Nuclear spin circular dichroism
Vaara, Juha; Rizzo, Antonio; Kauczor, Joanna; Norman, Patrick; Coriani, Sonia
2014-04-07
Recent years have witnessed a growing interest in magneto-optic spectroscopy techniques that use nuclear magnetization as the source of the magnetic field. Here we present a formulation of magnetic circular dichroism (CD) due to magnetically polarized nuclei, nuclear spin-induced CD (NSCD), in molecules. The NSCD ellipticity and nuclear spin-induced optical rotation (NSOR) angle correspond to the real and imaginary parts, respectively, of (complex) quadratic response functions involving the dynamic second-order interaction of the electron system with the linearly polarized light beam, as well as the static magnetic hyperfine interaction. Using the complex polarization propagator framework, NSCD and NSOR signals are obtained at frequencies in the vicinity of optical excitations. Hartree-Fock and density-functional theory calculations on relatively small model systems, ethene, benzene, and 1,4-benzoquinone, demonstrate the feasibility of the method for obtaining relatively strong nuclear spin-induced ellipticity and optical rotation signals. Comparison of the proton and carbon-13 signals of ethanol reveals that these resonant phenomena facilitate chemical resolution between non-equivalent nuclei in magneto-optic spectra.
Measurements of nuclear spin dynamics by spin-noise spectroscopy
Ryzhov, I. I.; Poltavtsev, S. V.; Kozlov, G. G.; Zapasskii, V. S.; Kavokin, K. V.; Glazov, M. M.; Vladimirova, M.; Scalbert, D.; Cronenberger, S.; Lemaître, A.; Bloch, J.
2015-06-15
We exploit the potential of the spin noise spectroscopy (SNS) for studies of nuclear spin dynamics in n-GaAs. The SNS experiments were performed on bulk n-type GaAs layers embedded into a high-finesse microcavity at negative detuning. In our experiments, nuclear spin polarisation initially prepared by optical pumping is monitored in real time via a shift of the peak position in the electron spin noise spectrum. We demonstrate that this shift is a direct measure of the Overhauser field acting on the electron spin. The dynamics of nuclear spin is shown to be strongly dependent on the electron concentration.
Nuclear spin polarization following intermediate-energy heavy-ion reactions
Groh, D. E.; Pinter, J. S.; Mantica, P. F.; Mertzimekis, T. J.; Stuchbery, A. E.; Khoa, D. T.
2007-11-15
Intermediate-energy heavy-ion collisions can produce a spin polarization of the projectile-like species. Spin polarization has been observed for both nucleon removal and nucleon pickup processes. Qualitative agreement with measured spin polarization as a function of the momentum of the projectile-like fragment is found in a kinematic model that considers conservation of linear and angular momentum and assumes peripheral interactions between the fast projectile and target. Better quantitative agreement was reached by including more realistic angular distributions and deorientation caused by {gamma}-ray emission and by correcting for the out-of-plane acceptance. The newly introduced corrections were found to apply to both nucleon removal and nucleon pickup processes.
Electron spin decoherence in nuclear spin baths and dynamical decoupling
Zhao, N.; Yang, W.; Ho, S. W.; Hu, J. L.; Wan, J. T. K.; Liu, R. B.
2011-12-23
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.
High-spin nuclear spectroscopy
Diamond, R.M.
1986-07-01
High-spin spectroscopy is the study of the changes in nuclear structure, properties, and behavior with increasing angular momentum. It involves the complex interplay between collective and single-particle motion, between shape and deformation changes, particle alignments, and changes in the pairing correlations. A review of progress in theory, experimentation, and instrumentation in this field is given. (DWL)
Electron spin decoherence in silicon carbide nuclear spin bath
NASA Astrophysics Data System (ADS)
Yang, Li-Ping
In this paper, we study the electron spin decoherence of single defects in silicon carbide (SiC) nuclear spin bath. We find that, although the natural abundance of 29Si (4.7 counter-intuitive result, is the suppression of heteronuclear-spin flip-flop process in finite magnetic field. Our results show that electron spin of defect centers in SiC are excellent candidates for solid state spin qubit in quantum information processing.
Dressed qubits in nuclear spin baths
Wu Lianao
2010-04-15
We present a method to encode a dressed qubit into the product state of an electron spin localized in a quantum dot and its surrounding nuclear spins via a dressing transformation. In this scheme, the hyperfine coupling and a portion of a nuclear dipole-dipole interaction become logic gates, while they are the sources of decoherence in electron-spin qubit proposals. We discuss errors and corrections for the dressed qubits. Interestingly, the effective Hamiltonian of nuclear spins is equivalent to a pairing Hamiltonian, which provides the microscopic mechanism to protect dressed qubits against decoherence.
Nuclear spin noise in NMR revisited
Ferrand, Guillaume; Luong, Michel
2015-09-07
The theoretical shapes of nuclear spin-noise spectra in NMR are derived by considering a receiver circuit with finite preamplifier input impedance and a transmission line between the preamplifier and the probe. Using this model, it becomes possible to reproduce all observed experimental features: variation of the NMR resonance linewidth as a function of the transmission line phase, nuclear spin-noise signals appearing as a “bump” or as a “dip” superimposed on the average electronic noise level even for a spin system and probe at the same temperature, pure in-phase Lorentzian spin-noise signals exhibiting non-vanishing frequency shifts. Extensive comparisons to experimental measurements validate the model predictions, and define the conditions for obtaining pure in-phase Lorentzian-shape nuclear spin noise with a vanishing frequency shift, in other words, the conditions for simultaneously obtaining the spin-noise and frequency-shift tuning optima.
Nuclear spin noise in NMR revisited
NASA Astrophysics Data System (ADS)
Ferrand, Guillaume; Huber, Gaspard; Luong, Michel; Desvaux, Hervé
2015-09-01
The theoretical shapes of nuclear spin-noise spectra in NMR are derived by considering a receiver circuit with finite preamplifier input impedance and a transmission line between the preamplifier and the probe. Using this model, it becomes possible to reproduce all observed experimental features: variation of the NMR resonance linewidth as a function of the transmission line phase, nuclear spin-noise signals appearing as a "bump" or as a "dip" superimposed on the average electronic noise level even for a spin system and probe at the same temperature, pure in-phase Lorentzian spin-noise signals exhibiting non-vanishing frequency shifts. Extensive comparisons to experimental measurements validate the model predictions, and define the conditions for obtaining pure in-phase Lorentzian-shape nuclear spin noise with a vanishing frequency shift, in other words, the conditions for simultaneously obtaining the spin-noise and frequency-shift tuning optima.
Detection and Control of Individual Nuclear Spins Using a Weakly Coupled Electron Spin
Taminiau, T.H.; Wagenaar, J.J.T.; van der Sar, T.; Jelezko, F.; Dobrovitski, Viatcheslav V.; Hanson, R.
2012-09-28
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.
The spin-temperature theory of dynamic nuclear polarization and nuclear spin-lattice relaxation
NASA Technical Reports Server (NTRS)
Byvik, C. E.; Wollan, D. S.
1974-01-01
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.
Nuclear spin relaxation of polycrystalline 129 xenon
NASA Astrophysics Data System (ADS)
Samuelson, Gary Lee, Jr.
Through spin exchange optical pumping, it is possible to achieve upwards of 30% nuclear spin polarization in 129Xe with an NMR signal enhancement of some 5 orders of magnitude over typical thermal signals. Hyperpolarized 129Xe has thus found application in several leading-edge technologies. At 1 T and 4.2 K, the characteristic relaxation time of enriched polycrystalline 129Xe (86% 129Xe, 0.1% 131Xe) is well over 200 hrs, sufficient for long-term storage and transport. Longitudinal nuclear spin relaxation of 129Xe at more convenient fields from 1 to 200 G is studied in detail. Significant structure in relaxation times vs. magnetic field is seen; the most prominent new finding being a sharp local long-time T 1 maximum of 1000 mins at ≈3 G. Such structure has not been observed in previous measurements of natural Xe. Below temperatures of 10 K, relaxation can be attributed to cross relaxation with 131Xe, mediated by spin diffusion. Measurements of 129Xe relaxation as a function of magnetic field, temperature and Xe isotopic content are reported and compared with expected theoretical behaviors. It is seen that the characteristic nuclear spin relaxation of enriched 129Xe at 4.2 K is nonexponential at these low fields. For fields between 10 G and 200 G, these nonexponential relaxation curves can be fit well with a specific spin diffusion model. Below 10 G no such fit is possible and thus quantum mechanical details of the coupling between 129Xe, 131Xe and the bulk lattice are considered. These findings support the hypothesis that cross relaxation with 131Xe is indeed a dominant actor in the nuclear spin relaxation of polycrystalline 129 Xe at such low fields and low temperatures.
Nuclear moment of inertia and spin distribution of nuclear levels
Alhassid, Y.; Fang, L.; Liu, S.; Bertsch, G.F.
2005-12-15
We introduce a simple model to calculate the nuclear moment of inertia at finite temperature. This moment of inertia describes the spin distribution of nuclear levels in the framework of the spin-cutoff model. Our model is based on a deformed single-particle Hamiltonian with pairing interaction and takes into account fluctuations in the pairing gap. We derive a formula for the moment of inertia at finite temperature that generalizes the Belyaev formula for zero temperature. We show that a number-parity projection explains the strong odd-even effects observed in shell model Monte Carlo studies of the nuclear moment of inertia in the iron region.
Nuclear spin effects in optical lattice clocks
Boyd, Martin M.; Zelevinsky, Tanya; Ludlow, Andrew D.; Blatt, Sebastian; Zanon-Willette, Thomas; Foreman, Seth M.; Ye Jun
2007-08-15
We present a detailed experimental and theoretical study of the effect of nuclear spin on the performance of optical lattice clocks. With a state-mixing theory including spin-orbit and hyperfine interactions, we describe the origin of the {sup 1}S{sub 0}-{sup 3}P{sub 0} clock transition and the differential g factor between the two clock states for alkaline-earth-metal(-like) atoms, using {sup 87}Sr as an example. Clock frequency shifts due to magnetic and optical fields are discussed with an emphasis on those relating to nuclear structure. An experimental determination of the differential g factor in {sup 87}Sr is performed and is in good agreement with theory. The magnitude of the tensor light shift on the clock states is also explored experimentally. State specific measurements with controlled nuclear spin polarization are discussed as a method to reduce the nuclear spin-related systematic effects to below 10{sup -17} in lattice clocks.
Feedback control of nuclear spin bath for a single hole spin in a quantum dot
NASA Astrophysics Data System (ADS)
Pang, Hongliang; Gong, Zhirui; Yao, Wang
2014-03-01
In a semiconductor quantum dot, the nuclear spin bath plays an important role as the ultimate environment of an electron or hole spin at low temperature. Through dynamic nuclear spin polarization driven by an oscillating electric field, we show that feedback controls can be implemented on the nuclear spin bath of a single hole spin. The feedback controls utilize the anisotropic hyperfine interaction between the hole spin and the nuclear spins. The negative feedback can suppress the statistical fluctuations of the nuclear hyperfine field and lead to longer coherence time of the hole spin. Positive feedback can possibly lead to cat like state of nuclear spin bath. The efficiency of the controls schemes is investigated under different parameters and control strategies. The work is supported by the Croucher Foundation under the Croucher Innovation Award, and the Research Grant Council of Hong Kong (HKU706309P, HKU8/CRF/11G).
Control of electron spin decoherence caused by electron nuclear spin dynamics in a quantum dot
NASA Astrophysics Data System (ADS)
Liu, Ren-Bao; Yao, Wang; Sham, L. J.
2007-07-01
Control of electron spin decoherence in contact with a mesoscopic bath of many interacting nuclear spins in an InAs quantum dot is studied by solving the coupled quantum dynamics. The nuclear spin bath, because of its bifurcated evolution predicated on the electron spin up or down state, measures the which-state information of the electron spin and hence diminishes its coherence. The many-body dynamics of the nuclear spin bath is solved with a pair-correlation approximation. In the relevant timescale, nuclear pair-wise flip flops, as elementary excitations in the mesoscopic bath, can be mapped into the precession of non-interacting pseudo-spins. Such mapping provides a geometrical picture for understanding the decoherence and for devising control schemes. A close examination of nuclear bath dynamics reveals a wealth of phenomena and new possibilities of controlling the electron spin decoherence. For example, when the electron spin is flipped by a π-pulse at τ, its coherence will partially recover at \\sqrt{2}\\tau as a consequence of quantum disentanglement from the mesoscopic bath. In contrast to the re-focusing of inhomogeneously broadened phases by conventional spin-echoes, the disentanglement is realized through shepherding quantum evolution of the bath state via control of the quantum object. A concatenated construction of pulse sequences can eliminate the decoherence with arbitrary accuracy, with the nuclear nuclear spin interaction strength acting as the controlling small parameter.
Atomic-scale magnetometry of distant nuclear spin clusters via nitrogen-vacancy spin in diamond.
Zhao, Nan; Hu, Jian-Liang; Ho, Sai-Wah; Wan, Jones T K; Liu, R B
2011-04-01
The detection of single nuclear spins is an important goal in magnetic resonance spectroscopy. Optically detected magnetic resonance can detect single nuclear spins that are strongly coupled to an electron spin, but the detection of distant nuclear spins that are only weakly coupled to the electron spin has not been considered feasible. Here, using the nitrogen-vacancy centre in diamond as a model system, we numerically demonstrate that it is possible to detect two or more distant nuclear spins that are weakly coupled to a centre electron spin if these nuclear spins are strongly bonded to each other in a cluster. This cluster will stand out from other nuclear spins by virtue of characteristic oscillations imprinted onto the electron spin decoherence profile, which become pronounced under dynamical decoupling control. Under many-pulse dynamical decoupling, the centre electron spin coherence can be used to measure nuclear magnetic resonances of single molecules. This atomic-scale magnetometry should improve the performance of magnetic resonance spectroscopy for applications in chemical, biological, medical and materials research, and could also have applications in solid-state quantum computing. PMID:21358646
Nuclear spin polarized H and D by means of spin-exchange optical pumping
NASA Astrophysics Data System (ADS)
Stenger, Jörn; Grosshauser, Carsten; Kilian, Wolfgang; Nagengast, Wolfgang; Ranzenberger, Bernd; Rith, Klaus; Schmidt, Frank
1998-01-01
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=PSṡPI, 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.
Feedback control of nuclear spin bath of a single hole spin in a quantum dot
NASA Astrophysics Data System (ADS)
Pang, Hongliang; Gong, Zhirui; Yao, Wang
2015-01-01
For a III-V semiconductor quantum dot charged with a single hole, we investigate the feedback control of the nuclear spin bath through dynamical nuclear spin polarization. The scheme utilizes the hole-nuclear flip-flop by their anisotropic hyperfine interaction, where the flip direction of the nuclear spin can be conditioned on the sign of the overall hyperfine field through initialization processes that do not involve explicit measurement. We show that a negative feedback can be implemented to suppress the statistical fluctuations of the nuclear hyperfine field for enhancing the coherence time of the hole spin qubit. Positive feedback can prepare the nuclear spin ensemble into states where the nuclear hyperfine field distribution has two well separated peaks, realizing a quantum heat bath that cannot be described by a single effective temperature.
Park, Kisam; Light, John C
2007-12-14
The spin-modification probability (SMP) method, which provides fundamental and detailed quantitative information on the nuclear spin selection rules, is discussed more systematically and generalized for reactive collision systems involving more than one configuration of reactant and product molecules, explicitly taking account of the conservation of the overall nuclear spin symmetry as well as the conservation of the total nuclear spin angular momentum, under the assumption of no nuclear hyperfine interaction. The values of SMP once calculated can be used for any system of identical nuclei of any spin as long as the system has the corresponding nuclear spin symmetry. The values of SMP calculated for simple systems can also be used for more complex systems containing several kinds of identical nuclei or various isotopomers. The generalized formulation of statistical scattering theory which can easily represent various rearrangement mechanisms is also presented. PMID:18081384
NASA Technical Reports Server (NTRS)
Lee, Seungwon; vonAllmen, Paul; Oyafuso, Fabiano; Klimeck, Gerhard; Whale, K. Birgitta
2004-01-01
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.
Nuclear magnetometry studies of spin dynamics in quantum Hall systems
NASA Astrophysics Data System (ADS)
Fauzi, M. H.; Watanabe, S.; Hirayama, Y.
2014-12-01
We performed a nuclear magnetometry study on quantum Hall ferromagnet with a bilayer total filling factor of νtot=2 . We found not only a rapid nuclear relaxation but also a sudden change in the nuclear-spin polarization distribution after a one-second interaction with a canted antiferromagnetic phase. We discuss the possibility of observing cooperative phenomena coming from nuclear-spin ensemble triggered by hyperfine interaction in quantum Hall system.
Spin Modes in Nuclei and Nuclear Forces
Suzuki, Toshio; Otsuka, Takaharu
2011-05-06
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.
Spin Modes in Nuclei and Nuclear Forces
NASA Astrophysics Data System (ADS)
Suzuki, Toshio; Otsuka, Takaharu
2011-05-01
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 12C and 14C and an anomalous M1 transition in 17C. 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 Δ 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.
Optically induced dynamic nuclear spin polarisation in diamond
NASA Astrophysics Data System (ADS)
Scheuer, Jochen; Schwartz, Ilai; Chen, Qiong; Schulze-Sünninghausen, David; Carl, Patrick; Höfer, Peter; Retzker, Alexander; Sumiya, Hitoshi; Isoya, Junichi; Luy, Burkhard; Plenio, Martin B.; Naydenov, Boris; Jelezko, Fedor
2016-01-01
The sensitivity of magnetic resonance imaging (MRI) depends strongly on nuclear spin polarisation and, motivated by this observation, dynamical nuclear spin polarisation has recently been applied to enhance MRI protocols (Kurhanewicz et al 2011 Neoplasia 13 81). Nuclear spins associated with the 13C carbon isotope (nuclear spin I = 1/2) in diamond possess uniquely long spin lattice relaxation times (Reynhardt and High 2011 Prog. Nucl. Magn. Reson. Spectrosc. 38 37). If they are present in diamond nanocrystals, especially when strongly polarised, they form a promising contrast agent for MRI. Current schemes for achieving nuclear polarisation, however, require cryogenic temperatures. Here we demonstrate an efficient scheme that realises optically induced 13C nuclear spin hyperpolarisation in diamond at room temperature and low ambient magnetic field. Optical pumping of a nitrogen-vacancy centre creates a continuously renewable electron spin polarisation which can be transferred to surrounding 13C nuclear spins. Importantly for future applications we also realise polarisation protocols that are robust against an unknown misalignment between magnetic field and crystal axis.
Room temperature hyperpolarization of nuclear spins in bulk
Tateishi, Kenichiro; Negoro, Makoto; Nishida, Shinsuke; Kagawa, Akinori; Morita, Yasushi; Kitagawa, Masahiro
2014-01-01
Dynamic nuclear polarization (DNP), a means of transferring spin polarization from electrons to nuclei, can enhance the nuclear spin polarization (hence the NMR sensitivity) in bulk materials at most 660 times for 1H spins, using electron spins in thermal equilibrium as polarizing agents. By using electron spins in photo-excited triplet states instead, DNP can overcome the above limit. We demonstrate a 1H spin polarization of 34%, which gives an enhancement factor of 250,000 in 0.40 T, while maintaining a bulk sample (∼0.6 mg, ∼0.7 × 0.7 × 1 mm3) containing >1019 1H spins at room temperature. Room temperature hyperpolarization achieved with DNP using photo-excited triplet electrons has potentials to be applied to a wide range of fields, including NMR spectroscopy and MRI as well as fundamental physics. PMID:24821773
Optical manipulation of a multilevel nuclear spin in ZnO: Master equation and experiment
NASA Astrophysics Data System (ADS)
Buß, J. H.; Rudolph, J.; Wassner, T. A.; Eickhoff, M.; Hägele, D.
2016-04-01
We demonstrate the dynamics and optical control of a large quantum mechanical solid state spin system consisting of a donor electron spin strongly coupled to the 9/2 nuclear spin of 115In in the semiconductor ZnO. Comparison of electron spin dynamics observed by time-resolved pump-probe spectroscopy with density matrix theory reveals nuclear spin pumping via optically oriented electron spins, coherent spin-spin interaction, and quantization effects of the ten nuclear spin levels. Modulation of the optical electron spin orientation at frequencies above 1 MHz gives evidence for fast optical manipulation of the nuclear spin state.
Enhancement of electron spin coherence by optical preparation of nuclear spins.
Stepanenko, Dimitrije; Burkard, Guido; Giedke, Geza; Imamoglu, Atac
2006-04-01
We study a large ensemble of nuclear spins interacting with a single electron spin in a quantum dot under optical excitation and photon detection. At the two-photon resonance between the two electron-spin states, the detection of light scattering from the intermediate exciton state acts as a weak quantum measurement of the effective magnetic (Overhauser) field due to the nuclear spins. In a coherent population trapping state without light scattering, the nuclear state is projected into an eigenstate of the Overhauser field operator, and electron decoherence due to nuclear spins is suppressed: We show that this limit can be approached by adapting the driving frequencies when a photon is detected. We use a Lindblad equation to describe the driven system under photon emission and detection. Numerically, we find an increase of the electron coherence time from 5 to 500 ns after a preparation time of 10 micros. PMID:16712008
Long-lived nuclear spin states far from magnetic equivalence.
Stevanato, Gabriele; Roy, Soumya Singha; Hill-Cousins, Joe; Kuprov, Ilya; Brown, Lynda J; Brown, Richard C D; Pileio, Giuseppe; Levitt, Malcolm H
2015-02-28
Clusters of coupled nuclear spins may form long-lived nuclear spin states, which interact weakly with the environment, compared to ordinary nuclear magnetization. All experimental demonstrations of long-lived states have so far involved spin systems which are close to the condition of magnetic equivalence, in which the network of spin-spin couplings is conserved under all pair exchanges of symmetry-related nuclei. We show that the four-spin system of trans-[2,3-(13)C2]-but-2-enedioate exhibits a long-lived nuclear spin state, even though this spin system is very far from magnetic equivalence. The 4-spin long-lived state is accessed by slightly asymmetric chemical substitutions of the centrosymmetric molecular core. The long-lived state is a consequence of the locally centrosymmetric molecular geometry for the trans isomer, and is absent for the cis isomer. A general group theoretical description of long-lived states is presented. It is shown that the symmetries of coherent and incoherent interactions are both important for the existence of long-lived states. PMID:25633837
Anisotropic nuclear-spin diffusion in double quantum wells
NASA Astrophysics Data System (ADS)
Hatano, T.; Kume, W.; Watanabe, S.; Akiba, K.; Nagase, K.; Hirayama, Y.
2015-03-01
Nuclear spin diffusion in double quantum wells (QWs) is examined by using dynamic nuclear polarization (DNP) at a Landau level filling factor ν =2 /3 spin phase transition (SPT). The longitudinal resistance increases during the DNP of one of the two QW (the "polarization QW") by means of a large applied current and starts to decrease just after the termination of the DNP. On the other hand, the longitudinal resistance of the other QW (the "detection QW") continuously increases for approximately 2 h after the termination of the DNP of the polarization QW. It is therefore concluded that the nuclear spins diffuse from the polarization QW to the detection QW. The time evolution of the longitudinal resistance of the polarization QW is explained mainly by the nuclear spin diffusion in the in-plane direction. In contrast, that of the detection QW manifests much slower nuclear diffusion in the perpendicular direction through the AlGaAs barrier.
Decoupling a hole spin qubit from the nuclear spins.
Prechtel, Jonathan H; Kuhlmann, Andreas V; Houel, Julien; Ludwig, Arne; Valentin, Sascha R; Wieck, Andreas D; Warburton, Richard J
2016-09-01
A huge effort is underway to develop semiconductor nanostructures as low-noise hosts for qubits. The main source of dephasing of an electron spin qubit in a GaAs-based system is the nuclear spin bath. A hole spin may circumvent the nuclear spin noise. In principle, the nuclear spins can be switched off for a pure heavy-hole spin. In practice, it is unknown to what extent this ideal limit can be achieved. A major hindrance is that p-type devices are often far too noisy. We investigate here a single hole spin in an InGaAs quantum dot embedded in a new generation of low-noise p-type device. We measure the hole Zeeman energy in a transverse magnetic field with 10 neV resolution by dark-state spectroscopy as we create a large transverse nuclear spin polarization. The hole hyperfine interaction is highly anisotropic: the transverse coupling is <1% of the longitudinal coupling. For unpolarized, randomly fluctuating nuclei, the ideal heavy-hole limit is achieved down to nanoelectronvolt energies; equivalently dephasing times up to a microsecond. The combination of large and strong optical dipole makes the single hole spin in a GaAs-based device an attractive quantum platform. PMID:27454044
Quantum dot spin coherence governed by a strained nuclear environment.
Stockill, R; Le Gall, C; Matthiesen, C; Huthmacher, L; Clarke, E; Hugues, M; Atatüre, M
2016-01-01
The interaction between a confined electron and the nuclei of an optically active quantum dot provides a uniquely rich manifestation of the central spin problem. Coherent qubit control combines with an ultrafast spin-photon interface to make these confined spins attractive candidates for quantum optical networks. Reaching the full potential of spin coherence has been hindered by the lack of knowledge of the key irreversible environment dynamics. Through all-optical Hahn echo decoupling we now recover the intrinsic coherence time set by the interaction with the inhomogeneously strained nuclear bath. The high-frequency nuclear dynamics are directly imprinted on the electron spin coherence, resulting in a dramatic jump of coherence times from few tens of nanoseconds to the microsecond regime between 2 and 3 T magnetic field and an exponential decay of coherence at high fields. These results reveal spin coherence can be improved by applying large magnetic fields and reducing strain inhomogeneity. PMID:27615704
Single-shot readout of a single nuclear spin.
Neumann, Philipp; Beck, Johannes; Steiner, Matthias; Rempp, Florian; Fedder, Helmut; Hemmer, Philip R; Wrachtrup, Jörg; Jelezko, Fedor
2010-07-30
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
Nuclear Spin Conversion in CH4: A Multichannel Relaxation Mechanism.
Cacciani, Patrice; Cosléou, Jean; Khelkhal, Mohamed; Čermák, Peter; Puzzarini, Cristina
2016-01-21
Experiments on nuclear spin interconversion of ortho, para, and meta nuclear spin isomers of the methane molecule have been undertaken in gas phase and cryomatrices. Only the latter environment has led to the observation of the nuclear spin conversion. In this study, a quantitative explanation is given for the first time by considering the coupling of three relaxation paths: meta ⇔ para, meta ⇔ ortho, and ortho ⇔ para. The global evolution of the three populations of spin isomers is thus described by two characteristic times, which have been calculated using the best values of the energy levels for the vibrational ground state, of the intramolecular magnetic interactions, and of the collisional relaxation rates, and for different pressure and temperature conditions. Such calculations also provide an indication for the proper choice of reliable scenarios for experimental separation of the spin isomers of methane. PMID:26681482
Hu, Huping; Wu, Maoxin
2004-01-01
A novel theory of consciousness is proposed in this paper. We postulate that consciousness is intrinsically connected to quantum spin since the latter is the origin of quantum effects in both Bohm and Hestenes quantum formulism and a fundamental quantum process associated with the structure of space-time. That is, spin is the "mind-pixel". The unity of mind is achieved by entanglement of the mind-pixels. Applying these ideas to the particular structures and dynamics of the brain, we theorize that human brain works as follows: through action potential modulated nuclear spin interactions and paramagnetic O2/NO driven activations, the nuclear spins inside neural membranes and proteins form various entangled quantum states some of which survive decoherence through quantum Zeno effects or in decoherence-free subspaces and then collapse contextually via irreversible and non-computable means producing consciousness and, in turn, the collective spin dynamics associated with said collapses have effects through spin chemistry on classical neural activities thus influencing the neural networks of the brain. Our proposal calls for extension of associative encoding of neural memories to the dynamical structures of neural membranes and proteins. Thus, according our theory, the nuclear spin ensembles are the "mind-screen" with nuclear spins as its pixels, the neural membranes and proteins are the mind-screen and memory matrices, and the biologically available paramagnetic species such as O2 and NO are pixel-activating agents. Together, they form the neural substrates of consciousness. We also present supporting evidence and make important predictions. We stress that our theory is experimentally verifiable with present technologies. Further, experimental realizations of intra-/inter-molecular nuclear spin coherence and entanglement, macroscopic entanglement of spin ensembles and NMR quantum computation, all in room temperatures, strongly suggest the possibility of a spin
Polarization of nuclear spins by a cold nanoscale resonator
Butler, Mark C.; Weitekamp, Daniel P.
2011-12-15
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
Nuclear magnetic resonance spectroscopy with single spin sensitivity
Müller, C.; Kong, X.; Cai, J.-M.; Melentijević, K.; Stacey, A.; Markham, M.; Twitchen, D.; Isoya, J.; Pezzagna, S.; Meijer, J.; Du, J. F.; Plenio, M. B.; Naydenov, B.; McGuinness, L. P.; Jelezko, F.
2014-01-01
Nuclear magnetic resonance spectroscopy and magnetic resonance imaging at the ultimate sensitivity limit of single molecules or single nuclear spins requires fundamentally new detection strategies. The strong coupling regime, when interaction between sensor and sample spins dominates all other interactions, is one such strategy. In this regime, classically forbidden detection of completely unpolarized nuclei is allowed, going beyond statistical fluctuations in magnetization. Here we realize strong coupling between an atomic (nitrogen–vacancy) sensor and sample nuclei to perform nuclear magnetic resonance on four 29Si spins. We exploit the field gradient created by the diamond atomic sensor, in concert with compressed sensing, to realize imaging protocols, enabling individual nuclei to be located with Angstrom precision. The achieved signal-to-noise ratio under ambient conditions allows single nuclear spin sensitivity to be achieved within seconds. PMID:25146503
Nuclear magnetic resonance spectroscopy with single spin sensitivity.
Müller, C; Kong, X; Cai, J-M; Melentijević, K; Stacey, A; Markham, M; Twitchen, D; Isoya, J; Pezzagna, S; Meijer, J; Du, J F; Plenio, M B; Naydenov, B; McGuinness, L P; Jelezko, F
2014-01-01
Nuclear magnetic resonance spectroscopy and magnetic resonance imaging at the ultimate sensitivity limit of single molecules or single nuclear spins requires fundamentally new detection strategies. The strong coupling regime, when interaction between sensor and sample spins dominates all other interactions, is one such strategy. In this regime, classically forbidden detection of completely unpolarized nuclei is allowed, going beyond statistical fluctuations in magnetization. Here we realize strong coupling between an atomic (nitrogen-vacancy) sensor and sample nuclei to perform nuclear magnetic resonance on four (29)Si spins. We exploit the field gradient created by the diamond atomic sensor, in concert with compressed sensing, to realize imaging protocols, enabling individual nuclei to be located with Angstrom precision. The achieved signal-to-noise ratio under ambient conditions allows single nuclear spin sensitivity to be achieved within seconds. PMID:25146503
Nuclear moments of inertia at high spins
Deleplanque, M.A.
1983-12-01
Nuclei with highest angular momentum are discussed. The production of high spin states, and the basic ideas associated with high spin physics are reviewed. Recent developments from continuum ..gamma..-ray studies are presented: the measurement of different average moments of inertia gives new information on the interplay between collective and single particle aspects at high spins. Finally, the exciting possibility of resolving the continuum spectra with new detector systems is examined. 8 references.
Robust dynamical decoupling sequences for individual-nuclear-spin addressing
NASA Astrophysics Data System (ADS)
Casanova, J.; Wang, Z.-Y.; Haase, J. F.; Plenio, M. B.
2015-10-01
We propose the use of non-equally-spaced decoupling pulses for high-resolution selective addressing of nuclear spins by a quantum sensor. The analytical model of the basic operating principle is supplemented by detailed numerical studies that demonstrate the high degree of selectivity and the robustness against static and dynamic control-field errors of this scheme. We exemplify our protocol with a nitrogen-vacancy-center-based sensor to demonstrate that it enables the identification of individual nuclear spins that form part of a large spin ensemble.
Highly selective detection of individual nuclear spins with rotary echo on an electron spin probe
Mkhitaryan, V. V.; Jelezko, F.; Dobrovitski, V. V.
2015-10-26
We consider an electronic spin, such as a nitrogen-vacancy center in diamond, weakly coupled to a large number of nuclear spins, and subjected to the Rabi driving with a periodically alternating phase. We show that by switching the driving phase synchronously with the precession of a given nuclear spin, the interaction to this spin is selectively enhanced, while the rest of the bath remains decoupled. The enhancement is of resonant character. The key feature of the suggested scheme is that the width of the resonance is adjustable, and can be greatly decreased by increasing the driving strength. Thus, the resonance can be significantly narrowed, by a factor of 10–100 in comparison with the existing detection methods. Significant improvement in selectivity is explained analytically and confirmed by direct numerical many-spin simulations. As a result, the method can be applied to a wide range of solid-state systems.
Highly selective detection of individual nuclear spins with rotary echo on an electron spin probe
Mkhitaryan, V. V.; Jelezko, F.; Dobrovitski, V. V.
2015-10-26
We consider an electronic spin, such as a nitrogen-vacancy center in diamond, weakly coupled to a large number of nuclear spins, and subjected to the Rabi driving with a periodically alternating phase. We show that by switching the driving phase synchronously with the precession of a given nuclear spin, the interaction to this spin is selectively enhanced, while the rest of the bath remains decoupled. The enhancement is of resonant character. The key feature of the suggested scheme is that the width of the resonance is adjustable, and can be greatly decreased by increasing the driving strength. Thus, the resonancemore » can be significantly narrowed, by a factor of 10–100 in comparison with the existing detection methods. Significant improvement in selectivity is explained analytically and confirmed by direct numerical many-spin simulations. As a result, the method can be applied to a wide range of solid-state systems.« less
Highly selective detection of individual nuclear spins with rotary echo on an electron spin probe
Mkhitaryan, V. V.; Jelezko, F.; Dobrovitski, V. V.
2015-01-01
We consider an electronic spin, such as a nitrogen-vacancy center in diamond, weakly coupled to a large number of nuclear spins, and subjected to the Rabi driving with a periodically alternating phase. We show that by switching the driving phase synchronously with the precession of a given nuclear spin, the interaction to this spin is selectively enhanced, while the rest of the bath remains decoupled. The enhancement is of resonant character. The key feature of the suggested scheme is that the width of the resonance is adjustable, and can be greatly decreased by increasing the driving strength. Thus, the resonance can be significantly narrowed, by a factor of 10–100 in comparison with the existing detection methods. Significant improvement in selectivity is explained analytically and confirmed by direct numerical many-spin simulations. The method can be applied to a wide range of solid-state systems. PMID:26497777
Analysis of the transient response of nuclear spins in GaAs with/without nuclear magnetic resonance
NASA Astrophysics Data System (ADS)
Rasly, Mahmoud; Lin, Zhichao; Yamamoto, Masafumi; Uemura, Tetsuya
2016-05-01
As an alternative to studying the steady-state responses of nuclear spins in solid state systems, working within a transient-state framework can reveal interesting phenomena. The response of nuclear spins in GaAs to a changing magnetic field was analyzed based on the time evolution of nuclear spin temperature. Simulation results well reproduced our experimental results for the transient oblique Hanle signals observed in an all-electrical spin injection device. The analysis showed that the so called dynamic nuclear polarization can be treated as a cooling tool for the nuclear spins: It works as a provider to exchange spin angular momentum between polarized electron spins and nuclear spins through the hyperfine interaction, leading to an increase in the nuclear polarization. In addition, a time-delay of the nuclear spin temperature with a fast sweep of the external magnetic field produces a possible transient state for the nuclear spin polarization. On the other hand, the nuclear magnetic resonance acts as a heating tool for a nuclear spin system. This causes the nuclear spin temperature to jump to infinity: i.e., the average nuclear spins along with the nuclear field vanish at resonant fields of 75As, 69Ga and 71Ga, showing an interesting step-dip structure in the oblique Hanle signals. These analyses provide a quantitative understanding of nuclear spin dynamics in semiconductors for application in future computation processing.
Nuclear-spin observation of noise spectra in semiconductors
NASA Astrophysics Data System (ADS)
Sasaki, Susumu; Yuge, Tatsuro; Nishimori, Masashi; Kawanago, Takashi; Hirayama, Yoshiro
2013-12-01
We propose a systematic method of obtaining the spectra of noises that cause the decoherence of spins in solids. Based on this method, we experimentally show that this method can be applied to nuclear spins in semiconductors. We clarify that the spectral intensity must be derived from the long-time tail of the multiple-echo decay. To obtain higher-frequency noise, the inversion-pulse interval must be as short as possible, which required us to employ the alternating-phase Carr-Purcell sequence instead of the widely used Carr-Purcell Meiboom-Gill. For 75As nuclear spin in variously-doped GaAs, we observed a Lorentzian spectrum, instead of the commonly observed 1/f spectrum. This indicates that the nuclear spins are indeed in a coherently-controlled state.
Calculation of nuclear spin-spin coupling constants using frozen density embedding
Götz, Andreas W.; Autschbach, Jochen; Visscher, Lucas
2014-03-14
We present a method for a subsystem-based calculation of indirect nuclear spin-spin coupling tensors within the framework of current-spin-density-functional theory. Our approach is based on the frozen-density embedding scheme within density-functional theory and extends a previously reported subsystem-based approach for the calculation of nuclear magnetic resonance shielding tensors to magnetic fields which couple not only to orbital but also spin degrees of freedom. This leads to a formulation in which the electron density, the induced paramagnetic current, and the induced spin-magnetization density are calculated separately for the individual subsystems. This is particularly useful for the inclusion of environmental effects in the calculation of nuclear spin-spin coupling constants. Neglecting the induced paramagnetic current and spin-magnetization density in the environment due to the magnetic moments of the coupled nuclei leads to a very efficient method in which the computationally expensive response calculation has to be performed only for the subsystem of interest. We show that this approach leads to very good results for the calculation of solvent-induced shifts of nuclear spin-spin coupling constants in hydrogen-bonded systems. Also for systems with stronger interactions, frozen-density embedding performs remarkably well, given the approximate nature of currently available functionals for the non-additive kinetic energy. As an example we show results for methylmercury halides which exhibit an exceptionally large shift of the one-bond coupling constants between {sup 199}Hg and {sup 13}C upon coordination of dimethylsulfoxide solvent molecules.
Optical hyperpolarization of 13C nuclear spins in nanodiamond ensembles
NASA Astrophysics Data System (ADS)
Chen, Q.; Schwarz, I.; Jelezko, F.; Retzker, A.; Plenio, M. B.
2015-11-01
Dynamical nuclear polarization holds the key for orders of magnitude enhancements of nuclear magnetic resonance signals which, in turn, would enable a wide range of novel applications in biomedical sciences. However, current implementations of DNP require cryogenic temperatures and long times for achieving high polarization. Here we propose and analyze in detail protocols that can achieve rapid hyperpolarization of 13C nuclear spins in randomly oriented ensembles of nanodiamonds at room temperature. Our protocols exploit a combination of optical polarization of electron spins in nitrogen-vacancy centers and the transfer of this polarization to 13C nuclei by means of microwave control to overcome the severe challenges that are posed by the random orientation of the nanodiamonds and their nitrogen-vacancy centers. Specifically, these random orientations result in exceedingly large energy variations of the electron spin levels that render the polarization and coherent control of the nitrogen-vacancy center electron spins as well as the control of their coherent interaction with the surrounding 13C nuclear spins highly inefficient. We address these challenges by a combination of an off-resonant microwave double resonance scheme in conjunction with a realization of the integrated solid effect which, together with adiabatic rotations of external magnetic fields or rotations of nanodiamonds, leads to a protocol that achieves high levels of hyperpolarization of the entire nuclear-spin bath in a randomly oriented ensemble of nanodiamonds even at room temperature. This hyperpolarization together with the long nuclear-spin polarization lifetimes in nanodiamonds and the relatively high density of 13C nuclei has the potential to result in a major signal enhancement in 13C nuclear magnetic resonance imaging and suggests functionalized and hyperpolarized nanodiamonds as a unique probe for molecular imaging both in vitro and in vivo.
Amaha, S.; Hatano, T.; Tarucha, S.; Gupta, J. A.; Austing, D. G.
2015-04-27
We investigate nuclear spin pumping with five-electron quadruplet spin states in a spin-blockaded weakly coupled vertical double quantum dot device. Two types of hysteretic steps in the leakage current are observed on sweeping the magnetic field and are associated with bidirectional polarization of nuclear spin. Properties of the steps are understood in terms of bias-voltage-dependent conditions for the mixing of quadruplet and doublet spin states by the hyperfine interaction. The hysteretic steps vanish when up- and down-nuclear spin pumping processes are in close competition.
Spin constraints on nuclear energy density functionals
NASA Astrophysics Data System (ADS)
Robledo, L. M.; Bernard, R. N.; Bertsch, G. F.
2014-02-01
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.
NASA Astrophysics Data System (ADS)
Flatté, Michael E.
Transport of carriers through disordered electronic energy landscapes occurs via hopping or tunneling through various sites, and can enhance the effects of carrier spin dynamics on the transport. When incoherent hopping preserves the spin orientation of carriers, the magnetic-field-dependent correlations between pairs of spins influence the charge conductivity of the material. Examples of these phenomena have been identified in hopping transport in organic semiconductors and colloidal quantum dots, as well as tunneling through oxide barriers in complex oxide devices, among other materials. The resulting room-temperature magnetic field effects on the conductivity or electroluminescence require external fields of only a few milliTesla. These magnetic field effects can be dramatically modified by changes in the local spin environment. Recent theoretical and experimental work has identified a regime for low-field magnetoresistance in organic semiconductors in which the spin-relaxing effects of localized nuclear spins and electronic spins interfere1. The regime is studied experimentally by the controlled addition of localized electronic spins, through the addition of a stable free radical (galvinoxyl) to a material (MEH-PPV) that exhibits substantial room-temperature magnetoresistance (20 initially suppressed by the doping, as the localized electronic spin mixes one of the two spins whose correlation controls the transport. At intermediate doping, when one spin is fully decohered but the other is not, there is a regime where the magnetoresistance is insensitive to the doping level. For much greater doping concentrations the magnetoresistance is fully suppressed as both spins that control the charge conductivity of the material are mixed. The behavior is described within a theoretical model describing the effect of carrier spin dynamics on the current. Generalizations to amorphous and other disordered crystalline semiconductors will also be described. This work was
NASA Astrophysics Data System (ADS)
Ivanov, D. A.; Lee, Patrick A.
1999-02-01
We study the nuclear spin-lattice relaxation rate 1/T1 in the two-leg antiferromagnetic spin-1/2 Heisenberg ladder. More specifically, we consider the contribution to 1/T1 from the processes with momentum transfer (π,π). In the limit of weak coupling between the two chains, this contribution is of activation type with gap 2Δ at low temperatures (Δ is the spin gap), but crosses over to a slowly decaying temperature dependence at the crossover temperature T~Δ. This crossover possibly explains the recent high-temperature NMR results on ladder-containing cuprates by Imai et al.
Nuclear spin conversion of methane in solid parahydrogen.
Miyamoto, Yuki; Fushitani, Mizuho; Ando, Daisuke; Momose, Takamasa
2008-03-21
The nuclear spin conversion of CH(4) and CD(4) isolated in solid parahydrogen was investigated by high resolution Fourier transform infrared spectroscopy. From the analysis of the temporal changes of rovibrational absorption spectra, the nuclear spin conversion rates associated with the rotational relaxation from the J=1 state to the J=0 state for both species were determined at temperatures between 1 and 6 K. The conversion rate of CD(4) was found to be 2-100 times faster than that of CH(4) in this temperature range. The faster conversion in CD(4) is attributed to the quadrupole interaction of D atoms in CD(4), while the conversion in CH(4) takes place mainly through the nuclear spin-nuclear spin interaction. The conversion rates depend on crystal temperature strongly above 3.5 K for CH(4) and above 2 K for CD(4), while the rates were almost constant below these temperatures. The temperature dependence indicates that the one-phonon process is dominant at low temperatures, while two-phonon processes become important at higher temperatures as a cause of the nuclear spin conversion. PMID:18361586
Dephasing due to Nuclear Spins in Large-Amplitude Electric Dipole Spin Resonance
NASA Astrophysics Data System (ADS)
Chesi, Stefano; Yang, Li-Ping; Loss, Daniel
2016-02-01
We analyze effects of the hyperfine interaction on electric dipole spin resonance when the amplitude of the quantum-dot motion becomes comparable or larger than the quantum dot's size. Away from the well-known small-drive regime, the important role played by transverse nuclear fluctuations leads to a Gaussian decay with characteristic dependence on drive strength and detuning. A characterization of spin-flip gate fidelity, in the presence of such additional drive-dependent dephasing, shows that vanishingly small errors can still be achieved at sufficiently large amplitudes. Based on our theory, we analyze recent electric dipole spin resonance experiments relying on spin-orbit interactions or the slanting field of a micromagnet. We find that such experiments are already in a regime with significant effects of transverse nuclear fluctuations and the form of decay of the Rabi oscillations can be reproduced well by our theory.
Combustion resistance of the 129Xe hyperpolarized nuclear spin state.
Stupic, Karl F; Six, Joseph S; Olsen, Michael D; Pavlovskaya, Galina E; Meersmann, Thomas
2013-01-01
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
Quantum and classical correlations in electron-nuclear spin echo
Zobov, V. E.
2014-11-15
The quantum properties of dynamic correlations in a system of an electron spin surrounded by nuclear spins under the conditions of free induction decay and electron spin echo have been studied. Analytical results for the time evolution of mutual information, classical part of correlations, and quantum part characterized by quantum discord have been obtained within the central-spin model in the high-temperature approximation. The same formulas describe discord in both free induction decay and spin echo although the time and magnetic field dependences are different because of difference in the parameters entering into the formulas. Changes in discord in the presence of the nuclear polarization β{sub I} in addition to the electron polarization β{sub S} have been calculated. It has been shown that the method of reduction of the density matrix to a two-spin electron-nuclear system provides a qualitatively correct description of pair correlations playing the main role at β{sub S} ≈ β{sub I} and small times. At large times, such correlations decay and multispin correlations ensuring nonzero mutual information and zero quantum discord become dominant.
Dynamics of a mesoscopic nuclear spin ensemble interacting with an optically driven electron spin
NASA Astrophysics Data System (ADS)
Stanley, M. J.; Matthiesen, C.; Hansom, J.; Le Gall, C.; Schulte, C. H. H.; Clarke, E.; Atatüre, M.
2014-11-01
The ability to discriminate between simultaneously occurring noise sources in the local environment of semiconductor InGaAs quantum dots, such as electric and magnetic field fluctuations, is key to understanding their respective dynamics and their effect on quantum dot coherence properties. We present a discriminatory approach to all-optical sensing based on two-color resonance fluorescence of a quantum dot charged with a single electron. Our measurements show that local magnetic field fluctuations due to nuclear spins in the absence of an external magnetic field are described by two correlation times, both in the microsecond regime. The nuclear spin bath dynamics show a strong dependence on the strength of resonant probing, with correlation times increasing by a factor of 4 as the optical transition is saturated. We interpret the behavior as motional averaging of both the Knight field of the resident electron spin and the hyperfine-mediated nuclear spin-spin interaction due to optically induced electron spin flips.
Theoretical aspects of Magic Angle Spinning - Dynamic Nuclear Polarization
NASA Astrophysics Data System (ADS)
Mentink-Vigier, Frederic; Akbey, Ümit; Oschkinat, Hartmut; Vega, Shimon; Feintuch, Akiva
2015-09-01
Magic Angle Spinning (MAS) combined with Dynamic Nuclear Polarization (DNP) has been proven in recent years to be a very powerful method for increasing solid-state NMR signals. Since the advent of biradicals such as TOTAPOL to increase the nuclear polarization new classes of radicals, with larger molecular weight and/or different spin properties have been developed. These have led to unprecedented signal gain, with varying results for different experimental parameters, in particular the microwave irradiation strength, the static field, and the spinning frequency. Recently it has been demonstrated that sample spinning imposes DNP enhancement processes that differ from the active DNP mechanism in static samples as upon sample spinning the DNP enhancements are the results of energy level anticrossings occurring periodically during each rotor cycle. In this work we present experimental results with regards to the MAS frequency dependence of the DNP enhancement profiles of four nitroxide-based radicals at two different sets of temperature, 110 and 160 K. In fact, different magnitudes of reduction in enhancement are observed with increasing spinning frequency. Our simulation code for calculating MAS-DNP powder enhancements of small model spin systems has been improved to extend our studies of the influence of the interaction and relaxation parameters on powder enhancements. To achieve a better understanding we simulated the spin dynamics of a single three-spin system {ea -eb - n } during its steady state rotor periods and used the Landau-Zener formula to characterize the influence of the different anti-crossings on the polarizations of the system and their necessary action for reaching steady state conditions together with spin relaxation processes. Based on these model calculations we demonstrate that the maximum steady state nuclear polarization cannot become larger than the maximum polarization difference between the two electrons during the steady state rotor cycle
Theoretical aspects of Magic Angle Spinning - Dynamic Nuclear Polarization.
Mentink-Vigier, Frederic; Akbey, Ümit; Oschkinat, Hartmut; Vega, Shimon; Feintuch, Akiva
2015-09-01
Magic Angle Spinning (MAS) combined with Dynamic Nuclear Polarization (DNP) has been proven in recent years to be a very powerful method for increasing solid-state NMR signals. Since the advent of biradicals such as TOTAPOL to increase the nuclear polarization new classes of radicals, with larger molecular weight and/or different spin properties have been developed. These have led to unprecedented signal gain, with varying results for different experimental parameters, in particular the microwave irradiation strength, the static field, and the spinning frequency. Recently it has been demonstrated that sample spinning imposes DNP enhancement processes that differ from the active DNP mechanism in static samples as upon sample spinning the DNP enhancements are the results of energy level anticrossings occurring periodically during each rotor cycle. In this work we present experimental results with regards to the MAS frequency dependence of the DNP enhancement profiles of four nitroxide-based radicals at two different sets of temperature, 110 and 160K. In fact, different magnitudes of reduction in enhancement are observed with increasing spinning frequency. Our simulation code for calculating MAS-DNP powder enhancements of small model spin systems has been improved to extend our studies of the influence of the interaction and relaxation parameters on powder enhancements. To achieve a better understanding we simulated the spin dynamics of a single three-spin system {ea-eb-n} during its steady state rotor periods and used the Landau-Zener formula to characterize the influence of the different anti-crossings on the polarizations of the system and their necessary action for reaching steady state conditions together with spin relaxation processes. Based on these model calculations we demonstrate that the maximum steady state nuclear polarization cannot become larger than the maximum polarization difference between the two electrons during the steady state rotor cycle. This
Imaging mesoscopic nuclear spin noise with a diamond magnetometer
NASA Astrophysics Data System (ADS)
Meriles, Carlos A.; Jiang, Liang; Goldstein, Garry; Hodges, Jonathan S.; Maze, Jeronimo; Lukin, Mikhail D.; Cappellaro, Paola
2010-09-01
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.
Optical Polarization of Nuclear Spins in Silicon Carbide
NASA Astrophysics Data System (ADS)
Falk, Abram L.; Klimov, Paul V.; Ivády, Viktor; Szász, Krisztián; Christle, David J.; Koehl, William F.; Gali, Ádám; Awschalom, David D.
2015-06-01
We demonstrate optically pumped dynamic nuclear polarization of 29Si nuclear spins that are strongly coupled to paramagnetic color centers in 4 H - and 6 H -SiC. The 9 9 % ±1 % degree of polarization that we observe at room temperature corresponds to an effective nuclear temperature of 5 μ K . By combining ab initio theory with the experimental identification of the color centers' optically excited states, we quantitatively model how the polarization derives from hyperfine-mediated level anticrossings. These results lay a foundation for SiC-based quantum memories, nuclear gyroscopes, and hyperpolarized probes for magnetic resonance imaging.
High-spin nuclear structure data on the Internet
Singh, B. |
1997-12-31
The study of nuclear structure at fast nuclear rotations, using fusion-evaporation reactions, started in the early sixties but since the experimental observation of superdeformation about a decade ago it has become one of the most pursued research topics in nuclear physics. Large gamma-ray detector arrays GAMMASPHERE, EUROGAM, and GASP were developed during the last few years and these continue to produce a wealth of new, information about the properties of nuclei at high spins, including superdeformation. It is considered vital to compile, evaluate and systematize published data on many thousands of levels and gamma rays and associated nuclear bands obtained in such studies and make these available to the research community in conveniently retrievable and modern formats. This talk will describe the numerical, bibliographic and other high-spin related databases that are already accessible via INTERNET. Present limitations and ways to improve the current status and display of such databases will also be discussed.
Experiments with Exotic Spin-Oriented Nuclear Beams and Examples of Nuclear Moment Measurements
NASA Astrophysics Data System (ADS)
Balabanski, D. L.; Neyens, G.; Borremans, D.; Coulier, N.; Daugas, J. M.; Teughels, S.; Georgiev, G.; Lewitowicz, M.; de Oliveira Santos, F.; Penionzhkevich, Yu. E.
2002-04-01
An overview of a series of recent experiments aimed at the determination of the moments of exotic nuclei is presented. The spin-orientation: spin-alignment and spin-polarization of the nuclear ensemble, which is produced in fragmentation reactions, is of utmost importance for these studies. The discussion emphasizes on the open problems related to the production and the preservation of the orientation during the experiments. Pros and contras for experiments at both, intermediate and high energies are considered. Examples from nuclear moment measurements, which were performed using the LISE-III spectrometer at GANIL, are provided. The spin-alignment and the spin-polarization of the nuclear ensemble were studied by the β-LMR, β-NMR and TDPAD experimental techniques. The experimental results are discussed in the framework of the kinematical model of the fragmentation reaction.
NASA Astrophysics Data System (ADS)
Forster, F.; Mühlbacher, M.; Schuh, D.; Wegscheider, W.; Giedke, G.; Ludwig, S.
2015-12-01
The control of nuclear spins in quantum dots is essential to explore their many-body dynamics and exploit their prospects for quantum information processing. We present a unique combination of dynamic nuclear spin polarization and electric-dipole-induced spin resonance in an electrostatically defined double quantum dot (DQD) exposed to the strongly inhomogeneous field of two on-chip nanomagnets. Our experiments provide direct and unrivaled access to the nuclear spin polarization distribution and allow us to establish and characterize multiple fixed points. Further, we demonstrate polarization of the DQD environment by nuclear spin diffusion which significantly stabilizes the nuclear spins inside the DQD.
Dependence of nuclear spin singlet lifetimes on RF spin-locking power
NASA Astrophysics Data System (ADS)
DeVience, Stephen J.; Walsworth, Ronald L.; Rosen, Matthew S.
2012-05-01
We measure the lifetime of long-lived nuclear spin singlet states as a function of the strength of the RF spin-locking field and present a simple theoretical model that agrees well with our measurements, including the low-RF-power regime. We also measure the lifetime of a long-lived coherence between singlet and triplet states that does not require a spin-locking field for preservation. Our results indicate that for many molecules, singlet states can be created using weak RF spin-locking fields: more than two orders of magnitude lower RF power than in previous studies. Our findings suggest that for many endogenous biomolecules, singlets and related states with enhanced lifetimes might be achievable in vivo with safe levels of RF power.
Nuclear moments of inertia at high spin
Deleplanque, M.A.
1982-10-01
The competition between collective motion and alignment at high spin can be evaluated by measuring two complementary dynamic moments of inertia. The first, I band, measured in ..gamma..-..gamma.. correlation experiments, relates to the collective properties of the nucleus. A new moment of inertia I/sub eff/ is defined here, which contains both collective and alignment effects. Both of these can be measured in continuum ..gamma..-ray spectra of rotational nuclei up to high frequencies. The evolution of ..gamma..-ray spectra for Er nuclei from mass 160 to 154 shows that shell effects can directly be observed in the spectra of the lighter nuclei.
Search for an Atomic EDM with Optical-Coupling Nuclear Spin Oscillator
Asahi, K.; Uchida, M.; Inoue, T.; Hatakeyama, N.; Yoshimi, A.
2007-06-13
We have constructed a nuclear spin oscillator of a new type, that employs a feedback scheme based on an optical spin detection and suceeding spin control by a transverse field application. This spin oscillator parallels the conventional spin maser in many points, but exhibits advantages and requirements that are different from those with the spin maser. By means of the optical-coupling nuclear spin oscillator, an experimental setup to search for an electric dipole moment (EDM) in a spin 1/2 diamagnetic atom 129Xe is being developed.
Decoherence-protected nuclear spin quantum register in diamond
NASA Astrophysics Data System (ADS)
Dobrovitski, Viatcheslav; Kuo, Wan Jung; Hanson, Ronald; Taminiau, Tim H.
2013-03-01
We analyze the decoherence-protected operation of a quantum register based on the nuclear spins surrounding a nitrogen-vacancy (NV) center in diamond. Combination of the decoherence protection with the quantum gates is achieved by applying the decoupling pulses to the NV center's electronic spin in resonance with the motion of one of the nuclear spins. In this way, many weakly coupled (tens of kHz) nuclei located far from the NV center can be combined in a quantum register. We study the limits, set by realistic experimental parameters, on the size of such a register and on the duration of the quantum gates needed for its operation. We also consider the ways of accelerating the quantum gate operation, and integration of the decoherence-protected gates with the decoupling of the nuclear spins themselves. We conclude that creation of such registers is feasible with current experimental capabilities. Work at the Ames Laboratory was supported by the Department of Energy - Basic Energy Sciences under Contract No. DE-AC02-07CH11358.
NASA Astrophysics Data System (ADS)
Chow, Colin M.; Ross, Aaron M.; Kim, Danny; Gammon, Daniel; Bracker, Allan S.; Sham, L. J.; Steel, Duncan G.
2016-08-01
We demonstrate the extension of coherence between all four two-electron spin ground states of an InAs quantum dot molecule (QDM) via nonlocal suppression of nuclear spin fluctuations in two vertically stacked quantum dots (QDs), while optically addressing only the top QD transitions. Long coherence times are revealed through dark-state spectroscopy as resulting from nuclear spin locking mediated by the exchange interaction between the QDs. Line shape analysis provides the first measurement of the quieting of the Overhauser field distribution correlating with reduced nuclear spin fluctuations.
Chow, Colin M; Ross, Aaron M; Kim, Danny; Gammon, Daniel; Bracker, Allan S; Sham, L J; Steel, Duncan G
2016-08-12
We demonstrate the extension of coherence between all four two-electron spin ground states of an InAs quantum dot molecule (QDM) via nonlocal suppression of nuclear spin fluctuations in two vertically stacked quantum dots (QDs), while optically addressing only the top QD transitions. Long coherence times are revealed through dark-state spectroscopy as resulting from nuclear spin locking mediated by the exchange interaction between the QDs. Line shape analysis provides the first measurement of the quieting of the Overhauser field distribution correlating with reduced nuclear spin fluctuations. PMID:27563998
Fast Room-Temperature Phase Gate on a Single Nuclear Spin in Diamond
NASA Astrophysics Data System (ADS)
Sangtawesin, S.; Brundage, T. O.; Petta, J. R.
