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Sample records for electron nuclear double

  1. Quantum computing using electron-nuclear double resonances

    NASA Astrophysics Data System (ADS)

    Bowden, Charles M.; Dowling, Jonathan P.; Hotaling, Steven P.

    1997-07-01

    We consider the use of Electron-Nuclear Double Resonance (ENDOR) techniques in quantum computing. ENDOR resolution as a possible limiting factor is discussed. It is found that ENDOR and double-ENDOR techniques have sufficient resolution for quantum computing applications.

  2. Electron spin coherence and electron nuclear double resonance of Bi donors in natural Si.

    PubMed

    George, Richard E; Witzel, Wayne; Riemann, H; Abrosimov, N V; Nötzel, N; Thewalt, Mike L W; Morton, John J L

    2010-08-06

    Donors in silicon hold considerable promise for emerging quantum technologies, due to their uniquely long electron spin coherence times. Bismuth donors in silicon differ from more widely studied group V donors, such as phosphorous, in several significant respects: They have the strongest binding energy (70.98 meV), a large nuclear spin (I=9/2), and a strong hyperfine coupling constant (A=1475.4  MHz). These larger energy scales allow us to perform a detailed test of theoretical models describing the spectral diffusion mechanism that is known to govern the electron spin decoherence of P donors in natural silicon. We report the electron-nuclear double resonance spectra of the Bi donor, across the range 200 MHz to 1.4 GHz, and confirm that coherence transfer is possible between electron and nuclear spin degrees of freedom at these higher frequencies.

  3. A multifrequency high-field pulsed electron paramagnetic resonance/electron-nuclear double resonance spectrometer

    NASA Astrophysics Data System (ADS)

    Morley, Gavin W.; Brunel, Louis-Claude; van Tol, Johan

    2008-06-01

    We describe a pulsed electron paramagnetic resonance spectrometer operating at several frequencies in the range of 110-336GHz. The microwave source at all frequencies consists of a multiplier chain starting from a solid state synthesizer in the 12-15GHz range. A fast p-i-n-switch at the base frequency creates the pulses. At all frequencies a Fabry-Pérot resonator is employed and the π /2 pulse length ranges from ˜100ns at 110GHzto˜600ns at 334GHz. Measurements of a single crystal containing dilute Mn2+ impurities at 12T illustrate the effects of large electron spin polarizations. The capabilities also allow for pulsed electron-nuclear double resonance (ENDOR) experiments as demonstrated by Mims ENDOR of K39 nuclei in Cr :K3NbO8.

  4. A triple resonance hyperfine sublevel correlation experiment for assignment of electron-nuclear double resonance lines

    NASA Astrophysics Data System (ADS)

    Potapov, Alexey; Epel, Boris; Goldfarb, Daniella

    2008-02-01

    A new, triple resonance, pulse electron paramagnetic resonance (EPR) sequence is described. It provides spin links between forbidden electron spin transitions (ΔMS=±1, ΔMI≠0) and allowed nuclear spin transitions (ΔMI=±1), thus, facilitating the assignment of nuclear frequencies to their respective electron spin manifolds and paramagnetic centers. It also yields the relative signs of the hyperfine couplings of the different nuclei. The technique is based on the combination of electron-nuclear double resonance (ENDOR) and electron-electron double resonance (ELDOR)-detected NMR experiments in a way similar to the TRIPLE experiment. The feasibility and the information content of the method are demonstrated first on a single crystal of Cu-doped L-histidine and then on a frozen solution of a Cu-histidine complex.

  5. Transition operators entering neutrinoless double electron capture to excited nuclear states

    NASA Astrophysics Data System (ADS)

    Vergados, J. D.

    2011-10-01

    We construct the effective transition operators relevant for neutrinoless double electron capture leading to final nuclear states different than 0+. From the structure of these operators we see that if such a process is observed experimentally, it will be very helpful in singling out the very important light neutrino mass contribution from the other lepton violating mechanisms.

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

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

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

  7. Electron-nuclear correlation in above-threshold double ionization of molecules

    NASA Astrophysics Data System (ADS)

    Lu, Peifen; Zhang, Wenbin; Gong, Xiaochun; Song, Qiying; Lin, Kang; Ji, Qinying; Ma, Junyang; He, Feng; Zeng, Heping; Wu, Jian

    2017-03-01

    We report on the experimental observation of photon energy sharing among two electrons and two ions ejected from a doubly ionized molecule exposed to an intense ultraviolet femtosecond laser pulse. Although two electrons are successively released one after the other, bridged by the nuclear motion via their interactions, photon energy sharing among four particles is observed as multiple energy conservation lines in their joint energy spectrum. For sequential double ionization of H2, the electron-nuclear joint energy spectrum allows us to identify three pathways towards the charge-resonance enhanced ionization of the stretching H2+ in strong laser fields. By counting the photon number absorbed by the molecule, we trace the accessibility, enhancement, and suppression of various pathways. The correlated electron-nuclear motion provides profound insights of the complicated strong-field dynamics of molecules.

  8. Distance measurements between paramagnetic centers and a planar object by matrix Mims electron nuclear double resonance

    NASA Astrophysics Data System (ADS)

    Zänker, Paul-Philipp; Jeschke, Gunnar; Goldfarb, Daniella

    2005-01-01

    Frequency-domain electron nuclear double resonance (ENDOR), two time-domain electron nuclear double resonance techniques, and electron spin echo envelope modulation spectroscopy are compared with respect to their merit in measurements of small hyperfine couplings to nuclei with intermediate gyromagnetic ratio such as 31P. The frequency-domain Mims ENDOR experiment is found to provide the most faithful line shapes. In the limit of long electron-nuclear distances of more than 0.5 nm, sensitivity of this experiment is optimized by matching the first interpulse delay to the transverse relaxation time of the electron spins. In the same limit, Mims ENDOR efficiency scales inversely with the sixth power of distance. Hyperfine splittings as small as 33 kHz can be detected, corresponding to an electron-31P distance of 1 nm. In systems, where a certain kind of nuclei is distributed in a plane, measurements of intermolecular hyperfine couplings can be analyzed in terms of a distance of closest approach of a paramagnetic center to that plane. By applying this technique to spin-labeled lipids in a fully hydrated lipid bilayer it is found that for a fraction of lipids, chain tilt angles can be 25° larger than the mean tilt angle of the lipid chains. This model of all-trans hydrocarbon chains with a broad distribution of tilt angles is also consistent with orientation selection effects in high-field ENDOR spectra.

  9. Distance measurements between paramagnetic centers and a planar object by matrix Mims electron nuclear double resonance.

    PubMed

    Zänker, Paul-Philipp; Jeschke, Gunnar; Goldfarb, Daniella

    2005-01-08

    Frequency-domain electron nuclear double resonance (ENDOR), two time-domain electron nuclear double resonance techniques, and electron spin echo envelope modulation spectroscopy are compared with respect to their merit in measurements of small hyperfine couplings to nuclei with intermediate gyromagnetic ratio such as 31P. The frequency-domain Mims ENDOR experiment is found to provide the most faithful line shapes. In the limit of long electron-nuclear distances of more than 0.5 nm, sensitivity of this experiment is optimized by matching the first interpulse delay to the transverse relaxation time of the electron spins. In the same limit, Mims ENDOR efficiency scales inversely with the sixth power of distance. Hyperfine splittings as small as 33 kHz can be detected, corresponding to an electron-31P distance of 1 nm. In systems, where a certain kind of nuclei is distributed in a plane, measurements of intermolecular hyperfine couplings can be analyzed in terms of a distance of closest approach of a paramagnetic center to that plane. By applying this technique to spin-labeled lipids in a fully hydrated lipid bilayer it is found that for a fraction of lipids, chain tilt angles can be 25 degrees larger than the mean tilt angle of the lipid chains. This model of all-trans hydrocarbon chains with a broad distribution of tilt angles is also consistent with orientation selection effects in high-field ENDOR spectra. 2005 American Institute of Physics.

  10. High frequency electron nuclear double resonance at 239 GHz using a far-infrared laser source

    SciTech Connect

    Paschedag, L.; van Tol, J.; Wyder, P.

    1995-10-01

    We report on the application of {sup 14}N electron nuclear double resonance (ENDOR) at 8.5 T and 239 GHz ({lambda}=1.2 mm) in a {gamma}-irradiated betaine arsenate single crystal. A laser was used as a far-infrared radiation source in a transmission-type electron paramagnetic resonance (EPR) setup without a cavity. The four expected nitrogen ENDOR lines were observed, but due to insufficient saturation of the EPR transitions the signal/noise ratio was not larger than 10 and the signals vanished at temperatures above 20 K. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  11. Concerted Electronic and Nuclear Fluxes During Coherent Tunnelling in Asymmetric Double-Well Potentials.

    PubMed

    Bredtmann, Timm; Manz, Jörn; Zhao, Jian-Ming

    2016-05-19

    The quantum theory of concerted electronic and nuclear fluxes (CENFs) during coherent periodic tunnelling from reactants (R) to products (P) and back to R in molecules with asymmetric double-well potentials is developed. The results are deduced from the solution of the time-dependent Schrödinger equation as a coherent superposition of two eigenstates; here, these are the two states of the lowest tunnelling doublet. This allows the periodic time evolutions of the resulting electronic and nuclear probability densities (EPDs and NPDs) as well as the CENFs to be expressed in terms of simple sinusodial functions. These analytical results reveal various phenomena during coherent tunnelling in asymmetric double-well potentials, e.g., all EPDs and NPDs as well as all CENFs are synchronous. Distortion of the symmetric reference to a system with an asymmetric double-well potential breaks the spatial symmetry of the EPDs and NPDs, but, surprisingly, the symmetry of the CENFs is conserved. Exemplary application to the Cope rearrangement of semibullvalene shows that tunnelling of the ideal symmetric system can be suppressed by asymmetries induced by rather small external electric fields. The amplitude for the half tunnelling, half nontunnelling border is as low as 0.218 × 10(-8) V/cm. At the same time, the delocalized eigenstates of the symmetric reference, which can be regarded as Schrödinger's cat-type states representing R and P with equal probabilities, get localized at one or the other minima of the asymmetric double-well potential, representing either R or P.

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

    SciTech Connect

    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.

  13. Characterization of borate glasses by W-band pulse electron-nuclear double resonance spectroscopy

    SciTech Connect

    Kordas, George; Goldfarb, Daniella

    2008-10-21

    (100-x) mol % B{sub 2}O{sub 3} x mol %Me{sub 2}O (Me=Li,Na,K) glasses, exposed to {gamma}-{sup 60}Co irradiation to produce paramagnetic states, were characterized by W-band (95 GHz) pulse electron-nuclear double resonance (ENDOR) spectroscopy in order to characterize local structures occurring in the range of compositions between x=16 and x=25 at which the 'boron oxide' anomaly occurs. The high resolution of nuclear frequencies allowed resolving the {sup 7}Li and {sup 11}B ENDOR lines. In the samples with x=16 and x=20 glasses, {sup 11}B hyperfine couplings of 16, 24, and 36 MHz were observed and attributed to the tetraborate, triborate, and boron oxygen hole center (BOHC) structures, respectively. The x=25 samples showed hyperfine couplings of 15 MHz for the tetraborate and 36 MHz for BOHC. Density functional theory (DFT) calculations predicted for these structures negative hyperfine couplings, which were confirmed by W-band ENDOR. This suggests that a spin polarization mechanism accounts for the negative hyperfine structure splitting.

  14. Schonland ambiguity in the electron nuclear double resonance analysis of hyperfine interactions: principles and practice.

    PubMed

    Vrielinck, H; De Cooman, H; Tarpan, M A; Sagstuen, E; Waroquier, M; Callens, F

    2008-12-01

    For the analysis of the angular dependence of electron paramagnetic resonance (EPR) spectra of low-symmetry centres with S=1/2 in three independent planes, it is well-established-but often overlooked-that an ambiguity may arise in the best-fit g<--> tensor result. We investigate here whether a corresponding ambiguity also arises when determining the hyperfine coupling (HFC) A<--> tensor for nuclei with I=1/2 from angular dependent electron nuclear double resonance (ENDOR) measurements. It is shown via a perturbation treatment that for each set of M(S) ENDOR branches two best-fit A<--> tensors can be derived, but in general only one unique solution simultaneously fits both. The ambiguity thus only arises when experimental data of only one M(S) multiplet are used in analysis or in certain limiting cases. It is important to realise that the ambiguity occurs in the ENDOR frequencies and therefore the other best-fit result for an ENDOR determined A<--> tensor depends on various details of the ENDOR experiment: the M(S) state of the fitted transitions, the microwave frequency (or static magnetic field) in the ENDOR measurements and the rotation planes in which data have been collected. The results are of particular importance in the identification of radicals based on comparison of theoretical predictions of HFCs with published literature data. A procedure for obtaining the other best-fit result for an ENDOR determined A<--> tensor is outlined.

  15. Electron spin-flip correlations due to nuclear dynamics in driven GaAs double dots

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

    We present experimental data and associated theory for correlations in a series of experiments involving repeated Landau-Zener sweeps through the crossing point of a singlet state and a spin-aligned triplet state in a GaAs double quantum dot containing two conduction electrons, which are loaded in the singlet state before each sweep, and the final spin is recorded after each sweep. The experiments reported here measure correlations on time scales from 4 μ s to 2 ms. When the magnetic field is aligned in a direction such that spin-orbit coupling cannot cause spin flips, the correlation spectrum has prominent peaks centered at zero frequency and at the differences of the Larmor frequencies of the nuclei, on top of a frequency-independent background. When the spin-orbit field is relevant, there are additional peaks, centered at the frequencies of the individual species. A theoretical model which neglects the effects of high-frequency charge noise correctly predicts the positions of the observed peaks, and gives a reasonably accurate prediction of the size of the frequency-independent background, but gives peak areas that are larger than the observed areas by a factor of 2 or more. The observed peak widths are roughly consistent with predictions based on nuclear dephasing times of the order of 60 μ s . However, there is extra weight at the lowest observed frequencies, which suggests the existence of residual correlations on the scale of 2 ms. We speculate on the source of these discrepancies.

  16. Electron Paramagnetic Resonance and Electron-Nuclear Double Resonance Characterization of Point Defects in Titanium dioxide Crystals

    NASA Astrophysics Data System (ADS)

    Brant, Adam

    Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to characterize several point defects in titanium dioxide (TiO2) single crystals in the rutile phase. A defect reported in 1961 by P. F. Chester called the “A Center” is assigned to a neutral hydrogen donor. Many researchers believe that the model for this S = 1/2 defect is an interstitial titanium ion (Ti3+) and that Ti3+ interstitials are the most dominant shallow donor in TiO 2. I show that the model for the A center is a neutral hydrogen donor and suggest that the Ti3+ interstitial model is not the most prevalent shallow donor defect in TiO2. Substitutional Cu2+ defects that are unintentionally introduced to TiO2 (rutile) during growth are characterized and assigned to a Cu2+ ion with an adjacent oxygen vacancy. Exact matrix diagonalization is used here to compute accurate values for the nuclear quadrupole parameter. The reduced intensity of the Cu2+ EPR signal when the sample is illuminated with 442 nm laser light as well as the appearance of photoinduced EPR signals due to singly and doubly ionized oxygen vacancies provide evidence that the Cu2+ defect has an adjacent oxygen vacancy. Interstitial lithium ions (Li+) adjacent to Ti 3+ ions and substitutional Fe3+ defects (Fe 3+ - Li+) are also characterized. These defects were introduced to the rutile crystal by heating at 450 °C in LiOH powder for times on the order of several hours. Principal values and principal axis directions of the g matrix are calculated for the interstitial Li+ ion adjacent to a Ti3+ ion and photoinduced effects of the Fe 3+ - Li+ defect are examined.

  17. Advanced Paramagnetic Resonance Spectroscopies of Iron-Sulfur Proteins: Electron Nuclear Double Resonance (ENDOR) and Electron Spin Echo Envelope Modulation (ESEEM)

    PubMed Central

    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

  18. Electron nuclear double resonance evidence supporting a monomeric nature for P700+ in spinach chloroplasts

    PubMed Central

    O'Malley, Pádraig J.; Babcock, Gerald T.

    1984-01-01

    Proton electron nuclear double resonance (ENDOR) spectra of P700+ in spinach chloroplasts and in photosystem I particles have been obtained and compared with the corresponding ENDOR spectrum of monomeric chlorophyl a+ (Chla+) cation radical. The hyperfine couplings for P700+ can be interpreted in terms of those expected for a monomer Chla+ radical. The reduction in α-carbon spin densities observed for the in vivo species when compared to the in vitro radical is attributed to differences in the composition of the ground-state orbital for the two systems. For P700+, a mixture of 75% D0/25% D1, in which D0 and D1 represent the ground-and first excited-state orbitals calculated by Petke et al. for Chla+ [Petke, J. D., Maggiora, G. M., Shipman, L. L. & Christoffersen, R. E. (1980) Photochem. Photobiol. 31, 243-257], gives good agreement between calculated and experimental spin-density reduction factors. Interaction of the pigment ion with its protein environment such as through ligation of the central Mg atom, hydrogen bonding to the 9-keto-carbonyl group, and electrostatic interactions with charged amino acid residues are proposed as factors responsible for the lowering in energy of the D1 level in vivo. Combined with similar previous proposals for P680+ of photosystem II, the data suggest that both primary donor cation radicals of green plant photosynthesis can be viewed as monomeric Chla+ species in which the D1 orbital makes a significant contribution to the spin-density distribution. PMID:16593417

  19. Electron nuclear double resonance evidence supporting a monomeric nature for P700 in spinach chloroplasts.

    PubMed

    O'malley, P J; Babcock, G T

    1984-02-01

    Proton electron nuclear double resonance (ENDOR) spectra of P700(+) in spinach chloroplasts and in photosystem I particles have been obtained and compared with the corresponding ENDOR spectrum of monomeric chlorophyl a(+) (Chla(+)) cation radical. The hyperfine couplings for P700(+) can be interpreted in terms of those expected for a monomer Chla(+) radical. The reduction in alpha-carbon spin densities observed for the in vivo species when compared to the in vitro radical is attributed to differences in the composition of the ground-state orbital for the two systems. For P700(+), a mixture of 75% D(0)/25% D(1), in which D(0) and D(1) represent the ground-and first excited-state orbitals calculated by Petke et al. for Chla(+) [Petke, J. D., Maggiora, G. M., Shipman, L. L. & Christoffersen, R. E. (1980) Photochem. Photobiol. 31, 243-257], gives good agreement between calculated and experimental spin-density reduction factors. Interaction of the pigment ion with its protein environment such as through ligation of the central Mg atom, hydrogen bonding to the 9-keto-carbonyl group, and electrostatic interactions with charged amino acid residues are proposed as factors responsible for the lowering in energy of the D(1) level in vivo. Combined with similar previous proposals for P680(+) of photosystem II, the data suggest that both primary donor cation radicals of green plant photosynthesis can be viewed as monomeric Chla(+) species in which the D(1) orbital makes a significant contribution to the spin-density distribution.

  20. Observation of strongly forbidden solid effect dynamic nuclear polarization transitions via electron-electron double resonance detected NMR

    NASA Astrophysics Data System (ADS)

    Smith, Albert A.; Corzilius, Björn; Haze, Olesya; Swager, Timothy M.; Griffin, Robert G.

    2013-12-01

    We present electron paramagnetic resonance experiments for which solid effect dynamic nuclear polarization transitions were observed indirectly via polarization loss on the electron. This use of indirect observation allows characterization of the dynamic nuclear polarization (DNP) process close to the electron. Frequency profiles of the electron-detected solid effect obtained using trityl radical showed intense saturation of the electron at the usual solid effect condition, which involves a single electron and nucleus. However, higher order solid effect transitions involving two, three, or four nuclei were also observed with surprising intensity, although these transitions did not lead to bulk nuclear polarization—suggesting that higher order transitions are important primarily in the transfer of polarization to nuclei nearby the electron. Similar results were obtained for the SA-BDPA radical where strong electron-nuclear couplings produced splittings in the spectrum of the indirectly observed solid effect conditions. Observation of high order solid effect transitions supports recent studies of the solid effect, and suggests that a multi-spin solid effect mechanism may play a major role in polarization transfer via DNP.

  1. Observation of strongly forbidden solid effect dynamic nuclear polarization transitions via electron-electron double resonance detected NMR

    SciTech Connect

    Smith, Albert A.; Corzilius, Björn; Haze, Olesya; Swager, Timothy M.; Griffin, Robert G.

    2013-12-07

    We present electron paramagnetic resonance experiments for which solid effect dynamic nuclear polarization transitions were observed indirectly via polarization loss on the electron. This use of indirect observation allows characterization of the dynamic nuclear polarization (DNP) process close to the electron. Frequency profiles of the electron-detected solid effect obtained using trityl radical showed intense saturation of the electron at the usual solid effect condition, which involves a single electron and nucleus. However, higher order solid effect transitions involving two, three, or four nuclei were also observed with surprising intensity, although these transitions did not lead to bulk nuclear polarization—suggesting that higher order transitions are important primarily in the transfer of polarization to nuclei nearby the electron. Similar results were obtained for the SA-BDPA radical where strong electron-nuclear couplings produced splittings in the spectrum of the indirectly observed solid effect conditions. Observation of high order solid effect transitions supports recent studies of the solid effect, and suggests that a multi-spin solid effect mechanism may play a major role in polarization transfer via DNP.

  2. Electron capture decay of {sup 116}In and nuclear structure of double {beta} decays

    SciTech Connect

    Bhattacharya, M.; Garcia, A.; Ortiz, C.E.; Kaloskamis, N.I.; Hindi, M.M.; Norman, E.B.; Davids, C.N.; Civitarese, O.; Suhonen, J.

