV) compounds were studied. The isotope shifts are larger than for the corresponding Se compounds, and the results can be qualitatively interpreted in analogy to those found for the selenium compounds. The isotope shift can be temperature dependent; this was shown, for example, on liquid samples of CF/sub 3/SeCN and SeCO. This behavior is explained by a substantial contribution of vibrationally excited states. Furthermore, an isotope effect of /sup 123/Te on the screening of /sup 125/Te (and vice versa) in CF/sub 3/TeTeCF/sub 3/ was detected, and the coupling constant /sup 1/J(/sup 125/Te-/sup 123/Te) was determined.

Gombler, W.

1982-12-01

87

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

88

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

89

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

90

Concerted two-dimensional NMR approaches to hydrogen-1, carbon-13, and nitrogen-15 resonance assignments in proteins  

SciTech Connect

When used in concert, one-bond carbon-carbon correlations, one-bond and multiple-bond proton-carbon correlations, and multiple-bond proton-nitrogen correlations, derived from two-dimensional (2D) NMR spectra of isotopically enriched proteins, provide a reliable method of assigning proton, carbon, and nitrogen resonances. In contrast to procedures that simply extend proton assignments to carbon or nitrogen resonances, this technique assigns proton, carbon, and nitrogen resonances coordinately on the basis of their integrated coupling networks. Redundant spin coupling pathways provide ways of resolving overlaps frequently encountered in homonuclear {sup 1}H 2D NMR spectra and facilitate the elucidation of complex proton spin systems. Carbon-carbon and proton-carbon couplings can be used to bridge the aromatic and aliphatic parts of proton spin systems; this avoids possible ambiguities that may result from the use of nuclear Overhauser effects to assign aromatic amino acid signals. The technique is illustrated for Anabaena 7120 flavodoxin and cytochrome c-553, both uniformly enriched with carbon-13 (26%) or nitrogen-15 (98%).

Stockman, B.J.; Reily, M.D.; Westler, W.M.; Ulrich, E.L.; Markley, J.L. (Univ. of Wisconsin, Madison (USA))

1989-01-10

91

Effects of inversion asymmetry on electron-nuclear spin coupling in semiconductor heterostructures: possible role of spin-orbit interactions.  

PubMed

We show that electron-nuclear spin coupling in semiconductor heterostructures is strongly modified by their potential inversion asymmetry. This is demonstrated in a GaAs quantum well, where we observe that the current-induced nuclear spin polarization at Landau-level filling factor nu=2/3 is completely suppressed when the quantum well is made largely asymmetric with gate voltages. Furthermore, we find that the nuclear spin relaxation rate is also modified by the potential asymmetry. These findings strongly suggest that even a very weak Rashba spin-orbit interaction can play a dominant role in determining the electron-nuclear spin coupling. PMID:15904087

Hashimoto, Katsushi; Muraki, Koji; Kumada, Norio; Saku, Tadashi; Hirayama, Yoshiro

2005-04-15

92

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.

93

Combustion resistance of the 129Xe hyperpolarized nuclear spin state.  

PubMed

Using a methane-xenon mixture for spin exchange optical pumping, MRI of combustion was enabled. The (129)Xe hyperpolarized nuclear spin state was found to sufficiently survive the complete passage through the harsh environment of the reaction zone. A velocity profile (V(z)(z)) of a flame was recorded to demonstrate the feasibility of MRI velocimetry of transport processes in combustors. PMID:23165418

Stupic, Karl F; Six, Joseph S; Olsen, Michael D; Pavlovskaya, Galina E; Meersmann, Thomas

2013-01-01

94

Imaging mesoscopic nuclear spin noise with a diamond magnetometer.  

PubMed

Magnetic resonance imaging 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. PMID:20886922

Meriles, Carlos A; Jiang, Liang; Goldstein, Garry; Hodges, Jonathan S; Maze, Jeronimo; Lukin, Mikhail D; Cappellaro, Paola

2010-09-28

95

Dipolar broadening of nuclear spin resonance under dynamical pumping  

NASA Astrophysics Data System (ADS)

We study the polarization dependence of the homogeneously broadened nuclear spin resonance in a crystal. We employ a combinatorial method to restrict the nuclear states to a fixed polarization and show that the center of the resonance is shifted linearly with the nuclear polarization by up to the zero polarization line width. The width shrinks from its maximum value at zero polarization to zero at full polarization. This suggests to use the line shape as a direct measure of nuclear polarization reached under dynamical pumping. In the limit of single quantum of excitation above the fully ferromagnetic state, we provide an explicit solution to the problem of nuclear spin dynamics which links a bound on the fastest decay rate to the observable width of the resonance line.

Tsyplyatyev, O.; Whittaker, D. M.

2012-03-01

96

Nuclear Tuning and Detuning of the Electron Spin Resonance in a Quantum Dot: Theoretical Consideration  

NASA Astrophysics Data System (ADS)

We study nuclear spin dynamics in a quantum dot close to the conditions of electron spin resonance. We show that at a small frequency mismatch, the nuclear field detunes the resonance. Remarkably, at larger frequency mismatch, its effect is opposite: The nuclear system is bistable, and in one of the stable states, the field accurately tunes the electron spin splitting to resonance. In this state, the nuclear field fluctuations are strongly suppressed, and nuclear spin relaxation is accelerated.

Danon, Jeroen; Nazarov, Yuli V.

2008-02-01

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

Quantum chaos and fluctuations in isolated nuclear-spin systems  

SciTech Connect

Using numerical simulations we investigate dynamical quantum chaos in isolated nuclear spin systems. We determine the structure of quantum states, investigate the validity of the Curie law for magnetic susceptibility and find the spectrum of magnetic noise. The spectrum is the same for positive and negative temperatures. The study is motivated by recent interest in condensed-matter experiments for searches of fundamental parity- and time-reversal-invariance violations. In these experiments nuclear spins are cooled down to microkelvin temperatures and are completely decoupled from their surroundings. A limitation on statistical sensitivity of the experiments arises from the magnetic noise.

Ludlow, J. A.; Sushkov, O. P. [School of Physics, University of New South Wales, Sydney 2052 (Australia)

2007-01-15

99

Quantum chaos and fluctuations in isolated nuclear-spin systems.  

PubMed

Using numerical simulations we investigate dynamical quantum chaos in isolated nuclear spin systems. We determine the structure of quantum states, investigate the validity of the Curie law for magnetic susceptibility and find the spectrum of magnetic noise. The spectrum is the same for positive and negative temperatures. The study is motivated by recent interest in condensed-matter experiments for searches of fundamental parity- and time-reversal-invariance violations. In these experiments nuclear spins are cooled down to microkelvin temperatures and are completely decoupled from their surroundings. A limitation on statistical sensitivity of the experiments arises from the magnetic noise. PMID:17358232

Ludlow, J A; Sushkov, O P

2007-01-01

100

Schematic model of nuclear spin excitations  

SciTech Connect

A simple model to estimate the strength of spin and nonspin collective states is presented. The model was inspired by early schematic models based on energy-weighted sum rules and is a useful tool for interpreting experimental data without the complexities of realistic microscopic calculations. The strength of collective states is calculated by assuming that a single collective state completely exhausts the energy-weighted sum rule. 19 refs.

Boucher, P.M.

1990-01-01

101

A METHOD FOR NUCLEAR SPIN STATISTICS IN MOLECULAR SPECTROSCOPY  

SciTech Connect

Using spin projection operator methods generating functions are developed for nuclear spin species. These operators also generate elegantly the irreducible representations spanned by a{sub 1}{sup b{sub 1}}, a{sub 2}{sup b{sub 2}} .... a{sub t}{sup b{sub t}} nuclear spin functions where a{sub i} is the number of possible spin states of the b{sub i} nuclei of the same kind in the molecule. From these generating functions the statistical weights of the rovibronic levels of any polyatomic molecule can be obtained easily. The method is illustrated with SF{sub 6}, C{sup 13}-Triphenylene and triphenylene with protons replaced by D. For C{sup 13}-Triphenylene there are 1073741824 nuclear spin functions from which we determine the statistical weights of the rovibronic levels A{sub 1}, A{sub 2}, E, A{sub 1}', A{sub 2}' and E' to be 178940928, 178973696, 357913600, 178940928, 178973696, and 357913600, respectively.

Balasubramanian, K.

1980-10-01

102

Creating nuclear spin entanglement using an optical degree of freedom  

SciTech Connect

Molecular nanostructures are promising building blocks for future quantum technologies, provided methods of harnessing their multiple degrees of freedom can be identified and implemented. Due to low decoherence rates, nuclear spins are considered ideal candidates for storing quantum information, while optical excitations can give rise to fast and controllable interactions for information processing. A recent paper [M. Schaffry et al., Phys. Rev. Lett. 104, 200501 (2010)] proposed a method for entangling two nuclear spins through their mutual coupling to a transient optically excited electron spin. Building on the same idea, we present here an extended and much more detailed theoretical framework, showing that this method is in fact applicable to a much wider class of molecular structures than previously discussed in the original proposal.

Schaffry, Marcus [Department of Materials, Oxford University, Oxford OX1 3PH (United Kingdom); Lovett, Brendon W. [Department of Materials, Oxford University, Oxford OX1 3PH (United Kingdom); SUPA, Department of Physics, Heriot Watt University, Edinburgh EH14 4AS (United Kingdom); Gauger, Erik M. [Department of Materials, Oxford University, Oxford OX1 3PH (United Kingdom); Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 (Singapore)

2011-09-15

103

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

PubMed

In order to establish an applicable system for advanced quantum information processing based on the interaction between light and atoms, we have demonstrated a quantum nondemolition measurement with a collective spin of cold ytterbium atoms (171Yb), 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. We used very short pulses with a width of 100 ns, and as a result the interaction time became much shorter than the decoherence time, which is important for multistep quantum information processing. PMID:19257352

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

2009-01-23

104

Spin Squeezing of a Cold Atomic Ensemble with the Nuclear Spin of One-Half  

NASA Astrophysics Data System (ADS)

In order to establish an applicable system for advanced quantum information processing based on the interaction between light and atoms, we have demonstrated a quantum nondemolition measurement with a collective spin of cold ytterbium atoms (Yb171), and have observed 1.8-1.5+2.4dB spin squeezing. Since Yb171 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. We used very short pulses with a width of 100 ns, and as a result the interaction time became much shorter than the decoherence time, which is important for multistep quantum information processing.

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

2009-01-01

105

Carbon-13 Labeling Used to Probe Cure and Degradation Reactions of High- Temperature Polymers  

NASA Technical Reports Server (NTRS)

High-temperature, crosslinked polyimides are typically insoluble, intractible materials. Consequently, in these systems it has been difficult to follow high-temperature curing or long-term degradation reactions on a molecular level. Selective labeling of the polymers with carbon-13, coupled with solid nuclear magnetic resonance spectrometry (NMR), enables these reactions to be followed. We successfully employed this technique to provide insight into both curing and degradation reactions of PMR-15, a polymer matrix resin used extensively in aircraft engine applications.

Meador, Mary Ann B.; Johnston, J. Christopher

1998-01-01

106

Nuclear spin polarization induced by ultrashort laser pulses  

SciTech Connect

We theoretically show that the use of the hyperfine interaction together with a static electric field leads to ultrafast nuclear spin polarization. The idea is specifically applied to the isotopes of alkaline-earth atoms such as 27Mg (I = 1/2) and 37 Ca (I = 3/2), and we find that spin polarization as high as 88 % and 62 %, respectively, can be attained within the time scale of a few to tens of ns. This technique can be very effective not only for stable nuclei but also unstable nuclei.

Nakajima, Takashi [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

2007-06-13

107

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

108

Investigation of the Possibility of Using Nuclear Magnetic Spin Alignment  

NASA Technical Reports Server (NTRS)

The goal of the program to investigate a "Gasdynamic fusion propulsion system for space exploration" is to develop a fusion propulsion system for a manned mission to the planet mars. A study using Deuterium and Tritium atoms are currently in progress. When these atoms under-go fusion, the resulting neutrons and alpha particles are emitted in random directions (isotropically). The probable direction of emission is equal for all directions, thus resulting in wasted energy, massive shielding and cooling requirements, and serious problems with the physics of achieving fusion. If the nuclear magnetic spin moments of the deuterium and tritium nuclei could be precisely aligned at the moment of fusion, the stream of emitted neutrons could be directed out the rear of the spacecraft for thrust and the alpha particles directed forward into an electromagnet ot produce electricity to continue operating the fusion engine. The following supporting topics are discussed: nuclear magnetic moments and spin precession in magnetic field, nuclear spin quantum mechanics, kinematics of nuclear reactions, and angular distribution of particles.

Dent, William V., Jr.

1998-01-01

109

Selective polarization of nuclear spins in a wire-like quantum Hall system  

SciTech Connect

Nuclear spins are polarized selectively in a mesoscopic wire-like quantum Hall system by using the fractional quantum Hall system at Landau level filling factor nu = 2/3. The nuclear spin polarized region is limited by setting the filling factor in the wire to 2/3, while leaving the filling factor in the bulk away from 2/3. The longitudinal relaxation rate of selectively polarized nuclear spins probes electron spin properties in the wire.

Kobayashi, Takashi; Sasaki, Satoshi [NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa 243-0198 (Japan); Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Kumada, Norio; Ota, Takeshi [NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa 243-0198 (Japan); Hirayama, Yoshiro [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); ERATO-JST Nuclear Spin Electronics Project, 468-15 Aramaki Aza-Aoba, Aoba-ku, Sendai 980-0845 (Japan)

2010-01-04

110

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

111

Interpretation of vicinal spin-spin coupling constants in ethane via the current-density induced by nuclear magnetic dipoles  

NASA Astrophysics Data System (ADS)

The indirect nuclear spin-spin coupling is rationalized via electronic current densities induced by nuclear magnetic dipoles. The coupling-density tensor, a function in real space obtained from the current density, visualizes fundamental aspects of the coupling mechanism. Magnetic group theory and current-density plots are used for discussing the Dirac-van Vleck vector model in the contact interaction. The Biot-Savart law is useful for understanding the sign of the contributions to the magnetic field at a nucleus from a given point of the current field. These tools are used to analyze the vicinal spin-spin coupling in ethane.

Soncini, A.; Lazzeretti, P.

2005-06-01

112

Hanle effect in (In,Ga)As quantum dots: Role of nuclear spin fluctuations  

NASA Astrophysics Data System (ADS)

The role of nuclear spin fluctuations in the dynamic polarization of nuclear spins by electrons is investigated in (In,Ga)As/GaAs quantum dots. The photoluminescence polarization under circularly polarized optical pumping in transverse magnetic fields (Hanle effect) is studied. A weak additional magnetic field parallel to the optical axis is used to control the efficiency of nuclear spin cooling and the sign of nuclear spin temperature. The shape of the Hanle curve is drastically modified when changing this control field, as observed earlier in bulk semiconductors and quantum wells. However, the standard nuclear spin cooling theory, operating with the mean nuclear magnetic field (Overhauser field), fails to describe the experimental Hanle curves in a certain range of control fields. This controversy is resolved by taking into account the nuclear spin fluctuations owed to the finite number of nuclei in the quantum dot. We propose a model considering cooling of the nuclear spin system by electron spins experiencing fast vector precession in the random Overhauser fields of nuclear spin fluctuations. The model allows us to accurately describe the measured Hanle curves and to evaluate the parameters of the electron-nuclear spin system of the studied quantum dots.

Kuznetsova, M. S.; Flisinski, K.; Gerlovin, I. Ya.; Ignatiev, I. V.; Kavokin, K. V.; Verbin, S. Yu.; Yakovlev, D. R.; Reuter, D.; Wieck, A. D.; Bayer, M.

2013-06-01

113

Nuclear Magnetic Relaxation in METHYLENE-13 and METHYL-13 Coupled Spin Systems and Variable Angle Spinning Lineshape Analysis for Quadrupolar Nuclei with Half Integer Spins  

NASA Astrophysics Data System (ADS)

The carbon-13 multiplet spin-lattice relaxation in ^{13}CH_2 and ^{13}CH _3^in systems is studied in detail by various nonselective and selective pulse techniques. Simultaneous fitting of the resulting relaxation curves with various rates and initial conditions allows for the extraction of both auto- and cross-correlated dipolar spectral densities which can provide detailed information on the molecular anisotropic reorientation. In addition, the ^ {13}CH_3 coupled spin relaxation can characterize the methyl internal rotation dynamics. The cross-correlation between the dipolar and chemical shift anisotropy (CSA) interactions is found to be appreciable. Dipolar-CSA cross-correlated spectral densities introduce relaxation pathways that couple together magnetization modes with different spin inversion symmetries. Consideration of the dipolar-CSA cross-correlated spectral densities not only improves the accuracy of the measurement of dipolar spectral densities but also allows for the determination of the dipolar-CSA cross-correlated spectral densities themselves, providing a new measure of the anisotropy of the shielding tensor. NMR spectroscopy of quadrupolar nuclei in solids generally yields broad lines even when magic angle spinning is applied. Broadening of the central transition of quadrupolar nuclei with half integer spins is caused by the anisotropy of the second order quadrupolar interaction. A straightforward approach is presented that combines average Hamiltonian theory and a numerical solution of a classical banded matrix describing the equation of motion for a quadrupolar nucleus under variable angle sample spinning conditions. At either of two fourth rank magic angles, a simple three parameter lineshape is obtained, and the three breakpoints are related directly to the quadrupolar constant and its asymmetry parameter. The banded matrix method used in the simulations is computationally much more efficient than the standard method using Bessel functions.

Zheng, Zhiwen

1992-01-01

114

Persistent Narrowing of Nuclear-Spin Fluctuations in InAs Quantum Dots Using Laser Excitation  

NASA Astrophysics Data System (ADS)

We demonstrate the suppression of nuclear-spin fluctuations in an InAs quantum dot and measure the timescales of the spin narrowing effect. By initializing for tens of milliseconds with two continuous wave diode lasers, fluctuations of the nuclear spins are suppressed via the hole-assisted dynamic nuclear polarization feedback mechanism. The fluctuation narrowed state persists in the dark (absent light illumination) for well over 1 s even in the presence of a varying electron charge and spin polarization. Enhancement of the electron spin coherence time (T2*) is directly measured using coherent dark state spectroscopy. By separating the calming of the nuclear spins in time from the spin qubit operations, this method is much simpler than the spin echo coherence recovery or dynamic decoupling schemes.

Sun, Bo; Chow, Colin Ming Earn; Steel, Duncan G.; Bracker, Allan S.; Gammon, Daniel; Sham, L. J.

2012-05-01

115

Solid effect in magic angle spinning dynamic nuclear polarization.  

PubMed

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 (1)H 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 (1)H 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. PMID:22894339

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

2012-08-01

116

Faraday rotation with a single-nuclear-spin qubit in a high-finesse optical cavity  

SciTech Connect

When an off-resonant light field is coupled with atomic spins, its polarization can rotate depending on the direction of the spins via Faraday rotation, which has been used for monitoring and controlling the atomic spins. We observed Faraday rotation by an angle of more than 10 deg for a single nuclear spin of 1/2 of a {sup 171}Yb atom in a high-finesse optical cavity. By employing the coupling between the single nuclear spin and a photon, we have also demonstrated that the spin can be projected or weakly measured through the projection of the transmitted single ancillary photon.

Takei, Nobuyuki; Takeuchi, Makoto; Zhang, Peng [ERATO Macroscopic Quantum Control Project, Japan Science and Technology Agency, 2-11-16 Yayoi, Bunkyo-Ku, Tokyo 113-8656 (Japan); Eto, Yujiro; Noguchi, Atsushi; Kozuma, Mikio [ERATO Macroscopic Quantum Control Project, Japan Science and Technology Agency, 2-11-16 Yayoi, Bunkyo-Ku, Tokyo 113-8656 (Japan); Department of Physics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8550 (Japan); Ueda, Masahito [ERATO Macroscopic Quantum Control Project, Japan Science and Technology Agency, 2-11-16 Yayoi, Bunkyo-Ku, Tokyo 113-8656 (Japan); Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2010-04-15

117

Nuclear Hydrogen for Peak Electricity Production and Spinning Reserve  

SciTech Connect

Nuclear energy can be used to produce hydrogen. The key strategic question is this: ''What are the early markets for nuclear hydrogen?'' The answer determines (1) whether there are incentives to implement nuclear hydrogen technology today or whether the development of such a technology could be delayed by decades until a hydrogen economy has evolved, (2) the industrial partners required to develop such a technology, and (3) the technological requirements for the hydrogen production system (rate of production, steady-state or variable production, hydrogen purity, etc.). Understanding ''early'' markets for any new product is difficult because the customer may not even recognize that the product could exist. This study is an initial examination of how nuclear hydrogen could be used in two interconnected early markets: the production of electricity for peak and intermediate electrical loads and spinning reserve for the electrical grid. The study is intended to provide an initial description that can then be used to consult with potential customers (utilities, the Electric Power Research Institute, etc.) to better determine the potential real-world viability of this early market for nuclear hydrogen and provide the starting point for a more definitive assessment of the concept. If this set of applications is economically viable, it offers several unique advantages: (1) the market is approximately equivalent in size to the existing nuclear electric enterprise in the United States, (2) the entire market is within the utility industry and does not require development of an external market for hydrogen or a significant hydrogen infrastructure beyond the utility site, (3) the technology and scale match those of nuclear hydrogen production, (4) the market exists today, and (5) the market is sufficient in size to justify development of nuclear hydrogen production techniques independent of the development of any other market for hydrogen. These characteristics make it an ideal early market for nuclear hydrogen.

Forsberg, C.W.

2005-01-20

118

Comparison of different methods for calculating the paramagnetic relaxation enhancement of nuclear spins as a function of the magnetic field  

Microsoft Academic Search

The enhancement of the spin-lattice relaxation rate for nuclear spins in a ligand bound to a paramagnetic metal ion [known as the paramagnetic relaxation enhancement (PRE)] arises primarily through the dipole-dipole (DD) interaction between the nuclear spins and the electron spins. In solution, the DD interaction is modulated mostly by reorientation of the nuclear spin-electron spin axis and by electron

Elie Belorizky; Pascal H. Fries; Lothar Helm; Jozef Kowalewski; Danuta Kruk; Robert R. Sharp; Per-Olof Westlund

2008-01-01

119

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

120

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

PubMed

The water-endofullerene H2O@C60 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 H2O 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 H2O molecules is catalysed by (13)C nuclei present in the cages. PMID:24852537

Mamone, Salvatore; Concistrè, Maria; Carignani, Elisa; Meier, Benno; Krachmalnicoff, Andrea; Johannessen, Ole G; Lei, Xuegong; Li, Yongjun; Denning, Mark; Carravetta, Marina; Goh, Kelvin; Horsewill, Anthony J; Whitby, Richard J; Levitt, Malcolm H

2014-05-21

121

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

NASA Astrophysics Data System (ADS)

The water-endofullerene H2O@C60 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 H2O 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 H2O molecules is catalysed by 13C nuclei present in the cages.

Mamone, Salvatore; Concistrè, Maria; Carignani, Elisa; Meier, Benno; Krachmalnicoff, Andrea; Johannessen, Ole G.; Lei, Xuegong; Li, Yongjun; Denning, Mark; Carravetta, Marina; Goh, Kelvin; Horsewill, Anthony J.; Whitby, Richard J.; Levitt, Malcolm H.

2014-05-01

122

Estimation of optical chemical shift in nuclear spin optical rotation  

NASA Astrophysics Data System (ADS)

A recently proposed optical chemical shift in nuclear spin optical rotation (NSOR) is studied by theoretical comparison of NSOR magnitude between chemically non-equivalent or different element nuclei in the same molecule. Theoretical expressions of the ratio R between their NSOR magnitudes are derived by using a known semi-empirical formula of NSOR. Taking methanol, tri-ethyl-phosphite and 2-methyl-benzothiazole as examples, the ratios R are calculated and the results approximately agree with the experiments. Based on those, the important influence factors on R and chemical distinction by NSOR are discussed.

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

2014-05-01

123

Spin Instability in Nuclear Matter and the Skyrme Interaction  

NASA Astrophysics Data System (ADS)

In the present work the problem of spin instability of nuclear matter with the Skyrme interaction is analyzed. The three-body part of the interaction is replaced by using a density dependent potential which is a modification to that given previously by Dabrowski. The symmetry energies are calculated and their rearrangement corrections. Good agreement is obtained with previous calculations.Translated AbstractSpininstabilität in Kernmaterie und Skyrme-WechselwirkungDie vorliegende Arbeit analysiert die Spininstabilität von Kernmaterie mit Skyrme-Wechselwirkung. Der Dreikörperanteil der Wechselwirkung ist durch ein dichteabhängiges Potential ersetzt. Die Symmetrieenergien und ihre Umordnungskorrekturen werden berechnet. Sie stimmen gut mit vorhergehenden Rechnungen überein.

Mansour, H. M. M.

124

Efficient room-temperature nuclear spin hyperpolarization of a defect atom in a semiconductor  

NASA Astrophysics Data System (ADS)

Nuclear spin hyperpolarization is essential to future solid-state quantum computation using nuclear spin qubits and in highly sensitive magnetic resonance imaging. Though efficient dynamic nuclear polarization in semiconductors has been demonstrated at low temperatures for decades, its realization at room temperature is largely lacking. Here we demonstrate that a combined effect of efficient spin-dependent recombination and hyperfine coupling can facilitate strong dynamic nuclear polarization of a defect atom in a semiconductor at room temperature. We provide direct evidence that a sizeable nuclear field (~150?Gauss) and nuclear spin polarization (~15%) sensed by conduction electrons in GaNAs originates from dynamic nuclear polarization of a Ga interstitial defect. We further show that the dynamic nuclear polarization process is remarkably fast and is completed in <5??s at room temperature. The proposed new concept could pave a way to overcome a major obstacle in achieving strong dynamic nuclear polarization at room temperature, desirable for practical device applications.

Puttisong, Y.; Wang, X. J.; Buyanova, I. A.; Geelhaar, L.; Riechert, H.; Ptak, A. J.; Tu, C. W.; Chen, W. M.

2013-04-01

125

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

126

Quantum Computing Using Pulse-Based Electron-Nuclear Double Resonance (endor):. Molecular Spin-Qubits  

NASA Astrophysics Data System (ADS)

Electrons with the spin quantum number 1/2, as physical qubits, have naturally been anticipated for implementing quantum computing and information processing (QC/QIP). Recently, electron spin-qubit systems in organic molecular frames have emerged as a hybrid spin-qubit system along with a nuclear spin-1/2 qubit. Among promising candidates for QC/QIP from the materials science side, the reasons for why electron spin-qubits such as molecular spin systems, i.e., unpaired electron spins in molecular frames, have potentialities for serving for QC/QIP will be given in the lecture (Chapter), emphasizing what their advantages or disadvantages are entertained and what technical and intrinsic issues should be dealt with for the implementation of molecular-spin quantum computers in terms of currently available spin manipulation technology such as pulse-based electron-nuclear double resonance (pulsed or pulse ENDOR) devoted to QC/QIP. Firstly, a general introduction and introductory remarks to pulsed ENDOR spectroscopy as electron-nuclear spin manipulation technology is given. Super dense coding (SDC) experiments by the use of pulsed ENDOR are also introduced to understand differentiating QC ENDOR from QC NMR based on modern nuclear spin technology. Direct observation of the spinor inherent in an electron spin, detected for the first time, will be shown in connection with the entanglement of an electron-nuclear hybrid system. Novel microwave spin manipulation technology enabling us to deal with genuine electron-electron spin-qubit systems in the molecular frame will be introduced, illustrating, from the synthetic strategy of matter spin-qubits, a key-role of the molecular design of g-tensor/hyperfine-(A-)tensor molecular engineering for QC/QIP. Finally, important technological achievements of recently-emerging CD ELDOR (Coherent-Dual ELectron-electron DOuble Resonance) spin technology enabling us to manipulate electron spin-qubits are described.

Sato, Kazuo; Nakazawa, Shigeki; Rahimi, Robabeh D.; Nishida, Shinsuke; Ise, Tomoaki; Shimoi, Daisuke; Toyota, Kazuo; Morita, Yasushi; Kitagawa, Masahiro; Carl, Parick; Höfner, Peter; Takui, Takeji

2009-06-01

127

Quantum limit for nuclear spin polarization in semiconductor quantum dots  

NASA Astrophysics Data System (ADS)

A recent experiment [E. A. Chekhovich et al., Phys. Rev. Lett. 104, 066804 (2010), 10.1103/PhysRevLett.104.066804] has demonstrated that high nuclear spin polarization can be achieved in self-assembled quantum dots by exploiting an optically forbidden transition between a heavy hole and a trion state. However, a fully polarized state is not achieved as expected from a classical rate equation. Here, we theoretically investigate this problem with the help of a quantum master equation and we demonstrate that a fully polarized state cannot be achieved due to formation of a nuclear dark state. Moreover, we show that the maximal degree of polarization depends on structural properties of the quantum dot.

Hildmann, Julia; Kavousanaki, Eleftheria; Burkard, Guido; Ribeiro, Hugo

2014-05-01

128

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

129

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

130

Spin–orbit corrections to the indirect nuclear spin–spin coupling constants in XH4 (X=C, Si, Ge, and Sn)  

Microsoft Academic Search

Summary.  ?Using the quadratic response function at the ab initio SCF level of approximation we have calculated the relativistic corrections from the spin–orbit Hamiltonian, H\\u000a SO, to the indirect nuclear spin–spin coupling constants of XH4 (X=C, Si, Ge, and Sn). We find that the spin–orbit contributions to J\\u000a X–H are small, amounting only to about 1% for J\\u000a Sn–H. For the

Sheela Kirpekar; Hans Jørgen Aagaard Jensen; Jens Oddershede

1997-01-01

131

Spin-orbit corrections to the indirect nuclear spin-spin coupling constants in XH 4 (X = C, Si, Ge, and Sn)  

Microsoft Academic Search

Summary  Using the quadratic response function at theab initio SCF level of approximation we have calculated the relativistic corrections from the spin-orbit Hamiltonian,H\\u000a SO, to the indirect nuclear spin-spin coupling constants of XH4 (X = C, Si, Ge, and Sn). We find that the spin-orbit contributions toJ\\u000a X-H are small, amounting only to about 1% forJ\\u000a Sn-H. For the geminal H-H

Sheela Kirpekar; Hans Jørgen Aagaard Jensen; Jens Oddershede

1997-01-01

132

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

133

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

134

Quantum Computation Using the 13C Nuclear Spins Near the Single NV Defect Center in Diamond  

NASA Astrophysics Data System (ADS)

We discuss the possibility of realizing quantum computation on the basis of a cluster of single interacting nuclear spins in solids. This idea seems to be feasible because of the combination of two techniques—Single Molecule Spectroscopy and Optically Detected Electron Nuclear Double Resonance. Compared to the well-known bulk Nuclear Magnetic Resonance (NMR), the proposed method of quantum computation has the advantage that quantum computation is performed with pure spin states and the quantum processor is more easily scalable. At the same time, the advantages of NMR quantum computation are kept: long coherence time and easy construction of quantum gates. As a specific system to implement the above idea, we discuss the 13C-nuclear spins in the nearest vicinity of a single nitrogen-vacancy (NV) defect center in diamond, which can be optically detected using the technique of scanning confocal microscopy. Owing to the hyperfine coupling of the ground state electron paramagnetic spin S=1 of the center to 13C nuclear spins in a diamond lattice, the states of nuclear spins in the vicinity of the defect-center can be addressed individually. Preliminary consideration shows that it should be possible to address up to 12 individual 13C nuclear spins. The dephasing time of the nuclear spin states at low temperatures allows realization up to 105 gates.

Wrachtrup, J.; Kilin, S. Ya.; Nizovtsev, A. P.

2001-09-01

135

MASS SPECTROMETRIC QUANTIFICATION OF POLYCHLORINATED BIPHENYL CONGENERS USING MULTIPLE CARBON-13 INTERNAL STANDARDS  

EPA Science Inventory

Multiple carbon-13 internal standards improve the precision and accuracy of the mass spectrometric analysis of polychlorinatedbiphenyl (PCB) congeners compared to analyses using a single carbon-13 internal standard. The mean percentage error in PCB congener analysis on the microg...

136

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.

2006-06-01

137

A co-magnetometer-based nuclear spin gyroscope  

NASA Astrophysics Data System (ADS)

We describe a new atomic gyroscope based on an alkali metal--noble gas co-magnetometer. Unlike atomic and laser gyroscopes based on the Sagnac effect, nuclear spin gyroscopes do not require a large enclosed area and can be made quite compact. A high density alkali-metal magnetometer operating in a spin-exchange relaxation free (SERF) regime is used to polarize the noble gas atoms and detect their gyroscopic precession. In this arrangement it is also possible to cancel the response to the magnetic fields as well as their gradients and transients between the two atomic species, giving a clean signal proportional to the rotation. Using a K--^3He co-magnetometer we demonstrated rotation sensitivity of 2 x10-7 rad/sec/Hz^1/2. The rotation signal can be increased by an order of magnitude using Ne-21 atoms which have a smaller magnetic moment, while the fundamental limit on the gyroscope sensitivity is about 10-10 rad/sec/ Hz^1/2 for a 10 cm^3 measurement cell. We will also present data on the long-term stability of the gyroscope obtained during a search for Lorentz violation using the K--^3He co-magnetometer.