2015-03-01
Nuclear spins support long lived quantum coherence due to weak coupling to the environment, but are difficult to rapidly control using nuclear magnetic resonance as a result of the small nuclear magnetic moment. We demonstrate a fast ~ 500 ns nuclear spin phase gate on a 14N nuclear spin qubit intrinsic to a nitrogen-vacancy center in high purity diamond. This phase gate is achieved by utilizing electron-nuclear hyperfine interaction. By driving off-resonant Rabi oscillations on the electronic spin, we can generate an arbitrary phase gate on the nuclear spin. We also demonstrate that repeated applications of π-phase gates can bang-bang decouple the nuclear spin from the environment, locking the spin state for up to 140 μs. Research was supported by the Sloan and Packard Foundations, the National Science Foundation through Awards DMR-0819860 and DMR-0846341, and the Army Research Office through PECASE Award W911NF-08-1-0189.
NASA Astrophysics Data System (ADS)
Heisterkamp, F.; Kirstein, E.; Greilich, A.; Zhukov, E. A.; Kazimierczuk, T.; Yakovlev, D. R.; Pawlis, A.; Bayer, M.
2016-02-01
We study the dynamics of optically induced nuclear spin polarization in a fluorine-doped ZnSe epilayer via time-resolved Kerr rotation. The nuclear polarization in the vicinity of a fluorine donor is induced by interaction with coherently precessing electron spins in a magnetic field applied in the Voigt geometry. It is detected by nuclei-induced changes in the electron spin coherence signal. This all-optical technique allows us to measure the longitudinal spin relaxation time T1 of the 77Se isotope in a magnetic field range from 10 to 130 mT under illumination. We combine the optical technique with radio frequency methods to address the coherent spin dynamics of the nuclei and measure Rabi oscillations, Ramsey fringes, and the nuclear spin echo. The inhomogeneous spin dephasing time T2* and the spin coherence time T2 of the 77Se isotope are measured. While the T1 time is on the order of several milliseconds, the T2 time is several hundred microseconds. The experimentally determined condition T1≫T2 verifies the validity of the classical model of nuclear spin cooling for describing the optically induced nuclear spin polarization.
Nuclear-spin-lattice relaxation in rhenium metal
Dimitropoulos, C.; Bucher, J.P.; Borsa, F.; Corti, M.
1989-04-01
Nuclear-spin-lattice relaxation measurements are presented for /sup 187/Re in Re metal as a function of temperature. The relaxation transition probabilities were extracted from the nuclear magnetization recovery curves both in high magnetic field (H/sub 0/ = 8 T) nuclear-magnetic-resonance experiments and in nuclear-quadrupole-resonance (H/sub 0/ = 0) experiments. It is found that the dominant relaxation mechanisms is due to magnetic rather then quadrupolar hyperfine interaction with W/sub M/ = 1.32 T. The data are analyzed in terms of the electronic structure of Re metal. The analysis confirms that Re is a ''weakly enhanced'' transition metal with a nuclear relaxation rate dominated by the s-contact hyperfine interaction.
Investigation of the Possibility of Using Nuclear Magnetic Spin Alignment
NASA Technical Reports Server (NTRS)
Dent, William V., Jr.
1998-01-01
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.
Fast Nuclear Spin Relaxation in Hyperpolarized Solid 129Xe
NASA Astrophysics Data System (ADS)
Kuzma, N. N.; Patton, B.; Raman, K.; Happer, W.
2002-04-01
We report extensive new measurements of the longitudinal relaxation time T1 of 129Xe nuclear spins in solid xenon. For temperatures T<120 K and magnetic fields B>0.05 T, we found T1 on the order of hours, in good agreement with previous measurements and with the predicted phonon-scattering limit for the spin-rotation interaction. For T>120 K, our new data show that T1 can be much shorter than the phonon scattering limit. For B = 0.06 T, a field often used to accumulate hyperpolarized xenon, T1 is ~6 s near the Xe melting point Tm = 161.4 K. From T = 50 K to Tm, the new data are in excellent agreement with the theoretical prediction that the relaxation is due to (i) modulation of the spin-rotation interaction by phonons, and (ii) modulation of the dipole-dipole interaction by vacancy diffusion.
Storing entanglement of nuclear spins via Uhrig dynamical decoupling
Roy, Soumya Singha; Mahesh, T. S.; Agarwal, G. S.
2011-06-15
Stroboscopic spin flips have already been shown to prolong the coherence times of quantum systems under noisy environments. Uhrig's dynamical decoupling scheme provides an optimal sequence for a quantum system interacting with a dephasing bath. Several experimental demonstrations have already verified the efficiency of such dynamical decoupling schemes in preserving single-qubit coherences. In this work we describe the experimental study of Uhrig's dynamical decoupling in preserving two-qubit entangled states using an ensemble of spin-1/2 nuclear pairs in solution state. We find that the performance of odd-order Uhrig sequences in preserving entanglement is superior to both even-order Uhrig sequences and periodic spin-flip sequences. We also find that there exists an optimal order of the Uhrig sequence in which a singlet state can be stored at high correlation for about 30 seconds.
Anisotropic nuclear spin relaxation in single-crystal xenon
NASA Astrophysics Data System (ADS)
Kuzma, N. N.; Babich, D.; Happer, W.
2002-04-01
We extend the theory of longitudinal spin relaxation of 129Xe nuclei in frozen xenon to the case of single-crystal samples, where the relaxation rate depends on the direction of the applied magnetic field with respect to the crystalline axes. For sufficiently large magnetic fields, the relaxation is dominated by spin-flip Raman scattering of lattice phonons. Two closely related interactions couple the lattice phonons to the spins of 129Xe nuclei: the nuclear spin-rotation interaction between nearest-neighbor atoms, which leads to an isotropic, field-independent relaxation rate, and the paramagnetic antishielding of the externally applied field at the site of 129Xe nuclei by the electrons of neighboring Xe atoms. The latter interaction, also known as the chemical shift anisotropy (CSA) interaction, leads to an anisotropic relaxation rate proportional to the square of the applied field. This mechanism dominates spin relaxation at fields of the order of the Debye field BD=kBTD/μB=82 T.
NASA Astrophysics Data System (ADS)
Cheng, Chi Y.; Ryley, Matthew S.; Peach, Michael J. G.; Tozer, David J.; Helgaker, Trygve; Teale, Andrew M.
2015-07-01
The Tamm-Dancoff approximation (TDA) can be applied to the computation of excitation energies using time-dependent Hartree-Fock (TD-HF) and time-dependent density-functional theory (TD-DFT). In addition to simplifying the resulting response equations, the TDA has been shown to significantly improve the calculation of triplet excitation energies in these theories, largely overcoming issues associated with triplet instabilities of the underlying reference wave functions. Here, we examine the application of the TDA to the calculation of another response property involving triplet perturbations, namely the indirect nuclear spin-spin coupling constant. Particular attention is paid to the accuracy of the triplet spin-dipole and Fermi-contact components. The application of the TDA in HF calculations leads to vastly improved results. For DFT calculations, the TDA delivers improved stability with respect to geometrical variations but does not deliver higher accuracy close to equilibrium geometries. These observations are rationalised in terms of the ground- and excited-state potential energy surfaces and, in particular, the severity of the triplet instabilities associated with each method. A notable feature of the DFT results within the TDA is their similarity across a wide range of different functionals. The uniformity of the TDA results suggests that some conventional evaluations may exploit error cancellations between approximations in the functional forms and those arising from triplet instabilities. The importance of an accurate treatment of correlation for evaluating spin-spin coupling constants is highlighted by this comparison.
Manipulation of the nuclear spin ensemble in a quantum dot with chirped magnetic resonance pulses
NASA Astrophysics Data System (ADS)
Munsch, Mathieu; Wüst, Gunter; Kuhlmann, Andreas V.; Xue, Fei; Ludwig, Arne; Reuter, Dirk; Wieck, Andreas D.; Poggio, Martino; Warburton, Richard J.
2014-09-01
The nuclear spins in nanostructured semiconductors play a central role in quantum applications. The nuclear spins represent a useful resource for generating local magnetic fields but nuclear spin noise represents a major source of dephasing for spin qubits. Controlling the nuclear spins enhances the resource while suppressing the noise. NMR techniques are challenging: the group III and V isotopes have large spins with widely different gyromagnetic ratios; in strained material there are large atom-dependent quadrupole shifts; and nanoscale NMR is hard to detect. We report NMR on 100,000 nuclear spins of a quantum dot using chirped radiofrequency pulses. Following polarization, we demonstrate a reversal of the nuclear spin. We can flip the nuclear spin back and forth a hundred times. We demonstrate that chirped NMR is a powerful way of determining the chemical composition, the initial nuclear spin temperatures and quadrupole frequency distributions for all the main isotopes. The key observation is a plateau in the NMR signal as a function of sweep rate: we achieve inversion at the first quantum transition for all isotopes simultaneously. These experiments represent a generic technique for manipulating nanoscale inhomogeneous nuclear spin ensembles and open the way to probe the coherence of such mesoscopic systems.
Hanle effect in (In,Ga)As quantum dots: Role of nuclear spin fluctuations
NASA Astrophysics Data System (ADS)
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
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.
129Xe EDM Search Experiment Using Active Nuclear Spin Maser
NASA Astrophysics Data System (ADS)
Sato, Tomoya; Ichikawa, Yuichi; Ohtomo, Yuichi; Sakamoto, Yu; Kojima, Shuichiro; Suzuki, Takahiro; Shirai, Hazuki; Chikamori, Masatoshi; Hikota, Eri; Miyatake, Hirokazu; Nanao, Tsubasa; Suzuki, Kunifumi; Tsuchiya, Masato; Inoue, Takeshi; Furukawa, Takeshi; Yoshimi, Akihiro; Bidinosti, Christopher P.; Ino, Takashi; Ueno, Hideki; Matsuo, Yukari; Fukuyama, Takeshi; Asahi, Koichiro
An active nuclear spin maser, which enables a precision measurement of spin precession frequency, is employed in the experimental search for permanent electric dipole moment (EDM) in the diamagnetic atom 129Xe. In order to eliminate systematic errors which limit the sensitivity of the experiment to an EDM, the following tactics are adopted: (i) 3He comagnetometry for the cancellation of long-term drifts in the external magnetic fields and (ii) double-cell geometry for the mitigation of frequency shifts due to interaction of 129Xe spin with polarized Rb atoms. In the present work, the design for the double-cell has been changed and a magnetic shield-coil system to provide a highly homogeneous magnetic field has been newly introduced. Thanks to increased polarization and longer 3He spin relaxation time, the dual-species maser of 129Xe and 3He in a double-cell geometry operated successfully. Our experiment is now at the stage of assembling these separate technical elements in order to start the measurement of 129Xe EDM in the 10-28 ecm region.
Coherent control of a single ²⁹Si nuclear spin qubit.
Pla, Jarryd J; Mohiyaddin, Fahd A; Tan, Kuan Y; Dehollain, Juan P; Rahman, Rajib; Klimeck, Gerhard; Jamieson, David N; Dzurak, Andrew S; Morello, Andrea
2014-12-12
Magnetic fluctuations caused by the nuclear spins of a host crystal are often the leading source of decoherence for many types of solid-state spin qubit. In group-IV semiconductor materials, the spin-bearing nuclei are sufficiently rare that it is possible to identify and control individual host nuclear spins. This Letter presents the first experimental detection and manipulation of a single ²⁹Si nuclear spin. The quantum nondemolition single-shot readout of the spin is demonstrated, and a Hahn echo measurement reveals a coherence time of T₂=6.3(7) ms—in excellent agreement with bulk experiments. Atomistic modeling combined with extracted experimental parameters provides possible lattice sites for the ²⁹Si atom under investigation. These results demonstrate that single ²⁹Si nuclear spins could serve as a valuable resource in a silicon spin-based quantum computer. PMID:25541792
Nuclear spin-spin coupling in a van der Waals-bonded system: xenon dimer.
Vaara, Juha; Hanni, Matti; Jokisaari, Jukka
2013-03-14
Nuclear spin-spin coupling over van der Waals bond has recently been observed via the frequency shift of solute protons in a solution containing optically hyperpolarized (129)Xe nuclei. We carry out a first-principles computational study of the prototypic van der Waals-bonded xenon dimer, where the spin-spin coupling between two magnetically non-equivalent isotopes, J((129)Xe - (131)Xe), is observable. We use relativistic theory at the four-component Dirac-Hartree-Fock and Dirac-density-functional theory levels using novel completeness-optimized Gaussian basis sets and choosing the functional based on a comparison with correlated ab initio methods at the nonrelativistic level. J-coupling curves are provided at different levels of theory as functions of the internuclear distance in the xenon dimer, demonstrating cross-coupling effects between relativity and electron correlation for this property. Calculations on small Xe clusters are used to estimate the importance of many-atom effects on J((129)Xe - (131)Xe). Possibilities of observing J((129)Xe - (131)Xe) in liquid xenon are critically examined, based on molecular dynamics simulation. A simplistic spherical model is set up for the xenon dimer confined in a cavity, such as in microporous materials. It is shown that the on the average shorter internuclear distance enforced by the confinement increases the magnitude of the coupling as compared to the bulk liquid case, rendering J((129)Xe - (131)Xe) in a cavity a feasible target for experimental investigation. PMID:23514495
Solid effect in magic angle spinning dynamic nuclear polarization
NASA Astrophysics Data System (ADS)
Corzilius, Björn; Smith, Albert A.; Griffin, Robert G.
2012-08-01
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 ω _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 ɛ = 91 obtained with the organic radical trityl (OX063) in magic angle spinning experiments performed at 5 T and 80 K. This is a factor of 6-7 higher than previous values in the literature under similar conditions. Because the solid effect depends strongly on the microwave field strength, we attribute this large enhancement to larger microwave field strengths inside the sample volume, achieved with more efficient coupling of the gyrotron to the sample chamber. In addition, we develop a theoretical model to explain the dependence of the buildup rate of enhanced nuclear polarization and the steady-state enhancement on the microwave power. Buildup times and enhancements were measured as a function of 1H concentration for both trityl and Gd-DOTA. Comparison of the results indicates that for trityl the initial polarization step is the slower, rate-determining step. However, for Gd-DOTA the spread of nuclear polarization via homonuclear 1H spin diffusion is rate-limiting. Finally, we discuss the applicability of the solid effect at fields > 5 T and the requirements to address the unfavorable field dependence of the solid effect.
Solid effect in magic angle spinning dynamic nuclear polarization
Corzilius, Björn; Smith, Albert A.; Griffin, Robert G.
2012-01-01
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 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} \\begin{equation*}\\omega _0 ^{ - 2}\\end{equation*} \\end{document}ω0−2 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 ɛ = 91 obtained with the organic radical trityl (OX063) in magic angle spinning experiments performed at 5 T and 80 K. This is a factor of 6-7 higher than previous values in the literature under similar conditions. Because the solid effect depends strongly on the microwave field strength, we attribute this large enhancement to larger microwave field strengths inside the sample volume, achieved with more efficient coupling of the gyrotron to the sample chamber. In addition, we develop a theoretical model to explain the dependence of the buildup rate of enhanced nuclear polarization and the steady-state enhancement on the microwave power. Buildup times and enhancements were measured as a function of 1H concentration for both trityl and Gd-DOTA. Comparison of the results indicates that for trityl the initial polarization step is the slower, rate-determining step. However, for Gd-DOTA the spread of nuclear polarization via homonuclear 1H spin diffusion is rate-limiting. Finally, we discuss the applicability of the solid effect at fields > 5 T and the requirements
Solid effect in magic angle spinning dynamic nuclear polarization.
Corzilius, Björn; Smith, Albert A; Griffin, Robert G
2012-08-01
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 ω(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 ε = 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
Voltage-induced conversion of helical to uniform nuclear spin polarization in a quantum wire
NASA Astrophysics Data System (ADS)
Kornich, Viktoriia; Stano, Peter; Zyuzin, Alexander A.; Loss, Daniel
2015-05-01
We study the effect of bias voltage on the nuclear spin polarization of a ballistic wire, which contains electrons and nuclei interacting via hyperfine interaction. In equilibrium, the localized nuclear spins are helically polarized due to the electron-mediated Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. Focusing here on nonequilibrium, we find that an applied bias voltage induces a uniform polarization, from both helically polarized and unpolarized spins available for spin flips. Once a macroscopic uniform polarization in the nuclei is established, the nuclear spin helix rotates with frequency proportional to the uniform polarization. The uniform nuclear spin polarization monotonically increases as a function of both voltage and temperature, reflecting a thermal activation behavior. Our predictions offer specific ways to test experimentally the presence of a nuclear spin helix polarization in semiconducting quantum wires.
Nuclear Spin Maser at Highly Stabilized Low Magnetic Field and Search for Atomic EDM
Yoshimi, A.; Asahi, K.; Inoue, T.; Uchida, M.; Hatakeyama, N.; Tsuchiya, M.; Kagami, S.
2009-08-04
A nuclear spin maser is operated at a low static field through an active feedback scheme based on an optical nuclear spin detection and succeeding spin control by a transverse field application. The frequency stability of this optical-coupling spin maser is improved by installation of a low-noise current source for a solenoid magnet producing a static magnetic field in the maser operation. Experimental devices for application of the maser to EDM experiment are being developed.
Nuclear Hydrogen for Peak Electricity Production and Spinning Reserve
Forsberg, C.W.
2005-01-20
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
Pulsed nuclear pumping and spin diffusion in a single charged quantum dot.
Ladd, Thaddeus D; Press, David; De Greve, Kristiaan; McMahon, Peter L; Friess, Benedikt; Schneider, Christian; Kamp, Martin; Höfling, Sven; Forchel, Alfred; Yamamoto, Yoshihisa
2010-09-01
We report the observation of a feedback process between the nuclear spins in a single charged quantum dot under coherently pulsed optical excitation and its trion transition. The optical pulse sequence intersperses resonant narrow-band pumping for spin initialization with off-resonant ultrafast pulses for coherent electron-spin rotation. A hysteretic sawtooth pattern in the free-induction decay of the single electron spin is observed; a mathematical model indicates a competition between optical nuclear pumping and nuclear spin-diffusion. This effect allows dynamic tuning of the electron Larmor frequency to a value determined by the pulse timing, potentially allowing more complex coherent control operations. PMID:20867546
NASA Astrophysics Data System (ADS)
Chekhovich, E. A.; Hopkinson, M.; Skolnick, M. S.; Tartakovskii, A. I.
2015-02-01
Interaction with nuclear spins leads to decoherence and information loss in solid-state electron-spin qubits. One particular, ineradicable source of electron decoherence arises from decoherence of the nuclear spin bath, driven by nuclear-nuclear dipolar interactions. Owing to its many-body nature nuclear decoherence is difficult to predict, especially for an important class of strained nanostructures where nuclear quadrupolar effects have a significant but largely unknown impact. Here, we report direct measurement of nuclear spin bath coherence in individual self-assembled InGaAs/GaAs quantum dots: spin-echo coherence times in the range 1.2-4.5 ms are found. Based on these values, we demonstrate that strain-induced quadrupolar interactions make nuclear spin fluctuations much slower compared with lattice-matched GaAs/AlGaAs structures. Our findings demonstrate that quadrupolar effects can potentially be used to engineer optically active III-V semiconductor spin-qubits with a nearly noise-free nuclear spin bath, previously achievable only in nuclear spin-0 semiconductors, where qubit network interconnection and scaling are challenging.
Chekhovich, E A; Hopkinson, M; Skolnick, M S; Tartakovskii, A I
2015-01-01
Interaction with nuclear spins leads to decoherence and information loss in solid-state electron-spin qubits. One particular, ineradicable source of electron decoherence arises from decoherence of the nuclear spin bath, driven by nuclear-nuclear dipolar interactions. Owing to its many-body nature nuclear decoherence is difficult to predict, especially for an important class of strained nanostructures where nuclear quadrupolar effects have a significant but largely unknown impact. Here, we report direct measurement of nuclear spin bath coherence in individual self-assembled InGaAs/GaAs quantum dots: spin-echo coherence times in the range 1.2-4.5 ms are found. Based on these values, we demonstrate that strain-induced quadrupolar interactions make nuclear spin fluctuations much slower compared with lattice-matched GaAs/AlGaAs structures. Our findings demonstrate that quadrupolar effects can potentially be used to engineer optically active III-V semiconductor spin-qubits with a nearly noise-free nuclear spin bath, previously achievable only in nuclear spin-0 semiconductors, where qubit network interconnection and scaling are challenging. PMID:25704639
Hyperfine-enhanced gyromagnetic ratio of a nuclear spin in diamond
NASA Astrophysics Data System (ADS)
Sangtawesin, S.; McLellan, C. A.; Myers, B. A.; Bleszynski Jayich, A. C.; Awschalom, D. D.; Petta, J. R.
2016-08-01
The nuclear spin gyromagnetic ratio can be enhanced by hyperfine coupling to the electronic spin. Here we show wide tunability of this enhancement on a 15N nuclear spin intrinsic to a single nitrogen-vacancy center in diamond. We perform control of the nuclear spin near the ground state level anti-crossing (GSLAC), where the enhancement of the gyromagnetic ratio from the ground state hyperfine coupling is maximized. We demonstrate a two order of magnitude enhancement of the effective nuclear gyromagnetic ratio compared to the value obtained at 500 G, a typical operating field that is suitable for nuclear spin polarization. Finally, we show that with strong enhancements, the nuclear spin ultimately suffers dephasing from the inhomogeneous broadening of the NMR transition frequency at the GSLAC.
Dynamics of entanglement of two electron spins interacting with nuclear spin baths in quantum dots
NASA Astrophysics Data System (ADS)
Bragar, Igor; Cywiński, Łukasz
2015-04-01
We study the dynamics of entanglement of two electron spins in two quantum dots, in which each electron is interacting with its nuclear spin environment. Focusing on the case of uncoupled dots, and starting from either Bell or Werner states of two qubits, we calculate the decay of entanglement due to the hyperfine interaction with the nuclei. We mostly focus on the regime of magnetic fields in which the bath-induced electron spin flips play a role, for example, their presence leads to the appearance of entanglement sudden death at finite time for two qubits initialized in a Bell state. For these fields, the intrabath dipolar interactions and spatial inhomogeneity of hyperfine couplings are irrelevant on the time scale of coherence (and entanglement) decay, and most of the presented calculations are performed using the uniform-coupling approximation to the exact hyperfine Hamiltonian. We provide a comprehensive overview of entanglement decay in this regime, considering both free evolution of the qubits, and an echo protocol with simultaneous application of π pulses to the two spins. All the currently relevant for experiments bath states are considered: the thermal state, narrowed states (characterized by diminished uncertainty of one of the components of the Overhauser field) of two uncorrelated baths, and a correlated narrowed state with a well-defined value of the z component of the Overhauser field interdot gradient. While we mostly use concurrence to quantify the amount of entanglement in a mixed state of the two electron spins, we also show that their entanglement dynamics can be reconstructed from measurements of the currently relevant for experiments entanglement witnesses and the fidelity of quantum teleportation, performed using a partially disentangled state as a resource.
Electron-Nuclear Spin Dynamics in a Mesoscopic Solid-State Quantum Computer
Berman, G.P.; Campbell, D.K.; Doolen, G.D.; Nagaev, K.E.
1998-12-07
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.
Mamone, Salvatore Concistrè, Maria; Carignani, Elisa; Meier, Benno; Krachmalnicoff, Andrea; Johannessen, Ole G.; Denning, Mark; Carravetta, Marina; Whitby, Richard J.; Levitt, Malcolm H.; Lei, Xuegong; Li, Yongjun; Goh, Kelvin; Horsewill, Anthony J.
2014-05-21
The water-endofullerene H{sub 2}O@C{sub 60} provides a unique chemical system in which freely rotating water molecules are confined inside homogeneous and symmetrical carbon cages. The spin conversion between the ortho and para species of the endohedral H{sub 2}O was studied in the solid phase by low-temperature nuclear magnetic resonance. The experimental data are consistent with a second-order kinetics, indicating a bimolecular spin conversion process. Numerical simulations suggest the simultaneous presence of a spin diffusion process allowing neighbouring ortho and para molecules to exchange their angular momenta. Cross-polarization experiments found no evidence that the spin conversion of the endohedral H{sub 2}O molecules is catalysed by {sup 13}C nuclei present in the cages.
NASA Astrophysics Data System (ADS)
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
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.
NMR response of nuclear-spin helix in quantum wires with hyperfine and spin-orbit interaction
NASA Astrophysics Data System (ADS)
Stano, Peter; Loss, Daniel
2014-11-01
We calculate the nuclear magnetic resonance (NMR) response of a quantum wire where at low temperature a self-sustained electron-nuclear spin order is created. Our model includes the electron mediated Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange, electron spin-orbit interactions, nuclear dipolar interactions, and the static and oscillating NMR fields, all of which play an essential role. The paramagnet to helimagnet transition in the nuclear system is reflected in an unusual response: it absorbs at a frequency given by the internal RKKY exchange field, rather than the external static field, whereas the latter leads to a splitting of the resonance peak.
Self-Polarization and Dynamical Cooling of Nuclear Spins in Double Quantum Dots
NASA Astrophysics Data System (ADS)
Rudner, M. S.; Levitov, L. S.
2007-07-01
The spin-blockade regime of double quantum dots features coupled dynamics of electron and nuclear spins resulting from the hyperfine interaction. We explain observed nuclear self-polarization via a mechanism based on feedback of the Overhauser shift on electron energy levels, and propose to use the instability toward self-polarization as a vehicle for controlling the nuclear spin distribution. In the dynamics induced by a properly chosen time-dependent magnetic field, nuclear spin fluctuations can be suppressed significantly below the thermal level.
Chekhovich, E.A.; Hopkinson, M.; Skolnick, M.S.; Tartakovskii, A.I.
2015-01-01
Interaction with nuclear spins leads to decoherence and information loss in solid-state electron-spin qubits. One particular, ineradicable source of electron decoherence arises from decoherence of the nuclear spin bath, driven by nuclear–nuclear dipolar interactions. Owing to its many-body nature nuclear decoherence is difficult to predict, especially for an important class of strained nanostructures where nuclear quadrupolar effects have a significant but largely unknown impact. Here, we report direct measurement of nuclear spin bath coherence in individual self-assembled InGaAs/GaAs quantum dots: spin-echo coherence times in the range 1.2–4.5 ms are found. Based on these values, we demonstrate that strain-induced quadrupolar interactions make nuclear spin fluctuations much slower compared with lattice-matched GaAs/AlGaAs structures. Our findings demonstrate that quadrupolar effects can potentially be used to engineer optically active III-V semiconductor spin-qubits with a nearly noise-free nuclear spin bath, previously achievable only in nuclear spin-0 semiconductors, where qubit network interconnection and scaling are challenging. PMID:25704639
Quenching of dynamic nuclear polarization by spin-orbit coupling in GaAs quantum dots.
Nichol, John M; Harvey, Shannon P; Shulman, Michael D; Pal, Arijeet; Umansky, Vladimir; Rashba, Emmanuel I; Halperin, Bertrand I; Yacoby, Amir
2015-01-01
The central-spin problem is a widely studied model of quantum decoherence. Dynamic nuclear polarization occurs in central-spin systems when electronic angular momentum is transferred to nuclear spins and is exploited in quantum information processing for coherent spin manipulation. However, the mechanisms limiting this process remain only partially understood. Here we show that spin-orbit coupling can quench dynamic nuclear polarization in a GaAs quantum dot, because spin conservation is violated in the electron-nuclear system, despite weak spin-orbit coupling in GaAs. Using Landau-Zener sweeps to measure static and dynamic properties of the electron spin-flip probability, we observe that the size of the spin-orbit and hyperfine interactions depends on the magnitude and direction of applied magnetic field. We find that dynamic nuclear polarization is quenched when the spin-orbit contribution exceeds the hyperfine, in agreement with a theoretical model. Our results shed light on the surprisingly strong effect of spin-orbit coupling in central-spin systems. PMID:26184854
Quenching of dynamic nuclear polarization by spin-orbit coupling in GaAs quantum dots
NASA Astrophysics Data System (ADS)
Nichol, John M.; Harvey, Shannon P.; Shulman, Michael D.; Pal, Arijeet; Umansky, Vladimir; Rashba, Emmanuel I.; Halperin, Bertrand I.; Yacoby, Amir
2015-07-01
The central-spin problem is a widely studied model of quantum decoherence. Dynamic nuclear polarization occurs in central-spin systems when electronic angular momentum is transferred to nuclear spins and is exploited in quantum information processing for coherent spin manipulation. However, the mechanisms limiting this process remain only partially understood. Here we show that spin-orbit coupling can quench dynamic nuclear polarization in a GaAs quantum dot, because spin conservation is violated in the electron-nuclear system, despite weak spin-orbit coupling in GaAs. Using Landau-Zener sweeps to measure static and dynamic properties of the electron spin-flip probability, we observe that the size of the spin-orbit and hyperfine interactions depends on the magnitude and direction of applied magnetic field. We find that dynamic nuclear polarization is quenched when the spin-orbit contribution exceeds the hyperfine, in agreement with a theoretical model. Our results shed light on the surprisingly strong effect of spin-orbit coupling in central-spin systems.
Dynamical decoupling design for identifying weakly coupled nuclear spins in a bath
NASA Astrophysics Data System (ADS)
Zhao, Nan; Wrachtrup, Jörg; Liu, Ren-Bao
2014-09-01
Identifying weakly coupled nuclear spins around single electron spins is a key step toward implementing quantum information processing using coupled electron-nuclei spin systems or sensing like single-spin nuclear magnetic resonance detection using diamond defect spins. Dynamical decoupling control of the center electron spin with periodic pulse sequences [e.g., the Carre-Purcell-Meiboom-Gill (CPMG) sequence] has been successfully used to identify single nuclear spins and to resolve structure of nuclear spin clusters. Here, we design a type of pulse sequence by replacing the repetition unit (a single π pulse) of the CPMG sequence with a group of nonuniformly spaced π pulses. Using the nitrogen-vacancy center system in diamond, we theoretically demonstrate that the designed pulse sequence improves the resolution of nuclear spin noise spectroscopy, and more information about the surrounding nuclear spins is extracted. The principle of dynamical decoupling design proposed in this paper is useful in many systems (e.g., defect spin qubit in solids, trapped ion, and superconducting qubit) for high-resolution noise spectroscopy.
NASA Astrophysics Data System (ADS)
Rao, K. Rama Koteswara; Suter, Dieter
2016-08-01
The nitrogen-vacancy (NV) center in diamond has attractive properties for a number of quantum technologies that rely on the spin angular momentum of the electron and the nuclei adjacent to the center. The nucleus with the strongest interaction is the 13C nuclear spin of the first shell. Using this degree of freedom effectively hinges on precise data on the hyperfine interaction between the electronic and the nuclear spin. Here, we present detailed experimental data on this interaction, together with an analysis that yields all parameters of the hyperfine tensor, as well as its orientation with respect to the atomic structure of the center.
Bowers, C.R.; Reno, J.L.; Simmons, J.A.; Vitkalov, S.A.
1998-12-01
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.
Quantum information processing with electronic and nuclear spins in semiconductors
NASA Astrophysics Data System (ADS)
Klimov, Paul Victor
Traditional electronic and communication devices operate by processing binary information encoded as bits. Such digital devices have led to the most advanced technologies that we encounter in our everyday lives and they influence virtually every aspect of our society. Nonetheless, there exists a much richer way to encode and process information. By encoding information in quantum mechanical states as qubits, phenomena such as coherence and entanglement can be harnessed to execute tasks that are intractable to digital devices. Under this paradigm, it should be possible to realize quantum computers, quantum communication networks and quantum sensors that outperform their classical counterparts. The electronic spin states of color-center defects in the semiconductor silicon carbide have recently emerged as promising qubit candidates. They have long-lived quantum coherence up to room temperature, they can be controlled with mature magnetic resonance techniques, and they have a built-in optical interface operating near the telecommunication bands. In this thesis I will present two of our contributions to this field. The first is the electric-field control of electron spin qubits. This development lays foundation for quantum electronics that operate via electrical gating, much like traditional electronics. The second is the universal control and entanglement of electron and nuclear spin qubits in an ensemble under ambient conditions. This development lays foundation for quantum devices that have a built-in redundancy and can operate in real-world conditions. Both developments represent important steps towards practical quantum devices in an electronic grade material.
Quantum limit for nuclear spin polarization in semiconductor quantum dots
NASA Astrophysics Data System (ADS)
Hildmann, Julia; Kavousanaki, Eleftheria; Burkard, Guido; Ribeiro, Hugo
2014-05-01
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.
Nuclear spin decoherence of neutral 31P donors in silicon: Effect of environmental 29Si nuclei
NASA Astrophysics Data System (ADS)
Petersen, Evan S.; Tyryshkin, A. M.; Morton, J. J. L.; Abe, E.; Tojo, S.; Itoh, K. M.; Thewalt, M. L. W.; Lyon, S. A.
2016-04-01
Spectral diffusion arising from 29Si nuclear spin flip-flops, known to be a primary source of electron spin decoherence in silicon, is also predicted to limit the coherence times of neutral donor nuclear spins in silicon. Here, the impact of this mechanism on 31P nuclear spin coherence is measured as a function of 29Si concentration using X -band pulsed electron nuclear double resonance. The 31P nuclear spin echo decays show that decoherence is controlled by 29Si flip-flops resulting in both fast (exponential) and slow (nonexponential) spectral diffusion processes. The decay times span a range from 100 ms in crystals containing 50% 29Si to 3 s in crystals containing 1% 29Si. These nuclear spin echo decay times for neutral donors are orders of magnitude longer than those reported for ionized donors in natural silicon. The electron spin of the neutral donors "protects" the donor nuclear spins by suppressing 29Si flip-flops within a "frozen core," as a result of the detuning of the 29Si spins caused by their hyperfine coupling to the electron spin.
High-spin nuclear structure studies with radioactive ion beams
Baktash, C.
1992-12-31
Two important developments in the sixties, namely the advent of heavy-ion accelerators and fabrication of Ge detectors, opened the way for the experimental studies of nuclear properties at high angular momentum. Addition of a new degree of freedom, namely spin, made it possible to observe such fascinating phenomena as occurrences and coexistence of a variety of novel shapes, rise, fall and occasionally rebirth of nuclear collectivity, and disappearance of pairing correlations. Today, with the promise of development of radioactive ion beams (RIB) and construction of the third-generation Ge-detection systems (GAMMASPHERE and EUROBALL), the authors are poised to explore new and equally fascinating phenomena that have been hitherto inaccessible. With the addition of yet another dimension, namely the isospin, they will be able to observe and verify predictions for exotic shapes as varied as rigid triaxiality, hyperdeformation and triaxial octupole shapes, or to investigate the T = 0 pairing correlations. In this paper, they shall review, separately for neutron-deficient and neutron-rich nuclei, these and a few other new high-spin physics opportunities that may be realized with RIB. Following this discussion, they shall present a list of the beam species, intensities and energies that are needed to fulfill these goals. The paper will conclude with a description of the experimental techniques and instrumentations that are required for these studies.
Mentink-Vigier, Frédéric; Paul, Subhradip; Lee, Daniel; Feintuch, Akiva; Hediger, Sabine; Vega, Shimon; De Paëpe, Gaël
2015-09-14
Over the last two decades solid state Nuclear Magnetic Resonance has witnessed a breakthrough in increasing the nuclear polarization, and thus experimental sensitivity, with the advent of Magic Angle Spinning Dynamic Nuclear Polarization (MAS-DNP). To enhance the nuclear polarization of protons, exogenous nitroxide biradicals such as TOTAPOL or AMUPOL are routinely used. Their efficiency is usually assessed as the ratio between the NMR signal intensity in the presence and the absence of microwave irradiation εon/off. While TOTAPOL delivers an enhancement εon/off of about 60 on a model sample, the more recent AMUPOL is more efficient: >200 at 100 K. Such a comparison is valid as long as the signal measured in the absence of microwaves is merely the Boltzmann polarization and is not affected by the spinning of the sample. However, recent MAS-DNP studies at 25 K by Thurber and Tycko (2014) have demonstrated that the presence of nitroxide biradicals combined with sample spinning can lead to a depolarized nuclear state, below the Boltzmann polarization. In this work we demonstrate that TOTAPOL and AMUPOL both lead to observable depolarization at ≈110 K, and that the magnitude of this depolarization is radical dependent. Compared to the static sample, TOTAPOL and AMUPOL lead, respectively, to nuclear polarization losses of up to 20% and 60% at a 10 kHz MAS frequency, while Trityl OX63 does not depolarize at all. This experimental work is analyzed using a theoretical model that explains how the depolarization process works under MAS and gives new insights into the DNP mechanism and into the spin parameters, which are relevant for the efficiency of a biradical. In light of these results, the outstanding performance of AMUPOL must be revised and we propose a new method to assess the polarization gain for future radicals. PMID:26235749
Long-range photon-mediated gate scheme between nuclear spin qubits in diamond
NASA Astrophysics Data System (ADS)
Auer, Adrian; Burkard, Guido
2016-01-01
Defect centers in diamond are exceptional solid-state quantum systems that can have exceedingly long electron and nuclear spin coherence times. So far, single-qubit gates for the nitrogen nuclear spin, a two-qubit gate with a nitrogen-vacancy (NV) center electron spin, and entanglement between nearby nitrogen nuclear spins have been demonstrated. Here, we develop a scheme to implement a universal two-qubit gate between two distant nitrogen nuclear spins. Virtual excitation of an NV center that is embedded in an optical cavity can scatter a laser photon into the cavity mode; we show that this process depends on the nuclear spin state of the nitrogen atom. If two NV centers are simultaneously coupled to a common cavity mode and individually excited, virtual cavity photon exchange can mediate an effective interaction between the nuclear spin qubits, conditioned on the spin state of both nuclei, which implements a universal controlled-Z gate. We predict operation times below 10 μ s , which is four orders of magnitude faster than the decoherence time of nuclear spin qubits in diamond.
Single-shot readout of multiple nuclear spin qubits in diamond under ambient conditions.
Dréau, A; Spinicelli, P; Maze, J R; Roch, J-F; Jacques, V
2013-02-01
We use the electronic spin of a single nitrogen-vacancy defect in diamond to observe the real-time evolution of neighboring single nuclear spins under ambient conditions. Using a diamond sample with a natural abundance of (13)C isotopes, we first demonstrate high fidelity initialization and single-shot readout of an individual (13)C nuclear spin. By including the intrinsic (14)N nuclear spin of the nitrogen-vacancy defect in the quantum register, we then report the simultaneous observation of quantum jumps linked to both nuclear spin species, providing an efficient initialization of the two qubits. These results open up new avenues for diamond-based quantum information processing including active feedback in quantum error correction protocols and tests of quantum correlations with solid-state single spins at room temperature. PMID:23432227
Robust Quantum-Network Memory Using Decoherence-Protected Subspaces of Nuclear Spins
NASA Astrophysics Data System (ADS)
Reiserer, Andreas; Kalb, Norbert; Blok, Machiel S.; van Bemmelen, Koen J. M.; Taminiau, Tim H.; Hanson, Ronald; Twitchen, Daniel J.; Markham, Matthew
2016-04-01
The realization of a network of quantum registers is an outstanding challenge in quantum science and technology. We experimentally investigate a network node that consists of a single nitrogen-vacancy center electronic spin hyperfine coupled to nearby nuclear spins. We demonstrate individual control and readout of five nuclear spin qubits within one node. We then characterize the storage of quantum superpositions in individual nuclear spins under repeated application of a probabilistic optical internode entangling protocol. We find that the storage fidelity is limited by dephasing during the electronic spin reset after failed attempts. By encoding quantum states into a decoherence-protected subspace of two nuclear spins, we show that quantum coherence can be maintained for over 1000 repetitions of the remote entangling protocol. These results and insights pave the way towards remote entanglement purification and the realization of a quantum repeater using nitrogen-vacancy center quantum-network nodes.
Optical pump-probe measurements of local nuclear spin coherence in semiconductor quantum wells.
Sanada, H; Kondo, Y; Matsuzaka, S; Morita, K; Hu, C Y; Ohno, Y; Ohno, H
2006-02-17
We demonstrate local manipulation and detection of nuclear spin coherence in semiconductor quantum wells by an optical pump-probe technique combined with pulse rf NMR. The Larmor precession of photoexcited electron spins is monitored by time-resolved Kerr rotation (TRKR) as a measure of nuclear magnetic field. Under the irradiation of resonant pulsed rf magnetic fields, Rabi oscillations of nuclear spins are traced by TRKR signals. The intrinsic coherence time evaluated by a spin-echo technique reveals the dependence on the orientation of the magnetic field with respect to the crystalline axis as expected by the nearest neighbor dipole-dipole interaction. PMID:16606048
Coherent manipulation of an NV center and one carbon nuclear spin
Scharfenberger, Burkhard; Nemoto, Kae; Munro, William J.
2014-12-04
We study a three-qubit system formed by the NV center’s electronic and nuclear spin plus an adjacent spin 1/2 carbon {sup 13}C. Specifically, we propose a manipulation scheme utilizing the hyperfine coupling of the effective S=1 degree of freedom of the vacancy electrons to the two adjacent nuclear spins to achieve accurate coherent control of all three qubits.
Nuclear Spin Dependent Parity Violation in Diatomic Molecules
NASA Astrophysics Data System (ADS)
Altuntas, Emine; Cahn, Sidney; Demille, David; Kozlov, Mikhail
2016-05-01
Nuclear spin-dependent parity violation (NSD-PV) effects arise from exchange of the Z0 boson between electrons and the nucleus, and from interaction of electrons with the nuclear anapole moment, a parity-odd magnetic moment. The latter scales with nucleon number of the nucleus A as A 2 / 3 , whereas the Z0 coupling is independent of A. Thus the former is the dominant source of NSD-PV for nuclei with A >= 20. We study NSD-PV effects using diatomic molecules, where signals are dramatically amplified by bringing rotational levels of opposite parity close to degeneracy in a strong magnetic field. The NSD-PV interaction matrix element is measured using a Stark-interference technique. We present results that demonstrate statistical sensitivity to NSD-PV effects surpassing that of any previous atomic parity violation measurement, using the test system 138 Ba19 F. We report our progress on measuring and cancelling systematic effects due to combination of non-reversing stray E-fields, Enr with B-field inhomogeneities. Short-term prospects for measuring the nuclear anapole moment of 137 Ba19 F are discussed. In the long term, our technique is sufficiently general and sensitive to enable measurements across a broad range of nuclei.
High-fidelity readout and control of a nuclear spin qubit in silicon.
Pla, Jarryd J; Tan, Kuan Y; Dehollain, Juan P; Lim, Wee H; Morton, John J L; Zwanenburg, Floris A; Jamieson, David N; Dzurak, Andrew S; Morello, Andrea
2013-04-18
Detection of nuclear spin precession is critical for a wide range of scientific techniques that have applications in diverse fields including analytical chemistry, materials science, medicine and biology. Fundamentally, it is possible because of the extreme isolation of nuclear spins from their environment. This isolation also makes single nuclear spins desirable for quantum-information processing, as shown by pioneering studies on nitrogen-vacancy centres in diamond. The nuclear spin of a (31)P donor in silicon is very promising as a quantum bit: bulk measurements indicate that it has excellent coherence times and silicon is the dominant material in the microelectronics industry. Here we demonstrate electrical detection and coherent manipulation of a single (31)P nuclear spin qubit with sufficiently high fidelities for fault-tolerant quantum computing. By integrating single-shot readout of the electron spin with on-chip electron spin resonance, we demonstrate quantum non-demolition and electrical single-shot readout of the nuclear spin with a readout fidelity higher than 99.8 percent-the highest so far reported for any solid-state qubit. The single nuclear spin is then operated as a qubit by applying coherent radio-frequency pulses. For an ionized (31)P donor, we find a nuclear spin coherence time of 60 milliseconds and a one-qubit gate control fidelity exceeding 98 percent. These results demonstrate that the dominant technology of modern electronics can be adapted to host a complete electrical measurement and control platform for nuclear-spin-based quantum-information processing. PMID:23598342
A 3D-printed high power nuclear spin polarizer.
Nikolaou, Panayiotis; Coffey, Aaron M; Walkup, Laura L; Gust, Brogan M; LaPierre, Cristen D; Koehnemann, Edward; Barlow, Michael J; Rosen, Matthew S; Goodson, Boyd M; Chekmenev, Eduard Y
2014-01-29
Three-dimensional printing with high-temperature plastic is used to enable spin exchange optical pumping (SEOP) and hyperpolarization of xenon-129 gas. The use of 3D printed structures increases the simplicity of integration of the following key components with a variable temperature SEOP probe: (i) in situ NMR circuit operating at 84 kHz (Larmor frequencies of (129)Xe and (1)H nuclear spins), (ii) <0.3 nm narrowed 200 W laser source, (iii) in situ high-resolution near-IR spectroscopy, (iv) thermoelectric temperature control, (v) retroreflection optics, and (vi) optomechanical alignment system. The rapid prototyping endowed by 3D printing dramatically reduces production time and expenses while allowing reproducibility and integration of "off-the-shelf" components and enables the concept of printing on demand. The utility of this SEOP setup is demonstrated here to obtain near-unity (129)Xe polarization values in a 0.5 L optical pumping cell, including ∼74 ± 7% at 1000 Torr xenon partial pressure, a record value at such high Xe density. Values for the (129)Xe polarization exponential build-up rate [(3.63 ± 0.15) × 10(-2) min(-1)] and in-cell (129)Xe spin-lattice relaxation time (T1 = 2.19 ± 0.06 h) for 1000 Torr Xe were in excellent agreement with the ratio of the gas-phase polarizations for (129)Xe and Rb (PRb ∼ 96%). Hyperpolarization-enhanced (129)Xe gas imaging was demonstrated with a spherical phantom following automated gas transfer from the polarizer. Taken together, these results support the development of a wide range of chemical, biochemical, material science, and biomedical applications. PMID:24400919
Antiferromagnetic nuclear spin helix and topological superconductivity in 13C nanotubes
NASA Astrophysics Data System (ADS)
Hsu, Chen-Hsuan; Stano, Peter; Klinovaja, Jelena; Loss, Daniel
2015-12-01
We investigate the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction arising from the hyperfine coupling between localized nuclear spins and conduction electrons in interacting 13C carbon nanotubes. Using the Luttinger liquid formalism, we show that the RKKY interaction is sublattice dependent, consistent with the spin susceptibility calculation in noninteracting carbon nanotubes, and it leads to an antiferromagnetic nuclear spin helix in finite-size systems. The transition temperature reaches up to tens of mK, due to a strong boost by a positive feedback through the Overhauser field from ordered nuclear spins. Similar to GaAs nanowires, the formation of the helical nuclear spin order gaps out half of the conduction electrons, and is therefore observable as a reduction of conductance by a factor of 2 in a transport experiment. The nuclear spin helix leads to a density wave combining spin and charge degrees of freedom in the electron subsystem, resulting in synthetic spin-orbit interaction, which induces nontrivial topological phases. As a result, topological superconductivity with Majorana fermion bound states can be realized in the system in the presence of proximity-induced superconductivity without the need of fine tuning the chemical potential. We present the phase diagram as a function of system parameters, including the pairing gaps, the gap due to the nuclear spin helix, and the Zeeman field perpendicular to the helical plane.
All-electrical control of a singlet-triplet qubit coupled to a single nuclear spin
NASA Astrophysics Data System (ADS)
Jacobson, N. Tobias; Harvey-Collard, Patrick; Baczewski, Andrew; Gamble, John; Rudolph, Martin; Nielsen, Erik; Muller, Richard; Carroll, Malcolm
Donor nuclear spins in isotopically purified silicon have very long coherence times, suggesting that they may form high-quality quantum memories. We propose that coupling these nuclear spins to few-electron quantum dots could enable nuclear spin readout and two-qubit operations of the joint quantum dot and nuclear spin system without the need for electron spin resonance. As a step towards this goal, our group recently demonstrated coherent singlet/triplet electron spin rotations induced by the hyperfine interaction between electronic spin degrees of freedom and a single nuclear spin in isotopically purified silicon. In this talk, I will discuss the feasibility of universal all-electrical control of such a singlet/triplet electron spin qubit and explore the decoherence mechanisms that we expect to dominate. Finally, I will examine the relative merits of AC and pulsed DC gating schemes. Sandia is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy National Nuclear Security Administration under Contract No. DE-AC04- 94AL85000.
Stable three-axis nuclear-spin gyroscope in diamond
NASA Astrophysics Data System (ADS)
Ajoy, Ashok; Cappellaro, Paola
2012-12-01
Gyroscopes find wide applications in everyday life from navigation and inertial sensing to rotation sensors in hand-held devices and automobiles. Current devices, based on either atomic or solid-state systems, impose a choice between long-time stability and high sensitivity in a miniaturized system. Here, we introduce a quantum sensor that overcomes these limitations by providing a sensitive and stable three-axis gyroscope in the solid state. We achieve high sensitivity by exploiting the long coherence time of the 14N nuclear spin associated with the nitrogen-vacancy center in diamond, combined with the efficient polarization and measurement of its electronic spin. Although the gyroscope is based on a simple Ramsey interferometry scheme, we use coherent control of the quantum sensor to improve its coherence time and robustness against long-time drifts. Such a sensor can achieve a sensitivity of η˜0.5(mdegs-1)/Hzmm3 while offering enhanced stability in a small footprint. In addition, we exploit the four axes of delocalization of the nitrogen-vacancy center to measure not only the rate of rotation, but also its direction, thus obtaining a compact three-axis gyroscope.
Frequency selective detection of nuclear quadrupole resonance (NQR) spin echoes
NASA Astrophysics Data System (ADS)
Somasundaram, Samuel D.; Jakobsson, Andreas; Smith, John A. S.; Althoefer, Kaspar A.
2006-05-01
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.
Spin-dependent modes in nuclei and nuclear forces
NASA Astrophysics Data System (ADS)
Suzuki, Toshio; Otsuka, Takaharu; Honma, Michio
2012-10-01
Spin-dependent modes in nuclei are studied and important roles of tensor and three-body forces on nuclear structure are discussed. New shell model Hamiltonians, which have proper tensor components, are shown to explain spin properties of both stable and exotic nuclei. Gamow-Teller (GT) strengths in Ni isotopes, especially in 56Ni, are found to be well described by pf-shell Hamiltonian GXPF1J, which leads to a remarkable improvement in the evaluation of electron capture rates in stellar environmnets. GT strength in 40Ar obtained with VMU (monopole-based universal interaction) is found to be consistent with the experimental strength, and neutrino capture reaction cross sections for solar neutrinos from 8B are found to be enhanced compared with previous calculations. The repulsive monopole corrections to the microscopic two-body interactions in isospin T=1 channel are important for the proper shell evolutions in neutron-rich isotopes. The three-body force, in particular the Fujita-Miyazawa force induced by δ excitations, is pointed out to be responsible for the repulsive corrections among the valence neutrons. The important roles of the three-body force on the energies of exotic calcium isotopes as well as on the closed-shell nature of 48Ca and M1 transition in 48Ca are demonstrated.
Atomic-Scale Nuclear Spin Imaging Using Quantum-Assisted Sensors in Diamond
NASA Astrophysics Data System (ADS)
Ajoy, A.; Bissbort, U.; Lukin, M. D.; Walsworth, R. L.; Cappellaro, P.
2015-01-01
Nuclear spin imaging at the atomic level is essential for the understanding of fundamental biological phenomena and for applications such as drug discovery. The advent of novel nanoscale sensors promises to achieve the long-standing goal of single-protein, high spatial-resolution structure determination under ambient conditions. In particular, quantum sensors based on the spin-dependent photoluminescence of nitrogen-vacancy (NV) centers in diamond have recently been used to detect nanoscale ensembles of external nuclear spins. While NV sensitivity is approaching single-spin levels, extracting relevant information from a very complex structure is a further challenge since it requires not only the ability to sense the magnetic field of an isolated nuclear spin but also to achieve atomic-scale spatial resolution. Here, we propose a method that, by exploiting the coupling of the NV center to an intrinsic quantum memory associated with the nitrogen nuclear spin, can reach a tenfold improvement in spatial resolution, down to atomic scales. The spatial resolution enhancement is achieved through coherent control of the sensor spin, which creates a dynamic frequency filter selecting only a few nuclear spins at a time. We propose and analyze a protocol that would allow not only sensing individual spins in a complex biomolecule, but also unraveling couplings among them, thus elucidating local characteristics of the molecule structure.
NASA Astrophysics Data System (ADS)
Onur, A. R.; de Jong, J. P.; O'Shea, D.; Reuter, D.; Wieck, A. D.; van der Wal, C. H.
2016-04-01
We experimentally demonstrate how coherent population trapping (CPT) for donor-bound electron spins in GaAs results in autonomous feedback that prepares stabilized states for the spin polarization of nuclei around the electrons. CPT was realized by excitation with two lasers to a bound-exciton state. Transmission studies of the spectral CPT feature on an ensemble of electrons directly reveal the statistical distribution of prepared nuclear-spin states. Tuning the laser driving from blue to red detuned drives a transition from one to two stable states. Our results have importance for ongoing research on schemes for dynamic nuclear-spin polarization, the central spin problem, and control of spin coherence.
Influence of spin polarizability on liquid gas phase transition in the nuclear matter
NASA Astrophysics Data System (ADS)
Rezaei, Z.; Bigdeli, M.; Bordbar, G. H.
2015-10-01
In this paper, we investigate the liquid gas phase transition for the spin polarized nuclear matter. Applying the lowest order constrained variational (LOCV) method, and using two microscopic potentials, AV18 and UV14+TNI, we calculate the free energy, equation of state (EOS), order parameter, entropy, heat capacity and compressibility to derive the critical properties of spin polarized nuclear matter. Our results indicate that for the spin polarized nuclear matter, the second-order phase transition takes place at lower temperatures with respect to the unpolarized one. It is also shown that the critical temperature of our spin polarized nuclear matter with a specific value of spin polarization parameter is in good agreement with the experimental result.
Recursive polarization of nuclear spins in diamond at arbitrary magnetic fields
Pagliero, Daniela; Laraoui, Abdelghani; Henshaw, Jacob D.; Meriles, Carlos A.
2014-12-15
We introduce an alternate route to dynamically polarize the nuclear spin host of nitrogen-vacancy (NV) centers in diamond. Our approach articulates optical, microwave, and radio-frequency pulses to recursively transfer spin polarization from the NV electronic spin. Using two complementary variants of the same underlying principle, we demonstrate nitrogen nuclear spin initialization approaching 80% at room temperature both in ensemble and single NV centers. Unlike existing schemes, our approach does not rely on level anti-crossings and is thus applicable at arbitrary magnetic fields. This versatility should prove useful in applications ranging from nanoscale metrology to sensitivity-enhanced NMR.
Turro, Nicholas J.
1983-01-01
The course of chemical reactions involving radical pairs may depend on occurrence and orientation of nuclear spins in the pairs. The influence of nuclear spins is maximized when the radical pairs are confined to a space that serves as a cage that allows a certain degree of independent diffusional and rotational motion of the partners of the pair but that also encourages reencounters of the partners within a period which allows the nuclear spins to operate on the odd electron spins of the pair. Under the proper conditions, the nuclear spins can induce intersystem crossing between triplet and singlet states of radical pairs. It is shown that this dependence of intersystem crossing on nuclear spin leads to a magnetic isotope effect on the chemistry of radical pairs which provides a means of separating isotopes on the basis of nuclear spins rather than nuclear masses and also leads to a magnetic field effect on the chemistry of radical pairs which provides a means of influencing the course of polymerization by the application of weak magnetic fields. PMID:16593273
A 3D-Printed High Power Nuclear Spin Polarizer
Nikolaou, Panayiotis; Coffey, Aaron M.; Walkup, Laura L.; Gust, Brogan M.; LaPierre, Cristen D.; Koehnemann, Edward; Barlow, Michael J.; Rosen, Matthew S.; Goodson, Boyd M.; Chekmenev, Eduard Y.
2015-01-01
Three-dimensional printing with high-temperature plastic is used to enable spin exchange optical pumping (SEOP) and hyperpolarization of xenon-129 gas. The use of 3D printed structures increases the simplicity of integration of the following key components with a variable temperature SEOP probe: (i) in situ NMR circuit operating at 84 kHz (Larmor frequencies of 129Xe and 1H nuclear spins), (ii) <0.3 nm narrowed 200 W laser source, (iii) in situ high-resolution near-IR spectroscopy, (iv) thermoelectric temperature control, (v) retroreflection optics, and (vi) optomechanical alignment system. The rapid prototyping endowed by 3D printing dramatically reduces production time and expenses while allowing reproducibility and integration of “off-the-shelf” components and enables the concept of printing on demand. The utility of this SEOP setup is demonstrated here to obtain near-unity 129Xe polarization values in a 0.5 L optical pumping cell, including ~74 ± 7% at 1000 Torr xenon partial pressure, a record value at such high Xe density. Values for the 129Xe polarization exponential build-up rate [(3.63 ± 0.15) × 10−2 min−1] and in-cell 129Xe spin−lattice relaxation time (T1 = 2.19 ± 0.06 h) for 1000 Torr Xe were in excellent agreement with the ratio of the gas-phase polarizations for 129Xe and Rb (PRb ~ 96%). Hyperpolarization-enhanced 129Xe gas imaging was demonstrated with a spherical phantom following automated gas transfer from the polarizer. Taken together, these results support the development of a wide range of chemical, biochemical, material science, and biomedical applications. PMID:24400919
Qubit Control Limited by Spin-Lattice Relaxation in a Nuclear Spin-Free Iron(III) Complex.