    1998-08-01

    Quasiparticle-random-phase-approximation (QRPA) calculations of double {beta} decays have not been able to reproduce data in the A=100 system. We propose the A=116 system{emdash}because of its smaller deformation{emdash}as a simpler system to test QRPA calculations. We present results of two experiments we performed, which determine the electron-capture-decay branch of {sup 116}In to be (2.27{plus_minus}0.63){times}10{sup {minus}2}{percent}, from which we deduce logft=4.39{sub {minus}0.15}{sup +0.10}. We present QRPA calculations and compare their predictions to experimental data. Finally we use these calculations to predict the 2{nu} double-{beta}-decay rate of {sup 116}Cd to the ground and excited states of {sup 116}Sn. {copyright} {ital 1998} {ital The American Physical Society}

  3. 31P electron-nuclear double resonance of the PIn antisite in InP:Zn detected via luminescence

    NASA Astrophysics Data System (ADS)

    Crookham, H. C.; Kennedy, T. A.; Treacy, D. J.

    1992-07-01

    Optically detected electron-nuclear double resonance (ODENDOR) has been observed via photoluminescence from the first-neighbor 31P shell of the phosphorus antisite in zinc-doped InP. Analysis of the ENDOR data confirms a tetrahedral arrangement of 31P nuclei. The hyperfine interaction for each of these nuclei is axial with ||A∥||/h=368.0+/-0.5 MHz and ||A⊥||/h=247.8+/-0.5 MHz. These parameters are slightly different from those reported by Jeon et al. [Phys. Rev. B 36, 1324 (1987)]. A shift of the ENDOR frequencies correlated with a change in the central nuclear-spin state has also been observed. We have been able to account for this shift with a perturbation treatment in which the electronic spin and central nuclear spin are treated exactly and a neighboring nuclear spin provides the perturbation. The best ENDOR signals are obtained with low optical-excitation-power density (~0.1 W/cm2) and low microwave modulation frequency (17 Hz). These conditions emphasize the contributions to the optically detected magnetic-resonance signal from distant donor-acceptor pairs.

  4. Electron-nuclear double resonance and hyperfine sublevel correlation spectroscopic studies of flavodoxin mutants from Anabaena sp. PCC 7119.

    PubMed Central

    Medina, M; Lostao, A; Sancho, J; Gómez-Moreno, C; Cammack, R; Alonso, P J; Martínez, J I

    1999-01-01

    The influence of the amino acid residues surrounding the flavin ring in the flavodoxin of the cyanobacterium Anabaena PCC 7119 on the electron spin density distribution of the flavin semiquinone was examined in mutants of the key residues Trp(57) and Tyr(94) at the FMN binding site. Neutral semiquinone radicals of the proteins were obtained by photoreduction and examined by electron-nuclear double resonance (ENDOR) and hyperfine sublevel correlation (HYSCORE) spectroscopies. Significant differences in electron density distribution were observed in the flavodoxin mutants Trp(57) --> Ala and Tyr(94) --> Ala. The results indicate that the presence of a bulky residue (either aromatic or aliphatic) at position 57, as compared with an alanine, decreases the electron spin density in the nuclei of the benzene flavin ring, whereas an aromatic residue at position 94 increases the electron spin density at positions N(5) and C(6) of the flavin ring. The influence of the FMN ribityl and phosphate on the flavin semiquinone was determined by reconstituting apoflavodoxin samples with riboflavin and with lumiflavin. The coupling parameters of the different nuclei of the isoalloxazine group, as detected by ENDOR and HYSCORE, were very similar to those of the native flavodoxin. This indicates that the protein conformation around the flavin ring and the electron density distribution in the semiquinone form are not influenced by the phosphate and the ribityl of FMN. PMID:10465780

  5. Structure of radical cations of saturated heterocyclic compounds with two heteroatoms as studied by electron paramagnetic resonance, electron-nuclear double resonance, and density functional theory calculations.

    PubMed

    Nuzhdin, Kirill B; Nesterov, Sergej V; Tyurin, Daniil A; Feldman, Vladimir I; Wei, Liu; Lund, Anders

    2005-07-21

    The radical cations of piperazine, morpholine, thiomorpholine, and thioxane were investigated by electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy in a solid Freon matrix. Optimized geometry and magnetic parameters of the radical cations were calculated using a density functional theory (DFT)/Perdew-Burke-Ernzerhof (PBE) method. Both experimental and theoretical results suggest that all the studied species adopt chair (or distorted chair) conformations. No evidence for the boat conformers with intramolecular sigma-bonding between heteroatoms were obtained. In the cases of morpholine and thioxane, the oxygen atoms are characterized by relatively small spin populations, whereas a major part of spin density is located at N and S atoms, respectively. The thiomorpholine radical cation exhibits nearly equal spin population of N and S atoms. In most cases (except for thioxane), the calculated magnetic parameters agree with the experimental data reasonably well.

  6. Electron nuclear double resonance study of photostimulated luminescence active centers in CsBr:Eu{sup 2+} medical imaging plates

    SciTech Connect

    Vrielinck, H.; Loncke, F.; Matthys, P.; Callens, F.; Tahon, J.-P.; Leblans, P.

    2011-02-01

    CsBr:Eu{sup 2+} needle image plates exhibit an electron-paramagnetic-resonance (EPR) spectrum at room temperature (RT), whose intensity is correlated with the photostimulated luminescence sensitivity of the plate. This EPR spectrum shows a strong temperature dependence: At RT it is owing to a single Eu{sup 2+} (S =7/2) center with axial symmetry, whereas at T<35 K the spectra can only be explained when two distinct centers are assumed to be present, a minority axial center and a majority center with nearly extremely rhombic symmetry. In this paper these low-temperature centers are studied with electron nuclear double resonance (ENDOR) spectroscopy, which reveals the presence of {sup 1}H nuclei close to the central Eu{sup 2+} ions in the centers. Analysis of the angular dependence of the ENDOR spectra allows to propose models for these centers, providing an explanation for the observed difference in intensity between the spectral components and for their temperature dependence.

  7. Electron-nuclear double resonance studies of point defects in silver gallium selenide and zinc germanium phosphide

    NASA Astrophysics Data System (ADS)

    Stevens, Kevin Taylor

    Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) studies have been performed on two chalcopyrite crystals grown by the horizontal-gradient-freeze technique. An impurity defect has been characterized in silver gallium selenide (AgGaSe2) and has been identified as a Ni+ ion substituting for a Ag+ ion. This nickel defect exists in as-grown crystals in the paramagnetic state. A complete ENDOR angular dependence study provided spin-Hamiltonian parameters for the 61Ni isotope as well as the neighboring selenium ions (77Se) and gallium ions (69Ga and 71Ga). Optical absorption data taken at room temperature and low temperature showed a broad band peaking near 2.2 microns. The zero-phonon line position was determined from the low temperature data. The EPR and optical absorption data were consistent with each other, suggesting the absorption band was associated with Ni+ impurities. Two point defects have been identified and characterized in zinc germanium phosphide (ZnGeP 2). The first is a copper impurity, which substitutes for a zinc ion in the ZnGeP2 lattice. The copper impurity acts as a conventional acceptor and is not paramagnetic in the as-grown condition, i.e., the light-off condition. Upon illumination of the sample with 633-nm or 1064-nm light, the copper acceptor gives up an electron and becomes paramagnetic. The EPR spectrum consists of resolved hyperfine due to the copper nucleus (63Cu and 65Cu) as well as neighboring phosphorous nuclei ( 31P). The spin-Hamiltonian parameters have been determined from ENDOR measurements of the light-induced EPR spectrum. The second defect that has been studied in ZnGeP2 is the previously identified zinc vacancy (VZn). EPR and ENDOR studies have previously characterized the g values and primary hyperfine interactions associated with the VZn. Further ENDOR measurements have been made in order to identify hyperfine interactions with more distant phosphorous neighbors. The results led to spin

  8. Characterization of calcium-binding sites in the kidney stone inhibitor glycoprotein nephrocalcin with vanadyl ions: electron paramagnetic resonance and electron nuclear double resonance spectroscopy.

    PubMed Central

    Mustafi, D; Nakagawa, Y

    1994-01-01

    Nephrocalcin (NC) is a calcium-binding glycoprotein of 14,000 molecular weight. It inhibits the growth of calcium oxalate monohydrate crystals in renal tubules. The NC used in this study was isolated from bovine kidney tissue and purified with the use of DEAE-cellulose chromatography into four isoforms, designated as fractions A-D. They differ primarily according to the content of phosphate and gamma-carboxy-glutamic acid. Fractions A and B are strong inhibitors of the growth of calcium oxalate monohydrate crystal, whereas fractions C and D inhibit crystal growth weakly. Fraction A, with the highest Ca(2+)-binding affinity, was characterized with respect to its metal-binding sites by using the vanadyl ion (VO2+) as a paramagnetic probe in electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) spectroscopic studies. By EPR spectrometric titration, it was shown that fraction A of NC bound VO2+ with a stoichiometry of metal:protein binding of 4:1. Also, the binding of VO2+ to NC was shown to be competitive with Ca2+. Only protein residues were detected by proton ENDOR as ligands, and these ligands bound with complete exclusion of solvent from the inner coordination sphere of the metal ion. This type of metal-binding environment, as derived from VO(2+)-reconstituted NC, differs significantly from the binding sites in other Ca(2+)-binding proteins. PMID:7972057

  9. 15N electron nuclear double resonance of the primary donor cation radical P+.865 in reaction centers of Rhodopseudomonas sphaeroides: additional evidence for the dimer model.

    PubMed Central

    Lubitz, W; Isaacson, R A; Abresch, E C; Feher, G

    1984-01-01

    Four 15N hyperfine coupling constants, including signs, have been measured by electron nuclear double resonance (ENDOR) and electron nuclear nuclear triple resonance (TRIPLE) for the bacteriochlorophyll a radical cation, BChla+., in vitro and for the light-induced primary donor radical cation, P+.865, in reaction centers of Rhodopseudomonas sphaeroides R-26. A comparison of the data shows that the hyperfine coupling constants have the same sign in both radicals and are, on the average, smaller by a factor of 2 in P+.865. These results provide additional evidence that P+.865 is a bacteriochlorophyll dimer and are in contradiction with the monomer structure of P+.865 recently proposed by O'Malley and Babcock. The reduction factors of the individual 15N couplings, together with the evidence from proton ENDOR data and molecular orbital calculations, indicate a dimer structure in which only two rings (either I and I or III and III) of the bacteriochlorophyll macrocycles overlap. PMID:6096857

  10. Electron Paramagnetic Resonance and Electron-Nuclear Double Resonance Studies of the Reactions of Cryogenerated Hydroperoxoferric–Hemoprotein Intermediates

    PubMed Central

    2015-01-01

    The fleeting ferric peroxo and hydroperoxo intermediates of dioxygen activation by hemoproteins can be readily trapped and characterized during cryoradiolytic reduction of ferrous hemoprotein–O2 complexes at 77 K. Previous cryoannealing studies suggested that the relaxation of cryogenerated hydroperoxoferric intermediates of myoglobin (Mb), hemoglobin, and horseradish peroxidase (HRP), either trapped directly at 77 K or generated by cryoannealing of a trapped peroxo-ferric state, proceeds through dissociation of bound H2O2 and formation of the ferric heme without formation of the ferryl porphyrin π-cation radical intermediate, compound I (Cpd I). Herein we have reinvestigated the mechanism of decays of the cryogenerated hydroperoxyferric intermediates of α- and β-chains of human hemoglobin, HRP, and chloroperoxidase (CPO). The latter two proteins are well-known to form spectroscopically detectable quasistable Cpds I. Peroxoferric intermediates are trapped during 77 K cryoreduction of oxy Mb, α-chains, and β-chains of human hemoglobin and CPO. They convert into hydroperoxoferric intermediates during annealing at temperatures above 160 K. The hydroperoxoferric intermediate of HRP is trapped directly at 77 K. All studied hydroperoxoferric intermediates decay with measurable rates at temperatures above 170 K with appreciable solvent kinetic isotope effects. The hydroperoxoferric intermediate of β-chains converts to the S = 3/2 Cpd I, which in turn decays to an electron paramagnetic resonance (EPR)-silent product at temperature above 220 K. For all the other hemoproteins studied, cryoannealing of the hydroperoxo intermediate directly yields an EPR-silent majority product. In each case, a second follow-up 77 K γ-irradiation of the annealed samples yields low-spin EPR signals characteristic of cryoreduced ferrylheme (compound II, Cpd II). This indicates that in general the hydroperoxoferric intermediates relax to Cpd I during cryoanealing at low temperatures, but

  11. Hyperfine selectivity using multiquantum electron-nuclear-electron triple resonance

    NASA Astrophysics Data System (ADS)

    Christidis, T. C.; Mchaourab, Hassane S.; Hyde, James S.

    1996-06-01

    Hyperfine selectivity is demonstrated in a continuous wave electron-nuclear double resonance (ENDOR) experiment. A multiquantum electron-electron double resonance (ELDOR) signal is monitored as a function of the nuclear radio frequency. The signs and relative intensities of the ENDOR lines permit separating the case where both ELDOR and ENDOR frequencies match hyperfine couplings from the cases where this condition is not satisfied.

  12. Electron-capture branch of {sup 100}Tc and tests of nuclear wave functions for double-{beta} decays.

    SciTech Connect

    Sjue, S. K. L.; Melconian, D.; Garcia, A.; Ahmad, I.; Algora, A.; Aysto, J.; Elomaa, V.-V.; Eronen, T.; Hakala, J.; Hoedl, S.; Kankainen, A.; Kessler, T.; Moore, I. D.; Naabe, F.; Penttila, H.; Rahaman, S.; Saastamoinen, A.; Swanson, H. E.; Weber, C.; Triambak, S.; Deryckx, K.; Physics; Univ. of Washington; Texas A&M Univ.; Univ. of Valencia; Hungarian Academy of Sciences; Univ. of Jyvaskyla; Univ. of Michigan

    2008-12-30

    We present a measurement of the electron-capture branch of {sup 100}Tc. Our value, B(EC) = (2.6 {+-} 0.4) x 10{sup -5}, implies that the {sup 100}Mo neutrino absorption cross section to the ground state of {sup 100}Tc is roughly 50% larger than previously thought. Disagreement between the experimental value and QRPA calculations relevant to double-{beta} decay matrix elements persists. We find agreement with previous measurements of the 539.5- and 590.8-keV {gamma}-ray intensities.

  13. Double coupled electron shuttle

    NASA Astrophysics Data System (ADS)

    Prada, M.; Platero, G.

    2012-10-01

    A nanoshuttle consisting of two movable islands connected in series and integrated between two contacts is studied. We evaluate the electron transport through the system in the presence of a source-drain voltage with and without an rf excitation. We evaluate the response of the system in terms of the net direct current enhanced by the mechanical motion of the oscillators. An introduction to the charge stability diagram is given in terms of electrochemical potentials and mechanical displacements. The low capacitance of the islands allows the observation of Coulomb blockade even at room temperature. Using radio frequency excitations, the nonlinear dynamics of the system is studied. The oscillators can be tuned to unstable regions where mechanically assisted transfer of electrons can further increase the amplitude of motion, resulting of a net energy being pumped into the system. The resulting amplified response can be exploited to design a mechanical motion detector of nanoscale objects.

  14. Electron-nuclear and electron-electron double resonance spectroscopies show that the primary quinone acceptor QA in reaction centers from photosynthetic bacteria Rhodobacter sphaeroides remains in the same orientation upon light-induced reduction.

    PubMed

    Flores, Marco; Savitsky, Anton; Paddock, Mark L; Abresch, Edward C; Dubinskii, Alexander A; Okamura, Melvin Y; Lubitz, Wolfgang; Möbius, Klaus

    2010-12-23

    Reaction centers (RCs) from the photosynthetic bacterium Rhodobacter (Rb.) sphaeroides R-26 exhibit changes in the recombination kinetics of the charge-separated radical-pair state, P(·+) Q(A)(·-), composed of the dimeric bacteriochlorophyll donor P and the ubiquinone-10 acceptor Q(A), depending on whether the RCs are cooled to cryogenic temperatures in the dark or under continuous illumination (Kleinfeld et al. Biochemistry 1984, 23, 5780-5786). Structural changes near redox-active cofactors have been postulated to be responsible for these changes in kinetics and to occur in the course of light-induced oxidation and reduction of the cofactors thereby assuring a high quantum yield. Here we investigated such potential light-induced structural changes, associated with the formation of P(·+) Q(A)(·-), via pulsed electron-nuclear double resonance (ENDOR) at Q-band (34 GHz) and pulsed electron-electron double resonance (PELDOR) at W-band (95 GHz). Two types of light excitation have been employed for which identical RC samples were prepared: (a) one sample was frozen in the dark and then illuminated to generate transient P(·+) Q(A)(·-), and (b) one was frozen under illumination which resulted in both trapped and transient P(·+) Q(A)(·-) at 80 K. The hyperfine interactions between Q(A)(·-) and the protein were found to be the same in RCs frozen in the dark as in RCs frozen under illumination. Furthermore, these interactions are completely consistent with those observed in RC crystals frozen in the dark. Thus, QA remains in its binding site with the same position and orientation upon reduction. This conclusion is consistent with the result of our orientation-resolving PELDOR experiments on transient P(·+) Q(A)(·-) radical pairs. However, these findings are incompatible with the recently proposed ~60° reorientation of Q(A) upon its photoreduction, as deduced from an analysis of Q-band quantum-beat oscillations (Heinen et al. J. Am. Chem. Soc. 2007, 129, 15935

  15. Dynamical cooling of nuclear spins in double quantum dots.

    PubMed

    Rudner, M S; Levitov, L S

    2010-07-09

    Electrons trapped in quantum dots can exhibit quantum-coherent spin dynamics over long timescales. These timescales are limited by the coupling of electron spins to the disordered nuclear spin background, which is a major source of noise and dephasing in such systems. We propose a scheme for controlling and suppressing fluctuations of nuclear spin polarization in double quantum dots, which uses nuclear spin pumping in the spin-blockade regime. We show that nuclear spin polarization fluctuations can be suppressed when electronic levels in the two dots are properly positioned near resonance. The proposed mechanism is analogous to that of optical Doppler cooling. The Overhauser shift due to fluctuations of nuclear polarization brings electron levels in and out of resonance, creating internal feedback to suppress fluctuations. Estimates indicate that a better than 10-fold reduction of fluctuations is possible.

  16. Q-Band Electron-Nuclear Double Resonance Reveals Out-of-Plane Hydrogen Bonds Stabilize an Anionic Ubisemiquinone in Cytochrome bo3 from Escherichia coli.

    PubMed

    Sun, Chang; Taguchi, Alexander T; Vermaas, Josh V; Beal, Nathan J; O'Malley, Patrick J; Tajkhorshid, Emad; Gennis, Robert B; Dikanov, Sergei A

    2016-10-11

    The respiratory cytochrome bo3 ubiquinol oxidase from Escherichia coli has a high-affinity ubiquinone binding site that stabilizes the one-electron reduced ubisemiquinone (SQH), which is a transient intermediate during the electron-mediated reduction of O2 to water. It is known that SQH is stabilized by two strong hydrogen bonds from R71 and D75 to ubiquinone carbonyl oxygen O1 and weak hydrogen bonds from H98 and Q101 to O4. In this work, SQH was investigated with orientation-selective Q-band (∼34 GHz) pulsed (1)H electron-nuclear double resonance (ENDOR) spectroscopy on fully deuterated cytochrome (cyt) bo3 in a H2O solvent so that only exchangeable protons contribute to the observed ENDOR spectra. Simulations of the experimental ENDOR spectra provided the principal values and directions of the hyperfine (hfi) tensors for the two strongly coupled H-bond protons (H1 and H2). For H1, the largest principal component of the proton anisotropic hfi tensor Tz' = 11.8 MHz, whereas for H2, Tz' = 8.6 MHz. Remarkably, the data show that the direction of the H1 H-bond is nearly perpendicular to the quinone plane (∼70° out of plane). The orientation of the second strong hydrogen bond, H2, is out of plane by ∼25°. Equilibrium molecular dynamics simulations on a membrane-embedded model of the cyt bo3 QH site show that these H-bond orientations are plausible but do not distinguish which H-bond, from R71 or D75, is nearly perpendicular to the quinone ring. Density functional theory calculations support the idea that the distances and geometries of the H-bonds to the ubiquinone carbonyl oxygens, along with the measured proton anisotropic hfi couplings, are most compatible with an anionic (deprotonated) ubisemiquinone.

  17. Pulsed electron-nuclear-electron triple resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Thomann, Hans; Bernardo, Marcelino

    1990-05-01

    A new experimental technique, pulsed electron-nuclear-electron triple resonance spectroscopy, is demonstrated. It is based on a modification of the pulse sequence for electron-nuclear double resonance (ENDOR) in which two EPR and one NMR transition are irradiated. The irradiation of one EPR transition is detected via a second EPR transition. The nuclear hyperfine coupling, which separates these EPR transition frequencies, is the irradiated NMR transition. The major advantages of triple resonance spectroscopy include the ability to resolve overlapping nuclear resonances in the ENDOR spectrum and a more direct quantitative assignment of nuclear hyperfine and quadrupole couplings. The triple resonance experiment is an alternative to the recently proposed method of employing rapid magnetic field jumps between microwave pulses for generating hyperfine selective ENDOR spectra.

  18. Influence of Ring-Expanded N-Heterocyclic Carbenes on the Structures of Half-Sandwich Ni(I) Complexes: An X-ray, Electron Paramagnetic Resonance (EPR), and Electron Nuclear Double Resonance (ENDOR) Study.