Kornack, Thomas

2005-05-01

138

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

139

Phase-Sensitive Probes of Nuclear Polarization in Spin-Blockaded Quantum Dots  

NASA Astrophysics Data System (ADS)

Semiconducting quantum dots provide a platform for investigating the quantum many-body dynamics of coupled electron and nuclear spins. The phenomenon of spin blockade, wherein the Pauli exclusion principle requires electrons to flip their spins in order to pass through the system [1], is an invaluable tool in this pursuit. We describe a new regime of coupled electron and nuclear spin dynamics in spin-blockaded quantum dots where the hyperfine coupling to nuclear spins competes with a purely electronic spin-flip mechanism, such as the spin-orbit interaction or coupling to an inhomogeneous Zeeman field [M. S. Rudner et al., arXiv:0909.0060]. We show that the long-lived coherence of the nuclear spin bath plays a crucial role and leads to a range of new surprising phenomena. In particular, a purely electrical detection of coherent nuclear precession can be realized. Recent results of Foletti et al. [arXiv:0801.3613] suggest that this interesting new regime is now within experimental reach. [1] K. Ono et al. Science 297, 1313 (2002).

Rudner, Mark; Neder, Izhar; Levitov, Leonid; Halperin, Bertrand

2010-03-01

140

Nuclear-spin-dependent coherent population trapping of single nitrogen-vacancy centers in diamond  

NASA Astrophysics Data System (ADS)

Coherent population trapping (CPT) provides a highly sensitive means for probing the energy-level structure of an atomic system. For a nitrogen-vacancy center in diamond, the CPT offers an alternative to the standard optically detected magnetic resonance method for measuring the hyperfine structure of the electronic ground states. We show that the nuclear-spin-dependent CPT measures directly the hyperfine splitting of these states due to the 14N nuclear spin. The CPT spectral response obtained in the presence of a strong microwave field, resonant or nearly resonant with a ground-state spin transition, maps out the dynamic Stark splitting induced by the coherent spin excitation.

Golter, D. Andrew; Dinyari, Khodadad N.; Wang, Hailin

2013-03-01

141

Distal and proximal ligand interactions in heme proteins: correlations between C-O and Fe-C vibrational frequencies, oxygen-17 and carbon-13 nuclear magnetic resonance chemical shifts, and oxygen-17 nuclear quadrupole coupling constants in C17O- and 13CO-labeled species.  

PubMed

We have obtained the oxygen-17 nuclear magnetic resonance (NMR) spectra of a variety of C17O-labeled heme proteins, including sperm whale (Physeter catodon) myoglobin, two synthetic sperm whale myoglobin mutants (His E7----Val E7; His E7----Phe E7), adult human hemoglobin, rabbit (Oryctolagus cuniculus) hemoglobin, horseradish (Cochlearia armoracia) peroxidase (E.C. 1.11.1.7) isoenzymes A and C, and Caldariomyces fumago chloroperoxidase (E.C. 1.11.1.10), in some cases as a function of pH, and have determined their isotropic 17O NMR chemical shifts, delta i, and spin-lattice relaxation times, T1. We have also obtained similar results on a picket fence prophyrin, [5,10,15,20-tetrakis(alpha, alpha, alpha, alpha, alpha-pivalamidophenyl)porphyrinato]iron(II) (1-MeIm)CO, both in solution and in the solid state. Our results show an excellent correlation between the infrared C-O vibrational frequencies, v(C-O), and delta i, between v(C-O) and the 17O nuclear quadrupole coupling constant (e2qQ/h, derived from T1), and as expected between e2qQ/h and delta i. Taken together with the work of others on the 13C NMR of 13CO-labeled proteins, where we find an excellent correlation between delta i(13C) and v(Fe-C), our results suggest that IR and NMR measurements reflect the same interaction, which is thought to be primarily the degree of pi-back-bonding from Fe d to CO pi* orbitals, as outlined previously [Li, X.-Y., & Spiro, T.G. (1988) J. Am. Chem. Soc. 110, 6024]. The modulation of this interaction by the local charge field of the distal heme residue (histidine, glutamine, arginine, and possibly lysine) in a variety of species and mutants, as reflected in the NMR and IR measurements, is discussed, as is the effect of cysteine as the proximal heme ligand. PMID:2001365

Park, K D; Guo, K M; Adebodun, F; Chiu, M L; Sligar, S G; Oldfield, E

1991-03-01

142

Fast control of nuclear spin polarization in an optically pumped single quantum dot  

NASA Astrophysics Data System (ADS)

Highly polarized nuclear spins within a semiconductor quantum dot induce effective magnetic (Overhauser) fields of up to several Tesla acting on the electron spin, or up to a few hundred mT for the hole spin. Recently this has been recognized as a resource for intrinsic control of quantum-dot-based spin quantum bits. However, only static long-lived Overhauser fields could be used. Here we demonstrate fast redirection on the microsecond timescale of Overhauser fields on the order of 0.5 T experienced by a single electron spin in an optically pumped GaAs quantum dot. This has been achieved using coherent control of an ensemble of 105 optically polarized nuclear spins by sequences of short radiofrequency pulses. These results open the way to a new class of experiments using radiofrequency techniques to achieve highly correlated nuclear spins in quantum dots, such as adiabatic demagnetization in the rotating frame leading to sub-?K nuclear spin temperatures, rapid adiabatic passage, and spin squeezing.

Makhonin, M. N.; Kavokin, K. V.; Senellart, P.; Lemaître, A.; Ramsay, A. J.; Skolnick, M. S.; Tartakovskii, A. I.

2011-11-01

143

Optical manipulation of nuclear spin by a two-dimensional electron gas.  

PubMed

Conduction electrons are used to optically polarize, detect, and manipulate nuclear spin in a (110) GaAs quantum well. Using optical Larmor magnetometry, we find that nuclear spin can be polarized along or against the applied magnetic field, depending on field polarity and tilting of the sample with respect to the optical pump beam. Periodic optical excitation of the quantum-confined electron spin reveals a complete spectrum of optically induced and quadrupolar-split nuclear resonances, as well as evidence for Deltam = 2 transitions. PMID:11290009

Salis, G; Fuchs, D T; Kikkawa, J M; Awschalom, D D; Ohno, Y; Ohno, H

2001-03-19

144

Voltage control of electron-nuclear spin correlation time in a single quantum dot  

NASA Astrophysics Data System (ADS)

We demonstrate bias control of the efficiency of the hyperfine coupling between a single electron in an InAs quantum dot and the surrounding nuclear spins monitored through the positively charged exciton X+ emission. In applied longitudinal magnetic fields, we vary simultaneously the correlation time of the hyperfine interaction and the nuclear spin relaxation time and thereby the amplitude of the achieved dynamic nuclear polarization under optical pumping conditions. In applied transverse magnetic fields, a change in the applied bias allows a switch from the anomalous Hanle effect to the standard electron spin depolarization curves.

Nilsson, J.; Bouet, L.; Bennett, A. J.; Amand, T.; Stevenson, R. M.; Farrer, I.; Ritchie, D. A.; Kunz, S.; Marie, X.; Shields, A. J.; Urbaszek, B.

2013-08-01

145

Fast nuclear spin conversion in water clusters and ices: a matrix isolation study.  

PubMed

Single water molecules have been isolated in solid Ar matrices at 4 K and studied by rovibrational spectroscopy using FTIR in the regions of the ?(1), ?(2), and ?(3) modes. Upon nuclear spin conversion at 4 K, essentially pure para-H(2)O was prepared, followed by subsequent fast annealing generating ice particles. FTIR studies of the vapor above the condensed water upon annealing to T ? 250 K indicate fast reconversion of nuclear spin to equilibrium conditions. Our results indicate that nuclear spin conversion is fast in water dimers and larger clusters, which preclude preparation of concentrated samples of para-H(2)O, such as in ice or vapor. PMID:21671631

Sliter, Russell; Gish, Melissa; Vilesov, Andrey F

2011-09-01

146

Coherent Storage of Photoexcited Triplet States Using Si29 Nuclear Spins in Silicon  

NASA Astrophysics Data System (ADS)

Pulsed electron paramagnetic resonance spectroscopy of the photoexcited, metastable triplet state of the oxygen-vacancy center in silicon reveals that the lifetime of the ms=±1 sublevels differs significantly from that of the ms=0 state. We exploit this significant difference in decay rates to the ground singlet state to achieve nearly ˜100% electron-spin polarization within the triplet. We further demonstrate the transfer of a coherent state of the triplet electron spin to, and from, a hyperfine-coupled, nearest-neighbor Si29 nuclear spin. We measure the coherence time of the Si29 nuclear spin employed in this operation and find it to be unaffected by the presence of the triplet electron spin and equal to the bulk value measured by nuclear magnetic resonance.

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

2012-03-01

147

Shell Structure at High Spin and the Influence on Nuclear Shapes.  

National Technical Information Service (NTIS)

Nuclear structure at high spin is influenced by a combination of liquid-drop and shell-structure effects. For N < 86 both contribute towards the occurrence along the yrast line of high-spin oblate aligned-particle configurations. Shell effects are mainly ...

T. L. Khoo P. Chowdhury I. Ahmad

1982-01-01

148

Nuclear Spin Relaxation Study of the Electronic Structure of Lead Telluride.  

National Technical Information Service (NTIS)

Measurements of the nuclear spin-lattice relaxation time (T1), the free induction decay time (T2*), and the spin echo decay time (T2) are reported for 207Pb in n- and p-type PbTe, for 105-295K. The measurements are related to a parameterized (k dot pi) no...

C. R. Hewes M. N. Alexander P. L. Sagalyn S. D. Senturia

1972-01-01

149

General theory of feedback control of a nuclear spin ensemble in quantum dots  

NASA Astrophysics Data System (ADS)

We present a microscopic theory of the nonequilibrium nuclear spin dynamics driven by the electron and/or hole under continuous-wave pumping in a quantum dot. We show the correlated dynamics of the nuclear spin ensemble and the electron and/or hole under optical excitation as a quantum feedback loop and investigate the dynamics of the many nuclear spins as a nonlinear collective motion. This gives rise to three observable effects: (i) hysteresis, (ii) locking (avoidance) of the pump absorption strength to (from) the natural resonance, and (iii) suppression (amplification) of the fluctuation of weakly polarized nuclear spins, leading to prolonged (shortened) electron-spin coherence time. A single nonlinear feedback function is constructed which determines the different outcomes of the three effects listed above depending on the feedback being negative or positive. The general theory also helps to put in perspective the wide range of existing theories on the problem of a single electron spin in a nuclear spin bath.

Yang, Wen; Sham, L. J.

2013-12-01

150

Nuclear spin selection rules in chemical reactions by angular momentum algebra  

NASA Astrophysics Data System (ADS)

The detailed selection rules for reactive collisions reported by Quack using molecular symmetry group are derived by using angular momentum algebra. Instead of the representations of the permutation-inversion 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 straightforward derivation of Quack's results and further extension of the calculation for separating elementary reactions and application to higher proton systems.

Oka, Takeshi

2004-12-01

151

Steady-State Entanglement in the Nuclear Spin Dynamics of a Double Quantum Dot  

NASA Astrophysics Data System (ADS)

We propose a scheme for the deterministic generation of steady-state entanglement between the two nuclear spin ensembles in an electrically defined double quantum dot. Due to quantum interference in the collective coupling to the electronic degrees of freedom, the nuclear system is actively driven into a two-mode squeezed-like target state. The entanglement build-up is accompanied by a self-polarization of the nuclear spins towards large Overhauser field gradients. Moreover, the feedback between the electronic and nuclear dynamics leads to multi-stability and criticality in the steady-state solutions.

Schuetz, M. J. A.; Kessler, E. M.; Vandersypen, L. M. K.; Cirac, J. I.; Giedke, G.

2013-12-01

152

Pulsed-field magnetization, electron spin resonance, and nuclear spin-lattice relaxation in the {Cu3} spin triangle  

NASA Astrophysics Data System (ADS)

We report on pulsed-field magnetization, Q -band electron spin resonance (ESR), and Na23 NMR measurements of the S=1/2 spin triangle clusters Na9[Cu3Na3(H2O)9(?-XW9O33)2] ( X=As and Sb). The pulsed-field magnetization shows pronounced hysteresis loops and magnetization steps including the half-step magnetization. The detailed magnetization behavior depends substantially on the diamagnetic heteroatom X . The angular dependence of ESR parameters necessitates Dzyaloshinskii-Moriya interaction. The temperature dependence of the Na23 spin-lattice relaxation rate, 1/T1 , scales well to ?(T)T , where ?(T) is the static susceptibility. The spin-spin relaxation rate, 1/T2 , increases rapidly for temperatures below 15K due to dipolar interactions between the Na23 nuclei and Cu2+ spins. The two clusters exhibit a markedly different field dependence of 1/T1 at antilevel crossing points. The enhancement of 1/T1 is noticeable only for X=Sb . Since the spin configurations of both clusters are nearly the same, the dependence of magnetization and 1/T1 on X is ascribed to the strong coupling of the spins to a lattice vibration, leading to an enhanced mixing of the S=1/2 chiral state.

Choi, Kwang-Yong; Dalal, Naresh S.; Reyes, Arneil P.; Kuhns, Philip L.; Matsuda, Yasuhiro H.; Nojiri, Hiroyuki; Mal, Sib Sankar; Kortz, Ulrich

2008-01-01

153

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

154

Increasing Hyperpolarized Spin Lifetimes Through True Singlet Eigenstates  

PubMed Central

The sensitivity limitations for magnetic resonance imaging of organic molecules have recently been addressed by hyperpolarization methods, which prepare excess nuclear spin polarization. This approach can increase sensitivity by orders of magnitude, but the enhanced signal relaxes away in tens of seconds, even in favorable cases. Here we show theoretically that singlet states between strongly coupled spins in molecules can be used to store and retrieve population in very-long-lived disconnected eigenstates, as long as the coupling between the spins substantially exceeds both the couplings to other spins and the resonance frequency difference between them. Experimentally, 2,3-carbon-13–labeled diacetyl has a disconnected eigenstate that can store population for minutes and is read out by hydration to make the two spins inequivalent.

Warren, Warren S.; Jenista, Elizabeth; Branca, Rosa Tamara; Chen, Xin

2010-01-01

155

Nuclear magnetic resonance linewidth and spin diffusion in {sup 29}Si isotopically controlled silicon  

SciTech Connect

A nuclear magnetic resonance (NMR) study was performed with n-type silicon single crystals containing {sup 29}Si isotope abundance f ranges from 1.2% to 99.2%. The nuclear spin diffusion coefficient D has been determined from the linewidth of significantly enhanced {sup 29}Si NMR signals utilizing a developed dynamic nuclear polarization (DNP) method. The {sup 29}Si NMR linewidth depends linearly on f, at least when f<10%, and approaches {proportional_to}f{sup 1/2} dependence when f>50%. The estimated {sup 29}Si nuclear spin diffusion time T{sub sd} between phosphorus atoms used for DNP is more than ten times shorter than the nuclear polarization time T{sub 1}{sup p} of {sup 29}Si nuclei around phosphorus. Therefore, the regime of 'rapid spin diffusion' is realized in the DNP experiments.

Hayashi, Hiroshi; Itoh, Kohei M.; Vlasenko, Leonid S. [Department of Applied Physics and Physico-Informatics, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); A. F. Ioffe Physico-Technical Institute, 194021 Saint Petersburg (Russian Federation)

2008-10-15

156

Gauge invariance of the nuclear spin/electron orbit interaction and NMR spectral parameters.  

PubMed

A gauge transformation of the vector potential A(m(I)), associated to the magnetic dipole m(I) of nucleus I in a molecule, has been studied. The conditions for gauge invariance of nuclear magnetic shielding, nuclear spin/electron orbit contribution to spin-spin coupling between two nuclei, I and J, and electronic current density induced by m(I), have been expressed via quantum mechanical sum rules that are identically satisfied for exact and optimal variational wavefunctions. It is shown that separate diamagnetic and paramagnetic contributions to the properties transform into one another in the gauge transformation, whereas their sum is invariant. Therefore, only total response properties have a physical meaning. In particular, the disjoint diamagnetic and paramagnetic components of nuclear spin/electron orbit contributions to coupling constants are not uniquely defined. The diamagnetic contribution to the nuclear spin-spin coupling tensor, evaluated as an expectation value in the Ramsey theory, can alternatively be expressed as a sum-over-states formula, by rewriting the second-order Hamiltonian in commutator form à la Geertsen, as previously reported by Sauer. Other sum-over-states formulae are obtained via a gauge transformation, by a procedure formally allowing for a continuous translation of the origin of the m(I)-induced current density, analogous to those previously proposed for magnetizabilities and nuclear magnetic shielding. PMID:22920104

Lazzeretti, Paolo

2012-08-21

157

Improved characterization of the botanical origin of sugar by carbon-13 SNIF-NMR applied to ethanol.  

PubMed

Until now, no analytical method, not even isotopic ones, had been able to differentiate between sugars coming from C4-metabolism plants (cane, maize, etc.) and some crassulacean acid metabolism plants (e.g., pineapple, agave) because in both cases the isotope distributions of the overall carbon-13/carbon-12 and site-specific deuterium/hydrogen isotope ratios are very similar. Following recent advances in the field of quantitative isotopic carbon-13 NMR measurements, a procedure for the analysis of the positional carbon-13/carbon-12 isotope ratios of ethanol derived from the sugars of pineapples and agave using the site-specific natural isotopic fractionation-nuclear magnetic resonance (SNIF-NMR) method is presented. It is shown that reproducible results can be obtained when appropriate analytical conditions are used. When applied to pineapple juice, this new method demonstrates a unique ability to detect cane and maize sugar, which are major potential adulterants, with a detection limit in the order of 15% of the total sugars, which provides an efficient mean of controlling the authenticity of juices made from this specific fruit. When applied to tequila products, this new method demonstrates a unique ability to unambiguously differentiate authentic 100% agave tequila, as well as misto tequila (made from at least 51% agave), from products made from a larger proportion of cane or maize sugar and therefore not complying with the legal definition of tequila. PMID:21028824

Thomas, Freddy; Randet, Celia; Gilbert, Alexis; Silvestre, Virginie; Jamin, Eric; Akoka, Serge; Remaud, Gerald; Segebarth, Nicolas; Guillou, Claude

2010-11-24

158

Zeeman perturbed nuclear quadrupole spin echo envelope modulations for spin 3/2 nuclei in polycrystalline specimens  

NASA Astrophysics Data System (ADS)

The results of theoretical and experimental studies of Zeeman-perturbed nuclear quadrupole spin echo envelope modulations (ZSEEM) for spin 3/2 nuclei in polycrystalline specimens are presented. The response of the Zeeman-perturbed spin ensemble to resonant two pulse excitations has been calculated using the density matrix formalism. The theoretical calculation assumes a parallel orientation of the external r.f. and static Zeeman fields and an arbitrary orientation of these fields to the principal axes system of the electric field gradient. A numerical powder averaging procedure has been adopted to simulate the response of the polycrystalline specimens. Using a coherent pulsed nuclear quadrupole resonance spectrometer the ZSEEM patterns of the 35Cl nuclei have been recorded in polycrystalline specimens of potassium chlorate, barium chlorate, mercuric chloride (two sites) and antimony trichloride (two sites) using the ?/2-?-?/2 sequence. The theoretical and experimental ZSEEM patterns have been compared. In the case of mercuric chloride, the experimental 35Cl ZSEEM patterns are found to be nearly identical for the two sites and correspond to a near-zero value of the asymmetry parameter, ?, of the electric field gradient tensor. The difference in the ? values for the two 35Cl sites (? ˜0·06 and ?˜0·16) in antimony trichloride is clearly reflected in the experimental and theoretical ZSEEM patterns. The present study indicates the feasibility of evaluating ? for spin 3/2 nuclei in polycrystalline specimens from ZSEEM investigations.

Ramachandran, R.; Narasimhan, P. T.

159

Distribution of spacings of nuclear energy levels of mixed spin and parity  

Microsoft Academic Search

An experimental spacing distribution for nuclear levels of mixed spin and parity is derived for 980 levels of 18 different nuclei. The experimental nuclear energy levels, taken from recent literature, were all determined by analyses of particles from (p, p') and\\/or (p, alpha) reactions with magnetic spectrographs. When proper account is taken of the experimental enrgy resolution, the spacing distribution

J. R. Huizenga; A. A. Katsanos

1967-01-01

160

Graph theoretical characterization of NMR groups, nonrigid nuclear spin species and the construction of symmetry adapted NMR spin functions  

NASA Astrophysics Data System (ADS)

NMR group defined by Woodman is shown to be the generalized wreath product group of the NMR graph which is constructed with protons as vertices and edges representing nuclear couplings. The NMR graph can be expressed as a generalized composition of its quotient graph and various types. It is shown that the NMR group is the automorphism group of the NMR graph that preserves the coupling matrix defined here. Using the representation theory of generalized wreath product groups developed in an earlier paper of the present author, the character tables of NMR groups can be obtained. The character tables of certain NMR groups are presented. The quotient graph of the NMR graph is shown to be the composite particle graph. The automorphism group of the quotient NMR graph is the symmetry group of the composite particles, preserving the NMR coupling constants. An iterative algorithm is formulated for obtaining the automorphism group of the composite particle tree. A combinatorial approach is expounded for identifying the nuclear spin species of nonrigid and rigid molecules. The coalescence diagrams describing the effect of nonrigidity on nuclear spin species are introduced and obtained to exemplify the utility of the proposed method. It is shown that using the automorphism group of the quotient graph, the symmetry adapted composite particle spin functions can be constructed. We illustrate this method with 2,3-dimethylbutane. The nuclear spin Hamiltonian matrix of 2,3-dimethylbutane of order 214×214 is reduced to a matrix of order 64×64 by the composite particle method. This matrix can be blocked in the symmetry adapted basis set constructed through the automorphism group of the quotient graph into 40 matrices of order 1×1 and 12 matrices of order 2×2.

Balasubramanian, K.

1980-10-01

161

Quantitative Analysis of Transferred Nuclear Overhauser Effects in Complex Spin Systems by Full Relaxation Matrix Analysis  

NASA Astrophysics Data System (ADS)

A computer program was developed for studying transferred nuclear Overhauser effects in complex spin systems. It permits quantitative analysis of nuclear Overhauser effects observed in biologically important systems, such as ligands interacting with transmembrane receptors in the presence of lipid bilayers. The full generalized relaxation matrix approach takes into account the local mobility, spin equivalence, finite exchange rates, and spectral overlap. The program can be used either to simulate theoretical nuclear Overhauser effect buildup curves or to fit a relaxation matrix of a given model to experimental data. Selected examples illustrate the program's performance.

Czaplicki, J.; Milon, A.

2006-07-01

162

Nuclear spin dynamics in double quantum dots: Multistability, dynamical polarization, criticality, and entanglement  

NASA Astrophysics Data System (ADS)

We theoretically study the nuclear spin dynamics driven by electron transport and hyperfine interaction in an electrically defined double quantum dot in the Pauli-blockade regime. We derive a master-equation-based framework and show that the coupled electron-nuclear system displays an instability towards the buildup of large nuclear spin polarization gradients in the two quantum dots. In the presence of such inhomogeneous magnetic fields, a quantum interference effect in the collective hyperfine coupling results in sizable nuclear spin entanglement between the two quantum dots in the steady state of the evolution. We investigate this effect using analytical and numerical techniques, and demonstrate its robustness under various types of imperfections.

Schuetz, M. J. A.; Kessler, E. M.; Vandersypen, L. M. K.; Cirac, J. I.; Giedke, G.

2014-05-01

163

Dynamic nuclear spin polarization of liquids and gases in contact with nanostructured diamond.  

PubMed

Optical pumping of spin polarization can produce almost complete spin order but its application is restricted to select atomic gases and condensed matter systems. Here, we theoretically investigate a novel route to nuclear spin hyperpolarization in arbitrary fluids in which target molecules are exposed to polarized paramagnetic centers located near the surface of a host material. We find that adsorbed nuclear spins relax to positive or negative polarization depending on the average paramagnetic center depth and nanoscale surface topology. For the particular case of optically pumped nitrogen-vacancy centers in diamond, we calculate strong nuclear spin polarization at moderate magnetic fields provided the crystal surface is engineered with surface roughness in the few-nanometer range. The equilibrium nuclear spin temperature depends only weakly on the correlation time describing the molecular adsorption dynamics and is robust in the presence of other, unpolarized paramagnetic centers. These features could be exploited to polarize flowing liquids or gases, as we illustrate numerically for the model case of a fluid brought in contact with an optically pumped diamond nanostructure. PMID:24754755

Abrams, Daniel; Trusheim, Matthew E; Englund, Dirk R; Shattuck, Mark D; Meriles, Carlos A

2014-05-14

164

Electron correlation effects on the theoretical calculation of nuclear magnetic resonance spin–spin coupling constants  

Microsoft Academic Search

The equation-of-motion coupled cluster singles and doubles (EOM-CCSD) method for general second-order properties is derived providing a quadratic, CI-like approximation and its linked form from coupled cluster (CC) energy derivative theory. The effects of the quadratic contribution, of the atomic basis set employed, and of electron correlation on NMR spin–spin coupling constant calculations using EOM-CCSD methods are investigated for a

S. Ajith Perera; Marcel Nooijen; Rodney J. Bartlett

1996-01-01

165

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

NASA Astrophysics Data System (ADS)

We report solid state 13C and 1H 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, 1H and cross-polarized 13C NMR signals from 15N,13C-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 T1e 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.; Tycko, Robert

2014-05-01

166

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

PubMed

We report solid state (13)C and (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, (1)H and cross-polarized (13)C NMR signals from (15)N,(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 T1e 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. PMID:24832263

Thurber, Kent R; Tycko, Robert

2014-05-14

167

The Spin Dependence of Nuclear Muon Capture by Laser Polarized HELIUM3  

Microsoft Academic Search

Using the muon beam at TRIUMF, we have made the first measurement of the spin dependence of the reaction: mu^- + ^3He tonu +^3H. This spin dependence is quite sensitive to the induced pseudoscalar form factor, F_{P}, a piece of the weak charged nuclear current of ^3He about which, experimentally, relatively little is known. The ratio of F_{P} to F

Paul Lev Bogorad

1995-01-01

168

Invalidity of Geometrical Interpretation of F-Spin Structure of Nuclear Rotations by Otsuka's View  

NASA Astrophysics Data System (ADS)

In Otsuka's view of nuclear rotations neutrons and protons are not rotating around a common axis, but rather around separate axis. In this letter, we pointed out that this invalidates the geometrical interpretation of F-spin structure of the neutron-proton interacting boson model, where the angle between the axis of symmetries of neutron ellipsoid and proton ellipsoid is used to determine whether a state is F-spin symmetric or mixed symmetric.

Long, Guilu

1995-06-01

169

Solid-state nuclear-spin quantum computer based on magnetic resonance force microscopy  

SciTech Connect

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 1 K. (c) 2000 The American Physical Society.

Berman, G. P. [Theoretical Division and CNLS, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Theoretical Division and CNLS, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Doolen, G. D. [Theoretical Division and CNLS, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Theoretical Division and CNLS, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Hammel, P. C. [MST-10, Los Alamos National Laboratory, MS K764, Los Alamos, New Mexico 87545 (United States)] [MST-10, Los Alamos National Laboratory, MS K764, Los Alamos, New Mexico 87545 (United States); Tsifrinovich, V. I. [IDS Department, Polytechnic University, Six Metrotech Center, Brooklyn, New York 11201 (United States)] [IDS Department, Polytechnic University, Six Metrotech Center, Brooklyn, New York 11201 (United States)

2000-06-01

170

Locking electron spins into magnetic resonance by electron-nuclear feedback  

NASA Astrophysics Data System (ADS)

Quantum information processing requires accurate coherent control of quantum-mechanical two-level systems, but is hampered in practice by their coupling to an uncontrolled environment. For electron spins in III-V quantum dots, the random environment is mostly given by the nuclear spins in the quantum-dot host material; they collectively act on the electron spin through the hyperfine interaction, much like a random magnetic field. Here we show that the same hyperfine interaction can be harnessed such that partial control of the normally uncontrolled environment becomes possible. In particular, we observe that the electron-spin-resonance frequency remains locked to the frequency of an applied microwave magnetic field, even when the external magnetic field or the excitation frequency are changed. The nuclear field thereby adjusts itself such that the electron-spin-resonance condition remains satisfied. General theoretical arguments indicate that this spin-resonance locking might be accompanied by a significant reduction of the randomness in the nuclear field.

Vink, Ivo T.; Nowack, Katja C.; Koppens, Frank H. L.; Danon, Jeroen; Nazarov, Yuli V.; Vandersypen, Lieven M. K.

2009-10-01

171

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

172

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

173

Quantum oscillations and polarization of nuclear spins in photoexcited triplet states.  

PubMed

The unique physical properties of photoexcited triplet states have been explored in numerous spectroscopic studies employing electron paramagnetic resonance (EPR). So far, however, no quantum interference effects were found in these systems in the presence of a magnetic field. In this study, we report the successful EPR detection of nuclear quantum oscillations in an organic triplet state subject to an external magnetic field. The observed quantum coherences can be rationalized using an analytical theory. Analysis suggests that the nuclear spins are actively involved in the intersystem crossing process. The novel mechanism also acts as a source of oscillatory nuclear spin polarization that gives rise to large signal enhancement in nuclear magnetic resonance (NMR). This opens new perspectives for the analysis of chemically induced dynamic nuclear polarization in mechanistic studies of photoactive proteins. PMID:20666450

Kothe, Gerd; Yago, Tomoaki; Weidner, Jörg-Ulrich; Link, Gerhard; Lukaschek, Michail; Lin, Tien-Sung

2010-11-18

174

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

175

Vector Model Of Electron Spin Echo Envelope Modulation Due To Nuclear Hyperfine And Zeeman Interactions  

SciTech Connect

The transverse electron spin magnetization of a paramagnetic center with effective spin S=? interacting with nonquadrupolar nuclei may be presented as a function of pairs of nuclei magnetization vectors which process around the effective magnetic field directions. Each vector of the pair starts its precession perpendicular to both effective fields. The FID signal is proportional to the scalar product of the vectors for nuclear spin I=?. The ESE signal can be described using two pairs of magnetization vectors. The ESE shape is not equal to two back-to-back FID signals except in the absence of ESE envelope modulation. A recursion relation is obtained which allows calculation of ESE signals for larger nuclear spins in the absence of NQI. This relation can be used to calculate the time course of the ESE signal for arbitrary nuclear spin as a function of the nuclear magnetization vectors. Although this formalism allows quantitative calculation of modulation from nuclei, it also provides a qualitative means of visualizing the modulation based on simple magnetization vectors.

Maryasov, Alexander G. (OFFICE OF FELLOWSHIP PROG); Bowman, Michael K. (BATTELLE (PACIFIC NW LAB)); Tsvetkov, Yuri D. (OFFICE OF FELLOWSHIP PROG)

2002-12-01

176

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

PubMed Central

We present theoretical calculations of dynamic nuclear polarization (DNP) due to the cross effect in nuclear magnetic resonance under magic-angle spinning (MAS). Using a three-spin model (two electrons and one nucleus), cross effect DNP with MAS for electron spins with a large g-anisotropy can be seen as a series of spin transitions at avoided crossings of the energy levels, with varying degrees of adiabaticity. If the electron spin-lattice relaxation time T1e is large relative to the MAS rotation period, the cross effect can happen as two separate events: (i) partial saturation of one electron spin by the applied microwaves as one electron spin resonance (ESR) frequency crosses the microwave frequency and (ii) flip of all three spins, when the difference of the two ESR frequencies crosses the nuclear frequency, which transfers polarization to the nuclear spin if the two electron spins have different polarizations. In addition, adiabatic level crossings at which the two ESR frequencies become equal serve to maintain non-uniform saturation across the ESR line. We present analytical results based on the Landau-Zener theory of adiabatic transitions, as well as numerical quantum mechanical calculations for the evolution of the time-dependent three-spin system. These calculations provide insight into the dependence of cross effect DNP on various experimental parameters, including MAS frequency, microwave field strength, spin relaxation rates, hyperfine and electron-electron dipole coupling strengths, and the nature of the biradical dopants.