Zadrozny, Joseph M; Freedman, Danna E
2015-12-21
High-spin transition metal complexes are of interest as candidates for quantum information processing owing to the tunability of the pairs of MS levels for use as quantum bits (qubits). Thus, the design of high-spin systems that afford qubits with stable superposition states is of primary importance. Nuclear spins are a potent instigator of superposition instability; thus, we probed the Ph4P(+) salt of the nuclear spin-free complex [Fe(C5O5)3](3-) (1) to see if long-lived superpositions were possible in such a system. Continuous-wave and pulsed electron paramagnetic resonance (EPR) spectroscopic measurements reveal a strong EPR transition at X-band that can be utilized as a qubit. However, at 5 K the coherent lifetime, T2, for this resonance is 721(3) ns and decreases rapidly with increasing temperature. Simultaneously, the spin-lattice relaxation time is extremely short, 11.33(1) μs, at 5 K, and also rapidly decreases with increasing temperature. The coincidence of these two temperature-dependent data sets suggests that T2 in 1 is strongly limited by the short T1. Importantly, these results highlight the need for new design parameters in pursuit of high-spin species with appreciable coherence times. PMID:26650962
Quantum state transfer between an optomechanical cavity and a diamond nuclear spin ensemble
NASA Astrophysics Data System (ADS)
Feng, Zhi-Bo; Wang, Hong-Ling; Yan, Run-Ying
2016-08-01
We explore an efficient scheme for transferring quantum state between an optomechanical cavity and nuclear spins of nitrogen-vacancy centers in diamond, where quantum information can be efficiently stored (retrieved) into (from) the nuclear spin ensemble assisted by a mechanical resonator in a dispersive regime. Our scheme works for a broad range of cavity frequencies and might have potential applications in employing the nuclear spin ensemble as a memory in quantum information processing. The feasibility of our protocol is analyzed using currently available parameters.
Projective measurement of a single nuclear spin qubit by using two-mode cavity QED.
Eto, Yujiro; Noguchi, Atsushi; Zhang, Peng; Ueda, Masahito; Kozuma, Mikio
2011-04-22
We report the implementation of projective measurement on a single 1/2 nuclear spin of the (171)Yb atom by measuring the polarization of cavity-enhanced fluorescence. To obtain cavity-enhanced fluorescence having a nuclear-spin-dependent polarization, we construct a two-mode cavity QED system, in which two cyclic transitions are independently coupled to each of the orthogonally polarized cavity modes, by manipulating the energy level of (171)Yb. This system can associate the nuclear spin degrees of freedom with the polarization of photons, which will facilitate the development of hybrid quantum systems. PMID:21599343
Boundary between the thermal and statistical polarization regimes in a nuclear spin ensemble
NASA Astrophysics Data System (ADS)
Herzog, B. E.; Cadeddu, D.; Xue, F.; Peddibhotla, P.; Poggio, M.
2014-07-01
As the number of spins in an ensemble is reduced, the statistical fluctuations in its polarization eventually exceed the mean thermal polarization. This transition has now been surpassed in a number of recent nuclear magnetic resonance experiments, which achieve nanometer-scale detection volumes. Here, we measure nanometer-scale ensembles of nuclear spins in a KPF6 sample using magnetic resonance force microscopy. In particular, we investigate the transition between regimes dominated by thermal and statistical nuclear polarization. The ratio between the two types of polarization provides a measure of the number of spins in the detected ensemble.
Boundary between the thermal and statistical polarization regimes in a nuclear spin ensemble
Herzog, B. E.; Cadeddu, D.; Xue, F.; Peddibhotla, P.; Poggio, M.
2014-07-28
As the number of spins in an ensemble is reduced, the statistical fluctuations in its polarization eventually exceed the mean thermal polarization. This transition has now been surpassed in a number of recent nuclear magnetic resonance experiments, which achieve nanometer-scale detection volumes. Here, we measure nanometer-scale ensembles of nuclear spins in a KPF{sub 6} sample using magnetic resonance force microscopy. In particular, we investigate the transition between regimes dominated by thermal and statistical nuclear polarization. The ratio between the two types of polarization provides a measure of the number of spins in the detected ensemble.
Quantum state transfer between an optomechanical cavity and a diamond nuclear spin ensemble
NASA Astrophysics Data System (ADS)
Feng, Zhi-Bo; Wang, Hong-Ling; Yan, Run-Ying
2016-05-01
We explore an efficient scheme for transferring quantum state between an optomechanical cavity and nuclear spins of nitrogen-vacancy centers in diamond, where quantum information can be efficiently stored (retrieved) into (from) the nuclear spin ensemble assisted by a mechanical resonator in a dispersive regime. Our scheme works for a broad range of cavity frequencies and might have potential applications in employing the nuclear spin ensemble as a memory in quantum information processing. The feasibility of our protocol is analyzed using currently available parameters.
King, Jonathan P.; Jeong, Keunhong; Vassiliou, Christophoros C.; Shin, Chang S.; Page, Ralph H.; Avalos, Claudia E.; Wang, Hai-Jing; Pines, Alexander
2015-12-07
Low detection sensitivity stemming from the weak polarization of nuclear spins is a primary limitation of magnetic resonance spectroscopy and imaging. Methods have been developed to enhance nuclear spin polarization but they typically require high magnetic fields, cryogenic temperatures or sample transfer between magnets. Here we report bulk, room-temperature hyperpolarization of 13C nuclear spins observed via high-field magnetic resonance. The technique harnesses the high optically induced spin polarization of diamond nitrogen vacancy centres at room temperature in combination with dynamic nuclear polarization. We observe bulk nuclear spin polarization of 6%, an enhancement of ~170,000 over thermal equilibrium. The signal ofmore » the hyperpolarized spins was detected in situ with a standard nuclear magnetic resonance probe without the need for sample shuttling or precise crystal orientation. In conclusion, hyperpolarization via optical pumping/dynamic nuclear polarization should function at arbitrary magnetic fields enabling orders of magnitude sensitivity enhancement for nuclear magnetic resonance of solids and liquids under ambient conditions.« less
King, Jonathan P.; Jeong, Keunhong; Vassiliou, Christophoros C.; Shin, Chang S.; Page, Ralph H.; Avalos, Claudia E.; Wang, Hai-Jing; Pines, Alexander
2015-12-07
Low detection sensitivity stemming from the weak polarization of nuclear spins is a primary limitation of magnetic resonance spectroscopy and imaging. Methods have been developed to enhance nuclear spin polarization but they typically require high magnetic fields, cryogenic temperatures or sample transfer between magnets. Here we report bulk, room-temperature hyperpolarization of 13C nuclear spins observed via high-field magnetic resonance. The technique harnesses the high optically induced spin polarization of diamond nitrogen vacancy centres at room temperature in combination with dynamic nuclear polarization. We observe bulk nuclear spin polarization of 6%, an enhancement of ~170,000 over thermal equilibrium. The signal of the hyperpolarized spins was detected in situ with a standard nuclear magnetic resonance probe without the need for sample shuttling or precise crystal orientation. In conclusion, hyperpolarization via optical pumping/dynamic nuclear polarization should function at arbitrary magnetic fields enabling orders of magnitude sensitivity enhancement for nuclear magnetic resonance of solids and liquids under ambient conditions.
King, Jonathan P.; Jeong, Keunhong; Vassiliou, Christophoros C.; Shin, Chang S.; Page, Ralph H.; Avalos, Claudia E.; Wang, Hai-Jing; Pines, Alexander
2015-01-01
Low detection sensitivity stemming from the weak polarization of nuclear spins is a primary limitation of magnetic resonance spectroscopy and imaging. Methods have been developed to enhance nuclear spin polarization but they typically require high magnetic fields, cryogenic temperatures or sample transfer between magnets. Here we report bulk, room-temperature hyperpolarization of 13C nuclear spins observed via high-field magnetic resonance. The technique harnesses the high optically induced spin polarization of diamond nitrogen vacancy centres at room temperature in combination with dynamic nuclear polarization. We observe bulk nuclear spin polarization of 6%, an enhancement of ∼170,000 over thermal equilibrium. The signal of the hyperpolarized spins was detected in situ with a standard nuclear magnetic resonance probe without the need for sample shuttling or precise crystal orientation. Hyperpolarization via optical pumping/dynamic nuclear polarization should function at arbitrary magnetic fields enabling orders of magnitude sensitivity enhancement for nuclear magnetic resonance of solids and liquids under ambient conditions. PMID:26639147
Decoupling a spin qubit from high-frequency Larmor dynamics of a GaAs nuclear spin bath
NASA Astrophysics Data System (ADS)
Malinowski, Filip K.; Martins, Frederico; Nissen, Peter D.; Rudner, Mark S.; Marcus, Charles M.; Kuemmeth, Ferdinand; Barnes, Edwin; Fallahi, Saeed; Gardner, Geoffrey C.; Manfra, Michael J.
We present a technique of decoupling a spin qubit in a GaAs/AlGaAs heterostructure from low- and high-frequency noise arising from hyperfine interaction of electrons with nuclear spins. We use Carr-Purcell-Meiboom-Gill sequences in which we synchronize the repetition rate of π pulses to difference Larmor frequencies of 69Ga, 71Ga and 75As nuclei. This decouples the qubit both from low-frequency noise due to diffusion of nuclear spins and from noise at selected high frequencies, allowing us to apply more than a thousand π pulses in a sequence. We demonstrate a coherence time of a singlet-triplet qubit of 0.87 ms, i.e. five orders of magnitude longer than the inhomogeneous dephasing time intrinsic to GaAs. Support through IARPA-MQCO, Army Research Office, LPS-MPO-CMTC, the Villum Foundation and the Danish National Research Foundation is acknowledged.
NASA Astrophysics Data System (ADS)
Jiang, Li; Zhang, Guo-Feng
2016-08-01
The effects of nuclear field and spin-orbit interaction on dense coding and swap operation are studied in detail for both the antiferromagnetic (AFM) and ferromagnetic (FM) coupling cases. The conditions for a valid dense coding and under which swap operation is feasible are given.
Positioning nuclear spins in interacting clusters for quantum technologies and bioimaging
NASA Astrophysics Data System (ADS)
Wang, Zhen-Yu; Haase, Jan F.; Casanova, Jorge; Plenio, Martin B.
2016-05-01
We propose a method to measure the hyperfine vectors between a nitrogen-vacancy (NV) center and an environment of interacting nuclear spins. Our protocol enables the generation of tunable electron-nuclear coupling Hamiltonians while suppressing unwanted internuclear interactions. In this manner, each nucleus can be addressed and controlled individually, thereby permitting the reconstruction of the individual hyperfine vectors. With this ability the three-dimensional (3D) structure of spin ensembles and spins in biomolecules can be identified without the necessity of varying the direction of applied magnetic fields. We demonstrate examples including the complete reconstruction of an interacting spin cluster in diamond and 3D imaging of all the nuclear spins in a biomolecule.
Lattice dynamics in spin-crossover nanoparticles through nuclear inelastic scattering
NASA Astrophysics Data System (ADS)
Félix, Gautier; Mikolasek, Mirko; Peng, Haonan; Nicolazzi, William; Molnár, Gábor; Chumakov, Aleksandr I.; Salmon, Lionel; Bousseksou, Azzedine
2015-01-01
We used nuclear inelastic scattering (NIS) to investigate the lattice dynamics in [Fe(pyrazine)(Ni(CN)4)] spin crossover nanoparticles. The vibrational density of states of iron was extracted from the NIS data, which allowed to determine characteristic thermodynamical and lattice dynamical parameters as well as their spin-state dependence. The optical part of the NIS spectra compares well with the Raman scattering data reflecting the expansion/contraction of the coordination octahedron during the spin transition. From the acoustic part, we extracted the sound velocity in the low-spin (vLS=2073 ±31 m s-1) and high-spin (vHS=1942 ±23 m s-1) states of the particles. The spin-state dependence of this parameter is of primary interest to rationalize the spin-transition behavior in solids as well as its dynamics and finite size effects.
NASA Astrophysics Data System (ADS)
Halse, Meghan E.; Zagdoun, Alexandre; Dumez, Jean-Nicolas; Emsley, Lyndon
2015-05-01
A method for quantitatively calculating nuclear spin diffusion constants directly from crystal structures is introduced. This approach uses the first-principles low-order correlations in Liouville space (LCL) method to simulate spin diffusion in a box, starting from atomic geometry and including both magic-angle spinning (MAS) and powder averaging. The LCL simulations are fit to the 3D diffusion equation to extract quantitative nuclear spin diffusion constants. We demonstrate this method for the case of 1H spin diffusion in ice and L-histidine, obtaining diffusion constants that are consistent with literature values for 1H spin diffusion in polymers and that follow the expected trends with respect to magic-angle spinning rate and the density of nuclear spins. In addition, we show that this method can be used to model 13C spin diffusion in diamond and therefore has the potential to provide insight into applications such as the transport of polarization in non-protonated systems.
The determination of the in situ structure by nuclear spin contrast variation
Stuhrmann, H.B.; Nierhaus, K.H.
1994-12-31
Polarized neutron scattering from polarized nuclear spins in hydrogenous substances opens a new way of contrast variation. The enhanced contrast due to proton spin polarization was used for the in situ structure determination of tRNA of the functional complex of the E.coli ribosome.
Cho, Herman M.; Washton, Nancy M.; Mueller, Karl T.; Sears, Jr., Jesse A.; Townsend, Mark R.; Ewing, James R.
2016-06-14
A magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) probe is described that includes double containment enclosures configured to seal and contain hazardous samples for analysis. The probe is of a modular design that ensures containment of hazardous samples during sample analysis while preserving spin speeds for superior NMR performance and convenience of operation.
Nuclear-Spin Gyroscope Based on an Atomic Co-Magnetometer
NASA Technical Reports Server (NTRS)
Romalis, Michael; Komack, Tom; Ghost, Rajat
2008-01-01
An experimental nuclear-spin gyroscope is based on an alkali-metal/noblegas co-magnetometer, which automatically cancels the effects of magnetic fields. Whereas the performances of prior nuclear-spin gyroscopes are limited by sensitivity to magnetic fields, this gyroscope is insensitive to magnetic fields and to other external perturbations. In addition, relative to prior nuclear-spin gyroscopes, this one exhibits greater sensitivity to rotation. There is commercial interest in development of small, highly sensitive gyroscopes. The present experimental device could be a prototype for development of nuclear spin gyroscopes suitable for navigation. In comparison with fiber-optic gyroscopes, these gyroscopes would draw less power and would be smaller, lighter, more sensitive, and less costly.
Microscopic control of 29Si nuclear spins near phosphorus donors in silicon
NASA Astrophysics Data System (ADS)
Järvinen, J.; Zvezdov, D.; Ahokas, J.; Sheludyakov, S.; Vainio, O.; Lehtonen, L.; Vasiliev, S.; Fujii, Y.; Mitsudo, S.; Mizusaki, T.; Gwak, M.; Lee, SangGap; Lee, Soonchil; Vlasenko, L.
2015-09-01
We demonstrate an efficient control of 29Si nuclear spins for specific lattice sites near 31P donors in silicon at temperatures below 1 K and in a high magnetic field of 4.6 T. Excitation of the forbidden electron-nuclear transitions leads to a pattern of well-resolved holes and peaks in the electron spin resonance (ESR) lines of 31P . The pattern originates from dynamic polarization (DNP) of the 29Si nuclear spins near the donors via the solid effect. DNP of 29Si is demonstrated also with the Overhauser effect where the allowed ESR transitions are excited. In this case mostly the remote 29Si nuclei having weak interaction with the donors are polarized, which results in a single hole and a sharp peak pair in the ESR spectrum. Our work shows that the solid effect can be used for initialization of 29Si nuclear spin qubits near the donors.
Investigation of ultrafast nuclear spin polarization induced by short laser pulses.
Nakajima, Takashi
2007-07-13
We theoretically investigate the dynamics of nuclear spin induced by short laser pulses and show that ultrafast nuclear spin polarization can take place. Combined use of the hyperfine interaction together with the static electric field is the key for that. Specifically we apply the idea to unstable isotopes, (27)Mg and (37)Ca, with nuclear spin of 1/2 and 3/2, respectively, and show that 88% and 62% of nuclear spin polarization can be achieved within a few to tens of ns, which is 2-3 orders of magnitude shorter than the time needed for any known optical methods. Because of its ultrafast nature, our scheme would be very effective not only for stable nuclei but also unstable nuclei with a lifetime as short as mus. PMID:17678226
NASA Astrophysics Data System (ADS)
Chesi, Stefano; Coish, W. A.
2015-06-01
We have theoretically analyzed coherent nuclear-spin dynamics induced by electron transport through a quantum-dot spin valve. The hyperfine interaction between electron and nuclear spins in a quantum dot allows for the transfer of angular momentum from spin-polarized electrons injected from ferromagnetic or half-metal leads to the nuclear spin system under a finite voltage bias. Accounting for a local nuclear-spin dephasing process prevents the system from becoming stuck in collective dark states, allowing a large nuclear polarization to be built up in the long-time limit. After reaching a steady state, reversing the voltage bias induces a transient current response as the nuclear polarization is reversed. Long-range nuclear-spin coherence leads to a strong enhancement of spin-flip transition rates (by an amount proportional to the number of nuclear spins) and is revealed by an intense current burst, analogous to superradiant light emission. The crossover to a regime with incoherent spin flips occurs on a relatively long-time scale, on the order of the single-nuclear-spin dephasing time, which can be much longer than the time scale for the superradiant current burst. This conclusion is confirmed through a general master equation. For the two limiting regimes (coherent/incoherent spin flips), the general master equation recovers our simpler treatment based on rate equations, but is also applicable at intermediate dephasing. Throughout this work, we assume uniform hyperfine couplings, which yield the strongest coherent enhancement. We propose realistic strategies, based on isotopic modulation and wave-function engineering in core-shell nanowires, to realize this analytically solvable "box-model" of hyperfine couplings.
Knight shift and nuclear spin relaxation in Fe/n -GaAs heterostructures
NASA Astrophysics Data System (ADS)
Christie, K. D.; Geppert, C. C.; Patel, S. J.; Hu, Q. O.; Palmstrøm, C. J.; Crowell, P. A.
2015-10-01
We investigate the dynamically polarized nuclear spin system in Fe/n -GaAs heterostructures using the response of the electron-spin system to nuclear magnetic resonance (NMR) in lateral spin-valve devices. The hyperfine interaction is known to act more strongly on donor-bound electron states than on those in the conduction band. We provide a quantitative model of the temperature dependence of the occupation of donor sites. With this model we calculate the ratios of the hyperfine and quadrupolar nuclear relaxation rates of each isotope. For all temperatures measured, quadrupolar relaxation limits the spatial extent of nuclear spin polarization to within a Bohr radius of the donor sites and is directly responsible for the isotope dependence of the measured NMR signal amplitude. The hyperfine interaction is also responsible for the 2 kHz Knight shift of the nuclear resonance frequency that is measured as a function of the electron-spin accumulation. The Knight shift is shown to provide a measurement of the electron-spin polarization that agrees qualitatively with standard spin transport measurements.
NASA Astrophysics Data System (ADS)
Akiba, K.; Kanasugi, S.; Yuge, T.; Nagase, K.; Hirayama, Y.
2015-07-01
We study nuclear spin polarization in the quantum Hall regime through the optically pumped electron spin polarization in the lowest Landau level. The nuclear spin polarization is measured as a nuclear magnetic field BN by means of the sensitive resistive detection. We find the dependence of BN on the filling factor nonmonotonic. The comprehensive measurements of BN with the help of the circularly polarized photoluminescence measurements indicate the participation of the photoexcited complexes, i.e., the exciton and trion (charged exciton), in nuclear spin polarization. On the basis of a novel estimation method of the equilibrium electron spin polarization, we analyze the experimental data and conclude that the filling factor dependence of BN is understood by the effect of electron spin polarization through excitons and trions.
Akiba, K; Kanasugi, S; Yuge, T; Nagase, K; Hirayama, Y
2015-07-10
We study nuclear spin polarization in the quantum Hall regime through the optically pumped electron spin polarization in the lowest Landau level. The nuclear spin polarization is measured as a nuclear magnetic field B(N) by means of the sensitive resistive detection. We find the dependence of B(N) on the filling factor nonmonotonic. The comprehensive measurements of B(N) with the help of the circularly polarized photoluminescence measurements indicate the participation of the photoexcited complexes, i.e., the exciton and trion (charged exciton), in nuclear spin polarization. On the basis of a novel estimation method of the equilibrium electron spin polarization, we analyze the experimental data and conclude that the filling factor dependence of B(N) is understood by the effect of electron spin polarization through excitons and trions. PMID:26207494
Multipulse operation and optical detection of nuclear spin coherence in a GaAs/AlGaAs quantum well.
Kondo, Y; Ono, M; Matsuzaka, S; Morita, K; Sanada, H; Ohno, Y; Ohno, H
2008-11-14
We demonstrate manipulation of nuclear spin coherence in a GaAs/AlGaAs quantum well by optically detected nuclear magnetic resonance (NMR). A phase shift of the Larmor precession of photoexcited electron spins is detected to read out the hyperfine-coupled nuclear spin polarization. Multipulse NMR sequences are generated to control the population and examine the phase coherence in quadrupolar-split spin-3/2 75As nuclei. The phase coherence among the multilevel nuclear spin states is addressed by application of pulse sequences that are used in quantum gate operations. PMID:19113379
NASA Astrophysics Data System (ADS)
Jameson, C. J.; Jameson, A. K.; Buchi, K.
1986-07-01
Nuclear spin-lattice relaxation times have been measured for C-13 in (C-13)(O-16) in pure CO gas and in CO in Ar, Kr, Xe, N2, O2, HCl, CH4, SF6 gases as a function of temperature. The experimental procedure is described, and typical data for C-13 in pure CO at several temperatures are shown along with the temperature dependence of C-13 in (C13)(O-16) in various gases. The relaxation is completely dominated by the spin-rotation mechanism, so that empirical values of the cross sections for the CO rotational angular momentum transfer are obtained as a function of temperature.
Description of ^{158}Er at Ultrahigh Spin in Nuclear Density Functional Theory
Afanasjev, A. V.; Nazarewicz, Witold
2012-01-01
Rotational bands in 158Er at ultrahigh spin have been studied in the framework of relativistic and nonrelativistic nuclear density-functional theories. Consistent results are obtained across the theoretical models used but some puzzles remain when confronted with experiment. Namely, the many-body configurations which provide good description of experimental transition quadrupole moments and dynamic moments of inertia require substantial increase of the spins of observed bands as compared with experimental estimates, which are still subject to large uncertainties. If, however, the theoretical spin assignments turned out to be correct, experimental band 1 in 158Er would be the highest spin structure ever observed.
Search for electric dipole moment in 129Xe atom using active nuclear spin maser
NASA Astrophysics Data System (ADS)
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
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.
Classical nature of nuclear spin noise near clock transitions of Bi donors in silicon
NASA Astrophysics Data System (ADS)
Ma, Wen-Long; Wolfowicz, Gary; Li, Shu-Shen; Morton, John J. L.; Liu, Ren-Bao
2015-10-01
Whether a quantum bath can be approximated as classical Gaussian noise is a fundamental issue in central spin decoherence and also of practical importance in designing noise-resilient quantum control. Spin qubits based on bismuth donors in silicon have tunable interactions with nuclear spin baths and are first-order insensitive to magnetic noise at so-called clock transitions (CTs). This system is therefore ideal for studying the quantum/classical Gaussian nature of nuclear spin baths since the qubit-bath interaction strength determines the back-action on the baths and hence the adequacy of a Gaussian noise model. We develop a Gaussian noise model with noise correlations determined by quantum calculations and compare the classical noise approximation to the full quantum bath theory. We experimentally test our model through a dynamical decoupling sequence of up to 128 pulses, finding good agreement with simulations and measuring electron spin coherence times approaching 1 s—notably using natural silicon. Our theoretical and experimental study demonstrates that the noise from a nuclear spin bath is analogous to classical Gaussian noise if the back-action of the qubit on the bath is small compared to the internal bath dynamics, as is the case close to CTs. However, far from the CTs, the back-action of the central spin on the bath is such that the quantum model is required to accurately model spin decoherence.
Hayashi, Hiroshi; Itoh, Kohei M.; Vlasenko, Leonid S.
2008-10-15
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.
NASA Astrophysics Data System (ADS)
Berec, V.
2016-02-01
We study the coupling and control adaptation of a hybrid electron-nuclear spin system using the laser mediated proton beam in MeV energy regime. The asymmetric control mechanism is based on exact optimization of both: the measure of exchange interaction and anisotropy of the hyperfine interaction induced in the resonance with optimal channeled protons (CP) superfocused field, allowing manipulation over arbitrary localized spatial centers while addressing only the electron spin. Using highly precise and coherent proton channeling regime we have obtained efficient pulse shaping separator technique aimed for spatio-temporal engineering of quantum states, introducing a method for control of nuclear spins, which are coupled via anisotropic hyperfine interactions in isolated electron spin manifold, without radio wave (RW) pulses. The presented method can be efficiently implemented in synchronized spin networks with the purpose to facilitate preservation and efficient transfer of experimentally observed quantum particle states, contributing to the overall background noise reduction.
Adelnia, Fatemeh; Lascialfari, Alessandro; Mariani, Manuel; Ammannato, Luca; Caneschi, Andrea; Rovai, Donella; Winpenny, Richard; Timco, Grigore; Corti, Maurizio Borsa, Ferdinando
2015-05-07
We present the room temperature proton nuclear magnetic resonance (NMR) nuclear spin-lattice relaxation rate (NSLR) results in two 1D spin chains: the Heisenberg antiferromagnetic (AFM) Eu(hfac){sub 3}NITEt and the magnetically frustrated Gd(hfac){sub 3}NITEt. The NSLR as a function of external magnetic field can be interpreted very well in terms of high temperature spin dynamics dominated by a long time persistence of the decay of the two-spin correlation function due to the conservation of the total spin value for isotropic Heisenberg chains. The high temperature spin dynamics are also investigated in Heisenberg AFM molecular rings. In both Cr{sub 8} closed ring and in Cr{sub 7}Cd and Cr{sub 8}Zn open rings, i.e., model systems for a finite spin segment, an enhancement of the low frequency spectral density is found consistent with spin diffusion but the high cut-off frequency due to intermolecular anisotropic interactions prevents a detailed analysis of the spin diffusion regime.
NASA Astrophysics Data System (ADS)
Abolfath, Ramin M.; Trojnar, Anna; Roostaei, Bahman; Brabec, Thomas; Hawrylak, Pawel
2013-06-01
Dynamical magnetic and nuclear polarization in complex spin systems is discussed on the example of transfer of spin from exciton to the central spin of magnetic impurity in a quantum dot in the presence of a finite number of nuclear spins. The exciton is described in terms of electron and heavy-hole spins interacting via exchange interaction with magnetic impurity, via hyperfine interaction with a finite number of nuclear spins and via dipole interaction with photons. The time evolution of the exciton, magnetic impurity and nuclear spins is calculated exactly between quantum jumps corresponding to exciton radiative recombination. The collapse of the wavefunction and the refilling of the quantum dot with a new spin-polarized exciton is shown to lead to the build up of magnetization of the magnetic impurity as well as nuclear spin polarization. The competition between electron spin transfer to magnetic impurity and to nuclear spins simultaneous with the creation of dark excitons is elucidated. The technique presented here opens up the possibility of studying optically induced dynamical magnetic and nuclear polarization in complex spin systems.
Nuclear spin resonance of (129)Xe doped with O(2).
McNabb, J W; Balakishiyeva, D N; Honig, A
2007-10-01
Spin-lattice relaxation of (129)Xe nuclei in solid natural xenon has been investigated in detail over a large range of paramagnetic O(2) impurity concentrations. Direct measurements of the ground state magnetic properties of the O(2) are difficult because the ESR (electron spin resonance) lines of O(2) are rather unstructured, but NMR measurements in the liquid helium temperature region (1.4-4 K) are very sensitive to the effective magnetic moments associated with the spin 1 Zeeman levels of the O(2) molecules and to the O(2) magnetic relaxation. From these measurements, the value of the D[Sz(2)-(1/3)S(2)] spin-Hamiltonian term of the triplet spin ground state of O(2) can be determined. The temperature and magnetic field dependence of the measured paramagnetic O(2)-induced excess line width of the (129)Xe NMR signal agree well with the theoretical model with the spin-Hamiltonian D=0.19 meV (2.3 K), and with the reasonable assumption that the E[S(x)(2)-S(y)(2)] spin-Hamiltonian term is close to 0 meV. An anomalous temperature dependence between 1.4 K and 4.2K of the (129)Xe spin-lattice relaxation rate, T(1n)(-1)(T), is also accounted for by our model. Using an independent determination of the true O(2) concentration in the Xe-O(2) solid, the effective spin lattice relaxation time (which will be seen to be transition dependent) of the O(2) at 2.3 K and 0.96 T is determined to be approximately 1.4 x 10(-8)s. The experimental results, taken together with the relaxation model, suggest routes for bringing highly spin-polarized (129)Xe from the low temperature condensed phase to higher temperatures without excessive depolarization. PMID:17689279
Strongly polarizing weakly coupled 13C nuclear spins with optically pumped nitrogen-vacancy center
Wang, Ping; Liu, Bao; Yang, Wen
2015-01-01
Enhancing the polarization of nuclear spins surrounding the nitrogen-vacancy (NV) center in diamond has recently attracted widespread attention due to its various applications. Here we present an analytical formula that not only provides a clear physical picture for the recently observed polarization reversal of strongly coupled13C nuclei over a narrow range of magnetic field [H. J. Wang et al., Nat. Commun. 4, 1940 (2013)], but also demonstrates the possibility to strongly polarize weakly coupled13C nuclei. This allows sensitive magnetic field control of the 13C nuclear spin polarization for NMR applications and significant suppression of the 13C nuclear spin noise to prolong the NV spin coherence time. PMID:26521962
Testing for parity violation in nuclei using spin density matrices for nuclear density functionals
NASA Astrophysics Data System (ADS)
Barrett, B. R.; Giraud, B. G.
2015-06-01
The spin density matrix (SDM) used in atomic and molecular physics is revisited for nuclear physics, in the context of the radial density functional theory. The vector part of the SDM defines a ‘hedgehog’ situation, which exists only if nuclear states contain some amount of parity violation. A toy model is given as an illustrative example.
Quadrupolar effects on nuclear spins of neutral arsenic donors in silicon
NASA Astrophysics Data System (ADS)
Franke, David P.; Pflüger, Moritz P. D.; Mortemousque, Pierre-André; Itoh, Kohei M.; Brandt, Martin S.
2016-04-01
We present electrically detected electron nuclear double resonance measurements of the nuclear spins of ionized and neutral arsenic donors in strained silicon. In addition to a reduction of the hyperfine coupling, we find significant quadrupole interactions of the nuclear spin of the neutral donors of the order of 10 kHz. By comparing these to the quadrupole shifts due to crystal fields measured for the ionized donors, we identify the effect of the additional electron on the electric field gradient at the nucleus. This extra component is expected to be caused by the coupling to electric field gradients created due to changes in the electron wave function under strain.
Nuclear spin-spin coupling anisotropy in the van der Waals-bonded 129Xe dimer.
Jokisaari, Jukka; Vaara, Juha
2013-07-21
The spin-spin coupling constant, J, in the van der Waals-bonded (129)Xe-(129)Xe dimer cannot be determined experimentally because of the magnetic equivalence of the two nuclei. In contrast, the anisotropy of the coupling tensor, ΔJ, can be obtained from the so called effective dipole-dipole coupling determined in a solid state inclusion compound whose cages accommodate two xenon atoms. For the determination of the experimental ΔJ((129)Xe, (129)Xe) we exploited the data reported earlier in this journal. [D. H. Brouwer et al., Phys. Chem. Chem. Phys., 2007, 9, 1093.] The experimental value and the value obtained from relativistic first-principles computation are in perfect agreement. To the best of our knowledge this is the first investigation of spin-spin coupling anisotropy in a van der Waals-bonded system. PMID:23743998
Structure determination of individual electron-nuclear spin complexes in a solid-state matrix
NASA Astrophysics Data System (ADS)
Laraoui, Abdelghani; Pagliero, Daniela; Meriles, Carlos
2015-03-01
A spin-based quantum computer will store and process information via ``spin complexes'' formed by a small number of interacting electronic and nuclear spins within a solid-state host. Unlike present electronic circuits, differences in the atomic composition and local geometry make each of these spin clusters distinct from the rest. Integration of these units into a working network thus builds on our ability to determine the cluster atomic structure, a problem we tackle herein with the aid of a magnetic resonance protocol. Using the nitrogen-vacancy (NV) center in diamond as a model system, we show analytically and numerically that the spatial coordinates of weakly coupled 13C spins can be determined by selectively transferring and retrieving spin polarization. The technique's spatial resolution can reach up to 0.1 nm, limited by the NV spin coherence lifetime. No external magnetic field gradient is required, which makes this imaging scheme applicable to NV-13C complexes buried deep inside the crystal host. Further, this approach can be adapted to nuclear spins other than 13C, and thus applied to the characterization of individual molecules anchored to the diamond surface.
Spin-orbit interaction in relativistic nuclear structure models
NASA Astrophysics Data System (ADS)
Ebran, J.-P.; Mutschler, A.; Khan, E.; Vretenar, D.
2016-08-01
Relativistic self-consistent mean-field (SCMF) models naturally account for the coupling of the nucleon spin to its orbital motion, whereas nonrelativistic SCMF methods necessitate a phenomenological ansatz for the effective spin-orbit potential. Recent experimental studies aim to explore the isospin properties of the effective spin-orbit interaction in nuclei. SCMF models are very useful in the interpretation of the corresponding data; however, standard relativistic mean-field and nonrelativistic Hartree-Fock models use effective spin-orbit potentials with different isovector properties, mainly because exchange contributions are not treated explicitly in the former. The impact of exchange terms on the effective spin-orbit potential in relativistic mean-field models is analyzed, and it is shown that it leads to an isovector structure similar to the one used in standard nonrelativistic Hartree-Fock models. Data on the isospin dependence of spin-orbit splittings in spherical nuclei could be used to constrain the isovector-scalar channel of relativistic mean-field models. The reproduction of the empirical kink in the isotope shifts of even Pb nuclei by relativistic effective interactions points to the occurrence of pseudospin symmetry in the single-neutron spectra in these nuclei.
Separation and conversion dynamics of nuclear-spin isomers of gaseous methanol
Sun, Zhen-Dong; Ge, Meihua; Zheng, Yujun
2015-01-01
All symmetrical molecules with non-zero nuclear spin exist in nature as nuclear-spin isomers (NSIs). However, owing to the lack of experimental information, knowledge is rare about interconversions of NSIs of gaseous molecules with torsional symmetry. Here we report our separation and conversion observations on NSI-torsion-specific transition systems of gaseous methanol from a light-induced drift experiment involving partially spatial separation of the ortho and para isomers. We find that vibrationally excited molecules of the methanol spin isomer have a smaller collision cross-section than their ground-state counterparts. Interconversion of the enriched ortho isomer with the para isomer, which is generally considered improbable, has been quantitatively studied by sensitive detections of the spectral intensities. Rather counterintuitively, this reveals that the interconversion is inhibited with increasing pressure. Our results suggest that the spin conversion mechanism in methanol is via a quantum relaxation process with the quantum Zeno effect induced by molecular collisions. PMID:25880882
Probing an NV Center's Nuclear Spin Environment with Coherent Population Trapping
NASA Astrophysics Data System (ADS)
Levonian, David; Goldman, Michael; Singh, Swati; Markham, Matthew; Twitchen, Daniel; Lukin, Mikhail
2016-05-01
Nitrogen-vacancy (NV) centers in diamond have emerged as a versatile atom-like system, finding diverse applications in metrology and quantum information science, but interaction between the NV center's electronic spin and its nuclear spin environment represent a major source of decoherence. We use optical techniques to monitor and control the nuclear bath surrounding an NV center. Specifically, we create an optical Λ-system using the | +/- 1 > components of the NV center's spin-triplet ground state. When the Zeeman splitting between the two states is equal to the two-photon detuning between the lasers, population is trapped in the resulting dark state. Measuring the rate at which the NV center escapes from the dark state therefore gives information on how spin bath dynamics change the effective magnetic field experienced by the NV center. By monitoring statistics of the emitted photons, we plan to probe non-equilibrium dynamics of the bath.
Separation and conversion dynamics of nuclear-spin isomers of gaseous methanol
NASA Astrophysics Data System (ADS)
Sun, Zhen-Dong; Ge, Meihua; Zheng, Yujun
2015-04-01
All symmetrical molecules with non-zero nuclear spin exist in nature as nuclear-spin isomers (NSIs). However, owing to the lack of experimental information, knowledge is rare about interconversions of NSIs of gaseous molecules with torsional symmetry. Here we report our separation and conversion observations on NSI-torsion-specific transition systems of gaseous methanol from a light-induced drift experiment involving partially spatial separation of the ortho and para isomers. We find that vibrationally excited molecules of the methanol spin isomer have a smaller collision cross-section than their ground-state counterparts. Interconversion of the enriched ortho isomer with the para isomer, which is generally considered improbable, has been quantitatively studied by sensitive detections of the spectral intensities. Rather counterintuitively, this reveals that the interconversion is inhibited with increasing pressure. Our results suggest that the spin conversion mechanism in methanol is via a quantum relaxation process with the quantum Zeno effect induced by molecular collisions.
Mance, Deni; Baldus, Marc; Gast, Peter; Huber, Martina; Ivanov, Konstantin L.
2015-06-21
We develop a theoretical description of Dynamic Nuclear Polarization (DNP) in solids under Magic Angle Spinning (MAS) to describe the magnetic field dependence of the DNP effect. The treatment is based on an efficient scheme for numerical solution of the Liouville-von Neumann equation, which explicitly takes into account the variation of magnetic interactions during the sample spinning. The dependence of the cross-effect MAS-DNP on various parameters, such as the hyperfine interaction, electron-electron dipolar interaction, microwave field strength, and electron spin relaxation rates, is analyzed. Electron spin relaxation rates are determined by electron paramagnetic resonance measurements, and calculations are compared to experimental data. Our results suggest that the observed nuclear magnetic resonance signal enhancements provided by MAS-DNP can be explained by discriminating between “bulk” and “core” nuclei and by taking into account the slow DNP build-up rate for the bulk nuclei.
NASA Astrophysics Data System (ADS)
Mance, Deni; Gast, Peter; Huber, Martina; Baldus, Marc; Ivanov, Konstantin L.
2015-06-01
We develop a theoretical description of Dynamic Nuclear Polarization (DNP) in solids under Magic Angle Spinning (MAS) to describe the magnetic field dependence of the DNP effect. The treatment is based on an efficient scheme for numerical solution of the Liouville-von Neumann equation, which explicitly takes into account the variation of magnetic interactions during the sample spinning. The dependence of the cross-effect MAS-DNP on various parameters, such as the hyperfine interaction, electron-electron dipolar interaction, microwave field strength, and electron spin relaxation rates, is analyzed. Electron spin relaxation rates are determined by electron paramagnetic resonance measurements, and calculations are compared to experimental data. Our results suggest that the observed nuclear magnetic resonance signal enhancements provided by MAS-DNP can be explained by discriminating between "bulk" and "core" nuclei and by taking into account the slow DNP build-up rate for the bulk nuclei.
Coherent manipulation of an ensemble of nuclear spins in diamond for high precision rotation sensing
NASA Astrophysics Data System (ADS)
Jaskula, Jean-Christophe; Saha, Kasturi; Ajoy, Ashok; Cappellaro, Paola
2016-05-01
Gyroscopes find wide applications in everyday life from navigation and inertial sensing to rotation sensors in hand-held devices and automobiles. Current devices, based on either atomic or solid-state systems, impose a choice between long-time stability and high sensitivity in a miniaturized system. We are building a solid-state spin gyroscope associated with the Nitrogen-Vacancy (NV) centers in diamond take advantage of the efficient optical initialization and measurement offered by the NV electronic spin and the stability and long coherence time of the nuclear spin, which is preserved even at high defect density. In addition, we also investigate electro-magnetic noise monitoring and feedback schemes based on the coupling between the NV electronic and nuclear spin to achieve higher stability.
Thurber, Kent R. Tycko, Robert
2014-05-14
We report solid state {sup 13}C and {sup 1}H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, {sup 1}H and cross-polarized {sup 13}C NMR signals from {sup 15}N,{sup 13}C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T{sub 1e} is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations.
Thurber, Kent R.; Tycko, Robert
2014-01-01
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. PMID:24832263
Nuclear states and shapes at high spin. [Good review
Diamond, R.M.
1980-08-01
As angular momentum is added to a nucleus, the balance of forces acting upon it to determine its shape, moment of inertia, mode of rotation, and type of level structure may undergo a series of changes. At relatively low spins a deformed nucleus will rotate collectively, and one may see the effect of Coriolis antipairing in gradually increasing the moment of inertia. Around spin 12 to 16 h-bar there may be an abrupt change (backbending) when a pair of high-j nucleons unpairs and the nucleons align with the axis of rotation; this process allows the nucleus to slow its collective rotation. This process, the start of a sharing of angular momentum between single-particle motion and the collective rotation, gives a lower total energy and corresponds to a change toward triaxiality in the shape of the nucleus. At much higher spins discrete ..gamma..-ray transitions can no longer be observed. This is the regime of continuum spectra; all the information on these high-spin states (to 65 h-bar) is contained in these continuum cascades. Knowledge is accumulating on how to study these spectra, experimentally and theoretically, and new techniques offer promise of revealing a great deal of information about the shapes and properties of very high spin states. 71 references, 34 figures.
Mechanism for nuclear and electron spin excitation by radio frequency current
NASA Astrophysics Data System (ADS)
Müllegger, Stefan; Rauls, Eva; Gerstmann, Uwe; Tebi, Stefano; Serrano, Giulia; Wiespointner-Baumgarthuber, Stefan; Schmidt, Wolf Gero; Koch, Reinhold
2015-12-01
Recent radio frequency scanning tunneling spectroscopy (rf-STS) experiments have demonstrated nuclear and electron spin excitations up to ±12 ℏ in a single molecular spin quantum dot (qudot). Despite the profound experimental evidence, the observed independence of the well-established dipole selection rules is not described by existing theory of magnetic resonance—pointing to a new excitation mechanism. Here we solve the puzzle of the underlying mechanism by discussing the relevant mechanistic steps. At the heart of the mechanism, periodic transient charging and electric polarization due to the rf-modulated tunneling process cause a periodic asymmetric deformation of the adsorbed qudot, enabling efficient spin transitions via spin-phonon-like coupling. The mechanism has general relevance for a broad variety of different spin qudots exhibiting internal mechanical degrees of freedom (organic molecules, doped semiconductor qudots, nanocrystals, etc.).
Probing the Nuclear Spin-Lattice Relaxation Time at the Nanoscale
NASA Astrophysics Data System (ADS)
Wagenaar, J. J. T.; den Haan, A. M. J.; de Voogd, J. M.; Bossoni, L.; de Jong, T. A.; de Wit, M.; Bastiaans, K. M.; Thoen, D. J.; Endo, A.; Klapwijk, T. M.; Zaanen, J.; Oosterkamp, T. H.
2016-07-01
Nuclear spin-lattice relaxation times are measured on copper using magnetic-resonance force microscopy performed at temperatures down to 42 mK. The low temperature is verified by comparison with the Korringa relation. Measuring spin-lattice relaxation times locally at very low temperatures opens up the possibility to measure the magnetic properties of inhomogeneous electron systems realized in oxide interfaces, topological insulators, and other strongly correlated electron systems such as high-Tc superconductors.
Hovav, Yonatan; Feintuch, Akiva; Vega, Shimon
2013-01-01
Dynamic nuclear polarization is a method which allows for a dramatic increase of the NMR signals due to polarization transfer between electrons and their neighboring nuclei, via microwave irradiation. These experiments have become popular in recent years due to the ability to create hyper-polarized chemically and biologically relevant molecules, in frozen glass forming mixtures containing free radicals. Three mechanisms have been proposed for the polarization transfer between electrons and their surrounding nuclei in such non-conducting samples: the solid effect and cross effect mechanisms, which are based on quantum mechanics and relaxation on small spin systems, and thermal mixing, which originates from the thermodynamic macroscopic notion of spin temperature. We have recently introduced a spin model, which is based on the density matrix formalism and includes relaxation, and applied it to study the solid effect and cross effect mechanisms on small spin systems. In this publication we use the same model to describe the thermal mixing mechanism, and the creation of spin temperature. This is obtained without relying on the spin temperature formalism. Simulations of small model systems are used on systems with homogeneously and inhomogeneously broadened EPR lines. For the case of a homogeneously broadened line we show that the nuclear enhancement results from the thermal mixing and solid effect mechanisms, and that spin temperatures are created in the system. In the inhomogeneous case the enhancements are attributed to the solid effect and cross effect mechanisms, but not thermal mixing. PMID:23160533
High-fidelity transfer and storage of photon states in a single nuclear spin
NASA Astrophysics Data System (ADS)
Yang, Sen; Wang, Ya; Rao, D. D. Bhaktavatsala; Hien Tran, Thai; Momenzadeh, Ali S.; Markham, M.; Twitchen, D. J.; Wang, Ping; Yang, Wen; Stöhr, Rainer; Neumann, Philipp; Kosaka, Hideo; Wrachtrup, Jörg
2016-08-01
Long-distance quantum communication requires photons and quantum nodes that comprise qubits for interaction with light and good memory capabilities, as well as processing qubits for the storage and manipulation of photons. Owing to the unavoidable photon losses, robust quantum communication over lossy transmission channels requires quantum repeater networks. A necessary and highly demanding prerequisite for these networks is the existence of quantum memories with long coherence times to reliably store the incident photon states. Here we demonstrate the high-fidelity (∼98%) coherent transfer of a photon polarization state to a single solid-state nuclear spin that has a coherence time of over 10 s. The storage process is achieved by coherently transferring the polarization state of a photon to an entangled electron–nuclear spin state of a nitrogen–vacancy centre in diamond. The nuclear spin-based optical quantum memory demonstrated here paves the way towards an absorption-based quantum repeater network.
Interaction of Strain and Nuclear Spins in Silicon: Quadrupolar Effects on Ionized Donors
NASA Astrophysics Data System (ADS)
Franke, David P.; Hrubesch, Florian M.; Künzl, Markus; Becker, Hans-Werner; Itoh, Kohei M.; Stutzmann, Martin; Hoehne, Felix; Dreher, Lukas; Brandt, Martin S.
2015-07-01
The nuclear spins of ionized donors in silicon have become an interesting quantum resource due to their very long coherence times. Their perfect isolation, however, comes at a price, since the absence of the donor electron makes the nuclear spin difficult to control. We demonstrate that the quadrupolar interaction allows us to effectively tune the nuclear magnetic resonance of ionized arsenic donors in silicon via strain and determine the two nonzero elements of the S tensor linking strain and electric field gradients in this material to S11=1.5 ×1022 V /m2 and S44=6 ×1022 V /m2 . We find a stronger benefit of dynamical decoupling on the coherence properties of transitions subject to first-order quadrupole shifts than on those subject to only second-order shifts and discuss applications of quadrupole physics including mechanical driving of magnetic resonance, cooling of mechanical resonators, and strain-mediated spin coupling.
Universal Long-Time Behavior of Nuclear Spin Decays in a Solid
NASA Astrophysics Data System (ADS)
Morgan, S. W.; Fine, B. V.; Saam, B.
2008-08-01
Magnetic resonance studies of nuclear spins in solids are exceptionally well suited to probe the limits of statistical physics. We report experimental results indicating that isolated macroscopic systems of interacting nuclear spins possess the following fundamental property: spin decays that start from different initial configurations quickly evolve towards the same long-time behavior. This long-time behavior is characterized by the shortest ballistic microscopic time scale of the system and therefore falls outside of the validity range for conventional approximations of statistical physics. We find that the nuclear free-induction decay and different solid echoes in hyperpolarized solid xenon all exhibit sinusoidally modulated exponential long-time behavior characterized by identical time constants. This universality was previously predicted on the basis of analogy with resonances in classical chaotic systems.
Siddall, T.H.
1982-01-07
A theory is developed for nuclear magnetic resonance spectra of A/sub 2/B/sub 2/ systems with nuclei of higher spin. It is assumed that all nuclei have the same spin value. Otherwise no arbitrary limit is set on the spin. Although the development is made for NMR it also has application to the magnetic properties of clusters of transition-metal ions.
NASA Astrophysics Data System (ADS)
Cywiński, Łukasz; Witzel, Wayne M.; Das Sarma, S.
2009-06-01
We investigate decoherence due to pure dephasing of a localized spin qubit interacting with a nuclear spin bath. Although in the limit of a very large magnetic field the only decoherence mechanism is spectral diffusion due to dipolar flip-flops of nuclear spins, with decreasing field the hyperfine-mediated interactions between the nuclear spins become important. We take advantage of their long-range nature and resum the leading terms in an 1/N expansion of the decoherence time-evolution function ( N , being the number of nuclear spins interacting appreciably with the electron spin, is large). For the case of the thermal uncorrelated bath we show that our theory is applicable down to low magnetic fields ( ˜10mT for a large dot with N=106 ) allowing for comparison with recent experiments in GaAs quantum dot spin qubits. Within this approach we calculate the free induction decay and spin echo decoherence in GaAs and InGaAs as a function of the number of the nuclei in the bath (i.e., the quantum dot size) and the magnetic field. Our theory for free induction decay in a narrowed nuclear bath is shown to agree with the exact solution for decoherence due to hyperfine-mediated interaction which can be obtained when all the nuclei-electron coupling constants are identical. For the spin echo evolution we show that the dominant decoherence process at low fields is due to interactions between nuclei having significantly different Zeeman energies (i.e., nuclei of As and two isotopes of Ga in GaAs), and we compare our results with recent measurements of spin echo signal of a single spin confined in a GaAs quantum dot. For the same set of parameters we perform calculations of decoherence under various dynamical decoupling pulse sequences and predict the effect of these sequences in low- B regime in GaAs.
Spin-exchange narrowing in a nuclear magnetic transverse oscillator
NASA Astrophysics Data System (ADS)
Korver, Anna; Thrasher, Daniel; Bulatowicz, Michael; Walker, Thad
2015-05-01
We demonstrate spin exchange narrowing in synchronously pumped Xe NMR. The Xe NMR is driven by spin exchange with Rb atoms whose polarization is square-wave modulated at the Xe NMR frequency. On resonance, the nuclei precess in phase with the Rb polarization. Off resonance, however, the spin-exchange fields from the Rb cause the Xe to develop a static orthogonal spin component. This induces broadening in the NMR line while also dramatically suppressing the phase shift between the precessing Rb and Xe polarizations. We can compensate for this effect by adding an oscillating magnetic field oriented along the optical pumping axis and 180 degrees out of phase with the Rb polarization. This narrows the NMR line width to approximately the T1 limit, and nearly restores the usual relationship between detuning and phase shift. These results suggest the possibility of using the alkali field with appropriate magnetic field feedback along the bias field direction to narrow the NMR linewidth below the usual T1 limit. Support by the NSF and Northrop Grumman Co.
Thurber, Kent R.; Tycko, Robert
2012-01-01
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. PMID:22938251
Thurber, Kent R; Tycko, Robert
2012-08-28
We present theoretical calculations of dynamic nuclear polarization (DNP) due to the cross effect in nuclear magnetic resonance under magic-angle spinning (MAS). Using a three-spin model (two electrons and one nucleus), cross effect DNP with MAS for electron spins with a large g-anisotropy can be seen as a series of spin transitions at avoided crossings of the energy levels, with varying degrees of adiabaticity. If the electron spin-lattice relaxation time T(1e) is large relative to the MAS rotation period, the cross effect can happen as two separate events: (i) partial saturation of one electron spin by the applied microwaves as one electron spin resonance (ESR) frequency crosses the microwave frequency and (ii) flip of all three spins, when the difference of the two ESR frequencies crosses the nuclear frequency, which transfers polarization to the nuclear spin if the two electron spins have different polarizations. In addition, adiabatic level crossings at which the two ESR frequencies become equal serve to maintain non-uniform saturation across the ESR line. We present analytical results based on the Landau-Zener theory of adiabatic transitions, as well as numerical quantum mechanical calculations for the evolution of the time-dependent three-spin system. These calculations provide insight into the dependence of cross effect DNP on various experimental parameters, including MAS frequency, microwave field strength, spin relaxation rates, hyperfine and electron-electron dipole coupling strengths, and the nature of the biradical dopants. PMID:22938251
Kim, Y H; Kaur, N; Atkins, B M; Dalal, N S; Takano, Y
2009-12-11
At a quantum critical point (QCP)--a zero-temperature singularity in which a line of continuous phase transition terminates--quantum fluctuations diverge in space and time, leading to exotic phenomena that can be observed at nonzero temperatures. Using a quantum antiferromagnet, we present calorimetric evidence that nuclear spins frozen in a high-temperature nonequilibrium state by temperature quenching are annealed by quantum fluctuations near the QCP. This phenomenon, with readily detectable heat release from the nuclear spins as they are annealed, serves as an excellent marker of a quantum critical region around the QCP and provides a probe of the dynamics of the divergent quantum fluctuations. PMID:20366226
NASA Astrophysics Data System (ADS)
Clevenson, Hannah; Chen, Edward H.; Dolde, Florian; Teale, Carson; Englund, Dirk; Braje, Danielle
2016-08-01
We report on detailed studies of electronic and nuclear spin states in the diamond-nitrogen-vacancy (NV) center under weak transverse magnetic fields. We numerically predict and experimentally verify a previously unobserved NV hyperfine level anticrossing (LAC) occurring at bias fields of tens of gauss—two orders of magnitude lower than previously reported LACs at ˜500 and ˜1000 G axial magnetic fields. We then discuss how the NV ground-state Hamiltonian can be manipulated in this regime to tailor the NV's sensitivity to environmental factors and to map into the nuclear spin state.
Nuclear-Spin-Independent Short-Range Three-Body Physics in Ultracold Atoms
Gross, Noam; Shotan, Zav; Khaykovich, Lev; Kokkelmans, Servaas
2010-09-03
We investigate three-body recombination loss across a Feshbach resonance in a gas of ultracold {sup 7}Li atoms prepared in the absolute ground state and perform a comparison with previously reported results of a different nuclear-spin state [N. Gross et al., Phys. Rev. Lett. 103, 163202 (2009)]. We extend the previously reported universality in three-body recombination loss across a Feshbach resonance to the absolute ground state. We show that the positions and widths of recombination minima and Efimov resonances are identical for both states which indicates that the short-range physics is nuclear-spin independent.
Controlling the Excited-State Dynamics of Nuclear Spin Isomers Using the Dynamic Stark Effect.
Waldl, Maria; Oppel, Markus; González, Leticia
2016-07-14
Stark control of chemical reactions uses intense laser pulses to distort the potential energy surfaces of a molecule, thus opening new chemical pathways. We use the concept of Stark shifts to convert a local minimum into a local maximum of the potential energy surface, triggering constructive and destructive wave-packet interferences, which then induce different dynamics on nuclear spin isomers in the electronically excited state of a quinodimethane derivative. Model quantum-dynamical simulations on reduced dimensionality using optimized ultrashort laser pulses demonstrate a difference of the excited-state dynamics of two sets of nuclear spin isomers, which ultimately can be used to discriminate between these isomers. PMID:26840424
NASA Astrophysics Data System (ADS)
Fong, C. F.; Ota, Y.; Harbord, E.; Iwamoto, S.; Arakawa, Y.
2016-03-01
Repeated injection of spin-polarized carriers in a quantum dot (QD) leads to the polarization of nuclear spins, a process known as dynamic nuclear spin polarization (DNP). Here, we report the observation of p-shell carrier assisted DNP in single QDs at zero external magnetic field. The nuclear field—measured by using the Overhauser shift of the singly charged exciton state of the QDs—continues to increase, even after the carrier population in the s-shell saturates. This is also accompanied by an abrupt increase in nuclear spin buildup time as p-shell emission overtakes that of the s shell. We attribute the observation to p-shell electrons strongly altering the nuclear spin dynamics in the QD, supported by numerical simulation results based on a rate equation model of coupling between electron and nuclear spin system. Dynamic nuclear spin polarization with p-shell carriers could open up avenues for further control to increase the degree of nuclear spin polarization in QDs.
NASA Astrophysics Data System (ADS)
Heisterkamp, F.; Greilich, A.; Zhukov, E. A.; Kirstein, E.; Kazimierczuk, T.; Korenev, V. L.; Yugova, I. A.; Yakovlev, D. R.; Pawlis, A.; Bayer, M.
2015-12-01
Optically induced nuclear spin polarization in a fluorine-doped ZnSe epilayer is studied by time-resolved Kerr rotation using resonant excitation of donor-bound excitons. Excitation with helicity-modulated laser pulses results in a transverse nuclear spin polarization, which is detected as a change of the Larmor precession frequency of the donor-bound electron spins. The frequency shift in dependence on the transverse magnetic field exhibits a pronounced dispersion-like shape with resonances at the fields of nuclear magnetic resonance of the constituent zinc and selenium isotopes. It is studied as a function of external parameters, particularly of constant and radio frequency external magnetic fields. The width of the resonance and its shape indicate a strong spatial inhomogeneity of the nuclear spin polarization in the vicinity of a fluorine donor. A mechanism of optically induced nuclear spin polarization is suggested based on the concept of resonant nuclear spin cooling driven by the inhomogeneous Knight field of the donor-bound electron.
Nuclear Spin Relaxation Characteristic of Submonolayer He Films in Nanochannels
NASA Astrophysics Data System (ADS)
Matsushita, Taku; Kawai, Ryosuke; Kuze, Atsushi; Hieda, Mitsunori; Wada, Nobuo
2014-04-01
In order to obtain information on dynamics of helium films in the nondegenerate fluid region, we have performed a pulsed-NMR experiment at 3.29 MHz on He films adsorbed in straight 2.4 nm channels of FSM silicates down to 0.54 K. In general, the spin-lattice and spin-spin relaxation times and were explained in terms of the two-dimensional Bloembergen-Purcell-Pound model for dipolar relaxation. Temperature dependences of in submonolayer He films show a minimum, indicating that the dipolar-field correlation time is about s. The temperature of the minimum monotonically lowers with increasing coverage, suggesting that He adatoms become more mobile at higher coverages. The low-dimensional property of He adatoms is observed as the separation of and above where . On the other hand, several features specific to films in the nanochannel geometry were also found. Especially, the temperature dependence of becomes very small just below and shows a shoulder at lower temperatures. This anomaly has not been observed in He adsorbed in wider pores or on flat surfaces, so that it is considered to be characteristic of He films confined in narrow channels with a diameter of a few nm.
Relativistic Force Field: Parametrization of (13)C-(1)H Nuclear Spin-Spin Coupling Constants.