    PubMed

    Pelties, Stefan; Carter, Emma; Folli, Andrea; Mahon, Mary F; Murphy, Damien M; Whittlesey, Michael K; Wolf, Robert

    2016-11-07

    Potassium graphite reduction of the half-sandwich Ni(II) ring-expanded diamino/diamidocarbene complexes CpNi(RE-NHC)Br gave the Ni(I) derivatives CpNi(RE-NHC) (where RE-NHC = 6-Mes (1), 7-Mes (2), 6-MesDAC (3)) in yields of 40%-50%. The electronic structures of paramagnetic 1-3 were investigated by CW X-/Q-band electron paramagnetic resonance (EPR) and Q-band (1)H electron nuclear double resonance (ENDOR) spectroscopy. While small variations in the g-values were observed between the diaminocarbene complexes 1 and 2, pronounced changes in the g-values were detected between the almost isostructural species (1) and diamidocarbene species (3). These results highlight the sensitivity of the EPR g-tensor to changes in the electronic structure of the Ni(I) centers generated by incorporation of heteroatom substituents onto the backbone ring positions. Variable-temperature EPR analysis also revealed the presence of a second Ni(I) site in 3. The experimental g-values for these two Ni(I) sites detected by EPR in frozen solutions of 3 are consistent with resolution on the EPR time scale of the disordered components evident in the X-ray crystallographically determined structure and the corresponding density functional theory (DFT)-calculated g-tensor. Q-band (1)H ENDOR measurements revealed a small amount of unpaired electron spin density on the Cp rings, consistent with the calculated SOMO of complexes 1-3. The magnitude of the (1)H A values for 3 were also notably larger, compared to 1 and 2, again highlighting the influence of the diamidocarbene on the electronic properties of 3.

  19. Nuclear-resonant electron scattering

    NASA Astrophysics Data System (ADS)

    Pálffy, Adriana; Harman, Zoltán

    2008-04-01

    We investigate nuclear-resonant electron scattering as occurring in the two-step process of nuclear excitation by electron capture (NEEC) followed by internal conversion. The nuclear excitation and decay are treated by a phenomenological collective model in which nuclear states and transition probabilities are described by experimental parameters. We present capture rates and resonant strengths for a number of heavy-ion collision systems considering various scenarios for the resonant electron-scattering process. The results show that for certain cases resonant electron scattering can have significantly larger resonance strengths than NEEC followed by the radiative decay of the nucleus. We discuss the impact of our findings on the possible experimental observation of NEEC.

  20. Ultrafast electronic dynamics driven by nuclear motion

    NASA Astrophysics Data System (ADS)

    Vendrell, Oriol

    2016-05-01

    The transfer of electrical charge on a microscopic scale plays a fundamental role in chemistry, in biology, and in technological applications. In this contribution, we will discuss situations in which nuclear motion plays a central role in driving the electronic dynamics of photo-excited or photo-ionized molecular systems. In particular, we will explore theoretically the ultrafast transfer of a double electron hole between the functional groups of glycine after K-shell ionization and subsequent Auger decay. Although a large energy gap of about 15 eV initially exists between the two electronic states involved and coherent electronic dynamics play no role in the hole transfer, we will illustrate how the double hole can be transferred within 3 to 4 fs between both functional ends of the glycine molecule driven solely by specific nuclear displacements and non-Born-Oppenheimer effects. This finding challenges the common wisdom that nuclear dynamics of the molecular skeleton are unimportant for charge transfer processes at the few-femtosecond time scale and shows that they can even play a prominent role. We thank the Hamburg Centre for Ultrafast Imaging and the Volkswagen Foundation for financial support.

  1. Double-clad nuclear fuel safety rod

    DOEpatents

    McCarthy, William H.; Atcheson, Donald B.; Vaidyanathan, Swaminathan

    1984-01-01

    A device for shutting down a nuclear reactor during an undercooling or overpower event, whether or not the reactor's scram system operates properly. This is accomplished by double-clad fuel safety rods positioned at various locations throughout the reactor core, wherein melting of a secondary internal cladding of the rod allows the fuel column therein to shift from the reactor core to place the reactor in a subcritical condition.

  2. Nuclear astrophysics and electron beams

    SciTech Connect

    Schwenk, A.

    2013-11-07

    Electron beams provide important probes and constraints for nuclear astrophysics. This is especially exciting at energies within the regime of chiral effective field theory (EFT), which provides a systematic expansion for nuclear forces and electroweak operators based on quantum chromodynamics. This talk discusses some recent highlights and future directions based on chiral EFT, including nuclear structure and reactions for astrophysics, the neutron skin and constraints for the properties of neutron-rich matter in neutron stars and core-collapse supernovae, and the dark matter response of nuclei.

  3. Electron temperature differences and double layers

    NASA Technical Reports Server (NTRS)

    Chan, C.; Hershkowitz, N.; Lonngren, K. E.

    1983-01-01

    Electron temperature differences across plasma double layers are studied experimentally. It is shown that the temperature differences across a double layer can be varied and are not a result of thermalization of the bump-on-tail distribution. The implications of these results for electron thermal energy transport in laser-pellet and tandem-mirror experiments are also discussed.

  4. Mechanism-based inhibition reveals transitions between two conformational states in the action of lysine 5,6-aminomutase: a combination of electron paramagnetic resonance spectroscopy, electron nuclear double resonance spectroscopy, and density functional theory study.

    PubMed

    Chen, Yung-Han; Maity, Amarendra N; Frey, Perry A; Ke, Shyue-Chu

    2013-01-16

    An "open"-state crystal structure of lysine 5,6-aminomutase suggests that transition to a hypothetical "closed"-state is required to bring the cofactors adenosylcobalamin (AdoCbl) and pyridoxal-5'-phosphate (PLP) and the substrate into proximity for the radical-mediated 1,2-amino group migration. This process is achieved by transaldimination of the PLP-Lys144β internal aldimine with the PLP-substrate external aldimine. A closed-state crystal structure is not available. UV-vis and electron paramagnetic resonance studies show that homologues of substrate D-lysine, 2,5-DAPn, 2,4-DAB, and 2,3-DAPr bind to PLP as an external aldimine and elicit the AdoCbl Co-C bond homolysis and the accumulations of cob(II)alamin and analogue-based radicals, demonstrating the existence of a closed state. (2)H- and (31)P-electron nuclear double resonance studies, supported by computations, show that the position for hydrogen atom abstraction from 2,5-DAPn and 2,4-DAB by the 5'-deoxyadenosyl radical occurs at the carbon adjacent to the imine, resulting in overstabilized radicals by spin delocalization through the imine into the pyridine ring of PLP. These radicals block the active site, inhibit the enzyme, and poise the enzyme into two distinct conformations: for even-numbered analogues, the cob(II)alamin remains proximal to and spin-coupled with the analogue-based radical in the closed state while odd-numbered analogues could trigger the transition to the open state of the enzyme. We provide here direct spectroscopic evidence that strongly support the existence of a closed state and its analogue-dependent transition to the open state, which is one step that was proposed to complete the catalytic turnover of the substrate lysine.

  5. Double beta decays and neutrino nuclear responses

    NASA Astrophysics Data System (ADS)

    Ejiri, H.

    1999-05-01

    Neutrinos (ν) beyond the standard theory are studied by investigating double beta decays (ββ). The present status of ββ studies at RCNP is briefly reported. The ββ decays on 100Mo and 48Ca are studied at the Oto Cosmo Observatory. The Oto observatory is a new underground laboratory with low Rn and cosmic-ray backgrounds. The sensitivities expected there are 0.5 ˜ 1 eV for the Majorana ν-mass, 10 -6 ˜ 10 -8 for the right-handed weak currents, 2˜4.10 -5 for the ν-Majoron coupling, and so on. Nuclear axial weak responses for ββ-ν are investigated by charge-exchange spin-flip nuclear reactions.

  6. Controlled double-slit electron diffraction

    NASA Astrophysics Data System (ADS)

    Bach, Roger; Pope, Damian; Liou, Sy-Hwang; Batelaan, Herman

    2013-03-01

    Double-slit diffraction is a corner stone of quantum mechanics. It illustrates key features of quantum mechanics: interference and the particle-wave duality of matter. In 1965, Richard Feynman presented a thought experiment to show these features. Here we demonstrate the full realization of his famous thought experiment. By placing a movable mask in front of a double-slit to control the transmission through the individual slits, probability distributions for single- and double-slit arrangements were observed. Also, by recording single electron detection events diffracting through a double-slit, a diffraction pattern was built up from individual events.

  7. Electron density distribution in BaPb{sub 1-x}Sb{sub x}O{sub 3} superconducting oxides studied by double nuclear magnetic resonance methods

    SciTech Connect

    Piskunov, Yu. V. Ogloblichev, V. V.; Arapova, I. Yu.; Sadykov, A. V.; Gerashchenko, A. P.; Verkhovskii, S. V.

    2011-11-15

    The effect of charge disorder on the formation of an inhomogeneous state of the electron system in the conduction band in BaPb{sub 1-x}Sb{sub x}O{sub 3} superconducting oxides is investigated experimentally by NMR methods. The NMR spectra of {sup 17}O are measured systematically, and the contributions from {sup 17}O atoms with different cation nearest surroundings are identified. It is found that microscopic regions with an elevated spin density of charge carriers are formed within two coordination spheres near antimony ions. Nuclei of the superconducting phase of the oxide (regions with an elevated antimony concentration) microscopically distributed over the sample are detected in compounds with x = 0.25 and 0.33. Experiments in which a double resonance signal of the spin echo of {sup 17}O-{sup 207}Pb and {sup 17}O-{sup 121}Sb are measured in the metal phase of BaPb{sub 1-x}Sb{sub x}O{sub 3} oxides are carried out for the first time. The constants of indirect heteronuclear spin-spin {sup 17}O-{sup 207}Pb interaction are determined as functions of the local Knight shift {sub 207}Ks. The estimates of the constants of the indirect interaction between the nuclei of the nearest neighbors (O-Pb and Pb-Pb atoms) and analysis of evolution of the NMR spectra of {sup 17}O upon a change in the antimony concentration are convincing evidence in favor of the development of a microscopically inhomogeneous state of the electron system in the metal phase of BaPb{sub 1-x}Sb{sub x}O{sub 3} oxides.

  8. Electron-impact double ionization of magnesium

    SciTech Connect

    Ford, M.J.; El-Marji, B.; Doering, J.P.; Moore, J.H.; Coplan, M.A.; Cooper, J.W.

    1998-01-01

    Electron-impact double-ionization cross sections differential in the angles of the two ejected electrons have been measured at impact energies of 422 and 1052 eV. The energies of the ejected electrons were fixed at 100 eV each. The cross sections are very different at the two incident energies. At 1052 eV the ejected electrons are preferentially found in the forward direction with respect to the incident beam. At 422 eV they are found in the forward and backward directions with approximately equal probability. The 422-eV cross sections are largest when the incident-electron and ejected-electron momentum vectors lie in a common plane. The observations are discussed in the context of several models for double ionization. {copyright} {ital 1998} {ital The American Physical Society}

  9. Electron acceleration in stochastic double layers

    NASA Technical Reports Server (NTRS)

    Lotko, William

    1987-01-01

    Transversely localized double layers evolve randomly in turbulent regions of strongly magnetized plasma carrying current along the magnetic field. Results from numerical simulations and spacecraft observations in the auroral plasma indicate that the parallel electric field in such regions is microscopically intermittent or stochastic. The implications of stochastic double layer fields on electron acceleration will be discussed in terms of a statistical process involving ensemble averages over test particle motion. A Fokker-Planck equation can be derived for the electron phase space density, which depends on the mean and rms amplitudes of the double layers, the mean double layer density, and the initial electron velocity distribution. It is shown that the resulting electron acceleration is very sensitive to the ratio of the initial electron energy to the rms double layer amplitude. When this ratio is large, the acceleration process differs little from that expected in a dc electric field. When it is small, stochastic heating competes with directed acceleration. Evidence for both cases can be found in the auroral ionosphere in association with so-called inverted-V precipitation and collimated edge precipitation.

  10. Nuclear cusps in the HSF electron density

    NASA Astrophysics Data System (ADS)

    Cioslowski, Jerzy; Challacombe, Matt

    1994-07-01

    The Hiller-Sucher-Feinberg (HSF) identity provides an alternative definition for the electron density. The behavior of the HSF electron density in the vicinity of nuclei is analyzed. It is shown that the HSF density possesses nuclear cusps at which its gradient is discontinuous. The discontinuities in the HSF density gradient satisfy a simple equation analogous to Kato's electron-nuclear cusp condition. However, in contrast to Kato's condition, the electron-nuclear cusp condition is satisfied by HSF densities originating from both exact and approximate electronic wavefunctions. Several numerical examples are presented to illustrate this property of the HSF electron density.

  11. Au₂₅(SEt)₁₈, a nearly naked thiolate-protected Au₂₅ cluster: structural analysis by single crystal X-ray crystallography and electron nuclear double resonance.

    PubMed

    Dainese, Tiziano; Antonello, Sabrina; Gascón, José A; Pan, Fangfang; Perera, Neranjan V; Ruzzi, Marco; Venzo, Alfonso; Zoleo, Alfonso; Rissanen, Kari; Maran, Flavio

    2014-04-22

    X-ray crystallography has been fundamental in discovering fine structural features of ultrasmall gold clusters capped by thiolated ligands. For still unknown structures, however, new tools capable of providing relevant structural information are sought. We prepared a 25-gold atom nanocluster protected by the smallest ligand ever used, ethanethiol. This cluster displays the electrochemistry, mass spectrometry, and UV-vis absorption spectroscopy features of similar Au25 clusters protected by 18 thiolated ligands. The anionic and the neutral form of Au25(SEt)18 were fully characterized by (1)H and (13)C NMR spectroscopy, which confirmed the monolayer's properties and the paramagnetism of neutral Au25(SEt)18(0). X-ray crystallography analysis of the latter provided the first known structure of a gold cluster protected by a simple, linear alkanethiolate. Here, we also report the direct observation by electron nuclear double resonance (ENDOR) of hyperfine interactions between a surface-delocalized unpaired electron and the gold atoms of a nanocluster. The advantages of knowing the exact molecular structure and having used such a small ligand allowed us to compare the experimental values of hyperfine couplings with DFT calculations unaffected by structure's approximations or omissions.

  12. Multi-electron double quantum dot spin qubits

    NASA Astrophysics Data System (ADS)

    Nielsen, Erik; Kestner, Jason; Barnes, Edwin; Das Sarma, Sankar

    2013-03-01

    Double quantum dot (DQD) spin quits in a solid state environment typically consist of two electron spins confined to a DQD potential. We analyze the viability and potential advantages of DQD qubits which use greater then two electrons, and present results for six-electron qubits using full configuration interaction methods. The principal results of this work are that such six electron DQDs can retain an isolated low-energy qubit space that is more robust to charge noise due to screening. 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 Nuclear Security Administration under contract DE-AC04-94AL85000.

  13. Oil droplet versus electron double slit diffraction

    NASA Astrophysics Data System (ADS)

    Jones, Eric; Lif, Adam; McGregor, Scot; Bach, Roger; Batelaan, Herman

    2012-06-01

    The double-slit experiments for photons and electrons are considered cornerstones of modern physics. Feynman's account of these experiments is one of the most popular. To get as close to Feynman's description of double-slit diffraction we did some experiments. This includes closing individual slits on demand, and taking a movie of the build-up of the diffraction pattern one particle at a time. In recent work done in Paris [1], macroscopic particle-wave duality with bouncing oil droplets was demonstrated for the first time ever. This may have implications for microscopic or quantum-mechanical particle-wave duality for electrons and photons. We will report on our attempts to reproduce the Paris results, and show new results of the individual droplet trajectories and how they compare to de Broglie-Bohm trajectories. [4pt] [1] Yves Couder and Emmanuel Fort, Phys. Rev. Lett. 97, 154101 (2006)

  14. Nuclear state preparation via Landau-Zener-Stückelberg transitions in double quantum dots.

    PubMed

    Ribeiro, Hugo; Burkard, Guido

    2009-05-29

    We theoretically model a nuclear-state preparation scheme that increases the coherence time of a two-spin qubit in a double quantum dot. The two-electron system is tuned repeatedly across a singlet-triplet level anticrossing with alternating slow and rapid sweeps of an external bias voltage. Using a Landau-Zener-Stückelberg model, we find that in addition to a small nuclear polarization that weakly affects the electron spin coherence, the slow sweeps are only partially adiabatic and lead to a weak nuclear spin measurement and a nuclear-state narrowing which prolongs the electron spin coherence. This resolves some open problems brought up by a recent experiment [D. J. Reilly, Science 321, 817 (2008).10.1126/science.1159221]. Based on our description of the weak measurement, we simulate a system with up to n=200 nuclear spins per dot. Scaling in n indicates a stronger effect for larger n.

  15. Coronal electron confinement by double layers

    SciTech Connect

    Li, T. C.; Drake, J. F.; Swisdak, M.

    2013-12-01

    In observations of flare-heated electrons in the solar corona, a longstanding problem is the unexplained prolonged lifetime of the electrons compared to their transit time across the source. This suggests confinement. Recent particle-in-cell (PIC) simulations, which explored the transport of pre-accelerated hot electrons through ambient cold plasma, showed that the formation of a highly localized electrostatic potential drop, in the form of a double layer (DL), significantly inhibited the transport of hot electrons. The effectiveness of confinement by a DL is linked to the strength of the DL as defined by its potential drop. In this work, we investigate the scaling of the DL strength with the hot electron temperature by PIC simulations and find a linear scaling. We demonstrate that the strength is limited by the formation of parallel shocks. Based on this, we analytically determine the maximum DL strength, and also find a linear scaling with the hot electron temperature. The DL strength obtained from the analytic calculation is comparable to that from the simulations. At the maximum strength, the DL is capable of confining a significant fraction of hot electrons in the source.

  16. Locking electron spins into resonance by electron-nuclear feedback

    NASA Astrophysics Data System (ADS)

    Nowack, Katja

    2009-03-01

    All basic building blocks for spin-based quantum information processing using electron spins in GaAs quantum dots have recently been realized. Recent experiments have shown single-shot read-out of an individual spin [1], the implementation of the SWAP gate [2] and (magnetically induced) coherent single electron spin rotations [3]. However, the main drawback of using electron spins in a GaAs environment is the short spin coherence time, which is measured to be in the nanosecond range [2,4]. The source of this fast decoherence is the hyperfine interaction of the localized electron spin with the randomly fluctuating nuclear spins of the host lattice. The fluctuations of the nuclear spins have to be reduced to extend the electron spin coherence time. We therefore study the electron-nuclear spin interaction and use magnetically driven spin resonance to control the electron spin and indirectly manipulate the nuclear spins. We apply continuous microwave excitation to the electron spin and observe strong electron-nuclear feedback. One experimental signature of this feedback is the locking of the electron spin system into resonance with the microwaves. Once the electron spin is locked into resonance, this resonance condition remains fullfilled even when the external magnetic field or the microwave frequency is changed. This is due to dynamically build up nuclear polarizations (up to 500 mT) which generally counteract the external magnetic field. Locking of the electron spin system into resonance might indicate that the nuclear polarization exhibits stable configurations where fluctuations of the nuclear distribution are reduced [5]. [4pt] References [0pt] [1] J. M. Elzerman et al. , Nature 430, 431 (2004) [0pt] [2]. J. R. Petta et al., Science 309, 2180 (2005). [0pt] [3] F. H. L. Koppens et al., Nature 442, 766 (2006). [0pt] [4] F. H. L. Koppens et al., Phys. Rev. Lett. 100, 236802 (2008). [0pt] [5] J. Danon and Yu. V. Nazarov, private communication.

  17. Nuclear matrix elements for double-β decay

    NASA Astrophysics Data System (ADS)

    Barea, J.; Kotila, J.; Iachello, F.

    2013-01-01

    Background: Direct determination of the neutrino mass through double-β decay is at the present time one of the most important areas of experimental and theoretical research in nuclear and particle physics.Purpose: We calculate nuclear matrix elements for the extraction of the average neutrino mass in neutrinoless double-β decay.Methods: The microscopic interacting boson model (IBM-2) is used.Results: Nuclear matrix elements in the closure approximation are calculated for 48Ca, 76Ge, 82Se, 96Zr, 100Mo, 110Pd, 116Cd, 124Sn, 128Te, 130Te, 148Nd, 150Nd, 154Sm, 160Gd, and 198Pt decay.Conclusions: Realistic predictions for the expected half-lives in neutrinoless double-β decay with light and heavy neutrino exchange in terms of neutrino masses are made and limits are set from current experiments.

  18. Ultrafast Charge Transfer of a Valence Double Hole in Glycine Driven Exclusively by Nuclear Motion

    NASA Astrophysics Data System (ADS)

    Li, Zheng; Vendrell, Oriol; Santra, Robin

    2015-10-01

    We explore theoretically the ultrafast transfer of a double electron hole between the functional groups of glycine after K -shell ionization and subsequent Auger decay. Although a large energy gap of about 15 eV initially exists between the two electronic states involved and coherent electronic dynamics play no role in the hole transfer, we find that the double hole is transferred within 3 to 4 fs between both functional ends of the glycine molecule driven solely by specific nuclear displacements and non-Born-Oppenheimer effects. The nuclear displacements along specific vibrational modes are of the order of 15% of a typical chemical bond between carbon, oxygen, and nitrogen atoms and about 30% for bonds involving hydrogen atoms. The time required for the hole transfer corresponds to less than half a vibrational period of the involved nuclear modes. This finding challenges the common wisdom that nuclear dynamics of the molecular skeleton are unimportant for charge transfer processes at the few-femtosecond time scale and shows that they can even play a prominent role. It also indicates that in x-ray imaging experiments, in which ionization is unavoidable, valence electron redistribution caused by nuclear dynamics might be much faster than previously anticipated. Thus, non-Born-Oppenheimer effects may affect the apparent electron densities extracted from such measurements.