Thurber, Kent R.; Tycko, Robert

2012-01-01

177

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

PubMed

We present theoretical calculations of dynamic nuclear polarization (DNP) due to the cross effect in nuclear magnetic resonance under magic-angle spinning (MAS). Using a three-spin model (two electrons and one nucleus), cross effect DNP with MAS for electron spins with a large g-anisotropy can be seen as a series of spin transitions at avoided crossings of the energy levels, with varying degrees of adiabaticity. If the electron spin-lattice relaxation time T(1e) is large relative to the MAS rotation period, the cross effect can happen as two separate events: (i) partial saturation of one electron spin by the applied microwaves as one electron spin resonance (ESR) frequency crosses the microwave frequency and (ii) flip of all three spins, when the difference of the two ESR frequencies crosses the nuclear frequency, which transfers polarization to the nuclear spin if the two electron spins have different polarizations. In addition, adiabatic level crossings at which the two ESR frequencies become equal serve to maintain non-uniform saturation across the ESR line. We present analytical results based on the Landau-Zener theory of adiabatic transitions, as well as numerical quantum mechanical calculations for the evolution of the time-dependent three-spin system. These calculations provide insight into the dependence of cross effect DNP on various experimental parameters, including MAS frequency, microwave field strength, spin relaxation rates, hyperfine and electron-electron dipole coupling strengths, and the nature of the biradical dopants. PMID:22938251

Thurber, Kent R; Tycko, Robert

2012-08-28

178

Properties of Nuclear Matter with an Excess of Neutrons, of Spin-Up Neutrons and of Spin-Up Protons Using the Skyrme Interaction.  

National Technical Information Service (NTIS)

The binding energy of nuclear matter with an excess of neutrons, of spin-up neutrons, and of spin-up protons (characterized by the corresponding parameters, alpha sub(tau)=(N-Z/A), alpha sub(n)=(Nup-Ndown)/A, and alpha sub(rho)=(Zup-Zdown)/A), contains th...

M. Y. M. Hassan S. Ramadan

1983-01-01

179

High-resolution spectroscopy of single NV defects coupled with nearby 13C nuclear spins in diamond  

NASA Astrophysics Data System (ADS)

We report a systematic study of the hyperfine interaction between the electron spin of a single nitrogen-vacancy (NV) defect in diamond and nearby 13C nuclear spins, by using pulsed electron-spin resonance spectroscopy. We isolate a set of discrete values of the hyperfine coupling strength ranging from 14 MHz to 400 kHz and corresponding to 13C nuclear spins placed at different lattice sites of the diamond matrix. For each lattice site, the hyperfine interaction is further investigated through nuclear-spin polarization measurements and by studying the magnetic field dependence of the hyperfine splitting. This work provides information that is relevant for the development of nuclear-spin-based quantum register in diamond.

Dréau, A.; Maze, J.-R.; Lesik, M.; Roch, J.-F.; Jacques, V.

2012-04-01

180

Splitting of the one-body potential in spin-polarized isospin-symmetric nuclear matter  

SciTech Connect

Spin-polarized symmetric nuclear matter is studied within the Dirac-Brueckner-Hartree-Fock approach. We pay particular attention to the difference between the one-body potentials of upward and downward polarized nucleons. This is formally analogous to the Lane potential for isospin-asymmetric nuclear matter. We point out the necessity for additional information on this fundamentally important quantity and suggest ways to constrain it.

Sammarruca, Francesca [Department of Physics, University of Idaho, Moscow, Idaho 83844-0903 (United States)

2010-08-15

181

Electrically-induced shifts of the gallium arsenide nuclear spin levels  

Microsoft Academic Search

The application of a dc homogeneous electric field on a GaAs crystal will induce a quadrupolar splitting of the nuclear spin levels. This splitting was observed for Ga-71, Ga-69, and As-75 using a pulsed nuclear magnetic resonance spectrometer. A constant R sub 14 that relates the coupling between the induced field gradient and the applied electric field was measured. The

K. A. Dumas

1978-01-01

182

Nuclear spin-lattice relaxation times of metallic antimony at low temperatures  

Microsoft Academic Search

We have used pulsed Nuclear Quadrupole Resonance (NQR) techniques to measure the nuclear spin-lattice relaxation times in antimony at low temperatures. High quality echoes with strong signal\\/noise ratios were only observed for finely powdered samples of high purity (99.9999%). The samples were carefully annealed and diluted with fine silica to below the percolation limit to minimize RF heating. The powder

E. B. Genio; J. Xu; T. Lang; G. G. Ihas; N. S. Sullivan

1995-01-01

183

Direct Observation of a Nuclear Spin Excitation in Ho2Ti2O7  

SciTech Connect

A single nondispersive excitation is observed by means of neutron backscattering, at E{sub 0} = 26.3 {micro}eV in the spin ice Ho{sub 2}Ti{sub 2}O{sub 7} but not in the isotopically enriched {sup 162}Dy{sub 2}Ti{sub 2}O{sub 7} analogue. The intensity of this excitation is rather small, {approx}< 0.2% of the elastic intensity. It is clearly observed below 80 K but resolution limited only below {approx}65 K. The application of a magnetic field up to {mu}{sub 0}H = 4.5 T, at 1.6 K, has no measurable effect on the energy or intensity. This nuclear excitation is believed to perturb the electronic, Ising spin system resulting in the persistent spin dynamics observed in spin ice compounds.

Ehlers, Georg [ORNL; Mamontov, Eugene [ORNL; Zamponi, Michaela M [ORNL

2009-01-01

184

Direct observation of a nuclear spin excitation in Ho2Ti2O7.  

PubMed

A single nondispersive excitation is observed by means of neutron backscattering, at E_{0}=26.3 microeV in the spin ice Ho2Ti2O7 but not in the isotopically enriched 162Dy2Ti2O7 analogue. The intensity of this excitation is rather small, less, similar0.2% of the elastic intensity. It is clearly observed below 80 K but resolution limited only below approximately 65 K. The application of a magnetic field up to micro_{0}H=4.5 T, at 1.6 K, has no measurable effect on the energy or intensity. This nuclear excitation is believed to perturb the electronic, Ising spin system resulting in the persistent spin dynamics observed in spin ice compounds. PMID:19257221

Ehlers, G; Mamontov, E; Zamponi, M; Kam, K C; Gardner, J S

2009-01-01

185

A Search for Nonstandard Neutron Spin Interactions using Dual Species Xenon Nuclear Magnetic Resonance  

NASA Astrophysics Data System (ADS)

NMR measurements using polarized noble gases can constrain possible exotic spin-dependent interactions involving nucleons. A differential measurement insensitive to magnetic field fluctuations can be performed using a mixture of two polarized species with different ratios of nucleon spin to magnetic moment. We used the NMR cell test station at Northrop Grumman Corporation (NGC) (developed to evaluate dual species xenon vapor cells for the Nuclear Magnetic Resonance Gyroscope) to search for NMR frequency shifts of xenon-129 and xenon-131 when a non-magnetic zirconia rod is modulated near the NMR cell. We simultaneously excited both Xe isotopes and detected free-induction-decay transients. In combination with theoretical calculations of the neutron spin contribution to the nuclear angular momentum, the measurements put a new upper bound on possible monopole-dipole interactions of the neutron for ranges around 1mm. This work is supported by the NGC Internal Research and Development (IRAD) funding, the Department of Energy, and the NSF.

Bulatowicz, Michael; Larsen, Michael; Mirijanian, James; Fu, Changbo; Yan, Haiyang; Smith, Erick; Snow, Mike; Walker, Thad

2012-06-01

186

Anisotropic indirect nuclear spin-spin coupling in InP: 31P CP NMR study under slow MAS condition  

NASA Astrophysics Data System (ADS)

The indirect nuclear spin-spin interaction tensor between neighboring 113,115In- 31P spins in Fe-doped InP semiconductor has been studied by 31P NMR spectra measured using CP of 113In ? 31P and 115In ? 31P under slow MAS condition. The isotropic ( Jiso) and anisotropic ( Janiso = 2/3[ J? - J?]) parts of the indirect interaction tensor are obtained from the spectral simulation. The acceptable combinations of these values are found to be as follows: ( Jiso, Janiso) = (224 ± 5, 500 ± 100 Hz) or (-224 ± 5, 2100 ± 100 Hz). Although, the coupling constants estimated in this study are slightly different from previously reported values of ? Jiso? = 350 Hz, Janiso = 1298 Hz [M. Engelsberg, R.E. Norberg, Phys. Rev. B 5 (1972) 3395] and of ? Jiso? = 225 ± 10, Janiso = (813 ± 50) or (1733 ± 50) Hz [M. Tomaselli et al., Phys. Rev. B 58 (1998) 8627], all of these has the trend that Janiso is rather larger than Jiso.

Iijima, Takahiro; Hashi, Kenjiro; Goto, Atsushi; Shimizu, Tadashi; Ohki, Shinobu

2006-02-01

187

Nuclear Spin Relaxation and Molecular Interactions of a Novel Triazolium-Based Ionic Liquid  

SciTech Connect

Nuclear spin relaxation, small-angle X-ray scattering (SAXS), and electrospray ionization mass spectrometry (ESI-MS) techniques are used to determine supramolecular arrangement of 3-methyl-1-octyl-4-phenyl-1H-triazol-1,2,3-ium bis(trifluoromethanesulfonyl)imide [OMPhTz][Tf{sub 2}N], an example of a triazolium-based ionic liquid. The results obtained showed first-order thermodynamic dependence for nuclear spin relaxation of the anion. First-order relaxation dependence is interpreted as through-bond dipolar relaxation. Greater than first-order dependence was found in the aliphatic protons, aromatic carbons (including nearest neighbors), and carbons at the end of the aliphatic tail. Greater than first order thermodynamic dependence of spin relaxation rates is interpreted as relaxation resulting from at least one mechanism additional to through-bond dipolar relaxation. In rigid portions of the cation, an additional spin relaxation mechanism is attributed to anisotropic effects, while greater than first order thermodynamic dependence of the octyl side chain’s spin relaxation rates is attributed to cation–cation interactions. Little interaction between the anion and the cation was observed by spin relaxation studies or by ESI-MS. No extended supramolecular structure was observed in this study, which was further supported by MS and SAXS. nuclear Overhauser enhancement (NOE) factors are used in conjunction with spin–lattice relaxation time (T{sub 1}) measurements to calculate rotational correlation times for C–H bonds (the time it takes for the vector represented by the bond between the two atoms to rotate by one radian). The rotational correlation times are used to represent segmental reorientation dynamics of the cation. A combination of techniques is used to determine the segmental interactions and dynamics of this example of a triazolium-based ionic liquid.

Allen, Jesse J.; Schneider, Yanika; Kail, Brian W.; Luebke, David R.; Nulwala, Hunaid; Damodaran, Krishnan

2013-04-11

188

Electric readout and storage concepts for electron and nuclear spin states in silicon  

NASA Astrophysics Data System (ADS)

A variety of concepts utilizing spins in semiconductors for information storage and processing have been proposed in recent years. One of these concepts [1] uses the phosphorous nucleus in crystalline silicon as a quantum bit, an approach which combines longest known spin coherence times and, therefore, spin storage times, with already existing, well developed and highly reliable, crystalline silicon nano-technology. Our research is focused on implementations of electric readout devices for electron- and nuclear-spins in silicon. I will review different experiments which show how donor electrons [2-4] and nuclear [5] spins of phosphorous atoms in crystalline silicon can be used as a electrically readable spin memories with long storage times for classical and quantum information and how nuclear spin qubits can be initialized [6].[4pt] [1] B. E. Kane, Nature 393, 133 (1998).[0pt] [2] A. R. Stegner, C. Boehme, H. Huebl, M. Stutzmann, K. Lips, M. S. Brandt, Nature Physics 2, 835 (2006). [0pt] [3] S.-Y. Paik, S.-Y. Lee, W. J. Baker, D. R. McCamey, and C. Boehme, Phys. Rev. B 81, 075214 (2010).[0pt] [4] G. W. Morley, D. R. McCamey, H. A. Seipel, L.-C. Brunel, J. van Tol, C. Boehme, Phys. Rev. Lett. 101, 207602 (2008).[0pt] [5] D. R. McCamey, J. van Tol, G. W. Morley, C. Boehme, Science 330, 1652 (2010).[0pt] [6] D. R. McCamey, J. van Tol, G. W. Morley, C. Boehme, Phys. Rev. Lett. 102, 027601 (2009).

Boehme, Christoph

2011-10-01

189

Relevance of electron spin dissipative processes to dynamic nuclear polarization via thermal mixing.  

PubMed

The available theoretical approaches aiming at describing Dynamic Nuclear spin Polarization (DNP) in solutions containing molecules of biomedical interest and paramagnetic centers are not able to model the behaviour observed upon varying the concentration of trityl radicals or the polarization enhancement caused by moderate addition of gadolinium complexes. In this manuscript, we first show experimentally that the nuclear steady state polarization reached in solutions of pyruvic acid with 15 mM trityl radicals is substantially independent on the average internuclear distance. This evidences a leading role of electron (over nuclear) spin relaxation processes in determining the ultimate performances of DNP. Accordingly, we have devised a variant of the Thermal Mixing model for inhomogenously broadened electron resonance lines which includes a relaxation term describing the exchange of magnetic anisotropy energy of the electron spin system with the lattice. Thanks to this additional term, the dependence of the nuclear polarization on the electron concentration can be properly accounted for. Moreover, the model predicts a strong increase of the final polarization upon shortening the electron spin-lattice relaxation time, providing a possible explanation for the effect of gadolinium doping. PMID:24270353

Serra, Sonia Colombo; Filibian, Marta; Carretta, Pietro; Rosso, Alberto; Tedoldi, Fabio

2014-01-14

190

Nuclear Spin Measurements in Some Nuclides of the Alkali Elements Rubidium and Francium.  

National Technical Information Service (NTIS)

The nuclear spins of several nuclides of the alkali elements rubidium and francium have been measured using atomic-beam magnetic resonance techniques. The following results have been obtained: exp 77 Rb I = 3/2, exp 78 Rb I = 0 sup(78m)Rb I = 4, exp 79 Rb...

C. Ekstroem S. Ingleman G. Wannberg M. Skarestad

1977-01-01

191

Optical superradiance from nuclear spin environment of single-photon emitters.  

PubMed

We show that superradiant optical emission can be observed from the polarized nuclear spin ensemble surrounding a single-photon emitter such as a single quantum dot or nitrogen-vacancy center. The superradiant light is emitted under optical pumping conditions and would be observable with realistic experimental parameters. PMID:20481939

Kessler, E M; Yelin, S; Lukin, M D; Cirac, J I; Giedke, G

2010-04-01

192

Nuclear spin measurements of neutron-deficient isotopes of the refractory elements  

NASA Astrophysics Data System (ADS)

Nuclear ground and isomeric state spins of several isotopes of the refractory elements (Y, Nb, Mo, Tc, Rh, Ta, Re, Os, Ir, Pt) measured by the atomic beam magnetic resonance method, are reported. The atomic ground-state g-factor for the Os atom has also been measured.

Rubinsztein, H.; Gustafsson, M.

1975-09-01

193

Quantum dynamical simulations for nuclear spin selective laser control of ortho- and para-fulvene  

NASA Astrophysics Data System (ADS)

In the present paper we explore the prospects for laser control of the photoinduced nonadiabatic dynamics of para- and ortho-fulvene with the help of quantum dynamical simulations. Previous investigations [Bearpark et al., J. Am. Chem. Soc. 118, 5253 (1996); Alfalah et al., J. Chem. Phys. 130, 124318 (2009)] show that photoisomerization of fulvene is hindered by ultrafast radiationless decay through a conical intersection at planar configuration. Here, we demonstrate that photoisomerization can nevertheless be initiated by damping unfavorable nuclear vibrations with properly designed laser pulses. Moreover, we show that the resulting intramolecular torsion is nuclear spin selective. The selectivity of the photoexcitation with respect to the nuclear spin isomers can be further enhanced by applying an optimized sequence of two laser pulses.

Belz, S.; Grohmann, T.; Leibscher, M.

2009-07-01

194

Electron and nuclear spin dynamics in plastically deformed silicon crystals enriched in isotope 29Si  

NASA Astrophysics Data System (ADS)

Paramagnetic defects of a new type with a concentration of about 1015 cm-3 are shown to be generated during the plastic deformation of isotope-rich (72%, 76% 29Si) silicon crystals at a temperature of 950°C. The electron paramagnetic resonance (EPR) spectra of these defects are anisotropic and have a significant width (up to 1 kOe). The nonuniform broadening of the EPR lines is caused by the variation of the internal magnetic field in correlated defect clusters. The nuclear magnetic resonance (NMR) spectra of the deformed crystals consist of Pake doublets split by nuclear spin-spin interaction. The broadening of the NMR spectra is caused by nuclear dipole-dipole relaxation.

Koplak, O. V.; Dmitriev, A. I.; Vasil'ev, S. G.; Shteinman, E. A.; Morgunov, R. B.

2014-04-01

195

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

196

Advances and applications of dynamic-angle spinning nuclear magnetic resonance  

SciTech Connect

This dissertation describes nuclear magnetic resonance experiments and theory which have been developed to study quadrupolar nuclei (those nuclei with spin greater than one-half) in the solid state. Primarily, the technique of dynamic-angle spinning (DAS) is extensively reviewed and expanded upon in this thesis. Specifically, the improvement in both the resolution (two-dimensional pure-absorptive phase methods and DAS angle choice) and sensitivity (pulse-sequence development), along with effective spinning speed enhancement (again through choice of DAS conditions or alternative multiple pulse schemes) of dynamic-angle spinning experiment was realized with both theory and experimental examples. The application of DAS to new types of nuclei (specifically the {sup 87}Rb and {sup 85}Rb nuclear spins) and materials (specifically amorphous solids) has also greatly expanded the possibilities of the use of DAS to study a larger range of materials. This dissertation is meant to demonstrate both recent advances and applications of the DAS technique, and by no means represents a comprehensive study of any particular chemical problem.

Baltisberger, J.H.

1993-06-01

197

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

198

Spin- and isospin-polarized states of nuclear matter in the Dirac-Brueckner-Hartree-Fock model  

SciTech Connect

Spin-polarized isospin asymmetric nuclear matter is studied within the Dirac-Brueckner-Hartree-Fock approach. After a brief review of the formalism, we present and discuss the self-consistent single-particle potentials at various levels of spin and isospin asymmetry. We then move to predictions of the energy per particle, also under different conditions of isospin and spin polarization. Comparison with the energy per particle in isospin symmetric or asymmetric unpolarized nuclear matter shows no evidence for a phase transition to a spin-ordered state, neither ferromagnetic nor antiferromagnetic.

Sammarruca, Francesca [Physics Department, University of Idaho, Moscow, Idaho 83844-0903 (United States)

2011-06-15

199

High-Spin Isomeric States in Nuclear Reactions Induced by He Isotopes  

NASA Astrophysics Data System (ADS)

The high-spin states production in nuclear reactions is reviewed. The analysis of various experiments, our estimates and calculations reveal that in different compound nucleus energy regions maximal relative yield of high-spin states can be realized by different projectiles: at low energies -- by neutrons, in ˜ 20 -- 50 MeV region -- by ?-particles, at higher energies -- by heavy ions. It was predicted [1] that there are energy ranges in which neutron-rich radioactive ions (^6,8He, for example) are favorable. ?m/?g (the ratio between the yields of high-spin Jm and low-spin Jg metastable states of a nucleus in one and the same reaction) e.g. the isomeric cross-section ratio is a very good indicator of high-spin states production capability of a nuclear reaction. These experiments demonstrate that maximal values of isomeric cross-section ratios (up to 30) are obtained in ?-particle induced reactions. Experiment with ^6He beam [2] confirms the predictions of the work [1] concerning the prospects of neutron-rich radioactive-ion beams in high-spin states population. The results of calculations of the isomeric cross section ratios using the code EMPIRE-II-18 approach to statistical theory of nuclear reactions demonstrate rather good agreement with the experimental data. Due to that these prediction power of these calculation is confirmed. The results of widespread calculations of the isomeric cross-section ratios of the reactions with ^6,8He are presented. [1] T.V.Chvilskaya et al., AIP-Conference Proceedings ENAM-98 1998. V. 455. P. 482. [2] P.A.DeYoung et al., Phys.Rev.C. 2000. V. 62. P.047601.

Chuvilskaya, Tatjana; Shirokova, Alla

2010-11-01

200

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

201

Shell structure at high spin and the influence on nuclear shapes  

SciTech Connect

Nuclear structure at high spin is influenced by a combination of liquid-drop and shell-structure effects. For N < 86 both contribute towards the occurrence along the yrast line of high-spin oblate aligned-particle configurations. Shell effects are mainly responsible for the prolate deformation of nuclei with N > 90. The competition between oblate and prolate driving effects leads to a prolate-to-oblate shape transition in /sup 154/Dy/sub 88/. The role of rotation-aligned configurations in the shape change is discussed.

Khoo, T.L.; Chowdhury, P.; Ahmad, I.

1982-01-01

202

Relativistic impulse approximation, nuclear currents, and the spin-difference function  

NASA Astrophysics Data System (ADS)

Traditional nonrelativistic impulse-approximation treatments of p-nucleus scattering using a local nucleon-nucleon t matrix neglect nuclear currents which are intrinsic to relativistic approaches also employing a local t matrix. Inclusion of these current terms is essen- tial to understanding the spin-difference function (Dqk+Dkq) +i(P-Ay), as shown by comparison with 12C(p,p')12C*(12.71 MeV, 1+, T=0) spin-difference data at 150 MeV.

Sparrow, D. A.; Piekarewicz, J.; Rost, E.; Shepard, J. R.; McNeil, J. A.; Carey, T. A.; McClelland, J. B.

1985-05-01

203

Relativistic impulse approximation, nuclear currents, and the spin-difference function  

SciTech Connect

Traditional nonrelativistic impulse-approximation treatments of p-nucleus scattering using a local nucleon-nucleon t matrix neglect nuclear currents which are intrinsic to relativistic approaches also employing a local t matrix. Inclusion of these current terms is essen- tial to understanding the spin-difference function (D/sub q/k+D/sub kq/) +i(P-A/sub y/), as shown by comparison with /sup 12/C(p,p')/sup 12/C((12.71 MeV, 1/sup +/, T = 0) spin-difference data at 150 MeV.

Sparrow, D.A.; Piekarewicz, J.; Rost, E.; Shepard, J.R.; McNeil, J.A.; Carey, T.A.; McClelland, J.B.

1985-05-20

204

High-field dynamic nuclear polarization with high-spin transition metal ions.  

PubMed

We report the dynamic nuclear polarization of (1)H spins in magic-angle-spinning spectra recorded at 5 T and 84 K via the solid effect using Mn(2+) and Gd(3+) complexes as polarizing agents. We show that the magnitude of the enhancements can be directly related to the effective line width of the central (m(S) = -1/2 ? +1/2) EPR transition. Using a Gd(3+) complex with a narrow central transition EPR line width of 29 MHz, we observed a maximum enhancement of ?13, which is comparable to previous results on the narrow-line-width trityl radical. PMID:21446700

Corzilius, Björn; Smith, Albert A; Barnes, Alexander B; Luchinat, Claudio; Bertini, Ivano; Griffin, Robert G

2011-04-20

205

High Field Dynamic Nuclear Polarization with High-Spin Transition Metal Ions  

PubMed Central

We report the dynamic nuclear polarization of 1H spins in magic angle spinning spectra recorded at 5 T and 84K via the solid effect using Mn2+ and Gd3+ complexes as polarizing agents. We show that the magnitude of the enhancements can be directly related to the effective linewidth of the central (MS = ?1/2 ?+1/2) EPR transition. Using a Gd3+ complex with a narrow central transition EPR linewidth of 29 MHz, a maximum enhancement of ~13 is observed, which is comparable to previous results on the narrow linewidth trityl radical.

Corzilius, Bjorn; Smith, Albert A.; Barnes, Alexander B.; Luchinat, Claudio; Bertini, Ivano; Griffin, Robert G.

2011-01-01

206

Isovector spin observables in nuclear charge reactions at LAMPF  

SciTech Connect

LAMPF has undertaken a major development program to upgrade facilities for nuclear charge-exchange studies at intermediate energies. The major components of this upgrade are a medium-resolution spectrometer and neutron time-of-flight system for good resolution (delta E < 1 MeV) charge-exchange perograms in (n,p) and (p,n) respectively. Major emphasis is placed on polarization phenomena using polarized beams and analyzing the polarization of the outgoing particle.

McClelland, J.B.

1988-01-01

207

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.

208

High-pressure Magic Angle Spinning Nuclear Magnetic Resonance  

SciTech Connect

A high-pressure magic angle spinning (MAS) NMR capability, consisting of a reusable high-pressure MAS rotor, a high-pressure loading/reaction chamber for in situ sealing and re-opening of the high-pressure MAS rotor, and a MAS probe with a localized RF coil for background signal suppression, is reported. The unusual technical challenges associated with development of a reusable high-pressure MAS rotor are addressed in part by modifying standard ceramics for the rotor sleeve to include micro-groves at the internal surface at both ends of the cylinder. In this way, not only is the advantage of ceramic cylinders for withstanding very high-pressure utilized, but also plastic bushings can be glued tightly in place so that other plastic sealing mechanisms/components and O-rings can be mounted to create the desired high-pressure seal. Using this strategy, sealed internal pressures exceeding 150 bars have been achieved and sustained under ambient external pressure with minimal penetration loss of pressure for 72 hours. As an application example, in situ 13C MAS NMR studies of mineral carbonation reaction intermediates and final products of forsterite (Mg2SiO4) reacted with supercritical CO2 and H2O at 150 bar and 50?C are reported, with relevance to geological sequestration of carbon dioxide.

Hoyt, David W.; Turcu, Romulus VF; Sears, Jesse A.; Rosso, Kevin M.; Burton, Sarah D.; Felmy, Andrew R.; Hu, Jian Z.

2011-10-01

209

High-pressure magic angle spinning nuclear magnetic resonance.  

PubMed

A high-pressure magic angle spinning (MAS) NMR capability, consisting of a reusable high-pressure MAS rotor, a high-pressure rotor loading/reaction chamber for in situ sealing and re-opening of the high-pressure MAS rotor, and a MAS probe with a localized RF coil for background signal suppression, is reported. The unusual technical challenges associated with development of a reusable high-pressure MAS rotor are addressed in part by modifying standard ceramics for the rotor sleeve by abrading the internal surface at both ends of the cylinder. In this way, not only is the advantage of ceramic cylinders for withstanding very high-pressure utilized, but also plastic bushings can be glued tightly in place so that other removable plastic sealing mechanisms/components and O-rings can be mounted to create the desired high-pressure seal. Using this strategy, sealed internal pressures exceeding 150 bars have been achieved and sustained under ambient external pressure with minimal loss of pressure for 72 h. As an application example, in situ(13)C MAS NMR studies of mineral carbonation reaction intermediates and final products of forsterite (Mg(2)SiO(4)) reacted with supercritical CO(2) and H(2)O at 150 bar and 50°C are reported, with relevance to geological sequestration of carbon dioxide. PMID:21862372

Hoyt, David W; Turcu, Romulus V F; Sears, Jesse A; Rosso, Kevin M; Burton, Sarah D; Felmy, Andrew R; Hu, Jian Zhi

2011-10-01

210

Synthesis and carbon-13 NMR studies of liquid crystals  

NASA Astrophysics Data System (ADS)

The orientation of different segments of 4'-cyanophenyl 4-heptylbenzoate (7CPB) has been investigated using 13C NMR. The method of proton encoded local field (PELF) spectroscopy was used in combination with off-magic-angle spinning (OMAS) of the sample. High-resolution 2D spectra were obtained and the order parameters were calculated from the spectra. Linear relationships between the obtained order parameters and anisotropic chemical shifts determined by 1D 13C NMR were established and semi-empirical parameters were obtained. A 1:2 mixture of 7CPB and its chain-perfluorinated analog (7PFCPB) shows interesting phase behavior with changing of temperature. The mixture was studied by the use of 13C NMR and polarizing optical microscopy. The order parameters of 7CPB in the smectic A phase of the mixture were calculated using the semi-empirical parameters obtained by the 2D NMR method. Eight series of liquid crystals containing an electron- donating group at one end of a conjugated system and an electron-withdrawing group at the other end have been synthesized. The electron-donating group is 4- n-alkylpiperazinyl group, the electron- withdrawing group is nitro group and the conjugated system is diphenyldiazene with zero, one or two substituents on the phenyl rings. The substituents are -F, -Cl, and -CH3. Two series of compounds with cyano group as electron-withdrawing group were also synthesized. Most of the compounds synthesized are nematogenic and exhibit rather broad liquid crystalline ranges. The effects of the lateral substituents on the optical absorption and phase transition temperatures are correlated with their nature and position of substitution. Birefringence, dielectric anisotropy, elastic constant ratio and rise time of the liquid crystals were carried out using 10 wt% LC mixtures in E7. It has been found that lateral substituents have subtle effects on the properties. The presence of lateral substituents depresses melting points and clearing points of the liquid crystals. All the liquid crystals synthesized in this work have relatively large values of birefiringence, although the dielectric anisotropy values were not as high as desired. The incorporation of a fluorine atom onto the position neighboring the nitro group enhances the conjugation of the push-pull system and liquid crystals with better physical properties were obtained.

Sun, Hong

2000-08-01

211

Spin- and phase transition in the spin crossover complex [Fe(ptz) 6](BF 4) 2 studied by nuclear inelastic scattering of synchrotron radiation and by DFT calculations  

NASA Astrophysics Data System (ADS)

Nuclear inelastic scattering (NIS) spectra of [Fe(ptz) 6](BF 4) 2 (ptz = 1- n-propyl-tetrazole) have been measured for five phases differing in spin state and crystallographic structure. Different spectral patterns have been found for the low-spin and high-spin phases and are described in terms of normal coordinate analysis of the complex molecule. For both low-spin and high-spin phases the conversion from ordered to disordered phase results in splitting of the observed NIS bands. Packing becomes visible in the NIS spectra via coupling of the Fe-N stretching vibrations with those of the terminal n-propyl groups. The DFT-based normal coordinate analysis also reveals the character of Raman markers.

Böttger, Lars H.; Chumakov, Aleksandr I.; Matthias Grunert, C.; Gütlich, Philipp; Kusz, Joachim; Paulsen, Hauke; Ponkratz, Ulrich; Rusanov, Ventzislav; Trautwein, Alfred X.; Wolny, Juliusz A.

2006-09-01

212

The nuclear spin lattice relaxation rate in the PuMGa5 materials  

NASA Astrophysics Data System (ADS)

We examine the nuclear spin-lattice relaxation rates 1/T1 of PuRhGa5 and PuCoGa5, in particular, in normal state. PuRhGa5 exhibits a gradual suppression of (T1T)-1 below 25 K far above Tc˜8.5 K, while measurements for PuCoGa5 reveal a monotonic increase down to Tc. We propose that this behavior is consistently understood by the crossover from the two-dimensional quantum antiferromagnetic regime of the local 5f-electron spins of Pu to the concomitant formation of the fermion pseudogap based on the two-component spin-fermion model.

Bang, Yunkyu; Graf, M. J.; Curro, N. J.; Balatsky, A. V.

2007-03-01

213

Optically induced nuclear spin polarization in a single GaAs/AlGaAs quantum well probed by a resistance detection method in the fractional quantum Hall regime  

NASA Astrophysics Data System (ADS)

We study the optically pumped nuclear spin polarization in a single GaAs/AlGaAs quantum well in the quantum Hall system. We apply resistive detection via the contact hyperfine interaction, which provides high sensitivity and selectivity, to probe a small amount of polarized nuclear spins in a single well. The properties of the optical nuclear spin polarization are clearly observed. We theoretically discuss the nuclear spin dynamics accompanied with doped electrons to analyze the experimental data. The optical nuclear polarization spectra exhibit electron-spin-resolved lowest Landau level interband transitions. We find that the phonon emission process, which normally assists the optical pumping process, influences the optical nuclear spin polarization. We also discuss that the electron-electron interaction can play an important role in the optical nuclear spin polarization.

Akiba, K.; Yuge, T.; Kanasugi, S.; Nagase, K.; Hirayama, Y.

2013-06-01

214

Fluctuation-Induced Heat Release from Temperature-Quenched Nuclear Spins near a Quantum Critical Point  

NASA Astrophysics Data System (ADS)

The quasi-two-dimensional quantum antiferromagnet Cr(diethylenetriamine)(O2)2.H2O [1] has a magnetic-field-tuned quantum critical point (QCP) at 12.3 T, where a highly polarized antiferromagnetic phase turns into a field-induced ferromagnetic phase. We report a novel relaxation phenomenon near this QCP: quantum-fluctuation-driven annealing of hydrogen nuclear spins frozen in a non-equilibrium high-energy state by temperature quenching. This relaxation phenomenon, with readily detectable heat release from the nuclear spins as they are annealed, reveals the extent of a quantum critical region around the QCP and provides a unique avenue to investigate the dynamics of the divergent quantum fluctuations that underlie quantum criticality. [1] C. M. Ramsey et al., Chem. Mater. 15, 92 (2003).