Kutateladze, Andrei G; Mukhina, Olga A
2015-11-01
Previously, we reported a reliable DU8 method for natural bond orbital (NBO)-aided parametric scaling of Fermi contacts to achieve fast and accurate prediction of proton-proton spin-spin coupling constants (SSCC) in (1)H NMR. As sophisticated NMR experiments for precise measurements of carbon-proton SSCCs are becoming more user-friendly and broadly utilized by the organic chemistry community to guide and inform the process of structure determination of complex organic compounds, we have now developed a fast and accurate method for computing (13)C-(1)H SSCCs. Fermi contacts computed with the DU8 basis set are scaled using selected NBO parameters in conjunction with empirical scaling coefficients. The method is optimized for inexpensive B3LYP/6-31G(d) geometries. The parametric scaling is based on a carefully selected training set of 274 ((3)J), 193 ((2)J), and 143 ((1)J) experimental (13)C-(1)H spin-spin coupling constants reported in the literature. The DU8 basis set, optimized for computing Fermi contacts, which by design had evolved from optimization of a collection of inexpensive 3-21G*, 4-21G, and 6-31G(d) bases, offers very short computational (wall) times even for relatively large organic molecules containing 15-20 carbon atoms. The most informative SSCCs for structure determination, i.e., (3)J, were computed with an accuracy of 0.41 Hz (rmsd). The new unified approach for computing (1)H-(1)H and (13)C-(1)H SSCCs is termed "DU8c". PMID:26414291
NMR Investigation of Optical Polarization of Nuclear Spins in GaAs
NASA Astrophysics Data System (ADS)
Paravastu, Anant; Hayes, Sophia; Schwickert, Birgit; Reimer, Jeffrey; Dinh, Long; Balooch, Mehdi
2003-03-01
Light-induced nuclear spin alignments have been measured in GaAs as a function of photon energy, irradiation time, and sample temperature using NMR spectroscopy at 9.4 Tesla and 10 to 50 K. Significant optical enhancements were observed at a range of photon energies, starting just below the band gap and persisting through 100 meV above the gap. Irradiation above the band gap resulted in thermally activated NMR signal enhancements while sub band gap irradiation did not. Short and long irradiation time dependencies revealed insights into the nature of cross relaxation between electronic nuclear spins, contradicting mechanisms based on either localized electron-nuclear contact at defect sites or cross relaxation between nuclei and free electrons. We propose that the presence of a mobile or delocalized enabling electronic species characterized by a long electron-nuclear correlation time, such as an exciton, is necessary in any mechanism which explains the data.
Role of dual nuclear baths on spin blockade leakage current bistabilities.
Buddhiraju, Siddharth; Muralidharan, Bhaskaran
2014-12-01
Spin-blockaded electronic transport across a double quantum dot (DQD) system represents an important advancement in the area of spin-based quantum information. The basic mechanism underlying the blockade is the formation of a blocking triplet state. The bistability of the leakage current as a function of the applied magnetic field in this regime is believed to arise from the effect of nuclear Overhauser fields on spin-flip transitions between the blocking triplet and the conducting singlet states. The objective of this paper is to present the nuances of considering a two bath model on the experimentally observed current bistability by employing a self consistent simulation of the nuclear spin dynamics coupled with the electronic transport of the DQD set up. In doing so, we first discuss the important subtleties involved in the microscopic derivation of the hyperfine mediated spin flip rates. We then give insights as to how the differences between the two nuclear baths and the resulting difference Overhauser field affect the two-electron states of the DQD and their connection with the experimentally observed current hysteresis curve. PMID:25374371
Coupled nuclear spin relaxation and internal rotations in magnesium fluosilicate hexahydrate.
NASA Technical Reports Server (NTRS)
Utton, D. B.; Tsang, T.
1972-01-01
Both proton and fluorine nuclear spin-lattice relaxations have been studied by the 180- to 90-deg pulse method in magnesium fluosilicate hexahydrate at 25 and 13 MHz over the temperature range from 170 to 350 K. Observed nonexponential behavior of the nuclear magnetic relaxation is explained by internal rotations of the doubly charged negative fluosilicate ions and doubly charged positive magnesium hexahydrate ions.
Bordbar, G. H.; Bigdeli, M.
2008-01-15
In this paper, we calculate properties of the spin polarized asymmetrical nuclear matter and neutron star matter, using the lowest order constrained variational (LOCV) method with the AV{sub 18}, Reid93, UV{sub 14}, and AV{sub 14} potentials. According to our results, the spontaneous phase transition to a ferromagnetic state in the asymmetrical nuclear matter as well as neutron star matter do not occur.
Experimental search for EDM in diamagnetic atom 129Xe using active nuclear spin maser
NASA Astrophysics Data System (ADS)
Ichikawa, Yuichi; Sato, Tomoya; Ohtomo, Yuichi; Sakamoto, Yu; Kojima, Shuichiro; Funayama, Chikako; Hirao, Chika; Suzuki, Takahiro; Chikamori, Masatoshi; Hikota, Eri; Miyatake, Hirokazu; Nanao, Tsubasa; Suzuki, Kunifumi; Tsuchiya, Masato; Inoue, Takeshi; Furukawa, Takeshi; Yoshimi, Akihiko; Bidinosti, Christopher; Ino, Takashi; Ueno, Hideki; Matsuo, Yukari; Fukuyama, Takeshi; Asahi, Koichiro
2014-09-01
A permanent electric dipole moment (EDM) which directly means T-violation attracts much attention, because an unknown CP-violating phase which is necessary to understand the present matter-dominated Universe is expected to be probed by EDM. The present study aims at measuring the EDM in the diamagnetic atom 129Xe to a size of 10-28 ecm, stepping into a domain below the present upper limit by one order of magnitude. In the present experiment, we employ an active nuclear spin maser which has characteristics of the optical detection of the spin precession and the artificial production of the feedback field to sustain the spin precession over a long measurement duration. For the magnetometry in the measurement, a comagnetometer using 3He is incorporated to the spin maser system. In this presentation, the current status of our experiment will be given.
Coherent transfer of nuclear spin polarization in field-cycling NMR experiments
Pravdivtsev, Andrey N.; Yurkovskaya, Alexandra V.; Ivanov, Konstantin L.; Vieth, Hans-Martin
2013-12-28
Coherent polarization transfer effects in a coupled spin network have been studied over a wide field range. The transfer mechanism is based on exciting zero-quantum coherences between the nuclear spin states by means of non-adiabatic field jump from high to low magnetic field. Subsequent evolution of these coherences enables conversion of spin order in the system, which is monitored after field jump back to high field. Such processes are most efficient when the spin system passes through an avoided level crossing during the field variation. The polarization transfer effects have been demonstrated for N-acetyl histidine, which has five scalar coupled protons; the initial spin order has been prepared by applying RF-pulses at high magnetic field. The observed oscillatory transfer kinetics is taken as a clear indication of a coherent mechanism; level crossing effects have also been demonstrated. The experimental data are in very good agreement with the theoretical model of coherent polarization transfer. The method suggested is also valid for other types of initial polarization in the spin system, most notably, for spin hyperpolarization.
NASA Astrophysics Data System (ADS)
Bulatowicz, Michael; Larsen, Michael; Mirijanian, James; Fu, Changbo; Yan, Haiyang; Smith, Erick; Snow, Mike; Walker, Thad
2012-06-01
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.
Electric readout and storage concepts for electron and nuclear spin states in silicon
NASA Astrophysics Data System (ADS)
Boehme, Christoph
2011-10-01
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).
NASA Astrophysics Data System (ADS)
Natterer, Fabian Donat; Patthey, François; Brune, Harald
2014-03-01
The appeal of inelastic electron tunneling spectroscopy with the scanning tunneling microscope (STM) stems from its unmatched spatial resolution and the ability to measure the magnetic, electronic and vibrational properties of individual atoms and molecules. Rotational excitations of molecules could provide additional information of surface processes but have hitherto remained elusive. Here we demonstrate rotational excitation spectroscopy (RES) with the STM for hydrogen and its isotopes on graphene and hexagonal boron nitride. Since the Pauli principle imposes restrictions on the allowed rotational levels J for molecules with identical nuclei, a certain alignment of the nuclear spins entails a specific set of rotational levels. Conversely, measuring the rotational levels allows characterizing the molecular nuclear spin state. We measured excitation energies at 44 meV and 21 meV, corresponding to rotational transitions J = 0 --> 2 for hydrogen and deuterium. We thereby identify the nuclear spin isomers para-H2 and ortho-D2. For HD, we observe J = 0 --> 1 and J = 0 --> 2 transitions, as expected for heteronuclear diatomics. Our measurements demonstrate the potential of STM-RES in the study of nuclear spin states with unprecedented spatial resolution. We acknowledge funding from the Swiss National Science Foundation under Projects No. 140479 and No. 148891.
Nuclear Spin Dependent Chemistry of the Trihydrogen Cation in Diffuse Interstellar Clouds
NASA Astrophysics Data System (ADS)
Crabtree, Kyle
2015-05-01
The trihydrogen cation, H3+,long thought to be the species responsible for initiating ion-molecule chemistry in the interstellar medium, was first observed in interstellar clouds twenty years ago. Since its detection, this cation has been used to infer temperatures, densities, cloud sizes, and the local cosmic ray ionization rate. However, in diffuse molecular clouds the excitation temperature of its two nuclear spin modifications, ortho (I = 3 / 2) and para-H3+(I = 1 / 2) is found to differ markedly from the cloud kinetic temperature inferred from the spin modifications of molecular hydrogen (H2) in the same environment. A steady state analysis of the chemical kinetics of ortho and para-H3+suggests that the interplay of thermalizing collisions with H2 and nuclear spin dependent dissociative recombination with electrons may result in a nonthermal excitation temperature. Each of these processes is complex. Collisions between H3+and H2 must obey selection rules based on conservation of nuclear spin angular momentum, and the allowed spin conversion reactions, which proceed through the fluxional (H5+)* intermediate, each have different statistical weights and energetic requirements. Meanwhile, theoretical and experimental studies of H3+electron recombination carried out over the past 40 years have yielded rates that span 4 orders of magnitude in range. We will present experimental measurements of the nuclear spin dependence of the reactions of H3+with H2 and with electrons, as well as astronomical observations of H3+in diffuse molecular clouds and time-dependent chemical modeling of these environments. Astrochemical models incorporating the latest experimental data still do not satisfactorily explain the observed excitation temperature in diffuse molecular clouds, and point to the need for state-selective measurements of the H3+electron recombination rate.
Willans, Mathew J; Demko, Bryan A; Wasylishen, Roderick E
2006-06-21
A solid-state nuclear magnetic resonance and zeroth-order regular approximation density functional theory, ZORA-DFT, study of one-bond nuclear spin-spin coupling between group-14 nuclei and quadrupolar 35/37Cl nuclei in triphenyl group-14 chlorides, Ph3XCl (X = C, Si, Ge, Sn and Pb), is presented. This represents the first combined experimental and theoretical systematic study of spin-spin coupling involving spin-pairs containing quadrupolar nuclei. Solid-state NMR spectra have been acquired for all compounds in which X has a spin-1/2 isotope--13C, 29Si, [117/119]Sn and 207Pb-at applied magnetic fields of 4.70, 7.05 and 11.75 T. From simulations of these spectra, values describing the indirect spin-spin coupling tensor-the isotropic indirect spin-spin coupling constant, 1J(X, 35/37Cl)iso and the anisotropy of the J tensor, Delta1J(X, 35/37Cl)--have been determined for all but the lead-chlorine spin-pair. To better compare the indirect spin-spin coupling parameters between spin-pairs, 1J(iso) and Delta1J values were converted to their reduced coupling constants, 1K(iso) and Delta1K. From experiment, the sign of 1K(iso) was found to be negative while the sign of Delta1K is positive for all spin-pairs investigated. The magnitude of both 1K(iso) and Delta1K was found to increase as one moves down group-14. Theoretical values of the magnitude and sign of 1K(iso) and Delta1K were obtained from ZORA-DFT calculations and are in agreement with the available experimental data. From the calculations, the Fermi-contact mechanism was determined to provide the largest contribution to 1K(iso) for all spin-pairs while spin-dipolar and paramagnetic spin-orbit mechanisms make significant contributions to the anisotropy of K. The inclusion of relativistic effects was found to influence K(Sn,Cl) and K(Pb,Cl). PMID:16763706
NASA Astrophysics Data System (ADS)
Domínguez, F. D.; González, C. E.; Segnorile, H. H.; Zamar, R. C.
2016-02-01
We study the quantum adiabatic decoherence of a multispin array, coupled with an environment of harmonic phonons, in the framework of the theory of open quantum systems. We follow the basic formal guidelines of the well-known spin-boson model, since in this framework it is possible to derive the time dependence of the reduced density matrix in the adiabatic time scale, without resorting to coarse-graining procedures. However, instead of considering a set of uncoupled spins interacting individually with the boson field, the observed system in our model is a network of weakly interacting spin pairs; the bath corresponds to lattice phonons, and the system-environment interaction is generated by the variation of the dipole-dipole energy due to correlated shifts of the spin positions, produced by the phonons. We discuss the conditions that the model must meet in order to fit within the adiabatic regime. By identifying the coupling of the dipole-dipole spin interaction with the low-frequency acoustic modes as the source of decoherence, we calculate the decoherence function of the reduced spin density matrix in closed way, and estimate the decoherence rate of a typical element of the reduced density matrix in one- and three-dimensional models of the spin array. Using realistic values for the various parameters of the model we conclude that the dipole-phonon mechanism can be particularly efficient to degrade multispin coherences, when the number of active spins involved in a given coherence is high. The model provides insight into the microscopic irreversible spin dynamics involved in the buildup of quasiequilibrium states and in the coherence leakage during refocusing experiments in nuclear magnetic resonance of crystalline solids.
Advances and applications of dynamic-angle spinning nuclear magnetic resonance
Baltisberger, J.H.
1993-06-01
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.
Spin Noise Detection of Nuclear Hyperpolarization at 1.2 K
Pöschko, Maria Theresia; Vuichoud, Basile; Milani, Jonas; Bornet, Aurélien; Bechmann, Matthias; Bodenhausen, Geoffrey; Jannin, Sami; Müller, Norbert
2015-01-01
We report proton spin noise spectra of a hyperpolarized solid sample of commonly used “DNP (dynamic nuclear polarization) juice” containing TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine N-oxide) and irradiated by a microwave field at a temperature of 1.2 K in a magnetic field of 6.7 T. The line shapes of the spin noise power spectra are sensitive to the variation of the microwave irradiation frequency and change from dip to bump, when the electron Larmor frequency is crossed, which is shown to be in good accordance with theory by simulations. Small but significant deviations from these predictions are observed, which can be related to spin noise and radiation damping phenomena that have been reported in thermally polarized systems. The non-linear dependence of the spin noise integral on nuclear polarization provides a means to monitor hyperpolarization semi-quantitatively without any perturbation of the spin system by radio frequency irradiation. PMID:26477605
Spin Noise Detection of Nuclear Hyperpolarization at 1.2 K.
Pöschko, Maria Theresia; Vuichoud, Basile; Milani, Jonas; Bornet, Aurélien; Bechmann, Matthias; Bodenhausen, Geoffrey; Jannin, Sami; Müller, Norbert
2015-12-21
We report proton spin noise spectra of a hyperpolarized solid sample of commonly used "DNP (dynamic nuclear polarization) juice" containing TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine N-oxide) and irradiated by a microwave field at a temperature of 1.2 K in a magnetic field of 6.7 T. The line shapes of the spin noise power spectra are sensitive to the variation of the microwave irradiation frequency and change from dip to bump, when the electron Larmor frequency is crossed, which is shown to be in good accordance with theory by simulations. Small but significant deviations from these predictions are observed, which can be related to spin noise and radiation damping phenomena that have been reported in thermally polarized systems. The non-linear dependence of the spin noise integral on nuclear polarization provides a means to monitor hyperpolarization semi-quantitatively without any perturbation of the spin system by radio frequency irradiation. PMID:26477605
Shi, Junhui; Ikäläinen, Suvi; Vaara, Juha; Romalis, Michael V
2013-02-01
Nuclear spin optical rotation (NSOR) is a recently developed technique for detection of nuclear magnetic resonance via rotation of light polarization, instead of the usual long-range magnetic fields. NSOR signals depend on hyperfine interactions with virtual optical excitations, giving new information about the nuclear chemical environment. We use a multipass optical cell to perform the first precision measurements of NSOR signals for a range of organic liquids and find clear distinction between proton signals for different compounds, in agreement with our earlier theoretical predictions. Detailed first-principles quantum mechanical NSOR calculations are found to be in agreement with the measurements. PMID:26281737
Nuclear orientation of radon isotopes by spin-exchange optical pumping
Kitano, M.; Calaprice, F.P.; Pitt, M.L.; Clayhold, J.; Happer, W.; Kadar-Kallen, M.; Musolf, M.; Ulm, G.; Wendt, K.; Chupp, T.
1988-05-23
This paper reports the first demonstration of nuclear orientation of radon atoms. The method employed was spin exchange with potassium atoms polarized by optical pumping. The radon isotopes were produced at the ISOLDE isotope separator of CERN. The nuclear alignment of /sup 209/Rn and /sup 223/Rn has been measured by observation of ..gamma..-ray anisotropies and the magnetic dipole moment for /sup 209/Rn has been measured by the nuclear-magnetic-resonance method to be chemically bond..mu..chemically bond = 0.838 81(39)..mu../sub N/.
Natural reference for nuclear high-spin states
Rowley, Neil; Ollier, James; Simpson, John
2009-08-15
We suggest two new representations of the data on rotational nuclei. The first is reference-free and the second arises from a natural reference related to the variable moment of inertia model parameters of the ground-state band of the system. As such, neither representation contains any free parameters. By defining a 'configuration spin' we show how a new ground-state band reference can be applied. Its use allows a complete description of the changes associated with the first, and higher, band crossings. We apply these new representations to discuss the nature of the first band crossing along even-even isotopic chains in the erbium and osmium isotopes and to odd-even nuclei in the vicinity of {sup 158}Er.
Spin-orbit decomposition of ab initio nuclear wave functions
NASA Astrophysics Data System (ADS)
Johnson, Calvin W.
2015-03-01
Although the modern shell-model picture of atomic nuclei is built from single-particle orbits with good total angular momentum j , leading to j -j coupling, decades ago phenomenological models suggested that a simpler picture for 0 p -shell nuclides can be realized via coupling of the total spin S and total orbital angular momentum L . I revisit this idea with large-basis, no-core shell-model calculations using modern ab initio two-body interactions and dissect the resulting wave functions into their component L - and S -components. Remarkably, there is broad agreement with calculations using the phenomenological Cohen-Kurath forces, despite a gap of nearly 50 years and six orders of magnitude in basis dimensions. I suggest that L -S decomposition may be a useful tool for analyzing ab initio wave functions of light nuclei, for example, in the case of rotational bands.
NASA Astrophysics Data System (ADS)
Zhukov, E. A.; Greilich, A.; Yakovlev, D. R.; Kavokin, K. V.; Yugova, I. A.; Yugov, O. A.; Suter, D.; Karczewski, G.; Wojtowicz, T.; Kossut, J.; Petrov, V. V.; Dolgikh, Yu. K.; Pawlis, A.; Bayer, M.
2014-08-01
Resonant cooling of different nuclear isotopes manifested in optically induced nuclear magnetic resonances (NMR) is observed in n-doped CdTe/(Cd,Mg)Te and ZnSe/(Zn,Mg)Se quantum wells and for donor-bound electrons in ZnSe:F and GaAs epilayers. By time-resolved Kerr rotation used in the regime of resonant spin amplification, we can expand the range of magnetic fields where the effect can be observed up to nuclear Larmor frequencies of 170 kHz. The mechanism of the resonant cooling of the nuclear spin system is analyzed theoretically. The developed approach allows us to model the resonant spin amplification signals with NMR features.
Nuclear Spin Relaxation and Molecular Interactions of a Novel Triazolium-Based Ionic Liquid
Allen, Jesse J; Schneider, Yanika; Kail, Brian W; Luebke, David R; Nulwala, Hunaid; Damodaran, Krishnan
2013-04-11
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.
Atomic-scale nuclear spin imaging using quantum-assisted sensors in diamond
NASA Astrophysics Data System (ADS)
Ajoy, Ashok; Bissbort, Ulf; Liu, Yixiang; Marseglia, Luca; Saha, Kasturi; Cappellaro, Paola
2015-05-01
Recent developments in materials fabrication and coherent control have brought quantum magnetometers based on electronic spin defects in diamond close to single nuclear spin sensitivity. These quantum sensors have the potential to be a revolutionary tool in proteomics, thus helping drug discovery: They can overcome some of the challenges plaguing other experimental techniques (x-ray and NMR) and allow single protein reconstruction in their natural conditions. While the sensitivity of diamond-based magnetometers approaches the single nuclear spin level, the outstanding challenge is to resolve contributions arising from distinct nuclear spins in a dense sample and use the acquired signal to reconstruct their positions. This talk describes a strategy to boost the spatial resolution of NV-based magnetic resonance imaging, by combining the use of a quantum memory intrinsic to the NV system with Hamiltonian engineering by coherent quantum control. The proposed strategy promises to make diamond-based quantum sensors an invaluable technology for bioimaging, as they could achieve the reconstruction of biomolecules local structure without the need to crystallize them, to synthesize large ensembles or to alter their natural environment.
Dephasing of two-spin qubits due to their charge and nuclear environments
NASA Astrophysics Data System (ADS)
Ramon, Guy
2011-03-01
We consider dephasing of qubits encoded in the singlet and unpolarized triplet states of pairs of spins localized in biased double quantum dots. The charge environment is modeled by both two-center charge traps in the insulator (where electrons tunnel between the two centers), and single charge traps located near the gate electrodes and QPCs (where electrons charge and empty the trap). The couplings of these trapped charges to the qubits are calculated by considering their charge distributions within a multipole expansion. It is demonstrated that the summation over these random telegraph processes in mesoscopic devices results in non-Markovian and non-Gaussian noise. For the nuclear environment we consider hyperfine-induced electron-spin dephasing in a nuclear spin bath with narrowed distribution. Nuclear state preparation using dynamical polarization cycles was experimentally achieved recently, and it is also essential to enable X -rotations for two-spin qubits. Our analysis is performed for both free induction and echo signals. The scaling of these dephasing mechanisms with the number of qubits is also discussed. Supported by Research Corporation.
Employing Forbidden Transitions as Qubits in a Nuclear Spin-Free Chromium Complex.
Fataftah, Majed S; Zadrozny, Joseph M; Coste, Scott C; Graham, Michael J; Rogers, Dylan M; Freedman, Danna E
2016-02-01
The implementation of quantum computation (QC) would revolutionize scientific fields ranging from encryption to quantum simulation. One intuitive candidate for the smallest unit of a quantum computer, a qubit, is electronic spin. A prominent proposal for QC relies on high-spin magnetic molecules, where multiple transitions between the many MS levels are employed as qubits. Yet, over a decade after the original notion, the exploitation of multiple transitions within a single manifold for QC remains unrealized in these high-spin species due to the challenge of accessing forbidden transitions. To create a proof-of-concept system, we synthesized the novel nuclear spin-free complex [Cr(C3S5)3](3-) with precisely tuned zero-field splitting parameters that create two spectroscopically addressable transitions, with one being a forbidden transition. Pulsed electron paramagnetic resonance (EPR) measurements enabled the investigation of the coherent lifetimes (T2) and quantum control (Rabi oscillations) for two transitions, one allowed and one forbidden, within the S = (3)/2 spin manifold. This investigation represents a step forward in the development of high-spin species as a pathway to scalable QC systems within magnetic molecules. PMID:26739626
Wylie, Benjamin J; Dzikovski, Boris G; Pawsey, Shane; Caporini, Marc; Rosay, Melanie; Freed, Jack H; McDermott, Ann E
2015-04-01
We demonstrate that dynamic nuclear polarization of membrane proteins in lipid bilayers may be achieved using a novel polarizing agent: pairs of spin labels covalently bound to a protein of interest interacting at an intermolecular interaction surface. For gramicidin A, nitroxide tags attached to the N-terminal intermolecular interface region become proximal only when bimolecular channels forms in the membrane. We obtained signal enhancements of sixfold for the dimeric protein. The enhancement effect was comparable to that of a doubly tagged sample of gramicidin C, with intramolecular spin pairs. This approach could be a powerful and selective means for signal enhancement in membrane proteins, and for recognizing intermolecular interfaces. PMID:25828256
Nanoscale Nuclear Magnetic Resonance with a Nitrogen-Vacancy Spin Sensor
NASA Astrophysics Data System (ADS)
Mamin, H. J.; Kim, M.; Sherwood, M. H.; Rettner, C. T.; Ohno, K.; Awschalom, D. D.; Rugar, D.
2013-02-01
Extension of nuclear magnetic resonance (NMR) to nanoscale samples has been a longstanding challenge because of the insensitivity of conventional detection methods. We demonstrated the use of an individual, near-surface nitrogen-vacancy (NV) center in diamond as a sensor to detect proton NMR in an organic sample located external to the diamond. Using a combination of electron spin echoes and proton spin manipulation, we showed that the NV center senses the nanotesla field fluctuations from the protons, enabling both time-domain and spectroscopic NMR measurements on the nanometer scale.
Nuclear-spin diffusion in (NH4)2SnBr6
NASA Astrophysics Data System (ADS)
Punkkinen, M.; Ylinen, E. E.; Ingman, L. P.
1982-10-01
Nuclear-spin diffusion between the protons of the A and T species NH+4 ions in an (NH4)2SnBr6 single crystal is studied by the rf pulse sequence 90°-t1-90°180°-t2-90°. The shape of the induction signal after the third pulse approaches the equilibrium shape during the variable time t2 at a speed characterized by the spin-diffusion time constant TSD. TSD is longest for B-->0∥[111] and shortest for B-->0∥[100] below 30 K. It varies with temperature.
Gerlovin, I. Ya.; Cherbunin, R. V.; Ignatiev, I. V.; Kuznetsova, M. S.; Verbin, S. Yu.; Flisinski, K.; Bayer, M.; Reuter, D.; Wieck, A. D.; Yakovlev, D. R.
2013-12-04
The degree of circular polarization of photoluminescence of (In,Ga)As quantum dots as a function of magnetic field applied perpendicular to the optical axis (Hanle effect) is experimentally studied. The measurements have been performed at various regimes of the optical excitation modulation. The analysis of experimental data has been performed in the framework of a vector model of regular nuclear spin polarization and its fluctuations. The analysis allowed us to evaluate the magnitude of nuclear polarization and its dynamics at the experimental conditions used.
NASA Astrophysics Data System (ADS)
Waeber, A. M.; Hopkinson, M.; Farrer, I.; Ritchie, D. A.; Nilsson, J.; Stevenson, R. M.; Bennett, A. J.; Shields, A. J.; Burkard, G.; Tartakovskii, A. I.; Skolnick, M. S.; Chekhovich, E. A.
2016-07-01
One of the key challenges in spectroscopy is the inhomogeneous broadening that masks the homogeneous spectral lineshape and the underlying coherent dynamics. Techniques such as four-wave mixing and spectral hole-burning are used in optical spectroscopy, and spin-echo in nuclear magnetic resonance (NMR). However, the high-power pulses used in spin-echo and other sequences often create spurious dynamics obscuring the subtle spin correlations important for quantum technologies. Here we develop NMR techniques to probe the correlation times of the fluctuations in a nuclear spin bath of individual quantum dots, using frequency-comb excitation, allowing for the homogeneous NMR lineshapes to be measured without high-power pulses. We find nuclear spin correlation times exceeding one second in self-assembled InGaAs quantum dots--four orders of magnitude longer than in strain-free III-V semiconductors. This observed freezing of the nuclear spin fluctuations suggests ways of designing quantum dot spin qubits with a well-understood, highly stable nuclear spin bath.
High-pressure magic angle spinning nuclear magnetic resonance
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
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. Finally, 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.
High-pressure magic angle spinning nuclear magnetic resonance.
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
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
High-pressure magic angle spinning nuclear magnetic resonance
NASA Astrophysics Data System (ADS)
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
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 situ13C MAS NMR studies of mineral carbonation reaction intermediates and final products of forsterite (Mg 2SiO 4) reacted with supercritical CO 2 and H 2O at 150 bar and 50 °C are reported, with relevance to geological sequestration of carbon dioxide.
Optical and Nuclear Spin Spectroscopy in PRASEODYMIUM(3+):LANTHANUM Fluoride by Optical Pumping
NASA Astrophysics Data System (ADS)
Wald, Lawrence Leroy
A Stark Modulated Optical Pumping (SMOP) technique was used as a sensitive probe of optical hole-burning to study the effects of nuclear spin interactions in Pr ^{3+}:LaF_3. The results of two experiments are reported. In the first experiment, the SMOP technique is applied for optical detection of the NQR spectrum of the Pr^{3+} optical ground state. Frequency and linewidth variations of the Pr ^{3+} ground state hyperfine levels for different positions within the main ^3 H_4(Gamma1) -^1D_2(Gamma 1) inhomogeneous optical line and satellite transitions of Pr^{3+}:LaF _3 are observed. A linear increase in the broadening of the Pr^{3+} hyperfine transitions, without a shift of central frequency, is measured as the laser is tuned toward the wings of the inhomogeneous optical transition. The linear variation is attributed to electric quadrupole broadening caused by changes in local density of point defects across the Stark broadened optical transition. The optically detected NQR spectra of the satellite transitions associated with Pr ion pairs are shifted in frequency, and for most satellites are narrower in width than the NQR spectra found in the wings of the main inhomogeneous optical line. In the second experiment, direct evidence for the presence of a spin diffusion barrier or "frozen core" in Pr^{3+}:LaF _3 is observed by examining the cross relaxation between the Pr and F nuclei in a magnetic field chosen so that a pair of the optical ground state Pr^ {3+} hyperfine energy levels matches the F splitting or a multiple of the F splitting. This level crossing condition allows resonant flip-flop interactions with the nearest neighbor frozen core fluorine spins to re-populate Pr^{3+} hyperfine levels emptied by laser hole-burning, and is detected as enhanced absorption of the laser beam. The coupling of core fluorine spins to bulk fluorine spins during Pr-F cross-relaxation is measured by NMR of the bulk fluorine spin magnetization. The rate of cross relaxation between
New formulation of Magnetization Equation for Flowing Nuclear Spin under NMR/MRI Excitation(I)
NASA Astrophysics Data System (ADS)
de, Dilip; Emetere, Moses; Omotosho, Victor
2015-03-01
We have obtained for the first time from the Bloch NMR equations the correct dependence of the single component of magnetization, My and Mz at resonance (NMR/MRI) on relaxation times, rf B1 field (pulsed or continuous), blood(nuclear spin) flow velocity, etc. in the rotating frame of reference. The equations are applicable for both CW and pulsed NMR experiments with or without flow of spins. Our approaches can be extended easily to include gradient fields and diffusion of spins, if needed in NMR/MRI experiments. We also discuss the application of our equations to a specific case of MR excitation scheme: Free induction decay. The first time new equations of single component of MR magnetization and further equations that can be derived with the methodologies used here, can be applied towards accurate simulation of MR images/signals and extraction of parameters of clinical importance through comparison of the measured and the simulated images/signals.
Xue, Hai-Bin; Nie, Yi-Hang; Chen, Jingzhe; Ren, Wei
2015-03-15
We study theoretically the full counting statistics of electron transport through a quantum dot weakly coupled to two ferromagnetic leads, in which an effective nuclear-spin magnetic field originating from the configuration of nuclear spins is considered. We demonstrate that the quantum coherence between the two singly-occupied eigenstates and the spin polarization of two ferromagnetic leads play an important role in the formation of super-Poissonian noise. In particular, the orientation and magnitude of the effective field have a significant influence on the variations of the values of high-order cumulants, and the variations of the skewness and kurtosis values are more sensitive to the orientation and magnitude of the effective field than the shot noise. Thus, the high-order cumulants of transport current can be used to qualitatively extract information on the orientation and magnitude of the effective nuclear-spin magnetic field in a single quantum dot. - Highlights: • The effective nuclear-spin magnetic field gives rise to the off-diagonal elements of the reduced density matrix of single QD. • The off-diagonal elements of reduced density matrix of the QD have a significant impact on the high-order current cumulants. • The high-order current cumulants are sensitive to the orientation and magnitude of the effective nuclear-spin magnetic field. • The FCS can be used to detect the orientation and magnitude of the effective nuclear-spin magnetic field in a single QD.
Bryce, David L; Wasylishen, Roderick E; Autschbach, Jochen; Ziegler, Tom
2002-05-01
There have been significant advances in the calculation and interpretation of indirect nuclear spin-spin coupling (J) tensors during the past few years; however, much work remains to be done, especially for molecules containing heavy atoms where relativistic effects may play an important role. Many J tensors cannot be explained based solely on a nonrelativistic Fermi-contact mechanism. In the present work, the relativistic zeroth-order regular approximation density-functional (ZORA-DFT) implementation for the calculation of J has been applied to the complete series of homonuclear and heteronuclear diatomic halogen molecules: F(2), Cl(2), Br(2), I(2), At(2), ClF, BrF, IF, ClBr, ClI, and BrI. For all of these compounds, the reduced isotropic coupling constant (K(iso)) is positive and the reduced anisotropic coupling constant (DeltaK) is negative. With the exception of molecular fluorine, the magnitudes of K(iso) and DeltaK are shown to increase linearly with the product of the atomic numbers of the coupled nuclei. ZORA-DFT calculations of J for F(2) and ClF are in excellent agreement with the results obtained from multiconfigurational self-consistent-field calculations. The relative importance of the various coupling mechanisms is approximately constant for all of the compounds, with the paramagnetic spin-orbit term being the dominant contributor to K(iso), at approximately 70-80%. Available experimental stimulated resonant Raman spectroscopy data are exploited to extract the complete J((127)I,(127)I) tensor for iodine in two rotational states. The dependence of K(iso) and DeltaK on bond length and rovibrational state is investigated by using calculated results in combination with available experimental data. In addition to providing new insights into periodic trends for J coupling tensors, this work further demonstrates the utility of the ZORA-DFT method and emphasizes the necessity of spin-orbit relativistic corrections for J calculations involving heavy nuclei
Nuclear-driven electron spin rotations in a coupled silicon quantum dot and single donor system
NASA Astrophysics Data System (ADS)
Harvey-Collard, Patrick; Jacobson, Noah Tobias; Rudolph, Martin; Ten Eyck, Gregory A.; Wendt, Joel R.; Pluym, Tammy; Lilly, Michael P.; Pioro-Ladrière, Michel; Carroll, Malcolm S.
Single donors in silicon are very good qubits. However, a central challenge is to couple them to one another. To achieve this, many proposals rely on using a nearby quantum dot (QD) to mediate an interaction. In this work, we demonstrate the coherent coupling of electron spins between a single 31P donor and an enriched 28Si metal-oxide-semiconductor few-electron QD. We show that the electron-nuclear spin interaction can drive coherent rotations between singlet and triplet electron spin states. Moreover, we are able to tune electrically the exchange interaction between the QD and donor electrons. The combination of single-nucleus-driven rotations and voltage-tunable exchange provides all elements for future all-electrical control of a spin qubit, and requires only a single dot and no additional magnetic field gradients. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under Contract DE-AC04-94AL85000.
Long-lived nuclear spin states in monodeuterated methyl groups.
Elliott, Stuart J; Brown, Lynda J; Dumez, Jean-Nicolas; Levitt, Malcolm H
2016-07-21
It is possible to access long-lived nuclear singlet order in monodeuterated methyl groups, in the case that a significant chemical shift difference exists between the CH2D protons. This occurs when the local environment is chiral, and the CH2D rotamers have different populations. An experimental demonstration is presented for the case of N-CH2D-2-methylpiperidine. The ratio of the singlet relaxation time constant TS to the longitudinal relaxation time constant T1 is found to be equal to 3.1 ± 0.1, over a wide range of temperatures, solvents, and magnetic fields. The longest observed value of TS approaches 1 minute. The relaxation mechanisms of the long-lived state are discussed, and a modified model of the CH2D geometry is proposed to explain the observed ratio of TS to T1. PMID:27327382
Obaid, Rana; Kinzel, Daniel; Oppel, Markus González, Leticia
2014-10-28
Despite the concept of nuclear spin isomers (NSIs) exists since the early days of quantum mechanics, only few approaches have been suggested to separate different NSIs. Here, a method is proposed to discriminate different NSIs of a quinodimethane derivative using its electronic excited state dynamics. After electronic excitation by a laser field with femtosecond time duration, a difference in the behavior of several quantum mechanical operators can be observed. A pump-probe experimental approach for separating these different NSIs is then proposed.
NASA Astrophysics Data System (ADS)
Xiao, Yunlong; Zhang, Yong; Liu, Wenjian
2014-10-01
Both kinetically balanced (KB) and kinetically unbalanced (KU) rotational London orbitals (RLO) are proposed to resolve the slow basis set convergence in relativistic calculations of nuclear spin-rotation (NSR) coupling tensors of molecules containing heavy elements [Y. Xiao and W. Liu, J. Chem. Phys. 138, 134104 (2013)]. While they perform rather similarly, the KB-RLO Ansatz is clearly preferred as it ensures the correct nonrelativistic limit even with a finite basis. Moreover, it gives rise to the same "direct relativistic mapping" between nuclear magnetic resonance shielding and NSR coupling tensors as that without using the London orbitals [Y. Xiao, Y. Zhang, and W. Liu, J. Chem. Theory Comput. 10, 600 (2014)].
Diffusion-mediated nuclear spin phase decoherence in cylindrically porous materials
NASA Astrophysics Data System (ADS)
Knight, Michael J.; Kauppinen, Risto A.
2016-08-01
In NMR or MRI of complex materials, including biological tissues and porous materials, magnetic susceptibility differences within the material result in local magnetic field inhomogeneities, even if the applied magnetic field is homogeneous. Mobile nuclear spins move though the inhomogeneous field, by translational diffusion and other mechanisms, resulting in decoherence of nuclear spin phase more rapidly than transverse relaxation alone. The objective of this paper is to simulate this diffusion-mediated decoherence and demonstrate that it may substantially reduce coherence lifetimes of nuclear spin phase, in an anisotropic fashion. We do so using a model of cylindrical pores within an otherwise homogeneous material, and calculate the resulting magnetic field inhomogeneities. Our simulations show that diffusion-mediated decoherence in a system of parallel cylindrical pores is anisotropic, with coherence lifetime minimised when the array of cylindrical pores is perpendicular to B0. We also show that this anisotropy of coherence lifetime is reduced if the orientations of cylindrical pores are disordered within the system. In addition we characterise the dependence on B0, the magnetic susceptibility of the cylindrical pores relative to the surroundings, the diffusion coefficient and cylinder wall thickness. Our findings may aid in the interpretation of NMR and MRI relaxation data.
Diffusion-mediated nuclear spin phase decoherence in cylindrically porous materials.
Knight, Michael J; Kauppinen, Risto A
2016-08-01
In NMR or MRI of complex materials, including biological tissues and porous materials, magnetic susceptibility differences within the material result in local magnetic field inhomogeneities, even if the applied magnetic field is homogeneous. Mobile nuclear spins move though the inhomogeneous field, by translational diffusion and other mechanisms, resulting in decoherence of nuclear spin phase more rapidly than transverse relaxation alone. The objective of this paper is to simulate this diffusion-mediated decoherence and demonstrate that it may substantially reduce coherence lifetimes of nuclear spin phase, in an anisotropic fashion. We do so using a model of cylindrical pores within an otherwise homogeneous material, and calculate the resulting magnetic field inhomogeneities. Our simulations show that diffusion-mediated decoherence in a system of parallel cylindrical pores is anisotropic, with coherence lifetime minimised when the array of cylindrical pores is perpendicular to B0. We also show that this anisotropy of coherence lifetime is reduced if the orientations of cylindrical pores are disordered within the system. In addition we characterise the dependence on B0, the magnetic susceptibility of the cylindrical pores relative to the surroundings, the diffusion coefficient and cylinder wall thickness. Our findings may aid in the interpretation of NMR and MRI relaxation data. PMID:27208416
Quantum cognition: The possibility of processing with nuclear spins in the brain
NASA Astrophysics Data System (ADS)
Fisher, Matthew P. A.
2015-11-01
The possibility that quantum processing with nuclear spins might be operative in the brain is explored. Phosphorus is identified as the unique biological element with a nuclear spin that can serve as a qubit for such putative quantum processing-a neural qubit-while the phosphate ion is the only possible qubit-transporter. We identify the "Posner molecule", Ca9(PO4)6, as the unique molecule that can protect the neural qubits on very long times and thereby serve as a (working) quantum-memory. A central requirement for quantum-processing is quantum entanglement. It is argued that the enzyme catalyzed chemical reaction which breaks a pyrophosphate ion into two phosphate ions can quantum entangle pairs of qubits. Posner molecules, formed by binding such phosphate pairs with extracellular calcium ions, will inherit the nuclear spin entanglement. A mechanism for transporting Posner molecules into presynaptic neurons during vesicle endocytosis is proposed. Quantum measurements can occur when a pair of Posner molecules chemically bind and subsequently melt, releasing a shower of intra-cellular calcium ions that can trigger further neurotransmitter release and enhance the probability of post-synaptic neuron firing. Multiple entangled Posner molecules, triggering non-local quantum correlations of neuron firing rates, would provide the key mechanism for neural quantum processing. Implications, both in vitro and in vivo, are briefly mentioned.
Nuclear Magnetic Spin-Noise and Unusual Relaxation of Oxygen-17 in Water
NASA Astrophysics Data System (ADS)
Bendet-Taicher, Eli
Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) have evolved into widely used techniques, providing diagnostic power in medicine and material sciences due to their high precision and non-invasive nature. Due to the small population differences between spin energy states, a significant sensitivity problem for NMR arises. The low sensitivity of NMR is probably its greatest limitation for applications to biological systems. An alternative probe tuning strategy based on the spin-noise response for application in standard one-dimensional and common high-resolution multidimensional standard biomolecular NMR experiments has shown an increase of up to 50% signal-to-noise (SNR) in one-dimensional NMR experiments and an increase of up to 22% in multi-dimensional ones. The method requires the adjustment of the optimal tuning condition, which may be offset by several hundreds kHz from the conventional tuning settings using the noise response of the water protons as an indicator. This work is described in the first part of the thesis (chapters 2--3). The second part (Chapter 4) of the thesis deals with anomalous oxygen-17 NMR relaxation behavior in water. Oxygen-17 (17O), which has spin of 5/2 and a natural abundance of 0.0373% possesses an electric quadrupole moment. Spin-lattice and spin-spin relaxation occur by the quadrupole interaction, while the J-coupling to 1H spins and exchange are deciding factors. T1 and T2 of 17O in water have been previously measured over a large range of temperatures. The spin-spin relaxation times of 17O as a function of temperature show an anomalous behaviour, expressed by a local maximum at the temperature of maximum density (TMD) of water. It is shown that the same anomalous behaviour shifts to the respective temperatures of maximum density for H2O/D2O solutions with different compositions and salt concentrations. This phenomenon can be correlated to the pH dependency of T2 of 17O in water, and water proton exchange rates
A NEW METHOD FOR EXTRACTING SPIN-DEPENDENT NEUTRON STRUCTURE FUNCTIONS FROM NUCLEAR DATA
Kahn, Y.F.; Melnitchouk, W.
2009-01-01
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.
Rotor Design for High Pressure Magic Angle Spinning Nuclear Magnetic Resonance
Turcu, Romulus V.F.; Hoyt, David W.; Rosso, Kevin M.; Sears, Jesse A.; Loring, John S.; Felmy, Andrew R.; Hu, Jian Z.
2013-01-01
High pressure magic angle spinning (MAS) nuclear magnetic resonance (NMR) with a sample spinning rate exceeding 2.1 kHz and pressure greater than 165 bar has never been realized. In this work, a new sample cell design is reported, suitable for constructing cells of different sizes. Using a 7.5 mm high pressure MAS rotor as an example, internal pressure as high as 200 bar at a sample spinning rate of 6 kHz is achieved. The new high pressure MAS rotor is re-usable and compatible with most commercial NMR set-ups, exhibiting low 1H and 13C NMR background and offering maximal NMR sensitivity. As an example of its many possible applications, this new capability is applied to determine reaction products associated with the carbonation reaction of a natural mineral, antigorite ((Mg,Fe2+)3Si2O5(OH)4), in contact with liquid water in water-saturated supercritical CO2 (scCO2) at 150 bar and 50 deg C. This mineral is relevant to the deep geologic disposal of CO2, but its iron content results in too many sample spinning sidebands at low spinning rate. Hence, this chemical system is a good case study to demonstrate the utility of the higher sample spinning rates that can be achieved by our new rotor design. We expect this new capability will be useful for exploring solid-state, including interfacial, chemistry at new levels of high-pressure in a wide variety of fields.
Rotor design for high pressure magic angle spinning nuclear magnetic resonance.
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
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 (1)H and (13)C 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,Fe(2+))(3)Si(2)O(5)(OH)(4)), in contact with liquid water in water-saturated supercritical CO(2) (scCO(2)) at 150 bar and 50°C. This mineral is relevant to the deep geologic disposal of CO(2), 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. PMID:23220181
Rotor design for high pressure magic angle spinning nuclear magnetic resonance
NASA Astrophysics Data System (ADS)
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
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.
NASA Astrophysics Data System (ADS)
Gumann, Patryk; Ramanathan, Chandrasekhar; Patange, Om; Moussa, Osama; Thewalt, Mike; Riemann, Helge; Abrosimov, Nikolay; Becker, Peter; Pohl, Hans-Joachim; Itoh, Kohei; Cory, David G.
2014-03-01
We experimentally demonstrate the optical hyperpolarization and coherent control of 31P, nuclear spins in single crystal silicon via the inductive readout of the nuclear magnetic resonance (NMR) signal of 31P at a concentration of 1.5 x 1015 cc-1. The obtained polarization is sufficient the 31P spin polarization of 1.17 x 1015 in a 10 mm x 10 mm sample, observed in one FID with signal-to-noise ration of 113. The linewidth is 800 Hz. The Hahn echo pulse sequence reveals a 31P T2 time of 0.42 s at 1.6 K, which was extended by the Carr Purcell cycle to 1.2 s at the same temperature. The maximum build-up of the nuclear polarization was achieved within ~577 seconds, at 4.2 K, in 6.7 T, using optical excitations provided by an infra-red laser. This work has been supported by CERC Canada.
Nuclear-spin-induced cotton-mouton effect in a strong external magnetic field.
Fu, Li-Juan; Vaara, Juha
2014-08-01
Novel, high-sensitivity and high-resolution spectroscopic methods can provide site-specific nuclear information by exploiting nuclear magneto-optic properties. We present a first-principles electronic structure formulation of the recently proposed nuclear-spin-induced Cotton-Mouton effect in a strong external magnetic field (NSCM-B). In NSCM-B, ellipticity is induced in a linearly polarized light beam, which can be attributed to both the dependence of the symmetric dynamic polarizability on the external magnetic field and the nuclear magnetic moment, as well as the temperature-dependent partial alignment of the molecules due to the magnetic fields. Quantum-chemical calculations of NSCM-B were conducted for a series of molecular liquids. The overall order of magnitude of the induced ellipticities is predicted to be 10(-11) -10(-6) rad T(-1) M(-1) cm(-1) for fully spin-polarized nuclei. In particular, liquid-state heavy-atom systems should be promising for experiments in the Voigt setup. PMID:24862946
Sensing of single nuclear spins in random thermal motion with proximate nitrogen-vacancy centers
NASA Astrophysics Data System (ADS)
Bruderer, M.; Fernández-Acebal, P.; Aurich, R.; Plenio, M. B.
2016-03-01
Nitrogen-vacancy (NV) centers in diamond have emerged as valuable tools for sensing and polarizing spins. Motivated by potential applications in chemistry, biology, and medicine, we show that NV-based sensors are capable of detecting single spin targets even if they undergo diffusive motion in an ambient thermal environment. Focusing on experimentally relevant diffusion regimes, we derive an effective model for the NV-target interaction, where parameters entering the model are obtained from numerical simulations of the target motion. The practicality of our approach is demonstrated by analyzing two realistic experimental scenarios: (i) time-resolved sensing of a fluorine nuclear spin bound to an N-heterocyclic carbene-ruthenium (NHC-Ru) catalyst that is immobilized on the diamond surface and (ii) detection of an electron spin label by an NV center in a nanodiamond, both attached to a vibrating chemokine receptor in thermal motion. We find in particular that the detachment of a fluorine target from the NHC-Ru carrier molecule can be monitored with a time resolution of a few seconds.
Progress of the 129Xe EDM search using active feedback nuclear spin maser
NASA Astrophysics Data System (ADS)
Sato, Tomoya; Ichikawa, Yuichi; Ohtomo, Yuichi; Sakamoto, Yu; Kojima, Shuichiro; Funayama, Chikako; Suzuki, Takahiro; Chikamori, Masatoshi; Hikota, Eri; Tsuchiya, Masato; Furukawa, Takeshi; Yoshimi, Akihiro; Bidinosti, Christopher; Ino, Takashi; Ueno, Hideki; Matsuo, Yukari; Fukuyama, Takeshi; Asahi, Koichiro
2014-09-01
A permanent electric dipole moment (EDM) of a particle is an extremely sensitive probe for physics beyond the Standard Model. The objective of the present study is to search for the 129Xe EDM at a level of 10-28 ecm, beyond the current upper limit. In this experiment, an active-feedback nuclear spin maser is employed to achieve a precision measurement. Systematic instability sets a limit on the precision in our study. Co-magnetometry using 3He spin maser was incorporated into the maser system to eliminate the frequency drift caused by magnetic field fluctuations. Moreover, a double-cell geometry with linearly polarized laser was introduced to reduce frequency drifts arising from contact interactions with polarized Rb atoms. Having integrated these improvements, the 3He/129Xe dual spin maser was successfully operated. In the presentation, recent progress will be reported, including an analysis of spin maser frequencies, a study of electrode designs, and an estimation of possible systematic uncertainties.
NASA Astrophysics Data System (ADS)
Wu, Gang
2016-08-01
The nuclear quadrupole transverse relaxation process of half-integer spins in liquid samples is known to exhibit multi-exponential behaviors. Within the framework of Redfield's relaxation theory, exact analytical expressions for describing such a process exist only for spin-3/2 nuclei. As a result, analyses of nuclear quadrupole transverse relaxation data for half-integer quadrupolar nuclei with spin >3/2 must rely on numerical diagonalization of the Redfield relaxation matrix over the entire motional range. In this work we propose an approximate analytical expression that can be used to analyze nuclear quadrupole transverse relaxation data of any half-integer spin in liquids over the entire motional range. The proposed equation yields results that are in excellent agreement with the exact numerical calculations.
Wu, Gang
2016-08-01
The nuclear quadrupole transverse relaxation process of half-integer spins in liquid samples is known to exhibit multi-exponential behaviors. Within the framework of Redfield's relaxation theory, exact analytical expressions for describing such a process exist only for spin-3/2 nuclei. As a result, analyses of nuclear quadrupole transverse relaxation data for half-integer quadrupolar nuclei with spin >3/2 must rely on numerical diagonalization of the Redfield relaxation matrix over the entire motional range. In this work we propose an approximate analytical expression that can be used to analyze nuclear quadrupole transverse relaxation data of any half-integer spin in liquids over the entire motional range. The proposed equation yields results that are in excellent agreement with the exact numerical calculations. PMID:27343483
NASA Astrophysics Data System (ADS)
Herlitschke, M.; Disch, S.; Sergueev, I.; Schlage, K.; Wetterskog, E.; Bergström, L.; Hermann, R. P.
2016-04-01
The manuscript reports the investigation of spin disorder in maghemite nanoparticles of different shape by a combination of polarized small-angle neutron scattering (SANSPOL) and nuclear forward scattering (NFS) techniques. Both methods are sensitive to magnetization on the nanoscale. SANSPOL allows for investigation of the particle morphology and spatial magnetization distribution and NFS extends this nanoscale information to the atomic scale, namely the orientation of the hyperfine field experienced by the iron nuclei. The studied nanospheres and nanocubes with diameters of 7.4 nm and 10.6 nm, respectively, exhibit a significant spin disorder. This effect leads to a reduction of the magnetization to 44% and 58% of the theoretical maghemite bulk value, observed consistently by both techniques.
Magic radio-frequency dressing of nuclear spins in high-accuracy optical clocks.
Zanon-Willette, Thomas; de Clercq, Emeric; Arimondo, Ennio
2012-11-30
A Zeeman-insensitive optical clock atomic transition is engineered when nuclear spins are dressed by a nonresonant radio-frequency field. For fermionic species as (87)Sr, (171)Yb, and (199)Hg, particular ratios between the radio-frequency driving amplitude and frequency lead to "magic" magnetic values where a net cancelation of the Zeeman clock shift and a complete reduction of first-order magnetic variations are produced within a relative uncertainty below the 10(-18) level. An Autler-Townes continued fraction describing a semiclassical radio-frequency dressed spin is numerically computed and compared to an analytical quantum description including higher-order magnetic field corrections to the dressed energies. PMID:23368116
Nuclear Spin relaxation mediated by Fermi-edge electrons in n-type GaAs
NASA Astrophysics Data System (ADS)
Kotur, M.; Dzhioev, R. I.; Kavokin, K. V.; Korenev, V. L.; Namozov, B. R.; Pak, P. E.; Kusrayev, Yu. G.
2014-03-01
A method based on the optical orientation technique was developed to measure the nuclear-spin lattice relaxation time T 1 in semiconductors. It was applied to bulk n-type GaAs, where T 1 was measured after switching off the optical excitation in magnetic fields from 400 to 1200 G at low (< 30 K) temperatures. The spin-lattice relaxation of nuclei in the studied sample with n D = 9 × 1016 cm-3 was found to be determined by hyperfine scattering of itinerant electrons (Korringa mechanism) which predicts invariability of T 1 with the change in magnetic field and linear dependence of the relaxation rate on temperature. This result extends the experimentally verified applicability of the Korringa relaxation law in degenerate semiconductors, previously studied in strong magnetic fields (several Tesla), to the moderate field range.
Herlitschke, Marcus; Disch, Sabrina; Sergueev, I.; Schlage, Kai; Wetterskog, Erik; Bergstrom, Lennart; Hermann, Raphael P.
2016-01-01
The manuscript reports the investigation of spin disorder in maghemite nanoparticles of different shape by a combination of polarized small-angle neutron scattering (SANSPOL) and nuclear forward scattering (NFS) techniques. Both methods are sensitive to magnetization on the nanoscale. SANSPOL allows for investigation of the particle morphology and spatial magnetization distribution and NFS extends this nanoscale information to the atomic scale, namely the orientation of the hyperfine field experienced by the iron nuclei. The studied nanospheres and nanocubes with diameters of 7.4nm and 10.6 nm, respectively, exhibit a significant spin disorder. This effect leads to a reduction of the magnetization tomore » 44% and 58% of the theoretical maghemite bulk value, observed consistently by both techniques.« less
Difference between nuclear spin relaxation and ionic conductivity relaxation in superionic glasses
NASA Astrophysics Data System (ADS)
Ngai, K. L.
1993-04-01
Tatsumisago, Angell, and Martin [J. Chem. Phys. 97, 6968 (1992)] have compared conductivity relaxation data and 7Li nuclear spin lattice relaxation (SLR) data measured on a lithium chloroborate glass and found pronounced differences in the most probable relaxation times. The electrical conductivity relaxation (ECR) time, τ*σ, at some temperature occurs on a time scale shorter by some two orders of magnitude than the 7Li spin lattice relaxation correlation time, τ*s, and has a significantly lower activation energy. SLR and ECR monitor the motions of ions through different dynamic variables and correlation functions. Using this fact and the coupling model, I am able to explain quantitatively all aspects of the difference between SLR and ECR, and to establish relations between their different relaxation characteristics. The large difference between the observed activation energies of SLR and ECR alone should have implications on the validity of any proposed theory of the dynamics of ionic transport.
Sukstanskii, A.L.; Ackerman, J.J.H.; Yablonskiy, D.A.
2007-01-01
The spatial distribution of the transverse nuclear spin magnetization, appearing in a single compartment with impermeable boundaries in a Stejskal-Tanner gradient pulse MR experiment, is analyzed in detail. At short diffusion times the presence of diffusion-restrictive barriers (membranes) reduces effective diffusivity near the membranes and leads to an inhomogeneous spin magnetization distribution (the edge-enhancement effect). In this case, the signal reveals a quasi-two-compartment behavior and can be empirically modeled remarkably well by a biexponential function. The current results provide a framework for interpreting experimental MR data on various phenoma, including water diffusion in giant axons, metabolite diffusion in the brain, and hyperpolarized gas diffusion in lung airways. PMID:14523959
Impact of hadronic and nuclear corrections on global analysis of spin-dependent parton distributions
Jimenez-Delgado, Pedro; Accardi, Alberto; Melnitchouk, Wally
2014-02-01
We present the first results of a new global next-to-leading order analysis of spin-dependent parton distribution functions from the most recent world data on inclusive polarized deep-inelastic scattering, focusing in particular on the large-x and low-Q^2 regions. By directly fitting polarization asymmetries we eliminate biases introduced by using polarized structure function data extracted under nonuniform assumptions for the unpolarized structure functions. For analysis of the large-x data we implement nuclear smearing corrections for deuterium and 3He nuclei, and systematically include target mass and higher twist corrections to the g_1 and g_2 structure functions at low Q^2. We also explore the effects of Q^2 and W^2 cuts in the data sets, and the potential impact of future data on the behavior of the spin-dependent parton distributions at large x.
NASA Astrophysics Data System (ADS)
Komlosh, M. E.; Callaghan, P. T.
1998-12-01
Pulsed gradient spin echo nuclear magnetic resonance (NMR) is used to investigate polymer mean-squared segmental displacements in semidilute solutions of high molar mass polystyrene in deuterio-toluene. Nine molar masses from 1 to 20 million daltons are studied at a fixed concentration of 5% w/v, and a range of concentrations from 5% to 20% at fixed molar mass of 3 million daltons. The distance and time scales accessed are 20 to 1000 nm and 10 to 3000 ms, respectively. Evidence for intrachain spin diffusion is found and its effect corrected for. The time dependence of mean-squared segmental displacements is fitted to the predictions of the Doi-Edwards model and tube disengagement times and tube diameters obtained.
Herlitschke, Marcus; Disch, Sabrina; Sergueev, I.; Schlage, Kai; Wetterskog, Erik; Bergstrom, Lennart; Hermann, Raphael P.
2016-01-01
The manuscript reports the investigation of spin disorder in maghemite nanoparticles of different shape by a combination of polarized small-angle neutron scattering (SANSPOL) and nuclear forward scattering (NFS) techniques. Both methods are sensitive to magnetization on the nanoscale. SANSPOL allows for investigation of the particle morphology and spatial magnetization distribution and NFS extends this nanoscale information to the atomic scale, namely the orientation of the hyperfine field experienced by the iron nuclei. The studied nanospheres and nanocubes with diameters of 7.4nm and 10.6 nm, respectively, exhibit a significant spin disorder. This effect leads to a reduction of the magnetization to 44% and 58% of the theoretical maghemite bulk value, observed consistently by both techniques.
EDM measurement in 129Xe atom using dual active feedback nuclear spin maser
NASA Astrophysics Data System (ADS)
Sato, T.; Ichikawa, Y.; Ohtomo, Y.; Sakamoto, Y.; Kojima, S.; Funayama, C.; Suzuki, T.; Chikamori, M.; Hikota, E.; Tsuchiya, M.; Furukawa, T.; Yoshimi, A.; Bidinosti, C. P.; Ino, T.; Ueno, H.; Matsuo, Y.; Fukuyama, T.; Asahi, K.