  19. Nuclear matrix elements for double-β decay

    SciTech Connect

    Engel, Jonathan

    2015-07-15

    Recent progress in nuclear-structure theory has been dramatic. I describe applications in progress of ab inito calculations to double-beta decay, and discuss the recent and future application of generator-coordinate methods to the same problem. I also discuss the old and vexing problem of the renormalization of the weak nuclear axial-vector coupling constant “in medium” and plans to resolve it.

  20. Modulation scheme for electron-electron double resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Mehlkopf, A. F.; Kuiper, F. G.; Smidt, J.; Tiggelman, T. A.

    1983-06-01

    A modulation scheme for electron-electron double resonance (ELDOR) spectrometers is presented. With this scheme an optimum stabilization signal for locking the pump microwave generator to the pumped electron paramagnetic resonance (EPR) line is generated. A separate pump power level and a separate magnetic field modulation amplitude are used for the purpose of locking. In general, such a modulation scheme introduces false ELDOR lines. These false lines disturb the real ELDOR signals, or introduce an ELDOR signal in the absence of any communication between the observed EPR line and the pumped EPR line. With the described modulation scheme the frequencies of the false ELDOR signals are limited to even multiples of the frequency of the wanted ELDOR signals. This makes a suppression of the false ELDOR lines easy.

  1. Electron-nuclear-nuclear triple resonance of cis-rich polyacetylene —Evidence for negative spin sites of soliton

    NASA Astrophysics Data System (ADS)

    Kuroda, S.; Shirakawa, H.

    1991-03-01

    Electron-nuclear double resonance (ENDOR) and electron-nuclear-nuclear triple resonance (TRIPLE) spectra of stretch-oriented cis-rich polyacetylene at low temperatures show clear spectral turning points when the external magnetic field is parallel to the stretch direction. The difference between ENDOR and TRIPLE spectra, depending on the pumping frequency of the latter, provide direct evidence that the turning points are associated with the negative spin sites of the soliton, arising from electron correlation effect, as predicted from our previous ENDOR analysis.

  2. Nuclear Electronics: Superconducting Detectors and Processing Techniques

    NASA Astrophysics Data System (ADS)

    Polushkin, Vladimir

    2004-06-01

    With the commercialisation of superconducting particles and radiation detectors set to occur in the very near future, nuclear analytical instrumentation is taking a big step forward. These new detectors have a high degree of accuracy, stability and speed and are suitable for high-density multiplex integration in nuclear research laboratories and astrophysics. Furthermore, superconducting detectors can also be successfully applied to food safety, airport security systems, medical examinations, doping tests & forensic investigations. This book is the first to address a new generation of analytical tools based on new superconductor detectors demonstrating outstanding performance unsurpassed by any other conventional devices. Presenting the latest research and development in nanometer technologies and biochemistry this book: * Discusses the development of nuclear sensing techniques. * Provides guidance on the design and use of the next generation of detectors. * Describes cryogenic detectors for nuclear measurements and spectrometry. * Covers primary detectors, front-end readout electronics and digital signal processing. * Presents applications in nanotechnology and modern biochemistry including DNA sequencing, proteinomics, microorganisms. * Features examples of two applications in X-ray electron probe nanoanalysis and time-of-flight mass spectrometry. This comprehensive treatment is the ideal reference for researchers, industrial engineers and graduate students involved in the development of high precision nuclear measurements, nuclear analytical instrumentation and advanced superconductor primary sensors. This book will also appeal to physicists, electrical and electronic engineers in the nuclear industry.

  3. Neutrinoless Double Beta Nuclear Matrix Elements Around Mass 80 in the Nuclear Shell Model

    NASA Astrophysics Data System (ADS)

    Yoshinaga, Naotaka; Higashiyama, Koji; Taguchi, Daisuke; Teruya, Eri

    The observation of the neutrinoless double-beta decay can determine whether the neutrino is a Majorana particle or not. In its theoretical nuclear side it is particularly important to estimate three types of nuclear matrix elements, namely, Fermi (F), Gamow-Teller (GT), and tensor (T) types matrix elements. The shell model calculations and also the pair-truncated shell model calculations are carried out to check the model dependence on nuclear matrix elements. In this work the neutrinoless double-beta decay for mass A = 82 nuclei is studied. It is found that the matrix elements are quite sensitive to the ground state wavefunctions.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  5. Electron Scattering and Nuclear Structure

    ERIC Educational Resources Information Center

    Trower, W. P.; Ficenec, J. R.

    1971-01-01

    Presents information about the nucleus gained by studies of electron scattering. Discusses what can be implied about the shape of the charge distribution, the nucleus positions, the vibrational modes of the nucleus, the momentum of the nucleus, and the granularity and core structures of the nucleus. (DS)

  6. Electron Scattering and Nuclear Structure

    ERIC Educational Resources Information Center

    Trower, W. P.; Ficenec, J. R.

    1971-01-01

    Presents information about the nucleus gained by studies of electron scattering. Discusses what can be implied about the shape of the charge distribution, the nucleus positions, the vibrational modes of the nucleus, the momentum of the nucleus, and the granularity and core structures of the nucleus. (DS)

  7. MOON for double-beta decays and neutrino nuclear responses

    NASA Astrophysics Data System (ADS)

    Fushimi, K.; Kameda, Y.; Harada, K.; Nakayama, S.; Ejiri, H.; Shima, T.; Yasuda, K.; Hazama, R.; Imagawa, K.

    2010-01-01

    Thin and wide area inorganic crystal was tested for double beta decay experiment. The thin NaI(Tl) whose dimension of 18cm×18cm×0.5cm was developed. The energy resolution at Q-value of 100Mo was obtained less than 3% in full-width-half-maximum. Although the backscattering of electrons suffers the detection efficiency, the NaI(Tl) has the advantage for double beta decay experiment.

  8. Why Nature Uses Radical SAM Enzymes so Widely: Electron Nuclear Double Resonance Studies of Lysine 2,3-Aminomutase Show the 5'-dAdo• "Free Radical" Is Never Free.

    PubMed

    Horitani, Masaki; Byer, Amanda S; Shisler, Krista A; Chandra, Tilak; Broderick, Joan B; Hoffman, Brian M

    2015-06-10

    Lysine 2,3-aminomutase (LAM) is a radical S-adenosyl-L-methionine (SAM) enzyme and, like other members of this superfamily, LAM utilizes radical-generating machinery comprising SAM anchored to the unique Fe of a [4Fe-4S] cluster via a classical five-membered N,O chelate ring. Catalysis is initiated by reductive cleavage of the SAM S-C5' bond, which creates the highly reactive 5'-deoxyadenosyl radical (5'-dAdo•), the same radical generated by homolytic Co-C bond cleavage in B12 radical enzymes. The SAM surrogate S-3',4'-anhydroadenosyl-L-methionine (anSAM) can replace SAM as a cofactor in the isomerization of L-α-lysine to L-β-lysine by LAM, via the stable allylic anhydroadenosyl radical (anAdo•). Here electron nuclear double resonance (ENDOR) spectroscopy of the anAdo• radical in the presence of (13)C, (2)H, and (15)N-labeled lysine completes the picture of how the active site of LAM from Clostridium subterminale SB4 "tames" the 5'-dAdo• radical, preventing it from carrying out harmful side reactions: this "free radical" in LAM is never free. The low steric demands of the radical-generating [4Fe-4S]/SAM construct allow the substrate target to bind adjacent to the S-C5' bond, thereby enabling the 5'-dAdo• radical created by cleavage of this bond to react with its partners by undergoing small motions, ∼0.6 Å toward the target and ∼1.5 Å overall, that are controlled by tight van der Waals contact with its partners. We suggest that the accessibility to substrate and ready control of the reactive C5' radical, with "van der Waals control" of small motions throughout the catalytic cycle, is common within the radical SAM enzyme superfamily and is a major reason why these enzymes are the preferred means of initiating radical reactions in nature.

  9. Double-clad nuclear-fuel safety rod

    DOEpatents

    McCarthy, W.H.; Atcheson, D.B.

    1981-12-30

    A device for shutting down a nuclear reactor during an undercooling or overpower event, whether or not the reactor's scram system operates properly. This is accomplished by double-clad fuel safety rods positioned at various locations throughout the reactor core, wherein melting of a secondary internal cladding of the rod allows the fuel column therein to shift from the reactor core to place the reactor in a subcritical condition.

  10. Nuclear effects on tetraquark production by double parton scattering

    NASA Astrophysics Data System (ADS)

    Carvalho, F.; Navarra, F. S.

    2017-03-01

    In this work we study the nuclear effects in exotic meson production. We estimate the total cross section as a function of the energy for pPb scattering using a version of the color evaporation model (CEM) adapted to Double Parton Scattering (DPS). We fond that the cross section grows significantly with the atomic number, indicating that the hypothesis of tetraquark states can be tested in pA collisions at LHC.

  11. Double resonant enhancement in the neutrinoless double-electron capture of 190Pt

    NASA Astrophysics Data System (ADS)

    Eibach, M.; Bollen, G.; Gulyuz, K.; Izzo, C.; Redshaw, M.; Ringle, R.; Sandler, R.; Valverde, A. A.

    2016-07-01

    Background: The observation of neutrinoless double-β transitions would indicate physics beyond the standard model as the lepton number conservation is violated. For a complete degeneracy in the energy of the initial and final states, the neutrinoless double-electron capture is resonantly enhanced. This shortens the half-life to similar orders of magnitude as the neutrinoless double-β decay and expands the set of nuclei for the search of neutrinoless double-β transitions as the observation of either process would be equally likely. Purpose: To clearly identify transitions that are resonantly enhanced, among other parameters the total energy of the decay, Qɛ ɛ, needs to be measured very precisely. Of the 12 initially identified candidates, the last remaining decay without a precise Qɛ ɛ was 190Pt(0 ν ɛ ɛ )190Os . Method: The Qɛ ɛ value was determined with the Penning trap mass spectrometer LEBIT by measuring the ratio of the cyclotron frequencies of +190Pt and +190Os in a 9.4-T superconducting magnet. Result: The Qɛ ɛ value was determined to be 1401.57(47) keV with an uncertainty reduction of an order of magnitude compared to its previously known value. The absolute value is shifted by 17.17(623) keV relative to the previously accepted one. Furthermore, the mass value of 190Pt was found to be shifted by more than three standard deviations. In addition we improved the mass values for Os,190186 and 194Pt. Conclusion: Transitions to the two nuclear excited states of 190Os with 1326.9(5) and 1387.00(2) keV energy were identified to be resonantly enhanced within a 1 σ uncertainty. The significantly reduced uncertainty of Qɛ ɛ confirmed the potential for a resonantly enhanced transition.

  12. Nonadiabatic evolution of electronic states by electron nuclear dynamics theory

    NASA Astrophysics Data System (ADS)

    Hagelberg, Frank

    The problem of how to determine the nonadiabatic content of any given dynamic process involving molecular motion is addressed in the context of Electron Nuclear Dynamics (END) theory. Specifically, it is proposed to cast the dynamic END wave function into the language of static electronic configurations with time dependent complex-valued amplitudes. This is achieved by adiabatic transport of an electronic basis along the classical nuclear trajectories of the studied molecular system, as yielded by END simulation. Projecting the dynamic wave function on this basis yields a natural distinction between adiabatic and nonadiabatic components of the motion considered. Tracing the evolution of the leading configurations is shown to be a helpful device for clarifying the physical nature of electronic excitation processes. For illustration of these concepts, dynamic configuration analysis is applied to the scattering of a proton by a lithium atom.

  13. Electronic response to nuclear breathing mode

    SciTech Connect

    Ludwig, Hendrik; Ruffini, Remo; Xue, She-Sheng

    2015-12-17

    Based on our previous work on stationary oscillation modes of electrons around giant nuclei, we show how to treat a general driving force on the electron gas, such as the one generated by the breathing mode of the nucleus, by means of the spectral method. As an example we demonstrate this method for a system with Z = 10{sup 4} in β-equilibrium with the electrons compressed up to the nuclear radius. In this case the stationary modes can be obtained analytically, which allows for a very speedy numerical calculation of the final result.

  14. Coherent pump pulses in Double Electron Electron Resonance Spectroscopy

    PubMed Central

    Tait, Claudia E.; Stoll, Stefan

    2016-01-01

    The recent introduction of shaped pulses to Double Electron Electron Resonance (DEER) spectroscopy has led to significant enhancements in sensitivity through increased excitation bandwidths and improved control over spin dynamics. The application of DEER has so far relied on the presence of an incoherent pump channel to average out most undesired coherent effects of the pump pulse(s) on the observer spins. However, in fully coherent EPR spectrometers that are increasingly used to generate shaped pulses, the presence of coherent pump pulses means that these effects need to be explicitly considered. In this paper, we examine the effects of coherent rectangular and sech/tanh pump pulses in DEER experiments with up to three pump pulses. We show that, even in the absence of significant overlap of the observer and pump pulse excitation bandwidths, coherence transfer pathways involving both types of pulses generate spin echoes of considerable intensity. These echoes introduce artefacts, which, if not identified and removed, can easily lead to misinterpretation. We demonstrate that the observed echoes can be quantitatively modelled using a simple spin quantum dynamics approach that includes instrumental transfer functions. Based on an analysis of the echo crossing artefacts, we propose efficient phase cycling schemes for their suppression. This enables the use of advanced DEER experiments, characterized by high sensitivity and increased accuracy for long-distance measurements, on novel fully coherent EPR spectrometers. PMID:27339858

  15. Nuclear structure and depletion of nuclear isomers using electron linacs

    SciTech Connect

    Carroll, J. J.; Litz, M. S.; Henriquez, S. L.; Burns, D. A.; Netherton, K. A.; Pereira, N. R.; Karamian, S. A.

    2013-04-19

    Long-lived nuclear excited states (isomers) have proven important to understanding nuclear structure. With some isomers having half-lives of decades or longer, and intrinsic energy densities reaching 10{sup 12} J/kg, they have also been suggested for a wide range of applications. The ability to effectively transfer a population of nuclei from an isomer to shorter-lived levels will determine the feasibility of any applications. Here is described a first demonstration of the induced depletion of a population of the 438 year isomer of {sup 108}Ag to its 2.38 min ground state, using 6 MeV bremsstrahlung from a modified medical electron linac. The experiment suggests refinements to be implemented in the future and how a similar approach might be applied to study induced depletion of the 1200 year isomer of {sup 166}Ho.

  16. The electron screening puzzle and nuclear clustering

    SciTech Connect

    Spitaleri, C.; Bertulani, C. A.; Fortunato, L.; Vitturi, A.

    2016-02-12

    Accurate measurements of nuclear reactions of astrophysical interest within, or close to, the Gamow peak show evidence of an unexpected effect attributed to the presence of atomic electrons in the target. The experiments need to include an effective "screening" potential to explain the enhancement of the cross sections at the lowest measurable energies. Despite various theoretical studies conducted over the past 20 years and numerous experimental measurements, a theory has not yet been found that can explain the cause of the exceedingly high values of the screening potential needed to explain the data. Furthermore, in this letter we show that instead of an atomic physics solution of the "electron screening puzzle", the reason for the large screening potential values is in fact due to clusterization effects in nuclear reactions, in particular for reaction involving light nuclei.

  17. The electron screening puzzle and nuclear clustering

    DOE PAGES

    Spitaleri, C.; Bertulani, C. A.; Fortunato, L.; ...

    2016-02-12

    Accurate measurements of nuclear reactions of astrophysical interest within, or close to, the Gamow peak show evidence of an unexpected effect attributed to the presence of atomic electrons in the target. The experiments need to include an effective "screening" potential to explain the enhancement of the cross sections at the lowest measurable energies. Despite various theoretical studies conducted over the past 20 years and numerous experimental measurements, a theory has not yet been found that can explain the cause of the exceedingly high values of the screening potential needed to explain the data. Furthermore, in this letter we show thatmore » instead of an atomic physics solution of the "electron screening puzzle", the reason for the large screening potential values is in fact due to clusterization effects in nuclear reactions, in particular for reaction involving light nuclei.« less

  18. Radiation-induced radicals in glucose-1-phosphate. I. Electron paramagnetic resonance and electron nuclear double resonance analysis of in situ X-irradiated single crystals at 77 K.

    PubMed

    De Cooman, Hendrik; Vanhaelewyn, Gauthier; Pauwels, Ewald; Sagstuen, Einar; Waroquier, Michel; Callens, Freddy

    2008-11-27

    Electron magnetic resonance analysis of radiation-induced defects in dipotassium glucose-1-phosphate dihydrate single crystals in situ X-irradiated and measured at 77 K shows that at least seven different carbon-centered radical species are trapped. Four of these (R1-R4) can be fully or partly characterized in terms of proton hyperfine coupling tensors. The dominant radical (R2) is identified as a C1-centered species, assumedly formed by a scission of the sugar-phosphate junction and the concerted formation of a carbonyl group at the neighboring C2 carbon. This structure is chemically identical to a radical recently identified in irradiated sucrose single crystals. Radical species R1 and R4 most likely are C3- and C6-centered species, respectively, both formed by a net hydrogen abstraction. R3 is suggested to be chemically similar to but geometrically different from R4. Knowledge of the identity of the sugar radicals present at 77 K provides a first step in elucidating the formation mechanism of the phosphoryl radicals previously detected after X-irradiation at 280 K. In paper II, the chemical identity, precise conformation, and possible formation mechanisms of these radical species are investigated by means of DFT calculations and elementary insight into the radiation chemistry of sugar and sugar derivatives is obtained.

  19. Double Diffusive Natural Convection in a Nuclear Waste Repository

    SciTech Connect

    Y. Hao; J. Nitao; T.A. Buscheck; Y. Sun

    2006-03-28

    In this study, we conduct a two-dimensional numerical analysis of double diffusive natural convection in an emplacement drift for a nuclear waste repository. In-drift heat and moisture transport is driven by combined thermal- and compositional-induced buoyancy forces. Numerical results demonstrate buoyancy-driven convective flow patterns and configurations during both repository heat-up and cool-down phases. It is also shown that boundary conditions, particularly on the drip-shield surface, have strong impacts on the in-drift convective flow and transport.

  20. Double Diffusive Natural Convection in a Nuclear Waste Repository

    SciTech Connect

    Hao, Y; Nitao, J; Buscheck, T A; Sun, Y

    2006-02-03

    In this study, we conduct a two-dimensional numerical analysis of double diffusive natural convection in an emplacement drift for a nuclear waste repository. In-drift heat and moisture transport is driven by combined thermal- and compositional-induced buoyancy forces. Numerical results demonstrate buoyancy-driven convective flow patterns and configurations during both repository heat-up and cool-down phases. It is also shown that boundary conditions, particularly on the drip-shield surface, have strong impacts on the in-drift convective flow and transport.

  1. A double nuclear transfer technique for cloning pigs.

    PubMed

    Polejaeva, Irina A; Walker, Shawn; Campbell, Keith

    2006-01-01

    The first round of double nuclear transfer (NT) procedure includes the following steps: transfer of somatic cell nuclei into enucleated recipient oocytes, fusion, activation, and culture of reconstructed oocytes. The next day, a second round of NT is performed by removing karyoplasts from 1-d-old NT embryos and transferring them into in vivo-derived zygotes from which the two pronuclei have been removed. Couplets are then fused using an electrical pulse and transferred into synchronized recipient gilts. This system, which uses fertilized oocytes as cytoplast recipients, bypasses the inefficiencies of artificial activation procedures, and may promote more successful development.

  2. Double Diffusive Natural Convection in a Nuclear Waste Repository

    SciTech Connect

    Hao, Y; Nitao, J J; Buscheck, T A; Sun, Y

    2006-07-24

    In this study, we conduct a two dimensional numerical analysis of double diffusive natural convection in an emplacement drift for a nuclear waste repository. In-drift heat and moisture transport is driven by combined thermal- and compositional-induced buoyancy forces. Numerical results demonstrate buoyancy-driven convective flow patterns and configurations during both repository heat-up and cool-down phases. It is also shown that boundary conditions, particularly on the drip-shield surface, have a strong impact on in-drift convective flow and transport.

  3. Pumping of Dynamic Nuclear Polarization in GaAs Double Quantum Dots

    NASA Astrophysics Data System (ADS)

    Pal, Arijeet; Nichol, John; Shulman, Michael; Harvey, Shannon; Rashba, Emmanuel; Yacoby, Amir; Halperin, Bertrand

    2015-03-01

    Control of nuclear spins in semiconductors is essential for spin qubits realized using gate-defined quantum dots (QDs) for quantum computing. One qubit realization uses the singlet (S) and triplet Sz = 0 (T0) states of two electrons in a double QD. The difference in the Overhauser fields on the two dots provides an axis of rotation on the Bloch sphere orthogonal to the one produced by the exchange interaction. These fields, in turn, may be modified by a dynamic nuclear polarization protocol, in which the electronic system is swept repeatedly through the level crossing between the S and T+ states. In any given sweep, the hyperfine interaction may cause a transition from S to T+, thereby transferring electronic spin polarization to the nuclear spins. We find the dependence of the polarization process on the asymmetry of the electron wave function, which is induced by the Zeeman field even in geometrically symmetric dots and which leads to pumping of the difference in Overhauser fields. We further report on correlations between S -T+ transitions, which capture the macroscopic nuclear spin dynamics and the various relaxation mechanisms in this system. A semi-classical theoretical model is formulated which is in good agreement with the experimental observations.

  4. Neutrinoless double-β decay and nuclear transition matrix elements

    SciTech Connect

    Rath, P. K.