Kim, Y. H.; Kaur, N.; Atkins, B. M.; Dalal, N. S.; Takano, Y.

2010-03-01

215

Frozen spin solid targets developed at the Laboratory of Nuclear Problems (JINR, Dubna)  

NASA Astrophysics Data System (ADS)

Experience with polarized targets and achieving of very low temperatures gave rise to the idea of using a new technique based on dissolving 3He in 4He to create a frozen spin polarized target. The short history of the development of such proton and deuteron targets at the Laboratory of Nuclear Problems (LNP) JINR is given. Recently, the Saclay-Argonne frozen spin proton polarized target used initially in E704 experiment at FERMILAB was upgraded with adding the missing parts and the first physics experiments was carried out. At present, a new project is being proposed. The aim of this project is the development of effective methods of production 6LiD irradiated material for a large volume polarized deuteron target with a high polarization. The research will be carried out with use of the microtron of Czech Technical University for irradiation and the existing polarized target at Charles University Nuclear Centre for tests of the target materials.

Borisov, N. S.; Fedorov, A. N.; Lazarev, A. B.; Matafonov, V. N.; Neganov, A. B.; Plis, Y. A.; Shilov, S. N.; Usov, Y. A.; Bazhanov, N. A.; Kovalev, A. I.; Gurevich, G. M.; Dzyubak, A. P.; Karnaukhov, I. M.; Lukhanin, A. A.; ?erny, J.; Wilhelm, I.; Janout, Z.; Šimane, C.; Vognar, M.; Ball, J.; Durand, G.; Lehar, F.; Sans, J.-L.

2000-01-01

216

Proton-decoupled, Overhauser-enhanced, spatially localized carbon-13 spectroscopy in humans  

SciTech Connect

Spatially localized, natural abundance, carbon (13C) NMR spectroscopy has been combined with proton (1H) decoupling and nuclear Overhauser enhancement to improve 13C sensitivity up to five-fold in the human leg, liver, and heart. Broadhand-decoupled 13C spectra were acquired in 1 s to 17 min with a conventional 1.5-T imaging/spectroscopy system, an auxiliary 1H decoupler, an air-cooled dual-coil coplanar surface probe, and both depth-resolved surface coil spectroscopy (DRESS) and one-dimensional phase-encoding gradient NMR pulse sequences. The surface coil probe comprised circular and figure-eight-shaped coils to eliminate problems with mutual coupling of coils at high decoupling power levels applied during 13C reception. Peak decoupler RF power deposition in tissue was computed numerically from electromagnetic theory assuming a semi-infinite plane of uniform biological conductor. Peak values at the surface were calculated at 4 to 6 W/kg in any gram of tissue for each watt of decoupler power input excluding all coil and cable losses, warning of potential local RF heating problems in these and related experiments. The average power deposition was about 9 mW/kg per watt input, which should present no systemic hazard. At 3 W input, human 13C spectra were decoupled to a depth of about 5 cm while some Overhauser enhancement was sustained up to about 3 cm depth, without ill effect. The observation of glycogen in localized natural abundance 13C spectra of heart and muscle suggests that metabolites in the citric acid cycle should be observable noninvasively using 13C-labeled substrates.

Bottomley, P.A.; Hardy, C.J.; Roemer, P.B.; Mueller, O.M. (GE Corporate Research and Development Center, Schenectady, NY (USA))

1989-12-01

217

Proton-decoupled, Overhauser-enhanced, spatially localized carbon-13 spectroscopy in humans.  

PubMed

Spatially localized, natural abundance, carbon (13C) NMR spectroscopy has been combined with proton (1H) decoupling and nuclear Overhauser enhancement to improve 13C sensitivity up to five-fold in the human leg, liver, and heart. Broadhand-decoupled 13C spectra were acquired in 1 s to 17 min with a conventional 1.5-T imaging/spectroscopy system, an auxiliary 1H decoupler, an air-cooled dual-coil coplanar surface probe, and both depth-resolved surface coil spectroscopy (DRESS) and one-dimensional phase-encoding gradient NMR pulse sequences. The surface coil probe comprised circular and figure-eight-shaped coils to eliminate problems with mutual coupling of coils at high decoupling power levels applied during 13C reception. Peak decoupler RF power deposition in tissue was computed numerically from electromagnetic theory assuming a semi-infinite plane of uniform biological conductor. Peak values at the surface were calculated at 4 to 6 W/kg in any gram of tissue for each watt of decoupler power input excluding all coil and cable losses, warning of potential local RF heating problems in these and related experiments. The average power deposition was about 9 mW/kg per watt input, which should present no systemic hazard. At 3 W input, human 13C spectra were decoupled to a depth of about 5 cm while some Overhauser enhancement was sustained up to about 3 cm depth, without ill effect. The observation of glycogen in localized natural abundance 13C spectra of heart and muscle suggests that metabolites in the citric acid cycle should be observable noninvasively using 13C-labeled substrates. PMID:2560801

Bottomley, P A; Hardy, C J; Roemer, P B; Mueller, O M

1989-12-01

218

Nuclear Ground State Spins of the Francium Isotopes 208-213, 220-222Fr  

Microsoft Academic Search

The nuclear ground state spins of some francium isotopes have been measured using on-line atomic-beam magnetic resonance techniques. The following results have been obtained: 208Fr I = 7, 209Fr I = 9\\/2, 210Fr I = 6, 211Fr I = 9\\/2, 212Fr I = 5, 213Fr I = 9\\/2, 220Fr I = 1, 221Fr I = 5\\/2 and 222Fr I =

C. Ekström; S. Ingelman; G. Wannberg; M. Skarestad

1978-01-01

219

Diamond as a Solid State Quantum Computer with a Linear Chain of Nuclear Spins System  

NASA Astrophysics Data System (ADS)

By removing a $^{12}C$ atom from the tetrahedral configuration of the diamond, replace it by a $^{13}C$ atom, and repeating this in a linear direction, it is possible to have a linear chain of nuclear spins one half and to build a solid state quantum computer. One qubit rotation and controlled-not (CNOT) quantum gates are obtained immediately from this configuration, and CNOT quantum gate is used to determined the design parameters of this quantum computer.

López, G. V.; López, G. V.

220

Nuclear-spin relaxation of ²º?Pb in ferroelectric powders  

SciTech Connect

The ²º?Pb nuclear system (nuclear spin I = 1/2; magnetic Moment ? ?0.58 ?N; isotopic abundance ? 22%) in ferroelectric solids has been proposed for a search for a Schiff moment associated with simultaneous violation of parity (P) and time-reversal invariance (T) in fundamental interactions [1] (see also a discussion of the sensitivity of such search in Ref. [2]). The idea is that, due to the Schiff moment, a ferroelectric sample would acquire a P,T-odd magnetic polarization along the direction of its electric polarization. In conclusion, we have presented the first experimental study of relaxation properties of ²º?Pb in PT and PZT below room temperature. We find that above T? 50 K, longitudinal relaxation rate follows the T² dependence characteristic of the two-phonon Raman process. On the other hand, as the temperature is decreased below T? 50 K, the longitudinal relaxation rates drop slower than ?T2 (as opposed to ?T7 expected for the Raman process), and the relaxation is probably due to a direct process associated with paramagnetic impurities and nuclear-spin diffusion. While the longitudinal relaxation times T? vary between several seconds and over an hour in the temperature range between 290 and 10 K, the transverse relaxation time T? is found to be ?1.5 ms for all temperatures and all powder samples studied. D: we never discuss the origin of T? relaxation. Maybe we should. 1.5 ms is only a bit shorter from what would be expected from nuclear spin-spin interactions. Any comments? At some point Sasha asked Oleg to calculate T? exactly for PT and PZT, but I forgot what was the result. If such calculation exists, it would be great to compare with the expt. result. The obtained results provide an important input in the design of the experiments to search for P,T-violating effects in solid ferroelectrics

Bouchard, Louis S.; Sushkov, Alexander O.; Budker, Dmitry; Ford, Joe; Lipton, Andrew S.

2008-02-05

221

Nuclear tetrahedral states and high-spin states studied using the quantum number projection method  

NASA Astrophysics Data System (ADS)

We have recently developed an efficient method for performing the full quantum number projection from the most general mean-field (Hartree–Fock–Bogoliubov-type) wavefunctions including the angular momentum and parity, as well as the proton and neutron particle numbers. With this method, we have investigated several nuclear structure mechanisms. In this paper, we discuss the quantum rotational spectra obtained for the tetrahedral nuclear states, formulating certain experimentally verifiable criteria for the high-spin states, focusing on the wobbling bands and chiral bands, and for the drip-line nuclei, as illustrative examples.

Tagami, S.; Shimada, M.; Fujioka, Y.; Shimizu, Y. R.; Dudek, J.

2014-05-01

222

Nuclear spin singlet states as a contrast mechanism for NMR spectroscopy.  

PubMed

Nuclear magnetic resonance (NMR) spectra of complex chemical mixtures often contain unresolved or hidden spectral components, especially when strong background signals overlap weaker peaks. In this article we demonstrate a quantum filter utilizing nuclear spin singlet states, which allows undesired NMR spectral background to be removed and target spectral peaks to be uncovered. The quantum filter is implemented by creating a nuclear spin singlet state with spin quantum numbers j?=?0,?mz ?=?0 in a target molecule, applying a continuous RF field to both preserve the singlet state and saturate the magnetization of undesired molecules and then mapping the target molecule singlet state back into an NMR observable state so that its spectrum can be read out unambiguously. The preparation of the target singlet state can be carefully controlled with pulse sequence parameters, so that spectral contrast can be achieved between molecules with very similar structures. We name this NMR contrast mechanism 'Suppression of Undesired Chemicals using Contrast-Enhancing Singlet States' (SUCCESS) and we demonstrate it in vitro for three target molecules relevant to neuroscience: aspartate, threonine and glutamine. PMID:23606451

Devience, Stephen J; Walsworth, Ronald L; Rosen, Matthew S

2013-10-01

223

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

224

Coupling of the Larmor precession to the correlated motion of pairs of nuclear spins in noble metals  

SciTech Connect

The coupling of the Larmor line to pairs of nuclear spins being flipped by one photon is studied for the nuclear-spin system in the noble metals. The coupling parameter has been evaluated using the spherical model. The separation of the NMR frequencies of the Larmor line and the double-spin-flip line is calculated. The anticrossing feature in the Larmor-line frequency due to the coupling of the two modes is calculated in order to determine if the strength of the Ruderman-Kittel exchange interaction can be measured in Ag and Au.

Moyland, P.L.; Kumar, P.; Xu, J.; Takano, Y. (Department of Physics and Center for Ultralow Temperature Physics, University of Florida, Gainesville, Florida 32611 (United States))

1993-11-01

225

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

226

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 ?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 VF; Hoyt, David W.; Rosso, Kevin M.; Sears, Jesse A.; Loring, John S.; Felmy, Andrew R.; Hu, Jian Z.

2013-01-01

227

Dynamic evolution for liquid-state nuclear spins and Berry phase of mixed state in a magnetic resonance  

NASA Astrophysics Data System (ADS)

Dynamic evolution for liquid-state nuclear spin in a magnetic resonance is investigated based on Bloch sphere structure under the time-dependent modified Bloch equation. We show that the magnetization is related to the magnetic field strength but approximately independent of the initial unpolarized spin state after a very short evolving time. We predict that the Berry phase transition of the nuclear spin system take place in a quasicyclic evolution for some initial states, resulting in that the evolving memory of nuclear spin polarization is kept in terms of the Berry phase. The findings provide another clue to search for quantum memory devices in such a system on the basis of the geometric phase.

Xu, Hualan; Fu, Dan; Wang, Z. S.; Pan, Hui

2012-10-01

228

Improvements in carbon-13 broadband homonuclear cross-polarization for 2D and 3D NMR  

NASA Astrophysics Data System (ADS)

We describe a new multiple-pulse sequence (FLOPSY-8) for broadband homonuclear cross-polarization and compare it both theoretically and experimentally with the previous state of the art. FLOPSY-8 offers significant improvements in cross-polarization efficiency compared with the best alternative, and is especially useful for the large spectral bandwidths encountered in highfield carbon-13 NMR.

Mohebbi, A.; Shaka, A. J.

1991-03-01

229

Carbon-13 depletion in a hydrothermal vent mussel: suggestion of a chemosynthetic food source.  

PubMed

Tissues of a mytilid mussel from the Clambake I hydrothermal vent in the Galápagos 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. PMID:17813375

Rau, G H; Hedges, J I

1979-02-16

230

Carbon 13 Measurements on Dissolved Inorganic Carbon at the North Pacific (1969) E Secs Statio n.  

National Technical Information Service (NTIS)

Samples from 22 depths at the Geosecs station were measured for carbon 13 independently at Scripps Institution of Oceanography and Woods Hole Institution of Oceanography. The mean deviation between the two sets of data is -0.02 pH scale and the absolute d...

P. Kroopnick W. G. Deuser H. Craig

1970-01-01

231

Ignition conditions for inertial confinement fusion targets with a nuclear spin-polarized DT fuel  

NASA Astrophysics Data System (ADS)

The nuclear fusion cross-section is modified when the spins of the interacting nuclei are polarized. In the case of deuterium-tritium it has been theoretically predicted that the nuclear fusion cross-section could be increased by a factor ? = 1.5 if all the nuclei were polarized. In inertial confinement fusion this would result in a modification of the required ignition conditions. Using numerical simulations it is found that the required hot-spot temperature and areal density can both be reduced by about 15% for a fully polarized nuclear fuel. Moreover, numerical simulations of a directly driven capsule show that the required laser power and energy to achieve a high gain scale as ?-0.6 and ?-0.4 respectively, while the maximum achievable energy gain scales as ?0.9.

Temporal, M.; Brandon, V.; Canaud, B.; Didelez, J. P.; Fedosejevs, R.; Ramis, R.

2012-10-01

232

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

233

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

234

Frozen spin solid targets developed at the Laboratory of Nuclear Problems (JINR, Dubna)  

NASA Astrophysics Data System (ADS)

Experience with polarized targets [1,2] and achieving of very low temperatures in 1966 at the Laboratory of Nuclear Problems [3] and by another group [4] gave rise to the idea of using a radically new technique based on dissolving 3He in 4He to create a frozen spin polarized target. The short history of the development of such proton and deuteron targets at the LNP is given. The complex Cr(V) compounds in diols are used as target operating material. A characteristic feature of these targets is a long relaxation time (˜ 1000h) in magnetic fields of about 0.5 T. Lately, the Saclay-Argonne frozen spin proton polarized target used initially in E704 experiment at FERMILAB has been upgraded with adding the missing parts and the first physics experiment has been carried out.

Bazhanov, N. A.; Benda, B.; Borisov, N. S.; Durand, G.; Dzyubak, A. P.; Fedorov, A. N.; Golovanov, L. B.; Gurevich, G. M.; Karnaukhov, I. M.; Kovalev, A. I.; Lazarev, A. B.; Lehar, F.; Lukhanin, A. A.; Matafonov, V. N.; Neganov, A. B.; Plis, Yu. A.; Shilov, S. N.; Topalov, S. V.; Usov, Yu. A.

1998-02-01

235

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

236

Nuclear magnetic resonance, mass spectroscopic, and chromatographic characterization of narrow boiling distillates from a San Andres formation crude oil and a light Tensleep oil  

Microsoft Academic Search

Hydrogen (1H) and carbon (13C) high resolution nuclear magnetic resonance (NMR) spectroscopy, gas chromatography-mass spectroscopy (GC-MS), and high pressure liquid chromatography (HPLC) were used to determine the relative amounts of molecular functional groups in a series of narrow boiling range distillates from two crude oils. San Andres formation and Tensleep black oils were characterized. Spinning band distillation was used to

R. C. Stewart; D. W. Phelps; J. D. Parli; D. L. Crosby; J. R. Ball

1988-01-01

237

Selection rules for nuclear spin modifications in ion-neutral reactions involving H3+  

NASA Astrophysics Data System (ADS)

We present experimental evidence for nuclear spin selection rules in chemical reactions that have been theoretically anticipated by Quack [M. Quack, Mol. Phys. 34, 477 (1997)]. The abundance ratio of ortho-H3+ (I=3/2) and para-H3+ (I=1/2), R=[o-H3+]/[p-H3+], has been measured from relative intensities of their infrared spectral lines in hydrogen plasmas using para-H2 and normal-H2 (75% o-H2 and 25% p-H2). The observed clear differences in the value of R between the p-H2 and n-H2 plasmas demonstrate the spin memory of protons even after ion-neutral reactions, and thus the existence of selection rules for spin modifications. Both positive column discharges and hollow cathode discharges have been used to demonstrate the effect. Experiments using pulsed plasmas have been conducted in the hollow cathode to minimize the uncertainty due to long-term conversion between p-H2 and o-H2 and to study the time dependence of the o-H3+ to p-H3+ ratio. The observed R(t) has been analyzed using simultaneous rate equations assuming the nuclear spin branching ratios calculated from Quack's theory. In p-H2 plasmas, the electron impact ionization followed by the ion-neutral reaction H2++H2-->H3++H produces pure p-H3+, but the subsequent reaction between p-H3+ and p-H2 scrambles protons. While the proton hop reaction (rate constant kH) maintains the purity of p-H3+, the hydrogen exchange reaction (rate constant kE) produces o-H3+ and acts as the gateway for nuclear spin conversion. The value of R(t), therefore, depends critically on the ratio of their reaction rates ?=kH/kE. From observed values of R(t), the ratio has been determined to be ?=2.4. This is in approximate agreement with the value reported by Gerlich using isotopic species.

Cordonnier, M.; Uy, D.; Dickson, R. M.; Kerr, K. E.; Zhang, Y.; Oka, T.

2000-08-01

238

Comparison of different methods for calculating the paramagnetic relaxation enhancement of nuclear spins as a function of the magnetic field.  

PubMed

The enhancement of the spin-lattice relaxation rate for nuclear spins in a ligand bound to a paramagnetic metal ion [known as the paramagnetic relaxation enhancement (PRE)] arises primarily through the dipole-dipole (DD) interaction between the nuclear spins and the electron spins. In solution, the DD interaction is modulated mostly by reorientation of the nuclear spin-electron spin axis and by electron spin relaxation. Calculations of the PRE are in general complicated, mainly because the electron spin interacts so strongly with the other degrees of freedom that its relaxation cannot be described by second-order perturbation theory or the Redfield theory. Three approaches to resolve this problem exist in the literature: The so-called slow-motion theory, originating from Swedish groups [Benetis et al., Mol. Phys. 48, 329 (1983); Kowalewski et al., Adv. Inorg. Chem. 57, (2005); Larsson et al., J. Chem. Phys. 101, 1116 (1994); T. Nilsson et al., J. Magn. Reson. 154, 269 (2002)] and two different methods based on simulations of the dynamics of electron spin in time domain, developed in Grenoble [Fries and Belorizky, J. Chem. Phys. 126, 204503 (2007); Rast et al., ibid. 115, 7554 (2001)] and Ann Arbor [Abernathy and Sharp, J. Chem. Phys. 106, 9032 (1997); Schaefle and Sharp, ibid. 121, 5387 (2004); Schaefle and Sharp, J. Magn. Reson. 176, 160 (2005)], respectively. In this paper, we report a numerical comparison of the three methods for a large variety of parameter sets, meant to correspond to large and small complexes of gadolinium(III) and of nickel(II). It is found that the agreement between the Swedish and the Grenoble approaches is very good for practically all parameter sets, while the predictions of the Ann Arbor model are similar in a number of the calculations but deviate significantly in others, reflecting in part differences in the treatment of electron spin relaxation. The origins of the discrepancies are discussed briefly. PMID:18266432

Belorizky, Elie; Fries, Pascal H; Helm, Lothar; Kowalewski, Jozef; Kruk, Danuta; Sharp, Robert R; Westlund, Per-Olof

2008-02-01

239

Achievement of high nuclear spin polarization using lanthanides as low-temperature NMR relaxation agents.  

PubMed

Many approaches are now available for achieving high levels of nuclear spin polarization. One of these methods is based on the notion that as the temperature is reduced, the equilibrium nuclear polarization will increase, according to the Boltzmann distribution. The main problem with this approach is the length of time it may take to approach thermal equilibrium at low temperatures, since nuclear relaxation times (characterized by the spin-lattice relaxation time T1) can become very long. Here, we show, by means of relaxation time measurements of frozen solutions, that selected lanthanide ions, in the form of their chelates with DTPA, can act as effective relaxation agents at low temperatures. Differential effects are seen with the different lanthanides that were tested, holmium and dysprosium showing highest relaxivity, while gadolinium is ineffective at temperatures of 20 K and below. These observations are consistent with the known electron-spin relaxation time characteristics of these lanthanides. The maximum relaxivity occurs at around 10 K for Ho-DTPA and 20 K for Dy-DTPA. Moreover, these two agents show only modest relaxivity at room temperature, and can thus be regarded as relaxation switches. We conclude that these agents can speed up solid state NMR experiments by reducing the T1 values of the relevant nuclei, and hence increasing the rate at which data can be acquired. They could also be of value in the context of a simple low-cost method of achieving several-hundred-fold improvements in polarization for experiments in which samples are pre-polarized at low temperatures, then rewarmed and dissolved immediately prior to analysis. PMID:23588269

Peat, David T; Horsewill, Anthony J; Köckenberger, Walter; Perez Linde, Angel J; Gadian, David G; Owers-Bradley, John R

2013-05-28

240

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

241

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)], 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

242

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

PubMed

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)], 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. PMID:23534632

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

2013-03-21

243

Analytical theory of the nuclear-spin-induced optical rotation in liquids  

NASA Astrophysics Data System (ADS)

Based on the thought on the antisymmetric polarizability induced by nuclear magnetic moments and theory of the Faraday effect, an analytical theoretical expression is derived for the nuclear-spin-induced optical rotation (NSOR) of diamagnetic saturated molecules in a circular cylinder. That consists of two parts, ? and ?, induced by the intramolecular and intermolecular hyperfine interaction, respectively. By using them and the Verdet constants, NSOR for 1H in water, hexane, cyclohexane and methyl-alcohol in liquid and H 2 gas have been calculated. The calculated NSOR for water agrees with the experiment and for three hydrocarbons predicts the same order of magnitude as water. For the samples studied except H 2 gas, ? and ? are comparable in magnitude.

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

2011-08-01

244

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

245

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

NASA Astrophysics Data System (ADS)

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.

Davesne, D.; Pastore, A.; Navarro, J.

2014-04-01

246

Energy-Level Related Nuclear-Spin Effects and Super-Hyperfine Spectral Patterns: how Molecules do Self-Nmr  

NASA Astrophysics Data System (ADS)

At several points in his defining works on molecular spectroscopy, Herzberg notes that ``because nuclear moments ldots are so very slight ldots transitions between species ldots are very strictly forbiddenldots '' Herzberg's most recent statement of such selection rules pertained to spherical top spin-species. It has since been shown that spherical top species (as well as those of lower symmetry molecules) converge exponentially with momentum quanta J and K to degenerate level clusters wherein even ``very slight'' nuclear fields and moments cause pervasive resonance and total spin species mixing. Ultra-high resolution spectra of Borde, et .al and Pfister et .al shows how SF_6 and SiF_4 Fluorine nuclear spin levels rearrange from total-spin multiplets to NMR-like patterns as their superfine structure converges. Similar super-hyperfine effects are anticipated for lower symmetry molecules exhibiting converging superfine level-clusters. Examples include PH_3 molecules and asymmetric tops. Following this we consider models that treat nuclear spins as coupled rotors undergoing generalized Hund-case transitions from spin-lab-momentum coupling to various spin-rotor correlations. G. A. Herzberg, Electronic Spectra of Polyatomic Molecules, (Von Norstrand Rheinhold 1966) p. 246. W G. Harter and C. W Patterson, Phys. Rev. A 19, 2277 (1979) W. G. Harter, Phys. Rev. A 24, 192 (1981). Ch. J. Borde, J. Borde, Ch. Breant, Ch. Chardonnet, A. Van Lerberghe, and Ch. Salomon, in Laser Spectroscopy VII, T. W Hensch and Y. R. Shen, eds. (Springer-Verlag, Berlin, 1985). O. Pfister, F. Guernet, G. Charton, Ch. Chardonnet, F. Herlemont, and J. Legrand, J. Opt. Soc. Am. B 10, 1521 (1993). O. Pfister, Ch. Chardonnet, and Ch. J. Bordè, Phys. Rev. Lett. 76, 4516 (1996) S. N. Yurchenko, W. Thiel, S. Patchkovskii, and P. Jensen, Phys. Chem. Chem. Phys.7, 573 (2005)

Harter, William; Mitchell, Justin

2009-06-01

247

Experimental evidence for ferromagnetic spin-pairing superconductivity emerging in UGe2 : A Ge73 -nuclear-quadrupole-resonance study under pressure  

Microsoft Academic Search

We report that a different type of superconducting order parameter has been realized in the ferromagnetic states in UGe2 via Ge73 -nuclear-quadrupole-resonance experiments performed under pressure (P) . Measurements of the nuclear spin-lattice relaxation rate (1\\/T1) have revealed an unconventional nature of superconductivity such that the up-spin band is gapped with line nodes, but the down-spin band remains gapless at

A. Harada; S. Kawasaki; H. Mukuda; Y. Kitaoka; Y. Haga; E. Yamamoto; Y. Onuki; K. M. Itoh; E. E. Haller; H. Harima

2007-01-01

248

Nuclear Spin of H_3^+ and H_2 in Dense Molecular Clouds  

NASA Astrophysics Data System (ADS)

The ortho:para ratio of H_2 is a critical parameter for deuterium fractionation in cold, dense quiescent cores. The dominant reservoir for interstellar deuterium is in the inert molecule HD, but the exothermic reaction H_3^+ + HD ? H_2D^+ + H_2 + 220 K (and H_2D^+ + HD, etc.) can yield highly reactive species capable of distributing deuterium to other molecules. The barrier to the reverse reaction, however, can be overcome even at temperatures below 10 K when ortho-H_2 (o-H_2) reacts with H_2D^+ (or D_2H^+, D_3^+), as ortho-H_2 possesses ˜170 K of internal rotational energy in its ground state. Recent modeling work has demonstrated the importance of o-H_2 in cold, dense, highly depleted cores using a chemical network that includes all nuclear spin modifications of H_3^+, H_2, and their isotopologues, but the initial o-H_2 fraction is taken as a parameter in the model. Observationally or computationally constraining this quantity would aid in understanding deuterium fractionation in dense cores. To learn about the initial o-H_2 fraction in a cold core, we have modeled the chemistry of non-depleted dense interstellar clouds from which cold cores are thought to form. A simplified gas-phase chemical network consisting of 28 species and ˜170 reactions is combined with a physical model of a dense cloud, including time-dependent physical conditions. Included in the network are the nuclear spin modifications of H_2, H_2^+, and H_3^+, as well as nuclear spin dependent rate coefficients for the thermalization reactions H_2 + H^+ and H_3^+ + H_2. By modeling the time-dependent chemistry, we find that the ortho:para ratio of H_2 requires 10^7-10^8 years to reach steady state under ``standard'' dense cloud conditions, which is at least on the order of the cloud lifetime. The timescale depends on the ionization rate, the rate coefficients of the various H_3^+ + H_2 reactions, and the relative abundances of H_3^+ and H^+, but is largely insensitive to the total density and temperature. Even at steady state, the o-H_2 fraction is calculated to be >0.5% at 10 K, which is several orders of magnitude above its value at thermodynamic equilibrium. The prospects for using observations of the ortho:para ratio of H_3^+ as a probe of the H_2 ortho:para ratio will be discussed.

Crabtree, Kyle N.; McCall, Benjamin J.

2012-06-01

249

Treatment of scalar-relativistic effects on nuclear magnetic shieldings using a spin-free exact-two-component approach  

NASA Astrophysics Data System (ADS)

A cost-effective treatment of scalar-relativistic effects on nuclear magnetic shieldings based on the spin-free exact-two-component theory in its one-electron variant (SFX2C-1e) is presented. The SFX2C-1e scheme gains its computational efficiency, in comparison to the four-component approach, from a focus on spin-free contributions and from the elimination of the small component. For the calculation of nuclear magnetic shieldings, the separation of spin-free and spin-dependent terms in the parent four-component theory is carried out here for the matrix representation of the Dirac equation in terms of a restricted-magnetically balanced gauge-including atomic orbital basis. The resulting spin-free four-component matrix elements required to calculate nuclear magnetic shieldings are then used to construct the corresponding SFX2C-1e Hamiltonian and its perturbed counterpart in the context of SFX2C-1e analytic derivative theory. To demonstrate the applicability of the approach, we report coupled-cluster calculations for prototypical problems such as the 17O shieldings of transition-metal oxo complexes (MO42-, M = Cr, Mo, and W) and the 129Xe shieldings of xenon fluorides (XeF2, XeF4, and XeF6).

Cheng, Lan; Gauss, Jürgen; Stanton, John F.

2013-08-01

250

Treatment of scalar-relativistic effects on nuclear magnetic shieldings using a spin-free exact-two-component approach.  

PubMed

A cost-effective treatment of scalar-relativistic effects on nuclear magnetic shieldings based on the spin-free exact-two-component theory in its one-electron variant (SFX2C-1e) is presented. The SFX2C-1e scheme gains its computational efficiency, in comparison to the four-component approach, from a focus on spin-free contributions and from the elimination of the small component. For the calculation of nuclear magnetic shieldings, the separation of spin-free and spin-dependent terms in the parent four-component theory is carried out here for the matrix representation of the Dirac equation in terms of a restricted-magnetically balanced gauge-including atomic orbital basis. The resulting spin-free four-component matrix elements required to calculate nuclear magnetic shieldings are then used to construct the corresponding SFX2C-1e Hamiltonian and its perturbed counterpart in the context of SFX2C-1e analytic derivative theory. To demonstrate the applicability of the approach, we report coupled-cluster calculations for prototypical problems such as the (17)O shieldings of transition-metal oxo complexes (MO4(2-), M = Cr, Mo, and W) and the (129)Xe shieldings of xenon fluorides (XeF2, XeF4, and XeF6). PMID:23927241

Cheng, Lan; Gauss, Jürgen; Stanton, John F

2013-08-01

251

Solid state nuclear magnetic resonance with magic-angle spinning and dynamic nuclear polarization below 25 K  

NASA Astrophysics Data System (ADS)

We describe an apparatus for solid state nuclear magnetic resonance (NMR) with dynamic nuclear polarization (DNP) and magic-angle spinning (MAS) at 20-25 K and 9.4 Tesla. The MAS NMR probe uses helium to cool the sample space and nitrogen gas for MAS drive and bearings, as described earlier [1], but also includes a corrugated waveguide for transmission of microwaves from below the probe to the sample. With a 30 mW circularly polarized microwave source at 264 GHz, MAS at 6.8 kHz, and 21 K sample temperature, greater than 25-fold enhancements of cross-polarized 13C NMR signals are observed in spectra of frozen glycerol/water solutions containing the triradical dopant DOTOPA-TEMPO when microwaves are applied. As demonstrations, we present DNP-enhanced one-dimensional and two-dimensional 13C MAS NMR spectra of frozen solutions of uniformly 13C-labeled L-alanine and melittin, a 26-residue helical peptide that we have synthesized with four uniformly 13C-labeled amino acids.

Thurber, Kent R.; Potapov, Alexey; Yau, Wai-Ming; Tycko, Robert

2013-01-01

252

Solid state nuclear magnetic resonance with magic-angle spinning and dynamic nuclear polarization below 25 K.  

PubMed

We describe an apparatus for solid state nuclear magnetic resonance (NMR) with dynamic nuclear polarization (DNP) and magic-angle spinning (MAS) at 20-25 K and 9.4 Tesla. The MAS NMR probe uses helium to cool the sample space and nitrogen gas for MAS drive and bearings, as described earlier, but also includes a corrugated waveguide for transmission of microwaves from below the probe to the sample. With a 30 mW circularly polarized microwave source at 264 GHz, MAS at 6.8 kHz, and 21 K sample temperature, greater than 25-fold enhancements of cross-polarized (13)C NMR signals are observed in spectra of frozen glycerol/water solutions containing the triradical dopant DOTOPA-TEMPO when microwaves are applied. As demonstrations, we present DNP-enhanced one-dimensional and two-dimensional (13)C MAS NMR spectra of frozen solutions of uniformly (13)C-labeled l-alanine and melittin, a 26-residue helical peptide that we have synthesized with four uniformly (13)C-labeled amino acids. PMID:23238592

Thurber, Kent R; Potapov, Alexey; Yau, Wai-Ming; Tycko, Robert

2013-01-01

253

In vivo carbon-13 nuclear magnetic resonance studies of heart metabolism.  