2015-04-01
The technique of an active nuclear spin maser is adopted in the search for electric dipole moment in a diamagnetic atom 129Xe. In order to reduce systematic uncertainties arising from long-term drifts of the external magnetic field and from the contact interaction between longitudinal polarized Rb atoms and 129Xe spin, a 3He comagnetometer with a double-cell geometry was employed. The remaining shift, which turned out to show some correlation with the cell temperature, was mitigated by stabilizing the cell temperature. As a result, the frequency drift of the 129Xe maser was reduced from 12 mHz to 700 μHz, and the determination precision of frequency of 8.7 nHz was obtained for a 2×104 s measurement time using the double-cell geometry cell.
Wylie, Benjamin J; Dzikovski, Boris G.; Pawsey, Shane; Caporini, Marc; Rosay, Melanie; Freed, Jack H.; McDermott, Ann E.
2016-01-01
We demonstrate that dynamic nuclear polarization (DNP) of membrane proteins in lipid bilayers may be achieved using a novel polarizing agent: pairs of spin labels covalently bound to a protein of interest interacting at an intermolecular interaction surface. For gramicidin A, nitroxide tags attached to the N-terminal intermolecular interface region become proximal only when bimolecular channels forms in the membrane. We obtained signal enhancements of 6-fold for the dimeric protein. The enhancement affect was comparable to that of a doubly tagged sample of gramicidin C, with intramolecular spin pairs. This approach could be a powerful and selective means for signal enhancement in membrane proteins, and for recognizing intermolecular interfaces. PMID:25828256
Bigdeli, M.; Bordbar, G. H.; Poostforush, A.
2010-09-15
The lowest order constrained variational technique has been used to investigate some of the thermodynamic properties of spin-polarized hot asymmetric nuclear matter, such as the free energy, symmetry energy, susceptibility, and equation of state. We have shown that the symmetry energy of the nuclear matter is substantially sensitive to the value of spin polarization. Our calculations show that the equation of state of the polarized hot asymmetric nuclear matter is stiffer for higher values of the polarization as well as the isospin asymmetry parameter. Our results for the free energy and susceptibility show that spontaneous ferromagnetic phase transition cannot occur for hot asymmetric matter.
Resonance-inclined optical nuclear spin polarization of liquids in diamond structures
NASA Astrophysics Data System (ADS)
Chen, Q.; Schwarz, I.; Jelezko, F.; Retzker, A.; Plenio, M. B.
2016-02-01
Dynamic nuclear polarization (DNP) of molecules in a solution at room temperature has the potential to revolutionize nuclear magnetic resonance spectroscopy and imaging. The prevalent methods for achieving DNP in solutions are typically most effective in the regime of small interaction correlation times between the electron and nuclear spins, limiting the size of accessible molecules. To solve this limitation, we design a mechanism for DNP in the liquid phase that is applicable for large interaction correlation times. Importantly, while this mechanism makes use of a resonance condition similar to solid-state DNP, the polarization transfer is robust to a relatively large detuning from the resonance due to molecular motion. We combine this scheme with optically polarized nitrogen-vacancy (NV) center spins in nanodiamonds to design a setup that employs optical pumping and is therefore not limited by room temperature electron thermal polarization. We illustrate numerically the effectiveness of the model in a flow cell containing nanodiamonds immobilized in a hydrogel, polarizing flowing water molecules 4700-fold above thermal polarization in a magnetic field of 0.35 T, in volumes detectable by current NMR scanners.
Dynamic nuclear polarization of carbonyl and methyl 13C spins in acetate using trityl OX063
NASA Astrophysics Data System (ADS)
Niedbalski, Peter; Parish, Christopher; Lumata, Lloyd
2015-03-01
Hyperpolarization via dissolution dynamic nuclear polarization (DNP) is a physics technique that amplifies the magnetic resonance signals by several thousand-fold for biomedical NMR spectroscopy and imaging (MRI). Herein we have investigated the effect of carbon-13 isotopic location on the DNP of acetate (one of the biomolecules commonly used for hyperpolarization) at 3.35 T and 1.4 K using a narrow ESR linewidth free radical trityl OX063. We have found that the carbonyl 13C spins yielded about twice the polarization produced in methyl 13C spins. Deuteration of the methyl group, beneficial in the liquid-state, did not produce an improvement in the polarization level at cryogenic conditions. Concurrently, the solid-state nuclear relaxation of these samples correlate with the polarization levels achieved. These results suggest that the location of the 13C isotopic labeling in acetate has a direct impact on the solid-state polarization achieved and is mainly governed by the nuclear relaxation leakage factor.
Pravdivtsev, Andrey N; Yurkovskaya, Alexandra V; Kaptein, Robert; Miesel, Karsten; Vieth, Hans-Martin; Ivanov, Konstantin L
2013-09-21
Spin hyperpolarization can be coherently transferred to other nuclei in field-cycling NMR experiments. At low magnetic fields spin polarization is redistributed in a strongly coupled network of spins. Polarization transfer is most efficient at fields where level anti-crossings (LACs) occur for the nuclear spin-states. A further condition is that field switching to the LAC positions is non-adiabatic in order to convert the starting population differences into spin coherences that cause time-dependent mixing of states. The power of this method has been demonstrated by studying transfer of photo-Chemically Induced Dynamic Nuclear Polarization (photo-CIDNP) in N-acetyl-tryptophan. We have investigated the magnetic field dependence and time dependence of coherent CIDNP transfer and directly assessed nuclear spin LACs by studying polarization transfer at specific field positions. The proposed approach based on LACs is not limited to CIDNP but is advantageous for enhancing NMR signals by spin order transfer from any type of hyper-polarized nuclei. PMID:23893009
Peat, David T; Horsewill, Anthony J; Köckenberger, Walter; Perez Linde, Angel J; Gadian, David G; Owers-Bradley, John R
2013-05-28
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
NASA Astrophysics Data System (ADS)
Ulhaq, A.; Duan, Q.; Zallo, E.; Ding, F.; Schmidt, O. G.; Tartakovskii, A. I.; Skolnick, M. S.; Chekhovich, E. A.
2016-04-01
GaAs/AlGaAs quantum dots grown by in situ droplet etching and nanohole in-filling offer a combination of strong charge confinement, optical efficiency, and high spatial symmetry advantageous for polarization entanglement and spin-photon interface. Here, we study experimentally electron and nuclear spin properties of such dots. We find nearly vanishing electron g factors (ge<0.05 ), providing a potential route for electrically driven spin control schemes. Optical manipulation of the nuclear spin environment is demonstrated with nuclear spin polarization up to 65 % achieved. Nuclear magnetic resonance spectroscopy reveals two distinct types of quantum dots: with tensile and with compressive strain along the growth axis. In both types of dots, the magnitude of strain ɛb<0.02 % is nearly three orders of magnitude smaller than in self-assembled dots: On the one hand, this provides a route for eliminating a major source of electron spin decoherence arising from nuclear quadrupolar interactions, and on the other hand such strain is sufficient to suppress nuclear spin diffusion leading to a stable nuclear spin bath with nuclear spin lifetimes exceeding 500 s. The spin properties revealed in this work make this new type of quantum dot an attractive alternative to self-assembled dots for the applications in quantum information technologies.
Interlayer transport of nuclear spin polarization in Î½ = 2/3 quantum Hall states
NASA Astrophysics Data System (ADS)
Tsuda, S.; Nguyen, M. H.; Terasawa, D.; Fukuda, A.; Zheng, Y. D.; Arai, T.; Sawada, A.
2013-12-01
We investigated the interlayer diffusion of nuclear spin polarization (NSP) by using the phase transition point of quantum Hall states at a Landau level filling factor of ν ν 2/3 in a double quantum well sample. When the NSP is current-pumped in one layer, the magnetoresistance in the other layer is enhanced after a delay of 150 s and the raising speed of this layer is lower than that of the pumped layer. The delay and lower value of the raising speed are explained by the diffusion of NSP.
Interlayer transport of nuclear spin polarization in ν = 2/3 quantum Hall states
Tsuda, S.; Nguyen, M. H.; Terasawa, D.; Fukuda, A.; Zheng, Y. D.; Arai, T.; Sawada, A.
2013-12-04
We investigated the interlayer diffusion of nuclear spin polarization (NSP) by using the phase transition point of quantum Hall states at a Landau level filling factor of ν ν 2/3 in a double quantum well sample. When the NSP is current-pumped in one layer, the magnetoresistance in the other layer is enhanced after a delay of 150 s and the raising speed of this layer is lower than that of the pumped layer. The delay and lower value of the raising speed are explained by the diffusion of NSP.
Level density inputs in nuclear reaction codes and the role of the spin cutoff parameter
Voinov, A. V.; Grimes, S. M.; Brune, C. R.; Burger, A.; Gorgen, A.; Guttormsen, M.; Larsen, A. C.; Massey, T. N.; Siem, S.
2014-09-03
Here, the proton spectrum from the ^{57}Fe(α,p) reaction has been measured and analyzed with the Hauser-Feshbach model of nuclear reactions. Different input level density models have been tested. It was found that the best description is achieved with either Fermi-gas or constant temperature model functions obtained by fitting them to neutron resonance spacing and to discrete levels and using the spin cutoff parameter with much weaker excitation energy dependence than it is predicted by the Fermi-gas model.
Level density inputs in nuclear reaction codes and the role of the spin cutoff parameter
Voinov, A. V.; Grimes, S. M.; Brune, C. R.; Burger, A.; Gorgen, A.; Guttormsen, M.; Larsen, A. C.; Massey, T. N.; Siem, S.
2014-09-03
Here, the proton spectrum from the 57Fe(α,p) reaction has been measured and analyzed with the Hauser-Feshbach model of nuclear reactions. Different input level density models have been tested. It was found that the best description is achieved with either Fermi-gas or constant temperature model functions obtained by fitting them to neutron resonance spacing and to discrete levels and using the spin cutoff parameter with much weaker excitation energy dependence than it is predicted by the Fermi-gas model.
Instrumentation for solid-state dynamic nuclear polarization with magic angle spinning NMR
NASA Astrophysics Data System (ADS)
Rosay, Melanie; Blank, Monica; Engelke, Frank
2016-03-01
Advances in dynamic nuclear polarization (DNP) instrumentation and methodology have been key factors in the recent growth of solid-state DNP NMR applications. We review the current state of the art of solid-state DNP NMR instrumentation primarily based on available commercial platforms. We start with a general system overview, including options for microwave sources and DNP NMR probes, and then focus on specific developments for DNP at 100 K with magic angle spinning (MAS). Gyrotron microwave sources, passive components to transmit microwaves, the DNP MAS probe, a cooling device for low-temperature MAS, and sample preparation procedures including radicals for DNP are considered.
Electron-mediated nuclear-spin interactions between distant nitrogen-vacancy centers.
Bermudez, A; Jelezko, F; Plenio, M B; Retzker, A
2011-10-01
We propose a scheme enabling controlled quantum coherent interactions between separated nitrogen-vacancy centers in diamond in the presence of strong magnetic fluctuations. The proposed scheme couples nuclear qubits employing the magnetic dipole-dipole interaction between the electron spins and, crucially, benefits from the suppression of the effect of environmental magnetic field fluctuations thanks to a strong microwave driving. This scheme provides a basic building block for a full-scale quantum-information processor or quantum simulator based on solid-state technology. PMID:22107276
Instrumentation for solid-state dynamic nuclear polarization with magic angle spinning NMR.
Rosay, Melanie; Blank, Monica; Engelke, Frank
2016-03-01
Advances in dynamic nuclear polarization (DNP) instrumentation and methodology have been key factors in the recent growth of solid-state DNP NMR applications. We review the current state of the art of solid-state DNP NMR instrumentation primarily based on available commercial platforms. We start with a general system overview, including options for microwave sources and DNP NMR probes, and then focus on specific developments for DNP at 100K with magic angle spinning (MAS). Gyrotron microwave sources, passive components to transmit microwaves, the DNP MAS probe, a cooling device for low-temperature MAS, and sample preparation procedures including radicals for DNP are considered. PMID:26920834
Measurement of nuclear magnetic dipole—dipole couplings in magic angle spinning NMR
NASA Astrophysics Data System (ADS)
Tycko, Robert; Dabbagh, Gary
1990-10-01
We describe a method for measuring nuclear magnetic dipole—dipole couplings in NMR spectra of solids undergoing rapid magic angle spinning (MAS). We show in theory, simulations, and experiments that the couplings, which are averaged out by MAS alone, can be recovered by applying simple resonant radiofrequency pulse sequences in synchrony with the sample rotation. Experimental 13C dipolar powder pattern spectra of polycrystalline ( 13CH 3) 2C(OH)SO 3Na obtained in a two-dimensional experiment based on this method are presented. The method provides a means of determining internuclear distances in polycrystalline and noncrystalline solids while retaining the high resolution and sensitivity afforded by MAS.
Level Density Inputs in Nuclear Reaction Codes and the Role of the Spin Cutoff Parameter
NASA Astrophysics Data System (ADS)
Voinov, A. V.; Grimes, S. M.; Brune, C. R.; Bürger, A.; Görgen, A.; Guttormsen, M.; Larsen, A. C.; Massey, T. N.; Siem, S.
2014-05-01
The proton spectrum from the 57Fe(α, p) reaction has been measured and analyzed with the Hauser-Feshbach model of nuclear reactions. Different input level density models have been tested. It was found that the best description is achieved with either Fermi-gas or constant temperature model functions obtained by fitting them to neutron resonance spacings and to discrete levels and using the spin cutoff parameter with much a weaker excitation energy dependence than predicted by the Fermi-gas model.
Ong, A.; Berengut, J. C.; Flambaum, V. V.
2010-07-15
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.
Cardona-Serra, Salvador; Escalera-Moreno, Luis; Baldoví, José J; Gaita-Ariño, Alejandro; Clemente-Juan, Juan M; Coronado, Eugenio
2016-05-15
SIMPRE is a fortran77 code which uses an effective electrostatic model of point charges to predict the magnetic behavior of rare-earth-based mononuclear complexes. In this article, we present SIMPRE1.2, which now takes into account two further phenomena. First, SIMPRE now considers the hyperfine and quadrupolar interactions within the rare-earth ion, resulting in a more complete and realistic set of energy levels and wave functions. Second, and to widen SIMPRE's predictive capabilities regarding potential molecular spin qubits, it now includes a routine that calculates an upper-bound estimate of the decoherence time considering only the dipolar coupling between the electron spin and the surrounding nuclear spin bath. Additionally, SIMPRE now allows the user to introduce the crystal field parameters manually. Thus, we are able to demonstrate the new features using as examples (i) a Gd-based mononuclear complex known for its properties both as a single ion magnet and as a coherent qubit and (ii) an Er-based mononuclear complex. © 2016 Wiley Periodicals, Inc. PMID:26833799
Frequency-stepped acquisition in nuclear magnetic resonance spectroscopy under magic angle spinning
NASA Astrophysics Data System (ADS)
Pell, Andrew J.; Clément, Raphaële J.; Grey, Clare P.; Emsley, Lyndon; Pintacuda, Guido
2013-03-01
The nuclear magnetic resonance of paramagnetic solids is usually characterized by the presence of large chemical shifts and shift anisotropies due to hyperfine interactions. Frequently the resulting spectra cover a frequency range of several megahertz, which is greater than the bandwidth of commercially available radio-frequency (RF) probes, making it impossible to acquire the whole spectrum in a single experiment. In these cases it common to record a series of spectra, in which the probe is tuned to a different frequency for each, and then sum the results to give the "true" spectrum. While this method is very widely used on static samples, the application of frequency stepping under magic-angle spinning (MAS) is less common, owing to the increased complexity of the spin dynamics when describing the interplay of the RF irradiation with the mechanical rotation of the shift tensor. In this paper, we present a theoretical description, based on the jolting frame formalism of Caravatti et al. [J. Magn. Reson. 55, 88 (1983), 10.1016/0022-2364(83)90279-2], for describing the spin dynamics of a powder sample under MAS when subjected to a selective pulse of low RF-field amplitude. The formalism is used to describe the frequency stepping method under MAS, and under what circumstances the true spectrum is reproduced. We also present an experimental validation of the methodology under ultra-fast MAS with the paramagnetic materials LiMnPO4 and TbCsDPA.
Xiao, Yunlong; Zhang, Yong; Liu, Wenjian
2014-10-28
Both kinetically balanced (KB) and kinetically unbalanced (KU) rotational London orbitals (RLO) are proposed to resolve the slow basis set convergence in relativistic calculations of nuclear spin-rotation (NSR) coupling tensors of molecules containing heavy elements [Y. Xiao and W. Liu, J. Chem. Phys. 138, 134104 (2013)]. While they perform rather similarly, the KB-RLO Ansatz is clearly preferred as it ensures the correct nonrelativistic limit even with a finite basis. Moreover, it gives rise to the same "direct relativistic mapping" between nuclear magnetic resonance shielding and NSR coupling tensors as that without using the London orbitals [Y. Xiao, Y. Zhang, and W. Liu, J. Chem. Theory Comput. 10, 600 (2014)]. PMID:25362275
Xiao, Yunlong; Zhang, Yong; Liu, Wenjian
2014-10-28
Both kinetically balanced (KB) and kinetically unbalanced (KU) rotational London orbitals (RLO) are proposed to resolve the slow basis set convergence in relativistic calculations of nuclear spin-rotation (NSR) coupling tensors of molecules containing heavy elements [Y. Xiao and W. Liu, J. Chem. Phys. 138, 134104 (2013)]. While they perform rather similarly, the KB-RLO Ansatz is clearly preferred as it ensures the correct nonrelativistic limit even with a finite basis. Moreover, it gives rise to the same “direct relativistic mapping” between nuclear magnetic resonance shielding and NSR coupling tensors as that without using the London orbitals [Y. Xiao, Y. Zhang, and W. Liu, J. Chem. Theory Comput. 10, 600 (2014)].
NASA Astrophysics Data System (ADS)
Rusakova, I. L.; Rusakov, Yu Yu; Krivdin, L. B.
2016-04-01
The theoretical grounds of the modern relativistic methods for quantum chemical calculation of spin–spin coupling constants in nuclear magnetic resonance spectra are considered. Examples and prospects of application of relativistic calculations of these constants in the structural studies of organic and heteroorganic compounds are discussed. Practical recommendations on relativistic calculations of spin–spin coupling constants using the available software are given. The bibliography includes 622 references.
Radiative Lifetime for Nuclear Spin Conversion of Water-Ion H_2O^+
NASA Astrophysics Data System (ADS)
Tanaka, Keiichi; Harada, Kensuke; Oka, Takeshi
2013-06-01
Nuclear spin conversion interaction of the water ion, H_2O^+, has been studied to derive the spontaneous emission lifetime between the ortho- and para-levels. The H_2O^+ ion is a radical with ^2 B _1 electronic ground state and the off-diagonal electron spin-nuclear spin interaction term, T_{ab} (S_aΔ I_b + S_bΔ I_a), connects para and ortho levels, because Δ {I} = {I}_1 - {I}_2 has nonvanishing matrix elements between I = 0 and 1. The T_{ab} coupling constant, derived by an ab initio calculation in MRD-CI/Bk level to be 72 MHz, is larger than that of H_2O by 4 orders of magnitude, makes the ortho to para conversion of H_2O^+ faster than that of H_2O by 8 orders of magnitude and possibly competitive with other astrophysical processes. Last year we reported ortho and para coupling channels below 900 cm^{-1} caused by accidental near degeneracy of rotational levels. For example, hyperfine components of the 4_{2,2}(o) and 3_{3,0}(p) levels mix each other by 1.2 x 10^{-3} due to the near degeneracy (Δ E = 0.417 cm^{-1}), but the lower lying 1_{0,1}(p) and 1_{1,1}(o) levels mix only by 8.9 x 10^{-5} because of their large separation (Δ E = 16.27 cm^{-1}). In the present study, we solved the radiative rate equations including all the rotational levels below 900 cm^{-1} to give the o-p conversion lifetime to be 0.451, 3.27, 398 and 910 years for the equilibrium o/p ratio of 3.00, 3.00, 4.52, and 406 when the radiation temperature T_r is 100, 60, 20 and 5 K. These results qualitatively help to understand the observed high o/p ratio of 4.8 ± 0.5 (corresponding to the nuclear spin temperature of 21 K) toward Sgr B2, but they are too slow to compete with the reaction by collision unless the number of density of H_2 in the region is very low (n˜1 cm^{-3}) or the radiative temperature is very high (T_r > 50K). K. Tanaka, K. Harada, and T. Oka, the 67th OSU Symposium MG06, 2012. P. Schilke, et al., A&A 521, L11 (2010). K. Tanaka, K. Harada, and T. Oka, J. Phys. Chem. A
A high-performance Fortran code to calculate spin- and parity-dependent nuclear level densities
NASA Astrophysics Data System (ADS)
Sen'kov, R. A.; Horoi, M.; Zelevinsky, V. G.
2013-01-01
A high-performance Fortran code is developed to calculate the spin- and parity-dependent shell model nuclear level densities. The algorithm is based on the extension of methods of statistical spectroscopy and implies exact calculation of the first and second Hamiltonian moments for different configurations at fixed spin and parity. The proton-neutron formalism is used. We have applied the method for calculating the level densities for a set of nuclei in the sd-, pf-, and pf+g- model spaces. Examples of the calculations for 28Si (in the sd-model space) and 64Ge (in the pf+g-model space) are presented. To illustrate the power of the method we estimate the ground state energy of 64Ge in the larger model space pf+g, which is not accessible to direct shell model diagonalization due to the prohibitively large dimension, by comparing with the nuclear level densities at low excitation energy calculated in the smaller model space pf. Program summaryProgram title: MM Catalogue identifier: AENM_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AENM_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 193181 No. of bytes in distributed program, including test data, etc.: 1298585 Distribution format: tar.gz Programming language: Fortran 90, MPI. Computer: Any architecture with a Fortran 90 compiler and MPI. Operating system: Linux. RAM: Proportional to the system size, in our examples, up to 75Mb Classification: 17.15. External routines: MPICH2 (http://www.mcs.anl.gov/research/projects/mpich2/) Nature of problem: Calculating of the spin- and parity-dependent nuclear level density. Solution method: The algorithm implies exact calculation of the first and second Hamiltonian moments for different configurations at fixed spin and parity. The code is parallelized using the Message
WURST-QCPMG sequence and "spin-lock" in 14N nuclear quadrupole resonance
NASA Astrophysics Data System (ADS)
Gregorovič, Alan; Apih, Tomaž
2013-08-01
14N nuclear quadrupole resonance (NQR) is a promising method for the analysis of pharmaceuticals or for the detection of nitrogen based illicit compounds, but so far, the technique is still not widely used, mostly due to the very low sensitivity. This problem is already acute in the preliminary NQR stage, when a compound is being examined for the first time and the NQR frequencies are being searched for, by scanning a wide frequency range step-by-step. In the present work, we experimentally show how to increase the efficiency of this initial stage by using a combination of a wideband excitation achieved with frequency swept pulses (WURST) and a "spin-lock" state obtained with a quadrupolar-CPMG (QCPMG) sequence. In the first part we show that WURST pulses provide a much larger excitation bandwidth compared to common rectangular pulses. This increased bandwidth allows to increase the frequency step and reduces the total number of steps in a scanning stage. In the second part we show that the "spin-lock" decay time T2eff obtained with the WURST-QCPMG combination is practically identical with the T2eff obtained with the most common "spin-lock" sequence, the SLSE, despite a very different nature and length of excitation pulses. This allows for a substantial S/N increase through echo averaging in every individual step and really allows to exploit all the advantages of the wider excitation in the NQR frequency scanning stage. Our experimental results were obtained on a sample of trinitrotoluene, but identical behavior is expected for all compounds where a "spin-lock" state can be created.
Bock, Steffen; Bich, Eckard; Vogel, Eckhard; Dickinson, Alan S; Vesovic, Velisa
2004-09-01
Transport properties of pure carbon dioxide have been calculated from the intermolecular potential using the classical trajectory method. Results are reported in the dilute-gas limit for volume viscosity, depolarized Rayleigh scattering, and nuclear spin relaxation for temperatures ranging from 200 to 1000 K. Three recent carbon dioxide potential energy hypersurfaces have been investigated. Calculated values for the rotational collision number for all three intermolecular surfaces are consistent with the measurements and indicate that the temperature dependence of the Brau-Jonkman correlation is not applicable for carbon dioxide. The results for the depolarized Rayleigh scattering cross section and the nuclear spin relaxation cross section show that calculated values for the generally more successful potentials differ from the observations by 9% at about 290 K, although agreement is obtained for nuclear spin relaxation at about 400 K. PMID:15332957
Křístková, Anežka; Malkin, Vladimir G.; Komorovsky, Stanislav; Repisky, Michal; Malkina, Olga L.
2015-03-21
In this work, we report on the development and implementation of a new scheme for efficient calculation of indirect nuclear spin-spin couplings in the framework of four-component matrix Dirac-Kohn-Sham approach termed matrix Dirac-Kohn-Sham restricted magnetic balance resolution of identity for J and K, which takes advantage of the previous restricted magnetic balance formalism and the density fitting approach for the rapid evaluation of density functional theory exchange-correlation response kernels. The new approach is aimed to speedup the bottleneck in the solution of the coupled perturbed equations: evaluation of the matrix elements of the kernel of the exchange-correlation potential. The performance of the new scheme has been tested on a representative set of indirect nuclear spin-spin couplings. The obtained results have been compared with the corresponding results of the reference method with traditional evaluation of the exchange-correlation kernel, i.e., without employing the fitted electron densities. Overall good agreement between both methods was observed, though the new approach tends to give values by about 4%-5% higher than the reference method. On the average, the solution of the coupled perturbed equations with the new scheme is about 8.5 times faster compared to the reference method.
NASA Astrophysics Data System (ADS)
Harter, William; Mitchell, Justin
2009-06-01
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)
Prediction of Nuclear Masses in the A=80 region of nuclei as a function of P and F-spin
NASA Astrophysics Data System (ADS)
Teymurazyan, A.; Aprahamian, A.; Georgieva, A.
2002-11-01
Predictions of nuclear masses far from stability are one of the challenges to present day network calculations in simulating various astrophysical scenarios and yielding the appropriate elemental abundances. Various groups have shown that complex nuclear structure properties as well as nuclear masses are correlated with the valence number of neutrons and protons. One such parameter is the promiscuity factor P and a related approach is that of F-spin. Both parameters are used to describe known measurements and used to predict via interpolation methods the masses of nuclei presently unknown in the laboratory. Here we show the exact relationship between P and F-spin in an attempt to strengthen structure based prediction methods for nuclear masses of interest in both the rp-process and the r-process.
NASA Astrophysics Data System (ADS)
Cheng, Lan; Gauss, Jürgen; Stanton, John F.
2013-08-01
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 (MO_4^{2-}, M = Cr, Mo, and W) and the 129Xe shieldings of xenon fluorides (XeF2, XeF4, and XeF6).
NASA Astrophysics Data System (ADS)
Thurber, Kent R.; Potapov, Alexey; Yau, Wai-Ming; Tycko, Robert
2013-01-01
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
2012-01-01
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 (Thurber et al., J. Magn. Reson. 2008) [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. PMID:23238592
Ortho-para mixing hyperfine interaction in the H2O+ ion and nuclear spin equilibration.
Tanaka, Keiichi; Harada, Kensuke; Oka, Takeshi
2013-10-01
The ortho to para conversion of water ion, H2O(+), due to the interaction between the magnetic moments of the unpaired electron and protons has been theoretically studied to calculate the spontaneous emission lifetime between the ortho- and para-levels. The electron spin-nuclear spin interaction term, Tab(SaΔIb + SbΔIa) mixes ortho (I = 1) and para (I = 0) levels to cause the "forbidden" ortho to para |ΔI| = 1 transition. The mixing term with Tab = 72.0 MHz is 4 orders of magnitude higher for H2O(+) than for its neutral counterpart H2O where the magnetic field interacting with proton spins is by molecular rotation rather than the free electron. The resultant 10(8) increase of ortho to para conversion rate possibly makes the effect of conversion in H2O(+) measurable in laboratories and possibly explains the anomalous ortho to para ratio recently reported by Herschel heterodyne instrument for the far-infrared (HIFI) observation. Results of our calculations show that the ortho ↔ para mixings involving near-degenerate ortho and para levels are high (∼10(-3)), but they tend to occur at high energy levels, ∼300 K. Because of the rapid spontaneous emission, such high levels are not populated in diffuse clouds unless the radiative temperature of the environment is very high. The low-lying 101 (para) and 111 (ortho) levels of H2O(+) are mixed by ∼10(-4) making the spontaneous emission lifetime for the para 101 → ortho 000 transition 520 years and 5200 years depending on the F value of the hyperfine structure. Thus the ortho ↔ para conversion due to the unpaired electron is not likely to seriously affect thermalization of interstellar H2O(+) unless either the radiative temperature is very high or number density of the cloud is very low. PMID:23530629
Menghetti, L.; Basso, C.; Nava, A.; Angelini, A.; Thiene, G.
1996-01-01
OBJECTIVE: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a myocardial disorder characterised clinically by ventricular arrhythmias that can cause cardiac arrest and morphologically by fatty or fibro-fatty myocardial atrophy of the right ventricle. In vivo tissue characterisation without endomyocardial biopsy would be useful. The aim of this study was to investigate the diagnostic accuracy of spin-echo nuclear magnetic resonance (NMR) for tissue characterisation in ARVC. PATIENTS AND METHODS: Twenty three subjects (15 men and eight women, aged 18-49, mean 34) were studied with spin-echo T1-weighted NMR and multislice scan. Fifteen had a clinical diagnosis of ARVC and eight were controls (age and sex matched subjects). Data were independently evaluated by two expert observers. RESULTS: In the control group NMR was always negative (100% specificity). Ten of the 15 patients with ARVC had an abnormal NMR result (67% sensitivity), with areas that had a signal intensity close to that of pericardial or subcutaneous fat. In the remaining five cases the NMR signal was inadequate. Nine patients underwent both NMR and endomyocardial biopsy; biopsy was positive in eight (89%) and NMR was positive in five (56%). CONCLUSIONS: NMR is a useful non-invasive diagnostic tool in the evaluation of fatty replacement in ARVC. The technique can be used with other procedures in the initial diagnostic evaluation and is a useful alternative tool in the long term follow up of patients with ARVC. Images PMID:9014792
Nuclear spin relaxation of {sup 129}Xe due to persistent xenon dimers
Berry-Pusey, B. N.; Anger, B. C.; Laicher, G.; Saam, B.
2006-12-15
We have measured longitudinal nuclear relaxation rates of {sup 129}Xe in Xe-N{sub 2} mixtures at densities below 0.5 amagats in a magnetic field of 8.0 T. We find that intrinsic spin relaxation in this regime is principally due to fluctuations in the intramolecular spin-rotation (SR) and chemical-shift-anisotropy (CSA) interactions, mediated by the formation of {sup 129}Xe-Xe persistent dimers. Our results are consistent with previous work done in one case at much lower applied fields where the CSA interaction is negligible and in another case at much higher gas densities where transient xenon dimers mediate the interactions. We have verified that a large applied field suppresses the persistent-dimer mechanism, consistent with standard relaxation theory, allowing us to measure room-temperature gas-phase relaxation times T{sub 1} for {sup 129}Xe greater than 25 h at 8.0 T. These data also yield a maximum possible low-field T{sub 1} for pure xenon gas at room temperature of 5.45{+-}0.2 h. The coupling strengths for the SR and CSA interactions that we extract are in fair agreement with estimates based both on previous experimental work and on ab initio calculations. Our results have potential implications for the production and storage of large quantities of hyperpolarized {sup 129}Xe for use in various applications.
NASA Astrophysics Data System (ADS)
Aucar, Ignacio A.; Gómez, Sergio S.; de Azúa, Martín C. Ruiz; Giribet, Claudia G.
2012-05-01
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.
NASA Astrophysics Data System (ADS)
Aslam, Nabeel; Pfender, Matthias; Zaiser, Sebastian; Favaro de Oliveira, Felipe; Momenzadeh, S. Ali; Denisenko, Andrej; Isoya, Junichi; Neumann, Philipp; Wrachtrup, Joerg
Recently nuclear magnetic resonance (NMR) of nanoscale samples at ambient conditions has been achieved with nitrogen-vacancy (NV) centers in diamond. So far the spectral resolution in the NV NMR experiments was limited by the sensor's coherence time, which in turn prohibited revealing the chemical composition and dynamics of the system under investigation. By entangling the NV electron spin sensor with a long-lived memory spin qubit we increase the spectral resolution of NMR measurement sequences for the detection of external nuclear spins. Applying the latter sensor-memory-couple it is particularly easy to track diffusion processes, to identify the molecules under study and to deduce the actual NV center depth inside the diamond. We performed nanoscale NMR on several liquid and solid samples exhibiting unique NMR response. Our method paves the way for nanoscale identification of molecule and protein structures and dynamics of conformational changes.
Heckmann, J.; Meyer, W.; Radtke, E.; Reicherz, G.; Goertz, S.
2006-10-01
ESR spectroscopy is an important tool in polarized solid target material research, since it allows us to study the paramagnetic centers, which are used for the dynamic nuclear polarization (DNP). The polarization behavior of the different target materials is strongly affected by the properties of these centers, which are added to the diamagnetic materials by chemical doping or irradiation. In particular, the ESR linewidth of the paramagnetic centers is a very important parameter, especially concerning the deuterated target materials. In this paper, the results of the first precise ESR measurements of the deuterated target materials at a DNP-relevant magnetic field of 2.5 T are presented. Moreover, these results allowed us to experimentally study the correlation between ESR linewidth and maximum deuteron polarization, as given by the spin-temperature theory.
Pulsed NMR in the nuclear spin ordered phases of solid 3He in a silver sinter
NASA Astrophysics Data System (ADS)
Millan-Chacartegui, Carmen; Schuberth, Erwin A.; Deppe, Frank; Schöttl, Stephan
2003-05-01
To obtain the exact spin structure of the nuclear magnetically ordered phases of solid 3He, in the BCC lattice called U2D2 and high field phase, both occurring below about 1 mK, we started a project of neutron scattering from the solid at the Hahn-Meitner Institut, Berlin. This experiment faces three main difficulties: to cool the solid to temperatures below 1 mK (or even much lower in the case of the HCP lattice), to keep it there under neutron flux, and to grow a single crystal within the sintered material needed for this purpose. As a first step we have performed pulsed NMR measurements in the ordered phases of solid 3He in a silver sinter of 700 Å particle size down to temperatures of 600 μK at various molar volumes. The samples remained in the ordered state for as long as 110 h.
Nonlinear radiation damping of nuclear spin waves and magnetoelastic waves in antiferromagnets
NASA Astrophysics Data System (ADS)
Andrienko, Alexander V.; Safonov, Vladimir L.
2016-03-01
Parallel pumping of nuclear spin waves in antiferromagnetic CsMnF3 at liquid helium temperatures and magnetoelastic waves in antiferromagnetic FeBO3 at liquid nitrogen temperature in a helical resonator was studied. It was found that the absorbed microwave power is approximately equal to the irradiated power from the sample and that the main restriction mechanism of absorption in both cases is defined by the nonlinear radiation damping predicted about two decades ago. Nonlinear radiation damping is sure to be a common feature of the parallel pumping technique for all normal magnetic excitations and it must be taken into account for interpretation of nonlinear phenomena in parametrically excited magnetic systems.
NASA Astrophysics Data System (ADS)
Meriles, C. A.; Pérez, S. C.; Brunetti, A. H.
1997-08-01
p-chloronitrobenzene (PCNB) and p-chlorobromobenzene (PCBB) crystallize in the centrosymmetric space group P21/c with two molecules per unit cell. The space lattice will have an equal number of points with molecules facing in opposite directions. As a consequence, these compounds exhibit an orientational rigid disorder. In this work, we have measured the temperature dependence of the chlorine nuclear quadrupole spin-lattice relaxation time (T1), linewidth, and resonance frequency for both compounds for temperatures higher than 80 K. Both compounds exhibit an inhomogeneously broadened line shape and a "normal" Bayer-type temperature dependence of the resonance frequency. The analysis focuses on the identification of the dominant relaxation process at high temperatures (T>240 K in PCNB and T>260 K in PCBB). It is shown that T1(T) reflects the existence of 180° molecular reorientations through a modulation of the crystalline contribution to the electric field gradient.
Features of influence of dc magnetic field pulses on a nuclear spin echo in magnets
NASA Astrophysics Data System (ADS)
Mamniashvili, G. I.; Gegechkori, T. O.; Akhalkatsi, A. M.; Gavasheli, C. A.
2012-06-01
Signal intensities of a two-pulse nuclear spin echo as a function of parameters of dc magnetic field pulses are measured in the series of materials: Li0.5Fe2.5-xZnxO4 (x < 0.25) (enriched in 57Fe isotope to 96.8%), NiMnSb, Co2MnSi, La1-хСахMnO3 (x = 0.2; 0.25) and polycrystalline Co. Two types of dependences of these signals on a supplying time of such pulses with respect to the times of the exciting RF pulses are found. The mechanisms of influence of a domain structure and a dynamic frequency shift on the observed features of the investigated signals are discussed.
NASA Astrophysics Data System (ADS)
Mentink-Vigier, Frédéric; Binet, Laurent; Vignoles, Gerard; Gourier, Didier; Vezin, Hervé
2010-11-01
The hyperfine interactions of the unpaired electron with eight surrounding G69a and G71a nuclei in Ti-doped β-Ga2O3 were analyzed by electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopies. They are dominated by strong isotropic hyperfine couplings due to a direct Fermi contact interaction with Ga nuclei in octahedral sites of rutile-type chains oriented along b axis, revealing a large anisotropic spatial extension of the electron wave function. Titanium in β-Ga2O3 is thus best described as a diffuse (Ti4+-e-) pair rather than as a localized Ti3+ . Both electron and G69a nuclear spin Rabi oscillations could be observed by pulsed EPR and pulsed ENDOR, respectively. The electron spin decoherence time is about 1μs (at 4 K) and an upper bound of 520μs (at 8 K) is estimated for the nuclear decoherence time. Thus, β-Ga2O3:Ti appears to be a potential spin-bus system for quantum information processing with a large nuclear spin quantum register.
Nuclear spin imaging with hyperpolarized nuclei created by brute force method
NASA Astrophysics Data System (ADS)
Tanaka, Masayoshi; Kunimatsu, Takayuki; Fujiwara, Mamoru; Kohri, Hideki; Ohta, Takeshi; Utsuro, Masahiko; Yosoi, Masaru; Ono, Satoshi; Fukuda, Kohji; Takamatsu, Kunihiko; Ueda, Kunihiro; Didelez, Jean-P.; Prossati, Giorgio; de Waard, Arlette
2011-05-01
We have been developing a polarized HD target for particle physics at the SPring-8 under the leadership of the RCNP, Osaka University for the past 5 years. Nuclear polarizaton is created by means of the brute force method which uses a high magnetic field (~17 T) and a low temperature (~ 10 mK). As one of the promising applications of the brute force method to life sciences we started a new project, "NSI" (Nuclear Spin Imaging), where hyperpolarized nuclei are used for the MRI (Magnetic Resonance Imaging). The candidate nuclei with spin ½hslash are 3He, 13C, 15N, 19F, 29Si, and 31P, which are important elements for the composition of the biomolecules. Since the NMR signals from these isotopes are enhanced by orders of magnitudes, the spacial resolution in the imaging would be much more improved compared to the practical MRI used so far. Another advantage of hyperpolarized MRI is that the MRI is basically free from the radiation, while the problems of radiation exposure caused by the X-ray CT or PET (Positron Emission Tomography) cannot be neglected. In fact, the risk of cancer for Japanese due to the radiation exposure through these diagnoses is exceptionally high among the advanced countries. As the first step of the NSI project, we are developing a system to produce hyperpolarized 3He gas for the diagnosis of serious lung diseases, for example, COPD (Chronic Obstructive Pulmonary Disease). The system employs the same 3He/4He dilution refrigerator and superconducting solenoidal coil as those used for the polarized HD target with some modification allowing the 3He Pomeranchuk cooling and the following rapid melting of the polarized solid 3He to avoid the depolarization. In this report, the present and future steps of our project will be outlined with some latest experimental results.
NASA Astrophysics Data System (ADS)
Wu, Zhe-Ying; Qi, Chong; Wyss, Ramon; Liu, Hong-Liang
2015-08-01
Background: The deviation between different model calculations that may occur when one goes toward regions where the masses are unknown is getting increased attention. This is related to the uncertainties of the different models which may have not been fully understood. Purpose: To explore in detail the effect of the isospin dependence of the spin-orbital force in the Woods-Saxon potential on global binding energy and deformation calculations. Method: The microscopic energies and nuclear deformations of about 1850 even-even nuclei are calculated systematically within the macroscopic-microscopic framework using three Woods-Saxon parametrizations, with different isospin dependencies, which were constructed mainly for nuclear spectroscopy calculations. Calculations are performed in the deformation space (β2,γ ,β4) . Both the monopole and doubly stretched quadrupole interactions are considered for the pairing channel. Results: The ground-state deformations obtained by the three calculations are quite similar to each other. Large differences are seen mainly in neutron-rich nuclei and in superheavy nuclei. Systematic calculations on the shape-coexisting second minima are also presented. As for the microscopic energies of the ground states, the results are also very close to each other. Only in a few cases the difference is larger than 2 MeV. The total binding energy is estimated by adding the macroscopic energy provided by the usual liquid drop model with its parameters fitted through the least square root and minimax criteria. Calculations are also compared with the results of other macroscopic-microscopic mass models. Conclusions: All the three calculations give similar values for the deformations, microscopic energies, and binding energies of most nuclei. One may expect to have a better understanding of the isospin dependence of the spin-orbital force with more data on proton- and neutron-rich nuclei.
Optically addressable nuclear spins in a solid with a six-hour coherence time.
Zhong, Manjin; Hedges, Morgan P; Ahlefeldt, Rose L; Bartholomew, John G; Beavan, Sarah E; Wittig, Sven M; Longdell, Jevon J; Sellars, Matthew J
2015-01-01
Space-like separation of entangled quantum states is a central concept in fundamental investigations of quantum mechanics and in quantum communication applications. Optical approaches are ubiquitous in the distribution of entanglement because entangled photons are easy to generate and transmit. However, extending this direct distribution beyond a range of a few hundred kilometres to a worldwide network is prohibited by losses associated with scattering, diffraction and absorption during transmission. A proposal to overcome this range limitation is the quantum repeater protocol, which involves the distribution of entangled pairs of optical modes among many quantum memories stationed along the transmission channel. To be effective, the memories must store the quantum information encoded on the optical modes for times that are long compared to the direct optical transmission time of the channel. Here we measure a decoherence rate of 8 × 10(-5) per second over 100 milliseconds, which is the time required for light transmission on a global scale. The measurements were performed on a ground-state hyperfine transition of europium ion dopants in yttrium orthosilicate ((151)Eu(3+):Y2SiO5) using optically detected nuclear magnetic resonance techniques. The observed decoherence rate is at least an order of magnitude lower than that of any other system suitable for an optical quantum memory. Furthermore, by employing dynamic decoupling, a coherence time of 370 ± 60 minutes was achieved at 2 kelvin. It has been almost universally assumed that light is the best long-distance carrier for quantum information. However, the coherence time observed here is long enough that nuclear spins travelling at 9 kilometres per hour in a crystal would have a lower decoherence with distance than light in an optical fibre. This enables some very early approaches to entanglement distribution to be revisited, in particular those in which the spins are transported rather than the light
Fractionated Mercury Isotopes in Fish: The Effects of Nuclear Mass, Spin, and Volume
NASA Astrophysics Data System (ADS)
Das, R.; Odom, A. L.
2007-12-01
.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 Δ199Hg than in Δ201Hg 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 Δ201Hg /Δ199Hg 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.
Schmiedt, Hanno; Jensen, Per; Schlemmer, Stephan
2016-08-21
In modern physics and chemistry concerned with many-body systems, one of the mainstays is identical-particle-permutation symmetry. In particular, both the intra-molecular dynamics of a single molecule and the inter-molecular dynamics associated, for example, with reactive molecular collisions are strongly affected by selection rules originating in nuclear-permutation symmetry operations being applied to the total internal wavefunctions, including nuclear spin, of the molecules involved. We propose here a general tool to determine coherently the permutation symmetry and the rotational symmetry (associated with the group of arbitrary rotations of the entire molecule in space) of molecular wavefunctions, in particular the nuclear-spin functions. Thus far, these two symmetries were believed to be mutually independent and it has even been argued that under certain circumstances, it is impossible to establish a one-to-one correspondence between them. However, using the Schur-Weyl duality theorem we show that the two types of symmetry are inherently coupled. In addition, we use the ingenious representation-theory technique of Young tableaus to represent the molecular nuclear-spin degrees of freedom in terms of well-defined mathematical objects. This simplifies the symmetry classification of the nuclear wavefunction even for large molecules. Also, the application to reactive collisions is very straightforward and provides a much simplified approach to obtaining selection rules. PMID:27544099
Field-induced spin reorientation in [Fe/Cr ] n multilayers studied by nuclear resonance reflectivity
NASA Astrophysics Data System (ADS)
Andreeva, M.; Gupta, A.; Sharma, G.; Kamali, S.; Okada, K.; Yoda, Y.
2015-10-01
We present depth-resolved nuclear resonance reflectivity studies of the magnetization evolution in [57Fe(3nm ) /Cr (1.2 nm ) ] 10 multilayer under applied external field. The measurements have been performed at the station BL09XU of SPring-8 at different values of the external field (0-1500 Oe). We apply the joint fit of the delayed reflectivity curves and the time spectra of the nuclear resonance reflectivity measured at different grazing angles for enhancement of the depth resolution and reliability of results. We show that the azimuth angle, which is used in all papers devoted to the magnetization profile determination, has a more complicated physical sense due to the partially coherent averaging of the scattering amplitudes from magnetic lateral domains. We describe how to select the true azimuth angle from the determined "effective azimuth angle." Finally we obtain the noncollinear twisted magnetization depth profiles where the spin-flop state appears sequentially in different 57Fe layers at increasing applied field.
NASA Astrophysics Data System (ADS)
Robin, Caroline; Litvinova, Elena
2016-07-01
A new theoretical approach to spin-isospin excitations in open-shell nuclei is presented. The developed method is based on the relativistic meson-exchange nuclear Lagrangian of Quantum Hadrodynamics and extends the response theory for superfluid nuclear systems beyond relativistic quasiparticle random phase approximation in the proton-neutron channel (pn-RQRPA). The coupling between quasiparticle degrees of freedom and collective vibrations (phonons) introduces a time-dependent effective interaction, in addition to the exchange of pion and ρ -meson taken into account without retardation. The time-dependent contributions are treated in the resonant time-blocking approximation, in analogy to the previously developed relativistic quasiparticle time-blocking approximation (RQTBA) in the neutral (non-isospin-flip) channel. The new method is called proton-neutron RQTBA (pn-RQTBA) and is applied to the Gamow-Teller resonance in a chain of neutron-rich nickel isotopes 68-78Ni . A strong fragmentation of the resonance along with quenching of the strength, as compared to pn-RQRPA, is obtained. Based on the calculated strength distribution, beta-decay half-lives of the considered isotopes are computed and compared to pn-RQRPA half-lives and to experimental data. It is shown that a considerable improvement of the half-life description is obtained in pn-RQTBA because of the spreading effects, which bring the lifetimes to a very good quantitative agreement with data.
NASA Astrophysics Data System (ADS)
Yan, Li-Ping; Kurosawa, Masahiro; Hsu, Wei-Ting; Chang, Wen-Hao; Adachi, Satoru
2015-03-01
Longitudinal and in-plane electron g-factors, and a nuclear spin polarization (NSP) have been evaluated precisely in a CdTe/Cd0.85Mg0.15Te single quantum well by using the time-resolved Kerr rotation and double lock-in detection techniques. Resident electron spin polarization (RESP) was formed via the negative trion formation and recombination, and RESP gave rise to NSP in an oblique magnetic field configuration. We observed the effective nuclear field of a few mT which was weak compared with that in III-V semiconductor nanostructures as expected, but the nuclear field can be converted to the maximal NSP of 12% in Faraday geometry.
NASA Astrophysics Data System (ADS)
Pourfathi, M.; Kuzma, N. N.; Kara, H.; Ghosh, R. K.; Shaghaghi, H.; Kadlecek, S. J.; Rizi, R. R.
2013-10-01
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 129Xe 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 129Xe signals in the clusters as well as the apparent discontinuity of 129Xe 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 129Xe 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.
Nuclear energy surfaces at high-spin in the A{approximately}180 mass region
Chasman, R.R.; Egido, J.L.; Robledo, L.M.
1995-08-01
We are studying nuclear energy surfaces at high spin, with an emphasis on very deformed shapes using two complementary methods: (1) the Strutinsky method for making surveys of mass regions and (2) Hartree-Fock calculations using a Gogny interaction to study specific nuclei that appear to be particularly interesting from the Strutinsky method calculations. The great advantage of the Strutinsky method is that one can study the energy surfaces of many nuclides ({approximately}300) with a single set of calculations. Although the Hartree-Fock calculations are quite time-consuming relative to the Strutinsky calculations, they determine the shape at a minimum without being limited to a few deformation modes. We completed a study of {sup 182}Os using both approaches. In our cranked Strutinsky calculations, which incorporate a necking mode deformation in addition to quadrupole and hexadecapole deformations, we found three well-separated, deep, strongly deformed minima. The first is characterized by nuclear shapes with axis ratios of 1.5:1; the second by axis ratios of 2.2:1 and the third by axis ratios of 2.9:1. We also studied this nuclide with the density-dependent Gogny interaction at I = 60 using the Hartree-Fock method and found minima characterized by shapes with axis ratios of 1.5:1 and 2.2:1. A comparison of the shapes at these minima, generated in the two calculations, shows that the necking mode of deformation is extremely useful for generating nuclear shapes at large deformation that minimize the energy. The Hartree-Fock calculations are being extended to larger deformations in order to further explore the energy surface in the region of the 2.9:1 minimum.
NASA Astrophysics Data System (ADS)
Mananga, Eugene Stephane; Charpentier, Thibault
2015-04-01
In this paper we present a theoretical perturbative approach for describing the NMR spectrum of strongly dipolar-coupled spin systems under fast magic-angle spinning. Our treatment is based on two approaches: the Floquet approach and the Floquet-Magnus expansion. The Floquet approach is well known in the NMR community as a perturbative approach to get analytical approximations. Numerical procedures are based on step-by-step numerical integration of the corresponding differential equations. The Floquet-Magnus expansion is a perturbative approach of the Floquet theory. Furthermore, we address the " γ -encoding" effect using the Floquet-Magnus expansion approach. We show that the average over " γ " angle can be performed for any Hamiltonian with γ symmetry.
Microwave field distribution in a magic angle spinning dynamic nuclear polarization NMR probe
NASA Astrophysics Data System (ADS)
Nanni, Emilio A.; Barnes, Alexander B.; Matsuki, Yoh; Woskov, Paul P.; Corzilius, Björn; Griffin, Robert G.; Temkin, Richard J.
2011-05-01
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 μT/W 1/2, where S denotes the electron spin. For a routinely achievable input power of 5 W the corresponding value is γSB 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 ( ɛ) vs. ω1 S/(2 π) 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.
Shell-model study of spin modes in nuclei and nuclear forces
NASA Astrophysics Data System (ADS)
Suzuki, Toshio; Otsuka, Takaharu; Honma, Michio; Tsunoda, Naofumi
2015-02-01
Spin-dependent modes in nuclei are studied by shell-model method with the use of new shell-model Hamiltonians which properly take into account important roles of tensor interactions. New Hamiltonians can describe spin degrees of freedom in nuclei remarkably well. Nuclear weak processes at stellar environments are investigated based on these successes. New neutrino-nucleus reaction cross sections on 12C are applied to light-element synthesis in supernova explosions. The production rate for 11B/7Li is pointed out to be useful to determine v-oscillation parameters, in particular, v-mass hierarchy. New e-capture rates in Ni isotopes are obtained and implications for element synthesis are discussed. The monopole-based universal interaction is applied to study structure of p-sd shell nuclei and 40Ar as well as v-induced reactions on 40Ar. Repulsive corrections in the isospin T=1 monopoles are shown to be important for proper shell evolutions in neutron-rich carbon isotopes. The repulsive correction is pointed out to be due to three-body forces, in particular, the Fujita-Miyazawa force. Roles of the three-body forces on the shell evolution of neutron-rich calcium isotopes, the closed- shell nature of 48 Ca and M1 transition in 48 Ca are studied on top of the two-body G-matrix obtained by including core-polarization effects in larger spaces (<=24hslashω). Effects of the inclusion of g9/2-shell are also discussed.
Microwave field distribution in a magic angle spinning dynamic nuclear polarization NMR probe.
Nanni, Emilio A; Barnes, Alexander B; Matsuki, Yoh; Woskov, Paul P; Corzilius, Björn; Griffin, Robert G; Temkin, Richard J
2011-05-01
We present a calculation of the microwave field distribution in a magic angle spinning (MAS) probe utilized in dynamic nuclear polarization (DNP) experiments. The microwave magnetic field (B(1S)) profile was obtained from simulations performed with the High Frequency Structure Simulator (HFSS) software suite, using a model that includes the launching antenna, the outer Kel-F stator housing coated with Ag, the RF coil, and the 4mm diameter sapphire rotor containing the sample. The predicted average B(1S) field is 13μT/W(1/2), where S denotes the electron spin. For a routinely achievable input power of 5W the corresponding value is γ(S)B(1S)=0.84MHz. The calculations provide insights into the coupling of the microwave power to the sample, including reflections from the RF coil and diffraction of the power transmitted through the coil. The variation of enhancement with rotor wall thickness was also successfully simulated. A second, simplified calculation was performed using a single pass model based on Gaussian beam propagation and Fresnel diffraction. This model provided additional physical insight and was in good agreement with the full HFSS simulation. These calculations indicate approaches to increasing the coupling of the microwave power to the sample, including the use of a converging lens and fine adjustment of the spacing of the windings of the RF coil. The present results should prove useful in optimizing the coupling of microwave power to the sample in future DNP experiments. Finally, the results of the simulation were used to predict the cross effect DNP enhancement (ϵ) vs. ω(1S)/(2π) for a sample of (13)C-urea dissolved in a 60:40 glycerol/water mixture containing the polarizing agent TOTAPOL; very good agreement was obtained between theory and experiment. PMID:21382733
Microwave Field Distribution in a Magic Angle Spinning Dynamic Nuclear Polarization NMR Probe
Nanni, Emilio A.; Barnes, Alexander B.; Matsuki, Yoh; Woskov, Paul P.; Corzilius, Björn; Griffin, Robert G.; Temkin, Richard J.
2011-01-01
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 (B1S) 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 B1S field is 13µT/W1/2, where S denotes the electron spin. For a routinely achievable input power of 5 W the corresponding value is γ SB1S = 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 (ε) vs. ω1S/(2π) 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. PMID:21382733
Soubies, B.; Henry, J.Y.; Le Meur, M.
1995-04-01
1300 MWe pressurised water reactors (PWRs), like the 1400 MWe reactors, operate with microprocessor-based safety systems. This is particularly the case for the Digital Integrated Protection System (SPIN), which trips the reactor in an emergency and sets in action the safeguard functions. The softwares used in these systems must therefore be highly dependable in the execution of their functions. In the case of SPIN, three players are working at different levels to achieve this goal: the protection system manufacturer, Merlin Gerin; the designer of the nuclear steam supply system, Framatome; the operator of the nuclear power plants, Electricite de France (EDF), which is also responsible for the safety of its installations. Regulatory licenses are issued by the French safety authority, the Nuclear Installations Safety Directorate (French abbreviation DSIN), subsequent to a successful examination of the technical provisions adopted by the operator. This examination is carried out by the IPSN and the standing group on nuclear reactors. This communication sets out: the methods used by the manufacturer to develop SPIN software for the 1400 MWe PWRs (N4 series); the approach adopted by the IPSN to evaluate the safety software of the protection system for the N4 series of reactors.
NASA Astrophysics Data System (ADS)
Clevenson, Hannah; Chen, Edward; Dolde, Florian; Teale, Carson; Englund, Dirk; Braje, Danielle
2016-05-01
We report on detailed studies of electronic and nuclear spin states in the diamond nitrogen vacancy (NV) center under moderate transverse magnetic fields. We numerically predict and experimentally verify a previously unobserved NV ground state hyperfine anti-crossing occurring at magnetic bias fields as low as tens of Gauss - two orders of magnitude lower than previously reported hyperfine anti-crossings at ~ 510 G and ~ 1000 G axial magnetic fields. We then discuss how this regime can be optimized for magnetometry and other sensing applications and propose a method for how the nitrogen-vacancy ground state Hamiltonian can be manipulated by small transverse magnetic fields to polarize the nuclear spin state. Acknowlegement: The Lincoln Laboratory portion of this work is sponsored by the Assistant Secretary of Defense for Research & Engineering under Air Force Contract #FA8721-05-C-0002. Opinions, interpretations, conclusions and recommendations are those of the authors and are not necessarily endorsed by the United States Government.
Infrared spectroscopic investigation of nuclear spin conversion in solid CH{sub 4}
Sugimoto, Takeru; Yamakawa, Koichiro Arakawa, Ichiro
2015-12-14
Infrared spectra of solid CH{sub 4} were studied in the ν{sub 3} and ν{sub 4} vibrational regions. The phase I crystal around 30 K showed broad absorption bands, whereas the phase II crystal at 6.9–10.3 K exhibited splitting of these bands after annealing above 20 K. The split peaks were assigned to the librating and almost freely rotating molecules in phase II on the basis of the peak spacings and time evolution of the peak intensities. From the quantitative analysis of the temporal changes of the R(0) and R(1) peak intensities, the relaxation rates of the numbers of molecules with J = 0 (I = 2) and J = 1 (I = 1) were determined in the temperature range of 6.9–10.3 K. We fitted the function resulting from a combination of direct and indirect relaxation processes mediated by phonons to the temperature dependence of these rates and obtained the activation energies of the indirect process: C ≃ 36 K. Since this value is higher than the energies of perturbed J = 2 states relative to the J = 1 state, we argue that the nuclear spin conversion through the J = 3 state also takes place.
Nuclear spin dependence of the reaction of H(3)+ with H2. II. Experimental measurements.