    2015-10-28

    Within mechanisms involving the light Majorana neutrinos, squark-neutrino, Majorons, sterile neutrinos and heavy Majorana neutrino, nuclear transition matrix elements for the neutrinoless (β{sup −}β{sup −}){sub 0ν} decay of {sup 96}Zr, {sup 100}Mo, {sup 128,130}Te and {sup 150}Nd nuclei are calculated by employing the PHFB approach. Effects due to finite size of nucleons, higher order currents, short range correlations, and deformations of parent as well as daughter nuclei on the calculated matrix elements are estimated. Uncertainties in nuclear transition matrix elements within long-ranged mechanisms but for double Majoron accompanied (β{sup −}β{sup −}ϕϕ){sub 0ν} decay modes are 9%–15%. In the case of short ranged heavy Majorona neutrino exchange mechanism, the maximum uncertainty is about 35%. The maximum systematic error within the mechanism involving the exchange of light Majorana neutrino is about 46%.

  5. Quantum electron-acoustic double layers in a magnetoplasma

    SciTech Connect

    Misra, A. P.; Samanta, S.

    2008-12-15

    Using a quantum magnetohydrodynamic (QMHD) model, the existence of small but finite amplitude quantum electron-acoustic double layers (QEADLs) is reported in a magnetized collisionless dense quantum plasma whose constituents are two distinct groups of cold and hot electrons, and the stationary ions forming only the neutralizing background. It is shown that the existence of steady state solutions of these double layers obtained from an extended Korteweg-de Vries (KdV) equation depends parametrically on the ratio of the cold to hot electron unperturbed number density ({delta}), the quantum diffraction parameter (H), the obliqueness parameter (l{sub z}), and the external magnetic field via the normalized electron-cyclotron frequency ({omega}). It is found that the system supports both compressive and rarefactive double layers depending on the parameters {delta} and l{sub z}. The effects of all these parameters on the profiles of the double layers are also examined numerically.

  6. Entangled electron and nuclear spin states in 15N@C60: Density matrix tomography

    NASA Astrophysics Data System (ADS)

    Scherer, Werner; Mehring, Michael

    2008-02-01

    Procedures of the preparation and detection of entangled electron-nuclear spin states in N15@C60 by combining electron spin resonance and electron nuclear double resonance pulse techniques are presented. A quantitative evaluation of the complete density matrix is obtained by a special density matrix tomography. All four Bell states of a two qubit subsystem were analyzed and experimental decoherence times are presented. In addition, we estimate a quantum critical temperature of Tq=7.76K for this system at an electron spin resonance frequency of 95GHz.

  7. Two-dimensional Electronic Double-Quantum Coherence Spectroscopy

    PubMed Central

    Kim, Jeongho; Mukamel, Shaul

    2009-01-01

    CONSPECTUS The theory of electronic structure of many-electron systems like molecules is extraordinarily complicated. A lot can be learned by considering how electron density is distributed, on average, in the average field of the other electrons in the system. That is, mean field theory. However, to describe quantitatively chemical bonds, reactions, and spectroscopy requires consideration of the way that electrons avoid each other by the way they move; this is called electron correlation (or in physics, the many-body problem for fermions). While great progress has been made in theory, there is a need for incisive experimental tests that can be undertaken for large molecular systems in the condensed phase. Here we report a two-dimensional (2D) optical coherent spectroscopy that correlates the double excited electronic states to constituent single excited states. The technique, termed two-dimensional double-coherence spectroscopy (2D-DQCS), makes use of multiple, time-ordered ultrashort coherent optical pulses to create double- and single-quantum coherences over time intervals between the pulses. The resulting two-dimensional electronic spectrum maps the energy correlation between the first excited state and two-photon allowed double-quantum states. The principle of the experiment is that when the energy of the double-quantum state, viewed in simple models as a double HOMO to LUMO excitation, equals twice that of a single excitation, then no signal is radiated. However, electron-electron interactions—a combination of exchange interactions and electron correlation—in real systems generates a signal that reveals precisely how the energy of the double-quantum resonance differs from twice the single-quantum resonance. The energy shift measured in this experiment reveals how the second excitation is perturbed by both the presence of the first excitation and the way that the other electrons in the system have responded to the presence of that first excitation. We

  8. Superconductivity: from Electron Interaction to Nuclear Superfluidity

    NASA Astrophysics Data System (ADS)

    Pines, David

    I present an expanded version of a talk given at the Urbana symposium that celebrated the fiftieth anniversary of the publication of the microscopic theory of superconductivity by Bardeen, Cooper, and Schrieffer — BCS. I recall at some length, the work with my Ph.D. mentor, David Bohm, and my postdoctoral mentor, John Bardeen, on electron interaction in metals during the period 1948-55 that helped pave the way for BCS, describe the immediate impact of BCS on a small segment of the Princeton physics community in the early spring of 1957, and discuss the extent to which the Bardeen-Pines-Frohlich effective electron-electron interaction provided a criterion for superconductivity in the periodic system. I describe my lectures on BCS at Niels Bohr's Institute of Theoretical Physics in June 1957 that led to the proposal of nuclear superfluidity, discuss nuclear and cosmic superfluids briefly, and close with a tribute to John Bardeen, whose birth centennial we celebrated in 2008, and who was my mentor, close colleague, and dear friend.

  9. Neutrinoless double beta nuclear matrix elements around mass 80 in the nuclear shell-model

    NASA Astrophysics Data System (ADS)

    Yoshinaga, N.; Higashiyama, K.; Taguchi, D.; Teruya, E.

    2015-05-01

    The observation of the neutrinoless double-beta decay can determine whether the neutrino is a Majorana particle or not. For theoretical nuclear physics it is particularly important to estimate three types of matrix elements, namely Fermi (F), Gamow-Teller (GT), and tensor (T) matrix elements. In this paper, we carry out shell-model calculations and also pair-truncated shell-model calculations to check the model dependence in the case of mass A=82 nuclei.

  10. Double relativistic electron-accelerating mirror

    SciTech Connect

    Andreev, Aleksandr A; Platonov, Konstantin Yu

    2013-05-31

    A numerical simulation of the interaction of a laser pulse with ultrathin targets has revealed a possibility of generating thin dense relativistic electron layers. The maximum kinetic energy of the electron mirror can be gained using an optimal combination of the target thickness and the laser pulse intensity and duration. It is proposed to use an additional (second) laser target, located at an optimal distance from the first target to cut off the laser pulse from the electron layer when the latter gains a maximum kinetic energy. This relativistic electron mirror can be used for efficient generation of 'hard' coherent radiation via counter reflection of an additional (probe) laser pulse from the mirror. (interaction of laser radiation with matter. laser plasma)

  11. Momentum spectra for single and double electron ionization of He in relativistic collisions

    NASA Astrophysics Data System (ADS)

    Wood, C. J.; Olson, R. E.; Schmitt, W.; Moshammer, R.; Ullrich, J.

    1997-11-01

    The complete momentum spectra for single and double ionization of He by 1-GeV/u (β=0.88) U92+ have been investigated using a classical trajectory Monte Carlo method corrected for the relativistic projectile. The 1/r12 electron-electron interaction has been included in the post-collision region for double ionization to incorporate the effects of both the nuclear-electron and electron-electron ionizing interactions, and to access the effects of electron correlation in the electron spectra. Experimental measurements were able to determine the longitudinal momentum spectra for single ionization; these observations are in accordance with the theoretical predictions for the three-body momentum balance between projectile, recoil ion, and ionized electron. In particular, the Lorentz contraction of the Coulomb interaction of the projectile manifests itself in the decrease of the post-collision interaction of the projectile with the electron and recoil ion, causing them to recoil back-to-back as in the case for a short electromagnetic pulse. This feature is clearly displayed in both the theoretical and experimental longitudinal momentum spectra, and by comparing to calculations that are performed at the same collision speed but do not include the relativistic potentials. Moreover, collision plane spectra of the three particles demonstrate that the momenta of the recoil ion and ionized electron are preferentially equal, and opposite, to each other. The electron spectra for double ionization show that the inclusion of the electron-electron interaction in the post-collision regime partitions the combined ionization momentum of the electrons so that the electrons are preferentially emitted in opposite azimuthal angles to one another. This is in contrast to calculations made assuming independent electrons.

  12. Observation of the competitive double-gamma nuclear decay.

    PubMed

    Walz, C; Scheit, H; Pietralla, N; Aumann, T; Lefol, R; Ponomarev, V Yu

    2015-10-15

    The double-gamma (γγ)-decay of a quantum system in an excited state is a fundamental second-order process of quantum electrodynamics. In contrast to the well-known single-gamma (γ)-decay, the γγ-decay is characterized by the simultaneous emission of two γ quanta, each with a continuous energy spectrum. In nuclear physics, this exotic decay mode has only been observed for transitions between states with spin-parity quantum numbers J(π) = 0(+) (refs 1-3). Single-gamma decays-the main experimental obstacle to observing the γγ-decay-are strictly forbidden for these 0(+) → 0(+) transitions. Here we report the observation of the γγ-decay of an excited nuclear state (J(π) = 11/2(-)) that is directly competing with an allowed γ-decay (to ground state J(π) = 3/2(+)). The branching ratio of the competitive γγ-decay of the 11/2(-) isomer of (137)Ba to the ground state relative to its single γ-decay was determined to be (2.05 ± 0.37) × 10(-6). From the measured angular correlation and the shape of the energy spectra of the individual γ-rays, the contributing combinations of multipolarities of the γ radiation were determined. Transition matrix elements calculated using the quasiparticle-phonon model reproduce our measurements well. The γγ-decay rate gives access to so far unexplored important nuclear structure information, such as the generalized (off-diagonal) nuclear electric polarizabilities and magnetic susceptibilities.

  13. Vanishing current hysteresis under competing nuclear spin pumping processes in a quadruplet spin-blockaded double quantum dot

    SciTech Connect

    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.

  14. Observation of hysteretic transport due to dynamic nuclear spin polarization in a GaAs lateral double quantum dot.

    PubMed

    Kobayashi, Takashi; Hitachi, Kenichi; Sasaki, Satoshi; Muraki, Koji

    2011-11-18

    We report a new transport feature in a GaAs lateral double quantum dot that emerges for magnetic-field sweeps and shows hysteresis due to dynamic nuclear spin polarization (DNP). This DNP signal appears in the Coulomb blockade regime by virtue of the finite interdot tunnel coupling and originates from the crossing between ground levels of the spin triplet and singlet extensively used for nuclear spin manipulations in pulsed-gate experiments. The magnetic-field dependence of the current level is suggestive of unbalanced DNP between the two dots, which opens up the possibility of controlling electron and nuclear spin states via dc transport.

  15. A simple double quantum coherence ESR sequence that minimizes nuclear modulations in Cu2+-ion based distance measurements

    NASA Astrophysics Data System (ADS)

    Ruthstein, Sharon; Ji, Ming; Shin, Byong-kyu; Saxena, Sunil

    2015-08-01

    Double quantum coherence (DQC) ESR is a sensitive method to measure magnetic dipolar interactions between spin labels. However, the DQC experiment on Cu2+ centers presents a challenge at X-band. The Cu2+ centers are usually coordinated to histidine residues in proteins. The electron-nuclear interaction between the Cu2+ ion and the remote nitrogen in the imidazole ring can interfere with the electron-electron dipolar interaction. Herein, we report on a modified DQC experiment that has the advantage of reduced contributions from electron-nuclear interactions, which enhances the resolution of the DQC signal to the electron-electron dipolar modulations. The modified pulse-sequence is verified on Cu2+-NO system in a polyalanine-based peptide and on a coupled Cu2+ system in a polyproline-based peptide. The modified DQC data were compared with the DEER data and good agreement was found.

  16. The Nuclear and Particle Physics of Neutrinoless Double Beta Decay

    NASA Astrophysics Data System (ADS)

    Haxton, Wick

    2014-03-01

    Fortuitous properties of nuclei allow us to isolate and study the rare second-order weak process of double beta decay. In particular, the decay channel in which a final state of two electrons and no neutrinos is produced - neutrinoless double beta decay - provides our best test of lepton number conservation and the Majorana mass of the electron neutrino. I will describe the connections between this process and the charge conjugation properties of the neutrino, including the possibility that the presence of both Dirac and Majorana masses accounts for the anomalous scale of neutrino masses. The extraordinary progress made over the past two decades has prepared the way for next-generation experiments that will probe Majorana masses at levels where nonzero rates may be found, given what we now know about neutrino mass splittings. I will describe some of the heroic efforts underway to develop detectors of unprecedented size, radiopurity, depth, and thus sensitivity. Work supported by the Office of Science, US DOE.

  17. Search for two-neutrino double electron capture on 124Xe with the XMASS-I detector

    NASA Astrophysics Data System (ADS)

    Abe, K.; Hiraide, K.; Ichimura, K.; Kishimoto, Y.; Kobayashi, K.; Kobayashi, M.; Moriyama, S.; Nakagawa, K.; Nakahata, M.; Norita, T.; Ogawa, H.; Sekiya, H.; Takachio, O.; Takeda, A.; Yamashita, M.; Yang, B. S.; Kim, N. Y.; Kim, Y. D.; Tasaka, S.; Liu, J.; Martens, K.; Suzuki, Y.; Fujita, R.; Hosokawa, K.; Miuchi, K.; Oka, N.; Onishi, Y.; Takeuchi, Y.; Kim, Y. H.; Lee, J. S.; Lee, K. B.; Lee, M. K.; Fukuda, Y.; Itow, Y.; Kegasa, R.; Kobayashi, K.; Masuda, K.; Takiya, H.; Uchida, H.; Nishijima, K.; Fujii, K.; Murayama, I.; Nakamura, S.

    2016-08-01

    Double electron capture is a rare nuclear decay process in which two orbital electrons are captured simultaneously in the same nucleus. Measurement of its two-neutrino mode would provide a new reference for the calculation of nuclear matrix elements whereas observation of its neutrinoless mode would demonstrate lepton number violation. A search for two-neutrino double electron capture on 124Xe is performed using 165.9 days of data collected with the XMASS-I liquid xenon detector. No significant excess above background was observed and we set a lower limit on the half-life as 4.7 ×1021 years at 90% confidence level. The obtained limit has ruled out parts of some theoretical expectations. We obtain a lower limit on the 126Xe two-neutrino double electron capture half-life of 4.3 ×1021 years at 90% confidence level as well.

  18. Electron-induced double ionization of oriented methane molecules

    NASA Astrophysics Data System (ADS)

    Oubaziz, Dahbia; Aitelhadjali, Zakia; Quinto, Michele Arcangelo; Boulifa, Rachida; Champion, Christophe

    2017-06-01

    We report here a theoretical study of the target orientation effect on the total cross sections for the double ionization of methane molecules impacted by electrons. The theoretical description is performed within the first Born approximation. The initial state of the collisional system is composed of an electron projectile modeled by a plane wave and a molecular target described by a one-center wave function while the final state is constituted by a scattered electron described by a plane wave and two ejected electrons both represented by a Coulomb wave and coupled with a Gamow factor. Secondary electron energetic distributions and total cross sections are reported for particular target configurations. Strong orientation effects on the double-ionization process are pointed out in particular when scrutinized orbital by orbital.

  19. Attosecond Electron Correlation Dynamics in Double Ionization of Benzene Probed with Two-Electron Angular Streaking

    NASA Astrophysics Data System (ADS)

    Winney, Alexander H.; Lee, Suk Kyoung; Lin, Yun Fei; Liao, Qing; Adhikari, Pradip; Basnayake, Gihan; Schlegel, H. Bernhard; Li, Wen

    2017-09-01

    With a novel three-dimensional electron-electron coincidence imaging technique and two-electron angular streaking method, we show that the emission time delay between two electrons can be measured from tens of attoseconds to more than 1 fs. Surprisingly, in benzene, the double ionization rate decays as the time delay between the first and second electron emission increases during the first 500 as. This is further supported by the decay of the Coulomb repulsion in the direction perpendicular to the laser polarization. This result reveals that laser-induced electron correlation plays a major role in strong field double ionization of benzene driven by a nearly circularly polarized field.

  20. SUPPRESSION OF ENERGETIC ELECTRON TRANSPORT IN FLARES BY DOUBLE LAYERS

    SciTech Connect

    Li, T. C.; Drake, J. F.; Swisdak, M.

    2012-09-20

    During flares and coronal mass ejections, energetic electrons from coronal sources typically have very long lifetimes compared to the transit times across the systems, suggesting confinement in the source region. Particle-in-cell simulations are carried out to explore the mechanisms of energetic electron transport from the corona to the chromosphere and possible confinement. We set up an initial system of pre-accelerated hot electrons in contact with ambient cold electrons along the local magnetic field and let it evolve over time. Suppression of transport by a nonlinear, highly localized electrostatic electric field (in the form of a double layer) is observed after a short phase of free-streaming by hot electrons. The double layer (DL) emerges at the contact of the two electron populations. It is driven by an ion-electron streaming instability due to the drift of the back-streaming return current electrons interacting with the ions. The DL grows over time and supports a significant drop in temperature and hence reduces heat flux between the two regions that is sustained for the duration of the simulation. This study shows that transport suppression begins when the energetic electrons start to propagate away from a coronal acceleration site. It also implies confinement of energetic electrons with kinetic energies less than the electrostatic energy of the DL for the DL lifetime, which is much longer than the electron transit time through the source region.

  1. Relativistic contributions to single and double core electron ionization energies of noble gases.

    PubMed

    Niskanen, J; Norman, P; Aksela, H; Agren, H

    2011-08-07

    We have performed relativistic calculations of single and double core 1s hole states of the noble gas atoms in order to explore the relativistic corrections and their additivity to the ionization potentials. Our study unravels the interplay of progression of relaxation, dominating in the single and double ionization potentials of the light elements, versus relativistic one-electron effects and quantum electrodynamic effects, which dominate toward the heavy end. The degree of direct relative additivity of the relativistic corrections for the single electron ionization potentials to the double electron ionization potentials is found to gradually improve toward the heavy elements. The Dirac-Coulomb Hamiltonian is found to predict a scaling ratio of ∼4 for the relaxation induced relativistic energies between double and single ionization. Z-scaling of the computed quantities were obtained by fitting to power law. The effects of nuclear size and form were also investigated and found to be small. The results indicate that accurate predictions of double core hole ionization potentials can now be made for elements across the full periodic table.

  2. Relativistic contributions to single and double core electron ionization energies of noble gases

    SciTech Connect

    Niskanen, J.; Norman, P.; Aksela, H.; Aagren, H.

    2011-08-07

    We have performed relativistic calculations of single and double core 1s hole states of the noble gas atoms in order to explore the relativistic corrections and their additivity to the ionization potentials. Our study unravels the interplay of progression of relaxation, dominating in the single and double ionization potentials of the light elements, versus relativistic one-electron effects and quantum electrodynamic effects, which dominate toward the heavy end. The degree of direct relative additivity of the relativistic corrections for the single electron ionization potentials to the double electron ionization potentials is found to gradually improve toward the heavy elements. The Dirac-Coulomb Hamiltonian is found to predict a scaling ratio of {approx}4 for the relaxation induced relativistic energies between double and single ionization. Z-scaling of the computed quantities were obtained by fitting to power law. The effects of nuclear size and form were also investigated and found to be small. The results indicate that accurate predictions of double core hole ionization potentials can now be made for elements across the full periodic table.

  3. Double-tuned single coil probe for nuclear magnetic resonance spectrometer

    SciTech Connect

    McKay, R.A.

    1984-05-01

    A double-tuned single coil probe for a nuclear magnetic resonance spectrometer having improved sensitivity is described comprising a double-tuned circuit means in which the low frequency irradiation is fed to a transmission line through an inductor means. The double-tuned circuit means of the invention may be remotely disposed from the magnetic field which results in greater sensitivity.

  4. Electron impact double ionization cross sections of light elements

    NASA Astrophysics Data System (ADS)

    Talukder, M. R.; Haque, A. K. F.; Uddin, M. A.

    2009-06-01

    A simple user-friendly semiempirical model is proposed to calculate electron impact double ionization cross sections of He, Li, Li+, B+, C+, C3+, O, O2+, O3+, Ne, Ne+, Ne2+, Na, Mg, Al3+, S, and Arq+ (q=0-7) targets for the incident electron energies from threshold to 106 eV. The contributions in the total double ionization cross sections from the direct double ionization and inner-shell ionization processes are taken into account on the basis of experimental data considered. The results of the present analysis are compared with the available experimental data and theoretical calculations. The model is found successful for the description of experimental cross sections. Since, this model may be a prudent selection to meet the demand level in plasma modeling due to its simple inherent structure.

  5. Attosecond electronic and nuclear quantum photodynamics of the ozone molecule

    SciTech Connect

    Halász, G. J.; Perveaux, A.; Lasorne, B.; Gatti, F.; Robb, M. A.; Vibók, Á.

    2013-11-13

    Coupled electron-nuclear dynamics simulations are investigated for the ozone molecule on the attosecond time scale. The initial wavepacket is pumped as a coherent superposition of two or three electronic states.

  6. Nuclear excitation by electronic transition of 235U

    DOE PAGES

    Chodash, P. A.; Norman, E. B.; Burke, J. T.; ...

    2016-03-11

    Here, nuclear excitation by electronic transition (NEET) is a rare nuclear excitation that can occur in isotopes containing a low-lying nuclear excited state. Over the past 40 yr, several experiments have attempted to measure NEET of 235U and those experiments have yielded conflicting results.