PubMed Central

Guinea pig heart metabolism was studied in vivo by 13C NMR at 20.18 MHz. High-quality proton-decoupled 13C NMR spectra with excellent signal-to-noise ratios and resolution could be obtained in 6 min. Natural-abundance spectra showed resonances that could be assigned to fatty acids, but glycogen was not seen. During intravenous infusion of D-[1-13C]glucose and insulin, the time course of myocardial glycogen synthesis was followed serially for up to 4 hr. Anoxia resulted in degradation of the labeled glycogen within 6 min and appearance of 13C label in lactic acid. Infusion of sodium [2-13C]acetate resulted in incorporation of label into the C-4, C-2, and C-3 positions of glutamate and glutamine, reflecting "scrambling" of the label expected from tricarboxylic acid cycle activity. Examination of the 31P NMR spectrum of the guinea pig heart in vivo demonstrated no change in the high-energy phosphates during the time periods of the 13C NMR experiments. Our studies indicate that 13C NMR is a unique non-destructive tool for the study of heart metabolism in vivo.

Neurohr, K J; Barrett, E J; Shulman, R G

1983-01-01

254

Carbon-13 nuclear magnetic resonance spectroscopic investigation of the Kiliani reaction  

SciTech Connect

The Kiliani reaction of D-arabinose with sodium (/sup 13/C)cyanide (or (/sup 13/C,/sup 15/N)cyanide) was studied by /sup 13/C NMR. The C-1 resonances of intermediates and products were observed as the reaction evolved. Intermediates were identified by addition of authentic samples to reaction solutions, interpretation of chemical shifts and coupling constants, and chemical experiments. Intermediates identified included cyanohydrins, amides, lactones, amidines, and an imidate. A discussion of the course of the reaction over the pH range 5.1 to 12.5 is presented. The final mannonate-to-gluconate ratio was shown to be a function of pH and not associated with the presence of certain metal ions. 2 figures, 1 table.

Blazer, R.M.; Whaley, T.W.

1980-07-16

255

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

256

Carbon13 nuclear magnetic resonance measurement of oil composition in single viable soybeans  

Microsoft Academic Search

High-resolution, natural abundance13C NMR spectra of intact, viable soybeans have been obtained by Fourier transform techniques. The spectra are interpreted in\\u000a terms of the relative concentrations of the major fatty acids present in the soybean triglycerides. This nondestructive analysis\\u000a is sufficiently fast and accurate to permit the selection of individual soybeans for use in a genetic breeding program designed\\u000a to

Jacob Schaefer; E. O. Stejskal

1974-01-01

257

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

PubMed

Sensors based on the nitrogen-vacancy defect in diamond are being developed to measure weak magnetic and electric fields at the nanoscale. However, such sensors rely on measurements of a shift in the Lamor frequency of the defect, so an accumulation of quantum phase causes the measurement signal to exhibit a periodic modulation. This means that the measurement time is either restricted to half of one oscillation period, which limits accuracy, or that the magnetic field range must be known in advance. Moreover, the precision increases only slowly (as T(-0.5)) with measurement time T (ref. 3). Here, we implement a quantum phase estimation algorithm on a single nuclear spin in diamond to combine both high sensitivity and high dynamic range. By achieving a scaling of the precision with time to T(-0.85), we improve the sensitivity by a factor of 7.4 for an accessible field range of 16 mT, or, alternatively, we improve the dynamic range by a factor of 130 for a sensitivity of 2.5 µT Hz(-1/2). Quantum phase estimation algorithms have also recently been implemented using a single electron spin in a nitrogen-vacancy centre. These methods are applicable to a variety of field detection schemes, and do not require quantum entanglement. PMID:22179568

Waldherr, G; Beck, J; Neumann, P; Said, R S; Nitsche, M; Markham, M L; Twitchen, D J; Twamley, J; Jelezko, F; Wrachtrup, J

2012-02-01

258

The Study of High Spin States in Nuclear Rotation by the Cranked Nilsson Strutinsky Model  

NASA Astrophysics Data System (ADS)

A heavy-ion reaction can populate nuclear states of very high angular momentum with values of the order of I = 60 achievable. The reaction produces such configurations with a considerable internal excitation, but the emission of a few neutrons reduces the excitation energy effectively while not decreasing the spin by much. At sufficiently high spin the pairing is destroyed completely and the rigid-body moment of inertia becomes a good approximation. Even in this regime, however, the single-particle structure remains important and shell effects can be studied in terms of a rotating phenomenological shell model. On the theoretical side the cranked Nilsson strutinsky model has proved to be a successful tool to describe rapidly rotating nucleus. Indeed, this model gives a microscopic description of the influence of rotation on single-particle motion. This paper will concentrate on introduction to the cranked Nilsson strutinsky model in details. First, we explain the cranking model and the rotating liquid-drop model, then introduce the shell correction method. Also, we describe terminating bands, which show a continuous transition from high collectivity to a pure particle-hole state.

Kardan, A.; Miri-Hakimabad, H.; Rafat-Motevalli, L.

2010-11-01

259

Theoretical study of the nuclear spin-molecular rotation coupling for relativistic electrons and non-relativistic nuclei  

NASA Astrophysics Data System (ADS)

A theoretical study of the relation between the relativistic formulation of the nuclear magnetic shielding and spin-rotation tensors is presented. To this end a theoretical expression of the relativistic spin-rotation tensor is formulated, considering a molecular Hamiltonian of relativistic electrons and non-relativistic nuclei. Molecular rotation effects are introduced considering the terms of the Born-Oppenheimer decomposition, which couple the electrons and nuclei dynamics. The loss of the simple relation linking both spectral parameters in the non-relativistic formulation is further analyzed carrying out a perturbative expansion of relativistic effects by means of the linear response within the elimination of the small component approach. It is concluded that relativistic effects on the spin-rotation tensor are less important than those of the nuclear magnetic shielding tensor.

Aucar, Ignacio A.; Gómez, Sergio S.; de Azúa, Martín C. Ruiz; Giribet, Claudia G.

2012-05-01

260

Nuclear Spins, Hyperfine Structures, and Nuclear Moments of Scandium46 and Yttrium91  

Microsoft Academic Search

The atomic-beam magnetic-resonance method has been used to study some atomic and nuclear properties of 84-day Sc46 and 58-day Y91. The results are 2D32 2D52 Sc46 I=4 gJ=-0.7990(8) gJ=-1.1995(18) (muI)uncorr=+3.03(2) nm a=+150.576(9) Mc\\/sec a=+60.906(4) Mc\\/sec Quncorr=+0.119(6) b b=+14.38(14) Mc\\/sec b=+20.41(10) Mc\\/sec Y91 I=12 a=+\\/-68.34(2) Mc\\/sec a=+\\/-34.35(3) Mc\\/sec (muI)uncorr=+\\/-0.1634(8) nm Deltanu=+\\/-136.69(3) Mc\\/sec Deltanu=+\\/-103.05(4) Mc\\/sec

F. Russell Petersen; Howard A. Shugart

1962-01-01

261

Laboratory Scale Vacuum Energy Extraction Modeled on Weak Nuclear Force Reactions in a Spinning Black Hole System  

Microsoft Academic Search

A spinning black hole with accreting disk of matter and axially directed jet(s) of ejecta may promote a catalytic process of vacuum energy extraction by weak nuclear force reactions. This process would have profound cosmological implications and offers rationale for a luminosity mechanism in jets, anti-matter emission in jets, disrupted regions in jets, and some deep space gamma emission peaks.

Joseph J. Roser

1999-01-01

262

Deuterium isotope effects on the carbon-13 chemical shifts of carbocations  

SciTech Connect

The deuterium isotope effect on the carbon-13 NMR spectrum of several carbocations and neutral molecules have been examined. The carbon-13 resonance of the cationic carbon atom in the heavy isotopomer of the carbocations was found to be shifted upfield, to be unaffected, or to be shifted downfield, upon ..beta..-deuteration from the corresponding carbon in the nondeuterated compound. These effects ranged from -2.5 ppm to +1.6 ppm and were found to be consistent with previous work of Servis and Shue. The two bond chemical shift isotope effects determined for 2-methyl-2-norbornyl cation and for 2-(3,5-bis-(trifluoromethyl)-phenyl)-2-norbornyl cation provide evidence for partial delocalization of positive charge away from C2 into a three-center two-electron bond. The deuterium isotope effects determined for the 2-(p-fluorophenyl)-2-norbornyl cation and the 2-phenyl-2-norbornyl cation provide evidence about the stereochemical dependence of the two bond chemical shift isotope effect. The effect of exo C3 deuterium substitution on the C2-resonance in the carbon-13 NMR spectrum of the 2-(p-fluorophenyl)-2-norbornyl cation and the 2-phenyl-2-norbornyl cation is small and positive while the effect of endo C3 deuterium substitution is small and negative. This is the first case reported in which stereochemically distinct isotope effects at the same carbon are of opposite sign. The two bond chemical shift isotope effects determined for 2,3-dimethyl-2-butene bromonium ion and for 2,3-dimethyl-2-butene mercurinium ion permit the elucidation of the electronic structure of these cations.

Domenick, R.L.

1985-01-01

263

Optimized basis sets for the calculation of indirect nuclear spin-spin coupling constants involving the atoms B, Al, Si, P, and Cl  

NASA Astrophysics Data System (ADS)

The aug-cc-pVTZ-J series of basis sets for indirect nuclear spin-spin coupling constants has been extended to the atoms B, Al, Si, P, and Cl. The basis sets were obtained according to the scheme previously described by Provasi et al. [J. Chem. Phys. 115, 1324 (2001)]. First, the completely uncontracted correlation consistent aug-cc-pVTZ basis sets were extended with four tight s and three tight d functions. Second, the s and p basis functions were contracted with the molecular orbital coefficients of self-consistent-field calculations performed with the uncontracted basis sets on the simplest hydrides of each atom. As a first illustration, we have calculated the one-bond indirect spin-spin coupling constants in BH4-, BF, AlH, AlF, SiH4, SiF4, PH3, PF3, H2S, SF6, HCl, and ClF at the level of density functional theory using the Becke three parameter Lee-Yang-Parr and the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes.

Provasi, Patricio F.; Sauer, Stephan P. A.

2010-08-01

264

Carbon-13 magnetic resonance of hydrocarbons. Progress report, September 1, 1978-28 February 1981  

SciTech Connect

Carbon-13 and proton nmr data have been required for the following series of compounds: tetralin and sixteen of its methylated derivatives; eleven methylated tetrahydrophenanthrene which include the parent compound; and 9,10-dihydrophenanthrene and four of its 9,10 methylated isomers. Data for all these compounds are provided and a detailed discussion on their molecular structure from the chemical shift studies is presented. The temperature dependence of the solution chemical shifts of various methylated derivatives of tetralin has also been determined in CDCL/sub 4/ from 40/sup 0/C to -65/sup 0/C.

Dalling, D.K.; Morin, F.

1981-01-01

265

Deuterium/protium fractionation factors for polyfunctional organic molecules: direct determination by carbon-13 NMR spectroscopy  

SciTech Connect

The isotope exchange processes between water and readily exchangeable groups (e.g., OH, NH, and SH) are of interest in studying reaction mechanisms and elucidating the structural dynamics of biological macromolecules. A knowledge of the equilibrium partitioning of deuterium and protium between the different types of exchangeable hydrogens is needed for a detailed interpretation of kinetic and equilibrium data and for the understanding of these processes. This paper describes a method for the direct determination of fractionation factors from the integrated intensities of the carbon-13 resonances of deuterio and protio species under conditions of slow chemical exchange.

Reuben, J.

1986-03-05

266

Fractionated Mercury Isotopes in Fish: The Effects of Nuclear Mass, Spin, and Volume  

NASA Astrophysics Data System (ADS)

Mercury is long known as a common environmental contaminant. In methylated form it is even more toxic and the methylation process is facilitated by microbial activities. Methyl mercury easily crosses cell membrane and accumulates in soft tissues of fishes and finally biomagnifies with increasing trophic levels. Natural variations in the isotopic composition of mercury have been reported and such variations have emphasized mass dependent fractionations, while theory and laboratory experiments indicate that mass-independent isotopic fractionation (MIF) effects are likely to be found as well. This study focuses on the MIF of mercury isotopes in the soft tissues of fishes. Samples include both fresh water and marine fish, from different continents and oceans. Approximately 1 gm of fish soft tissue was dissolved in 5 ml of conc. aqua regia for 24 hrs and filtered through a ¬¬¬100 ?m filter paper and diluted with DI water. Hg is measured as a gaseous phase generated by reduction of the sample with SnCl2 in a continuous- flow cold-vapor generator connected to a Thermo-Finnigan Neptune MC-ICPMS. To minimize instrumental fractionation isotope ratios were measured by sample standard bracketing and reported as ?‰ relative to NIST SRM 3133 Hg standard where ?AHg = [(A Hg/202Hg)sample/(A Hg/202Hg)NIST313] -1 ×1000‰. In this study we have measured the isotope ratios 198Hg/202Hg, 199Hg/202Hg, 200Hg/202Hg, 201Hg/202Hg and 204Hg/202Hg. In all the fish samples ?198Hg, ?200Hg, ?202Hg, ?204Hg define a mass- dependent fractionation sequence, where as the ?199Hg and ?201Hg depart from the mass- dependent fractionation line and indicate an excess of the odd-N isotopes. The magnitude of the deviation (?AHg where A=199 or 201) as obtained by difference between the measured ?199Hg and ?201Hg of the samples and the value obtained by linear scaling defined by the even-N isotopes ranges from approximately 0.2 ‰ to 3‰. The ratios of ?199Hg /?201Hg range from 0.8 to 1.3, and thus more than one mass-independent isotope effect is inferred. MIF of mercury can be caused by the nuclear volume effect. Schauble, 2007 has calculated nuclear volume fractionation scaling factors for a number of common mercury chemical species in equilibrium with Hg° vapor. From his calculations the nuclear field shift effect is larger in ?199Hg than in ?201Hg by approximately a factor of two. The predominant mercury chemical species in fish is methylmercury cysteine. From the experimental studies of Buchachenko and others (2004) on the reaction of methylmercury chloride with creatine kinase it seems reasonable to predicted that the thiol functional groups of cysteine gets enriched in 199Hg and 201Hg. Here the magnetic isotope effect (MIE) produces a kinetic partial separation of isotopes with non-zero nuclear spin quantum numbers from the even-N isotopes. The ratio of enrichment of ?201Hg /?199Hg is predicted from theory to be 1.11, which is the ratio of the magnetic moments of 199Hg and 201Hg. Because mercury possesses two odd-N isotopes, it is possible to detect and evaluate the effects of two distinct, mass-independent isotope fractionating processes. From the data obtained on fish samples, we can deconvolute the contributions of the isotope effects of nuclear mass, spin and volume. For these samples the role of spin or the magnetic isotope effect is the most dominant.

Das, R.; Odom, A. L.

2007-12-01

267

Ethanol transport in Zymomonas mobilis measured by using in vivo nuclear magnetic resonance spin transfer.  

PubMed Central

For the first time, unidirectional rate constants of ethanol diffusion through the lipid membrane of a microorganism, the bacterium Zymomonas mobilis, were determined, thus replacing indirect inferences with direct kinetic data. The rate constants k1 (in to out) were 6.8 +/- 0.4s(-1) at 29 degrees C and 2.7 +/- 0.3s(-1) at 20 degrees C. They were determined by using 1H selective nuclear magnetic resonance spin magnetization transfer. The measurements were done on l-ml cell suspensions. No addition of radiotracers, withdrawing of aliquots, physical separation methods, or chemical manipulations were required. Until now, the rate constants of ethanol transport in microorganisms have been unknown because ethanol diffuses through the cytoplasmic membrane too quickly for radiolabel approaches. Net velocities of ethanol exchange were calculated from unidirectional rate constants and cytoplasmic volume, which was also determined with the same nuclear magnetic resonance experiments. The results (i) confirmed that ethanol would not be rate limiting during the conversion of glucose by Z. mobilis and (ii) indicated that ethanol can serve as an in vivo marker of cytoplasmic volume changes. This was verified by monitoring for the first time the changes of both cytoplasmic volume and extracytoplasmic and cytoplasmic concentrations of alpha and beta anomers of D-glucose in cell suspensions of a microorganism. These findings may open up new possibilities for kinetic studies of ethanol and sugar transport in Z. mobilis and other organisms.

Schoberth, S M; Chapman, B E; Kuchel, P W; Wittig, R M; Grotendorst, J; Jansen, P; DeGraff, A A

1996-01-01

268

Interaction between vine pesticides and bovine serum albumin studied by nuclear spin relaxation data.  

PubMed

Pesticides are chemicals usually used in agriculture to prevent possible diseases to crops, such as grapes, caused by parasites. Even if most of the pesticides are degraded during the wine process, residual levels remain in the final product. The most commonly used pesticides in vine belong to several classes of chemical compounds; among them, triazoles and anilinopyrimidines have been commercially used since the 1970s and 1990s, respectively. In this work, we investigated the interaction between three of the most used fungicides belonging to the chemical classes mentioned above (myclobutanil, triadimenol, and pyrimethanil) and bovine serum albumin (BSA) by nuclear spin relaxation analysis. We found that all of the pesticides were able to form a complex with BSA; nevertheless, there were strong differences in their affinity toward the plasma protein. The nuclear magnetic resonance approach used on the basis of the analysis of selective relaxation rate enhancements of pesticide protons in the presence of BSA allowed for the calculation of the affinity indexes and the equilibrium constants of the three systems. Myclobutanil showed the highest affinity toward BSA, whereas triadimenol gave the weakest interaction with the protein. The differences in the capacity of the three pesticides to bind to albumin highlighted the existence of different binding strengths on the protein. These results indicate that myclobutanil and triadimenol, despite their structure similarity, may have very different residence times in the plasma and rates of clearance. PMID:20857906

Martini, Silvia; Bonechi, Claudia; Rossi, Claudio

2010-10-13

269

Dynamic nuclear polarization of 29Si via spin S=1 centers in isotopically controlled silicon  

NASA Astrophysics Data System (ADS)

We report the results of the experiments on dynamic nuclear polarization (DNP) of 29Si nuclei under saturation the electron paramagnetic resonance (EPR) transitions of the photoexcited spin S=1 states of the oxygen+vacancy complexes in irradiated 29Si isotopically controlled silicon. The effect of isotope 29Si abundance on the line width and hyperfine structure of the Si-SL1 EPR spectra was observed. It was shown clearly that the decrease of the 29Si abundance leads to the transformation the DNP mechanism from the “differential” to “resolved” solid-effect accompanied with the increase of DNP degree. High steady-state 29Si nuclear polarization of 6% due to “resolved” solid-effect was achieved in silicon crystals with the 29Si isotope abundance below 4.7%. It was found that the DNP induced by saturation the hyperfine structure EPR lines of triplet centers does not follow the symmetric first derivative EPR line shape, showing the additional contribution to the DNP process.

Itahashi, T.; Hayashi, H.; Itoh, K. M.; Poloskin, D. S.; Vlasenko, L. S.; Vlasenko, M. P.

2009-12-01

270

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

271

Nuclear quadrupole spin dynamics: How weak RF pulses and double resonance cross-relaxation contribute to explosives detection  

NASA Astrophysics Data System (ADS)

Nuclear quadrupole resonance (NQR) is a type of radio-frequency (rf) spectroscopy which can detect quadrupolar nuclei (I > 1/2), such as nitrogen, in crystalline solids. NQR spectroscopy is useful for the detection of the many types of explosives containing 14N, however it suffers from a low signal to noise ratio (SNR) particularly in samples with long spin-lattice relaxation times. To improve the SNR the nuclear quadrupole spin dynamics are exploited in two limiting cases: systems with long spin relaxation times and systems where the excitation power is limited. The former is addressed through double resonance effects and the latter through spin echoes created by weak rf pulses. The double resonance effect occurs in samples that also contain a second faster relaxing nuclear species, such as 1H in ammonium nitrate. In this sample an 1H-14N double resonance can be created between the species that improves the SNR. While the focus is on the common case of solids containing both nitrogen and hydrogen, the theory is generally applicable to solids containing spin-1 and spin-1/2 nuclei. A model of this system is developed that treats the motionally averaged secular dipolar Hamiltonian as a perturbation of the combined quadrupole and Zeeman Hamiltonians. This model reveals three types of double resonance conditions, involving static and rf fields, and predicts expressions for the cross-relaxation rate (Wd) between the two species. Using this cross-relaxation rate, in addition to the hydrogen and nitrogen autorelaxation rates, expressions governing the relaxation back to equilibrium in a spin-1/2 and spin-1 system are determined. The three different types of double resonance conditions are created experimentally; one of them for the first time in any system and another for the first time in a solid. Under these double resonance conditions, the increase in Wd and improvements in SNR are explored both theoretically and experimentally using ammonium nitrate. The second effect investigated is the NQR spin echo that forms after excitation of a powder sample by a single weak resonant radio-frequency pulse. This single-pulse echo is identified for the first time, and when applications are limited by a weak rf field, can be used effectively to increase the SNR over conventional detection techniques.

Prescott, David

272

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

273

Dynamic-angle spinning and double rotation of quadrupolar nuclei  

SciTech Connect

Nuclear magnetic resonance (NMR) spectroscopy of quadrupolar nuclei is complicated by the coupling of the electric quadrupole moment of the nucleus to local variations in the electric field. The quadrupolar interaction is a useful source of information about local molecular structure in solids, but it tends to broaden resonance lines causing crowding and overlap in NMR spectra. Magic- angle spinning, which is routinely used to produce high resolution spectra of spin-{1/2} nuclei like carbon-13 and silicon-29, is incapable of fully narrowing resonances from quadrupolar nuclei when anisotropic second-order quadrupolar interactions are present. Two new sample-spinning techniques are introduced here that completely average the second-order quadrupolar coupling. Narrow resonance lines are obtained and individual resonances from distinct nuclear sites are identified. In dynamic-angle spinning (DAS) a rotor containing a powdered sample is reoriented between discrete angles with respect to high magnetic field. Evolution under anisotropic interactions at the different angles cancels, leaving only the isotropic evolution of the spin system. In the second technique, double rotation (DOR), a small rotor spins within a larger rotor so that the sample traces out a complicated trajectory in space. The relative orientation of the rotors and the orientation of the larger rotor within the magnetic field are selected to average both first- and second-order anisotropic broadening. The theory of quadrupolar interactions, coherent averaging theory, and motional narrowing by sample reorientation are reviewed with emphasis on the chemical shift anisotropy and second-order quadrupolar interactions experienced by half-odd integer spin quadrupolar nuclei. The DAS and DOR techniques are introduced and illustrated with application to common quadrupolar systems such as sodium-23 and oxygen-17 nuclei in solids.

Mueller, K.T. (Lawrence Berkeley Lab., CA (United States) California Univ., Berkeley, CA (United States). Dept. of Chemistry)

1991-07-01

274

Improving Estimates of Nuclear-Spin Relaxation Time (T1) in Surface-NMR Experiments  

NASA Astrophysics Data System (ADS)

Surface nuclear magnetic resonance (NMR) is a relatively novel and powerful geophysical technique for investigating hydrological characteristics of shallow aquifers from the Earth's surface in a non-invasive way. Large current loops of approximately 100 m diameter laid on the ground transmit electromagnetic pulses into the subsurface. These pulses excite spins of protons in groundwater molecules out of their equilibrium state in the Earth's magnetic field. The spin response is recorded on either coincident or offset surface receiver loops of similar dimension. The amplitudes of the response signals recorded after single-pulse excitation provide estimates of water-content in the shallow subsurface. Another important parameter is the NMR relaxation time T1, from which information on pore structure or even hydraulic conductivity can be inferred under favorable circumstances. T1 data are conventionally acquired using a scheme that involves two sequential pulses of electromagnetic energy, the second of which is phase-shifted by ? relative to the first. We show that common imperfections in the transmitted pulses and variations of the excitation field with distance from the transmitter introduce significant bias in conventional estimates of T1. Here, we propose a novel yet simple modification to the conventional scheme that is theoretically capable of resolving this problem. The proposed scheme comprises a conventional double-pulse sequence followed by an additional double-pulse sequence for which the 2nd pulse is in-phase with the 1st pulse. Subtracting the voltage signals measured during the two double-pulse sequences (i.e., phase cycle) eliminates the bias. This strategy of continuously cycling the phase of the 2nd pulse between ? and 0 in sequential double-pulse experiments and then subtracting the resulting voltages is a promising step towards recording more reliable T1 data under general field conditions.

Walbrecker, Jan O.; Hertrich, Marian; Green, Alan G.

2011-03-01

275

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

NASA Astrophysics Data System (ADS)

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 1 S) 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 4 mm diameter sapphire rotor containing the sample. The predicted average B 1 S field is 13 ?T/W 1/2, where S denotes the electron spin. For a routinely achievable input power of 5 W the corresponding value is ?SB 1 S = 0.84 MHz. 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. ?1 S/(2 ?) for a sample of 13C-urea dissolved in a 60:40 glycerol/water mixture containing the polarizing agent TOTAPOL; very good agreement was obtained between theory and experiment.

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

2011-05-01

276

Nuclear spin-lattice relaxation rate in PuMGa5 (M=Rh,Co) : A two-component spin-fermion model  

NASA Astrophysics Data System (ADS)

We examine the nuclear spin-lattice relaxation rates 1/T1 of PuRhGa5 and PuCoGa5 , both in the superconducting and normal states, as well as their Knight shifts. Results for both compounds are consistent with a superconducting gap of d -wave symmetry in the presence of strong impurity scattering, though with quite different gap-over- Tc ratios 2?0/kBTc (eight for PuCoGa5 and five for PuRhGa5 ). In the normal state, PuRhGa5 exhibits a gradual suppression of (T1T)-1 below 25K , while measurements for PuCoGa5 reveal a monotonic increase down to Tc . We propose that this behavior is consistently understood by the crossover of the two-dimensional quantum antiferromagnetic correlation of the local 5f -electron spins of Pu and the concomitant formation of the fermion pseudogap based on the two-component spin-fermion model.

Bang, Yunkyu; Graf, M. J.; Curro, N. J.; Balatsky, A. V.

2006-08-01

277

The Spin Dependence of Nuclear Muon Capture by Laser Polarized HELIUM-3.  

NASA Astrophysics Data System (ADS)

Using the muon beam at TRIUMF, we have made the first measurement of the spin dependence of the reaction: mu^- + ^3He tonu +^3H. This spin dependence is quite sensitive to the induced pseudoscalar form factor, F_{P}, a piece of the weak charged nuclear current of ^3He about which, experimentally, relatively little is known. The ratio of F_{P} to F _{A}, the axial vector form factor, is predicted by the partially conserved axial current hypothesis (PCAC) and the Goldberger-Treiman relation. Thus, a measurement of F_{P} will test our understanding of strong interactions at low energies. The rate of nuclear muon capture in ^3 He is proportional to (1+A_{v }P_{v} {rm cos} theta), where theta is the angle between the muon polarization and the direction of the triton recoil, P_{v} is the muon vector polarization and A_{v } is the vector analyzing power, a preliminary value for which is: A_{v} = .604 +/-.093(stat.)_sp{-142}{+112 }(system.). This value is in agreement with the PCAC prediction of: A_{v}=.524 +/-.006. A measure of the strength of our technique is that the raw forward/backward asymmetry in the triton recoil direction was measured to 11.5% of itself. The design, construction and operation of the device that served both as a polarized target and as a detector for the recoil tritons is the main emphasis of this thesis. The detector, a gridded ion chamber, was incorporated inside a 5 liter target that was filled with 8 atmospheres of ^3He, 100 torr of N_2, and 6 grams of Rb. Muons stopped in the target formed muonic helium atoms and were polarized by collisions with Rb atoms that were optically pumped with lasers. The ion chamber produced clean signals despite operating under the severe conditions required for optical pumping. The direction of the tritons was determined by fitting the shapes of the ionization pulses. Future improvements of our technique appear to provide the most promising avenue to improved understanding of the induced pseudoscalar coupling, F_ {P}, as well as the induced pseudoscalar coupling of the proton, g_{P}. .

Bogorad, Paul Lev

1995-01-01

278

Characterization of quantum algorithms by quantum process tomography using quadrupolar spins in solid-state nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

NMR quantum computing with qubit systems represented by nuclear spins (I=12) in small molecules in liquids has led to the most successful experimental quantum information processors so far. We use the quadrupolar spin-32 sodium nuclei of a NaNO3 single crystal as a virtual two-qubit system. The large quadrupolar coupling in comparison with the environmental interactions and the usage of strongly modulating pulses allow us to manipulate the system fast enough and at the same time keeping the decoherence reasonably slow. The experimental challenge is to characterize the ``calculation'' behavior of the quantum processor by process tomography which is here adapted to the quadrupolar spin system. The results of a selection of quantum gates and algorithms are presented as well as a detailed analysis of experimental results.

Kampermann, H.; Veeman, W. S.

2005-06-01

279

Water, hydrogen, deuterium, carbon, carbon-13, and oxygen-18 content of selected lunar material  

USGS Publications Warehouse

The water content of the breccia is 150 to 455 ppm, with a ??D from -580 to -870 per mil. Hydrogen gas content is 40 to 53 ppm with a ??D of -830 to -970 per mil. The CO2 is 290 to 418 ppm with S 13C = + 2.3 to + 5.1 per mil and ??18O = 14.2 to 19.1 per mil. Non-CO2 carbon is 22 to 100 ppm, ??18C = -6.4 to -23.2 per mil. Lunar dust is 810 ppm H2O (D = 80 ppm) and 188 ppm total carbon (??13C = -17.6 per mil). The 18O analyses of whole rocks range from 5.8 to 6.2 per mil. The temperature of crystallization of type B rocks is 1100?? to 1300??C, based on the oxygen isotope fractionation between coexisting plagioclase and ilmenite.

Friedman, I.; O'Neil, J. R.; Adami, L. H.; Gleason, J. D.; Hardcastle, K.

1970-01-01

280

Population and decay of high-spin states in /sup 157-161/Yb: evolution of nuclear shapes as a function spin and neutron number  

SciTech Connect

The population and decay of the entry states in /sup 157-161/Yb and /sup 155-158/Er from the reactions of 136- and 149-MeV /sup 20/Ne with /sup 144/Nd and /sup 146/Nd have been investigated with the Spin Spectrometer gated with a Ge detector. Statistical-model calculations reproduce the main features of the entry state populations. The entry lines, as a function of multiplicity, M/sub ..gamma../ show changes in slope at high M/sub ..gamma../ which are due to changes in the decay mode as a result of changes in nuclear structure. Energy spectra of the continuum ..gamma..-rays and angular distributions as a function of M/sub ..gamma../ show the onset of a dipole component localized at 650 +- 100 keV accompanied by an equally intense quadrupole component at twice the energy that continues to evolve to higher energies with increasing multiplicity. For /sup 157/ /sup 158/ /sup 159/ /sup 160/ /sup 161/Yb the dipole component appears at M/sub ..gamma../ = 21,22,23,25, and 27 (at spin I approx. = 38,40,42,45, and 50), respectively. At precisely these multiplicities the entry lines show a decrease in slope. In /sup 158/Yb the dipole component disappears at M/sub ..gamma../ = 28 and the entry line resumes its original slope. The results are consistent with the following picture. At low spins for /sup 157/ /sup 158/Yb the nuclear shapes evolve from prolate to slightly oblate particle-aligned structures. At I approx. = 38,40,42,45, and 50 the /sup 157/ /sup 158/ /sup 159/ /sup 160/ /sup 161/Yb nuclei, respectively, develop high-K rotational bands which may be built on oblate structures with large deformation (epsilon approx. = 0.3). At I = 49 a transition to triaxial shape appears to occur in /sup 158/Yb.

Jaeaeskelaeinen, M.; Sarantites, D.G.; Dilmanian, F.A.; Woodward, R.; Puchta, H.; Beene, J.R.; Halbert, M.L.; Hattula, J.; Hensley, D.C.; Barker, J.H.

1982-01-01

281

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

282

Breit interaction effects in relativistic theory of the nuclear spin-rotation tensor  

NASA Astrophysics Data System (ADS)

In this work, relativistic effects on the nuclear spin-rotation (SR) tensor originated in the electron-nucleus and electron-electron Breit interactions are analysed. To this end, four-component numerical calculations were carried out in model systems HX (X=H,F,Cl,Br,I). The electron-nucleus Breit interaction couples the electrons and nuclei dynamics giving rise to a purely relativistic contribution to the SR tensor. Its leading order in 1/c is of the same value as that of relativistic corrections on the usual second order expression of the SR tensor considered in previous work [I. A. Aucar, S. S. Gómez, J. I. Melo, C. G. Giribet, and M. C. Ruiz de Azúa, J. Chem. Phys. 138, 134107 (2013)], and therefore it is absolutely necessary to establish its relative importance. For the sake of completeness, the corresponding effect originating in the electron-electron Breit interaction is also considered. It is verified that in all cases these Breit interactions yield only very small corrections to the SR tensors of both the X and H nuclei in the present series of compounds. Results of the present work strongly suggest that in order to achieve experimental accuracy in the theoretical study of the SR tensor both electron-nucleus and electron-electron Breit effects can be safely neglected.