Crabtree, Kyle N; Kauffman, Carrie A; Tom, Brian A; Beçka, Eftalda; McGuire, Brett A; McCall, Benjamin J
2011-05-21
The nuclear spin dependence of the chemical reaction H(3)(+)+ H(2) → H(2) + H(3)(+) has been studied in a hollow cathode plasma cell. Multipass infrared direct absorption spectroscopy has been employed to monitor the populations of several low-energy rotational levels of ortho- and para-H(3)(+) (o-H(3)(+) and p-H(3)(+)) in hydrogenic plasmas of varying para-H(2) (p-H(2)) enrichment. The ratio of the rates of the proton hop (k(H)) and hydrogen exchange (k(E)) reactions α ≡ k(H)/k(E) is inferred from the observed p-H(3)(+) fraction as a function of p-H(2) fraction using steady-state chemical models. Measurements have been performed both in uncooled (T(kin) ∼ 350 K) and in liquid-nitrogen-cooled (T(kin) ∼ 135 K) plasmas, marking the first time this reaction has been studied at low temperature. The value of α has been found to decrease from 1.6 ± 0.1 at 350 K to 0.5 ± 0.1 at 135 K. PMID:21599063
Infrared spectroscopic investigation of nuclear spin conversion in solid CH4
NASA Astrophysics Data System (ADS)
Sugimoto, Takeru; Yamakawa, Koichiro; Arakawa, Ichiro
2015-12-01
Infrared spectra of solid CH4 were studied in the ν3 and ν4 vibrational regions. The phase I crystal around 30 K showed broad absorption bands, whereas the phase II crystal at 6.9-10.3 K exhibited splitting of these bands after annealing above 20 K. The split peaks were assigned to the librating and almost freely rotating molecules in phase II on the basis of the peak spacings and time evolution of the peak intensities. From the quantitative analysis of the temporal changes of the R(0) and R(1) peak intensities, the relaxation rates of the numbers of molecules with J = 0 (I = 2) and J = 1 (I = 1) were determined in the temperature range of 6.9-10.3 K. We fitted the function resulting from a combination of direct and indirect relaxation processes mediated by phonons to the temperature dependence of these rates and obtained the activation energies of the indirect process: C ≃ 36 K. Since this value is higher than the energies of perturbed J = 2 states relative to the J = 1 state, we argue that the nuclear spin conversion through the J = 3 state also takes place.
Cryogenic sample exchange NMR probe for magic angle spinning dynamic nuclear polarization
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
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. PMID:19356957
Spin-mapping of coal structures with ESE and ENDOR (Electron-Nuclear Double Resonance)
Belford, R.L.; Clarkson, R.B.
1989-03-01
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.
NASA Astrophysics Data System (ADS)
Hackmann, J.; Glasenapp, Ph.; Greilich, A.; Bayer, M.; Anders, F. B.
2015-11-01
The real-time spin dynamics and the spin noise spectra are calculated for p and n -charged quantum dots within an anisotropic central spin model extended by additional nuclear electric quadrupolar interactions and augmented by experimental data. Using realistic estimates for the distribution of coupling constants including an anisotropy parameter, we show that the characteristic long time scale is of the same order for electron and hole spins strongly determined by the quadrupolar interactions even though the analytical form of the spin decay differs significantly consistent with our measurements. The low frequency part of the electron spin noise spectrum is approximately 1 /3 smaller than those for hole spins as a consequence of the spectral sum rule and the different spectral shapes. This is confirmed by our experimental spectra measured on both types of quantum dot ensembles in the low power limit of the probe laser.
NASA Astrophysics Data System (ADS)
Chalupský, Jakub; Yanai, Takeshi
2013-11-01
The derivation, implementation, and validation of a new approximation to the two-electron spin-orbit coupling (SOC) terms is reported. The approximation, referred to as flexible nuclear screening spin-orbit, is based on the effective one-electron spin-orbit operator and accounts for two-electron SOC effects by screening nuclear charges. A highly flexible scheme for the nuclear screening is developed, mainly using parameterization based on ab initio atomic SOC calculations. Tabulated screening parameters are provided for contracted and primitive Gaussian-type basis functions of the ANO-RCC basis set for elements from H to Cm. The strategy for their adaptation to any other Gaussian basis set is presented and validated. A model to correct for the effect of splitting of transition metal d orbitals on their SOC matrix elements is introduced. The method is applied to a representative set of molecules, and compared to exact treatment and other approximative approaches at the same level of relativistic theory. The calculated SOC matrix elements are in very good agreement with their "exact" values; deviation below 1% is observed on average. The presented approximation is considered to be generally applicable, simple to implement, highly efficient, and accurate.
Nozirov, Farhod E-mail: farhod.nozirov@gmail.com; Stachów, Michał; Kupka, Teobald E-mail: farhod.nozirov@gmail.com
2014-04-14
A theoretical prediction of nuclear magnetic shieldings and indirect spin-spin coupling constants in 1,1-, cis- and trans-1,2-difluoroethylenes is reported. The results obtained using density functional theory (DFT) combined with large basis sets and gauge-independent atomic orbital calculations were critically compared with experiment and conventional, higher level correlated electronic structure methods. Accurate structural, vibrational, and NMR parameters of difluoroethylenes were obtained using several density functionals combined with dedicated basis sets. B3LYP/6-311++G(3df,2pd) optimized structures of difluoroethylenes closely reproduced experimental geometries and earlier reported benchmark coupled cluster results, while BLYP/6-311++G(3df,2pd) produced accurate harmonic vibrational frequencies. The most accurate vibrations were obtained using B3LYP/6-311++G(3df,2pd) with correction for anharmonicity. Becke half and half (BHandH) density functional predicted more accurate {sup 19}F isotropic shieldings and van Voorhis and Scuseria's τ-dependent gradient-corrected correlation functional yielded better carbon shieldings than B3LYP. A surprisingly good performance of Hartree-Fock (HF) method in predicting nuclear shieldings in these molecules was observed. Inclusion of zero-point vibrational correction markedly improved agreement with experiment for nuclear shieldings calculated by HF, MP2, CCSD, and CCSD(T) methods but worsened the DFT results. The threefold improvement in accuracy when predicting {sup 2}J(FF) in 1,1-difluoroethylene for BHandH density functional compared to B3LYP was observed (the deviations from experiment were −46 vs. −115 Hz)
NASA Astrophysics Data System (ADS)
Manca Tanner, Carine; Quack, Martin; Schmidiger, David
2013-10-01
We report high resolution near-infrared laser spectra of water seeded in a supersonic jet expansion of argon probed by cavity ring-down spectroscopy (CRDS) in the R branch of the 2-3 band (above 7500 cm-1) at several effective temperatures T < 30 K. Our goal is to study nuclear spin symmetry conservation and relaxation. For low mole fractions of water in the gas mixture, we obtained the lowest rotational temperatures and observed nuclear spin symmetry conservation, in agreement with theoretical expectation for inelastic collisions of isolated H2O molecules with Ar and similar to a previous series of experiments with other small molecules in supersonic jet expansions. However, for the highest mole fractions of water, which we used (xH2O < 1.6%), we obtained slightly higher rotational temperatures and observed nuclear spin symmetry relaxation, which cannot be explained by the intramolecular quantum relaxation mechanism in the monomer H2O. The nuclear spin symmetry relaxation observed is, indeed, seen to be related to the formation of water clusters at the early stage of the supersonic jet expansion. Under these conditions, two mechanisms can contribute to nuclear spin symmetry relaxation. The results are discussed in relation to claims of the stability of nuclear spin isomers of H2O in the condensed phase and briefly also to astrophysical spectroscopy.
Nuclear spin of odd-odd α emitters based on the behavior of α -particle preformation probability
NASA Astrophysics Data System (ADS)
Ismail, M.; Adel, A.; Botros, M. M.
2016-05-01
The preformation probabilities of an α cluster inside radioactive parent nuclei for both odd-even and odd-odd nuclei are investigated. The calculations cover the isotopic chains from Ir to Ac in the mass regions 166 ≤A ≤215 and 77 ≤Z ≤89 . The calculations are employed in the framework of the density-dependent cluster model. A realistic density-dependent nucleon-nucleon (N N ) interaction with a finite-range exchange part is used to calculate the microscopic α -nucleus potential in the well-established double-folding model. The main effect of antisymmetrization under exchange of nucleons between the α and daughter nuclei has been included in the folding model through the finite-range exchange part of the N N interaction. The calculated potential is then implemented to find both the assault frequency and the penetration probability of the α particle by means of the Wentzel-Kramers-Brillouin approximation in combination with the Bohr-Sommerfeld quantization condition. The correlation of the α -particle preformation probability and the neutron and proton level sequences of the parent nucleus as obtained in our previous work is extended to odd-even and odd-odd nuclei to determine the nuclear spin and parities. Two spin coupling rules are used, namely, strong and weak rules to determine the nuclear spin for odd-odd isotopes. This work can be a useful reference for theoretical calculation of undetermined nuclear spin of odd-odd nuclei in the future.
McCarney, Evan R; Armstrong, Brandon D; Kausik, Ravinath; Han, Songi
2008-09-16
We present a unique analysis tool for the selective detection of local water inside soft molecular assemblies (hydrophobic cores, vesicular bilayers, and micellar structures) suspended in bulk water. Through the use of dynamic nuclear polarization (DNP), the (1)H NMR signal of water is amplified, as it interacts with stable radicals that possess approximately 658 times higher spin polarization. We utilized stable nitroxide radicals covalently attached along the hydrophobic tail of stearic acid molecules that incorporate themselves into surfactant-based micelle or vesicle structures. Here, we present a study of local water content and fluid viscosity inside oleate micelles and vesicles and Triton X-100 micelles to serve as model systems for soft molecular assemblies. This approach is unique because the amplification of the NMR signal is performed in bulk solution and under ambient conditions with site-specific spin labels that only detect the water that is directly interacting with the localized spin labels. Continuous wave (cw) electron spin resonance (ESR) analysis provides rotational dynamics of the spin-labeled molecular chain segments and local polarity parameters that can be related to hydration properties, whereas we show that DNP-enhanced (1)H NMR analysis of fluid samples directly provides translational water dynamics and permeability of the local environment probed by the spin label. Our technique therefore has the potential to become a powerful analysis tool, complementary to cw ESR, to study hydration characteristics of surfactant assemblies, lipid bilayers, or protein aggregates, where water dynamics is a key parameter of their structure and function. In this study, we find that there is significant penetration of water inside the oleate micelles with a higher average local water viscosity (approximately 1.8 cP) than in bulk water, and Triton X-100 micelles and oleate vesicle bilayers mostly exclude water while allowing for considerable surfactant chain
Distribution of Pico- and Nanosecond Motions in Disordered Proteins from Nuclear Spin Relaxation
Khan, Shahid N.; Charlier, Cyril; Augustyniak, Rafal; Salvi, Nicola; Déjean, Victoire; Bodenhausen, Geoffrey; Lequin, Olivier; Pelupessy, Philippe; Ferrage, Fabien
2015-01-01
Intrinsically disordered proteins and intrinsically disordered regions (IDRs) are ubiquitous in the eukaryotic proteome. The description and understanding of their conformational properties require the development of new experimental, computational, and theoretical approaches. Here, we use nuclear spin relaxation to investigate the distribution of timescales of motions in an IDR from picoseconds to nanoseconds. Nitrogen-15 relaxation rates have been measured at five magnetic fields, ranging from 9.4 to 23.5 T (400–1000 MHz for protons). This exceptional wealth of data allowed us to map the spectral density function for the motions of backbone NH pairs in the partially disordered transcription factor Engrailed at 11 different frequencies. We introduce an approach called interpretation of motions by a projection onto an array of correlation times (IMPACT), which focuses on an array of six correlation times with intervals that are equidistant on a logarithmic scale between 21 ps and 21 ns. The distribution of motions in Engrailed varies smoothly along the protein sequence and is multimodal for most residues, with a prevalence of motions around 1 ns in the IDR. We show that IMPACT often provides better quantitative agreement with experimental data than conventional model-free or extended model-free analyses with two or three correlation times. We introduce a graphical representation that offers a convenient platform for a qualitative discussion of dynamics. Even when relaxation data are only acquired at three magnetic fields that are readily accessible, the IMPACT analysis gives a satisfactory characterization of spectral density functions, thus opening the way to a broad use of this approach. PMID:26331256
Magnetization studies of the nuclear spin ordered phases of solid 3He in silver sinters
NASA Astrophysics Data System (ADS)
Schuberth, E. A.; Kath, M.; Tassini, L.; Millan-Chacartegui, C.
2005-08-01
Solid 3He, in the bcc lattice between 34 and 100 bar, exhibits two nuclear magnetic ordered phases in the sub-mK temperature range, the so called U2D2 low (magnetic) field phase and the “high field phase” above 0.4 T. To determine the exact spin structure of these phases we started a project of neutron scattering from the ordered solid in collaboration with the Hahn-Meitner Institute, Berlin, and other European and US groups. For this experiment it is crucial to grow a single crystal within the sinter needed for cooling the solid to temperatures of the order of 500 μK (or even twenty times lower in the case of the hcp lattice which is formed above 100 bar) and to keep it there long enough to measure a magnetic neutron reflection. We studied the growth of crystals in Ag sinters of different pore size and with different growth speeds to find an optimal way to obtain single crystalline samples. As a first diagnostic step we performed pulsed NMR measurements in the ordered phases of solid 3He in a sinter of 2700 Å particle size down to temperatures of 450 μK at various molar volumes. We could keep the samples in the ordered state for as long as 140 h. The second method we used was SQUID magnetometry. For the low field phase TN was indicated by a drop of the intensity, both in the NMR signal and in the dc magnetization, whereas in the high field phase an increase of about 30% was observed below the ordering temperature. For the fabrication of the sinters a packing fraction of 50% and subsequent annealing proved to be very favorable to obtain cold ordered solid. Furthermore, we find that a paramagnetic surface contribution from a few monolayers of 3He exists down to 500 μK in addition to the bulk magnetization.
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
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. PMID:21774549
Nuclear shape transitions and some properties of aligned-particle configurations at high spin
Koo, T.L.; Chowdhury, P.; Emling, H.
1982-01-01
Two topics are addressed in this paper. First, we discuss the variation of shapes with spin and neutron number for nuclei in the N approx. = 88 transitional region. Second, we present comments on the feeding times of very high spin single-particle yrast states.
Nuclear magnetic relaxation by the dipolar EMOR mechanism: Three-spin systems.
Chang, Zhiwei; Halle, Bertil
2016-07-21
In aqueous systems with immobilized macromolecules, including biological tissue, the longitudinal spin relaxation of water protons is primarily induced by exchange-mediated orientational randomization (EMOR) of intra- and intermolecular magnetic dipole-dipole couplings. Starting from the stochastic Liouville equation, we have developed a non-perturbative theory that can describe relaxation by the dipolar EMOR mechanism over the full range of exchange rates, dipole couplings, and Larmor frequencies. Here, we implement the general dipolar EMOR theory for a macromolecule-bound three-spin system, where one, two, or all three spins exchange with the bulk solution phase. In contrast to the previously studied two-spin system with a single dipole coupling, there are now three dipole couplings, so relaxation is affected by distinct correlations as well as by self-correlations. Moreover, relaxation can now couple the magnetizations with three-spin modes and, in the presence of a static dipole coupling, with two-spin modes. As a result of this complexity, three secondary dispersion steps with different physical origins can appear in the longitudinal relaxation dispersion profile, in addition to the primary dispersion step at the Larmor frequency matching the exchange rate. Furthermore, and in contrast to the two-spin system, longitudinal relaxation can be significantly affected by chemical shifts and by the odd-valued ("imaginary") part of the spectral density function. We anticipate that the detailed studies of two-spin and three-spin systems that have now been completed will provide the foundation for developing an approximate multi-spin dipolar EMOR theory sufficiently accurate and computationally efficient to allow quantitative molecular-level interpretation of frequency-dependent water-proton longitudinal relaxation data from biophysical model systems and soft biological tissue. PMID:27448879
Nuclear magnetic relaxation by the dipolar EMOR mechanism: Three-spin systems
NASA Astrophysics Data System (ADS)
Chang, Zhiwei; Halle, Bertil
2016-07-01
In aqueous systems with immobilized macromolecules, including biological tissue, the longitudinal spin relaxation of water protons is primarily induced by exchange-mediated orientational randomization (EMOR) of intra- and intermolecular magnetic dipole-dipole couplings. Starting from the stochastic Liouville equation, we have developed a non-perturbative theory that can describe relaxation by the dipolar EMOR mechanism over the full range of exchange rates, dipole couplings, and Larmor frequencies. Here, we implement the general dipolar EMOR theory for a macromolecule-bound three-spin system, where one, two, or all three spins exchange with the bulk solution phase. In contrast to the previously studied two-spin system with a single dipole coupling, there are now three dipole couplings, so relaxation is affected by distinct correlations as well as by self-correlations. Moreover, relaxation can now couple the magnetizations with three-spin modes and, in the presence of a static dipole coupling, with two-spin modes. As a result of this complexity, three secondary dispersion steps with different physical origins can appear in the longitudinal relaxation dispersion profile, in addition to the primary dispersion step at the Larmor frequency matching the exchange rate. Furthermore, and in contrast to the two-spin system, longitudinal relaxation can be significantly affected by chemical shifts and by the odd-valued ("imaginary") part of the spectral density function. We anticipate that the detailed studies of two-spin and three-spin systems that have now been completed will provide the foundation for developing an approximate multi-spin dipolar EMOR theory sufficiently accurate and computationally efficient to allow quantitative molecular-level interpretation of frequency-dependent water-proton longitudinal relaxation data from biophysical model systems and soft biological tissue.
Theory of long-lived nuclear spin states in methyl groups and quantum-rotor induced polarisation
NASA Astrophysics Data System (ADS)
Dumez, Jean-Nicolas; Hâkansson, Pär; Mamone, Salvatore; Meier, Benno; Stevanato, Gabriele; Hill-Cousins, Joseph T.; Roy, Soumya Singha; Brown, Richard C. D.; Pileio, Giuseppe; Levitt, Malcolm H.
2015-01-01
Long-lived nuclear spin states have a relaxation time much longer than the longitudinal relaxation time T1. Long-lived states extend significantly the time scales that may be probed with magnetic resonance, with possible applications to transport and binding studies, and to hyperpolarised imaging. Rapidly rotating methyl groups in solution may support a long-lived state, consisting of a population imbalance between states of different spin exchange symmetries. Here, we expand the formalism for describing the behaviour of long-lived nuclear spin states in methyl groups, with special attention to the hyperpolarisation effects observed in 13CH3 groups upon rapidly converting a material with low-barrier methyl rotation from the cryogenic solid state to a room-temperature solution [M. Icker and S. Berger, J. Magn. Reson. 219, 1 (2012)]. We analyse the relaxation properties of methyl long-lived states using semi-classical relaxation theory. Numerical simulations are supplemented with a spherical-tensor analysis, which captures the essential properties of methyl long-lived states.
Theory of long-lived nuclear spin states in methyl groups and quantum-rotor induced polarisation
Dumez, Jean-Nicolas; Håkansson, Pär; Mamone, Salvatore; Meier, Benno; Stevanato, Gabriele; Hill-Cousins, Joseph T.; Roy, Soumya Singha; Brown, Richard C. D.; Pileio, Giuseppe; Levitt, Malcolm H.
2015-01-28
Long-lived nuclear spin states have a relaxation time much longer than the longitudinal relaxation time T{sub 1}. Long-lived states extend significantly the time scales that may be probed with magnetic resonance, with possible applications to transport and binding studies, and to hyperpolarised imaging. Rapidly rotating methyl groups in solution may support a long-lived state, consisting of a population imbalance between states of different spin exchange symmetries. Here, we expand the formalism for describing the behaviour of long-lived nuclear spin states in methyl groups, with special attention to the hyperpolarisation effects observed in {sup 13}CH{sub 3} groups upon rapidly converting a material with low-barrier methyl rotation from the cryogenic solid state to a room-temperature solution [M. Icker and S. Berger, J. Magn. Reson. 219, 1 (2012)]. We analyse the relaxation properties of methyl long-lived states using semi-classical relaxation theory. Numerical simulations are supplemented with a spherical-tensor analysis, which captures the essential properties of methyl long-lived states.
Balasubramanian, K
2004-03-17
We have presented a group theoretical analysis of the vibrational modes and rovibronic levels of a novel extended aromatic C{sub 48}N{sub 12} azafullerene. The nuclear spin multiplets and statistical weights of {sup 14}N spin-1 bosons, vibrational and rotational analysis and computed vibrational spectra are provided. We have also predicted the properties of the {sup 3}A{sub u}, {sup 3}E{sub g}, and {sup 3}E{sub u} excited states of C{sub 48}N{sub 12} that lie 1.9 eV above the {sup 1}A{sub g} ground state, and that the {sup 3}E{sub g} and {sup 3}E{sub u} states would undergo Jahn-Teller distortion into chiral structures with no symmetry and an achiral structure with C{sub i} symmetry.
SivaRanjan, Uppala; Ramachandran, Ramesh
2014-02-07
A quantum-mechanical model integrating the concepts of reduced density matrix and effective Hamiltonians is proposed to explain the multi-spin effects observed in rotational resonance (R{sup 2}) nuclear magnetic resonance (NMR) experiments. Employing this approach, the spin system of interest is described in a reduced subspace inclusive of its coupling to the surroundings. Through suitable model systems, the utility of our theory is demonstrated and verified with simulations emerging from both analytic and numerical methods. The analytic results presented in this article provide an accurate description/interpretation of R{sup 2} experimental results and could serve as a test-bed for distinguishing coherent/incoherent effects in solid-state NMR.
Theory of nuclear spin-lattice relaxation in La2CuO4 at high temperatures
NASA Astrophysics Data System (ADS)
Sokol, A.; Gagliano, E.; Bacci, S.
1993-06-01
The nuclear-spin-lattice relaxation in La2CuO4 is reexamined in connection with the recent measurements of the NQR relaxation rate for temperatures up to 900 K [T. Imai, C. P. Slichter, K. Yoshimura, and K. Kosuge, Phys. Rev. Lett. 70, 1002 (1993)]. We use an approach based on the exact diagonalization for the Heisenberg model to calculate the short-wavelength contribution to the relaxation rate in the high-temperature region, T>~J/2. It is shown that the spin diffusion accounts for approximately 10% of the total relaxation rate at 900 K and would beome dominant for T>J. The calculated 1/T1 is in good agreement with the experiment both in terms of the absolute value and temperature dependence.
Rosay, Melanie; Weis, Volker; Kreischer, Kenneth E; Temkin, Richard J; Griffin, Robert G
2002-04-01
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
NASA Astrophysics Data System (ADS)
Tycko, R.; Dabbagh, G.; Vaughan, G. B. M.; Heiney, P. A.; Strongin, R. M.; Cichy, M. A.; Smith, A. B., III
1993-11-01
We present the results of 13C nuclear magnetic resonance (NMR) measurements that probe molecular orientational dynamics in solid C70 in the temperature range 223-343 K. Orientational dynamics affect the NMR line shapes and spin-lattice relaxation rates by modulating the 13C chemical shift anisotropy (CSA). Motionally averaged CSA line shapes, determined from both one-dimensional and two-dimensional magic angle spinning NMR spectra, and relaxation rates are determined for each of the five inequivalent carbon sites in the C70 molecule. Comparisons of the results for the five sites provide evidence for rapid uniaxial molecular reorientation in the monoclinic (T≤280 K) and rhombohedral (280≤T≤330 K) phases and rapid isotropic reorientation in the face-centered cubic (T≥330 K) phase. The orientational correlation time is roughly 2 ns at 250 K and of the order of 5 ps at 340 K.
Moka, D; Vorreuther, R; Schicha, H; Spraul, M; Humpfer, E; Lipinski, M; Foxall, P J; Nicholson, J K; Lindon, J C
1998-05-01
High resolution 1H nuclear magnetic resonance (NMR) spectra using spinning at the magic angle (1H MAS NMR) have been obtained on intact normal and pathological kidney tissue samples from patients undergoing surgery for renal cell carcinoma (RCC). The spectra were measured on ca. 80 mg samples and provided high resolution 1H NMR spectra in which effects of dipolar couplings, chemical shift anisotropy and magnetic susceptibility differences are minimised thus yielding high spectral resolution. Conventional one-dimensional and spin-echo spectra and two-dimensional J-resolved, TOCSY and 1H-13C HMQC spectra were also measured on selected samples and these allowed the assignment of resonances of endogenous substances comprising both cytosolic and membrane components. The tumour tissues were characterised principally by an increased lipid content. These are the first reported results on human tumour tissues using this technique and the approach offers potential for the rapid classification of different types of tumour tissue. PMID:9608434
Multiple quantum filtering and spin exchange in solid state nuclear magnetic resonance
NASA Astrophysics Data System (ADS)
Ba, Yong; Ripmeester, John A.
1998-05-01
Multiple quantum NMR of coupled spin-1/2 nuclei in a solid has been exploited as a filter to separate different magnetization components in a spatially heterogeneous system. After filtering, the spins labeled according to coherence orders were used to follow the track of spin exchange between different domains. In order to avoid time-consuming two-dimensional experiments, this exchange was detected in a one-dimensional experiment via selective detection of multiple quantum coherences. The technique was demonstrated for samples of solid adamantane in contact with its saturated solution in benzene-d6 and for a high-density polyoxymethylene.
NASA Astrophysics Data System (ADS)
Abernathy, S. M.; Miller, J. C.; Lohr, L. L.; Sharp, R. R.
1998-09-01
Dissolved paramagnetic ions generally provide an efficient mechanism for the relaxation of nuclear spins in solution, a phenomenon called the nuclear magnetic resonance-paramagnetic relaxation enhancement (NMR-PRE). Metal ions with electron spins S⩾1 exhibit rich NMR relaxation phenomena originating in the properties of the zero-field splitting (zfs) interaction, which vanishes for spin-1/2 ions but which is nonzero for S⩾1 ions in site symmetry lower than cubic. For S⩾1 ions in the vicinity of the zfs-limit, i.e., at magnetic-field strengths low enough that the zfs energy exceeds the Zeeman energy, the NMR-PRE depends strongly on the detailed structure of the electron spin energy levels as well as on the spatial quantization of the spin motion. It is shown theoretically and experimentally that the NMR-PRE produced by integer spins can be influenced strongly by the small intradoublet zero-field splittings, i.e., the splittings between the components of the non-Kramers doublets, which are produced by noncylindrical components of the crystal field potential. These small splittings produce relatively low-frequency oscillations in the dipolar field associated with (the spin component along the molecule-fixed ẑ axis). These motions decouple the nuclear spin from the electron spin, thereby depressing, in some cases very strongly, the NMR-PRE. The presence of a relatively small Zeeman field, comparable in magnitude to the intradoublet spacing but small compared to the larger interdoublet zfs splittings, causes a major change in the spin wave functions which has profound effects on the motions of the electron spin. When the Zeeman energy exceeds the small zfs splitting, the oscillatory motion of damps out, with the result that the electron spin couples more effectively to the nuclear spin, providing a more efficient NMR relaxation pathway. NMR-PRE data are presented for the S=1 complex Ni(II)(o-pda)2Cl2 (o-pda=ortho-phenylenediamine) which confirm the
Effects of orbital and spin current interference in E1 and M2 nuclear excitations
Goncharova, N. G.
2015-12-15
The interference of contributions from the orbital and spin currents to the E1 and M2 resonances is investigated. The results of the current interference analysis within the shell model are compared with the experimental data.
NASA Astrophysics Data System (ADS)
Ito, T. U.; Higemoto, W.; Sakai, A.; Tsujimoto, M.; Nakatsuji, S.
2015-09-01
The nature of multipolar order and hyperfine-enhanced (HE) 141Pr nuclear spin dynamics in PrV2Al20 was investigated using the muon spin relaxation technique. No explicit sign of time-reversal symmetry breaking was found below the multipolar order temperature TQ˜0.6 K in a zero applied field as anticipated on the basis of the antiferroquadrupolar (AFQ) order picture proposed by Sakai and Nakatsuji [J. Phys. Soc. Jpn. 80, 063701 (2011), 10.1143/JPSJ.80.063701]. Further evidence of the nonmagnetic ground state was obtained from the observation of HE 141Pr nuclear spin fluctuations in the MHz scale. A marked increase in the muon spin-lattice relaxation rate (1 /T1 ,μ) was observed below 1 K with decreasing temperature, which was attributed to the perturbation on the HE 141Pr nuclear spin dynamics associated with the development of AFQ correlations. The longitudinal field dependence of 1 /T1 ,μ revealed that the enhanced 141Pr nuclear spin accidentally has an effective gyromagnetic ratio close to that of the muon.
Efficient calculation of nuclear spin-rotation constants from auxiliary density functional theory.
Zuniga-Gutierrez, Bernardo; Camacho-Gonzalez, Monica; Bendana-Castillo, Alfonso; Simon-Bastida, Patricia; Calaminici, Patrizia; Köster, Andreas M
2015-09-14
The computation of the spin-rotation tensor within the framework of auxiliary density functional theory (ADFT) in combination with the gauge including atomic orbital (GIAO) scheme, to treat the gauge origin problem, is presented. For the spin-rotation tensor, the calculation of the magnetic shielding tensor represents the most demanding computational task. Employing the ADFT-GIAO methodology, the central processing unit time for the magnetic shielding tensor calculation can be dramatically reduced. In this work, the quality of spin-rotation constants obtained with the ADFT-GIAO methodology is compared with available experimental data as well as with other theoretical results at the Hartree-Fock and coupled-cluster level of theory. It is found that the agreement between the ADFT-GIAO results and the experiment is good and very similar to the ones obtained by the coupled-cluster single-doubles-perturbative triples-GIAO methodology. With the improved computational performance achieved, the computation of the spin-rotation tensors of large systems or along Born-Oppenheimer molecular dynamics trajectories becomes feasible in reasonable times. Three models of carbon fullerenes containing hundreds of atoms and thousands of basis functions are used for benchmarking the performance. Furthermore, a theoretical study of temperature effects on the structure and spin-rotation tensor of the H(12)C-(12)CH-DF complex is presented. Here, the temperature dependency of the spin-rotation tensor of the fluorine nucleus can be used to identify experimentally the so far unknown bent isomer of this complex. To the best of our knowledge this is the first time that temperature effects on the spin-rotation tensor are investigated. PMID:26374014
Efficient calculation of nuclear spin-rotation constants from auxiliary density functional theory
Zuniga-Gutierrez, Bernardo; Camacho-Gonzalez, Monica; Bendana-Castillo, Alfonso; Simon-Bastida, Patricia; Calaminici, Patrizia; Köster, Andreas M.
2015-09-14
The computation of the spin-rotation tensor within the framework of auxiliary density functional theory (ADFT) in combination with the gauge including atomic orbital (GIAO) scheme, to treat the gauge origin problem, is presented. For the spin-rotation tensor, the calculation of the magnetic shielding tensor represents the most demanding computational task. Employing the ADFT-GIAO methodology, the central processing unit time for the magnetic shielding tensor calculation can be dramatically reduced. In this work, the quality of spin-rotation constants obtained with the ADFT-GIAO methodology is compared with available experimental data as well as with other theoretical results at the Hartree-Fock and coupled-cluster level of theory. It is found that the agreement between the ADFT-GIAO results and the experiment is good and very similar to the ones obtained by the coupled-cluster single-doubles-perturbative triples-GIAO methodology. With the improved computational performance achieved, the computation of the spin-rotation tensors of large systems or along Born-Oppenheimer molecular dynamics trajectories becomes feasible in reasonable times. Three models of carbon fullerenes containing hundreds of atoms and thousands of basis functions are used for benchmarking the performance. Furthermore, a theoretical study of temperature effects on the structure and spin-rotation tensor of the H{sup 12}C–{sup 12}CH–DF complex is presented. Here, the temperature dependency of the spin-rotation tensor of the fluorine nucleus can be used to identify experimentally the so far unknown bent isomer of this complex. To the best of our knowledge this is the first time that temperature effects on the spin-rotation tensor are investigated.
NASA Astrophysics Data System (ADS)
Hayashida, H.; Oku, T.; Kira, H.; Sakai, K.; Hiroi, K.; Ino, T.; Shinohara, T.; Imagawa, T.; Ohkawara, M.; Ohoyama, K.; Kakurai, K.; Takeda, M.; Yamazaki, D.; Oikawa, K.; Harada, M.; Miyata, N.; Akutsu, K.; Mizusawa, M.; Parker, J. D.; Matsumoto, Y.; Zhang, S.; Suzuki, J.; Soyama, K.; Aizawa, K.; Arai, M.
2016-04-01
We have been developing a 3He neutron spin filter (NSF) using the spin exchange optical pumping (SEOP) technique. The 3He NSF provides a high-energy polarized neutron beam with large beam size. Moreover the 3He NSF can work as a π-flipper for a polarized neutron beam by flipping the 3He nuclear spin using a nuclear magnetic resonance (NMR) technique. For NMR with the in-situ SEOP technique, the polarization of the laser must be reversed simultaneously because a non-reversed laser reduces the polarization of the spin-flipped 3He. To change the polarity of the laser, a half-wavelength plate was installed. The rotation angle of the half-wavelength plate was optimized, and a polarization of 97% was obtained for the circularly polarized laser. The 3He polarization reached 70% and was stable over one week. A demonstration of the 3He nuclear spin flip system was performed at the polarized neutron reflectometer SHARAKU (BL17) and NOBORU (BL10) at J-PARC. Off-specular measurement from a magnetic Fe/Cr thin film and magnetic imaging of a magnetic steel sheet were performed at BL17 and BL10, respectively.
NASA Astrophysics Data System (ADS)
Chou, Yi; Huang, Shang-Yu; Goan, Hsi-Sheng
2015-05-01
A negatively charged nitrogen-vacancy (NV) center in diamond has been recognized as a good solid-state qubit. A system consisting of the electronic spin of the NV center and hyperfine-coupled nitrogen and additionally nearby carbon nuclear spins can form a quantum register of several qubits for quantum information processing or as a node in a quantum repeater. Several impressive experiments on the hybrid electron and nuclear spin register have been reported, but fidelities achieved so far are not yet at or below the thresholds required for fault-tolerant quantum computation (FTQC). Using quantum optimal control theory based on the Krotov method, we show here that fast and high-fidelity single-qubit and two-qubit gates in the universal quantum gate set for FTQC, taking into account the effects of the leakage state, nearby noise qubits, and distant bath spins, can be achieved with errors less than those required by the threshold theorem of FTQC.
NASA Astrophysics Data System (ADS)
Inoue, Takeshi; Furukawa, Takeshi; Yoshimi, Akihiro; Nanao, Tsubasa; Chikamori, Masatoshi; Suzuki, Kunifumi; Hayashi, Hironori; Miyatake, Hirokazu; Ichikawa, Yuichi; Tsuchiya, Masato; Hatakeyama, Naoto; Kagami, Sota; Uchida, Makoto; Ueno, Hideki; Matsuo, Yukari; Fukuyama, Takeshi; Asahi, Koichiro
2016-06-01
A 129Xe nuclear spin oscillator with an artificial feedback was constructed, and detailed studies were conducted on its performance, focusing on the frequency stability. As a result, the major sources of drift of the precession frequency in the present spin oscillator setup were identified to be drifts of a solenoid current and an environmental magnetic field. By introducing stabilization systems for the current and the environmental field, which yielded improvements by one order of magnitude on the solenoid current and by a factor of three on the environmental field, a frequency precision of 7.9 nHz was obtained for a one-shot measurement of 3 × 104 s duration. We found, however, that the Allan deviation leveled off at around 30 μHz, indicating a strong need for the precision monitor of the experimental conditions represented by magnetometry. The frequency stability of the spin oscillator is discussed in relation to an experimental search for an electric dipole moment of the 129Xe atom.
NASA Astrophysics Data System (ADS)
Xiao, Yunlong; Liu, Wenjian
2013-07-01
The relativistic molecular Hamiltonian written in the body-fixed frame of reference is the basis for high-precision calculations of spectroscopic parameters involving nuclear vibrations and/or rotations. Such a Hamiltonian that describes electrons fully relativistically and nuclei quasi-relativistically is just developed for semi-rigid nonlinear molecules [Y. Xiao and W. Liu, J. Chem. Phys. 138, 134104 (2013)], 10.1063/1.4797496. Yet, the formulation should somewhat be revised for linear molecules thanks to some unusual features arising from the redundancy of the rotation around the molecular axis. Nonetheless, the resulting isomorphic Hamiltonian is rather similar to that for nonlinear molecules. Consequently, the relativistic formulation of nuclear spin-rotation (NSR) tensor for linear molecules is very much the same as that for nonlinear molecules. So is the relativistic mapping between experimental NSR and NMR.
Analysis of experimental data on nuclear masses within Wigner spin-isospin SU(4) symmetry
Nurmukhamedov, A. M.
2009-03-15
The problem of the realization of Wigner spin-isospin SU(4) symmetry in nuclei is analyzed on the basis of available experimental data on nuclide masses in the mass-number range 1 {<=} A {<=} 257. Empirical expressions are obtained for the universal functions in the Wigner mass formula. The experimental values of the energy of spin-orbit interaction are determined for the aforementioned nuclides. An alternative mechanism of the origin of the odd-even effect in nuclei having an even mass number associated with a specific property of the Casimir operator is proposed. The results obtained in this study suggest that SU(4) symmetry is broken predominantly by spin-orbit interaction.
What Do Nuclear Spin Temperatures Tell Us About The Origin Of Comets? A Multi-molecule Study
NASA Astrophysics Data System (ADS)
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
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 ν7 band of C2H6 and ν3 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
NASA Astrophysics Data System (ADS)
Thurber, Kent; Tycko, Robert
2016-03-01
We describe novel instrumentation for low-temperature solid state nuclear magnetic resonance (NMR) with dynamic nuclear polarization (DNP) and magic-angle spinning (MAS), focusing on aspects of this instrumentation that have not been described in detail in previous publications. We characterize the performance of an extended interaction oscillator (EIO) microwave source, operating near 264 GHz with 1.5 W output power, which we use in conjunction with a quasi-optical microwave polarizing system and a MAS NMR probe that employs liquid helium for sample cooling and nitrogen gas for sample spinning. Enhancement factors for cross-polarized 13C NMR signals in the 100-200 range are demonstrated with DNP at 25 K. The dependences of signal amplitudes on sample temperature, as well as microwave power, polarization, and frequency, are presented. We show that sample temperatures below 30 K can be achieved with helium consumption rates below 1.3 l/h. To illustrate potential applications of this instrumentation in structural studies of biochemical systems, we compare results from low-temperature DNP experiments on a calmodulin-binding peptide in its free and bound states.
Thurber, Kent; Tycko, Robert
2016-03-01
We describe novel instrumentation for low-temperature solid state nuclear magnetic resonance (NMR) with dynamic nuclear polarization (DNP) and magic-angle spinning (MAS), focusing on aspects of this instrumentation that have not been described in detail in previous publications. We characterize the performance of an extended interaction oscillator (EIO) microwave source, operating near 264 GHz with 1.5 W output power, which we use in conjunction with a quasi-optical microwave polarizing system and a MAS NMR probe that employs liquid helium for sample cooling and nitrogen gas for sample spinning. Enhancement factors for cross-polarized (13)C NMR signals in the 100-200 range are demonstrated with DNP at 25K. The dependences of signal amplitudes on sample temperature, as well as microwave power, polarization, and frequency, are presented. We show that sample temperatures below 30K can be achieved with helium consumption rates below 1.3 l/h. To illustrate potential applications of this instrumentation in structural studies of biochemical systems, we compare results from low-temperature DNP experiments on a calmodulin-binding peptide in its free and bound states. PMID:26920835
Spin noise in mixed Spin Systems
NASA Astrophysics Data System (ADS)
Bauch, Erik; Junghyun, Paul; Singh, Swati; Devakul, Trithep; Feguin, Adrian; Hart, Connor; Walsworth, Ronald
2016-05-01
The spin noise due to interaction of multiple spin species in mixed spin systems provides a fundamental limit to ultra-sensitive ensemble sensing and quantum information applications. In our work, we investigate the interaction of dense nuclear 13C spins with electronic nitrogen spins using Nitrogen-Vacancy centers in diamond. Our work shows experimentally and theoretically, that under certain conditions, spin noise is greatly suppressed and the coherence time of NV centers improved by order of magnitudes, providing a pathway to engineering high density ensemble samples with long coherence times at room temperature.
Anisotropic collective motion contributes to nuclear spin relaxation in crystalline proteins.
Lewandowski, Józef R; Sein, Julien; Blackledge, Martin; Emsley, Lyndon
2010-02-01
A model for calculating the influence of anisotropic collective motions on NMR relaxation rates in crystalline proteins is presented. We show that small-amplitude (<10 degrees ) fluctuations may lead to substantial contributions to the (15)N spin-lattice relaxation rates and propose that the effect of domain motions should be included in solid-state NMR analyses of protein dynamics. PMID:19916496
Devices and process for high-pressure magic angle spinning nuclear magnetic resonance
Hoyt, David W; Sears, Jr., Jesse A; Turcu, Romulus V.F.; Rosso, Kevin M; Hu, Jian Zhi
2014-04-08
A high-pressure magic angle spinning (MAS) rotor is detailed that includes a high-pressure sample cell that maintains high pressures exceeding 150 bar. The sample cell design minimizes pressure losses due to penetration over an extended period of time.
Dynamic nuclear polarization at 40 kHz magic angle spinning.
Chaudhari, Sachin R; Berruyer, Pierrick; Gajan, David; Reiter, Christian; Engelke, Frank; Silverio, Daniel L; Copéret, Christophe; Lelli, Moreno; Lesage, Anne; Emsley, Lyndon
2016-04-21
DNP-enhanced solid-state NMR spectroscopy under magic angle spinning (MAS) is rapidly developing into a powerful analytical tool to investigate the structure of a wide range of solid materials, because it provides unsurpassed sensitivity gains. Most developments and applications of DNP MAS NMR were so far reported at moderate spinning frequencies (up to 14 kHz using 3.2 mm rotors). Here, using a 1.3 mm MAS DNP probe operating at 18.8 T and ∼100 K, we show that signal amplification factors can be increased by up to a factor two when using smaller volume rotors as compared to 3.2 mm rotors, and report enhancements of around 60 over a range of sample spinning rates from 10 to 40 kHz. Spinning at 40 kHz is also shown to increase (29)Si coherence lifetimes by a factor three as compared to 10 kHz, substantially increasing sensitivity in CPMG type experiments. The contribution of quenching effects to the overall sensitivity gain at very fast MAS is evaluated, and applications are reported on a functionalised mesostructured organic-inorganic material. PMID:27035630
NASA Technical Reports Server (NTRS)
1974-01-01
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.
Adiabatic transfer of coherences in a cluster of coupled nuclear spins
Lee, Jae-Seung; Cardwell, Kate E.; Khitrin, A. K.
2005-12-15
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.
NASA Astrophysics Data System (ADS)
Trautwein, A. X.; Paulsen, H.; Winkler, H.; Giefers, H.; Wortmann, G.; Toftlund, H.; Wolny, J. A.; Chumakov, A. I.; Leupold, O.
2010-03-01
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.
NASA Astrophysics Data System (ADS)
Inoue, T.; Tsuchiya, M.; Furukawa, T.; Hayashi, H.; Nanao, T.; Yoshimi, A.; Uchida, M.; Matsuo, Y.; Asahi, K.
2011-01-01
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.
NASA Astrophysics Data System (ADS)
Vincent, Sebastien J. F.; Zwahlen, Catherine; Post, Carol Beth; Burgner, John W.; Bodenhausen, Geoffrey
1997-04-01
We have reinvestigated the conformation of NAD+ bound to dogfish lactate dehydrogenase (LDH) by using an NMR experiment that allows one to exploit nuclear Overhauser effects to determine internuclear distances between pairs of protons, without perturbation of spin-diffusion effects from other protons belonging either to the cofactor or to the binding pocket of the enzyme. The analysis indicates that the structure of bound NAD+ is in accord with the conformation determined in the solid state by x-ray diffraction for the adenosine moiety, but deviates significantly from that of the nicotinamide. The NMR data indicate conformational averaging about the glycosidic bond of the nicotinamide nucleotide. In view of the strict stereospecificity of catalysis by LDH and the conformational averaging of bound NAD+ that we infer from solution-state NMR, we suggest that LDH binds the cofactor in both syn and anti conformations, but that binding interactions in the syn conformation are not catalytically productive.
NASA Astrophysics Data System (ADS)
Crooker, S. A.; Liu, F.; Kelley, M. R.; Martinez, N. J. D.; Nie, W.; Mohite, A.; Nayyar, I. H.; Tretiak, S.; Smith, D. L.; Ruden, P. P.
2014-10-01
We use spectrally resolved magneto-electroluminescence (EL) measurements to study the energy dependence of hyperfine interactions between polaron and nuclear spins in organic light-emitting diodes. Using layered devices that generate bright exciplex emission, we show that the increase in EL emission intensity I due to small applied magnetic fields of order 100 mT is markedly larger at the high-energy blue end of the EL spectrum (ΔI/I ˜ 11%) than at the low-energy red end (˜4%). Concurrently, the widths of the magneto-EL curves increase monotonically from blue to red, revealing an increasing hyperfine coupling between polarons and nuclei and directly providing insight into the energy-dependent spatial extent and localization of polarons.
Crooker, S. A.; Kelley, M. R.; Martinez, N. J. D.; Nie, W.; Mohite, A.; Nayyar, I. H.; Tretiak, S.; Smith, D. L.; Liu, F.; Ruden, P. P.
2014-10-13
We use spectrally resolved magneto-electroluminescence (EL) measurements to study the energy dependence of hyperfine interactions between polaron and nuclear spins in organic light-emitting diodes. Using layered devices that generate bright exciplex emission, we show that the increase in EL emission intensity I due to small applied magnetic fields of order 100 mT is markedly larger at the high-energy blue end of the EL spectrum (ΔI/I ∼ 11%) than at the low-energy red end (∼4%). Concurrently, the widths of the magneto-EL curves increase monotonically from blue to red, revealing an increasing hyperfine coupling between polarons and nuclei and directly providing insight into the energy-dependent spatial extent and localization of polarons.
NASA Astrophysics Data System (ADS)
Mizuno, Takashi; Hioka, Katsuya; Fujioka, Koji; Takegoshi, K.
2008-04-01
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 (˜12K) 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). H1 MAS NMR with the coil temperature of ˜20K was successfully observed for solid adamantane rotating at room temperature, and signal-to-noise increment due to this cryocoil approach was confirmed.
NASA Astrophysics Data System (ADS)
Fujita, T.; Furukawa, T.; Imamura, K.; Yang, X. F.; Hatakeyama, A.; Kobayashi, T.; Ueno, H.; Asahi, K.; Shimoda, T.; Matsuo, Y.
2015-11-01
A new laser spectroscopic method named "OROCHI (Optical RI-atom Observation in Condensed Helium as Ion catcher)" has been developed for deriving the nuclear spins and electromagnetic moments of low-yield exotic nuclei. In this method, we observe atomic Zeeman and hyperfine structures using laser-radio-frequency/microwave double-resonance spectroscopy. In our previous works, double-resonance spectroscopy was performed successfully with laser-sputtered stable atoms including non-alkali Au atoms as well as alkali Rb and Cs atoms. Following these works, measurements with 84-87Rb energetic ion beams were carried out in the RIKEN projectile fragment separator (RIPS). In this paper, we report the present status of OROCHI and discuss its feasibility, especially for low-yield nuclei such as unstable Au isotopes.
NASA Astrophysics Data System (ADS)
Chang, Zhiwei; Halle, Bertil
2013-10-01
In complex biological or colloidal samples, magnetic relaxation dispersion (MRD) experiments using the field-cycling technique can characterize molecular motions on time scales ranging from nanoseconds to microseconds, provided that a rigorous theory of nuclear spin relaxation is available. In gels, cross-linked proteins, and biological tissues, where an immobilized macromolecular component coexists with a mobile solvent phase, nuclear spins residing in solvent (or cosolvent) species relax predominantly via exchange-mediated orientational randomization (EMOR) of anisotropic nuclear (electric quadrupole or magnetic dipole) couplings. The physical or chemical exchange processes that dominate the MRD typically occur on a time scale of microseconds or longer, where the conventional perturbation theory of spin relaxation breaks down. There is thus a need for a more general relaxation theory. Such a theory, based on the stochastic Liouville equation (SLE) for the EMOR mechanism, is available for a single quadrupolar spin I = 1. Here, we present the corresponding theory for a dipole-coupled spin-1/2 pair. To our knowledge, this is the first treatment of dipolar MRD outside the motional-narrowing regime. Based on an analytical solution of the spatial part of the SLE, we show how the integral longitudinal relaxation rate can be computed efficiently. Both like and unlike spins, with selective or non-selective excitation, are treated. For the experimentally important dilute regime, where only a small fraction of the spin pairs are immobilized, we obtain simple analytical expressions for the auto-relaxation and cross-relaxation rates which generalize the well-known Solomon equations. These generalized results will be useful in biophysical studies, e.g., of intermittent protein dynamics. In addition, they represent a first step towards a rigorous theory of water 1H relaxation in biological tissues, which is a prerequisite for unravelling the molecular basis of soft
Tsunoda, N.; Shimizu, N.; Otsuka, T.; Suzuki, T.
2011-05-06
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.
Hu, Jian Zhi; Sears, Jr., Jesse A.; Hoyt, David W.; Mehta, Hardeep S.; Peden, Charles H. F.
2015-11-24
A continuous-flow (CF) magic angle sample spinning (CF-MAS) NMR rotor and probe are described for investigating reaction dynamics, stable intermediates/transition states, and mechanisms of catalytic reactions in situ. The rotor includes a sample chamber of a flow-through design with a large sample volume that delivers a flow of reactants through a catalyst bed contained within the sample cell allowing in-situ investigations of reactants and products. Flow through the sample chamber improves diffusion of reactants and products through the catalyst. The large volume of the sample chamber enhances sensitivity permitting in situ .sup.13C CF-MAS studies at natural abundance.
Kazanskii, S. A.; Warren, W. W.; Ryskin, A. I.
2009-08-15
Temperature dependences of spin-lattice relaxation rates of the {sup 113}Cd and {sup 19}F lattice nuclei in the CdF{sub 2} semiconductor crystals containing bistable In and Ga impurity centers show that the relaxation mechanisms in the CdF{sub 2}:In and CdF{sub 2}:Ga crystals are different. The basic mechanism of spin-lattice relaxation of the {sup 113}Cd nuclei in the CdF{sub 2}:In crystal is the scalar contact's interaction of nuclear spins with spins of mobile charge carriers of the conduction band. In the CdF{sub 2}:Ga crystal, relaxation of the {sup 113}Cd nuclei is controlled by the contact interaction with electrons moving within a narrow band of impurity states. The same mechanism is apparently responsible for relaxation of the {sup 19}F nuclei in this crystal. In the CdF{sub 2}:In crystal, the {sup 19}F nuclei relax by the dipole-dipole interaction with electron spins localized at the hydrogen-like orbits of shallow donors.
Taddeucci, T.N.
1995-02-01
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.
NASA Astrophysics Data System (ADS)
Morton, Donald C.; Schulhoff, Eva E.; Drake, G. W. F.
2015-12-01
We have calculated the electric dipole (E1) and magnetic quadrupole (M2) oscillator strengths and spontaneous decay rates for 24 spin-changing transitions of atomic helium. We included the effects of the finite nuclear mass and the anomalous magnetic moment of the electron augmented by the recently derived Pachucki term. The specific transitions for 4He are n{ }1{{{S}}}0-{n}\\prime { }3{{{P}}}{1,2} and n{ }3{{{S}}}1-{n}\\prime { }1{{{P}}}1 with n,{n}\\prime ≤slant 3 and n≤slant 10 for {n}\\prime =n. For the E1 calculations we used the Breit approximation and pseudostate expansions to perform the perturbation sums over intermediate states in both the length and velocity gauge as a check on both numerical accuracy and validity of the transition operators. The corrections for the nuclear mass and the electron anomaly tend to cancel, indicating that if one is included, then so should be the other. The tables give mass- and anomaly-dependent coefficients permitting the easy generation of results for the other isotopes of helium.
NASA Astrophysics Data System (ADS)
De Paëpe, Gaël; Eléna, Bénédicte; Emsley, Lyndon
2004-08-01
The work presented here aims at understanding the performance of phase modulated heteronuclear decoupling sequences such as Cosine Modulation or Two Pulse Phase Modulation. To that end we provide an analytical description of the intrinsic behavior of Cosine Modulation decoupling with respect to radio-frequency-inhomogeneity and the proton-proton dipolar coupling network. We discover through a Modulation Frame average Hamiltonian analysis that best decoupling is obtained under conditions where the heteronuclear interactions are removed but notably where homonuclear couplings are recoupled at a homonuclear Rotary Resonance (HORROR) condition in the Modulation Frame. These conclusions are supported by extensive experimental investigations, and notably through the introduction of proton nutation experiments to characterize spin dynamics in solids under decoupling conditions. The theoretical framework presented in this paper allows the prediction of the optimum parameters for a given set of experimental conditions.
Full Controllability of a Singlet-Triplet Qubit Coupled to a Nuclear Spin Qubit
NASA Astrophysics Data System (ADS)
Baczewski, Andrew D.; Gamble, John King; Jacobson, N. Tobias; Muller, Richard P.; Nielsen, Erik; Carr, Stephen M.; Carroll, Malcolm S.; Curry, Matthew; Harvey-Collard, Patrick; Jock, Ryan M.; Rudolph, Martin
Recent experimental developments indicate that it is possible to drive coherent singlet-triplet rotations in a MOS quantum dot coupled to a single nearby phosphorus donor through the electron-nucleus hyperfine interaction. With the addition of NMR, we propose that it is possible to achieve universal 2-qubit control spanning i.) an electronic singlet-triplet subspace of the dot, ii.) the spin-1/2 donor nucleus, and iii.) entangling operations between them. We will assess the practicality of such an approach given realistic experimental conditions and constraints, including a comparison of pulsed and RF control of the detuning between the donor and dot. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Security Administration under Contract DE-AC04-94AL85000.
Effect of nuclear spin on chemical reactions and internal molecular rotation
Sterna, L.L.
1980-12-01
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.
NASA Astrophysics Data System (ADS)
Turcu, R. V.; Hoyt, D. H.; Sears, J. A.; Rosso, K. M.; Felmy, A. R.; Hu, J. Z.
2011-12-01
Understanding the mechanisms and kinetics of mineral carbonation reactions relevant to sequestering carbon dioxide as a supercritical fluid (scCO2) in geologic formations is crucial for accurately predicting long-term storage risks. In situ probes that provide molecular-level information at geologically relevant temperatures and pressures are highly desirable and challenging to develop. Magic angle spinning nuclear magnetic resonance (MAS NMR) is a powerful tool for obtaining detailed molecular structure and dynamics information of a system regardless whether the system is in a solid, a liquid, a gaseous, a supercritical state, or a mixture thereof. However, MAS NMR under scCO2 conditions has never been realized due to the tremendous technical difficulties of achieving and maintaining high pressure within a fast spinning MAS sample rotor. In this work, we report development of a unique high pressure MAS NMR capability capable of handling fluid pressure exceeding 170 bars and temperatures up to 80°C, and its application to mineral carbonation in scCO2 under geologically relevant temperatures and pressures. Mineral carbonation reactions of the magnesium silicate mineral forsterite and the magnesium hydroxide brucite reacted with scCO2 (up to 170 bar) and containing variable content of H2O (at, below, and above saturation in scCO2) were investigated at 50 to 70°C. In situ 13C MAS NMR spectra show peaks corresponding to the reactants, intermediates, and the magnesium carbonation products in a single spectrum. For example, Figure 1 shows the reaction dynamics, i.e., the formation and conversion of reaction intermediates, i.e., HCO3- and nesquehonite, to magnesite as a function of time at 70°C. This capability offers a significant advantage over traditional ex situ 13C MAS experiments on similar systems, where, for example, CO2 and HCO3- are not directly observable.
Moreno, Karlos X; Nasr, Khaled; Milne, Mark; Sherry, A Dean; Goux, Warren J
2015-08-01
Here we report the polarization of the solvent OH protons by SABRE using standard iridium-based catalysts under slightly acidic conditions. Solvent polarization was observed in the presence of a variety of structurally similar N-donor substrates while no solvent enhancement was observed in the absence of substrate or para-hydrogen (p-H2). Solvent polarization was sensitive to the polarizing field and catalyst:substrate ratio in a manner similar to that of substrate protons. SABRE experiments with pyridine-d5 suggest a mechanism where hyperpolarization is transferred from the free substrate to the solvent by chemical exchange while measured hyperpolarization decay times suggest a complimentary mechanism which occurs by direct coordination of the solvent to the catalytic complex. We found the solvent hyperpolarization to decay nearly 3 times more slowly than its characteristic spin-lattice relaxation time suggesting that the hyperpolarized state of the solvent may be sufficiently long lived (∼20s) to hyperpolarize biomolecules having exchangeable protons. This route may offer future opportunities for SABRE to impact metabolic imaging. PMID:26037136
Mechanism of nuclear spin-lattice relaxation and its field dependence for ultraslow atomic motion
Mefed, A. E.
2008-10-15
The contribution of ultraslow self-diffusion of polycrystalline benzene molecules to the spin-lattice relaxation of protons is studied as a function of effective magnetic field H{sub 2} in a doubly rotating frame (DRF). Proton relaxation time T{sub 1{rho}}{sub {rho}} is measured by direct recording of NMR in a rotating frame (RF). The effective fields have a 'magic' orientation corresponding to angles arccos(1/{radical}3) in the RF and {pi}/2 in the DRF so that the secular part of the dipole-dipole interactions of protons is suppressed in two orders of perturbation theory, while the nonsecular part becomes predominant. It is found that the diffusion contribution of benzene molecules to proton relaxation time T{sub 1{rho}}{sub {rho}} is a linear function of the square of field H{sub 2} and exhibits all peculiarities typical of the model of strong collisions generalized to only fluctuating nonsecular dipole interactions in fields exceeding the local field. This means that the model can also be employed in the given conditions. It is shown that perfect agreement with such a dependence can also be obtained in the model of weak collisions if we take into account the concept of the locally effective quantization field, whose magnitude and direction are controlled by the vector sum of field H{sub 2}, and the nonsecular local field perpendicular to it.
David Dennison, the specific heat of hydrogen, and the discovery of nuclear spin
NASA Astrophysics Data System (ADS)
Gearhart, Clayton
2008-04-01
The specific heat of hydrogen gas at low temperatures, first measured by Arnold Eucken in 1912, decreases sharply as the two rotational degrees of freedom freeze out. The ``old quantum theory'' could never explain this behavior satisfactorily, despite persistent efforts. Then in 1926, Heisenberg showed that in the new quantum mechanics, identical particles must have either symmetric or antisymmetric wave functions, and were the key to the spectrum of helium. Friedrich Hund first applied this concept to the rotational specific heat of hydrogen, with limited success. An experimental breakthrough came in 1926, when for the first time, spectral lines involving the ground state of molecular hydrogen were found in the far ultraviolet. Further measurements by the Japanese spectroscopist Takeo Hori led to a moment of inertia for molecular hydrogen more than double earlier estimates. Using this result, the American physicist David Dennison devised the modern theory in 1927, and in the process, found persuasive evidence for proton spin. Most of these actors were at Bohr's institute in Copenhagen in 1926--27; their interaction plays a central role in this story.