  7. TEM transmission line coil with double nuclear capability.

    PubMed

    Erickson, Matthew G; Kurpad, Krishna N; Holmes, James H; Fain, Sean B

    2007-10-01

    MR imaging and spectroscopy requires RF fields of high homogeneity. Quadrature volume coils meeting this requirement include the birdcage coil and the TEM resonator. We describe here a quadrature volume coil designed around a modified coaxial transmission line in which multiple inner conductors are arrayed on a circular perimeter and surrounded by a common shield. Current antinodes are established at appropriate points on the inner conductors by series transmission line stubs, either open circuit or short circuit, which terminate the line. Quadrature phasing is generated by a novel circuit constructed from a pair of high-performance current baluns and a commercial quadrature hybrid. The coil is a "pure" TEM coil as it is simply a resonant transmission line. There is no mode structure to consider. The construction of a prototype quadrature four-element coil is described and preliminary test results from this coil in a 4.7T horizontal bore magnet are reported. A related double nuclear coil design for (3)He and (1)H in which two linear transmission line coils are arrayed on a circular perimeter and simultaneously tuned and matched to their respective frequencies is also described. Preliminary tests from this coil in a 1.5T clinical scanner are reported.

  8. Nuclear-structure aspects of double beta decay

    SciTech Connect

    Suhonen, Jouni

    2010-11-24

    Neutrinoless double beta (0{nu}{beta}{beta}) decay of nuclei is a process that requires the neutrino to be a massive Majorana particle and thus cannot proceed in the standard model of electro-weak interactions. Recent results of the neutrino-oscillation experiments have produced accurate information on the mixing of neutrinos and their squared mass differences. The 0{nu}{beta}{beta} decay takes place in atomic nuclei where it can be observed, at least in principle, by underground neutrino experiments. The need of nuclei in observation of the 0{nu}{beta}{beta} decay bears two facets: The nucleus serves as laboratory for detection but at the same time its complicated many-nucleon structure interferes strongly with the analysis of the experimental data. The information about the weak-interaction observables, like the neutrino mass, has to be filtered from the data through the nuclear matrix elements (NMEs). Hence, exact knowledge about the NMEs is of paramount importance in the analysis of the data provided by the expensive and time-consuming underground experiments.

  9. Equivalent electron correlations in nonsequential double ionization of noble atoms

    NASA Astrophysics Data System (ADS)

    Dong, Shansi; Han, Qiujing; Zhang, Jingtao

    2017-02-01

    Electron correlation is encoded directly in the distribution of the energetic electrons produced in a recollision-impact double ionization process, and varies with the laser field and the target atoms. In order to get equivalent electron correlation effects, one should enlarge the laser intensity cubically and the laser frequency linearly in proportion to the second ionization potentials of the target atoms. The physical mechanism behind the transform is to keep the ponderomotive parameter unchanged when the laser frequency is enlarged. Project supported by the National Natural Science Foundation of China (Grant Nos. 61475168 and 11674231) and sponsored by Shanghai Gaofeng & Gaoyuan Project for University Academic Program Development (Zhang).

  10. Nonadiabatic Evolution of Electronic States by Electron Nuclear Dynamics Theory: Application to Atom-Molecule Scattering Problems.

    NASA Astrophysics Data System (ADS)

    Hagelberg, Frank

    2004-03-01

    In this contribution, we address the problem how to determine accurately the nonadiabatic content of any given dynamic process involving molecular motion. More specifically, we generate a dynamic electronic wave function using Electron Nuclear Dynamics (END) theory^2 and cast this wave function into the language of electronic excitations. This is achieved by adiabatic transport of an electronic basis along the classical nuclear trajectories of the studied molecular system. This basis is chosen as the static UHF molecular ground state determinant of the system in conjunction with all determinants that arise from the ground state by single, double and triple substitutions. Projecting the dynamic wave function into this basis, we arrive at a natural distinction between adiabatic and nonadiabatic components of the motion considered. We will discuss this concept by the examples of various scattering problems, among them the interaction of proton projectiles with methylene targets. ^2E. Deumens et al., Rev. Mod. Phys. 1994, 66, 917.

  11. Effects of hot electron inertia on electron-acoustic solitons and double layers

    SciTech Connect

    Verheest, Frank; Hellberg, Manfred A.

    2015-07-15

    The propagation of arbitrary amplitude electron-acoustic solitons and double layers is investigated in a plasma containing cold positive ions, cool adiabatic and hot isothermal electrons, with the retention of full inertial effects for all species. For analytical tractability, the resulting Sagdeev pseudopotential is expressed in terms of the hot electron density, rather than the electrostatic potential. The existence domains for Mach numbers and hot electron densities clearly show that both rarefactive and compressive solitons can exist. Soliton limitations come from the cool electron sonic point, followed by the hot electron sonic point, until a range of rarefactive double layers occurs. Increasing the relative cool electron density further yields a switch to compressive double layers, which ends when the model assumptions break down. These qualitative results are but little influenced by variations in compositional parameters. A comparison with a Boltzmann distribution for the hot electrons shows that only the cool electron sonic point limit remains, giving higher maximum Mach numbers but similar densities, and a restricted range in relative hot electron density before the model assumptions are exceeded. The Boltzmann distribution can reproduce neither the double layer solutions nor the switch in rarefactive/compressive character or negative/positive polarity.

  12. Conformation dependent electronic transport in a DNA double-helix

    SciTech Connect

    Kundu, Sourav Karmakar, S. N.

    2015-10-15

    We present a tight-binding study of conformation dependent electronic transport properties of DNA double-helix including its helical symmetry. We have studied the changes in the localization properties of DNA as we alter the number of stacked bases within every pitch of the double-helix keeping fixed the total number of nitrogen bases within the DNA molecule. We take three DNA sequences, two of them are periodic and one is random and observe that in all the cases localization length increases as we increase the radius of DNA double-helix i.e., number of nucleobases within a pitch. We have also investigated the effect of backbone energetic on the I-V response of the system and found that in presence of helical symmetry, depending on the interplay of conformal variation and disorder, DNA can be found in either metallic, semiconducting and insulating phases, as observed experimentally.

  13. Double deflection system for an electron beam device

    DOEpatents

    Parker, Norman W.; Golladay, Steven D.; Crewe, Albert V.

    1978-01-01

    A double deflection scanning system for electron beam instruments is provided embodying a means of correcting isotropic coma, and anisotropic coma aberrations induced by the magnetic lens of such an instrument. The scanning system deflects the beam prior to entry into the magnetic lens from the normal on-axis intersection of the beam with the lens according to predetermined formulas and thereby reduces the aberrations.

  14. Double differential cross sections for electron impact ionization of helium

    NASA Astrophysics Data System (ADS)

    Yun-fei, Yao; Zhang-jin, Chen

    1999-03-01

    The double differential cross sections for electron impact ionization of helium at incident energies of 200 eV, 100 eV and 64.6 eV have been calculated in the BBK model. The present results are found to be in generally good agreement with the latest measurements of Röder et al. and the theoretical results of the convergent close-coupling method although some quantitative discrepancy remains.

  15. Double-shot MeV electron diffraction and microscopy

    PubMed Central

    Musumeci, P.; Cesar, D.; Maxson, J.

    2017-01-01

    In this paper, we study by numerical simulations a time-resolved MeV electron scattering mode where two consecutive electron pulses are used to capture the evolution of a material sample on 10 ps time scales. The two electron pulses are generated by illuminating a photocathode in a radiofrequency photogun by two short laser pulses with adjustable delay. A streak camera/deflecting cavity is used after the sample to project the two electron bunches on two well separated regions of the detector screen. By using sufficiently short pulses, the 2D spatial information from each snapshot can be preserved. This “double-shot” technique enables the efficient capture of irreversible dynamics in both diffraction and imaging modes. In this work, we demonstrate both modes in start-to-end simulations of the UCLA Pegasus MeV microscope column. PMID:28612040

  16. Double-shot MeV electron diffraction and microscopy

    DOE PAGES

    Musumeci, P.; Cesar, D.; Maxson, J.

    2017-05-19

    Here in this paper, we study by numerical simulations a time-resolved MeV electron scattering mode where two consecutive electron pulses are used to capture the evolution of a material sample on 10 ps time scales. The two electron pulses are generated by illuminating a photocathode in a radiofrequency photogun by two short laser pulses with adjustable delay. A streak camera/deflecting cavity is used after the sample to project the two electron bunches on two well separated regions of the detector screen. By using sufficiently short pulses, the 2D spatial information from each snapshot can be preserved. This “double-shot” technique enablesmore » the efficient capture of irreversible dynamics in both diffraction and imaging modes. Finally, in this work, we demonstrate both modes in start-to-end simulations of the UCLA Pegasus MeV microscope column.« less

  17. Electron transport through nuclear pasta in magnetized neutron stars

    NASA Astrophysics Data System (ADS)

    Yakovlev, D. G.

    2015-10-01

    We present a simple model for electron transport in a possible layer of exotic nuclear clusters (in the so-called nuclear pasta layer) between the crust and liquid core of a strongly magnetized neutron star. The electron transport there can be strongly anisotropic and gyrotropic. The anisotropy is produced by different electron effective collision frequencies along and across local symmetry axis in domains of exotic ordered nuclear clusters and by complicated effects of the magnetic field. We also calculate averaged kinetic coefficients in case local domains are freely oriented. Possible applications of the obtained results and open problems are outlined.

  18. Electronic and Nuclear Factors in Charge and Excitation Transfer

    SciTech Connect

    Piotr Piotrowiak

    2004-09-28

    We report the and/or state of several subprojects of our DOE sponsored research on Electronic and Nuclear Factors in Electron and Excitation Transfer: (1) Construction of an ultrafast Ti:sapphire amplifier. (2) Mediation of electronic interactions in host-guest molecules. (3) Theoretical models of electrolytes in weakly polar media. (4) Symmetry effects in intramolecular excitation transfer.

  19. Singlet-triplet electron spin qubit in Si/SiGe double quantum dot

    NASA Astrophysics Data System (ADS)

    Wu, Xian

    In this thesis, we study the electronic properties of devices made from Si/SiGe heterostructures and demonstrate universal control of a two-electron spin qubit in a double quantum dot. First, we introduce the basic concepts of a quantum bit (qubit), which is the fundamental building block of a quantum computer. We choose to use electron spin states in a solid state device as the hardware for implementing a qubit. The solid state device is made in a Si/SiGe heterostructure, in which a two dimensional electron gas (2DEG) forms at the interface of a Si layer and a SiGe layer at cryogenic temperatures. Metal gates are patterned on top of the heterostrucutres to confine electrons in the two lateral directions. We characterize the material by fabricating Hall bars and performing magnetotransport measurements on those Hall bars to extract the carrier density and mobility of the 2DEG formed in each material. We study the surface effects of modulation doped heterostructures on the 2DEG formed underneath and demonstrate that the quality of the surface affects the property of the buried 2DEG in a Si/SiGe heterostructure. In a double quantum dot, the spin singlet state and the spin-zero triplet state of two electrons can be used as the qubit basis states. The energy difference between singlet and triplet states induces rotations about the Z axis in the Bloch sphere. The difference in magnetic field DeltaB between the two sides of the double dot, arising from the coupling to the nuclear spins in the host material, drives singlet-triplet state rotation about the X axis in the Blochsphere. X rotation is poor because this nuclear Delta B is unstable. We fabricate a Si/SiGe double quantum dot with an integrated micromagnet, which generates a larger and more stable Delta B to improve X rotation. Using this DeltaB, we demonstrate coherent rotation of the qubit's Bloch vector about two different axes of the Bloch sphere. The inhomogeneous spin coherence time T 2* is determined. We

  20. Isotensor Axial Polarizability and Lattice QCD Input for Nuclear Double-β Decay Phenomenology.

    PubMed

    Shanahan, Phiala E; Tiburzi, Brian C; Wagman, Michael L; Winter, Frank; Chang, Emmanuel; Davoudi, Zohreh; Detmold, William; Orginos, Kostas; Savage, Martin J

    2017-08-11

    The potential importance of short-distance nuclear effects in double-β decay is assessed using a lattice QCD calculation of the nn→pp transition and effective field theory methods. At the unphysical quark masses used in the numerical computation, these effects, encoded in the isotensor axial polarizability, are found to be of similar magnitude to the nuclear modification of the single axial current, which phenomenologically is the quenching of the axial charge used in nuclear many-body calculations. This finding suggests that nuclear models for neutrinoful and neutrinoless double-β decays should incorporate this previously neglected contribution if they are to provide reliable guidance for next-generation neutrinoless double-β decay searches. The prospects of constraining the isotensor axial polarizabilities of nuclei using lattice QCD input into nuclear many-body calculations are discussed.

  1. Isotensor Axial Polarizability and Lattice QCD Input for Nuclear Double-β Decay Phenomenology

    NASA Astrophysics Data System (ADS)

    Shanahan, Phiala E.; Tiburzi, Brian C.; Wagman, Michael L.; Winter, Frank; Chang, Emmanuel; Davoudi, Zohreh; Detmold, William; Orginos, Kostas; Savage, Martin J.; Nplqcd Collaboration

    2017-08-01

    The potential importance of short-distance nuclear effects in double-β decay is assessed using a lattice QCD calculation of the n n →p p transition and effective field theory methods. At the unphysical quark masses used in the numerical computation, these effects, encoded in the isotensor axial polarizability, are found to be of similar magnitude to the nuclear modification of the single axial current, which phenomenologically is the quenching of the axial charge used in nuclear many-body calculations. This finding suggests that nuclear models for neutrinoful and neutrinoless double-β decays should incorporate this previously neglected contribution if they are to provide reliable guidance for next-generation neutrinoless double-β decay searches. The prospects of constraining the isotensor axial polarizabilities of nuclei using lattice QCD input into nuclear many-body calculations are discussed.

  2. Coulomb-tail effect of electron-electron interaction on nonsequential double ionization

    NASA Astrophysics Data System (ADS)

    Zhou, Yueming; Huang, Cheng; Lu, Peixiang

    2011-08-01

    With the classical ensemble model, we investigate the manifestations of the Coulomb tail of electron-electron interaction in nonsequential double ionization by comparing the results from the short-range electron-electron interaction with those from the Coulombic electron-electron interaction. At the intensity below the recollision threshold, the two-electron momentum distributions in the direction parallel to the laser polarization show an anticorrelated behavior for the Coulombic electron-electron interaction while a correlated behavior for the short-range interaction, which indicates the responsibility of the Coulomb tail of the electron-electron interaction for the experimentally observed anticorrelated emission [Y. Liu, S. Tschuch, A. Rudenko, M. Durr, M. Siegel, U. Morgner, R. Moshammer, and J. Ullrich, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.101.053001 101, 053001 (2008)]. In the transverse direction, for the Coulombic electron-electron interaction, the two electrons exhibit no effect of repulsion at an intensity below the recollision threshold while a strong repulsion effect at an intensity above the threshold, which becomes weaker as the laser intensity further increases. Back analysis shows that the role of the Coulomb tail of electron-electron interaction leads asymmetric energy sharing (AES) to be prevalent at recollision. This AES results in the two electrons leaving the ion at different times or with different initial momenta, which is responsible for the anticorrelated behavior in the parallel direction and the intensity-dependent repulsion effect in the transverse direction.

  3. Coulomb-tail effect of electron-electron interaction on nonsequential double ionization

    SciTech Connect

    Zhou Yueming; Huang Cheng; Lu Peixiang

    2011-08-15

    With the classical ensemble model, we investigate the manifestations of the Coulomb tail of electron-electron interaction in nonsequential double ionization by comparing the results from the short-range electron-electron interaction with those from the Coulombic electron-electron interaction. At the intensity below the recollision threshold, the two-electron momentum distributions in the direction parallel to the laser polarization show an anticorrelated behavior for the Coulombic electron-electron interaction while a correlated behavior for the short-range interaction, which indicates the responsibility of the Coulomb tail of the electron-electron interaction for the experimentally observed anticorrelated emission [Y. Liu, S. Tschuch, A. Rudenko, M. Durr, M. Siegel, U. Morgner, R. Moshammer, and J. Ullrich, Phys. Rev. Lett. 101, 053001 (2008)]. In the transverse direction, for the Coulombic electron-electron interaction, the two electrons exhibit no effect of repulsion at an intensity below the recollision threshold while a strong repulsion effect at an intensity above the threshold, which becomes weaker as the laser intensity further increases. Back analysis shows that the role of the Coulomb tail of electron-electron interaction leads asymmetric energy sharing (AES) to be prevalent at recollision. This AES results in the two electrons leaving the ion at different times or with different initial momenta, which is responsible for the anticorrelated behavior in the parallel direction and the intensity-dependent repulsion effect in the transverse direction.

  4. Realizing double Dirac particles in the presence of electronic interactions

    NASA Astrophysics Data System (ADS)

    Di Sante, Domenico; Hausoel, Andreas; Barone, Paolo; Tomczak, Jan M.; Sangiovanni, Giorgio; Thomale, Ronny

    2017-09-01

    Double Dirac fermions have recently been identified as possible quasiparticles hosted by three-dimensional crystals with particular nonsymmorphic point-group symmetries. Applying a combined approach of a b initio methods and dynamical mean-field theory, we investigate how interactions and double Dirac band topology conspire to form the electronic quantum state of Bi2CuO4 . We derive a downfolded eight-band model of the pristine material at low energies around the Fermi level. By tuning the model parameters from the free band structure to the realistic strongly correlated regime, we find a persistence of the double Dirac dispersion until its constituting time-reversal symmetry is broken due to the onset of magnetic ordering at the Mott transition. Our calculations suggest that the double Dirac fermions in Bi2CuO4 can be restored by experimentally accessible hydrostatic pressures. In light of the growing attention to the topological quantum chemistry approach, our results on Bi2CuO4 show how many-body effects must be included beyond the static mean-field level for reliable predictions on new materials.

  5. Electron-Nuclear Spin Transfer in Triple Quantum Dot Networks

    NASA Astrophysics Data System (ADS)

    Prada, Marta; Toonen, Ryan; Harrison, Paul

    2005-03-01

    We investigate the conductance spectra of coupled quantum dots to study systematically the nuclear spin relaxation of delta- and y-junction networks and observe spin blockade dependence on the electronic configurations. We derive the conductance using the Beenakker approach generalised to an array of quantum dots where we consider the nuclear spin transfer to electrons by hyperfine coupling. This allows us to predict the relevant memory effects on the different electronic states by studying the evolution of the single electron resonances in presence of nuclear spin relaxation. We find that the gradual depolarisation of the nuclear system is imprinted in the conductance spectra of the multidot system. Our calculations of the temporal evolution of the conductance resonance reveal that spin blockade can be lifted by hyperfine coupling.

  6. Electron nuclear spin transfer in quantum-dot networks

    NASA Astrophysics Data System (ADS)

    Prada, M.; Toonen, R. C.; Blick, R. H.; Harrison, P.

    2005-05-01

    We investigate the conductance spectra of coupled quantum dots to study systematically the nuclear spin relaxation of different geometries of a two-dimensional network of quantum dots and observe spin blockade dependence on the electronic configurations. We derive the conductance using the Beenakker approach generalized to an array of quantum dots where we consider the nuclear spin transfer to electrons by hyperfine coupling. This allows us to predict the relevant memory effects on the different electronic states by studying the evolution of the single electron resonances in the presence of nuclear spin relaxation. We find that the gradual depolarization of the nuclear system is imprinted in the conductance spectra of the multidot system. Our calculations of the temporal evolution of the conductance resonance reveal that spin blockade can be lifted by hyperfine coupling.

  7. Search for two-neutrino double electron capture of 124Xe with XENON100

    NASA Astrophysics Data System (ADS)

    Aprile, E.; Aalbers, J.; Agostini, F.; Alfonsi, M.; Amaro, F. D.; Anthony, M.; Arneodo, F.; Barrow, P.; Baudis, L.; Bauermeister, B.; Benabderrahmane, M. L.; Berger, T.; Breur, P. A.; Brown, A.; Brown, E.; Bruenner, S.; Bruno, G.; Budnik, R.; Bütikofer, L.; Calvén, J.; Cardoso, J. M. R.; Cervantes, M.; Cichon, D.; Coderre, D.; Colijn, A. P.; Conrad, J.; Cussonneau, J. P.; Decowski, M. P.; de Perio, P.; di Gangi, P.; di Giovanni, A.; Diglio, S.; Duchovni, E.; Fei, J.; Ferella, A. D.; Fieguth, A.; Franco, D.; Fulgione, W.; Gallo Rosso, A.; Galloway, M.; Gao, F.; Garbini, M.; Geis, C.; Goetzke, L. W.; Greene, Z.; Grignon, C.; Hasterok, C.; Hogenbirk, E.; Itay, R.; Kaminsky, B.; Kessler, G.; Kish, A.; Landsman, H.; Lang, R. F.; Lellouch, D.; Levinson, L.; Le Calloch, M.; Levy, C.; Lin, Q.; Lindemann, S.; Lindner, M.; Lopes, J. A. M.; Manfredini, A.; Marrodán Undagoitia, T.; Masbou, J.; Massoli, F. V.; Masson, D.; Mayani, D.; Meng, Y.; Messina, M.; Micheneau, K.; Miguez, B.; Molinario, A.; Murra, M.; Naganoma, J.; Ni, K.; Oberlack, U.; Orrigo, S. E. A.; Pakarha, P.; Pelssers, B.; Persiani, R.; Piastra, F.; Pienaar, J.; Piro, M.-C.; Plante, G.; Priel, N.; Rauch, L.; Reichard, S.; Reuter, C.; Rizzo, A.; Rosendahl, S.; Rupp, N.; Dos Santos, J. M. F.; Sartorelli, G.; Scheibelhut, M.; Schindler, S.; Schreiner, J.; Schumann, M.; Scotto Lavina, L.; Selvi, M.; Shagin, P.; Silva, M.; Simgen, H.; Sivers, M. V.; Stein, A.; Thers, D.; Tiseni, A.; Trinchero, G.; Tunnell, C. D.; Wall, R.; Wang, H.; Weber, M.; Wei, Y.; Weinheimer, C.; Wulf, J.; Zhang, Y.; Xenon Collaboration

    2017-02-01

    Two-neutrino double electron capture is a rare nuclear decay where two electrons are simultaneously captured from the atomic shell. For 124Xe this process has not yet been observed and its detection would provide a new reference for nuclear matrix element calculations. We have conducted a search for two-neutrino double electron capture from the K shell of 124Xe using 7636 kg d of data from the XENON100 dark matter detector. Using a Bayesian analysis we observed no significant excess above background, leading to a lower 90% credibility limit on the half-life T1 /2>6.5 ×1020 yr. We have also evaluated the sensitivity of the XENON1T experiment, which is currently being commissioned, and found a sensitivity of T1 /2>6.1 ×1022 yr after an exposure of 2 t yr .