Aucar, I. Agustín; Gómez, Sergio S.; Giribet, Claudia G.; Ruiz de Azúa, Martín C.

2013-09-01

283

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

PubMed

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 improving long-term instrument stability. Changing samples in conventional cryogenic MAS DNP/NMR experiments involves warming the probe to room temperature, detaching all cryogenic, RF, and microwave connections, removing the probe from the magnet, replacing the sample, and reversing all the previous steps, with the entire cycle requiring a few hours. The sample exchange system described here-which relies on an eject pipe attached to the front of the MAS stator and a vacuum jacketed dewar with a bellowed hole-circumvents these procedures. To demonstrate the excellent sensitivity, resolution, and stability achieved with this quadruple resonance sample exchange probe, we have performed high precision distance measurements on the active site of the membrane protein bacteriorhodopsin. We also include a spectrum of the tripeptide N-f-MLF-OH at 100K which shows 30 Hz linewidths. PMID:19356957

Barnes, Alexander B; Mak-Jurkauskas, Melody L; Matsuki, Yoh; Bajaj, Vikram S; van der Wel, Patrick C A; Derocher, Ronald; Bryant, Jeffrey; Sirigiri, Jagadishwar R; Temkin, Richard J; Lugtenburg, Johan; Herzfeld, Judith; Griffin, Robert G

2009-06-01

284

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

PubMed Central

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 improving long-term instrument stability. Changing samples in conventional cryogenic MAS DNP/NMR experiments involves warming the probe to room temperature, detaching all cryogenic, RF, and microwave connections, removing the probe from the magnet, replacing the sample, and reversing all the previous steps, with the entire cycle requiring a few hours. The sample exchange system described here — which relies on an eject pipe attached to the front of the MAS stator and a vacuum jacketed dewar with a bellowed hole — circumvents these procedures. To demonstrate the excellent sensitivity, resolution, and stability achieved with this quadruple resonance sample exchange probe, we have performed high precision distance measurements on the active site of the membrane protein bacteriorhodopsin. We also include a spectrum of the tripeptide N-f-MLF-OH at 100 K which shows 30 Hz linewidths.

Barnes, Alexander B.; Mak-Jurkauskas, Melody L.; Matsuki, Yoh; Bajaj, Vikram S.; van der Wel, Patrick C. A.; DeRocher, Ronald; Bryant, Jeffrey; Sirigiri, Jagadishwar R.; Temkin, Richard J.; Lugtenburg, Johan; Herzfeld, Judith; Griffin, Robert G.

2009-01-01

285

Spin-mapping of coal structures with ESE and ENDOR (Electron-Nuclear Double Resonance)  

SciTech Connect

Our Laboratory is presently engaged in developing a method to model sulfur-containing compounds in whole coal. It has been established that most of the organic sulfur in coal exists in the form of aromatic groups known as thiophenes. Sulfur-containing aromatic compounds such as thiophene, tetraphenylthiophene and thianthrene were adsorbed onto silica-alumina catalyst surfaces were used as models to emulate coal's anisotropic nature and abundance of unpaired electron spin density. The spectroscopic techniques used were Electron Paramagnetic Resonance (EPR), Electron-Nuclear Double Resonance (ENDOR). EPR spectroscopy is a well established method to characterize g-matrix anisotropy in transition metal compounds. With increased resolution, EPR has become very useful for characterizing the small but still detectable g-matrix anisotropy in organic systems such as coal and the model systems for coal. ENDOR spectroscopy involves the inducement of NMR transitions of the nearby protons while detecting them with an EPR detection scheme which is several orders of magnitude more sensitive than using a NMR detection scheme. Analysis of the ENDOR spectra produced hyperfine information which is characteristic of these sulfur-containing systems. This information will be needed to resolve anisotropic hyperfine spectral features attributable to sulfur content in the analysis of coal macerals. 2 refs., 3 figs.

Belford, R.L.; Clarkson, R.B.

1989-03-01

286

Microcoil high-resolution magic angle spinning NMR spectroscopy.  

PubMed

We report the construction of a dual-channel microcoil nuclear magnetic resonance probehead allowing magic-angle spinning for mass-limited samples. With coils down to 235 mum inner diameter, this allows high-resolution solid-state NMR spectra to be obtained for amounts of materials of a few nanoliters. This is demonstrated by the carbon-13 spectrum of a tripeptide and a single silk rod, prepared from the silk gland of the Bombyx mori silkworm. Furthermore, the microcoil allows for radio frequency field strengths well beyond current probe technology, aiding in getting the highest possible resolution by efficiently decoupling the observed nuclei from the abundantly present proton nuclei. PMID:16819853

Janssen, Hans; Brinkmann, Andreas; van Eck, Ernst R H; van Bentum, P Jan M; Kentgens, Arno P M

2006-07-12

287

High-temperature nuclear spin relaxation in 51V metal: self-diffusion and interstitial-impurity diffusion effects  

Microsoft Academic Search

Zeeman and dipolar reservoir nuclear spin relaxation times T1Z, T1D and T2 in 51V metal have been measured in samples with different purities, over temperatures within the 300-1700K range. T1Z and T1D have been analysed into electronic, quadrupolar and diffusion contributions, whose temperature dependences have been determined. For the electronic contributions it has been shown that T1eZ=(2+ epsilon )T1eD with

J. F. Tiers; Y. Chabre

1981-01-01

288

Lyso platelet activating factor (LysoPAF) and its enantiomer. Total synthesis and carbon-13 NMR spectroscopy.  

PubMed

Described is a reaction sequence for the total synthesis of lyso platelet activating factor (lysoPAF; 1-O-alkyl-sn-glycero-3-phosphocholine) and its enantiomer. The procedure is versatile and yields optically pure isomers of defined chain length. The synthesis is equally suited for the preparation of lysoPAF analogues and its enantiomers with unsaturation in the long aliphatic chain. First, rac-1(3)-O-alkylglycerol is prepared by alkylation of rac-isopropylideneglycerol with alkyl methanesulfonate followed by acid-catalyzed removal of the ketal group. The primary hydroxy group of alkylglycerol is then protected by tritylation, the secondary hydroxy group is acylated, and the protective trityl group is removed under mild acidic conditions with boric acid on silicic acid, essentially without acyl migration. Condensation of the diradylglycerol with bromoethyl dichlorophosphate in diethyl ether, hydrolysis of the resulting chloride, and nucleophilic displacement of the bromine with trimethylamine gives rac-1-O-alkyl-2-acylglycero-3-phosphocholine in good overall yield. The racemic alkylacylglycerophosphocholine is finally treated with snake venom phospholipase A2 (Ophiophagus hannah) which affords 1-O-alkyl-sn-glycero-3-phosphocholine (lysoPAF) of natural configuration in optically pure form. The "unnatural" 3-O-alkyl-2-O-acyl-sn-glycero-1-phosphocholine enantiomer, which is not susceptible to phospholipase A2 cleavage, gives 3-O-alkyl-sn-glycero-1-phosphocholine upon deacylation with methanolic sodium hydroxide. Homogeneity and structure of the intermediates and final products were ascertained by carbon-13 nuclear magnetic resonance spectroscopy on monomeric solutions. PMID:2079867

Murari, M P; Murari, R; Parthasarathy, S; Guy, C A; Kumar, V V; Malewicz, B; Baumann, W J

1990-10-01

289

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

NASA Astrophysics Data System (ADS)

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 19F 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 2J(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; Kupka, Teobald; Stachów, Micha?

2014-04-01

290

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

PubMed

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 (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 (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). PMID:24735295

Nozirov, Farhod; Kupka, Teobald; Stachów, Micha?

2014-04-14

291

A solid-state and suspended-state magic angle spinning nuclear magnetic resonance spectroscopic investigation of a 9-ethyladenine molecularly imprinted polymer  

Microsoft Academic Search

Suspended-state high resolution\\/magic angle spinning nuclear magnetic resonance spectroscopy and solid-state cross-polarization\\/magic angle spinning nuclear magnetic resonance spectroscopy were employed to study the interactions between 9-ethyladenine and a 9-ethyladenine molecularly imprinted polymer, and a non-imprinted polymer, respectively, both are copolymers of methacrylic acid and ethyleneglycol dimethacrylate. Template-related structural differences between the materials were revealed by contact time measurements and solid-state

Urban Skogsberg; Christoph Meyer; Jens Rehbein; Gerd Fischer; Siri Schauff; Norbert Welsch; Klaus Albert; Andrew J. Hall; Börje Sellergren

2007-01-01

292

Chemical characterization of pigment gallstones using /sup 13/C nuclear magnetic resonance analysis  

SciTech Connect

The unique ability of Carbon-13 nuclear magnetic resonance analysis with cross polarization/magic angle spinning techniques to investigate chemical structures of solids is used to probe the chemical characteristics of several gallstone types. New pulse program techniques are used to distinguish various carbon atoms in studying the polymeric nature of the black bilirubinoid pigment of pigment gallstones. Evidence for the involvement of the carboxyl group and noninvolvement of vinyl groups of bilirubinoids in the polymeric bond formation is presented. Conjugated bilirubin structures are found to be present in some solid residues from pigment stones extracted with acidic methanol/chloroform.

Woolfenden, W.R. (Univ. of Utah, Salt Lake City); Grant, D.M.; Straight, R.C.; Englert, E. Jr.

1982-07-30

293

Experimental evidence for ferromagnetic spin-pairing superconductivity emerging in UGe2 : A Ge73 -nuclear-quadrupole-resonance study under pressure  

NASA Astrophysics Data System (ADS)

We report that a different type of superconducting order parameter has been realized in the ferromagnetic states in UGe2 via Ge73 -nuclear-quadrupole-resonance experiments performed under pressure (P) . Measurements of the nuclear spin-lattice relaxation rate (1/T1) have revealed an unconventional nature of superconductivity such that the up-spin band is gapped with line nodes, but the down-spin band remains gapless at the Fermi level. This result is consistent with that of a ferromagnetic spin-pairing model in which Cooper pairs are formed among ferromagnetically polarized electrons. The present experiment has shed light on the possible origin of ferromagnetic superconductivity, which is mediated by ferromagnetic spin-density fluctuations relevant to the first-order transition inside the ferromagnetic states.

Harada, A.; Kawasaki, S.; Mukuda, H.; Kitaoka, Y.; Haga, Y.; Yamamoto, E.; ?nuki, Y.; Itoh, K. M.; Haller, E. E.; Harima, H.

2007-04-01

294

Observation of zero-point quantum fluctuations of a single-molecule magnet through the relaxation of its nuclear spin bath.  

PubMed

A single-molecule magnet placed in a magnetic field perpendicular to its anisotropy axis can be truncated to an effective two-level system, with easily tunable energy splitting. The quantum coherence of the molecular spin is largely determined by the dynamics of the surrounding nuclear spin bath. Here we report the measurement of the nuclear spin-lattice relaxation rate 1/T1n in a single crystal of the single-molecule magnet Mn12-ac, at T ? 30 mK in perpendicular fields B? up to 9 T. The relaxation channel at B ? 0 is dominated by incoherent quantum tunneling of the Mn12-ac spin S, aided by the nuclear bath itself. However for B?>5 T we observe an increase of 1/T1n by several orders of magnitude up to the highest field, despite the fact that the molecular spin is in its quantum mechanical ground state. This striking observation is a consequence of the zero-point quantum fluctuations of S, which allow it to mediate the transfer of energy from the excited nuclear spin bath to the crystal lattice at much higher rates. Our experiment highlights the importance of quantum fluctuations in the interaction between an "effective two-level system" and its surrounding spin bath. PMID:24702408

Morello, A; Millán, A; de Jongh, L J

2014-03-21

295

Matrix Isolation Spectroscopy and Nuclear Spin Conversion of NH3 and ND3 in Solid Parahydrogen  

NASA Astrophysics Data System (ADS)

We present matrix isolation infrared absorption spectra of NH3 and ND3 trapped in solid parahydrogen (pH2) at temperatures around 1.8 K. We used the relatively slow nuclear spin conversion (NSC) of NH3 and ND3 in freshly deposited pH2 samples as a tool to assign the sparse vibration-inversion-rotation (VIR) spectra of NH3 in the regions of the -2, -4, 2-4, -1, and -3 bands and ND3 in the regions of the -2, -4, -1, and -3 fundamentals. Partial assignments are also presented for various combination bands of NH3. Detailed analysis of the -2 bands of NH3 and ND3 indicates that both isotopomers are nearly free rotors; that the vibrational energy is blue-shifted by 1-2%; and that the rotational constants and inversion tunneling splitting are 91-94% and 67-75%, respectively, of the gas-phase values. The line shapes of the VIR absorptions are narrow (0.2-0.4 cm-1) for upper states that cannot rotationally relax and broad (>1 cm-1) for upper states that can rotationally relax. We report and assign a number of NH3-induced infrared absorption features of the pH2 host near 4150 cm-1, along with a cooperative transition that involves simultaneous vibrational excitation of a pH2 molecule and rotation-inversion excitation of NH3. The NSCs of NH3 and ND3 were found to follow first-order kinetics with rate constants at 1.8 K of k = 1.88(16) - 10-3 s-1 and k = 1.08(8) - 10-3 s-1, respectively. These measured rate constants are compared to previous measurements for NH3 in an Ar matrix and with the rate constants measured for other dopant molecules isolated in solid pH2.

Ruzi, Mahmut; Anderson, David T.

2013-10-01

296

Intermolecular structure determination of amyloid fibrils with magic-angle spinning and dynamic nuclear polarization NMR  

PubMed Central

We describe magic-angle spinning NMR experiments designed to elucidate the interstrand architecture of amyloid fibrils. Three methods are introduced for this purpose, two being based on the analysis of long-range 13C-13C correlation spectra and a third based on the identification of intermolecular interactions in 13C-15N spectra. We show, in studies of fibrils formed by the 86-residue SH3 domain of PI3 kinase (PI3-SH3), that efficient 13C-13C correlation spectra display a resonance degeneracy that establishes a parallel, in-register alignment of the proteins in the amyloid fibrils. In addition, this degeneracy can be circumvented to yield direct intermolecular constraints. The 13C-13C experiments are corroborated by 15N-13C correlation spectrum obtained from a mixed [15N,12C]/[14N,13C] sample which directly quantifies interstrand distances. Furthermore, when the spectra are recorded with signal enhancement provided by dynamic nuclear polarization (DNP) at 100 K, we demonstrate a dramatic increase (from 23 to 52) in the number of intermolecular 15N-13C constraints present in the spectra. The increase in the information content is due to the enhanced signal intensities and to the fact that dynamic processes, leading to spectral intensity losses, are quenched at low temperatures. Thus, acquisition of low temperature spectra addresses a problem that is frequently encountered in MAS spectra of proteins. In total the experiments provide 111 intermolecular 13C-13C and 15N-13C constraints that establish that the PI3-SH3 protein strands are aligned in a parallel, in-register arrangement within the amyloid fibril.

Bayro, Marvin J.; Debelouchina, Galia T.; Eddy, Matthew T.; Birkett, Neil R.; MacPhee, Catherine E.; Rosay, Melanie; Maas, Werner E.; Dobson, Christopher M.

2011-01-01

297

Intermolecular structure determination of amyloid fibrils with magic-angle spinning and dynamic nuclear polarization NMR.  

PubMed

We describe magic-angle spinning NMR experiments designed to elucidate the interstrand architecture of amyloid fibrils. Three methods are introduced for this purpose, two being based on the analysis of long-range (13)C-(13)C correlation spectra and the third based on the identification of intermolecular interactions in (13)C-(15)N spectra. We show, in studies of fibrils formed by the 86-residue SH3 domain of PI3 kinase (PI3-SH3 or PI3K-SH3), that efficient (13)C-(13)C correlation spectra display a resonance degeneracy that establishes a parallel, in-register alignment of the proteins in the amyloid fibrils. In addition, this degeneracy can be circumvented to yield direct intermolecular constraints. The (13)C-(13)C experiments are corroborated by (15)N-(13)C correlation spectra obtained from a mixed [(15)N,(12)C]/[(14)N,(13)C] sample which directly quantify interstrand distances. Furthermore, when the spectra are recorded with signal enhancement provided by dynamic nuclear polarization (DNP) at 100 K, we demonstrate a dramatic increase (from 23 to 52) in the number of intermolecular (15)N-(13)C constraints detectable in the spectra. The increase in the information content is due to the enhanced signal intensities and to the fact that dynamic processes, leading to spectral intensity losses, are quenched at low temperatures. Thus, acquisition of low temperature spectra addresses a problem that is frequently encountered in MAS spectra of proteins. In total, the experiments provide 111 intermolecular (13)C-(13)C and (15)N-(13)C constraints that establish that the PI3-SH3 protein strands are aligned in a parallel, in-register arrangement within the amyloid fibril. PMID:21774549

Bayro, Marvin J; Debelouchina, Galia T; Eddy, Matthew T; Birkett, Neil R; MacPhee, Catherine E; Rosay, Melanie; Maas, Werner E; Dobson, Christopher M; Griffin, Robert G

2011-09-01

298

Molecular orbital calculations of /sup 13/C-/sup 13/C and /sup 1/H-/sup 1/H nuclear spin-spin coupling constants  

SciTech Connect

Theoretical studies are presented for the conformational dependencies of vicinal /sup 13/C-/sup 13/C coupling constants within a variety of saturated and unsaturated molecular frameworks. Using the molecular orbital approach of Blizzard and Santry, it is shown that three distinct patterns of dihedral angle versus /sup 3/H/sub CC/sup contract/ coupling are produced, depending upon the degree of double bonding present within the direct coupling path. By means of calculations that involve modifying the various exchange integrals, two of these coupling patterns are found to depend on sigma-..pi.. exchange. A rationalization of the origin of these coupling patterns is presented. In all systems studied, the orbital and dipolar contributions to the vicinal coupling constant are calculated to be negligible compared to the Fermi contact mechanism except in conjugated systems. The FP/INDO molecular orbital method is employed in the investigation of substitutent effects on /sup 1/H-/sup 1/H coupling constants in substituted ethanes, ethylenes, and benzenes. Substituent effects are simulated by varying the (1/2)(I + A) INDO parameters on two different types of pseudoatoms, one essentially a pseudo-hydrogen and the other involving 2s and 2p orbitals on two centers. A review of the theory of nuclear spin-spin coupling is presented.

Severson, M.L.

1984-01-01

299

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

300

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

301

Two-dimensional (13)C-(13)C correlation spectroscopy with magic angle spinning and dynamic nuclear polarization.  

PubMed

The sensitivity of solid-state NMR experiments can be enhanced with dynamic nuclear polarization (DNP), a technique that transfers the high Boltzmann polarization of unpaired electrons to nuclei. Signal enhancements of up to 23 have been obtained for magic angle spinning (MAS) experiments at 5 T and 85-90 K using a custom-designed high-power gyrotron. The extended stability of MAS/DNP experiments at low temperature is demonstrated with (1)H-driven (13)C spin-diffusion experiments on the amino acid proline. These (13)C-(13)C chemical shift correlation spectra are the first two-dimensional MAS/DNP experiments performed at high field (>1.4 T). PMID:11916398

Rosay, Melanie; Weis, Volker; Kreischer, Kenneth E; Temkin, Richard J; Griffin, Robert G

2002-04-01

302

Through-space hydrogen-fluorine and carbon-fluorine nuclear spin-spin coupling: An experimental study  

SciTech Connect

The synthesis of 1-fluoro-8-methylbiphenylene (16) was repeated and both H-F and C-F coupling between the fluorine and the methyl group was found to be either nonexistent or beyond the resolution of the spectrometer. Several unsuccessful attempts were made to repeat the synthesis of 4-fluoro-5-methylfluorene (17). 4-Fluoro-5-methylphenanthrene (65) was generated via eliminative photocyclization of stilbene 102 and was found to have [sup 6]J[sub H-F] = 12.4 H and [sup 5]J[sub C-F] = 24.1 Hz between fluorine and the methyl group. These values are among the largest ever reported for through-space H-F and C-F coupling. In an attempt to produce examples of frozen methyl compounds akin to the 5-fluoro-1,2,3,4-tetrahydrophenanthrenes 25 and 26, efforts were made toward synthesizing the dihydrobenzindane 104 and the aceanthrene 105. Intermediate products were realized in each pathway. 4-Fluoro-5-methylacridine (160) was synthesized to test whether the lone pairs on nitrogen transmit spin information between fluorine and the methyl group. No H-F or C-F splitting was observed, however. The synthesis of 1,4-dimethyl-5,6,7,8-tetrafluronaphthalene (170) was repeated and the compound showed deshielding of the peri fluorines by the methyl groups compared to the desmethyl analog 172. The synthesis of 1-t-butyl-8-fluoronaphthalene (173) was repeated and the material was studied by Dynamic NMR spectroscopy. At low temperatures, the t-butyl group was found to undergo slow rotation on the NMR timescale, as was the individual methyl group antiperiplanar to the fluorine. In order to continue study of the regioselectivity of Diels-Alder reactions of 3-fluorobenzyne with 2-alkylfurans, 2-neopentyfuran (181) was generated and allowed to react with 3-fluorobenzyne. The ratio of the 1,8-adduct 196 to the 1,5-adduct 197 was 1,7L1-the same ratio as the previously observed for 2-methylfuran. This proportion was much less than the 9:1 isomer ratio obtained when 2-t-butylfuran was utilized.

Olson, E.R.

1993-01-01

303

Evolution of Nuclear Shapes at High Spins as Determined by Lifetime Measurements.  

National Technical Information Service (NTIS)

Lifetime measurements of high spin states are obtained by the Doppler-shift recoil-distance method. Transition quadrupole moments are extracted from these data. Expanding on earlier experimental work, lifetime and moment of inertia measurements were made ...

N. Johnson

1986-01-01

304

Nuclear Magnetic Resonance Spectroscopy Applications: Proton NMR In Biological Objects Subjected To Magic Angle Spinning  

SciTech Connect

Proton NMR in Biological Objects Submitted to Magic Angle Spinning, In Encyclopedia of Analytical Science, Second Edition (Paul J. Worsfold, Alan Townshend and Colin F. Poole, eds.), Elsevier, Oxford 6:333-342. Published January 1, 2005. Proposal Number 10896.

Wind, Robert A.; Hu, Jian Zhi

2005-01-01

305

High-spin states in the neutron-rich N = 50 region: nuclear structure close to 78Ni  

NASA Astrophysics Data System (ADS)

The spectroscopy of fission fragments, obtained by the 18O+208Pb fusion-fission reaction at 85 MeV bombarding energy, has been performed with the Euroball IV ?-array. High-spin states in many neutron-rich Se, Br, Kr and Rb of the 78Ni region nuclei have been identified for the first time. Several physical aspects which govern the nuclear structure in this mass region are underlined thanks to the new results. Among those, empirical values of the residual proton-neutron interactions have been extracted for the ?f5/2?vd5/2 and ?p3/2?vd5/2 configurations.

Astier, A.; Porquet, M.-G.; Venkova, Ts.; Prévost, A.; Deloncle, I.; Azaiez, F.; Buta, A.; Curien, D.; Dorvaux, O.; Duchêne, G.; Gall, B. J. P.; Khalfallah, F.; Piqueras, I.; Rousseau, M.; Meyer, M.; Redon, N.; Stézowski, O.; Lucas, R.; Bogachev, A.

2009-10-01

306

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

307

Robust control of entanglement in a nitrogen-vacancy center coupled to a C13 nuclear spin in diamond  

NASA Astrophysics Data System (ADS)

We address the problem of generating a robust entangling gate between electronic and nuclear spins in a system of a single nitrogen-vacancy center coupled to a nearest C13 atom in diamond against certain types of systematic errors such as pulse-length and off-resonance errors. We analyze the robustness of various control schemes: sequential pulses, composite pulses and numerically optimized pulses. We find that numerically optimized pulses, produced by the modified gradient ascent pulse engineering (GRAPE) algorithm, are more robust than the composite pulses and the sequential pulses. The optimized pulses can also be implemented in a faster time than the composite pulses.

Said, R. S.; Twamley, J.

2009-09-01

308

Heteronuclear dipolar decoupling in solid-state nuclear magnetic resonance under ultra-high magic-angle spinning.  

PubMed

We compare in this communication several heteronuclear dipolar decoupling sequences in solid-state nuclear magnetic resonance experiments under a magic-angle spinning frequency of 60 kHz. The decoupling radiofrequency field amplitudes considered are 190 and 10 kHz. No substantial difference was found among the sequences considered here in performance barring the difference in the optimisation protocol of the various schemes, an aspect that favours the use of swept-frequency two pulse phase modulation (SW(f)-TPPM). PMID:21354839

Mithu, Venus Singh; Paul, Subhradip; Kurur, Narayanan D; Madhu, P K

2011-04-01

309

Carbon-13 NMR relaxation studies demonstrate an inverse temperature transition in the elastin polypentapeptide.  

PubMed

Carbon-13 NMR longitudinal relaxation time and line-width studies are reported on the coacervate concentration (about 60% water by weight) of singly carbonyl carbon enriched polypentapeptides of elastin: specifically, (L-Val1-L-[1-13C]Pro2-Gly3-L-Val4-Gly5)n and (L-Val1-L-Pro2-Gly3-L-Val4-[1-13C]Gly5)n. On raising the temperature from 10 to 25 degrees C and from 40 to 70 degrees C, carbonyl mobility increases, but over the temperature interval from 25 to 40 degrees C, the mobility decreases. The results characterize an inverse temperature transition in the most fundamental sense of temperature being a measure of molecular motion. This transition in the state of the polypentapeptide indicates an increase in order of polypeptide on raising the temperature from 25 degrees C to physiological temperature. This fundamental NMR characterization corresponds with the results of numerous other physical methods, e.g., circular dichroism, dielectric relaxation, and electron microscopy, that correspondingly indicate an increase in order of the polypentapeptide both intramolecularly and intermolecularly for the same temperature increase from 25 to 40 degrees C. Significantly with respect to elastomeric function, thermoelasticity studies on gamma-irradiation cross-linked polypentapeptide coacervate show a dramatic increase in elastomeric force over the same interval that is here characterized by NMR as an inverse temperature transition. The temperature dependence of mobility above 40 degrees C indicates an activation energy of the order of 1.2 kcal/mol, which is the magnitude of barrier expected for elasticity. PMID:4074687

Urry, D W; Trapane, T L; Iqbal, M; Venkatachalam, C M; Prasad, K U

1985-09-10

310

Carbon-13 NMR relaxation studies of pre-melt structural dynamics in [4-13C-uracil] labeled E. coli transfer RNAIVal.  

PubMed Central

We report 67.8 MHz carbon-13 spin-lattice relaxation studies on [4-13C-uracil] labeled tRNAIVal purified from E. coli SO-187. Following 13C-enriched C4 carbonyl resonances from modified and unsubstituted uridines scattered throughout the polymer backbone enables us to determine dynamical features in both loop and helical stem regions. The experimental results have been analyzed in terms of a model of isotropic overall molecular reorientation. "Anomalous" residues for which the experimental data cannot be accounted for in terms of the model provide an assessment of local and regional properties. Thus, "native" tRNAIVal under physiological conditions of magnesium (10 mM) and temperature (20 degrees - 40 degrees C), exhibits the following characteristics: 1) uridines held rigidly in helical stems and tertiary interactions display correlation times for rotational reorientation of 15-20 nsecs, typical for overall tRNA motion; 2) uridines in loops such as the wobble residue uridine-5-oxyacetic acid (V34) are quite accessible to solvent; moreover V34 and another loop residue, D17, exhibit local mobility; 3) the tertiary interactions involving 4-thio uridine (s4U8) and A14 and ribothymidine (rT54) and A58 are weakened as temperature increases.

Olsen, J I; Schweizer, M P; Walkiw, I J; Hamill, W D; Horton, W J; Grant, D M

1982-01-01

311

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

312

What Do Nuclear Spin Temperatures Tell Us About The Origin Of Comets? A Multi-molecule Study  

NASA Astrophysics Data System (ADS)

Comets are true remnants of our primordial Solar System, and provide unique clues to its formation and evolution, including the delivery of organics and water to our planet. A key indicator stored in the molecular structure of the nuclear ices is the spin temperature (Tspin), derived from spin-isomeric ratios (Rspin, e.g. ortho/para). At the time when cometary ices formed, the prevailing temperature defined the relative abundance of the different spin-isomeric species, and herewith Rspin and Tspin are normally treated as “remnant thermometers” probing the formation environments. Most of our knowledge of this indicator comes from measurements of ortho-para ratios in water and NH2, suggesting a common Tspin near 30K. This information is based on a restricted sample of comets, and the measurements are particularly sensitive to the molecular modeling technique and adopted spectral database. Here, we present new methodologies for extracting spin temperatures from ethane (C2H6), methane (CH4), and methanol (CH3OH), and describe advanced new models for ortho/para water (H2O) and ammonia (NH3). Our H2O analysis is based on the most complete fluorescence radiative transfer model to date, which incorporates 1,200 million transitions including those originating from high-energy levels that are activated in comets via non-resonance cascade. In a similar fashion, we developed non-resonance fluorescence models for NH3 and HCN, and quantum band models for the ?7 band of C2H6 and ?3 band of CH3OH. All models respect spin symmetry non-conversion radiative rules, and make use of a realistic Solar spectrum for the computation of fluorescence pumps. We applied these new methods to derive spin-isomeric ratios for H2O, CH4, C2H6, CH3OH and NH3 from three high-quality cometary datasets: 1) C/2007 W1 (Boattini), 2) C/2001 A2 (LINEAR), and 3) 8P/Tuttle. We compare our results with the measured organic compositions for these comets, and present possible formation and evolution scenarios.

Villanueva, Geronimo; Mumma, M. J.; Bonev, B. P.; DiSanti, M. A.; Magee-Sauer, K.; Gibb, E. L.; Paganini, L.; Radeva, Y. L.

2012-10-01

313

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

314

Methods for the Synthesis of L-Leucine Selectively Labelled with Carbon13 or Deuterium in either Diastereotopic Methyl Group  

Microsoft Academic Search

A versatile approach is described for the enantioselective synthesis of isotopically labelled L-leucine involving the preparation of 2-oxo-4-methylpentanoic acid labelled selectively with carbon-13 or deuterium in either the pro-R or pro-S methyl group followed by a reductive amination of the ketone catalysed by leucine dehydrogenase. This strategy is applied to the total synthesis of (2S.4R)-[5.5.5-D3]-leucine using CD3I as the source

Nicholas M. Kelly; R. Gordon Reid; Christine L. Willis; Peter L. Winton

1995-01-01

315

Evaluation of acidity of strong acid catalysts. 1. Derivation of an acidity function from carbon-13 NMR measurements  

Microsoft Academic Search

The limitations of the Hammett indicator method for acidity measurements of liquid acid catalysts of practical importance and the inapplicability in principle of the Hammett acidity concept to solid acid catalysts are discussed. Evaluation of acidities from the hydronation equilibrium of two simple alcohols, methanol and ethanol, and an α,β-unsaturated detone, 4-methyl-3-penten-2-one (mesityl oxide, I), by carbon-13 NMR is demonstrated

D. Farcasiu; A. Ghenciu; G. Miller

1992-01-01

316

Study of order and dynamics in liquid crystalline materials by carbon-13 and deuterium NMR spectroscopy  

NASA Astrophysics Data System (ADS)

This dissertation investigates the phase structures, molecular structures and diffusion motions in some recently discovered liquid crystals using 1D and 2D carbon-13 and deuterium NMR spectroscopy. Two classes of liquid crystals are involved: chiral rod-like liquid crystals and banana mesogens. Our investigations of these new materials were divided into five main sections. The ordering and structures of banana liquid crystals and chiral rod-like mesogens were extracted from solid-state 13C NMR experiments including Separated-Local-Field study based on Lee-Goldberg Cross-Polarization (LGCP-SLF) and temperature dependent chemical shifts. The principal values of CSA tensor were measured using Separation of Undistorted CSA Powder patterns by Effortless Recoupling (SUPER) experiment. Some ID and 2D pulse experiments were performed for the assignment of carbon peaks, such as Cross-Polarization Polarization-Inversion (CPPI), HECTOR and so on. The soliton-like distortion of the helicoidal structure in the chiral smectic C phase (SmC*) of 8BEF5 liquid crystal was observed by the angular dependent DNMR patterns, and quantitatively interpreted based on Landau theory. The distortion was induced by the NMR magnetic field. The phase structure and interlayer diffusion in anticlinic Sm C* phases (Sm C*A , Sm C*Fi1 and Sm C*Fi2 ) of 10B1M7 liquid crystal were measured using angular dependent DNMR lineshapes and echo intensities. This work represents the first study of ferrielectric smectic phases by means of NMR. Measurements of the interlayer diffusion in synclinic and anticlinic SmC* phases (SmC*, Sm C*Fi1 and Sm C*Fi2 ) of 10B1M7 were carried out using 2H NMR exchange experiments. The phase structures of anticlinic SmC* phases were also determined using the same technique. A 'deformed clock model' was found to be appropriate for these phases. Molecular structures and dynamics were investigated in an exotic B 2 phase of a banana liquid crystal Pbis11BB by means of CP-MAS 13C NMR, MAS 2D 13C NMR exchange and LGCP-SLF (with MAS) experiments. These experiments showed that the molecules have asymmetric conformation in the solid state and carry on much slower motions in solid and liquid states compared to banana molecules in the same homologous series.