NASA Astrophysics Data System (ADS)
Villanueva, G.; Mumma, M.; Bonev, B.; DiSanti, M.; Paganini, L.; Magee-Sauer, K.; Gibb, E.
2014-07-01
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 (T_{spin}), derived from spin-isomeric ratios (R_{spin}, 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 R_{spin} and T_{spin} are normally treated as ''remnant thermometers'' probing the formation environments of cometary molecules. Radiative and collisional transitions between the ortho and para states are strongly forbidden and herewith this indicator is preserved over time. Most of our knowledge of this indicator comes from the measurements of the ortho-para ratios in water and NH_2 (a proxy for ammonia), suggesting a common T_{spin} near 30 K. 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 (C_2H_6), methane (CH_4), and methanol (CH_3OH), and advanced new models for ortho/para water (H_2O) and ammonia (NH_3). Our H_2O 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 a non-resonant cascade. In a similar fashion, we developed non-resonant fluorescence models for NH_3 and HCN, and quantum-band models for the ν_7 band of C_2H_6 and ν_3 band of CH_3OH. 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 H_2O, CH_4, C_2H_6, CH_3OH, and NH_3 from three high
NASA Astrophysics Data System (ADS)
Rat, Sylvain; Mikolasek, Mirko; Costá, José Sánchez; Chumakov, Aleksandr I.; Nicolazzi, William; Molnár, Gábor; Salmon, Lionel; Bousseksou, Azzedine
2016-06-01
We report on a combined nuclear inelastic scattering and metal isotope substitution based Raman spectroscopic investigation of lattice dynamics changes associated with the spin transition in the ferrous complex [Fe(H2B(pz)2)2(phen)] (pz = pyrazolyl, phen = 1,10-phenantroline). These techniques allowed us to identify Raman active metal - ligand stretching vibrations in the high spin (vHS = 232 cm-1) and low spin (vLS = 390 cm-1) states as well as to calculate associated changes of the Debye temperature (ΘDHS = 140 K, ΘDLS = 146 K), Debye sound velocity (vHS = 1282 m/s, vLS = 1300 m/s) and Young's modulus (EHS = 4.7 GPa, ELS = 5.2 GPa).
NASA Astrophysics Data System (ADS)
Ball, R. C.; Callaghan, P. T.; Samulski, E. T.
1997-05-01
We derive closed-form expressions for a sine correlation function β(2τ,τ) which is particularly sensitive to modulations of nuclear dipolar (and quadrupolar) interactions caused by slow molecular reorientations. This function is placed in the context of traditional nuclear magnetic resonance (NMR) experiments—the Free Induction Decay R(t) and the solid echo amplitude E(τ) and families of expressions are evaluated for (i) motion governed by an exponential correlation function and (ii) macromolecular motion dominated by reptation. We introduce a simple correlation function for reptation that depends on only two parameters, M2¯, the preaveraged dipolar interaction strength and τd, the tube disengagement time. From proton NMR measurements of β in poly(dimethyl siloxane) melts we estimate M2¯=1.3×106s-2 and τd=0.019 s at 300 K, in reasonable agreement with a calculated value for M2¯ and an independent NMR estimate of the terminal relaxation time.
Komorovsky, Stanislav; Repisky, Michal; Malkin, Elena; Demissie, Taye B; Ruud, Kenneth
2015-08-11
We present an implementation of the nuclear spin-rotation (SR) constants based on the relativistic four-component Dirac-Coulomb Hamiltonian. This formalism has been implemented in the framework of the Hartree-Fock and Kohn-Sham theory, allowing assessment of both pure and hybrid exchange-correlation functionals. In the density-functional theory (DFT) implementation of the response equations, a noncollinear generalized gradient approximation (GGA) has been used. The present approach enforces a restricted kinetic balance condition for the small-component basis at the integral level, leading to very efficient calculations of the property. We apply the methodology to study relativistic effects on the spin-rotation constants by performing calculations on XHn (n = 1-4) for all elements X in the p-block of the periodic table and comparing the effects of relativity on the nuclear SR tensors to that observed for the nuclear magnetic shielding tensors. Correlation effects as described by the density-functional theory are shown to be significant for the spin-rotation constants, whereas the differences between the use of GGA and hybrid density functionals are much smaller. Our calculated relativistic spin-rotation constants at the DFT level of theory are only in fair agreement with available experimental data. It is shown that the scaling of the relativistic effects for the spin-rotation constants (varying between Z(3.8) and Z(4.5)) is as strong as for the chemical shieldings but with a much smaller prefactor. PMID:26574455
Magliozzo, R S; Peisach, J
1993-08-24
Electron spin echo envelope modulation (ESEEM) spectroscopy and computer simulation of spectra has been used to evaluate the nitrogen nuclear hyperfine and quadrupole coupling parameters for the proximal imidazole nitrogen directly coordinated to iron in three low-spin heme complexes, myoglobin-azide, -cyanide, and -mercaptoethanol (MbN3, MbCN, and MbRS). The variability in the weak electron-nuclear coupling parameters reveals the electronic flexibility within the heme group that depends on properties of the exogenous ligands. For example, the isotropic component of the nitrogen nuclear hyperfine coupling ranges from 4.4 MHz for MbN3 to 2.2 MHz for both MbCN and MbRS. The weaker coupling in MbCN and MbRS is taken as evidence for delocalization of unpaired electron spin from iron into the exogenous anionic ligands. The value of e2Qq, the nuclear quadrupole coupling constant for the axial imidazole nitrogen in MbCN and MbRS, was 2.5 MHz but was significantly larger, 3.2 MHz, in MbN3. This large value is considered evidence for a weakened sigma bond between the proximal imidazole and ferric iron in this form, and for a feature contributing to the origin of the high spin-low spin equilibrium exhibited by MbN3 [Beetlestone, J., & George, P. (1964) Biochemistry 5, 707-714]. The ESEEM results have allowed a correlation to be made between the orientation of the g tensor axes, the orientation of the p-pi orbital of the proximal imidazole nitrogen, and sigma- and pi-bonding features of the axial ligands. Furthermore, the proximal imidazole is suggested to act as a pi-acceptor in low-spin heme complexes in order to support strong sigma electron donation from the lone pair orbital to iron. An evaluation of the nitrogen nuclear hyperfine coupling parameters for the porphyrin pyrrole sites in MbRS reveals a large inequivalence in isotropic components consistent with an orientation of rhombic axes (and g tensor axes) that eclipses the Fe-Npyrrole vector directions. PMID:8395204
Theis, Thomas; Ortiz, Gerardo X.; Logan, Angus W. J.; Claytor, Kevin E.; Feng, Yesu; Huhn, William P.; Blum, Volker; Malcolmson, Steven J.; Chekmenev, Eduard Y.; Wang, Qiu; Warren, Warren S.
2016-01-01
Conventional magnetic resonance (MR) faces serious sensitivity limitations which can be overcome by hyperpolarization methods, but the most common method (dynamic nuclear polarization) is complex and expensive, and applications are limited by short spin lifetimes (typically seconds) of biologically relevant molecules. We use a recently developed method, SABRE-SHEATH, to directly hyperpolarize 15N2 magnetization and long-lived 15N2 singlet spin order, with signal decay time constants of 5.8 and 23 minutes, respectively. We find >10,000-fold enhancements generating detectable nuclear MR signals that last for over an hour. 15N2-diazirines represent a class of particularly promising and versatile molecular tags, and can be incorporated into a wide range of biomolecules without significantly altering molecular function. PMID:27051867
Bohler, C.L.; Schearer, L.D.; Leduc, M.; Nacher, P.J.; Zachorowski, L.; Milner, R.G.; McKeown, R.D.; Woodward, C.E.
1988-04-15
Several Nd:YAP lasers were constructed which could be broadly tuned in the 1083-nm region which includes the helium 2/sup 3/S-2/sup 3/P transition, using a Lyot filter and thin, uncoated etalons within the laser cavity. 1 W of power could be extracted at 1083 nm through a 1% transmitting output coupler. This laser beam was used to optically pump metastable /sup 4/He and /sup 3/He 2/sup 3/S helium atoms in a weak discharge cell, spin polarizing the metastable ensemble. In a /sup 3/He cell the polarization is transferred to the nuclear spin system. A /sup 3/He target cell at 0.3 Torr was polarized to 52% in a few minutes. We describe the application of this system to the design of polarized targets for experiments in nuclear physics.
NASA Astrophysics Data System (ADS)
Mounce, A. M.; Yasuoka, H.; Koutroulakis, G.; Ni, N.; Bauer, E. D.; Ronning, F.; Thompson, J. D.
2015-03-01
Nuclear magnetic resonance (NMR) measurements on the 195Pt nucleus in an aligned powder of the moderately heavy-fermion material U2PtC2 are consistent with spin-triplet pairing in its superconducting state. Across the superconducting transition temperature and to much lower temperatures, the NMR Knight shift is temperature independent for field both parallel and perpendicular to the tetragonal c axis, expected for triplet equal-spin pairing superconductivity. The NMR spin-lattice relaxation rate 1 /T1, in the normal state, exhibits characteristics of ferromagnetic fluctuations, compatible with an enhanced Wilson ratio. In the superconducting state, 1 /T1 follows a power law with temperature without a coherence peak giving additional support that U2PtC2 is an unconventional superconductor. Bulk measurements of the ac susceptibility and resistivity indicate that the upper critical field exceeds the Pauli limiting field for spin-singlet pairing and is near the orbital limiting field, an additional indication for spin-triplet pairing.
(1)H and (13)C magic-angle spinning nuclear magnetic resonance studies of the chicken eggshell.
Pisklak, Dariusz Maciej; Szeleszczuk, Lukasz; Wawer, Iwona
2012-12-19
The chicken eggshell, a product of biomineralization, contains inorganic and organic substances whose content changes during the incubation process. Bloch-decay (BD) (1)H, (13)C, and cross-polarization (CP) (13)C nuclear magnetic resonance (NMR) spectra of chicken eggshells were acquired under magic-angle spinning (MAS). Variable contact time (13)C CP MAS NMR experiments revealed the signals of carbonyl groups from organic and inorganic compounds. In the (13)C BD NMR spectra, a single peak at 168.1 ppm was detected, whereas in the (1)H BD spectra, the signals from water and the bicarbonate ion were assigned. A simultaneous decrease of the water signal in the (1)H MAS NMR spectra and an increase of the carbonate ion signal in the (13)C CP MAS NMR spectra of eggshells collected during the incubation period indicate the substitution of calcium ions by hydrogen ions in the calcium carbonate crystalline phase during the incubation of an egg. PMID:23157303
Chatterji, T; Jalarvo, N; Kumar, C M N; Xiao, Y; Brückel, Th
2013-07-17
We have investigated low energy nuclear spin excitations in the strongly correlated electron compound HoCrO3. We observe clear inelastic peaks at E = 22.18 ± 0.04 μeV in both energy loss and gain sides. The energy of the inelastic peaks remains constant in the temperature range 1.5-40 K at which they are observed. The intensity of the inelastic peak increases at first with increasing temperature and then decreases at higher temperatures. The temperature dependence of the energy and intensity of the inelastic peaks is very unusual compared to that observed in other Nd, Co, V and also simple Ho compounds. Huge quasielastic scattering appears at higher temperatures presumably due to the fluctuating electronic moments of the Ho ions that get increasingly disordered at higher temperatures. The strong quasielastic scattering may also originate in the first Ho crystal-field excitations at about 1.5 meV. PMID:23779198
THE LOW-TEMPERATURE NUCLEAR SPIN EQUILIBRIUM OF H{sup +} {sub 3} IN COLLISIONS WITH H{sub 2}
Grussie, F.; Berg, M. H.; Wolf, A.; Kreckel, H.; Crabtree, K. N.; McCall, B. J.; Gaertner, S.; Schlemmer, S.
2012-11-01
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.
Crabtree, Kyle N.; Kauffman, Carrie A.; Tom, Brian A.; Becka, Eftalda; McGuire, Brett A.; McCall, Benjamin J.
2011-05-21
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.
Nuclear spin dependence of the reaction of H{sub 3}{sup +} with H{sub 2}. I. Kinetics and modeling
Crabtree, Kyle N.; Tom, Brian A.; McCall, Benjamin J.
2011-05-21
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}.
Cutsail, George E.; Telser, Joshua; Hoffman, Brian M.
2015-01-01
The advanced electron paramagnetic resonance (EPR) techniques, electron nuclear double resonance (ENDOR) and electron spin echo envelope modulation (ESEEM) spectroscopies, provide unique insights into the structure, coordination chemistry, and biochemical mechanism of Nature’s widely distributed iron-sulfur cluster (FeS) proteins. This review describes the ENDOR and ESEEM techniques and then provides a series of case studies on their application to a wide variety of FeS proteins including ferredoxins, nitrogenase, and radical SAM enzymes. PMID:25686535
NASA Astrophysics Data System (ADS)
McCarney, Evan R.; Han, Songi
2008-02-01
Dynamic nuclear polarization (DNP) has recently received much attention as a viable approach to enhance the sensitivity of nuclear magnetic resonance (NMR) spectroscopy and the contrast of magnetic resonance imaging (MRI), where the significantly higher electron spin polarization of stable radicals is transferred to nuclear spins. In order to apply DNP-enhanced NMR and MRI signal to biological and in vivo systems, it is crucial to obtain highly polarized solution samples at ambient temperatures. As stable radicals are employed as the source for the DNP polarization transfer, it is also crucial that the highly polarized sample lacks residual radical concentration because the polarized molecules will be introduced to a biological system that will be sensitive to the presence of radicals. We developed an agarose-based porous media that is covalently spin-labeled with stable radicals. The loading of solvent accessible radical is sufficiently high and their mobility approximates that in solution, which ensures high efficiency for Overhauser mechanism induced DNP without physically releasing any measurable radical into the solution. Under ambient conditions at 0.35 T magnetic field, we measure the DNP enhancement efficiency of 1H signal of stagnant and continuously flowing water utilizing immobilized stable nitroxide radicals that contain two or three ESR hyperfine splitting lines and compare them to the performance of freely dissolved radicals.
NASA Astrophysics Data System (ADS)
Cui, J.; Roy, B.; Tanatar, M. A.; Ran, S.; Bud'ko, S. L.; Prozorov, R.; Canfield, P. C.; Furukawa, Y.
2015-11-01
We report 75As nuclear magnetic resonance (NMR) measurements of single-crystalline Ca (Fe1-xCox) 2As2 (x =0.023 , 0.028, 0.033, and 0.059) annealed at 350 °C for 7 days. From the observation of a characteristic shape of 75As NMR spectra in the stripe-type antiferromagnetic (AFM) state, as in the case of x =0 (TN=170 K), clear evidence for the commensurate AFM phase transition with the concomitant structural phase transition is observed in x =0.023 (TN=106 K) and x =0.028 (TN=53 K). Through the temperature dependence of the Knight shifts and the nuclear spin lattice relaxation rates (1 /T1 ), although stripe-type AFM spin fluctuations are realized in the paramagnetic state as in the case of other iron pnictide superconductors, we found a gradual decrease of the AFM spin fluctuations below a crossover temperature T* that was nearly independent of Co-substitution concentration, and it is attributed to a pseudogaplike behavior in the spin excitation spectra of these systems. The T* feature finds correlation with features in the temperature-dependent interplane resistivity, ρc(T ) , but not with the in-plane resistivity ρa(T ) . The temperature evolution of anisotropic stripe-type AFM spin fluctuations is tracked in the paramagnetic and pseudogap phases by the 1 /T1 data measured under magnetic fields parallel and perpendicular to the c axis. Based on our NMR data, we have added a pseudogaplike phase to the magnetic and electronic phase diagram of Ca (Fe1-xCox) 2As2 .
Cui, J.; Roy, B.; Tanatar, M. A.; Ran, S.; Bud'ko, S. L.; Prozorov, R.; Canfield, P. C.; Furukawa, Y.
2015-11-06
We report 75As nuclear magnetic resonance (NMR) measurements of single-crystalline Ca(Fe1–xCox)2As2 (x=0.023, 0.028, 0.033, and 0.059) annealed at 350°C for 7 days. From the observation of a characteristic shape of 75As NMR spectra in the stripe-type antiferromagnetic (AFM) state, as in the case of x=0 (TN=170 K), clear evidence for the commensurate AFM phase transition with the concomitant structural phase transition is observed in x=0.023 (TN=106 K) and x=0.028 (TN=53 K). Through the temperature dependence of the Knight shifts and the nuclear spin lattice relaxation rates (1/T1), although stripe-type AFM spin fluctuations are realized in the paramagnetic state as inmore » the case of other iron pnictide superconductors, we found a gradual decrease of the AFM spin fluctuations below a crossover temperature T* that was nearly independent of Co-substitution concentration, and it is attributed to a pseudogaplike behavior in the spin excitation spectra of these systems. The T* feature finds correlation with features in the temperature-dependent interplane resistivity, ρc(T), but not with the in-plane resistivity ρa(T). The temperature evolution of anisotropic stripe-type AFM spin fluctuations is tracked in the paramagnetic and pseudogap phases by the 1/T1 data measured under magnetic fields parallel and perpendicular to the c axis. As a result, based on our NMR data, we have added a pseudogaplike phase to the magnetic and electronic phase diagram of Ca(Fe1–xCox)2As2.« less
Li, Jia V; Holmes, Elaine; Saric, Jasmina; Keiser, Jennifer; Dirnhofer, Stephan; Utzinger, Jürg; Wang, Yulan
2009-04-01
In order to enhance our understanding of physiological and pathological consequences of a patent Schistosoma mansoni infection in the mouse, we examined the metabolic responses of different tissue samples recovered from the host animal using a metabolic profiling strategy. Ten female NMRI mice were infected with approximately 80 S. mansoni cercariae each, and 10 uninfected age- and sex-matched animals served as controls. At day 74 post infection (p.i.), mice were killed and jejunum, ileum, colon, liver, spleen and kidney samples were removed. We employed (1)H magic angle spinning-nuclear magnetic resonance spectroscopy to generate tissue-specific metabolic profiles. The spectral data were analyzed using multivariate modelling methods including an orthogonal signal corrected-projection to latent structure analysis and hierarchical principal component analysis to assess the differences and/or similarities in metabolic responses between infected and non-infected control mice. Most tissues obtained from S. mansoni-infected mice were characterized by high levels of amino acids, such as leucine, isoleucine, lysine, glutamine and asparagine. High levels of membrane phospholipid metabolites, including glycerophosphoryl choline and phosphoryl choline were found in the ileum, colon, liver and spleen of infected mice. Additionally, low levels of energy-related metabolites, including lipids, glucose and glycogen were observed in ileum, spleen and liver samples of infected mice. Energy-related metabolites in the jejunum, liver and renal medulla were found to be positively correlated with S. mansoni worm burden upon dissection. These findings show that a patent S. mansoni infection causes clear disruption of metabolism in a range of tissues at a molecular level, which can be interpreted in relation to the previously reported signature in a biofluid (i.e. urine), giving further evidence of the global effect of the infection. PMID:19068218
Hu, Jian Z.
2011-05-01
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.
NASA Astrophysics Data System (ADS)
Martel, L.; Somers, J.; Berkmann, C.; Koepp, F.; Rothermel, A.; Pauvert, O.; Selfslag, C.; Farnan, I.
2013-05-01
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.
NASA Astrophysics Data System (ADS)
Baek, S.-H.; Klingeler, R.; Neef, C.; Koo, C.; Büchner, B.; Grafe, H.-J.
2014-04-01
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 Θ and the effective magnetic moment μeff 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.
NASA Astrophysics Data System (ADS)
Appelbaum, Ian
2008-03-01
Silicon has been broadly viewed as the ideal material for spintronics due to its low atomic weight, lattice inversion symmetry, and near lack of nuclear spin, resulting in exceptionally long spin lifetime. Despite this appeal, however, the experimental difficulties of achieving coherent spin transport in silicon were overcome for the first time only recently, by using unique spin-polarized hot-electron injection and detection techniques. [1] Our subsequent observations of very long spin lifetimes and transit lengths [2] have impact on prospects for Silicon spintronics as the basis for a new paradigm of information processing. [1] Ian Appelbaum, Biqin Huang, and Douwe J. Monsma, ``Electronic measurement and control of spin transport in silicon,'' Nature 447, 295 (2007). [2] Biqin Huang, Douwe J. Monsma, and Ian Appelbaum, ``Coherent spin transport through a 350-micron-thick silicon wafer,'' Phys. Rev. Lett. 99, 177209 (2007).
Mahata, Sasadhar; Bhattacharya, S. K.
2009-06-21
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.
NASA Astrophysics Data System (ADS)
Miranowicz, Adam; Ã-zdemir, Şahin K.; Bajer, Jiří; Yusa, Go; Imoto, Nobuyuki; Hirayama, Yoshiro; Nori, Franco
2015-08-01
We discuss methods of quantum state tomography for solid-state systems with a large nuclear spin I =3 /2 in nanometer-scale semiconductors devices based on a quantum well. Due to quadrupolar interactions, the Zeeman levels of these nuclear-spin devices become nonequidistant, forming a controllable four-level quantum system (known as quartit or ququart). The occupation of these levels can be selectively and coherently manipulated by multiphoton transitions using the techniques of nuclear magnetic resonance (NMR) [Yusa et al., Nature (London) 434, 1001 (2005), 10.1038/nature03456]. These methods are based on an unconventional approach to NMR, where the longitudinal magnetization Mz is directly measured. This is in contrast to the standard NMR experiments and tomographic methods, where the transverse magnetization Mx y is detected. The robustness against errors in the measured data is analyzed by using the condition number based on the spectral norm. We propose several methods with optimized sets of rotations yielding the highest robustness against errors, as described by the condition number equal to 1, assuming an ideal experimental detection. This robustness is only slightly deteriorated, as given by the condition number equal to 1.05, for a more realistic "noisy" Mz detection based on the standard cyclically ordered phase sequence (CYCLOPS) method.
NASA Astrophysics Data System (ADS)
Chang, Zhiwei; Halle, Bertil
2016-02-01
In aqueous systems with immobilized macromolecules, including biological tissue, the longitudinal spin relaxation of water protons is primarily induced by exchange-mediated orientational randomization (EMOR) of intra- and intermolecular magnetic dipole-dipole couplings. We have embarked on a systematic program to develop, from the stochastic Liouville equation, a general and rigorous theory that can describe relaxation by the dipolar EMOR mechanism over the full range of exchange rates, dipole coupling strengths, and Larmor frequencies. Here, we present a general theoretical framework applicable to spin systems of arbitrary size with symmetric or asymmetric exchange. So far, the dipolar EMOR theory is only available for a two-spin system with symmetric exchange. Asymmetric exchange, when the spin system is fragmented by the exchange, introduces new and unexpected phenomena. Notably, the anisotropic dipole couplings of non-exchanging spins break the axial symmetry in spin Liouville space, thereby opening up new relaxation channels in the locally anisotropic sites, including longitudinal-transverse cross relaxation. Such cross-mode relaxation operates only at low fields; at higher fields it becomes nonsecular, leading to an unusual inverted relaxation dispersion that splits the extreme-narrowing regime into two sub-regimes. The general dipolar EMOR theory is illustrated here by a detailed analysis of the asymmetric two-spin case, for which we present relaxation dispersion profiles over a wide range of conditions as well as analytical results for integral relaxation rates and time-dependent spin modes in the zero-field and motional-narrowing regimes. The general theoretical framework presented here will enable a quantitative analysis of frequency-dependent water-proton longitudinal relaxation in model systems with immobilized macromolecules and, ultimately, will provide a rigorous link between relaxation-based magnetic resonance image contrast and molecular parameters.
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...
Single spin magnetic resonance
NASA Astrophysics Data System (ADS)
Wrachtrup, Jörg; Finkler, Amit
2016-08-01
Different approaches have improved the sensitivity of either electron or nuclear magnetic resonance to the single spin level. For optical detection it has essentially become routine to observe a single electron spin or nuclear spin. Typically, the systems in use are carefully designed to allow for single spin detection and manipulation, and of those systems, diamond spin defects rank very high, being so robust that they can be addressed, read out and coherently controlled even under ambient conditions and in a versatile set of nanostructures. This renders them as a new type of sensor, which has been shown to detect single electron and nuclear spins among other quantities like force, pressure and temperature. Adapting pulse sequences from classic NMR and EPR, and combined with high resolution optical microscopy, proximity to the target sample and nanoscale size, the diamond sensors have the potential to constitute a new class of magnetic resonance detectors with single spin sensitivity. As diamond sensors can be operated under ambient conditions, they offer potential application across a multitude of disciplines. Here we review the different existing techniques for magnetic resonance, with a focus on diamond defect spin sensors, showing their potential as versatile sensors for ultra-sensitive magnetic resonance with nanoscale spatial resolution.
Single spin magnetic resonance.
Wrachtrup, Jörg; Finkler, Amit
2016-08-01
Different approaches have improved the sensitivity of either electron or nuclear magnetic resonance to the single spin level. For optical detection it has essentially become routine to observe a single electron spin or nuclear spin. Typically, the systems in use are carefully designed to allow for single spin detection and manipulation, and of those systems, diamond spin defects rank very high, being so robust that they can be addressed, read out and coherently controlled even under ambient conditions and in a versatile set of nanostructures. This renders them as a new type of sensor, which has been shown to detect single electron and nuclear spins among other quantities like force, pressure and temperature. Adapting pulse sequences from classic NMR and EPR, and combined with high resolution optical microscopy, proximity to the target sample and nanoscale size, the diamond sensors have the potential to constitute a new class of magnetic resonance detectors with single spin sensitivity. As diamond sensors can be operated under ambient conditions, they offer potential application across a multitude of disciplines. Here we review the different existing techniques for magnetic resonance, with a focus on diamond defect spin sensors, showing their potential as versatile sensors for ultra-sensitive magnetic resonance with nanoscale spatial resolution. PMID:27378060
Cutsail, George E; Telser, Joshua; Hoffman, Brian M
2015-06-01
The advanced electron paramagnetic resonance (EPR) techniques, electron nuclear double resonance (ENDOR) and electron spin echo envelope modulation (ESEEM) spectroscopies, provide unique insights into the structure, coordination chemistry, and biochemical mechanism of nature's widely distributed iron-sulfur cluster (FeS) proteins. This review describes the ENDOR and ESEEM techniques and then provides a series of case studies on their application to a wide variety of FeS proteins including ferredoxins, nitrogenase, and radical SAM enzymes. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases. PMID:25686535
NASA Astrophysics Data System (ADS)
Nath, Nilamoni; Suryaprakash, N.
2010-08-01
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.
Demissie, Taye B; Jaszuński, Michał; Komorovsky, Stanislav; Repisky, Michal; Ruud, Kenneth
2015-10-28
We present nuclear spin-rotation constants, absolute nuclear magnetic resonance (NMR) shielding constants, and shielding spans of all the nuclei in (175)LuX and (197)AuX (X = (19)F, (35)Cl, (79)Br, (127)I), calculated using coupled-cluster singles-and-doubles with a perturbative triples (CCSD(T)) correction theory, four-component relativistic density functional theory (relativistic DFT), and non-relativistic DFT. The total nuclear spin-rotation constants determined by adding the relativistic corrections obtained from DFT calculations to the CCSD(T) values are in general in agreement with available experimental data, indicating that the computational approach followed in this study allows us to predict reliable results for the unknown spin-rotation constants in these molecules. The total NMR absolute shielding constants are determined for all the nuclei following the same approach as that applied for the nuclear spin-rotation constants. In most of the molecules, relativistic effects significantly change the computed shielding constants, demonstrating that straightforward application of the non-relativistic formula relating the electronic contribution to the nuclear spin-rotation constants and the paramagnetic contribution to the shielding constants does not yield correct results. We also analyze the origin of the unusually large absolute shielding constant and its relativistic correction of gold in AuF compared to the other gold monohalides. PMID:26520517
NASA Astrophysics Data System (ADS)
Demissie, Taye B.; Jaszuński, Michał; Komorovsky, Stanislav; Repisky, Michal; Ruud, Kenneth
2015-10-01
We present nuclear spin-rotation constants, absolute nuclear magnetic resonance (NMR) shielding constants, and shielding spans of all the nuclei in 175LuX and 197AuX (X = 19F, 35Cl, 79Br, 127I), calculated using coupled-cluster singles-and-doubles with a perturbative triples (CCSD(T)) correction theory, four-component relativistic density functional theory (relativistic DFT), and non-relativistic DFT. The total nuclear spin-rotation constants determined by adding the relativistic corrections obtained from DFT calculations to the CCSD(T) values are in general in agreement with available experimental data, indicating that the computational approach followed in this study allows us to predict reliable results for the unknown spin-rotation constants in these molecules. The total NMR absolute shielding constants are determined for all the nuclei following the same approach as that applied for the nuclear spin-rotation constants. In most of the molecules, relativistic effects significantly change the computed shielding constants, demonstrating that straightforward application of the non-relativistic formula relating the electronic contribution to the nuclear spin-rotation constants and the paramagnetic contribution to the shielding constants does not yield correct results. We also analyze the origin of the unusually large absolute shielding constant and its relativistic correction of gold in AuF compared to the other gold monohalides.
NASA Astrophysics Data System (ADS)
Tekely, Piotr; Gardiennet, Carole; Potrzebowski, Marek J.; Sebald, Angelika; Reichert, Detlef; Luz, Zeev
2002-05-01
Exploration of the molecular geometry in rotating powder solids on the basis of magnetization exchange between spins with identical isotropic chemical shifts but differing chemical shielding tensor orientations is demonstrated experimentally. For this we take advantage of the potential of the ODESSA (one-dimensional exchange spectroscopy by sidebands alternation) experiment for the accurate measurement of spin exchange rate constants. We also report the observation of oscillatory behavior of the rotor-driven magnetization exchange at this so-called n=0 rotational-resonance condition which, in contrast to n=1,2,3,… rotational-resonance conditions, takes place at nearly arbitrary magic-angle spinning frequencies. The sensitivity of the longitudinal exchange decays to the relevant physical parameters of the spin system under conditions of rotor-driven and proton-driven magnetization exchange is discussed theoretically and demonstrated experimentally. Several 13C and 31P spin-exchange measurements have been performed on a series of model compounds covering a broad range of internuclear distances between carboxyl carbon atoms, and on a series of phosphorylated amino acids with different internuclear distances between phosphorus sites. The capacity of the ODESSA experiment for an unambiguous recognition of distinct internuclear distances is demonstrated. Potential applications of such measurements involve the exploration of intermolecular distances and the determination of the mutual orientation of neighboring molecular fragments in polycrystalline and noncrystalline solids.
Wood, R. M.; Saha, D.; McCarthy, L. A.; Tokarski, III, J. T.; Sanders, G. D.; Kuhns, P. L.; McGill, S. A.; Reyes, A. P.; Reno, J. L.; Stanton, C. J.; et al
2014-10-29
A combined experimental-theoretical study of optically pumped NMR (OPNMR) has been performed in a GaAs/Al0.1Ga0.9As quantum well film with thermally induced biaxial strain. The photon energy dependence of the Ga-71 OPNMR signal was recorded at magnetic fields of 4.9 and 9.4 T at a temperature of 4.8-5.4 K. The data were compared to the nuclear spin polarization calculated from differential absorption to spin-up and spin-down states of the conduction band using a modified Pidgeon Brown model. Reasonable agreement between theory and experiment is obtained, facilitating assignment of features in the OPNMR energy dependence to specific interband transitions. Despite the approximationsmore » made in the quantum-mechanical model and the inexact correspondence between the experimental and calculated observables, the results provide insight into how effects of strain and quantum confinement are manifested in OPNMR signals« less
Wood, R. M.; Saha, D.; McCarthy, L. A.; Tokarski, III, J. T.; Sanders, G. D.; Kuhns, P. L.; McGill, S. A.; Reyes, A. P.; Reno, J. L.; Stanton, C. J.; Bowers, C. R.
2014-10-29
A combined experimental-theoretical study of optically pumped NMR (OPNMR) has been performed in a GaAs/Al_{0.1}Ga_{0.9}As quantum well film with thermally induced biaxial strain. The photon energy dependence of the Ga-71 OPNMR signal was recorded at magnetic fields of 4.9 and 9.4 T at a temperature of 4.8-5.4 K. The data were compared to the nuclear spin polarization calculated from differential absorption to spin-up and spin-down states of the conduction band using a modified Pidgeon Brown model. Reasonable agreement between theory and experiment is obtained, facilitating assignment of features in the OPNMR energy dependence to specific interband transitions. Despite the approximations made in the quantum-mechanical model and the inexact correspondence between the experimental and calculated observables, the results provide insight into how effects of strain and quantum confinement are manifested in OPNMR signals
Challoner, R; Sebald, A
1995-01-01
31P and 195Pt cross-polarization magic-angle spinning nuclear magnetic resonance (CP-MAS NMR) spectra of three platinum complexes of formal oxidation state Pt(0) and Pt(II), respectively, are reported. All three complexes, (Ph3P)2Pt(C2H4) (1), (Et2P-CH2-CH2-PEt2)Pt(C identical to C-H)2 (2) and (Ph2P-CH2-CH2-PPh2)Pt(C identical to C-C(CH3)=CH2)2 (3) contain the square-planar cis-P2PtC2 fragment and show unusual NMR spectroscopic properties insofar that the 195Pt shielding patterns are fairly narrow in relation to what one would generally have to expect for 195Pt in square-planar coordination. Another unexpected NMR property of the cis-P2PtC2 fragment in 1-3 is the absence of spinning frequency-dependent second-order effects in this solid-state ABX spin system. PMID:7894980
Lafon, Olivier; Thankamony, Aany S. Lilly; Kokayashi, Takeshi; Carnevale, Diego; Vitzthum, Veronika; Slowing, Igor I.; Kandel, Kapil; Vezin, Herve; Amoureux, Jean-Paul; Bodenhausen, Geoffrey; Pruski, Marek
2012-12-21
We show that dynamic nuclear polarization (DNP) can be used to enhance NMR signals of 13C and 29Si nuclei located in mesoporous organic/inorganic hybrid materials, at several hundreds of nanometers from stable radicals (TOTAPOL) trapped in the surrounding frozen disordered water. The approach is demonstrated using mesoporous silica nanoparticles (MSN), functionalized with 3-(N-phenylureido)propyl (PUP) groups, filled with the surfactant cetyltrimethylammonium bromide (CTAB). The DNP-enhanced proton magnetization is transported into the mesopores via 1H–1H spin diffusion and transferred to rare spins by cross-polarization, yielding signal enhancements εon/off of around 8. When the CTAB molecules are extracted, so that the radicals can enter the mesopores, the enhancements increase to εon/off ≈ 30 for both nuclei. A quantitative analysis of the signal enhancements in MSN with and without surfactant is based on a one-dimensional proton spin diffusion model. The effect of solvent deuteration is also investigated.
NASA Astrophysics Data System (ADS)
Nielsen, N. C.; Bildsøe, H.; Jakobsen, H. J.; Levitt, M. H.
1994-08-01
We describe an efficient method for the recovery of homonuclear dipole-dipole interactions in magic-angle spinning NMR. Double-quantum homonuclear rotary resonance (2Q-HORROR) is established by fulfilling the condition ωr=2ω1, where ωr is the sample rotation frequency and ω1 is the nutation frequency around an applied resonant radio frequency (rf) field. This resonance can be used for double-quantum filtering and measurement of homonuclear dipolar interactions in the presence of magic-angle spinning. The spin dynamics depend only weakly on crystallite orientation allowing good performance for powder samples. Chemical shift effects are suppressed to zeroth order. The method is demonstrated for singly and doubly 13C labeled L-alanine.
Little, Reginald B; McClary, Felicia; Rice, Bria; Jackman, Corine; Mitchell, James W
2012-12-14
The recent observation of the explosive oxidation of graphene with enhancement for decreasing temperature and the requirements for synchronizing oxidants for collective oxidation-reduction (redox) reactions presented a chemical scenario for the thermal harvesting by the magnetic spin Hall Effect. More experimental data are presented to demonstrate such spin Hall Effect by determining the influence of spins of so-called spectator fermionic cations. Furthermore, the so-called spectator bosonic cations are discovered to cause a Klein tunneling effect during the redox reaction of graphene. The Na(+) and K(+), fermionic cations and the Mg(2+) and Ca(2+), bosonic cations were observed and compared under a variety of experimental conditions: adiabatic reactions with initial temperatures (18-22 °C); reactions toward infinite dilution; isothermal reactions under nonadiabatic conditions at low temperature of 18 °C; reactions under paramagnetic O(2) or diamagnetic N(2) atmospheres of different permeabilities; reactions in applied and no applied external magnetic field; and reactions toward excess concentrations of common and uncommon Na(+) and Mg(2+) cations. The observed reaction kinetics and dynamics under these various, diverse conditions are consistent with the spin Hall mechanism, energy harvesting and short time violation of Second Law of Thermodynamics for redox reactions of graphene by the Na(+)K(+) mixture and are consistent with the Klein tunnel mechanism for the redox reactions of graphene by the Mg(2+)Ca(2+) mixture. Mixed spin Hall and Klein tunnel mechanisms are discovered to slow and modulate explosive redox reactions. Such spin Hall Effect also gives explanation of recent tunneling of electrons through boron nitride. PMID:23108034
NASA Astrophysics Data System (ADS)
Liu, X. H.; Luo, H.; Qu, T. L.; Yang, K. Y.; Ding, Z. C.
2015-10-01
We report a novel method of measuring the spin polarization of alkali-metal atoms by detecting the NMR frequency shifts of noble gases. We calculated the profile of 87Rb D1 line absorption cross sections. We then measured the absorption profile of the sample cell, from which we calculated the 87Rb number densities at different temperatures. Then we measured the frequency shifts resulted from the spin polarization of the 87Rb atoms and calculated its polarization degrees at different temperatures. The behavior of frequency shifts versus temperature in experiment was consistent with theoretical calculation, which may be used as compensative signal for the NMRG closed-loop control system.
NASA Astrophysics Data System (ADS)
Ichimura, Kouichi; Goto, Hayato; Nakamura, Satoshi; Kujiraoka, Mamiko
2015-03-01
Nuclear spin states of rare-earth-metal ions in a crystal are known as good candidates for qubits in solids because of their long coherence time and their good controllability by lights. In the frequency-domain quantum computer (FDQC), nuclear spin states of the ions are employed as qubits defined in a frequency domain, and interaction between the qubits is mediated by a single cavity mode. In FDQC we can use adiabatic passage with dark states to perform single-qubit gates and two-qubit gates, and a single-qubit gate using adiabatic passage has been demonstrated. For two-qubit gates, quantum states of qubit ions need to be read out and operated individually. In order to observe a single ion in a crystal, we studied modulated signals due to ions in a cavity-mode spectrum of a monolithic optical cavity made of Pr3+:Y2SiO5. Owing to the cavity enhancement and the electric-field modulation spectroscopy, signals which are likely due to individual ions (statistical fine structure in an inhomogeneously broadened optical trandition) were observed.
NASA Astrophysics Data System (ADS)
Yesinowski, James P.; Ladouceur, Harold D.; Purdy, Andrew P.; Miller, Joel B.
2010-12-01
We investigate experimentally and theoretically the effects of two different types of conductivity, electrical and ionic, upon magic-angle spinning NMR spectra. The experimental demonstration of these effects involves 63Cu, 65Cu, and 127I variable temperature MAS-NMR experiments on samples of γ-CuI, a Cu+-ion conductor at elevated temperatures as well as a wide bandgap semiconductor. We extend previous observations that the chemical shifts depend very strongly upon the square of the spinning-speed as well as the particular sample studied and the magnetic field strength. By using the 207Pb resonance of lead nitrate mixed with the γ-CuI as an internal chemical shift thermometer we show that frictional heating effects of the rotor do not account for the observations. Instead, we find that spinning bulk CuI, a p-type semiconductor due to Cu+ vacancies in nonstoichiometric samples, in a magnetic field generates induced AC electric currents from the Lorentz force that can resistively heat the sample by over 200 °C. These induced currents oscillate along the rotor spinning axis at the spinning speed. Their associated heating effects are disrupted in samples containing inert filler material, indicating the existence of macroscopic current pathways between micron-sized crystallites. Accurate measurements of the temperature-dependence of the 63Cu and 127I chemical shifts in such diluted samples reveal that they are of similar magnitude (ca. 0.27 ppm/K) but opposite sign (being negative for 63Cu), and appear to depend slightly upon the particular sample. This relationship is identical to the corresponding slopes of the chemical shifts versus square of the spinning speed, again consistent with sample heating as the source of the observed large shift changes. Higher drive-gas pressures are required to spin samples that have higher effective electrical conductivities, indicating the presence of a braking effect arising from the induced currents produced by rotating a
Liu, X. H.; Luo, H.; Qu, T. L. Yang, K. Y.; Ding, Z. C.
2015-10-15
We report a novel method of measuring the spin polarization of alkali-metal atoms by detecting the NMR frequency shifts of noble gases. We calculated the profile of {sup 87}Rb D1 line absorption cross sections. We then measured the absorption profile of the sample cell, from which we calculated the {sup 87}Rb number densities at different temperatures. Then we measured the frequency shifts resulted from the spin polarization of the {sup 87}Rb atoms and calculated its polarization degrees at different temperatures. The behavior of frequency shifts versus temperature in experiment was consistent with theoretical calculation, which may be used as compensative signal for the NMRG closed-loop control system.
Nuclear spin-lattice relaxation at field-induced level crossings in a Cr8F8 pivalate single crystal
NASA Astrophysics Data System (ADS)
Yamamoto, Shoji
2016-01-01
We construct a microscopic theory for the proton spin-lattice relaxation-rate 1 / T1 measurements around field-induced level crossings in a single crystal of the trivalent chromium ion wheel complex [Cr8F8(OOCtBu)16] at sufficiently low temperatures [E. Micotti et al., Phys. Rev. B 72 (2005) 020405(R)]. Exactly diagonalizing a well-equipped spin Hamiltonian for the individual clusters and giving further consideration to their possible interactions, we reveal the mechanism of 1 / T1 being single-peaked normally at the first level crossing but double-peaked intriguingly around the second level crossing. We wipe out the doubt about poor crystallization and find out a solution-intramolecular alternating Dzyaloshinsky-Moriya interaction combined with intermolecular coupling of antiferromagnetic character, each of which is so weak as several tens of mK in magnitude.
Yesinowski, James P; Ladouceur, Harold D; Purdy, Andrew P; Miller, Joel B
2010-12-21
We investigate experimentally and theoretically the effects of two different types of conductivity, electrical and ionic, upon magic-angle spinning NMR spectra. The experimental demonstration of these effects involves (63)Cu, (65)Cu, and (127)I variable temperature MAS-NMR experiments on samples of γ-CuI, a Cu(+)-ion conductor at elevated temperatures as well as a wide bandgap semiconductor. We extend previous observations that the chemical shifts depend very strongly upon the square of the spinning-speed as well as the particular sample studied and the magnetic field strength. By using the (207)Pb resonance of lead nitrate mixed with the γ-CuI as an internal chemical shift thermometer we show that frictional heating effects of the rotor do not account for the observations. Instead, we find that spinning bulk CuI, a p-type semiconductor due to Cu(+) vacancies in nonstoichiometric samples, in a magnetic field generates induced AC electric currents from the Lorentz force that can resistively heat the sample by over 200 °C. These induced currents oscillate along the rotor spinning axis at the spinning speed. Their associated heating effects are disrupted in samples containing inert filler material, indicating the existence of macroscopic current pathways between micron-sized crystallites. Accurate measurements of the temperature-dependence of the (63)Cu and (127)I chemical shifts in such diluted samples reveal that they are of similar magnitude (ca. 0.27 ppm/K) but opposite sign (being negative for (63)Cu), and appear to depend slightly upon the particular sample. This relationship is identical to the corresponding slopes of the chemical shifts versus square of the spinning speed, again consistent with sample heating as the source of the observed large shift changes. Higher drive-gas pressures are required to spin samples that have higher effective electrical conductivities, indicating the presence of a braking effect arising from the induced currents produced by
Jankowska, Marzena; Kupka, Teobald; Stobiński, Leszek; Faber, Rasmus; Lacerda, Evanildo G; Sauer, Stephan P A
2016-02-01
Hartree-Fock and density functional theory with the hybrid B3LYP and general gradient KT2 exchange-correlation functionals were used for nonrelativistic and relativistic nuclear magnetic shielding calculations of helium, neon, argon, krypton, and xenon dimers and free atoms. Relativistic corrections were calculated with the scalar and spin-orbit zeroth-order regular approximation Hamiltonian in combination with the large Slater-type basis set QZ4P as well as with the four-component Dirac-Coulomb Hamiltonian using Dyall's acv4z basis sets. The relativistic corrections to the nuclear magnetic shieldings and chemical shifts are combined with nonrelativistic coupled cluster singles and doubles with noniterative triple excitations [CCSD(T)] calculations using the very large polarization-consistent basis sets aug-pcSseg-4 for He, Ne and Ar, aug-pcSseg-3 for Kr, and the AQZP basis set for Xe. For the dimers also, zero-point vibrational (ZPV) corrections are obtained at the CCSD(T) level with the same basis sets were added. Best estimates of the dimer chemical shifts are generated from these nuclear magnetic shieldings and the relative importance of electron correlation, ZPV, and relativistic corrections for the shieldings and chemical shifts is analyzed. PMID:26503739
Lomzov, Alexander A; Sviridov, Eugeniy A; Shernuykov, Andrey V; Shevelev, Georgiy Yu; Pyshnyi, Dmitrii V; Bagryanskaya, Elena G
2016-06-16
Pulse dipole-dipole electron paramagnetic resonance (EPR) spectroscopy (double electron-electron resonance [DEER] or pulse electron-electron double resonance [PELDOR] and double quantum coherence [DQC]) allows for measurement of distances in biomolecules and can be used at low temperatures in a frozen solution. Recently, the possibility of distance measurement in a nucleic acid at a physiological temperature using pulse EPR was demonstrated. In these experiments, triarylmethyl (TAM) radicals with long memory time of the electron spin served as a spin label. In addition, the duplex was immobilized on modified silica gel particles (Nucleosil DMA); this approach enables measurement of interspin distances close to 4.5 nm. Nevertheless, the possible influence of TAM on the structure of a biopolymer under study and validity of the data obtained by DQC are debated. In this paper, a combination of molecular dynamics (MD) and nuclear magnetic resonance (NMR) methods was used for verification of interspin distances measured by the X-band DQC method. NMR is widely used for structural analysis of biomolecules under natural conditions (room temperature and an aqueous solution). The ultraviolet (UV) melting method and thermal series (1)H NMR in the range 5-95 °C revealed the presence of only the DNA duplex in solution at oligonucleotide concentrations 1 μM to 1.1 mM at temperatures below 40 °C. The duplex structures and conformation flexibility of native and TAM-labeled DNA complexes obtained by MD simulation were the same as the structure obtained by NMR refinement. Thus, we showed that distance measurements at physiological temperatures by the X-band DQC method allow researchers to obtain valid structural information on an unperturbed DNA duplex using terminal TAM spin labels. PMID:27195671
NASA Astrophysics Data System (ADS)
Babunts, R. A.; Soltamova, A. A.; Tolmachev, D. O.; Soltamov, V. A.; Gurin, A. S.; Anisimov, A. N.; Preobrazhenskii, V. L.; Baranovi, P. G.
2012-06-01
New method for the detection of magnetic resonance signals versus temperature is developed on the basis of the temperature dependence of the spin Hamiltonian parameters of the paramagnetic system under investigation. The implementation of this technique is demonstrated on the nitrogen-vacancy (NV) centers in diamonds. Single NV defects and their ensembles are suggested to be almost inertialess temperature sensors. The hyperfine structure of the 14N nitrogen nuclei of the nitrogen-vacancy center appears to be resolved in the hyperfine structure characteristic of the hyperfine interaction between NV and an N s center (substitutional nitrogen impurity) in the optically detected magnetic resonance spectra of the molecular NV-N s complex. Thus, we show that a direct evidence of the two-way transfer of a nitrogen nuclear spin hyperfine interaction in coupled NV-N s pairs was observed. It is shown that more than 3-fold enhancement of the NV optically detected magnetic resonance signal can be achieved by using water as a collection optics medium.
Matsuki, Yoh; Ueda, Keisuke; Idehara, Toshitaka; Ikeda, Ryosuke; Ogawa, Isamu; Nakamura, Shinji; Toda, Mitsuru; Anai, Takahiro; Fujiwara, Toshimichi
2012-12-01
We describe a (1)H polarization enhancement via dynamic nuclear polarization (DNP) at very low sample temperature T≈30 K under magic-angle spinning (MAS) conditions for sensitivity-enhanced solid-state NMR measurement. Experiments were conducted at a high external field strength of 14.1 T. For MAS DNP experiments at T<90 K, a new probe system using cold helium gas for both sample-cooling and -spinning was developed. The novel system can sustain a low sample temperature between 30 and 90K for a period of time >10 h under MAS at ν(R)≈3 kHz with liquid He consumption of ≈6 L/h. As a microwave source, we employed a high-power, continuously frequency-tunable gyrotron. At T≈34 K, (1)H DNP enhancement factors of 47 and 23 were observed with and without MAS, respectively. On the basis of these observations, a discussion on the total NMR sensitivity that takes into account the effect of sample temperature and external field strength used in DNP experiments is presented. It was determined that the use of low sample temperature and high external field is generally rewarding for the total sensitivity, in spite of the slower polarization buildup at lower temperature and lower DNP efficiency at higher field. These findings highlight the potential of the current continuous-wave DNP technique also at very high field conditions suitable to analyze large and complex systems, such as biological macromolecules. PMID:23079589
Straus, Suzana K
2004-01-01
In recent years, a large number of solid-state nuclear magnetic resonance (NMR) techniques have been developed and applied to the study of fully or significantly isotopically labelled ((13)C, (15)N or (13)C/(15)N) biomolecules. In the past few years, the first structures of (13)C/(15)N-labelled peptides, Gly-Ile and Met-Leu-Phe, and a protein, Src-homology 3 domain, were solved using magic-angle spinning NMR, without recourse to any structural information obtained from other methods. This progress has been made possible by the development of NMR experiments to assign solid-state spectra and experiments to extract distance and orientational information. Another key aspect to the success of solid-state NMR is the advances made in sample preparation. These improvements will be reviewed in this contribution. Future prospects for the application of solid-state NMR to interesting biological questions will also briefly be discussed. PMID:15306412
Righi, Valeria; Parenti, Francesca; Tugnoli, Vitaliano; Schenetti, Luisa; Mucci, Adele
2015-09-30
Intact Crocus sativus petals were studied for the first time by high-resolution magic angle spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy, revealing the presence of kinsenoside (2) and goodyeroside A (3), together with 3-hydroxy-γ-butyrolactone (4). These findings were confirmed by HR-NMR analysis of the ethanol extract of fresh petals and showed that, even though carried out rapidly, partial hydrolysis of glucopyranosyloxybutanolides occurs during extraction. On the other hand, kaempferol 3-O-sophoroside (1), which is "NMR-silent" in intact petals, is present in extracts. These results suggest to evaluate the utilization of saffron petals for phytopharmaceutical and nutraceutical purposes to exploit a waste product of massive production of commercial saffron and point to the application of HR-MAS NMR for monitoring bioactive compounds directly on intact petals, avoiding the extraction procedure and the consequent hydrolysis reaction. PMID:26367873
Spin-bus concept of spin quantum computing
Mehring, Michael; Mende, Jens
2006-05-15
We present a spin-bus concept of quantum computing where an electron spin S=1/2 acts as a bus qubit connected to a finite number N of nuclear spins I=1/2 serving as client qubits. Spin-bus clusters are considered as local processing units and may be interconnected with other spin-bus clusters via electron-electron coupling in a scaled up version. Here we lay the ground for the basic functional unit with long qubit registers, provide the theory and experimental verification of correlated qubit states, and demonstrate the Deutsch algorithm. Experiments were performed on a qubyte plus one nuclear spin in a solid state system.
NASA Astrophysics Data System (ADS)
Lee, W. W.; Scherr, Lawrence M.; Barsh, Max K.
1988-11-01
Some rotational transitions of ethyl iodide, CH3CH2I, have been reinvestigated by microwave Fourier transform (MWFT) spectroscopy. The iodine hyperfine structure splittings were first ana lyzed using a direct diagonalization procedure of the complete quadrupole Hamiltonian matrix. The results of this analysis showed deviations from our measurements up to 60 kHz. A new analysis using additional spin rotation coupling matrix elements reproduces our measurements within the experimental error limit and decreases the standard deviation of the least squares fit from 28 kHz to only 4 kHz.
Nouicer, R.; Beck, C.; Freeman, R.M.; Haas, F.; Aissaoui, N.; Bellot, T.; de France, G.; Disdier, D.; Duchene, G.; Elanique, A.; Hachem, A.; Hoellinger, F.; Mahboub, D.; Rauch, V.; Szanto de Toledo, A.; Elanique, A.; Mahboub, D.; Cavallaro, S.; Sanders, S.J.; Dummer, A.; Prosser, F.W.; Uegaki, E.; Abe, Y.
1999-10-01
Fragment-fragment-{gamma} coincidences have been measured for {sup 28}Si+{sup 28}Si at an energy corresponding to the population of a conjectured resonance in {sup 56}Ni. Fragment angular distributions as well as {gamma}-ray angular correlations indicate that the spin orientations of the outgoing fragments are perpendicular to the orbital angular momentum. This differs from the {sup 24}Mg+{sup 24}Mg and the {sup 12}C+{sup 12}C resonances, and suggests two oblate {sup 28}Si nuclei interacting in an equator-to-equator molecular configuration. {copyright} {ital 1999} {ital The American Physical Society}
Hu, Jian Zhi; Hu, Mary Y.; Townsend, Mark R.; Lercher, Johannes A.; Peden, Charles H. F.
2015-10-06
Re-usable ceramic magic angle spinning (MAS) NMR rotors constructed of high-mechanic strength ceramics are detailed that include a sample compartment that maintains high pressures up to at least about 200 atmospheres (atm) and high temperatures up to about least about 300.degree. C. during operation. The rotor designs minimize pressure losses stemming from penetration over an extended period of time. The present invention makes possible a variety of in-situ high pressure, high temperature MAS NMR experiments not previously achieved in the prior art.
Geometrical spin symmetry and spin
Pestov, I. B.
2011-07-15
Unification of General Theory of Relativity and Quantum Mechanics leads to General Quantum Mechanics which includes into itself spindynamics as a theory of spin phenomena. The key concepts of spindynamics are geometrical spin symmetry and the spin field (space of defining representation of spin symmetry). The essence of spin is the bipolar structure of geometrical spin symmetry induced by the gravitational potential. The bipolar structure provides a natural derivation of the equations of spindynamics. Spindynamics involves all phenomena connected with spin and provides new understanding of the strong interaction.
NASA Astrophysics Data System (ADS)
Sahoo, B. K.; Aoki, T.; Das, B. P.; Sakemi, Y.
2016-03-01
Employing the relativistic coupled-cluster method, comparative studies of the parity nonconserving electric dipole amplitudes for the 7 s 1/2 2S →6 d 5/2 2D transitions in 210Fr and 211Fr isotopes have been carried out. It is found that these transition amplitudes, sensitive only to the nuclear spin-dependent effects, are enhanced substantially owing to the very large contributions from the electron core-polarization effects in Fr. This translates to a relatively large and, in principle, measurable induced light shift, which would be a signature of nuclear spin-dependent parity nonconservation that is dominated by the nuclear anapole moment in a heavy atom like Fr. A plausible scheme to measure this quantity using the Cyclotron and Radioisotope Center (CYRIC) facility at Tohoku University has been outlined.
Voinov, Alexander V.; Grimes, Steven M.; Brune, Carl R.; Burger, Alexander; Gorgen, Andreas; Guttormsen, Magne; Larsen, Ann -Cecilie; Massey, Thomas N.; Siem, Sunniva
2013-11-08
Proton double-differential cross sections from 59Co(α,p)62Ni, 57Fe(α,p)60Co, 56Fe(7Li,p)62Ni, and 55Mn(6Li,p)60Co reactions have been measured with 21-MeV α and 15-MeV lithium beams. Cross sections have been compared against calculations with the empire reaction code. Different input level density models have been tested. It was found that the Gilbert and Cameron [A. Gilbert and A. G. W. Cameron, Can. J. Phys. 43, 1446 (1965)] level density model is best to reproduce experimental data. Level densities and spin cutoff parameters for 62Ni and 60Co above the excitation energy range of discrete levels (in continuum) have been obtained with a Monte Carlo technique. Furthermore,more » excitation energy dependencies were found to be inconsistent with the Fermi-gas model.« less
NASA Astrophysics Data System (ADS)
Voinov, A. V.; Grimes, S. M.; Brune, C. R.; Bürger, A.; Görgen, A.; Guttormsen, M.; Larsen, A. C.; Massey, T. N.; Siem, S.
2013-11-01
Proton double-differential cross sections from 59Co(α,p)62Ni, 57Fe(α,p)60Co, 56Fe(7Li,p)62Ni, and 55Mn(6Li,p)60Co reactions have been measured with 21-MeV α and 15-MeV lithium beams. Cross sections have been compared against calculations with the empire reaction code. Different input level density models have been tested. It was found that the Gilbert and Cameron [A. Gilbert and A. G. W. Cameron, Can. J. Phys.0008-420410.1139/p65-139 43, 1446 (1965)] level density model is best to reproduce experimental data. Level densities and spin cutoff parameters for 62Ni and 60Co above the excitation energy range of discrete levels (in continuum) have been obtained with a Monte Carlo technique. Excitation energy dependencies were found to be inconsistent with the Fermi-gas model.