  8. Non-nuclear electron transport channels in hollow molecules

    NASA Astrophysics Data System (ADS)

    Zhao, Jin; Petek, Hrvoje

    2014-08-01

    Electron transport in inorganic semiconductors and metals occurs through delocalized bands formed by overlapping electron orbitals. Strong correlation of electronic wave functions with the ionic cores couples the electron and lattice motions, leading to efficient interaction and scattering that degrades coherent charge transport. By contrast, unoccupied electronic states at energies near the vacuum level with diffuse molecular orbitals may form nearly-free-electron bands with density maxima in non-nuclear interstitial voids, which are subject to weaker electron-phonon interaction. The position of such bands typically above the frontier orbitals, however, renders them unstable with respect to electronic interband relaxation and therefore unsuitable for charge transport. Through electronic-structure calculations, we engineer stable, non-nuclear, nearly-free-electron conduction channels in low-dimensional molecular materials by tailoring their electrostatic and polarization potentials. We propose quantum structures of graphane-derived Janus molecular sheets with spatially isolated conducting and insulating regions that potentially exhibit emergent electronic properties, as a paradigm for molecular-scale non-nuclear charge conductors; we also describe tuning of their electronic properties by application of external fields and calculate their electron-acoustic-phonon interaction.

  9. Simulating electron spin entanglement in a double quantum dot

    NASA Astrophysics Data System (ADS)

    Rodriguez-Moreno, M. A.; Hernandez de La Luz, A. D.; Meza-Montes, Lilia

    2011-03-01

    One of the biggest advantages of having a working quantum-computing device when compared with a classical one, is the exponential speedup of calculations. This exponential increase is based on the ability of a quantum system to create and operate on entangled states. In order to study theoretically the entanglement between two electron spins, we simulate the dynamics of two electron spins in an electrostatically-defined double quantum dot with a finite barrier height between the dots. Electrons are initially confined to separated quantum dots. Barrier height is varied and the spin entanglement as a function of this variation is investigated. The evolution of the system is simulated by using a numerical approach for solving the time-dependent Schrödinger equation for two particles. Partially supported by VIEP-BUAP.

  10. Double layers and solitary structures in electron-positron-ion plasma with Kappa distributed trapped electrons

    NASA Astrophysics Data System (ADS)

    Ali Shan, Shaukat; Imtiaz, Nadia

    2017-10-01

    The effect of electron trapping in an electron-positron-ion plasma is modeled with κ-distributed electrons. The trapped electron number density is truncated to some finite order of the electrostatic potential Φ. Small amplitude solitary structures with Sagdeev potential approach and reductive perturbation method (through Schamel equation) are found to be modified under the impact of superthermality index κ and trapping efficiency β. A modified Schamel equation which gives rise to the small amplitude double layers (SIADLs) is obtained. The role of various plasma parameters in particular, the superthermality index, the positron concentration, and the electron trapping efficiency on the small amplitude ion acoustic double layers (SIADLs) has been investigated. It can be inferred from this investigation that these parameters play modifying character in the formation of nonlinear structures like solitary waves and SIADLs in e-p-i plasma.

  11. Critical Nuclear Charge for Two-electron Atoms

    NASA Astrophysics Data System (ADS)

    Estienne, C. S.; Drake, G. W. F.

    2014-05-01

    There has been a recent revival of interest in the critical nuclear charge Zc that is just sufficient to bind a nucleus of charge Z and two electrons in the 1s21 S ground state. It is conjectured that the inverse of critical charge is related to the radius of convergence 1 /Z* for a 1 / Z expansion of the energy of the form E (Z) =Z2 (E0 +E1 / Z +E2 /Z2 + ⋯) . We have performed high precision variational calculations in Hylleraas coordinates, using the double basis set method, for values of Z very close to Zc, with basis sets containing up to 2809 terms (Ω = 24). Our preliminary result is Zc = 0 . 911 028 224 077 260 (15) , corresponding to 1 /Zc = 1 . 097 660 833 738 555 (18) . Well-defined eigenvalues continue to appear for Z

  12. Photon angular distribution and nuclear-state alignment in nuclear excitation by electron capture

    NASA Astrophysics Data System (ADS)

    Pálffy, Adriana; Harman, Zoltán; Surzhykov, Andrey; Jentschura, Ulrich D.

    2007-01-01

    The alignment of nuclear states resonantly formed in nuclear excitation by electron capture (NEEC) is studied by means of a density matrix technique. The vibrational excitations of the nucleus are described by a collective model and the electrons are treated in a relativistic framework. Formulas for the angular distribution of photons emitted in the nuclear relaxation are derived. We present numerical results for alignment parameters and photon angular distributions for a number of heavy elements in the case of E2 nuclear transitions. Our results are intended to help future experimental attempts to discern NEEC from radiative recombination, which is the dominant competing process.

  13. Multistability and spin diffusion enhanced lifetimes in dynamic nuclear polarization in a double quantum dot

    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.

  14. Near infrared organic photodetector utilizing a double electron blocking layer.

    PubMed

    Shafian, Shafidah; Hwang, Heewon; Kim, Kyungkon

    2016-10-31

    A near infrared organic photodiode (OPD) utilizing a double electron blocking layer (EBL) fabricated by the sequential deposition of molybdenum (VI) oxide (MoO3) and poly(3,4ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) is reported. The double EBL improves the on/off current ratio of OPD up to 1.36 x 104 at -1V, which is one order of magnitude higher than PEDOT:PSS single EBL (2.45 x 103) and three orders of magnitude higher than that of MoO3 single EBL (7.86). The detectivity at near infrared (800 nm) at -1V is 4.90 x 1011 Jones, which is 2.83 times higher than the PEDOT:PSS single EBL and 2 magnitudes higher compared to the MoO3 single EBL.

  15. Two-electron cusp in the double ionization of helium

    SciTech Connect

    Gulyas, L.; Sarkadi, L.; Igarashi, A.; Kirchner, T.

    2010-09-15

    We analyze the double ionization of He under the impact of 100 keV He{sup 2+} projectiles. The process is described within the framework of the impact parameter and frozen-correlation approximations where the one-electron events are treated by the continuum distorted wave method. Correlation between the emitted electrons, which plays an important role in forming the shape of the differential distribution of the electron emission, is described by the Coulomb density of states approximation (CDS). Special attention is paid to the region of the two-electron cusp that has been observed in a recent experiment for 100 keV He{sup 0}+He collisions [L. Sarkadi and A. Orban, Phys. Rev. Lett. 100, 133201 (2008)]. In the cusp region the correlated motion of the two electrons is influenced dominantly by the outgoing projectile, that is, the correlation function of the CDS treatment is expected to depend on the electron momenta measured relative to the projectile rather than to the target nucleus. A qualitative agreement with the experiment is achieved with a CDS model based on the use of such a projectile-centered correlation function that applies effective charges as given in the dynamically screened three-Coulomb wave function.

  16. Two-electron cusp in the double ionization of helium

    NASA Astrophysics Data System (ADS)

    Gulyás, L.; Sarkadi, L.; Igarashi, A.; Kirchner, T.

    2010-09-01

    We analyze the double ionization of He under the impact of 100 keV He2+ projectiles. The process is described within the framework of the impact parameter and frozen-correlation approximations where the one-electron events are treated by the continuum distorted wave method. Correlation between the emitted electrons, which plays an important role in forming the shape of the differential distribution of the electron emission, is described by the Coulomb density of states approximation (CDS). Special attention is paid to the region of the two-electron cusp that has been observed in a recent experiment for 100 keV He0+He collisions [L. Sarkadi and A. Orbán, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.100.133201 100, 133201 (2008)]. In the cusp region the correlated motion of the two electrons is influenced dominantly by the outgoing projectile, that is, the correlation function of the CDS treatment is expected to depend on the electron momenta measured relative to the projectile rather than to the target nucleus. A qualitative agreement with the experiment is achieved with a CDS model based on the use of such a projectile-centered correlation function that applies effective charges as given in the dynamically screened three-Coulomb wave function.

  17. Non-nuclear Electron Transport Channels in Hollow Molecules

    SciTech Connect

    Zhao, Jin; Petek, Hrvoje

    2014-08-15

    Electron transport in inorganic semiconductors and metals occurs through delocalized bands formed by overlapping electron orbitals. Strong correlation of electronic wave functions with the ionic cores couples the electron and lattice motions, leading to efficient interaction and scattering that degrades coherent charge transport. By contrast, unoccupied electronic states at energies near the vacuum level with diffuse molecular orbitals may form nearly-free-electron bands with density maxima in non-nuclear interstitial voids, which are subject to weaker electron-phonon interaction. The position of such bands typically above the frontier orbitals, however, renders them unstable with respect to electronic interband relaxation and therefore unsuitable for charge transport. Through electronic-structure calculations, we engineer stable, non-nuclear, nearly-free-electron conduction channels in low-dimensional molecular materials by tailoring their electrostatic and polarization potentials. We propose quantum structures of graphane-derived Janus molecular sheets with spatially isolated conducting and insulating regions that potentially exhibit emergent electronic properties, as a paradigm for molecular-scale non-nuclear charge conductors; we also describe tuning of their electronic properties by application of external fields and calculate their electron–acoustic-phonon interaction.

  18. Relations among several nuclear and electronic density functional reactivity indexes

    NASA Astrophysics Data System (ADS)

    Torrent-Sucarrat, Miquel; Luis, Josep M.; Duran, Miquel; Toro-Labbé, Alejandro; Solà, Miquel

    2003-11-01

    An expansion of the energy functional in terms of the total number of electrons and the normal coordinates within the canonical ensemble is presented. A comparison of this expansion with the expansion of the energy in terms of the total number of electrons and the external potential leads to new relations among common density functional reactivity descriptors. The formulas obtained provide explicit links between important quantities related to the chemical reactivity of a system. In particular, the relation between the nuclear and the electronic Fukui functions is recovered. The connection between the derivatives of the electronic energy and the nuclear repulsion energy with respect to the external potential offers a proof for the "Quantum Chemical le Chatelier Principle." Finally, the nuclear linear response function is defined and the relation of this function with the electronic linear response function is given.

  19. Nuclear excitation by electronic processes: NEEC and NEET effects

    NASA Astrophysics Data System (ADS)

    Morel, P.; Daugas, J. M.; Gosselin, G.; Méot, V.; Gogny, D.

    2004-12-01

    The nuclear excitation by electron capture (NEEC) and nuclear excitation by electronic transition (NEET), and related de-excitation, are two important electromagnetic processes to modify the nuclear state populations. In this paper, we present, on one hand, an experiment, accepted at GANIL (France) in September 2004, to measure the NEEC effect with a fully stripped 57Fe ion beam and, on the other hand, a complete calculation leading to the NEET rate of the first excited state of the 235U in a local thermodynamic equilibrium (LTE) plasma.

  20. Nuclear Excitation by Electronic Processes: NEEC and NEET Effects

    NASA Astrophysics Data System (ADS)

    Morel, P.; Daugas, J. M.; Gosselin, G.; Méot, V.; Gogny, D.

    2005-05-01

    The nuclear excitation by electron capture (NEEC) and nuclear excitation by electronic transition (NEET), and related de-excitation, are two important electromagnetic processes to modify the nuclear state populations. In this paper, we present, on one hand, an experiment accepted at GANIL (France) in September 2004 to measure the NEEC effect with a fully stripped 57Fe ion beam and, on the other hand, a complete calculation leading to the NEET rate of the first excited state of the 235U in a local thermodynamic equilibrium (LTE) plasma.

  1. Theory of nuclear excitation by electron capture for heavy ions

    NASA Astrophysics Data System (ADS)

    Pálffy, Adriana; Scheid, Werner; Harman, Zoltán

    2006-01-01

    We investigate the resonant process of nuclear excitation by electron capture (NEEC), in which a continuum electron is captured into a bound state of an ion with the simultaneous excitation of the nucleus. In order to derive the cross section a Feshbach projection operator formalism is introduced. Nuclear states and transitions are described by a nuclear collective model and making use of experimental data. Transition rates and total cross sections for NEEC followed by the radiative decay of the excited nucleus are calculated for various heavy-ion collision systems.

  2. Nuclear Excitation by Electronic Transition - NEET

    SciTech Connect

    Becker, J.A.

    2002-06-10

    Experiments seeking to demonstrate nuclear excitation induced by synchrotron radiation have been enabled by the development of intense synchrotron radiation. The phenomena has been demonstrated in {sup 197}Au, while realistic upper limits for {sup 189}Os have been established. A new experiment in {sup 189}Os is described. The experimental claim of NEET in isomeric {sup 178}Hf is not credible.

  3. Thomas double scattering in electron capture from oriented molecular hydrogen

    SciTech Connect

    Alston, S.; Brennan, T.; Bannon, F.

    1995-11-01

    Electron capture from hydrogen molecules by protons is treated using the second-order Born approximation. Differential cross sections in an adiabatic-nuclei approximation for specific molecular orientations and for an equally weighted averaging over all orientations are presented for incident energies of 2.5 and 10 MeV. A Hartree-Fock molecular wave function and linearized-propagator approximation are employed to evaluate the amplitude. An approximate factoring of the amplitude into double scattering and diffraction (arising from the two target nuclei) components is shown to give a poor description of high-velocity molecular capture.

  4. Electron flux in molecules induced by nuclear motion

    NASA Astrophysics Data System (ADS)

    Okuyama, Michihiro; Takatsuka, Kazuo

    2009-07-01

    As a general tool for analysis of chemical reactions from the view point of electron wavepacket dynamics, electron flux within a molecule is numerically realized in terms of physically time-dependent electronic wavefunctions given by the semiclassical Ehrenfest theory. These wavefunctions are synchronized with real time motion of molecular nuclei through the nuclear kinematic coupling (nonadiabatic elements). Since the standard quantum flux gives only a null field for a real-valued electronic eigenfunction, we extend the definition of flux such that the essential information of dynamical flow of electrons can be retrieved even from adiabatic electronic wavefunctions calculated in the scheme of the so-called ab initio molecular dynamics.

  5. Shigella flexneri Spa15 Crystal Structure Verified in Solution by Double Electron Electron Resonance

    PubMed Central

    Lillington, James E.D.; Lovett, Janet E.; Johnson, Steven; Roversi, Pietro; Timmel, Christiane R.; Lea, Susan M.

    2011-01-01

    Shigella flexneri Spa15 is a chaperone of the type 3 secretion system, which binds a number of effectors to ensure their stabilization prior to secretion. One of these effectors is IpgB1, a mimic of the human Ras-like Rho guanosine triphosphatase RhoG. In this study, Spa15 alone and in complex with IpgB1 has been studied by double electron electron resonance, an experiment that gives distance information showing the spacial separation of attached spin labels. This distance is explained by determining the crystal structure of the spin-labeled Spa15 where labels are seen to be buried in hydrophobic pockets. The double electron electron resonance experiment on the Spa15 complex with IpgB1 shows that IpgB1 does not bind Spa15 in the same way as is seen in the homologous Salmonella sp. chaperone:effector complex InvB:SipA. PMID:21075116

  6. Nuclear Magnetic Double Resonance Using Weak Perturbing RF Fields

    ERIC Educational Resources Information Center

    Reynolds, G. Fredric

    1977-01-01

    Describes a nuclear magnetic resonance experimental example of spin tickling; also discusses a direct approach for verifying the relative signs of coupling constants in three-spin cyclopropyl systems. (SL)

  7. Nuclear Magnetic Double Resonance Using Weak Perturbing RF Fields

    ERIC Educational Resources Information Center

    Reynolds, G. Fredric

    1977-01-01

    Describes a nuclear magnetic resonance experimental example of spin tickling; also discusses a direct approach for verifying the relative signs of coupling constants in three-spin cyclopropyl systems. (SL)

  8. Nuclear Magnetic Resonance Coupling Constants and Electronic Structure in Molecules.

    ERIC Educational Resources Information Center

    Venanzi, Thomas J.

    1982-01-01

    Theory of nuclear magnetic resonance spin-spin coupling constants and nature of the three types of coupling mechanisms contributing to the overall spin-spin coupling constant are reviewed, including carbon-carbon coupling (neither containing a lone pair of electrons) and carbon-nitrogen coupling (one containing a lone pair of electrons).…

  9. Nuclear Magnetic Resonance Coupling Constants and Electronic Structure in Molecules.

    ERIC Educational Resources Information Center

    Venanzi, Thomas J.

    1982-01-01

    Theory of nuclear magnetic resonance spin-spin coupling constants and nature of the three types of coupling mechanisms contributing to the overall spin-spin coupling constant are reviewed, including carbon-carbon coupling (neither containing a lone pair of electrons) and carbon-nitrogen coupling (one containing a lone pair of electrons).…

  10. High-resolution observation by double-biprism electron holography

    SciTech Connect

    Harada, Ken; Tonomura, Akira; Matsuda, Tsuyoshi; Akashi, Tetsuya; Togawa, Yoshihiko

    2004-12-01

    High-resolution electron holography has been achieved by using a double-biprism interferometer implemented on a 1 MV field emission electron microscope. The interferometer was installed behind the first magnifying lens to narrow carrier fringes and thus enabled complete separation of sideband Fourier spectrum from center band in reconstruction process. Holograms of Au fine particles and single-crystalline thin films with the finest fringe spacing of 4.2 pm were recorded and reconstructed. The overall holography system including the reconstruction process performed well for holograms in which carrier fringes had a spacing of around 10 pm. High-resolution lattice images of the amplitude and phase were clearly reconstructed without mixing of the center band and sideband information. Additionally, entire holograms were recorded without Fresnel fringes normally generated by the filament electrode of the biprism, and the holograms were thus reconstructed without the artifacts caused by Fresnel fringes.

  11. Electronic transport in double-strand DNA segments

    NASA Astrophysics Data System (ADS)

    Albuquerque, E. L.; Mauriz, P. W.; Moreira, D. A.

    2008-03-01

    We report in this work a numerical study of the electronic density of states in π-stacked arrays of DNA double-strand segments made up from the nucleotides guanine G, adenine A, cytosine C and thymine T. In order to reveal the relevance of the underlying correlations in the nucleotides distribution, we compare the results for a genomic DNA sequence, considering a segment of the first sequenced human chromosome 22 (Ch 22), with those of two artificial sequences forming a Rudin-Shapiro (RS) as well as a Fibonacci (FB) polyGC quasiperiodic sequences. Our theoretical method uses an electronic tight-binding Hamiltonian suitable to describe the DNA segments modeled by the quasiperiodic chains.

  12. Electron-electron double resonance in electron spin echo: Model biradical systems and the sensitized photolysis of decalin

    NASA Astrophysics Data System (ADS)

    Milov, A. D.; Ponomarev, A. B.; Tsvetkov, Yu. D.

    1984-09-01

    Model systems, comprising frozen glassy solutions of stabilized radicals and biradicals of the nitroxyl type, have been used to test the applicability of electron-electron double resonance in electron spin echo (ELDOR ESE) in studies of the spatial distributions of free radicals arranged in groups in solids. The method was used to investigate the spatial distribution of alkyl radicals generated by the sensitized photolysis of glassy naphthalene solutions in decalin at 77 K. and detected radical pairs.

  13. Dissipative electronic transport through double quantum dots irradiated with microwaves

    NASA Astrophysics Data System (ADS)

    Brandes, Tobias; Aguado, Ramon; Platero, Gloria

    2003-03-01

    Double quantum dots in the strong Coulomb blockade regime are realizations of two-level systems defined from two tunnel--splitted ground states, which are separated by a large energy gap from the remaining many--particle states. The interactions between electrons and bosonic degrees of freedom (photons, phonons) in these systems can be tested and manipulated in electronic transport experiments [1]. Monochromatic classical radiation (AC fields, microwaves) gives rise to various non-linear effects such as photo-sidebands or dynamical localization (coherent supression of tunneling) that show up in the time-averaged, stationary electronic current [2]. On the other hand, quantum noise of a dissipative environment strongly influences the transport properties of coupled quantum dots [3,4]. In this contribution, we quantitatively investigate the combined influence of a classical, monochromatic time-dependent AC field and a dissipative boson environment on the non-linear transport through a double quantum dot. We develop a Floquet-like theory [5] that takes into account the effect of the electron reservoirs (leads) and can be numerically evaluated for arbitrary strong AC fields and arbitrary boson environment. In limiting cases we reproduce previous analytical results (polaron tunneling, Tien-Gordon formula). [1] T. Fujisawa, T. H. Oosterkamp, W. G. van der Wiel, B. W. Broer, R. Aguado, S. Tarucha, and L. P. Kouwenhoven, Science 282, 932 (1998); R. H. Blick, D. Pfannkuche, R. J. Haug, K. v. Klitzing, and K. Eberl, Phys. Rev. Lett. 80, 4032 (1998). [2] T. H. Stoof, Yu. V. Nazarov, Phys. Rev. B 53, 1050 (1996). [3] T. Brandes, B. Kramer, Phys. Rev. Lett. 83, 3021 (1999); T. Brandes, F. Renzoni, R. H. Blick, Phys. Rev. B 64, 035319 (2001); T. Brandes, T. Vorrath, Phys. Rev. B 66, 075341 (2002). [4] R. Aguado and L. P. Kouwenhoven, Phys. Rev. Lett, 84, 1986 (2000). [5] M. Grifoni, P. Hänggi, Phys. Rep. 304, 229 (1998).