Xu, Jiadi

317

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

NASA Astrophysics Data System (ADS)

T-odd angular correlations in ternary fission of 233U and 235U 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.

Barabanov, A. L.

2013-07-01

318

The Nuclear Responses for Double Beta Neutrinos and Double Spin Isospin Resonances by Using of Double Charge Exchange Heavey Ion Reaction  

NASA Astrophysics Data System (ADS)

To study double spin-isospin responses in view of the ??? decays, double charge-exchange nuclear reactions have measured at RCNP. We have succeeded to measure the double charge exchange reaction by means of heavy ion reaction. From these experiments, we conclude that the (11B,11Li) reaction at 70 MeV/nucleon is a good spectroscopic tool. We believe that the reaction can be well applied to the study of pure spin-flip nuclear responses in higher-excited regions including DGT and higher ?L excitations.

Takahisa, K.; Akimune, H.; Ejiri, H.; Fujimura, H.; Fujiwara, M.; Hara, K.; Hasimoto, H.; Hatanaka, K.; Itahasi, T.; Kawabata, T.; Kawase, K.; Koreeda, Y.; Maehara, N.; Mordechai, S.; Nagai, Y.; Nakanishi, K.; Ninomiya, S.; Shima, T.; Tanaka, M.; Umehara, S.; Umisedo, S.; Yoshida, H. P.; Yoshida, S.; Yoshimura, M.; Yosoi, M.

2005-12-01

319

Adiabatic transfer of coherences in a cluster of coupled nuclear spins  

SciTech Connect

It is experimentally demonstrated that quantum coherences can be efficiently transferred using adiabatic energy-level crossing. In a cluster of six dipolar-coupled proton spins of benzene, oriented by a liquid-crystalline matrix, a single-quantum coherence between one pair of states has been adiabatically transferred to another pair of states, and the superposition survived even after ten successive energy-level crossings.

Lee, Jae-Seung; Cardwell, Kate E.; Khitrin, A. K. [Department of Chemistry, Kent State University, Kent, Ohio 44242-0001 (United States)

2005-12-15

320

Research program in nuclear and solid state physics. [including pion absorption spectra and muon spin precession  

NASA Technical Reports Server (NTRS)

The survey of negative pion absorption reactions on light and medium nuclei was continued. Muon spin precession was studied using an iron target. An impulse approximation model of the pion absorption process implied that the ion will absorb almost exclusively on nucleon pairs, single nucleon absorption being suppressed by energy and momentum conservation requirements. For measurements on both paramagnetic and ferromagnetic iron, the external magnetic field was supplied by a large C-type electromagnet carrying a current of about 100 amperes.

1974-01-01

321

Nuclear quadrupolar spin-lattice relaxation in some III-V compounds  

Microsoft Academic Search

Measurements of the spin-lattice relaxation rates in the group-III-V compounds, GaAs, GaSb, InAs, and InSb, are presented as a function of temperature from 4 to 300 K. These rates, except for GaSb, are separated into magnetic and quadrupolar parts. The quadrupolar rates are separated into relaxation by acoustic phonons and that by optical phonons. A simple phenomenological model fits the

John A. McNeil; W. Gilbert Clark

1976-01-01

322

Experimental study of nuclear structure of 91 Mo at high spin  

NASA Astrophysics Data System (ADS)

The high spin structure of 91 Mo with neutron and proton number close to magicity has been investigated using the 63 Cu ( 31 P ,xnyp) reaction at an incident beam energy of 125 MeV . The level at Ex =3811 keV has been assigned a negative parity based on our polarization measurements. In view of this change, the observed level structure for 91 Mo so far does not have any negative parity sequence. More than 30 new transitions were observed and placed in the decay scheme, which has been extended up to spin of J˜39/2? and an excitation energy of Ex ˜10 MeV . The energy spectrum bears signature of core breaking viz. presence of high energy ( E? ˜2 MeV ) ? rays originating due to excitation of nucleons across the shell gaps. The proposed level scheme is compared with large basis spherical shell model calculations. Excitation of protons across Z=38 shell dominates the level structure up to moderate spins i.e., J˜27/2? . Configurations arising due to excitation of a single ? g9/2 across N=50 shell gap dominate the higher angular momentum J?35/2? states.

Ray, S.; Pattabiraman, N. S.; Goswami, R.; Ghugre, S. S.; Sinha, A. K.; Garg, U.

2004-05-01

323

Photochemically induced dynamic nuclear polarisation in entire bacterial photosynthetic units observed by 13C magic-angle spinning NMR  

NASA Astrophysics Data System (ADS)

Photochemically induced dynamic nuclear polarisation has been observed from entire photosynthetic units (PSUs) bound to chromatophore membrane (membrane-bound PSU) of the purple bacteria Rhodobacter sphaeroides, which have been selectively 13C-isotope enriched at all BChl and BPheo cofactors. These 1.5 MDa membrane-bound protein complexes comprise reaction centres as well as the antenna systems called light harvesting complexes I and II. Due to light-induced enhancement of nuclear polarisation, the 13C magic-angle spinning (MAS) NMR spectrum shows absorptive lines originating from the cofactors involved into the photochemical machinery and allowing the determination of the electronic ground state structure at atomic resolution. Addition of detergent released intact PSU from the chromatophore membrane (so called detergent solubilised PSU) and caused significant changes in the sign and intensity pattern of the light-induced MAS NMR spectrum. In contrast, detergent solubilised PSU and detergent solubilised bacterial reaction centres with the same isotope label pattern exhibit essentially the same chemical shifts with only minor differences in the intensity pattern. The pronounced differences between intact membrane-bound and detergent solubilised PSU are tentatively explained by the loss of self-orientation of the membrane-bound samples by solubilisation. This interpretation suggests that the theoretically predicted anisotropy of the light-induced nuclear polarisation has been observed for the first time.

Prakash, Shipra; Alia; Gast, Peter; Jeschke, Gunnar; de Groot, Huub J. M.; Matysik, Jörg

2003-12-01

324

Progress in Spin Dynamics Solid-State Nuclear Magnetic Resonance with the Application of Floquet-Magnus Expansion to Chemical Shift Anisotropy  

PubMed Central

The purpose of this article is to present an historical overview of theoretical approaches used for describing spin dynamics under static or rotating experiments in solid state nuclear magnetic resonance. The article gives a brief historical overview for major theories in nuclear magnetic resonance and the promising theories. We present the first application of Floquet-Magnus expansion to chemical shift anisotropy when irradiated by BABA pulse sequence.

Mananga, Eugene Stephane

2013-01-01

325

Pressure-induced changes of the vibrational modes of spin-crossover complexes studied by nuclear resonance scattering of synchrotron radiation  

NASA Astrophysics Data System (ADS)

Nuclear inelastic scattering (NIS) spectra were recorded for the spin-crossover complexes STP and ETP (STP = [Fe(1,1,1-tris{[N-(2-pyridylmethyl)-N-methylamino]methyl}-ethane)](ClO4)2 and ETP = [Fe(1,1,1-tris{[N-(2-pyridylmethyl)-N-methylamino]methyl}-butane)](ClO4)2) at 30 K and at room temperature and also at ambient pressure and applied pressure (up to 2.6 GPa). Spin transition from the high-spin (HS) to the low-spin (LS) state was observed by lowering temperature and also by applying pressure at room temperature and has been assigned to the hardening of iron-bond stretching modes due to the smaller volume in the LS isomer.

Trautwein, A. X.; Paulsen, H.; Winkler, H.; Giefers, H.; Wortmann, G.; Toftlund, H.; Wolny, J. A.; Chumakov, A. I.; Leupold, O.

2010-03-01

326

Optimization of data acquisition and processing in Carr-Purcell-Meiboom-Gill multiple quantum magic angle spinning nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

Data acquisition using the Carr-Purcell-Meiboom-Gill (CPMG) train of ? pulses has been recently explored in multiple quantum magic angle spinning (MQMAS) nuclear magnetic resonance of half-integer quadrupolar nuclei [T. Vosegaard, F. H. Larsen, H. J. Jakobsen, P. D. Ellis, and N. C. Nielsen, J. Am. Chem. Soc. 119, 9055 (1997)]. Significant increase of sensitivity can be obtained by using this technique at the expense of spectral definition, as the spectrum transforms into a manifold of narrow sidebands. A detailed analysis of the CPMG method, with emphasis on the MQMAS experiment, is presented. The MQ-QCPMG-MAS approach is adapted to spin-5/2 nuclei. Several numerical methods of data treatment are shown that allow for improvement of the definition of the sideband envelope, reconstruction of the standard line shape, and improvement of S/N ratio via optimized filtering. Theoretical and experimental estimates of signal enhancement through proper acquisition and processing of MQ-QCPMG-MAS data are given.

Lefort, R.; Wiench, J. W.; Pruski, M.; Amoureux, J.-P.

2002-02-01

327

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

PubMed

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-(13) C2 ]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 (13) C-labeled substrate through the increase in solvent water (1) H signal. PMID:24523064

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

2014-01-01

328

Frequency characteristics of a nuclear spin maser for the search for the electric dipole moment of 129Xe atom  

NASA Astrophysics Data System (ADS)

Frequency characteristics of a 129Xe nuclear spin maser was studied, which is under development at Tokyo Institute of Technology for the search for a permanent electric dipole moment in diamagnetic 129Xe atom. Drifts in the solenoid current and cell temperature were found to be the most influential factors on the maser frequency. From correlation coefficient analysis, there seem to exist other origins of frequency fluctuation, such as phase drifts in the maser oscillation. In order to improve the stability of the maser frequency, the intensity of the pumping laser required to fully polarize 129Xe nuclei was evaluated. Construction of a polarization assessment system for 129Xe gas cells and development of a new scheme of current stabilization are also remarked.

Inoue, T.; Tsuchiya, M.; Furukawa, T.; Hayashi, H.; Nanao, T.; Yoshimi, A.; Uchida, M.; Matsuo, Y.; Asahi, K.

2011-01-01

329

Spin-Echo Nuclear Magnetic Resonance Evidence for Complexing of Sodium Ions in Muscle, Brain, and Kidney  

PubMed Central

Na+ in muscle, brain, and kidney is shown by spin-echo nuclear magnetic resonance (NMR) to consist of two fractions with different NMR parameters. The slow fraction of Na+ in these tissues has NMR relaxation times T1 and T2 of 10-15 × 10-3 sec, which is approximately 4-5 times shorter than for Na+ in aqueous NaCl solution. The slow fraction may represent Na+ dissolved in structured tissue water. The fast fraction of tissue Na+, which is shown to represent approximately 65% of the total tissue Na+ concentration, has T2 less than 1 × 10-3 sec, which resembles the values of T2 observed for Na+ complexed by synthetic ion-exchange resins. One is drawn to the conclusion that approximately 65% of total Na+ in muscle, brain, and kidney is complexed by tissue macromolecules.

Cope, Freeman W.

1970-01-01

330

Development of a magic-angle spinning nuclear magnetic resonance probe with a cryogenic detection system for sensitivity enhancement  

NASA Astrophysics Data System (ADS)

A novel nuclear magnetic resonance (NMR) probe for high-resolution solid-state NMR has been developed. In this probe, temperature of the detection coil is kept at cryogenic temperature (~12 K) for sensitivity enhancement, which is achieved not only by suppression of thermal noise but also by increment of a Q factor of the coil. A marked feature of this probe is that a sample rotating at magic angle is thermally isolated from the cryogenic system in order to realize high-resolution solid-state NMR measurement at various sample temperatures. We call this system as cryocoil magic-angle spinning (cryocoil MAS). 1H MAS NMR with the coil temperature of ~20 K was successfully observed for solid adamantane rotating at room temperature, and signal-to-noise increment due to this cryocoil approach was confirmed.

Mizuno, Takashi; Hioka, Katsuya; Fujioka, Koji; Takegoshi, K.

2008-04-01

331

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

PubMed

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 (1)H relaxation in biological tissues, which is a prerequisite for unravelling the molecular basis of soft-tissue contrast in clinical magnetic resonance imaging. PMID:24116610

Chang, Zhiwei; Halle, Bertil

2013-10-14

332

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

333

Intramolecular hydrogen bonding as reflected in the deuterium isotope effects on carbon-13 chemical shifts. Correlation with hydrogen bond energies  

SciTech Connect

The carbon-13 resonances of atoms bearing phenolic or enolic hydroxyl groups, that are engaged in intramolecular hydrogen bonds, experience large (/sup 2/..delta.. may exceed 1 ppm) upfield deuterium isotope effects. The magnitude of the two-bond isotope effect, /sup 2/..delta.., correlates with the hydrogen bond energy as obtained from the hydroxyl proton chemical shift. In the conjugated systems investigated in this work, the isotope effects extend over several (up to six) chemical bonds. The signs and magnitudes of the long-range isotope effects are related to molecular structure.

Reuben, J.

1986-04-16

334

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.

335

Element-sensitive measurement of the hole-nuclear spin interaction in quantum dots  

NASA Astrophysics Data System (ADS)

It has been proposed that valence-band holes can form robust spin qubits owing to their weaker hyperfine coupling compared with electrons. However, it was demonstrated recently that the hole hyperfine interaction is not negligible, although a consistent picture of the mechanism controlling its magnitude is still lacking. Here we address this problem by measuring the hole hyperfine constant independently for each chemical element in InGaAs/GaAs, InP/GaInP and GaAs/AlGaAs quantum dots. Contrary to existing models we find that the hole hyperfine constant has opposite signs for cations and anions and ranges from -15% to +15% relative to that for electrons. We attribute such changes to the competing positive contributions of p-symmetry atomic orbitals and the negative contributions of d-orbitals. These findings yield information on the orbital composition of the valence band and enable a fundamentally new approach for verification of computed Bloch wavefunctions in semiconductor nanostructures. Furthermore, we show that the contribution of cationic d-orbitals leads to a new mechanism of hole spin decoherence.

Chekhovich, E. A.; Glazov, M. M.; Krysa, A. B.; Hopkinson, M.; Senellart, P.; Lemaître, A.; Skolnick, M. S.; Tartakovskii, A. I.

2013-02-01

336

Intermediate energy neutrons at WNR. Spin-isospin and energy dependence of the NN interaction and the nuclear response  

SciTech Connect

This report summarizes results of nuclear physics studies using intermediate energy (50-800 MeV) neutron probes carried out over the past five years using the Neutron Time-of-Flight (NTOF) Facility and Optically-Pumped Ion Source (OPPIS) at LAMPF and the `white` neutron source at the Weapons Neutron Research (WNR) facility. LAMPF did significant work in polarization transfer, while WNR took advantage of the wide neutron energy spectrum available to study energy dependent effects. The major focus of experiments with intermediate energy neutron probes for the next five years will be to explore fundamental details of the spin-isospin and energy dependence of the NN interaction and the nuclear response. To achieve this goal, the WNR white neutron source will be used for nucleon-nucleon and nucleon-nucleus interaction studies over a broad continuous range of incident neutron energy. Measurement of polarization observables using polarized targets or polarized beam should be possible, and will add an important extra dimension to these studies.

Taddeucci, T.N.

1995-02-01

337

Carbon-13 chemical shift tensors of disaccharides: measurement, computation and assignment.  

PubMed

A recently developed chemical shift anisotropy amplification solid-state nuclear magnetic resonance (NMR) experiment is applied to the measurement of the chemical shift tensors in three disaccharides: sucrose, maltose, and trehalose. The measured tensor principal values are compared with those calculated from first principles using density functional theory within the planewave-pseudopotential approach. In addition, a method of assigning poorly dispersed NMR spectra, based on comparing experimental and calculated shift anisotropies as well as isotropic shifts, is demonstrated. PMID:17999473

Shao, Limin; Yates, Jonathan R; Titman, Jeremy J

2007-12-20

338

Effects of Hindered Rotation on H2 Nuclear Spin Conversion on Ag(111)  

NASA Astrophysics Data System (ADS)

We investigated the effects of H2 hindered rotation on ortho--para (o--p) H2 conversion. To clarify the adsorption properties of H2 on Ag(111), we performed first-principles calculations based on spin-polarized density functional theory (DFT) with DFT-D2 method. We calculated the wave functions of nuclei of H2 from potential energy curves of H2 on Ag(111). From these results, we found that non-negligible out-of-plane potential anisotropy with a perpendicular orientation preference exists even on non-corrugated Ag(111). We also clarified that o--p H2 conversion is enhanced by H2 hindered rotation on Ag(111). This enhancement is induced by electron transfer from the surface to H2 with the perpendicular orientation preference.

Kunisada, Yuji; Kasai, Hideaki

2013-02-01

339

Nuclear spin relaxation in ionic dielectrics at low temperatures via conduction electrons in metallic covering  

NASA Astrophysics Data System (ADS)

We propose a method of obtaining of polarized nuclei in a crystal of ionic insulator, which is placed in a magnetic field and cooled to cryogenic temperatures. Polarization is a result of inelastic scattering of the conduction electrons of the metallic covering of a sample from the nuclei. This method (in a simplified form without the magnetic field) is suitable for obtaining aligned nuclei. We have derived the formulas (a) for the cross section of the process of electron-nucleus inelastic scattering, and (b) for the longitudinal relaxation time T1. As an example, we consider the spin relaxation process for the 93Nb nucleus inside the Nb2O5 dielectric sample with a gold covering.

Tkalya, E. V.

2012-11-01

340

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

341

Relaxation magnétique nucléaire du carbone-13 et dynamique des molécules de chlorpromazine associées en solution aqueuse  

NASA Astrophysics Data System (ADS)

13C relaxation times and heteronuclear NOE enhancements have been measured for chlorpromazine hydrochloride salt in chloroform and water. The dipolar contribution to 13C ^1H spin systems relaxation rates were extracted and allowed us to characterize the molecular reorientation in the two solvents. The correlation times are on either side of “T1 minimum". The values agree with the size of the molecule and show an association by stacking of 11 monomeric entities. Les temps de relaxation des 13C et les accroissements par effet Overhauser 1Hto13C ont été mesurés parallèlement sur la molécule de chlorhydrate de chlorpromazine non associée dans le chloroforme et auto-associée dans l'eau. L'extraction de la contribution dipolaire aux constantes de vitesse de relaxation des systèmes 13C 1H de la molécule a permis de caractériser la réorientation de la molécule dans les deux cas. Les temps de corrélation obtenus qui se situent de part et d'autre du “T1 minimum" sont en accord avec la taille de la molécule isolée et montrent que l'agrégat est formé par empilement de 11 molécules.

Compère, S.; Thévand, A.

1998-02-01

342

Paramagnetic carbon-13 shifts induced by the free radical tempo. 2. Nitrogen heterocycles  

SciTech Connect

With use of the free radical Tempo as a shift and relaxation reagent, both paramagnetic shifts and spin-lattice relaxation rates of nitrogen heterocycles are reported. Paramagnetic shifts of these compounds are larger than the corresponding shifts of the aromatic hydrocarbons, indicating a stronger interaction between nitrogen heterocyclic compounds and Tempo. Paramagnetic shifts increase with the number of nitrogen atoms per molecule. For pyridine type compounds, both shift and relaxation data show that the stronger interaction is not at the adjacent positions to the nitrogen atoms. It would appear in these heterocyclic complexes with Tempo that the nitrogen atoms tend to orient away from the N-O group in Tempo. In contrast, imidazole and indole exhibit a much stronger interaction with the Tempo due to hydrogen bond formation, and the positions near the N-H group exhibit larger paramagnetic shifts and relaxation rates. An approximate static model involving an indole-Tempo, hydrogen-bond complex accounts for the relaxation data from which both an equilibrium constant of complexation and a hydrogen-bond distance in the indole-Tempo complex could be estimated.

Qui, Z.W.; Grant, D.M.; Pugmire, R.J.

1984-02-08

343

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...

344

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...

345

Correlation of fast and slow chemical shift spinning sideband patterns under fast magic-angle spinning  

NASA Astrophysics Data System (ADS)

A new two-dimensional solid-state NMR experiment, which correlates slow and fast chemical shift anisotropy sideband patterns is proposed. The experiment, dubbed ROSES, is performed under fast magic-angle spinning and leads to an isotropic spectrum in the directly detected ?2 dimension. In the evolution dimension ?1, the isotropic chemical shift is reduced by a factor S, and spinning sidebands are observed spaced by a scaled effective spinning speed ?R/ S. These spinning sidebands patterns are not identical to those observed with standard slow magic-angle spinning experiments. Chemical shift anisotropy parameters can be accurately extracted with standard methods from these spinning sideband patterns. The experiment is demonstrated with carbon-13 experiments on powdered samples of a dipeptide and a cyclic undecapeptide, cyclosporin-A.

Eléna, Bénédicte; Hediger, Sabine; Emsley, Lyndon

2003-01-01

346

Intersubunit communication in tryptophan synthase by carbon-13 and fluorine-19 REDOR NMR.  

PubMed

The beta subunits of the 143-kDa alpha2beta2 tetrameric enzyme tryptophan synthase have been labeled by L-[ring-4-19F]phenylalanine and L-[phenol-4-13C]tyrosine in an effort to monitor the positions of these residues on ligand binding. Of the 13 phenylalanine and 11 tyrosine residues in the beta subunit, only three pairs have labels with 13C-19F separations of less than 6 angstrom. The beta subunit residues Tyr279 and Phe280 (each members of one of the three Tyr-Phe proximate pairs) have been suggested as possible conformational gates on ligand binding. The 188-MHz 19F NMR spectrum of the microcrystalline, double-labeled enzyme complex has five resolved lines under 5-kHz magic-angle spinning and 80-kHz proton dipolar decoupling. The distribution of beta-subunit 19F isotropic shifts is altered by addition of L-[3-13C]-serine to the mother liquor in contact with the microcrystals, consistent with a conformational rearrangement. The 13C label from serine is detected at 28 ppm as a methyl tautomer of bound aminoacrylate. The change in aromatic 19F chemical shifts on binding of serine indicates an alteration in local electric field gradients within the beta subunit. However, rotational-echo double-resonance 13C NMR (with 19F dephasing) shows that the average 13C-19F distance for the three phenylalanine-tyrosine proximate pairs in the beta subunit is changed by less than 1 angstrom. PMID:8605170

McDowell, L M; Lee, M; McKay, R A; Anderson, K S; Schaefer, J

1996-03-12

347

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

348

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

349

Nuclear magnetic resonance data of C36H80BN  

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.

350

Nuclear magnetic resonance data of C30H22OSe  

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.

351

Nuclear magnetic resonance data of C30H68BN  

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.

352

Nuclear magnetic resonance data of C30H50Si  

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.

353

Nuclear magnetic resonance data of C30H25Sb  

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.

354

Nuclear magnetic resonance data of C35H35As  

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.

355

Nuclear magnetic resonance data of C35H35Sb  

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.

356

Nuclear magnetic resonance data of C30H25As  

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.

357

Nuclear magnetic resonance data of C30H22SSe  

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.

358

Nuclear magnetic resonance data of CF2Se  

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.

359

Nuclear magnetic resonance data of CF3NSe  

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.

360

Nuclear magnetic resonance data of C28 H56  

NASA Astrophysics Data System (ADS)

This document is part of Part 1 `Aliphatic 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'.

Kalinowski, H.-O.; Kumar, M.; Gupta, V.; Gupta, R.

361

Nuclear magnetic resonance spectra for l > 1 spins in dynamically heterogeneous systems with chemical exchange among environments.  

PubMed Central

Nuclear magnetic resonance spectra for nuclei with spin l > 1 are considered in cases in which the observed nucleus may sample a rotationally immobilized and an isotropic environment that are coupled by a chemical exchange process. Spectra are simulated for the central (1/2, -1/2) transition for a 3/2 nucleus as a function of the concentrations of the two environments and as a function of the exchange rate between them. It is shown that a crucial feature determining the shape of the observable spectra is the spatial extent or the local order in the immobilized phase. In the case for which all rotationally immobilized sites sampled by the exchanging nucleus are identically oriented but where there is a distribution of these microdomain orientations with respect to the magnetic field direction, a powder pattern for the central transition is observed that carries whatever dynamic information may be derived from it. In the fast exchange limit, the width of the powder pattern scales inversely with the concentration of the isotropic environment as usual. In the intermediate exchange regimes, a complex line shape results that may mask the anisotropic character of the spectrum. In the slow exchange limit, superposition of the spectral contributions results; however, if the isotropic environment concentration is significantly larger than the anisotropic environment concentration, the anisotropic contribution is very difficult to detect because of the dynamic range problem and the possibly large difference in the effective line widths. In the case for which the exchanging nucleus samples a considerable distribution of rotationally immobilized site orientations, the anisotropic character of the spectrum is lost and a super-Lorentzian line shape results. These effects are demonstrated experimentally by 35Cl nuclear magnetic resonance spectra obtained on a lamellar liquid crystal that is modified with the addition of a thiolmercurate to provide a site of large quadrupole coupling constant and with cross-linked bovine serum albumin gels.

Zhang, H; Bryant, R G

1995-01-01

362

Nuclear magnetic resonance spectra for l > 1 spins in dynamically heterogeneous systems with chemical exchange among environments.  

PubMed

Nuclear magnetic resonance spectra for nuclei with spin l > 1 are considered in cases in which the observed nucleus may sample a rotationally immobilized and an isotropic environment that are coupled by a chemical exchange process. Spectra are simulated for the central (1/2, -1/2) transition for a 3/2 nucleus as a function of the concentrations of the two environments and as a function of the exchange rate between them. It is shown that a crucial feature determining the shape of the observable spectra is the spatial extent or the local order in the immobilized phase. In the case for which all rotationally immobilized sites sampled by the exchanging nucleus are identically oriented but where there is a distribution of these microdomain orientations with respect to the magnetic field direction, a powder pattern for the central transition is observed that carries whatever dynamic information may be derived from it. In the fast exchange limit, the width of the powder pattern scales inversely with the concentration of the isotropic environment as usual. In the intermediate exchange regimes, a complex line shape results that may mask the anisotropic character of the spectrum. In the slow exchange limit, superposition of the spectral contributions results; however, if the isotropic environment concentration is significantly larger than the anisotropic environment concentration, the anisotropic contribution is very difficult to detect because of the dynamic range problem and the possibly large difference in the effective line widths. In the case for which the exchanging nucleus samples a considerable distribution of rotationally immobilized site orientations, the anisotropic character of the spectrum is lost and a super-Lorentzian line shape results. These effects are demonstrated experimentally by 35Cl nuclear magnetic resonance spectra obtained on a lamellar liquid crystal that is modified with the addition of a thiolmercurate to provide a site of large quadrupole coupling constant and with cross-linked bovine serum albumin gels. PMID:7647258

Zhang, H; Bryant, R G

1995-06-01

363

In vivo studies of pyridine nucleotide metabolism in Escherichia coli and Saccharomyces cerevisiae by carbon-13 NMR spectroscopy  

SciTech Connect

Pyridine nucleotide metabolism has been studied in vivo in a prokaryotic (Escherichia coli) and a eukaryotic (Saccharomyces cerevisiae) system cultured in a medium containing carbon-13-labeled nicotinic acid, followed by NMR detection of the labeled organisms. Chemical exchange between oxidized and reduced nucleotides is found to be sufficiently slow on the NMR time scale to permit the observation of separate resonances corresponding to each redox state. The possibility of significant exchange broadening of reduced pyridine nucleotide resonances under some conditions was further evaluated based on comparative NMR studies utilizing organisms cultured in the presence of either (2-/sup 13/C)nicotinate or (5-/sup 13/C)nicotinate. Based on these experiments, it was concluded that broadening as a consequence of intermediate exchange is not significant. Although it was initially anticipated that the carbon-13 resonances arising from the di- and triphosphopyridine nucleotide pools could not be distinguished, the absence of observable resonances corresponding to reduced nucleotides in oxygenated yeast and E. coli cells suggests that the NMR method is fairly specific for determining the redox status of the diphosphopyridine nucleotide pool. Studies of the effects of a variety of perturbations including variation of the oxygen supply, addition of ethanol, and addition of the oxidative phosphorylation uncoupler dinitrophenol have been carried out. Dramatic differences in the response of the catabolic reduction charge, CRC = (NADH)/(NADH) + (NAD/sup +/), between the yeast and E. coli cells are observed. The CRC values for the yeast undergo large changes in response to these perturbations which are not observed for the bacterial cells. 52 references, 9 figures, 2 tables.

Unkefer, C.J.; London, R.E.

1984-02-25

364

Preparation of highly polarized nuclei: Observation and control of time-dependent polarization transfer from H{sup 35}Cl molecular rotation to {sup 35}Cl nuclear spin  

SciTech Connect

We demonstrate time-dependent polarization transfer from molecular rotation to nuclear spin. The H{sup 35}Cl (v=2,J=1,M=1) state is excited with a 1.7 {mu}m laser pulse, and then dissociated with a delayed 235 nm laser pulse to produce {sup 35}Cl atoms. Time-dependent polarizations of both H{sup 35}Cl (v=2,J=1) molecules and {sup 35}Cl({sup 2}P{sub 3/2}) atoms, which vary due to hyperfine quantum beating, are measured. The {sup 35}Cl nuclear spin is highly polarized ({approx_equal}1.1) at a pump-probe delay of 145 ns. Densities surpassing 10{sup 14} cm{sup -3} are achieved. The technique is applicable to many atoms not amenable to optical pumping.

Sofikitis, Dimitris; Rakitzis, T. Peter [Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, 71110 Heraklion-Crete (Greece); Department of Physics, University of Crete, P.O. 2208, 71003 Voutes-Heraklion (Greece); Rubio-Lago, Luis [Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, 71110 Heraklion-Crete (Greece); Martin, Marion R.; Brown, Davida J. Ankeny; Bartlett, Nathaniel C.-M.; Zare, Richard N. [Department of Chemistry, Stanford University, Stanford, California 94305-5080 (United States)

2007-07-15

365

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

366

THE LOW-TEMPERATURE NUCLEAR SPIN EQUILIBRIUM OF H{sup +} {sub 3} IN COLLISIONS WITH H{sub 2}  

SciTech Connect

Recent observations of H{sub 2} and H{sup +} {sub 3} in diffuse interstellar sightlines revealed a difference in the nuclear spin excitation temperatures of the two species. This discrepancy comes as a surprise, as H{sup +} {sub 3} and H{sub 2} should undergo frequent thermalizing collisions in molecular clouds. Non-thermal behavior of the fundamental H{sup +} {sub 3}/H{sub 2} collision system at low temperatures was considered as a possible cause for the observed irregular populations. Here, we present measurements of the steady-state ortho/para ratio of H{sup +} {sub 3} in collisions with H{sub 2} molecules in a temperature-variable radiofrequency ion trap between 45 and 100 K. The experimental results are close to the expected thermal outcome and they agree very well with a previous micro-canonical model. We briefly discuss the implications of the experimental results for the chemistry of the diffuse interstellar medium.

Grussie, F.; Berg, M. H.; Wolf, A.; Kreckel, H. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Crabtree, K. N.; McCall, B. J. [Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Gaertner, S.; Schlemmer, S., E-mail: holger.kreckel@mpi-hd.mpg.de [I. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Str. 77, D-50937 Koeln (Germany)

2012-11-01

367

Nuclear-spin relaxation due to translational diffusion in a hexatic-B and crystalline-B phase  

NASA Astrophysics Data System (ADS)

The general theory of nuclear-spin relaxation induced by translational self-diffusion in liquid crystals, developed in previous papers, is applied to the crystalline-B and hexatic-B phases of smectics by taking into account their characteristic features concerning molecular positional ordering, the inter-and intralayer molecular jumps, and the correlation in the layer stacking. The evaluated anisotropy and dispersion of T1 and T1? are presented graphically for a variety of parameters. It is shown that in most cases T1?, due to translational diffusion, has a characteristic anisotropy and dispersion while T1 is expected to be nearly isotropic and with ?2-type dispersion at usual NMR frequencies. The relaxation study cannot discriminate between various types of the interlayer and intralayer correlations occurring in the crystalline-B and hexatic-B phases of the smectics except in the case when relative layer motions are fast compared to the diffusion. The comparison of the theoretical relation and experimental data enables the determination of diffusion constant D? in the smectic-B phases while the ratio D?D? could be determined only via precise study of the T1? angular dependence. With the application of the theory to available T1 data of the smectic-B phase of N-[4-(n-dodecanoyl) benzylidene]-4'-aminoazobenzene (C12BAA) and of the smectic-Bc phase of terephthal-bis(4-n-butylaniline) (TBBA), the corresponding D? are estimated.