Han, Oc Hee; Oldfield, E. )
1990-09-19
The authors have obtained {sup 27}Al solid-state nuclear magnetic resonance (NMR) spectra of several AlCl{sub 3}-THF complexes, using magic-angle sample-spinning (MASS) NMR at high field. The authors results suggest that the isotropic chemical shifts ({delta}{sub i}) occur in relatively well defined regions for 4-, 5-, and 6-coordinate species (AlCl{sub 4}{sup {minus}}, {approximately} 103 ppm; AlCl{sub 3}{center dot}THF, {approximately} 99 ppm; trans-AlCl{sub 3}{center dot}2THF, {approximately} 60 ppM; trans-(AlCl{sub 2}(THF){sub 4}){sup +}, {approximately} 14 ppM), as found previously with aluminum oxo compounds. They also find that theoretically calculated average nuclear quadrupole coupling constants (e{sup 2}qQ/h) (trans-(AlCl{sub 2}(THF){sub 4}){sup +}, {approximately} 6.3 MHz; trans-AlCl{sub 3}{center dot}2THF, {approximately} 4.6 MHz; AlCl{sub 3}{center dot}THF, {approximately} 3.0 MHz; AlCl{sub 4}{sup {minus}}, 0 MHz) are in good accord with experimentally determined nuclear quadrupole coupling constants, determined from computer simulations of the MASS NMR spectra (trans-(AlCl{sub 2}(THF){sub 4}){sup +}, 6.4 MHz; trans-AlCl{sub 3}{center dot}2THF, 4.9 MHz; AlCl{sub 3}{center dot}THF, 4.7 MHz; AlCl{sub 4}{sup {minus}}, 0.3 MHz). Both {sup 27}Al {delta}{sub i} and e{sup 2}qQ/h determinations appear to be useful as probes of structure in these systems, and thus offer a facile means of monitoring various solid-state reactions. 14 refs., 3 figs., 3 tabs.
Rude, Erica; Laborie, Marie-Pierre G
2008-05-01
The chemical interactions between maleic anhydride grafted polypropylene (MAPP) and wood were studied with solid-state carbon-13 cross-polarization magic-angle-spinning nuclear magnetic resonance ((13)C CPMAS NMR) spectroscopy. MAPP was synthesized with 100% (13)C enrichment at the C(1) and C(4) carbons to allow detection of the [1,4-(13)C(2)]MAPP functional groups and was melt blended with cellulose, lignin, and maple wood. In the cellulose/MAPP blend, changes in (13)C CPMAS NMR corrected signal intensities for the anhydride and dicarboxylic maleic acid functionalities suggested that esterification may have occurred predominantly from the more numerous diacid carbons. A single proton longitudinal relaxation in the rotating frame, (H)T(1rho), for the MAPP and the cellulose carbons in the blend suggested that they were spin coupled, i.e., homogeneous on a 10-200 Angstrom scale. Esterification was also suggested in the lignin/MAPP blend. Furthermore, the more significant changes in the intensities of the carbonyl signals and (H)T(1rho) values suggested that lignin may be more reactive to MAPP than cellulose. Finally, when maple was melt blended with MAPP, the same trends in the (13)C CP-MAS NMR spectra and (H)T(1rho) behavior were observed as when MAPP was blended with cellulose or lignin. This study therefore clarifies that during melt compounding of wood with MAPP, esterification occurs with wood polymers, preferentially with lignin. Understanding the interactions of MAPP with wood is of significance for the development of natural-fiber-reinforced thermoplastic composites. PMID:18498698
NASA Astrophysics Data System (ADS)
Matsuki, Yoh; Ueda, Keisuke; Idehara, Toshitaka; Ikeda, Ryosuke; Ogawa, Isamu; Nakamura, Shinji; Toda, Mitsuru; Anai, Takahiro; Fujiwara, Toshimichi
2012-12-01
We describe a 1H polarization enhancement via dynamic nuclear polarization (DNP) at very low sample temperature T ≈ 30 K under magic-angle spinning (MAS) conditions for sensitivity-enhanced solid-state NMR measurement. Experiments were conducted at a high external field strength of 14.1 T. For MAS DNP experiments at T ≪ 90 K, a new probe system using cold helium gas for both sample-cooling and -spinning was developed. The novel system can sustain a low sample temperature between 30 and 90 K for a period of time >10 h under MAS at νR ≈ 3 kHz with liquid He consumption of ≈6 L/h. As a microwave source, we employed a high-power, continuously frequency-tunable gyrotron. At T ≈ 34 K, 1H DNP enhancement factors of 47 and 23 were observed with and without MAS, respectively. On the basis of these observations, a discussion on the total NMR sensitivity that takes into account the effect of sample temperature and external field strength used in DNP experiments is presented. It was determined that the use of low sample temperature and high external field is generally rewarding for the total sensitivity, in spite of the slower polarization buildup at lower temperature and lower DNP efficiency at higher field. These findings highlight the potential of the current continuous-wave DNP technique also at very high field conditions suitable to analyze large and complex systems, such as biological macromolecules.
NASA Astrophysics Data System (ADS)
Cho, Herman
2016-09-01
Allowed transition energies and eigenstate expansions have been calculated and tabulated in numerical form as functions of the electric field gradient asymmetry parameter for the zero field Hamiltonian of quadrupolar nuclides with I = 3 / 2 , 5 / 2 , 7 / 2, and 9 / 2. These results are essential to interpret nuclear quadrupole resonance (NQR) spectra and extract accurate values of the electric field gradient tensors. Applications of NQR methods to studies of electronic structure in heavy element systems are proposed.
Cho, Herman
2016-02-28
Allowed transition energies and eigenstate expansions have been calculated and tabulated in numerical form as functions of the electric field gradient asymmetry parameter for the zero field Hamiltonian of quadrupolar nuclides with I = 3/2,5/2,7/2, and 9/2. These results are essential to interpret nuclear quadrupole resonance (NQR) spectra and extract accurate values of the electric field gradient tensors. Furthermore, applications of NQR methods to studies of electronic structure in heavy element systems are proposed.
Frozen spin targets in ribosomal structure research.
Stuhrmann, H B
1991-01-01
Polarized neutron scattering strongly depends on nuclear spin polarisation, particularly on proton spin polarisation. A single proton in a deuterated environment then is as efficient as 10 electrons in X-ray anomalous diffraction. Neutron scattering from the nuclear spin label is controlled by the polarisation of neutron spins and nuclear spins. Pure deuteron spin labels and proton spin labels are created by NMR saturation. We report on results obtained from the large subunit of E. coli ribosomes which have been obtained at the research reactor of GKSS using the polarized target facility developed by CERN. The nuclear spins were oriented with respect to an external field by dynamic nuclear polarisation. Proton spin polarisations of more than 80% were obtained in ribosomes at temperatures below 0.5 K. At T = 130 mK the relaxation time of the polarized target is one month (frozen spin target). Polarized small-angle neutron scattering of the in situ structure of rRNA and the total ribosomal protein (TP) has been determined from the frozen spin targets of the large ribosomal subunit, which has been deuterated in the TP and rRNA respectively. The results agree with those from neutron scattering in H2O/D2O mixtures obtained at room temperature. This is a necessary prerequisite for the planned determination of the in situ structure of individual ribosomal proteins and especially of that of ribosome bound mRNA and tRNAs. PMID:1720669
Voinov, Alexander V.; Grimes, Steven M.; Brune, Carl R.; Burger, Alexander; Gorgen, Andreas; Guttormsen, Magne; Larsen, Ann -Cecilie; Massey, Thomas N.; Siem, Sunniva
2013-11-08
Proton double-differential cross sections from ^{59}Co(α,p)^{62}Ni, ^{57}Fe(α,p)^{60}Co, ^{56}Fe(^{7}Li,p)^{62}Ni, and ^{55}Mn(^{6}Li,p)^{60}Co reactions have been measured with 21-MeV α and 15-MeV lithium beams. Cross sections have been compared against calculations with the empire reaction code. Different input level density models have been tested. It was found that the Gilbert and Cameron [A. Gilbert and A. G. W. Cameron, Can. J. Phys. 43, 1446 (1965)] level density model is best to reproduce experimental data. Level densities and spin cutoff parameters for ^{62}Ni and ^{60}Co above the excitation energy range of discrete levels (in continuum) have been obtained with a Monte Carlo technique. Furthermore, excitation energy dependencies were found to be inconsistent with the Fermi-gas model.
NASA Astrophysics Data System (ADS)
Dewberry, Christopher T.; Cooke, Stephen A.
2010-06-01
Recent progress in the fitting and analyses of simple methyl rotors to simultaneously account for internal rotation and nuclear hyperfine terms will be presented. The analyses have been attempted using Herb Pickett's IAMCALC program which acts as a ``front end" for the powerful SPFIT/SPCAT software. Progress has been made by simply appending hyperfine parameters to an IAMCALC-prepared SPFIT input file. This work has been prompted by our recent high resolution spectral measurements in the 1 - 21 GHz region on species such as methanol and methyl nitrite. Data will be presented together with comments on the validity of the fitting approach.
Benjamin Michael Meyer
2003-05-31
As time progresses, the world is using up more of the planet's natural resources. Without technological advances, the day will eventually arrive when these natural resources will no longer be sufficient to supply all of the energy needs. As a result, society is seeing a push for the development of alternative fuel sources such as wind power, solar power, fuel cells, and etc. These pursuits are even occurring in the state of Iowa with increasing social pressure to incorporate larger percentages of ethanol in gasoline. Consumers are increasingly demanding that energy sources be more powerful, more durable, and, ultimately, more cost efficient. Fast Ionic Conducting (FIC) glasses are a material that offers great potential for the development of new batteries and/or fuel cells to help inspire the energy density of battery power supplies. This dissertation probes the mechanisms by which ions conduct in these glasses. A variety of different experimental techniques give a better understanding of the interesting materials science taking place within these systems. This dissertation discusses Nuclear Magnetic Resonance (NMR) techniques performed on FIC glasses over the past few years. These NMR results have been complimented with other measurement techniques, primarily impedance spectroscopy, to develop models that describe the mechanisms by which ionic conduction takes place and the dependence of the ion dynamics on the local structure of the glass. The aim of these measurements was to probe the cause of a non-Arrhenius behavior of the conductivity which has been seen at high temperatures in the silver thio-borosilicate glasses. One aspect that will be addressed is if this behavior is unique to silver containing fast ion conducting glasses. more specifically, this study will determine if a non-Arrhenius correlation time, {tau}, can be observed in the Nuclear Spin Lattice Relaxation (NSLR) measurements. If so, then can this behavior be modeled with a new single distribution
Electron Spin Dynamics in Semiconductor Quantum Dots
Marie, X.; Belhadj, T.; Urbaszek, B.; Amand, T.; Krebs, O.; Lemaitre, A.; Voisin, P.
2011-07-15
An electron spin confined to a semiconductor quantum dot is not subject to the classical spin relaxation mechanisms known for free carriers but it strongly interacts with the nuclear spin system via the hyperfine interaction. We show in time resolved photoluminescence spectroscopy experiments on ensembles of self assembled InAs quantum dots in GaAs that this interaction leads to strong electron spin dephasing.
Spinning angle optical calibration apparatus
Beer, Stephen K.; Pratt, II, Harold R.
1991-01-01
An optical calibration apparatus is provided for calibrating and reproducing spinning angles in cross-polarization, nuclear magnetic resonance spectroscopy. An illuminated magnifying apparatus enables optical setting an accurate reproducing of spinning "magic angles" in cross-polarization, nuclear magnetic resonance spectroscopy experiments. A reference mark scribed on an edge of a spinning angle test sample holder is illuminated by a light source and viewed through a magnifying scope. When the "magic angle" of a sample material used as a standard is attained by varying the angular position of the sample holder, the coordinate position of the reference mark relative to a graduation or graduations on a reticle in the magnifying scope is noted. Thereafter, the spinning "magic angle" of a test material having similar nuclear properties to the standard is attained by returning the sample holder back to the originally noted coordinate position.
Properties of nuclei at very high spin
Stephens, F.S.
1980-09-01
Nuclear structure at very high spins involves an interplay between collective (often rotational) and noncollective (individual particle alignment) behavior. The new techniques for studying ..gamma..-ray energy correlations promise to give detailed information about both of these aspects of nuclear behavior up to the very highest spins that can be populated. 17 figures.
NASA Astrophysics Data System (ADS)
Colton, J. S.; Wienkes, L. R.
2009-03-01
We present a newly developed microwave resonant cavity for use in optically detected magnetic resonance (ODMR) experiments. The cylindrical quasi-TE011 mode cavity is designed to fit in a 1 in. magnet bore to allow the sample to be optically accessed and to have an adjustable resonant frequency between 8.5 and 12 GHz. The cavity uses cylinders of high dielectric material, so-called "dielectric resonators," in a double-stacked configuration to determine the resonant frequency. Wires in a pseudo-Helmholtz configuration are incorporated into the cavity to provide frequencies for simultaneous nuclear magnetic resonance (NMR). The system was tested by measuring cavity absorption as microwave frequencies were swept, by performing ODMR on a zinc-doped InP sample, and by performing optically detected NMR on a GaAs sample. The results confirm the suitability of the cavity for ODMR with simultaneous NMR.
Sen, Sabyasachi; Kaseman, Derrick C; Hung, Ivan; Gan, Zhehong
2015-04-30
The mechanism of (77)Se nuclear spin-lattice relaxation is investigated in binary Ge-Se glasses. The (77)Se nuclides in Se-Se-Se chain sites relax faster via dipolar coupling fluctuation compared to those in Ge-Se-Ge sites shared by GeSe4 tetrahedra that relax slower via the fluctuation of the chemical shift anisotropy. The relaxation rate for the Se-Se-Se sites decreases markedly with increasing magnetic field, whereas that for the Ge-Se-Ge sites displays no appreciable dependence on the magnetic field such that the extent of differential relaxation between the two Se environments becomes small at high fields on the order of 19.6 T. The corresponding dynamical correlation time is three orders of magnitude shorter (∼10(-9) s) for the Se-Se-Se sites, compared to that for the Ge-Se-Ge sites (∼10(-6) s). The large decoupling in the time scale between these Se environments provides direct experimental support to the commonly made assumption that the selenium chains are mechanically floppy, and the interconnected GeSe4 tetrahedra form the rigid elements in the selenide glass structure. PMID:25848959
Mazzei, Pierluigi; Vinale, Francesco; Woo, Sheridan Lois; Pascale, Alberto; Lorito, Matteo; Piccolo, Alessandro
2016-05-11
Trichoderma fungi release 6-pentyl-2H-pyran-2-one (1) and harzianic acid (2) secondary metabolites to improve plant growth and health protection. We isolated metabolites 1 and 2 from Trichoderma strains, whose different concentrations were used to treat seeds of Solanum lycopersicum. The metabolic profile in the resulting 15 day old tomato leaves was studied by high-resolution magic-angle-spinning nuclear magnetic resonance (HRMAS NMR) spectroscopy directly on the whole samples without any preliminary extraction. Principal component analysis (PCA) of HRMAS NMR showed significantly enhanced acetylcholine and γ-aminobutyric acid (GABA) content accompanied by variable amount of amino acids in samples treated with both Trichoderma secondary metabolites. Seed germination rates, seedling fresh weight, and the metabolome of tomato leaves were also dependent upon doses of metabolites 1 and 2 treatments. HRMAS NMR spectroscopy was proven to represent a rapid and reliable technique for evaluating specific changes in the metabolome of plant leaves and calibrating the best concentration of bioactive compounds required to stimulate plant growth. PMID:27088924
DeCoste, Jared B; Glover, T Grant; Mogilevsky, Gregory; Peterson, Gregory W; Wagner, George W
2011-08-01
A novel technique for determining the relative accessibility and reactivity of basic surface hydroxyl sites by reacting various zirconium(IV) hydroxide materials with 2,2,2-trifluoroethanol (TFE) and characterizing the resulting material using (19)F magic angle spinning (MAS) nuclear magnetic resonance (NMR) is presented here. Studied here are three zirconium hydroxide samples, two unperturbed commercial materials, and one commercial material that is crushed by a pellet press. Factors, such as the ratio of bridging/terminal hydroxyls, surface area, and pore size distribution, are examined and found to affect the ability of the zirconium(IV) hydroxide to react with TFE. X-ray diffraction, nitrogen isotherms, and (1)H MAS NMR were used to characterize the unperturbed materials, while thermogravitric analysis with gas chromatography and mass spectrometry along with the (19)F MAS NMR were used to characterize the materials that were reacted with TFE. Zirconium hydroxide materials with a high surface area and a low bridging/terminal hydroxyl ratio were found to react TFE in the greatest amounts. PMID:21699226
Hellmann, Robert; Bich, Eckard; Vogel, Eckhard; Dickinson, Alan S; Vesovic, Velisa
2009-03-28
Transport properties of pure methane have been calculated in the rigid-rotor approximation using the recently proposed intermolecular potential energy hypersurface [R. Hellmann et al., J. Chem. Phys. 128, 214303 (2008)] and the classical-trajectory method. Results are reported in the dilute-gas limit for the temperature range of 80-1500 K. The calculated thermal conductivity values are in very good agreement with the measured data and correlations. In the temperature range of 310-480 K the calculated values underestimate the best experimental data by 0.5%-1.0%. We suggest that the calculated values are more accurate, especially at low and high temperatures, than the currently available correlations based on the experimental data. Our results also agree well with measurements of thermal transpiration and of the thermomagnetic coefficients. We have shown that although the dominant contribution to the thermomagnetic coefficients comes from the Wjj polarization in the spherical approximation, the contribution of a second polarization, Wj, cannot be neglected nor can a full description of the Wjj polarization. The majority of the volume viscosity measurements around room temperature are consistent with the calculated values but this is not the case at high and low temperatures. However, for nuclear-spin relaxation the calculated values consistently exceed the measurements, which are mutually consistent within a few percent. PMID:19334832
NASA Astrophysics Data System (ADS)
Hoyt, D. W.; Turcu, R. V.; Sears, J. A.; Rosso, K. M.; Burton, S. D.; Kwak, J.; Felmy, A. R.; Hu, J.
2010-12-01
GCS is one of the most promising ways of mitigating atmospheric greenhouse gases. Mineral carbonation reactions are potentially important to the long-term sealing effectiveness of caprock but remain poorly predictable, particularly reactions occurring in low-water supercritical CO2(scCO2)-dominated environments where the chemistry has not been adequately explored. In situ probes that provide molecular-level information is desirable for investigating mechanisms and rates of GCS mineral carbonation reactions. MAS-NMR is a powerful tool for obtaining detailed molecular structure and dynamics information of a system regardless whether the system is in a solid, a liquid, a gaseous, or a supercritical state, or a mixture thereof. However, MAS NMR under scCO2 conditions has never been realized due to the tremendous technical difficulties of achieving and maintaining high pressure within a fast spinning MAS rotor. In this work, we report development of a unique high pressure MAS NMR capability, and its application to mineral carbonation chemistry in scCO2 under geologically relevant temperatures and pressures. Our high pressure MAS rotor has successfully maintained scCO2 conditions with minimal leakage over a period of 72 hours. Mineral carbonation reactions of a model magnesium silicate (forsterite) reacted with 96 bars scCO2 containing varying amounts of H2O (both below and above saturation of the scCO2) were investigated at 50○C. Figure 1 shows typical in situ 13C MAS NMR spectra demonstrating that the peaks corresponding to the reactants, intermediates, and the magnesium carbonation products are all observed in a single spectrum. For example, the scCO2 peak is located at 126.1 ppm. Reaction intermediates include the aqueous species HCO3-(160 ppm), partially hydrated/hydroxylated magnesium carbonates(166-168 ppm), and can easily be distinguished from final product magnesite(170 ppm). The new capability and this model mineral carbonation process will be overviewed in
Spectroscopy of composite solid-state spin environments for improved metrology with spin ensembles
NASA Astrophysics Data System (ADS)
Bar-Gill, Nir; Pham, Linh; Belthangady, Chinmay; Lesage, David; Cappellaro, Paola; Maze, Jeronimo; Lukin, Mikhail; Yacoby, Amir; Walsworth, Ronald
2012-02-01
For precision coherent measurements with ensembles of quantum spins the relevant Figure-of-Merit (FOM) is the product of spin density and coherence lifetime, which is generally limited by the dynamics of spin coupling to the environment. Significant effort has been invested in understanding the causes of decoherence in a diverse range of spin systems in order to increase the FOM and improve measurement sensitivity. Here, we apply a coherent spectroscopic technique to characterize the dynamics of a composite solid-state spin environment consisting of Nitrogen-Vacancy (NV) color centers in room temperature diamond coupled to baths of electronic spin (N) and nuclear spin (13C) impurities. For diamond samples with a wide range of NV densities and impurity spin concentrations we employ a dynamical decoupling technique to minimize coupling to the environment, and find similar values for the FOM, which is three orders of magnitude larger than previously achieved in any room-temperature solid-state spin system, and thus should enable greatly improved precision spin metrology. We also identify a suppression of electronic spin bath dynamics in the presence of a nuclear spin bath of sufficient nuclear spin concentration. This suppression could inform efforts to engineer samples with even larger FOM for solid-state spin ensemble metrology and collective quantum information processing.
Inhomogeneously broadened spin masers
NASA Astrophysics Data System (ADS)
Romalis, M. V.; Happer, W.
1999-08-01
Hyperpolarized 3He gas, where the nuclear spin polarization has been increased to several tens of percent by optical pumping, can couple such a large negative resistance into an external circuit that masing can ensue. The masing threshold can be suppressed by application of a magnetic field gradient. However, edge enhancement, that is, the less effective diffusional damping of the precessing magnetization at the container walls, can lower the masing threshold. The edge enhancement of the masing is greatly modified by magnetic self-interactions of the spins.
Spin Technologies in Silicon Carbide
NASA Astrophysics Data System (ADS)
Klimov, Paul
2015-03-01
Over the past several decades SiC has evolved from being a simple abrasive to a versatile material platform for high-power electronics, optoelectronics, and nanomechanical devices. These technologies have been driven by advanced growth, doping, and processing capabilities, and the ready availability of large-area, single-crystal SiC wafers. Recent advances have also established SiC as a promising host for a novel class of technologies based on the spin of intrinsic color centers. In particular, the divacancies and related defects have ground-state electronic-spin triplets with ms-long coherence times that can be optically addressed near telecom wavelengths and manipulated with magnetic, electric, and strain fields. Recently, divacancy addressability has been extended to the single defect level, laying foundation for single spin technologies in SiC. This rapidly developing field has prompted research into the SiC material host to understand how defect-bound electron spins interact with their surrounding nuclear spin bath. Although nuclear spins are typically a major source of decoherence in color-center spin systems, they are also an important resource since they interact with magnetic fields orders of magnitude more weakly than electronic spins. This fact has motivated their use for quantum memories and ultra-sensitive sensors. In this talk I will review advances in this rapidly developing field and discuss our efforts towards this latter goal. This work was supported by the AFOSR, DARPA, and the NSF.
Lorenz, Klaus; Preston, Caroline M
2002-01-01
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
2015-01-01
The N-terminus of the voltage-dependent anion channel (VDAC) has been proposed to contain the mechanistically important gating helices that modulate channel opening and closing. In this study, we utilize magic angle spinning nuclear magnetic resonance (MAS NMR) to determine the location and structure of the N-terminus for functional channels in lipid bilayers by measuring long-range 13C–13C distances between residues in the N-terminus and other domains of VDAC reconstituted into DMPC lipid bilayers. Our structural studies show that the distance between A14 Cβ in the N-terminal helix and S193 Cβ is ∼4–6 Å. Furthermore, VDAC phosphorylation by a mitochondrial kinase at residue S193 has been claimed to delay mitochondrial cell death by causing a conformational change that closes the channel, and a VDAC-Ser193Glu mutant has been reported to show properties very similar to those of phosphorylated VDAC in a cellular context. We expressed VDAC-S193E and reconstituted it into DMPC lipid bilayers. Two-dimensional 13C–13C correlation experiments showed chemical shift perturbations for residues located in the N-terminus, indicating possible structural perturbations to that region. However, electrophysiological data recorded on VDAC-S193E showed that channel characteristics were identical to those of wild type samples, indicating that phosphorylation of S193 does not directly affect channel gating. The combination of NMR and electrophysiological results allows us to discuss the validity of proposed gating models. PMID:25545271
Tian, Bing; Ma, Chao; Wang, Jian; Pan, Chun-Shu; Yang, Gen-Jin; Lu, Jian-Ping
2015-01-01
Pathological and metabolic alterations co-exist and co-develop in the progression of chronic pancreatitis (CP). The aim of the present study was to investigate the metabolic characteristics and disease severity of a rat model of CP in order to determine associations in the observed pathology and the metabolites of CP using high-resolution magic-angle spinning nuclear magnetic resonance spectroscopy (HR-MAS NMR). Wistar rats (n=36) were randomly assigned into 6 groups (n=6 per group). CP was established by administering dibutyltin dichloride solution into the tail vein. After 0, 7, 14, 21, 28 and 35 days, the pancreatic tissues were collected for pathological scoring or for HR-MAS NMR. Correlation analyses between the major pathological scores and the integral areas of the major metabolites were determined. The most representative metabolites, aspartate, betaine and fatty acids, were identified as possessing the greatest discriminatory significance. The Spearman's rank correlation coefficients between the pathology and metabolites of the pancreatic tissues were as follows: Betaine and fibrosis, 0.454 (P=0.044); betaine and inflammatory cell infiltration, 0.716 (P=0.0001); aspartate and fibrosis, -0.768 (P=0.0001); aspartate and inflammatory cell infiltration, -0.394 (P=0.085); fatty acid and fibrosis, -0.764 (P=0.0001); and fatty acid and inflammatory cell infiltration, -0.619 (P=0.004). The metabolite betaine positively correlated with fibrosis and inflammatory cell infiltration in CP. In addition, aspartate negatively correlated with fibrosis, but exhibited no significant correlation with inflammatory cell infiltration. Furthermore, the presence of fatty acids negatively correlated with fibrosis and inflammatory cell infiltration in CP. HR-MAS NMR may be used to analyze metabolic characteristics in a rat model of different degrees of chronic pancreatitis. PMID:25338744
Deaton, M. Brett; Duez, Matthew D.; Foucart, Francois; O'Connor, Evan; Ott, Christian D.; Scheel, Mark A.; Szilagyi, Bela; Kidder, Lawrence E.; Muhlberger, Curran D. E-mail: m.duez@wsu.edu
2013-10-10
Neutrino emission significantly affects the evolution of the accretion tori formed in black hole-neutron star mergers. It removes energy from the disk, alters its composition, and provides a potential power source for a gamma-ray burst. To study these effects, simulations in general relativity with a hot microphysical equation of state (EOS) and neutrino feedback are needed. We present the first such simulation, using a neutrino leakage scheme for cooling to capture the most essential effects and considering a moderate mass (1.4 M{sub ☉} neutron star, 5.6 M{sub ☉} black hole), high-spin (black hole J/M {sup 2} = 0.9) system with the K{sub 0} = 220 MeV Lattimer-Swesty EOS. We find that about 0.08 M{sub ☉} of nuclear matter is ejected from the system, while another 0.3 M{sub ☉} forms a hot, compact accretion disk. The primary effects of the escaping neutrinos are (1) to make the disk much denser and more compact, (2) to cause the average electron fraction Y{sub e} of the disk to rise to about 0.2 and then gradually decrease again, and (3) to gradually cool the disk. The disk is initially hot (T ∼ 6 MeV) and luminous in neutrinos (L{sub ν} ∼ 10{sup 54} erg s{sup –1}), but the neutrino luminosity decreases by an order of magnitude over 50 ms of post-merger evolution.
Eddy, Matthew T; Andreas, Loren; Teijido, Oscar; Su, Yongchao; Clark, Lindsay; Noskov, Sergei Y; Wagner, Gerhard; Rostovtseva, Tatiana K; Griffin, Robert G
2015-02-01
The N-terminus of the voltage-dependent anion channel (VDAC) has been proposed to contain the mechanistically important gating helices that modulate channel opening and closing. In this study, we utilize magic angle spinning nuclear magnetic resonance (MAS NMR) to determine the location and structure of the N-terminus for functional channels in lipid bilayers by measuring long-range (13)C-(13)C distances between residues in the N-terminus and other domains of VDAC reconstituted into DMPC lipid bilayers. Our structural studies show that the distance between A14 Cβ in the N-terminal helix and S193 Cβ is ∼4-6 Å. Furthermore, VDAC phosphorylation by a mitochondrial kinase at residue S193 has been claimed to delay mitochondrial cell death by causing a conformational change that closes the channel, and a VDAC-Ser193Glu mutant has been reported to show properties very similar to those of phosphorylated VDAC in a cellular context. We expressed VDAC-S193E and reconstituted it into DMPC lipid bilayers. Two-dimensional (13)C-(13)C correlation experiments showed chemical shift perturbations for residues located in the N-terminus, indicating possible structural perturbations to that region. However, electrophysiological data recorded on VDAC-S193E showed that channel characteristics were identical to those of wild type samples, indicating that phosphorylation of S193 does not directly affect channel gating. The combination of NMR and electrophysiological results allows us to discuss the validity of proposed gating models. PMID:25545271
NASA Astrophysics Data System (ADS)
Temme, F. P.
1992-12-01
Realisation of the invariance properties of the p ⩽ 2 number partitional inventory components of the 20-fold spin algebra associated with [A] 20 nuclear spin clusters under SU2 × L20 allows the mappings {[λ] → Γ} to be derived. In addition, recent general inner tensor product expressions under Ln, for n even (odd), also facilitates the evaluation of many higher [λ] ( L20; p = 3) correlative mappings onto SU3↓SO(3) × L↓20T A 5 subduced symmetry from SU2 duality, thus providing results that determine the nature of adapted NMR bases for both dodecahedrane and its d 20 analogue. The significance of this work lies in the pertinence of nuclear spin statistics to both selective MQ-NMR and to other spectroscopic aspects of cage clusters, e.g., [ 13C] n, n = 20, 60, fullerenes. Mappings onto Ln irreps sets of specific p ⩽ 3 number partitions arise in combinatorial treatment of {M iti} Rota fields, defining scalar invariants in the context of Cayley algebra. Inclusion of the Ln group in the specific Racah chain for NMR symmetry gives rise to significant further physical insight.
Quantum measurement of a mesoscopic spin ensemble
Giedke, G.; Taylor, J. M.; Lukin, M. D.; D'Alessandro, D.; Imamoglu, A.
2006-09-15
We describe a method for precise estimation of the polarization of a mesoscopic spin ensemble by using its coupling to a single two-level system. Our approach requires a minimal number of measurements on the two-level system for a given measurement precision. We consider the application of this method to the case of nuclear-spin ensemble defined by a single electron-charged quantum dot: we show that decreasing the electron spin dephasing due to nuclei and increasing the fidelity of nuclear-spin-based quantum memory could be within the reach of present day experiments.
Landau level spin diode in a GaAs two dimensional hole system
NASA Astrophysics Data System (ADS)
Klochan, O.; Hamilton, A. R.; das Gupta, K.; Sfigakis, F.; Beere, H. E.; Ritchie, D. A.
2015-03-01
We have fabricated and characterized a Landau level spin diode in a GaAs two-dimensional hole system. We used the spin diode to probe the hyperfine coupling between hole and nuclear spins and found no detectable net nuclear spin polarization, indicating that hole-nuclear spin flip-flop processes are suppressed by at least factor of 50 compared to GaAs electron systems.
Spin symmetry in the antinucleon spectrum.
Zhou, Shan-Gui; Meng, Jie; Ring, P
2003-12-31
We discuss spin and pseudospin symmetry in the spectrum of single nucleons and single antinucleons in a nucleus. As an example we use relativistic mean field theory to investigate single antinucleon spectra. We find a very well developed spin symmetry in single antineutron and single antiproton spectra. The dominant components of the wave functions of the spin doublet are almost identical. This spin symmetry in antiparticle spectra and the pseudospin symmetry in particle spectra have the same origin. However, it turns out that the spin symmetry in antinucleon spectra is much better developed than the pseudospin symmetry in normal nuclear single particle spectra. PMID:14754045
Optoelectronic spin memories of electrons in semiconductors
NASA Astrophysics Data System (ADS)
Miah, M. Idrish
2016-03-01
We optically generate electron spins in semiconductors and apply an external magnetic field perpendicularly to them. Time-resolved photoluminescence measurements, pumped with a circularly polarized light, are performed to study the spin polarization and spin memory times in the semiconducting host. The measured spin polarization is found to be an exponential decay with the time delay of the probe. It is also found that the spin memory times, extracted from the polarization decays, enhance with the strength of the external magnetic field. However, at higher fields, the memory times get saturated to sub- μs because of the coupling for interacting electrons with the local nuclear field.
Protecting a Solid-State Spin from Decoherence Using Dressed Spin States
NASA Astrophysics Data System (ADS)
Golter, D. Andrew; Baldwin, Thomas K.; Wang, Hailin
2014-12-01
We report experimental studies of dressing an electron spin in diamond with resonant and continuous microwave fields to protect the electron spin from magnetic fluctuations induced by the nuclear spin bath. We use optical coherent population trapping (CPT) to probe the energy level structure, optically induced spin transitions, and spin decoherence rates of the dressed spin states. Dressing an electron spin with resonant microwaves at a coupling rate near 1 MHz leads to a 50 times reduction in the linewidth of the spin transition underlying the CPT process, limited by transit-time broadening. Compared with dynamical decoupling, where effects of the bath are averaged out at specific times, the dressed spin state provides a continuous protection from decoherence.
NASA Astrophysics Data System (ADS)
Ishikawa, K.; Patton, B.; Olsen, B. A.; Jau, Y.-Y.; Happer, W.
2011-06-01
Optical pumping of alkali-metal atoms in vapor cells causes spin currents to flow to the cell walls where excess angular momentum accumulates in the wall nuclei. Experiments reported here indicate that the substantial enhancement of the nuclear-spin polarization of salts at the cell walls is primarily due to the nuclear-spin current, with a lesser contribution from the electron-spin current of the vapor.
Ishikawa, K.; Patton, B.; Olsen, B. A.; Jau, Y.-Y.; Happer, W.
2011-06-15
Optical pumping of alkali-metal atoms in vapor cells causes spin currents to flow to the cell walls where excess angular momentum accumulates in the wall nuclei. Experiments reported here indicate that the substantial enhancement of the nuclear-spin polarization of salts at the cell walls is primarily due to the nuclear-spin current, with a lesser contribution from the electron-spin current of the vapor.
Electrical control of single spin dynamics
NASA Astrophysics Data System (ADS)
Petta, Jason
2012-02-01
Over ten years ago, Daniel Loss and David DiVincenzo proposed using the spin of a single electron as a quantum bit. At the time of the proposal, it was not possible to trap a single electron in a device and measure its spin, let alone demonstrate control of quantum coherence. In this talk I will describe recent progress in the field, focusing on two new methods for single spin control that have been developed by my group at Princeton. The first method is based on quantum interference and implements spin-interferometry on a chip. The second method utilizes the strong spin-orbit coupling of InAs. By shifting the orbital position of the electronic wavefunction at gigahertz frequencies, we can control the orientation of a single electron spin and measure the full g-tensor, which exhibits a large anisotropy due to spin-orbit interactions. Both methods for single spin control are orders of magnitude faster than conventional electron spin resonance and allow investigations of single spin coherence in the presence of fluctuating nuclear and spin-orbit fields. I will also describe recent efforts to transfer these methods to silicon quantum dots, where the effects of fluctuating nuclear fields are much smaller.
Microfabricated Spin Polarized Atomic Magnetometers
NASA Astrophysics Data System (ADS)
Jimenez Martinez, Ricardo
Spin polarized atomic magnetometers involve the preparation of atomic spins and their detection for monitoring magnetic fields. Due to the fact that magnetic fields are ubiquitous in our world, spin polarized atomic magnetometers are used in a wide range of applications from the detection of magnetic fields generated by the human heart and brain to the detection of nuclear magnetic resonance. In this thesis we developed microfabricated spin polarized atomic magnetometers. These sensors are based on optical pumping and spin-exchange collisions between alkali atoms and noble gases contained in microfabricated millimeter-scale vapor cells. In the first part of the thesis, we improved different features of current microfabricated optical magnetometers. Specifically, we improved the bandwidth of these devices, without degrading their magnetic field sensitivity, by broadening their magnetic resonance through spin-exchange collisions between alkali atoms. We also implemented all-optical excitation techniques to avoid problems, such as the magnetic perturbation of the environment, induced by the radio-frequency fields used in some of these sensors. In the second part of the thesis we demonstrated a microfluidic chip for the optical production and detection of hyperpolarized Xe gas through spin-exchange collisions with optically pumped Rb atoms. These devices are critical for the widespread use of spin polarized atomic magnetometers in applications requiring simple, compact, low-cost, and portable instrumentation.
Spin polarization transfer by the radical pair mechanism
Zarea, Mehdi Ratner, Mark A.; Wasielewski, Michael R.
2015-08-07
In a three-site representation, we study a spin polarization transfer from radical pair spins to a nearby electron or nuclear spin. The quantum dynamics of the radical pair spins is governed by a constant exchange interaction between the radical pair spins which have different Zeeman frequencies. Radical pair spins can recombine to the singlet ground state or to lower energy triplet states. It is then shown that the coherent dynamics of the radical pair induces spin polarization on the nearby third spin in the presence of a magnetic field. The spin polarization transfer depends on the difference between Zeeman frequencies, the singlet and triplet recombination rates, and on the exchange and dipole-dipole interactions between the different spins. In particular, the sign of the polarization depends on the exchange coupling between radical pair spins and also on the difference between singlet and triplet recombination rate constants.
129Xe spin relaxation in frozen xenon
NASA Astrophysics Data System (ADS)
Fitzgerald, R. J.; Gatzke, M.; Fox, David C.; Cates, G. D.; Happer, W.
1999-04-01
We discuss the longitudinal spin relaxation of 129Xe nuclei in frozen xenon. Over a large range of temperatures and magnetic fields, the dominant spin-lattice relaxation mechanism is shown to be nuclear spin-flip Raman scattering of lattice phonons. Two closely related interactions couple the lattice phonons to the spins of 129Xe nuclei: (1) the nuclear spin-rotation interaction between nearest-neighbor atoms, and (2) the paramagnetic antishielding of the externally applied field at the site of 129Xe nuclei by the electrons of neighboring Xe atoms. We show that relaxation rates can be predicted by using measured chemical shifts of gaseous and condensed xenon. The predicted relaxation rates are in good agreement with measurements. We outline a simple way to estimate the spin-rotation coupling and paramagnetic antishielding in terms of the small perturbations of the outermost electron orbitals of one xenon atom due to a neighboring atom.
NASA Astrophysics Data System (ADS)
Lefort, Ronan; Bordat, Patrice; Cesaro, Attilio; Descamps, Marc
2007-01-01
This paper uses chemical shift surfaces to simulate experimental C13 cross polarization magic angle spinning spectra for amorphous solid state disaccharides, paying particular attention to the glycosidic linkage atoms in trehalose, sucrose, and lactose. The combination of molecular mechanics with density functional theory/gauge invariant atomic orbital ab initio methods provides reliable structural information on the conformational distribution in the glass. The results are interpreted in terms of an enhanced flexibility that trehalose possesses in the amorphous solid state, at least on the time scale of C13 nuclear magnetic resonance measurements. Implications of these findings for the fragility of trehalose glass and bioprotectant action are discussed.
NASA Astrophysics Data System (ADS)
Wang, Xiaorong
2016-03-01
In recent years, there has been exciting development in both experimental and theoretical studies of transverse spin asymmetries in polarized p+p and and DIS collisions. As a unique polarized proton-proton collider, Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) provides a unique opportunity to investigate the novel physics mechanisms that cause the large single spin asymmetry at the forward rapidity. Both PHENIX and STAR experiments have been studying the transverse spin asymmetries with a variety of final state particles in different kinematic regimes since 2006. Especially, recent theoretical development on scattering a polarized probe on the saturated nuclear may provide a unique way to probe the gluon and quark TMDs. RHIC successfully ran polarized p+Au collisions in 2015. We will expect to have new results from polarized d+Au to compare with existing results from p+p collision to extend our understanding of QCD. Further more, In 2015, PHENIX installed MPC-ex calorimeter at very forward region to measure direct photon AN and STAR installed Roman Pots to study the diffractive events in polarized p+p and p+Au collisions. The recent results on transverse polarized p+p and p+Au collisions from both PHENIX and STAR experiments will be presented in this talk. I will also briefly discuss the possibility for the transverse Spin program at future experiments sPHENIX and forward sPHENIX at RHIC. Supported by US Department of Energy and RIKEN Brookhaven Research Center.
Spin-dependent recombination and hyperfine interaction at deep defects
NASA Astrophysics Data System (ADS)
Ivchenko, E. L.; Bakaleinikov, L. A.; Kalevich, V. K.
2015-05-01
We present a theoretical study of optical electron-spin orientation and spin-dependent Shockley-Read-Hall recombination in the longitudinal magnetic field, taking into account the hyperfine coupling between the bound-electron spin and the nuclear spin of a deep paramagnetic center. The master rate equations for the coupled system are extended to describe the nuclear spin relaxation by using two distinct relaxation times, τn 1 and τn 2, respectively, for defect states with one and two (singlet) bound electrons. The general theory is developed for an arbitrary value of the nuclear spin I . The magnetic-field and excitation-power dependencies of the electron and nuclear spin polarizations are calculated for the value of I =1 /2 . In this particular case the nuclear effects can be taken into account by a simple replacement of the bound-electron spin relaxation time by an effective time dependent on free-electron and hole densities and free-electron spin polarization. The role of nuclear spin relaxation is visualized by isolines of the electron spin polarization on a two-dimensional graph with the axes log2(τn 1) and log2(τn 2) .
Spin noise spectroscopy in semiconductors: from a billion down to single spins
NASA Astrophysics Data System (ADS)
Hübner, J.; Dahbashi, R.; Berski, F.; Wiegand, J.; Kuhn, H.; Lonnemann, J.; Oestreich, M.
2014-08-01
Spin noise spectroscopy in semiconductors has matured during the past nine years into a versatile and well developed technique being capable to unveil the intrinsic and unaltered spin dynamics in a wide range of semiconductor systems. Originating from atom and quantum optics as a potential true quantum non-demolition measurement technique, SNS is capable of unearthing the intricate dynamics of free or localized electron and hole spins in semiconductors being eventually coupled to the nuclear spin bath as well. In this contribution, we review shortly the major steps which inspired the success of spin noise spectroscopy in semiconductors and present the most recent extensions into the low-invasive detection regime of the spin dynamics for the two extreme limits of very high and extremely low rates of spin decoherence, respectively. On the one hand, merging ultrafast laser spectroscopy with spin noise spectroscopy enables the detection of spin noise with picosecond resolution, i.e., with THz bandwidths yielding access to otherwise concealed microscopic electronic processes. On the other hand, we present very high sensitivity SNS being capable to measure the extremely long spin coherence of single holes enclosed in individual quantum dots venturing a step forward towards true optical quantum non-demolition experiments in semiconductors. In addition, higher-order spin noise statistics of, e.g., single charges can give information beyond the linear response regime governed by the fundamental fluctuationdissipation theorem and thereby possibly shed some light on the nested coupling between electronic and nuclear spins.
High spin isomer beam line at RIKEN
Kishida, T.; Ideguchi, E.; Wu, H.Y.
1996-12-31
Nuclear high spin states have been the subject of extensive experimental and theoretical studies. For the production of high spin states, fusion reactions are usually used. The orbital angular momentum brought in the reaction is changed into the nuclear spin of the compound nucleus. However, the maximum induced angular momentum is limited in this mechanism by the maximum impact parameter of the fusion reaction and by the competition with fission reactions. It is, therefore, difficult to populate very high spin states, and as a result, large {gamma}-detector arrays have been developed in order to detect subtle signals from such very high spin states. The use of high spin isomers in the fusion reactions can break this limitation because the high spin isomers have their intrinsic angular momentum, which can bring the additional angular momentum without increasing the excitation energy. There are two methods to use the high spin isomers for secondary reactions: the use of the high spin isomers as a target and that as a beam. A high spin isomer target has already been developed and used for several experiments. But this method has an inevitable shortcoming that only {open_quotes}long-lived{close_quotes} isomers can be used for a target: {sup 178}Hf{sup m2} (16{sup +}) with a half-life of 31 years in the present case. By developing a high spin isomer beam, the authors can utilize various short-lived isomers with a short half-life around 1 {mu}s. The high spin isomer beam line of RIKEN Accelerator Facility is a unique apparatus in the world which provides a high spin isomer as a secondary beam. The combination of fusion-evaporation reaction and inverse kinematics are used to produce high spin isomer beams; in particular, the adoption of `inverse kinematics` is essential to use short-lived isomers as a beam.
Andersen, John A.; Flanigan, John J.; Kindley, Robert J.
1978-01-01
The disclosure relates to an apparatus for spin ejecting a body having a flat plate base containing bosses. The apparatus has a base plate and a main ejection shaft extending perpendicularly from the base plate. A compressible cylindrical spring is disposed about the shaft. Bearings are located between the shaft and the spring. A housing containing a helical aperture releasably engages the base plate and surrounds the shaft bearings and the spring. A piston having an aperture follower disposed in the housing aperture is seated on the spring and is guided by the shaft and the aperture. The spring is compressed and when released causes the piston to spin eject the body.
NASA Astrophysics Data System (ADS)
Aucar, I. Agustín; Gómez, Sergio S.; Melo, Juan I.; Giribet, Claudia C.; Ruiz de Azúa, Martín C.
2013-04-01
In the present work, numerical results of the nuclear spin-rotation (SR) tensor in the series of compounds HX (X=H,F,Cl,Br,I) within relativistic 4-component expressions obtained by Aucar et al. [J. Chem. Phys. 136, 204119 (2012), 10.1063/1.4721627] are presented. The SR tensors of both the H and X nuclei are discussed. Calculations were carried out within the relativistic Linear Response formalism at the Random Phase Approximation with the DIRAC program. For the halogen nucleus X, correlation effects on the non-relativistic values are shown to be of similar magnitude and opposite sign to relativistic effects. For the light H nucleus, by means of the linear response within the elimination of the small component approach it is shown that the whole relativistic effect is given by the spin-orbit operator combined with the Fermi contact operator. Comparison of "best estimate" calculated values with experimental results yield differences smaller than 2%-3% in all cases. The validity of "Flygare's relation" linking the SR tensor and the NMR nuclear magnetic shielding tensor in the present series of compounds is analyzed.
Aucar, I Agustín; Gómez, Sergio S; Melo, Juan I; Giribet, Claudia C; Ruiz de Azúa, Martín C
2013-04-01
In the present work, numerical results of the nuclear spin-rotation (SR) tensor in the series of compounds HX (X = H,F,Cl,Br,I) within relativistic 4-component expressions obtained by Aucar et al. [J. Chem. Phys. 136, 204119 (2012)] are presented. The SR tensors of both the H and X nuclei are discussed. Calculations were carried out within the relativistic Linear Response formalism at the Random Phase Approximation with the DIRAC program. For the halogen nucleus X, correlation effects on the non-relativistic values are shown to be of similar magnitude and opposite sign to relativistic effects. For the light H nucleus, by means of the linear response within the elimination of the small component approach it is shown that the whole relativistic effect is given by the spin-orbit operator combined with the Fermi contact operator. Comparison of "best estimate" calculated values with experimental results yield differences smaller than 2%-3% in all cases. The validity of "Flygare's relation" linking the SR tensor and the NMR nuclear magnetic shielding tensor in the present series of compounds is analyzed. PMID:23574208
Spin-current probe for phase transition in an insulator.
Qiu, Zhiyong; Li, Jia; Hou, Dazhi; Arenholz, Elke; N'Diaye, Alpha T; Tan, Ali; Uchida, Ken-Ichi; Sato, Koji; Okamoto, Satoshi; Tserkovnyak, Yaroslav; Qiu, Z Q; Saitoh, Eiji
2016-01-01
Spin fluctuation and transition have always been one of the central topics of magnetism and condensed matter science. Experimentally, the spin fluctuation is found transcribed onto scattering intensity in the neutron-scattering process, which is represented by dynamical magnetic susceptibility and maximized at phase transitions. Importantly, a neutron carries spin without electric charge, and therefore it can bring spin into a sample without being disturbed by electric energy. However, large facilities such as a nuclear reactor are necessary. Here we show that spin pumping, frequently used in nanoscale spintronic devices, provides a desktop microprobe for spin transition; spin current is a flux of spin without an electric charge and its transport reflects spin excitation. We demonstrate detection of antiferromagnetic transition in ultra-thin CoO films via frequency-dependent spin-current transmission measurements, which provides a versatile probe for phase transition in an electric manner in minute devices. PMID:27573443
Spin-current probe for phase transition in an insulator
Qiu, Zhiyong; Li, Jia; Hou, Dazhi; Arenholz, Elke; N’Diaye, Alpha T.; Tan, Ali; Uchida, Ken-ichi; Sato, Koji; Okamoto, Satoshi; Tserkovnyak, Yaroslav; et al
2016-08-30
Spin fluctuation and transition have always been one of the central topics of magnetism and condensed matter science. Experimentally, the spin fluctuation is found transcribed onto scattering intensity in the neutron-scattering process, which is represented by dynamical magnetic susceptibility and maximized at phase transitions. Importantly, a neutron carries spin without electric charge, and therefore it can bring spin into a sample without being disturbed by electric energy. However, large facilities such as a nuclear reactor are necessary. Here we present that spin pumping, frequently used in nanoscale spintronic devices, provides a desktop microprobe for spin transition; spin current is amore » flux of spin without an electric charge and its transport reflects spin excitation. Additionally, we demonstrate detection of antiferromagnetic transition in ultra-thin CoO films via frequency-dependent spin-current transmission measurements, which provides a versatile probe for phase transition in an electric manner in minute devices.« less
Electric probe for spin transition and fluctuation
NASA Astrophysics Data System (ADS)
Qiu, Zhiyong; Li, Jia; Hou, Dazhi; Arenholz, Elke; N'diaye, Alpha T.; Tan, Ali; Uchida, Ken-Ichi; Sato, Koji; Tserkovnyak, Yaroslov; Qiu, Z. Q.; Saitoh, Eiji
Spin fluctuation and transition have always been one of central topics of magnetism and condense matter science. To probe them, neutron scatterings have been used as powerful tools. A part of neutrons injected into a sample is scattered by spin fluctuation inside the sample. This process transcribes the spin fluctuation onto scattering intensity, which is commonly represented by dynamical magnetic susceptibility of the sample and is maximized at magnetic phase transitions. Importantly, a neutron carries spin without electric charge, and it thus can bring spin into a sample without being disturbed by electric energy: an advantage of neutrons, although large facilities such as a nuclear reactor is necessary. Here we show that spin pumping, frequently used in nanoscale spintronic devices, provides a desktop micro probe for spin fluctuation and transition; not only a neutron beam, spin current is also a flux of spin without an electric charge and its transport reflects spin fluctuation in a sample. We demonstrate detection of anti-ferromagnetic transition in ultra-thin CoO films via frequency dependent spin-current transmission measurements.
Spin pumping and spin Seebeck effect
NASA Astrophysics Data System (ADS)
Saitoh, Eiji
2012-02-01
Utilization of a spin current, a flow of electrons' spins in a solid, is the key technology in spintronics that will allow the achievement of efficient magnetic memories and computing devices. In this technology, generation and detection of spin currents are necessary. Here, we review inverse spin-Hall effect and spin-current-generation phenomena recently discovered both in metals and insulators: inverse spin-Hall effect, spin pumping, and spin Seebeck effect. (1)Spin pumping and spin torque in a Mott insulator system We found that spin pumping and spin torque effects appear also at an interface between Pt and an insulator YIG.. This means that we can connect a spin current carried by conduction electrons and a spin-wave spin current flowing in insulators. We demonstrate electric signal transmission by using these effects and interconversion of the spin currents [1]. (2) Spin Seebeck effect We have observed, by using the inverse spin-Hall effect [2], spin voltage generation from a heat current in a NiFe, named the spin-Seebeck effect [3]. Surprisingly, spin-Seebeck effect was found to appear even in insulators [4], a situation completely different from conventional charge Seebeck effect. The result implies an important role of elementary excitation in solids beside charge in the spin Seebeck effect. In the talk, we review the recent progress of the research on this effect. This research is collaboration with K. Ando, K. Uchida, Y. Kajiwara, S. Maekawa, G. E. W. Bauer, S. Takahashi, and J. Ieda. [4pt] [1] Y. Kajiwara and E. Saitoh et al. Nature 464 (2010) 262. [0pt] [2] E. Saitoh et al., Appl. Phys. Lett. 88 (2006) 182509. [0pt] [3] K. Uchida and E. Saitoh et al., Nature 455 (2008)778. [0pt] [4] K. Uchida and E. Saitoh et al.,Nature materials 9 (2010) 894 - 897.
Electrical control of quantum dot spin qubits
NASA Astrophysics Data System (ADS)
Laird, Edward Alexander
This thesis presents experiments exploring the interactions of electron spins with electric fields in devices of up to four quantum dots. These experiments are particularly motivated by the prospect of using electric fields to control spin qubits. A novel hyperfine effect on a single spin in a quantum dot is presented in Chapter 2. Fluctuations of the nuclear polarization allow single-spin resonance to be driven by an oscillating electric field. Spin resonance spectroscopy revealed a nuclear polarization built up inside the quantum dot device by driving the resonance. The evolution of two coupled spins is controlled by the combination of hyperfine interaction, which tends to cause spin dephasing, and exchange, which tends to prevent it. In Chapter 3, dephasing is studied in a device with tunable exchange, probing the crossover between exchange-dominated and hyperfine-dominated regimes. In agreement with theoretical predictions, oscillations of the spin conversion probability and saturation of dephasing are observed. Chapter 4 deals with a three-dot device, suggested as a potential qubit controlled entirely by exchange. Preparation and readout of the qubit state are demonstrated, together with one out of two coherent exchange operations needed for arbitrary manipulations. A new readout technique allowing rapid device measurement is described. In Chapter 5, an attempt to make a two-qubit gate using a four-dot device is presented. Although spin qubit operation has not yet been possible, the electrostatic interaction between pairs of dots was measured to be sufficient in principle for coherent qubit coupling.
Electron spin coherence near room temperature in magnetic quantum dots.
Moro, Fabrizio; Turyanska, Lyudmila; Wilman, James; Fielding, Alistair J; Fay, Michael W; Granwehr, Josef; Patanè, Amalia
2015-01-01
We report on an example of confined magnetic ions with long spin coherence near room temperature. This was achieved by confining single Mn(2+) spins in colloidal semiconductor quantum dots (QDs) and by dispersing the QDs in a proton-spin free matrix. The controlled suppression of Mn-Mn interactions and minimization of Mn-nuclear spin dipolar interactions result in unprecedentedly long phase memory (TM ~ 8 μs) and spin-lattice relaxation (T1 ~ 10 ms) time constants for Mn(2+) ions at T = 4.5 K, and in electron spin coherence observable near room temperature (TM ~ 1 μs). PMID:26040432
Spin relaxation in disordered media
NASA Astrophysics Data System (ADS)
Dzheparov, F. S.
2011-10-01
A review is given on theoretical grounds and typical experimental appearances of spin dynamics and relaxation in solids containing randomly distributed nuclear and/or electronic spins. Brief content is as follows. Disordered and magnetically diluted systems. General outlines of the spin transport theory. Random walks in disordered systems (RWDS). Observable values in phase spin relaxation, free induction decay (FID). Interrelation of longitudinal and transversal relaxation related to dynamics of occupancies and phases. Occupation number representation for equations of motion. Continuum media approximation and inapplicability of moment expansions. Long-range transitions vs percolation theory. Concentration expansion as a general constructive basis for analytical methods. Scaling properties of propagators. Singular point. Dynamical and kinematical memory in RWDS. Ways of regrouping of concentration expansions. CTRW and semi-phenomenology. Coherent medium approximation for nuclear relaxation via paramagnetic impurities. Combining of memory functions and cumulant expansions for calculation of FID. Path integral representations for RWDS. Numerical simulations of RWDS. Spin dynamics in magnetically diluted systems with low Zeeman and medium low dipole temperatures. Cluster expansions, regularization of dipole interactions and spectral dynamics.
Creutz, Michael
2014-03-15
Quantum mechanics and relativity in the continuum imply the well known spin–statistics connection. However for particles hopping on a lattice, there is no such constraint. If a lattice model yields a relativistic field theory in a continuum limit, this constraint must “emerge” for physical excitations. We discuss a few models where a spin-less fermion hopping on a lattice gives excitations which satisfy the continuum Dirac equation. This includes such well known systems such as graphene and staggered fermions. -- Highlights: •The spin–statistics theorem is not required for particles on a lattice. •Spin emerges dynamically when spinless fermions have a relativistic continuum limit. •Graphene and staggered fermions are examples of this phenomenon. •The phenomenon is intimately tied to chiral symmetry and fermion doubling. •Anomaly cancellation is a crucial feature of any valid lattice fermion action.
Exclusive processes in QCD and spin-spin correlations
de Teramond, G.F.
1988-09-01
The unexpected spin behavior observed in hard proton-proton collisions is described in terms of new degrees of freedom associated with the onset of strange and charmed thresholds. The deviation from dimensional scaling laws, the anomalous broadening of angular distributions, and the unusual energy dependence of pp quasielastic scattering in nuclear targets are also consistent with the onset of highly inelastic contributions to elastic pp amplitudes interfering with a perturbative QCD background. The model predicts significant charm production above 12 GeV/c and a relaxation of the spin correlation parameters to their scaling values at higher energies. 13 refs., 3 figs.
Measurement of spin coherence using Raman scattering
NASA Astrophysics Data System (ADS)
Sun, Z.; Delteil, A.; Faelt, S.; Imamoǧlu, A.
2016-06-01
Ramsey interferometry provides a natural way to determine the coherence time of most qubit systems. Recent experiments on quantum dots, however, demonstrated that dynamical nuclear spin polarization can strongly influence the measurement process, making it difficult to extract the T2* coherence time using standard optical Ramsey pulses. Here, we demonstrate an alternative method for spin coherence measurement that is based on first-order coherence of photons generated in spin-flip Raman scattering. We show that if a quantum emitter is driven by a weak monochromatic laser, Raman coherence is determined exclusively by spin coherence, allowing for a direct determination of spin T2* time. When combined with coherence measurements on Rayleigh scattered photons, our technique enables us to identify coherent and incoherent contributions to resonance fluorescence, and to minimize the latter. We verify the validity of our technique by comparing our results to those determined from Ramsey interferometry for electron and heavy-hole spins.
The Art of Neutron Spin Flipping
NASA Astrophysics Data System (ADS)
Lieffers, Justin; Holley, Adam; Snow, W. M.
2014-09-01
Low energy precision measurements complement high energy collider results in the search for physics beyond the Standard Model. Neutron spin rotation is a sensitive technique to search for possible exotic velocity and spin-dependent interactions involving the neutron from the exchange of light (~ meV) spin 1 bosons. We plan to conduct such searches using beams of cold neutrons at the Los Alamos Neutron Science Center (LANSCE) and the National Institute of Standards and Technology (NIST). To change the spin state of the neutrons in the apparatus we have developed an Adiabatic Fast Passage (AFP) neutron spin flipper. I will present the mechanical design, static and RF magnetic field modeling and measurements, and spin flip efficiency optimization of the constructed device. I would like to acknowledge the NSF REU program (NSF-REU grant PHY-1156540) and the Indiana University nuclear physics group (NSF grant PHY-1306942) for this opportunity.