Žumer, S.; Vilfan, M.

1983-11-01

368

Method for accurate measurements of nuclear-spin optical rotation for applications in correlated optical-NMR spectroscopy.  

PubMed

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. PMID:23685716

Savukov, I M; Chen, H-Y; Karaulanov, T; Hilty, C

2013-07-01

369

Nutation frequency modulation on NMR signal of nuclear spins in chemical exchange with solvent water under the BEST conditions.  

PubMed

Solvent exchange properties of protein backbone amide protons provide valuable residue-specific information on protein solvent accessibility, structure stability and flexibility and hence are of significant interest in structural biology. NMR has served as a unique means for the characterization of chemical exchange including proton amide exchange with solvent water at residue-specific levels across a broad range of exchange rates. One of the methods used for the characterization of protein backbone amide exchange by NMR involves the use of progressive selective irradiation of the water resonance. Here, we report the experimental observation of the nutation frequency (strength of RF field used for the irradiation of water resonance) modulation on amide proton signals for those in exchange with the solvent water under the band-selective excitation short transient (BEST) conditions. Compared with conventional saturation transfer of water magnetization experiments, this nutation frequency modulation observed on signal of nuclear spins under the BEST conditions potentially offers a quick identification of protein backbone amides in rapid exchange with solvent water. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24459096

Yao, Shenggen; Keizer, David W

2014-04-01

370

Nuclear spin dependence of the reaction of H{sub 3}{sup +} with H{sub 2}. I. Kinetics and modeling  

SciTech Connect

The chemical reaction H{sub 3}{sup +}+ H{sub 2}{yields} H{sub 2}+H{sub 3}{sup +} is the simplest bimolecular reaction involving a polyatomic, yet is complex enough that exact quantum mechanical calculations to adequately model its dynamics are still unfeasible. In particular, the branching fractions for the ''identity,''''proton hop,'' and ''hydrogen exchange'' reaction pathways are unknown, and to date, experimental measurements of this process have been limited. In this work, the nuclear-spin-dependent steady-state kinetics of the H{sub 3}{sup +}+ H{sub 2} reaction is examined in detail, and employed to generate models of the ortho:para ratio of H{sub 3}{sup +} formed in plasmas of varying ortho:para H{sub 2} ratios. One model is based entirely on nuclear spin statistics, and is appropriate for temperatures high enough to populate a large number of H{sub 3}{sup +} rotational states. Efforts are made to include the influence of three-body collisions in this model by deriving nuclear spin product branching fractions for the H{sub 5}{sup +}+ H{sub 2} reaction. Another model, based on rate coefficients calculated using a microcanonical statistical approach, is appropriate for lower-temperature plasmas in which energetic considerations begin to compete with the nuclear spin branching fractions. These models serve as a theoretical framework for interpreting the results of laboratory studies on the reaction of H{sub 3}{sup +} with H{sub 2}.

Crabtree, Kyle N.; Tom, Brian 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

371

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

372

Nuclear spin-lattice relaxation of 139La in the superconducting phase of La1.8Sr0.2CuO4- delta  

Microsoft Academic Search

We report on zero-field nuclear spin-lattice relaxation measurements of 139La in La1.8Sr0.2CuO4-? in the normal and the superconducting state. Below the superconducting transition temperature Tc the relaxation rate behaves like 1\\/T1 ? exp [- ?\\/kT] with activation energy ? = 11.5 meV leading to a gap energy of 2? = 23 meV. With Tc = 38 K the ratio 2?\\/kTc

H. Seidel; F. Hentsch; M. Mehring; J. G. Bednorz; K. A. Müller

1988-01-01

373

Hyperfine anomaly arising from the nuclear spin-forbidden transition and absolute sign determination of the zero-field splitting constant  

Microsoft Academic Search

It has been found in the triplet E.S.R. spectra of radical pairs in irradiated potassium deuterium fumarate that the hyperfine structure of the two transitions, Ms = 1?0 and Ms = 0?+1, are entirely different. This anomaly has been interpreted in terms of the forbidden transition arising from the mixing of the nuclear spin states by the anisotropic hyperfine interaction.

Kayoko Minakata; Machio Iwasaki

1972-01-01

374

Population and Decay of High-Spin States in /Sup 157-161/Yb: Evolution of Nuclear Shapes as a Function Spin and Neutron Number.  

National Technical Information Service (NTIS)

The population and decay of the entry states in /sup 157-161/Yb and /sup 155-158/Er from the reactions of 136- and 149-MeV exp 20 Ne with exp 144 Nd and exp 146 Nd have been investigated with the Spin Spectrometer gated with a Ge detector. Statistical-mod...

M. Jaeaeskelaeinen D. G. Sarantites F. A. Dilmanian R. Woodward H. Puchta

1982-01-01

375

The nuclear-spin-rotation constants of HCY, HSiY, and SiY2 (Y=F, Cl): An ab initio study  

NASA Astrophysics Data System (ADS)

The nuclear-spin-rotation constants of fluoro- (HCF) and chloro- (HCCl) carbene, of the corresponding silylenes (HSiF and HSiCl), and of difluoro- and dichlorosilylene (SiF2 and SiCl2) are quantum-chemically investigated employing the coupled-cluster singles and doubles model augmented by a perturbative treatment of triple excitations together with various sequences of correlation-consistent basis sets. Theoretical best estimates are obtained through consideration of corrections for core correlation and of zero-point vibrational contributions. In addition, nuclear quadrupole coupling constants for the chlorine containing species are determined. A thorough comparison with experiment is made.

Rizzo, Antonio; Puzzarini, Cristina; Coriani, Sonia; Gauss, Jürgen

2006-02-01

376

The nuclear-spin-rotation constants of HCY, HSiY, and SiY(2) (Y=F, Cl): an ab initio study.  

PubMed

The nuclear-spin-rotation constants of fluoro- (HCF) and chloro- (HCCl) carbene, of the corresponding silylenes (HSiF and HSiCl), and of difluoro- and dichlorosilylene (SiF(2) and SiCl(2)) are quantum-chemically investigated employing the coupled-cluster singles and doubles model augmented by a perturbative treatment of triple excitations together with various sequences of correlation-consistent basis sets. Theoretical best estimates are obtained through consideration of corrections for core correlation and of zero-point vibrational contributions. In addition, nuclear quadrupole coupling constants for the chlorine containing species are determined. A thorough comparison with experiment is made. PMID:16483202

Rizzo, Antonio; Puzzarini, Cristina; Coriani, Sonia; Gauss, Jürgen

2006-02-14

377

Nuclear Spin Effects in the Reactions of H3^+ with H2 and Electrons  

NASA Astrophysics Data System (ADS)

H3^+ is the simplest polyatomic molecule. It is widely used as a benchmark for theoretical calculations of molecular spectroscopy and reaction dynamics, and also plays a pivotal role as the cornerstone of interstellar chemistry. In Urbana, we have investigated the proton hop/exchange reaction H3^+ + H2 -> (H5^+)^* -> H2 + H3^+ for the first time at low temperatures. This reaction is the simplest bimolecular reaction involving a polyatomic, and is also the most common bimolecular reaction in the universe. Our experiments have revealed the branching ratio between proton hop and exchange, and appear to explain the observed ortho:para ratio of H3^+ in diffuse interstellar clouds. At the TSR storage ring of the Max Planck Institute for Nuclear Physics in Heidelberg, we have performed high-resolution measurements of the dissociative recombination (DR) cross sections of cold H3^+ in different mixtures of its lowest ortho and para quantum states. These measurements represent an important step towards the first state-selected DR measurements.

Kreckel, Holger; Crabtree, Kyle; Kauffman, Carrie; Tom, Brian; Novotny, Oldrich; Berg, Max; Bing, Dennis; Buhr, Henrik; Krantz, Claude; Lestinsky, Michael; Mendes, Mario; Nordhorn, Christian; Stutzel, Julia; Wolf, Andreas; Thomas, Richard; McCall, Benjamin

2010-03-01

378

Nuclear properties of the exotic high-spin isomer {sup 178m2}Hf  

SciTech Connect

The complete hyperfine spectrum in the optical transition 5d{sup 2}6s{sup 2} 3{sup P}2{yields}5d6s{sup 2}6p {sup 1}P1 of {sup 178m2}Hf was recorded by collinear laser spectroscopy using nanogram amounts of samples. The quadrupole moment and isomer shift were determined for the first time as well as a precise value and the sign of the magnetic dipole moment. The change in nuclear mean-square charge radius between the isomeric state {sup 178m2}Hf and the ground state {sup 178g}Hf was evaluated as {delta}{sup 178,178m2}=-0.059(9) fm{sup 2}. From the hyperfine A- and B-factors the magnetic moment {gamma}I{sup 178m2}=+8.16(4){mu}N and the spectroscopic quadrupole moment Q{sup 178m2}s=6.00(7) b were extracted. In an additional experiment using a RIS scheme we recorded the A- and B-factors and the isotope shift of the 5d{sup 2}6s{sup 23} F3{yields}5d{sup 2}6s6p {sup 3}G4 and the 5d{sup d}6s{sup 2} {sup 3}P0{yields}5d{sup 2}6s6p {sup 3}D1 transition.

Krieg, M.; Boos, N.; Le Blanc, F.; Pinard, J.; Huber, G.; Lunney, M. D.; Le Du, D.; Meunier, R.; Hussonnois, M.; Constantinescu, O.; Kim, J. B.; Briancon, Ch.; Crawford, J. E.; Duong, H. T.; Gangrski, Y. P.; Kuehl, T.; Markov, B. N.; Oganessian, Yu. Ts.; Quentin, P.; Roussiere, B. [Institut fuer Physik der Universitaet Mainz, 55099 Mainz (Germany) and Institut fuer Physik der Universitaet Mainz, 55099 Mainz (Germany) and Institut de Physique Nucleaire, IN2P3-CNRS, 91406 Orsay (France) and Institut de Physique Nucleaire, IN2P3-CNRS, 91406 Orsay (France); Institut fuer Physik der Universitaet Mainz, 55099 Mainz (Germany); Laboratoire Aime Cotton, 91405 Orsay (France); Institut fuer Physik der Universitaet Mainz, 55099 Mainz (Germany); CSNSM-Orsay, IN2P3-CNRS, 91405 Orsay (France); Foster Radiation Laboratory, McGill University, Montreal (Canada); Laboratoire Aime Cotton, 91405 Orsay (France); JINR Dubna, POB 79, 101000 Moscow Region (Russian Federation); GSI, 64291 Darmstadt (Germany); JINR Dubna, POB 79, 101000 Moscow Region (Russian Federation)] (and others)

1995-04-01

379

Nuclear spin-spin coupling constants from regular approximate relativistic density functional calculations. I. Formalism and scalar relativistic results for heavy metal compounds  

NASA Astrophysics Data System (ADS)

We present a relativistic formulation of the spin-spin coupling hyperfine terms based on the two component zeroth-order regular approximate Hamiltonian. The scalar relativistic parts of the resulting operators were used for an implementation into the Amsterdam density functional program. Application of the code for the calculation of one-bond metal-ligand couplings of systems containing 183W, 195Pt, 199Hg, and 207Pb shows that scalar relativistic calculations are able to reproduce major parts of the relativistic effects on the coupling constants, which can be even larger in magnitude than the respective total nonrelativistic values. The spatial origin of the regular approximate relativistic analogue of the Fermi-contact contribution, which is usually responsible for the strong relativistic increase of the couplings, is analyzed. Its relativistic effects can be described by the relativistic increase of valence orbital density in the very vicinity of the heavy nucleus.

Autschbach, Jochen; Ziegler, Tom

2000-07-01

380

Detailed analysis of the S-RESPDOR solid-state NMR method for inter-nuclear distance measurement between spin-1/2 and quadrupolar nuclei.  

PubMed

We present a detailed analysis of the Symmetry-based Resonance-Echo Saturation-Pulse DOuble-Resonance (S-RESPDOR) method in order to measure the inter-nuclear distances between spin-1/2 and quadrupolar nuclei. This recently introduced sequence employs a symmetry-based recoupling scheme on the observed spin-1/2 channel and a saturation pulse on the quadrupolar channel. This method requires a low radio-frequency (rf) field, is compatible with high MAS frequency and allows a rapid determination of inter-nuclear distances by fitting the experimental signal fraction to an analytical expression. Here, we analyze in detail the influence of the various experimental and spin-interaction parameters on the S-RESPDOR signal fraction and the measured distance. We show that the S-RESPDOR signal fraction only depends on the quadrupole interaction and the inter-nuclear distance. We demonstrate that the required rf-field on the quadrupolar channel is smaller than that required for an adiabatic-passage pulse in REAPDOR-type experiments. The only limitation of the method is the requirement of accurate rotor synchronization between the two parts of the dipolar recoupling sequences. Using S-RESPDOR, we have quantitatively measured a (31)P-(51)V distance of 357 pm in a mono-vanadium-substituted polyoxo-tungstate, K(4)PVW(11)O(40), from the Keggin family and a (13)C-(67)Zn distance of 286 pm in [80%-(67)Zn]zinc [1-(13)C]acetate. These results show that S-RESPDOR can be employed in the challenging cases of quadrupolar nuclei exhibiting a high spin number and either large chemical-shift anisotropy ((51)V) or low gyromagnetic ratio ((67)Zn). PMID:22257437

Lu, Xingyu; Lafon, Olivier; Trébosc, Julien; Amoureux, Jean-Paul

2012-02-01

381

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

Microsoft Academic Search

It is shown that HYSCORE spectra of paramagnetic centers having nuclei of spin I=1 with isotropic hfi and arbitrary NQI consist of ridges having zero width. A parametric presentation of these ridges is found which shows the range of possible frequencies in the HYSCORE spectrum and aids in spectral assignments and rapid estimation of spin Hamiltonian parameters. An alternative approach

Alexander G. Maryasov; Michael K. Bowman

2004-01-01

382

Slow magic angle sample spinning: a non- or minimally invasive method for high-resolution 1H nuclear magnetic resonance (NMR) metabolic profiling.  

PubMed

High-resolution (1)H magic angle spinning nuclear magnetic resonance (NMR), using a sample spinning rate of several kilohertz 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 minimally 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 H(2)O, where an unusually large magnetic susceptibility field gradient is obtained. PMID:21207300

Hu, Jian Zhi

2011-01-01

383

A nuclear magnetic resonance spectrometer concept for hermetically sealed magic angle spinning investigations on highly toxic, radiotoxic, or air sensitive materials.  

PubMed

A concept to integrate a commercial high-resolution, magic angle spinning nuclear magnetic resonance (MAS-NMR) probe capable of very rapid rotation rates (70 kHz) in a hermetically sealed enclosure for the study of highly radiotoxic materials has been developed and successfully demonstrated. The concept centres on a conventional wide bore (89 mm) solid-state NMR magnet operating with industry standard 54 mm diameter probes designed for narrow bore magnets. Rotor insertion and probe tuning take place within a hermetically enclosed glovebox, which extends into the bore of the magnet, in the space between the probe and the magnet shim system. Oxygen-17 MAS-NMR measurements demonstrate the possibility of obtaining high quality spectra from small sample masses (~10 mg) of highly radiotoxic material and the need for high spinning speeds to improve the spectral resolution when working with actinides. The large paramagnetic susceptibility arising from actinide paramagnetism in (Th(1-x)U(x))O2 solid solutions gives rise to extensive spinning sidebands and poor resolution at 15 kHz, which is dramatically improved at 55 kHz. The first (17)O MAS-NMR measurements on NpO(2+x) samples spinning at 55 kHz are also reported. The glovebox approach developed here for radiotoxic materials can be easily adapted to work with other hazardous or even air sensitive materials. PMID:23742594

Martel, L; Somers, J; Berkmann, C; Koepp, F; Rothermel, A; Pauvert, O; Selfslag, C; Farnan, I

2013-05-01

384

Unusual spin fluctuations and magnetic frustration in olivine and non-olivine LiCoPO4 detected by P31 and Li7 nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

We report P31 and Li7 nuclear magnetic resonance (NMR) studies in new non-olivine LiZnPO4-type LiCoPO4tetra microcrystals, where the Co2+ ions are tetrahedrally coordinated. Olivine LiCoPO4, which was directly transformed from LiCoPO4tetra by an annealing process, was also studied and compared. The uniform bulk magnetic susceptibility and the P31 Knight shift obey the Curie-Weiss law for both materials with a high spin Co2+ (3d7, S =3/2), but the Weiss temperature ? and the effective magnetic moment ?eff are considerably smaller in LiCoPO4tetra. The spin-lattice relaxation rate T1-1 reveals a quite different nature of the spin dynamics in the paramagnetic state of both materials. Our NMR results imply that strong geometrical spin frustration occurs in tetrahedrally coordinated LiCoPO4, which may lead to the incommensurate magnetic ordering.

Baek, S.-H.; Klingeler, R.; Neef, C.; Koo, C.; Büchner, B.; Grafe, H.-J.

2014-04-01

385

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

386

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

387

Vibrational spectrum of the spin crossover complex [Fe(phen)(2)(NCS)(2)] studied by IR and Raman spectroscopy, nuclear inelastic scattering and DFT calculations.  

PubMed

The vibrational modes of the low-spin and high-spin isomers of the spin crossover complex [Fe(phen)(2)(NCS)(2)] (phen = 1,10-phenanthroline) have been measured by IR and Raman spectroscopy and by nuclear inelastic scattering. The vibrational frequencies and normal modes and the IR and Raman intensities have been calculated by density functional methods. The vibrational entropy difference between the two isomers, DeltaS(vib), which is--together with the electronic entropy difference DeltaS(el)--the driving force for the spin-transition, has been determined from the measured and from the calculated frequencies. The calculated difference (DeltaS(vib) = 57-70 J mol(-1) K(-1), depending on the method) is in qualitative agreement with experimental values (20-36 J mol(-1) K(-1)). Only the low energy vibrational modes (20% of the 147 modes of the free molecule) contribute to the entropy difference and about three quarters of the vibrational entropy difference are due to the 15 modes of the central FeN(6) octahedron. PMID:17047767

Ronayne, Kate L; Paulsen, Hauke; Höfer, Andreas; Dennis, Andrew C; Wolny, Juliusz A; Chumakov, Aleksandr I; Schünemann, Volker; Winkler, Heiner; Spiering, Hartmut; Bousseksou, Azzedine; Gütlich, Philipp; Trautwein, Alfred X; McGarvey, John J

2006-10-28

388

A nuclear magnetic resonance spectrometer concept for hermetically sealed magic angle spinning investigations on highly toxic, radiotoxic, or air sensitive materials  

NASA Astrophysics Data System (ADS)

A concept to integrate a commercial high-resolution, magic angle spinning nuclear magnetic resonance (MAS-NMR) probe capable of very rapid rotation rates (70 kHz) in a hermetically sealed enclosure for the study of highly radiotoxic materials has been developed and successfully demonstrated. The concept centres on a conventional wide bore (89 mm) solid-state NMR magnet operating with industry standard 54 mm diameter probes designed for narrow bore magnets. Rotor insertion and probe tuning take place within a hermetically enclosed glovebox, which extends into the bore of the magnet, in the space between the probe and the magnet shim system. Oxygen-17 MAS-NMR measurements demonstrate the possibility of obtaining high quality spectra from small sample masses (~10 mg) of highly radiotoxic material and the need for high spinning speeds to improve the spectral resolution when working with actinides. The large paramagnetic susceptibility arising from actinide paramagnetism in (Th1-xUx)O2 solid solutions gives rise to extensive spinning sidebands and poor resolution at 15 kHz, which is dramatically improved at 55 kHz. The first 17O MAS-NMR measurements on NpO2+x samples spinning at 55 kHz are also reported. The glovebox approach developed here for radiotoxic materials can be easily adapted to work with other hazardous or even air sensitive materials.

Martel, L.; Somers, J.; Berkmann, C.; Koepp, F.; Rothermel, A.; Pauvert, O.; Selfslag, C.; Farnan, I.

2013-05-01

389

Anomalous enrichment of {sup 17}O and {sup 13}C in photodissociation products of CO{sub 2}: Possible role of nuclear spin  

SciTech Connect

Oxygen and carbon isotope fractionation associated with products (CO and O{sub 2}) of gas phase photodissociation of CO{sub 2} have been studied using photons from Hg lamp (184.9 nm) and Kr lamp (123.6 and 116.5 nm). In dissociation by Hg lamp photons both CO and O{sub 2} are enriched in {sup 17}O by about 81 per mille compared to the estimate based on a kinetic model. Additionally, CO is enriched in {sup 13}C by about 37 per mille relative to the model composition. In contrast, in dissociation by higher energy Kr lamp photons no such anomaly was found in O{sub 2}. The observed isotopic enrichments in case of Hg lamp dissociation are proposed to be due to a hyperfine interaction between nuclear spin and electron spins or orbital motion causing enhanced dissociation of isotopologues of CO{sub 2} containing {sup 17}O and {sup 13}C. The {sup 17}O enrichment is higher than that of {sup 13}C by a factor of 2.2{+-}0.2 which can be explained by the known magnetic moment ratio of {sup 17}O and {sup 13}C due to differing nuclear spins and g-factors. These results have potential implications in studies of the planetary atmospheres.

Mahata, Sasadhar; Bhattacharya, S. K. [Physical Research Laboratory, Navrangpura, Ahmedabad 380 009 (India)

2009-06-21

390

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

391

Conformation of methyl beta-lactoside bound to the ricin B-chain: Interpretation of transferred nuclear Overhauser effects facilitated by spin simulation and selective deuteration  

SciTech Connect

Spin simulation and selective deuteration have been used to aid in the interpretation of 1D transferred nuclear Overhauser effect (TRNOE) NMR experiments on ricin B-chain/ligand systems. Application of these methods has revealed a change in the conformation of deuterated methyl beta-lactoside upon binding to the ricin B-chain which results in a slight change in glycosidic torsional angels which appear to dominate in the solution conformation. The combination of simulation and experiment also shows an important sensitivity of TRNOE magnitudes to dissociation rate constants and available spin-diffusion pathways for the ricin B-chain/ligand systems under study. The sensitivity to dissociation rates allows determination of rate constants for methyl beta-lactoside and methyl beta-galactoside of 50 and 300 s-1, respectively.

Bevilacqua, V.L.; Thomson, D.S.; Prestegard, J.H. (Yale Univ., New Haven, CT (USA))

1990-06-12

392

Electron spin-echo envelope modulation and pulse electron nuclear double resonance studies of Cu2+...beta-carotene interactions in Cu-MCM-41 molecular sieves.  

PubMed

Perdeuterated all-trans beta-carotene imbedded in activated Cu-MCM-41 was examined by electron paramagnetic resonance (EPR) and electron spin-echo envelope modulation (ESEEM) spectroscopies. The EPR study showed that complexation and electron transfer between Cu2+ and deuterated beta-carotene occurs. The interaction was confirmed by detecting the spin-echo modulation of deuterium in the ESEEM spectra of Cu2+. Ratio analysis of ESEEM was used to determine the number of deuterons which interact with Cu2+ and the distance between deuteron(s) and Cu2+. The bonding site of beta- carotene determined by ESEEM and pulse electron nuclear double resonance is the C15=C15' double bond. PMID:16853353

Gao, Yunlong; Kispert, Lowell D; van Tol, Johan; Brunel, Louis-Claude

2005-10-01

393

Characterization of V2O5-AlPO4 catalysts by 51V and 1H magic-angle spinning solid-state nuclear magnetic resonance spectroscopy.  

PubMed

Amorphous aluminum orthophosphate is used as a carrier for preparing a series of V2O5-AlPO4 catalysts with varying vanadia content. The catalysts were characterized by solid-state 51V and 1H magic-angle spinning nuclear magnetic resonance (MAS NMR), electron spin resonance (ESR) and X-ray diffraction (XRD). The XRD patterns of the catalysts remained amorphous at all loadings studied. 51V Solid-state NMR spectra revealed the presence of V2O5 microcrystallites at higher vanadia loadings. The 1H MAS NMR spectra of the catalysts showed a maximum consumption of support hydroxyl groups at 6 wt.-% V2O5 indicating the completion of a monolayer at this composition. PMID:7894983

Lakshmi, L J; Srinivas, S T; Rao, P K; Nosov, A V; Lapina, O B; Mastikhin, V M

1995-01-01

394

Magnetic decoupling of 129Xe nuclear spin relaxation due to wall collisions with RbH and RbD coatings  

NASA Astrophysics Data System (ADS)

Data are presented on the wall-induced nuclear spin-relaxation rate of 129Xe in glass cells in which the interior walls are coated with either rubidium hydride (RbH) or rubidium deuteride (RbD). The relaxation rates have been measured as a function of both magnetic field (0.08Spin relaxation was observed to decrease significantly with increasing magnetic field in both RbH- and RbD-coated cells at all temperatures studied. At temperatures above roughly 250 K, there is strong evidence that relaxation is due to long-range dipolar interactions with paramagnetic sites.

Rohrbaugh, Scott; Wang, H. T. J.; Singh, J.; Tobias, W. A.; Cates, G. D.

2012-10-01

395

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...

396

Nuclear spin temperature of ammonia in Comet 9P/Tempel 1 before and after the Deep Impact event  

NASA Astrophysics Data System (ADS)

The Deep Impact mission succeeded in excavating inner materials from the nucleus of Comet 9P/Tempel 1 on 2005 July 04 (at 05:52 UT). Comet 9P/Tempel 1 is one of Jupiter family short period comets, which might originate in the Kuiper belt region in the solar nebula. In order to characterize the comet and to support the mission from the ground-based observatory, optical high-dispersion spectroscopic observations were carried out with the echelle spectrograph (UVES) mounted on the 8-m telescope VLT (UT2) before and after the Deep Impact event. Ortho-to- para abundance ratios (OPRs) of cometary ammonia were determined from the NH 2 emission spectra. The OPRs of ammonia on July 3.996 UT and 4.997 UT were derived to be 1.28±0.07 (nuclear spin temperature: T=24±2 K) and 1.26±0.08 ( T=25±2 K), respectively. There is no significant change between before and after the impact. Actually, most materials ejected from the impact site could have moved away from the nucleus on July 4.997 UT, about 17 h after the impact. However, a small fraction of the ejected materials might remain in the slit of UVES instrument at that time because an excess of about 20% in the NH 2 emission flux is observed above the normal activity level was found [Manfroid, J., Hutsemékers, D., Jehin, E., Cochran, A.L., Arpigny, C., Jackson, W.M., Meech, K.J., Schulz, R., Zucconi, J.-M., 2007. Icarus. This issue]. If the excess of NH 2 on July 04.997 UT was produced from icy materials excavated by the Deep Impact, then an upper-limit of the ammonia OPR would be 1.75 ( T>17 K) for those materials. On the other hand, the OPR of ammonia produced from the quiescent sources was similar to that of the Oort cloud comets observed so far. This fact may imply that physical conditions where cometary ices formed were similar between Comet 9P/Tempel 1 and the Oort cloud comets.

Kawakita, Hideyo; Jehin, Emmanuel; Manfroid, Jean; Hutsemékers, Damien

2007-03-01

397

Nuclear spin temperature of ammonia in Comet 9P/Tempel 1 before and after the Deep Impact event  

NASA Astrophysics Data System (ADS)

The Deep Impact mission succeeded in excavating inner materials from the nucleus of Comet 9P/Tempel 1 on 2005 July 04 (at 05:52 UT). Comet 9P/Tempel 1 is one of Jupiter family short period comets, which might originate in the Kuiper belt region in the solar nebula. In order to characterize the comet and to support the mission from the ground-based observatory, optical high-dispersion spectroscopic observations were carried out with the echelle spectrograph (UVES) mounted on the 8-m telescope VLT (UT2) before and after the Deep Impact event. Ortho-to-para abundance ratios (OPRs) of cometary ammonia were determined from the NH2 emission spectra. The OPRs of ammonia on July 3.996 UT and 4.997 UT were derived to be 1.28±0.07 (nuclear spin temperature: T=24±2 K) and 1.26±0.08 (T=25±2 K), respectively. There is no significant change between before and after the impact. Actually, most materials ejected from the impact site could have moved away from the nucleus on July 4.997 UT, about 17 h after the impact. However, a small fraction of the ejected materials might remain in the slit of UVES instrument at that time because an excess of about 20% in the NH2 emission flux is observed above the normal activity level was found [Manfroid, J., Hutsemékers, D., Jehin, E., Cochran, A.L., Arpigny, C., Jackson, W.M., Meech, K.J., Schulz, R., Zucconi, J.-M., 2007. Icarus. This issue]. If the excess of NH2 on July 04.997 UT was produced from icy materials excavated by the Deep Impact, then an upper-limit of the ammonia OPR would be 1.75 (T>17 K) for those materials. On the other hand, the OPR of ammonia produced from the quiescent sources was similar to that of the Oort cloud comets observed so far. This fact may imply that physical conditions where cometary ices formed were similar between Comet 9P/Tempel 1 and the Oort cloud comets.

Kawakita, Hideyo; Jehin, Emmanuel; Manfroid, Jean; Hutsemékers, Damien

398

Enantiodiscrimination and extraction of short and long range homo- and hetero-nuclear residual dipolar couplings by a spin selective correlation experiment  

NASA Astrophysics Data System (ADS)

A two dimensional correlation experiment for the measurement of short and long range homo- and hetero- nuclear residual dipolar couplings (RDCs) from the broad and featureless proton NMR spectra including 13C satellites is proposed. The method employs a single natural abundant 13C spin as a spy nucleus to probe all the coupled protons and permits the determination of RDCs of negligible strengths. The technique has been demonstrated for the study of organic chiral molecules aligned in chiral liquid crystal, where additional challenge is to unravel the overlapped spectrum of enantiomers. The significant advantage of the method is demonstrated in better chiral discrimination using homonuclear RDCs as additional parameters.

Nath, Nilamoni; Suryaprakash, N.

2010-08-01

399

Near-surface structural phase transition of SrTiO3 studied with zero-field beta-detected nuclear spin relaxation and resonance.  

PubMed

We demonstrate that zero-field beta-detected nuclear quadrupole resonance and spin relaxation of low energy (8)Li can be used as a sensitive local probe of structural phase transitions near a surface. We find that the transition near the surface of a SrTiO(3) single crystal occurs at T(c) approximately 150K, i.e., approximately 45K higher than T(c)bulk, and that the tetragonal domains formed below T(c) are randomly oriented. PMID:16712119

Salman, Z; Kiefl, R F; Chow, K H; Hossain, M D; Keeler, T A; Kreitzman, S R; Levy, C D P; Miller, R I; Parolin, T J; Pearson, M R; Saadaoui, H; Schultz, J D; Smadella, M; Wang, D; MacFarlane, W A

2006-04-14

400

Nuclear magnetic resonance data of C17H14N2O3  

NASA Astrophysics Data System (ADS)

This document is part of Part 1 `Aliphatic 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'.

Kalinowski, H.-O.; Kumar, M.; Gupta, V.; Gupta, R.

401

Nuclear magnetic resonance data of C10H16O4  

NASA Astrophysics Data System (ADS)

This document is part of Part 1 `Aliphatic 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'.

Kalinowski, H.-O.; Kumar, M.; Gupta, V.; Gupta, R.

402

Nuclear magnetic resonance data of C34H46Se2Si4  

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.

403

Nuclear magnetic resonance data of C33H39N6PSe3  

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.

404

Nuclear magnetic resonance data of C33H86S3Si13  

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.

405

Nuclear magnetic resonance data of C32H25N2S3Sb  

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.

406

Nuclear magnetic resonance data of C36H108Se4Si17  

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.

407

Nuclear magnetic resonance data of C30H64S2Si9  

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.

408

Nuclear magnetic resonance data of C36H23F15Te  

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.

409

Nuclear magnetic resonance data of C28H84Se3Si13  

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.

410

Nuclear magnetic resonance data of C30H64Si9Te2  

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.

411

Nuclear magnetic resonance data of C33H39N6PS3  

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.

412

Nuclear magnetic resonance data of C28H48As2N2  

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.

413

Nuclear magnetic resonance data of C27H81SbSi12Te3  

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.

414

Nuclear magnetic resonance data of C36H30S3Si3  

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.

415

Nuclear magnetic resonance data of C28H84Si13Te3  

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.

416

Nuclear magnetic resonance data of C36H30Se3Si3  

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.

417

Nuclear magnetic resonance data of C42H35As2O2Sb  

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.

418

Nuclear magnetic resonance data of C36H30Cl2OSb2  

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.

419

Nuclear magnetic resonance data of C36H108S4Si17  

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.

420

Nuclear magnetic resonance data of C28H60B4N4P2  

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.

421

Nuclear magnetic resonance data of C34H29O6Sb  

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.

422