  14. Precision Measurement of Nuclear Electron Capture Decay

    NASA Astrophysics Data System (ADS)

    Koltick, David; Liu, Shih-Chieh; Wang, Haoyu; Heim, Jordan; Nistor, Jonathan

    2017-01-01

    The method of accurately measuring the radioactive decay constant of a isotope by measuring the decay rate as a function of time requires that both the detector and environment be stable over time periods comparable to the life-time of the isotope. In addition statistical accuracy requires initial counting rates be high but limited by the dead time capability of the data collection system and the detectors double-event resolving time. A High Purity Germanium (HPGe) spectrometer, sensitive to radiation from 3-KeV to over 3-MeV, has been built to measure radioactive decay constants to a level of 10-5 10-6 at a location only 6 meters from the core of the High Flux Isotope Reactor located at Oak Ridge National Laboratory. Such accuracy requires understanding of, background, signal-processing algorithms, and both the double and triple event pile-up in the observed spectrum. The approach taken is to fit the collected energy spectrum with invariant shapes, independent of event rate. By fixing the source-detector geometry and environmental conditions, the invariant shapes are (1) ideal energy spectrum without pile-up and background, (2) the ideal double event pile-up spectrum, (3) the ideal triple event pile-up spectrum, and (4) the stable background spectrum. A method is presented that finds these ideal shapes using the collected data in situ. Taking this approach the HPGe detector photopeak shape in the absence of background and pile-up is presented showing associated structure over a range of 7 orders of magnitude.

  15. Consequences of nuclear electron capture in core collapse supernovae.

    PubMed

    Hix, W R; Messer, O E B; Mezzacappa, A; Liebendörfer, M; Sampaio, J; Langanke, K; Dean, D J; Martínez-Pinedo, G

    2003-11-14

    The most important weak nuclear interaction to the dynamics of stellar core collapse is electron capture, primarily on nuclei with masses larger than 60. In prior simulations of core collapse, electron capture on these nuclei has been treated in a highly parametrized fashion, if not ignored. With realistic treatment of electron capture on heavy nuclei come significant changes in the hydrodynamics of core collapse and bounce. We discuss these as well as the ramifications for the postbounce evolution in core collapse supernovae.

  16. A model for electron nuclear dynamics of a monatomic chain

    NASA Astrophysics Data System (ADS)

    Calais, Jean-Louis; Deumens, Erik; Ohrn, Yngve

    1994-05-01

    The Electron Nuclear Dynamics (END) approach is developed for a linear chain in a parametrized model inspired by the PPP (Pariser-Parr-Pople) model. Particular attention is given to the model parameters, and the choice of basis functions in this time-dependent theory. The resulting equations of motion include electronic-vibrational couplings. Explicit analysis of the simplest model leads to coupling between the highest frequency longitudinal vibrational mode and the electrons.

  17. A model for electron nuclear dynamics of a monatomic chain

    NASA Astrophysics Data System (ADS)

    Calais, Jean-Louis; Deumens, Erik; Öhrn, Yngve

    1994-09-01

    The electron nuclear dynamics (END) approach is developed for a linear chain in a parametrized model inspired by the PPP (Pariser-Parr-Pople) model. Particular attention is given to the model parameters, and the choice of basis functions in this time-dependent theory. The resulting equations of motion include electronic-vibrational couplings. Explicit analysis of the simplest model leads to coupling between the highest frequency longitudinal vibrational mode and the electrons.

  18. Monolithic electronics for nuclear and high-energy physics experiments

    SciTech Connect

    Young, G.R.

    1994-12-31

    Electronic instrumentation for large fixed-target and collider experiments is rapidly moving to the use of highly integrated electronics wherever it is cost effective. This trend is aided by the development of circuit building blocks useful for nuclear and high-energy physics instrumentation and has accelerated recently with the development of monolithic silicon chips with multiple functions on one substrate. Examples of recent developments are given, together with remarks on the rationale for use of monolithic electronics and economic considerations.

  19. Electronic and Magnetic Properties of Double Perovskites and Oxide Interfaces

    NASA Astrophysics Data System (ADS)

    Erten, Onur

    Transition metal oxides exhibit a wide range of fascinating phenomena ranging from high Tc superconductivity to colossal magnetoresistance. In this thesis, we examine the novel electronic and magnetic properties of double perovskites and oxide interfaces. First we focus on Sr2FeMoO6 which has a half-metallic ground state and a ferrimagnetic Tc=420 K, well above the room temperature. There are very few half-metals in nature and along with its high Tc, Sr2FeMoO6 has enormous potential in spintronics applications. We develop a minimal model that couples the conduction electrons on Mo (4d1) to the core spins of Fe (3d5). Delocalization of conduction electrons and maximizing the kinetic energy drives the long-range magnetic order. "Integrating out" the conduction electrons, we derive a new effective Hamiltonian, H eff, only for the localized spins. Heff is unique to double perovskites, and with its peculiar double square root form, it is different from standard Heisenberg or Anderson-Hasegawa Hamiltonians. Using Heff, we perform the first 3D, finite temperature calculations of double perovskites, going well beyond previous mean field or small cluster calculations. Next we consider Sr2CrOsO6 which has the highest Tc among all perovskites with a net moment. Its insulating behavior is puzzling given that Cr and Os are in the 3d3 and 5d3 configurations, half filled in t2g orbitals. The net moment at low temperature is M(0)=0.75 muB and non-monotonic magnetization as a function of temperature are quite unusual. To address these questions, we organize the problem through the hierarchy of its energy scales. To deal with the highest energy scale, the charge sector, we develop a multi-band Hubbard model that has different on-site Coulomb correlations on the Cr and Os sites. We solve this model using slave-rotor mean field theory which captures the essentials of the metal-Mott insulator transition and goes well beyond Hartree-Fock. We find a new criterion for the Mott transition

  20. Double quantum coherence electron spin resonance on coupled Cu(II)-Cu(II) electron spins

    NASA Astrophysics Data System (ADS)

    Becker, James S.; Saxena, Sunil

    2005-10-01

    We demonstrate for the first time the ability to generate double quantum coherences (DQCs) for the case of Cu(II). We show that small splittings (˜7 MHz) from the Cu(II)-Cu(II) electron-electron magnetic dipolar interaction can be reliably resolved even though the inhomogeneously broadened Cu(II) linewidth is ˜2 GHz. A Cu(II)-Cu(II) distance of 2.0 nm was measured on a model peptide system, thus, demonstrating that distances on the nanometer scale may be measured using DQC electron spin resonance (ESR).

  1. Cavity Born-Oppenheimer Approximation for Correlated Electron-Nuclear-Photon Systems.

    PubMed

    Flick, Johannes; Appel, Heiko; Ruggenthaler, Michael; Rubio, Angel

    2017-03-09

    In this work, we illustrate the recently introduced concept of the cavity Born-Oppenheimer approximation for correlated electron-nuclear-photon problems in detail. We demonstrate how an expansion in terms of conditional electronic and photon-nuclear wave functions accurately describes eigenstates of strongly correlated light-matter systems. For a GaAs quantum ring model in resonance with a photon mode we highlight how the ground-state electronic potential-energy surface changes the usual harmonic potential of the free photon mode to a dressed mode with a double-well structure. This change is accompanied by a splitting of the electronic ground-state density. For a model where the photon mode is in resonance with a vibrational transition, we observe in the excited-state electronic potential-energy surface a splitting from a single minimum to a double minimum. Furthermore, for a time-dependent setup, we show how the dynamics in correlated light-matter systems can be understood in terms of population transfer between potential energy surfaces. This work at the interface of quantum chemistry and quantum optics paves the way for the full ab-initio description of matter-photon systems.

  2. Electron backscatter diffraction: applications for nuclear materials.

    PubMed

    Medevielle; Hugon; Dugne

    1999-09-01

    The diffraction of electrons was first observed in 1928 by Kikuchi. The phenomenon results in the formation of characteristic diagrams of the crystalline lattice and the orientation of the phase. Backscattered electrons are diffracted by the different crystallographic planes (hkl) according to the Bragg angle thetab. These describe, by symmetry, two cones of axes normal to the diffracting plane. Information is collected on a phosphor screen, leading to the acquisition of a diffraction pattern called a Kikuchi diagram. Several improvements now give a wide range of applications such as phase identification (carbides or complex compounds in a (U,Zr,O) structure), analysis of materials interfaces (ZrO2/UO2), as well as solidification studies and local texture determination (molybdenum sheets). In these applications, EBSD, as a type of quantitative metallography, is a powerful tool.

  3. Double β-decay nuclear matrix elements for the A=48 and A=58 systems

    NASA Astrophysics Data System (ADS)

    Skouras, L. D.; Vergados, J. D.

    1983-11-01

    The nuclear matrix elements entering the double β decays of the 48Ca-48Ti and 58Ni-58Fe systems have been calculated using a realistic two nucleon interaction and realistic shell model spaces. Effective transition operators corresponding to a variety of gauge theory models have been considered. The stability of such matrix elements against variations of the nuclear parameters is examined. Appropriate lepton violating parameters are extracted from the A=48 data and predictions are made for the lifetimes of the positron decays of the A=58 system. RADIOACTIVITY Double β decay. Gauge theories. Lepton nonconservation. Neutrino mass. Shell model calculations.

  4. Electron capture branching ratio measurements in an ion trap for double beta decay experiments at TITAN

    NASA Astrophysics Data System (ADS)

    Brunner, T.; Brodeur, M.; Champagne, C.; Frekers, D.; Krücken, R.; Lapierre, A.; Delheij, P.; Ringle, R.; Ryjkov, V.; Smith, M.; Tanihata, I.; Dilling, J.

    2008-10-01

    Double beta decay (ββ) is a nuclear decay mode expected to appear in at least two varieties, the double-neutrino (2ν) and the zero-neutrino (0ν) mode. The 0νββ-decay is of particular interest as it requires the neutrino to be a Majorana particle. The search for such a decay is presently being carried out or planned in a number of experiments, such as EXO, MAJORANA, GERDA, CUORE, COBRA, NEMO-III and SNO+. The 0ν-decay rate depends on the neutrino mass but, unfortunately, also on a rather complex nuclear matrix element, making the extraction of the mass heavily dependent on the underlying theoretical nuclear model. However, all theoretical models can readily be tested against the 2ν mode, which, unlike its 0ν counterpart, only involves simple Gamow Teller nuclear matrix elements. These elements can be determined experimentally either through charge-exchange reactions or, for the ground-state transition, through the electron capture (EC) or single β-decay of the intermediate odd odd nucleus. The present program is geared towards the measurement of the EC branching ratios (BR). In most cases, these ratios are poorly known or not known at all, because EC is usually suppressed by several orders of magnitude compared to the β-decay counterpart due to energy considerations. Traditional methods for measuring these ratios have so far suffered from overwhelming background generated by these high-energy electrons. Recently, a unique background-free method for measuring EC branching ratios was proposed using the TITAN ion trap at the TRIUMF ISAC (Isotope Separator and ACcelerator) radioactive beam facility. The measurements will make use of the EBIT (Electron Beam Ion Trap) operating in Penning mode where electrons from the β--decay will be confined by the magnetic field. K-shell X-rays from EC will be detected by seven X-ray detectors located around the trap, thus providing orders of magnitude background suppression and thus ideal low-BR measurement environment.

  5. Electronic and nuclear flux densities in the H2 molecule

    NASA Astrophysics Data System (ADS)

    Hermann, G.; Paulus, B.; Pérez-Torres, J. F.; Pohl, V.

    2014-05-01

    We present a theoretical study of the electronic and nuclear flux densities of a vibrating H2 molecule after an electronic excitation by a short femtosecond laser pulse. The final state, a coherent superposition of the electronic ground state X1Σg+ and the electronic excited state B1Σu+, evolves freely and permits the partition of the electronic flux density into two competing fluxes: the adiabatic and the transition flux density. The nature of the two fluxes allows us to identify two alternating dynamics of the electronic motion, occurring on the attosecond and the femtosecond time scales. In contradistinction to the adiabatic electronic flux density, the transition electronic flux density shows a dependence on the carrier-envelope phase of the laser field, encoding information of the interaction of the electrons with the electric field. Furthermore, the nuclear flux density displays multiple reversals, a quantum effect recently discovered by Manz et al. [J. Manz, J. F. Pérez-Torres, and Y. Yang, Phys. Rev. Lett. 111, 153004 (2013), 10.1103/PhysRevLett.111.153004], calling for investigation of the electronic flux density.

  6. Double asymptotic expansion of three-center electronic repulsion integrals

    NASA Astrophysics Data System (ADS)

    Alvarez-Ibarra, A.; Köster, A. M.

    2013-07-01

    A double asymptotic expansion for the evaluation of three-center electron repulsion integrals (ERIs) in the long-range limit is presented. For the definition of this limit, a natural division of space based on the atomic coordinates and basis function exponents in utilized. The resulting analytical expression for the calculation of three-center ERIs in the long-range limit are implemented in the density functional theory program deMon2k. Validation and benchmark calculations of n-alkanes, hydrogen saturated graphene sheets and hydrogen saturated diamond blocks are discussed. It is shown that for a sufficient large number of long-range ERIs, the linear scaling regime is reached.

  7. Frustrated double ionization in two-electron triatomic molecules

    NASA Astrophysics Data System (ADS)

    Chen, A.; Price, H.; Staudte, A.; Emmanouilidou, A.

    2016-10-01

    Using a semiclassical model, we investigate frustrated double ionization (FDI) in D3+ , a two-electron triatomic molecule, when driven by an intense, linearly polarized, near-infrared (800 nm) laser field. We compute the kinetic energy release of the nuclei and find a good agreement between experiment and our model. We explore the two pathways of FDI and show that, with increasing field strength, over-the-barrier ionization overtakes tunnel ionization as the underlying mechanism of FDI. Moreover, we compute the angular distribution of the ion fragments for FDI and identify a feature that can potentially be observed experimentally and is a signature of only one of the two pathways of FDI.

  8. Visualization of Distance Distribution from Pulsed Double Electron-Electron Resonance Data

    SciTech Connect

    Bowman, Michael K.; Maryasov, Alexander G.; Kim, Nak-Kyoon; DeRose, Victoria J.

    2004-01-01

    Double electron-electron resonance (DEER), also known as pulsed electron-electron double resonance (PELDOR), is a time-domain electron paramagnetic resonance method that can measure the weak dipole-dipole interactions between unpaired electrons. DEER has been applied to discrete pairs of free radicals in biological macromolecules and to clusters containing small numbers of free radicals in polymers and irradiated materials. The goal of such work is to determine the distance or distribution of distances between radicals, which is an underdetermined problem. That is, the spectrum of dipolar interactions can be readily calculated for any distribution of free radicals, but there are many, quite different distributions of radicals that could produce the same experimental dipolar spectrum. This paper describes two methods that are useful for approximating the distance distributions for the large subset of cases in which the mutual orientations of the free radicals are uncorrelated and the width of the distribution is more than a few percent of its mean. The first method relies on a coordinate transformation and is parameter free, while the second is based on iterative least-squares with Tikhonov regularization. Both methods are useful in DEER studies of spin labeled biomolecules containing more than two labels.

  9. Molecular interferometer to decode attosecond electron-nuclear dynamics.

    PubMed

    Palacios, Alicia; González-Castrillo, Alberto; Martín, Fernando

    2014-03-18

    Understanding the coupled electronic and nuclear dynamics in molecules by using pump-probe schemes requires not only the use of short enough laser pulses but also wavelengths and intensities that do not modify the intrinsic behavior of the system. In this respect, extreme UV pulses of few-femtosecond and attosecond durations have been recognized as the ideal tool because their short wavelengths ensure a negligible distortion of the molecular potential. In this work, we propose the use of two twin extreme UV pulses to create a molecular interferometer from direct and sequential two-photon ionization processes that leave the molecule in the same final state. We theoretically demonstrate that such a scheme allows for a complete identification of both electronic and nuclear phases in the wave packet generated by the pump pulse. We also show that although total ionization yields reveal entangled electronic and nuclear dynamics in the bound states, doubly differential yields (differential in both electronic and nuclear energies) exhibit in addition the dynamics of autoionization, i.e., of electron correlation in the ionization continuum. Visualization of such dynamics is possible by varying the time delay between the pump and the probe pulses.

  10. Collective π -electronic excitations in BN double-walled nanotubes

    NASA Astrophysics Data System (ADS)

    Margulis, Vl. A.; Muryumin, E. E.; Gaiduk, E. A.

    2008-07-01

    We report a systematic theoretical study of the collective π -electronic excitations in boron nitride double-walled nanotubes (BN-DWNTs). For simplicity, it is assumed that both shells (inner and outer) of such tubes have a zigzag achiral structure. Taking into account intershell Coulomb coupling and neglecting intershell electron tunneling, we introduce the effective dynamic-dielectric-response function of the BN-DWNTs, which depends on frequency ω , wave number q , and angular momentum L . An explicit expression for this function is derived within the random-phase approximation using standard many-body techniques based on the Green’s function method. Numerical results are presented for the wave-number dispersion and damping of the π -plasmon modes with different L ’s, demonstrating a unified picture of the π -plasmon-energy variation with q for the BN-DWNTs of different diameters. According to this picture, the spectrum of the π plasmons, which are shown to be long lived and hence well-defined collective electronic excitations in the BN-DWNTs, consists of a set of nonintersecting upward-dispersed branches, which are well separated in their energies at small values of q , but which tend to merge with increasing q . Each of the branches corresponds to one and only one value of the angular momentum L=0,1,2,… and none of the branches starts from q=0 . The present calculations also show that the π plasmons in the BN-DWNTs can exist even at those q values at which the π -plasmon modes are not supported by either of the nanotube shells alone. It is found that the threshold value of the wavelength, at which the L=0 π -plasmon dispersion curve in the BN-DWNTs makes its start, is redshifted as compared to that in the inner and outer nanotube shells if they are considered separately. The most important features of our calculated results seem to be consistent, more or less reasonable, with those derived from the recent electron

  11. Recent searches for double-electron capture of nuclei to excited states

    SciTech Connect

    Povinec, P. P.; Frekers, D.; Šimkovic, F.

    2015-10-28

    Double electron capture has been of interest of many theoretical and experimental works as a possible extension of double beta-decay investigations. The neutrinoless double-electron capture, similarly as the neutrinoless double beta-decay may help to clarify if neutrinos are Majorana or Dirac particles. Results obtained in several double electron capture experiments are reviewed and new experiments to be carried out in deep underground laboratories using enriched sources and multidimensional HPGe-HPGe gamma-ray spectrometry with a few years of counting time are proposed, which should be able to improve half-lives limits by at least an order of magnitude.

  12. Energy and angular distributions of electrons emitted by direct double auger decay.

    PubMed

    Viefhaus, Jens; Cvejanović, Slobodan; Langer, Burkhard; Lischke, Toralf; Prümper, Georg; Rolles, Daniel; Golovin, Alexander V; Grum-Grzhimailo, Alexei N; Kabachnik, Nikolai M; Becker, Uwe

    2004-02-27

    We have observed the direct L(2,3)MMM double Auger transition after photoionization of the 2p shell of argon by angle-resolved electron-electron coincidence spectroscopy. The process is responsible for about 20% of the observed Auger electron intensity. In contrast to the normal Auger lines, the spectra in double Auger decay show a continuous intensity distribution. The energy and angular distributions of the emitted electrons allow one to obtain information on the electron correlations giving rise to the double Auger process as well as the symmetry of the associated two-electron continuum state.

  13. Electron transport in coupled double quantum wells and wires

    SciTech Connect

    Harff, N.E.; Simmons, J.A.; Lyo, S.K.

    1997-04-01

    Due to inter-quantum well tunneling, coupled double quantum wells (DQWs) contain an extra degree of electronic freedom in the growth direction, giving rise to new transport phenomena not found in single electron layers. This report describes work done on coupled DQWs subject to inplane magnetic fields B{sub {parallel}}, and is based on the lead author`s doctoral thesis, successfully defended at Oregon State University on March 4, 1997. First, the conductance of closely coupled DQWs in B{sub {parallel}} is studied. B{sub {parallel}}-induced distortions in the dispersion, the density of states, and the Fermi surface are described both theoretically and experimentally, with particular attention paid to the dispersion anticrossing and resulting partial energy gap. Measurements of giant distortions in the effective mass are found to agree with theoretical calculations. Second, the Landau level spectra of coupled DQWs in tilted magnetic fields is studied. The magnetoresistance oscillations show complex beating as Landau levels from the two Fermi surface components cross the Fermi level. A third set of oscillations resulting from magnetic breakdown is observed. A semiclassical calculation of the Landau level spectra is then performed, and shown to agree exceptionally well with the data. Finally, quantum wires and quantum point contacts formed in DQW structures are investigated. Anticrossings of the one-dimensional DQW dispersion curves are predicted to have interesting transport effects in these devices. Difficulties in sample fabrication have to date prevented experimental verification. However, recently developed techniques to overcome these difficulties are described.

  14. Status and future of nuclear matrix elements for neutrinoless double-beta decay: a review

    NASA Astrophysics Data System (ADS)

    Engel, Jonathan; Menéndez, Javier

    2017-04-01

    The nuclear matrix elements that govern the rate of neutrinoless double beta decay must be accurately calculated if experiments are to reach their full potential. Theorists have been working on the problem for a long time but have recently stepped up their efforts as ton-scale experiments have begun to look feasible. Here we review past and recent work on the matrix elements in a wide variety of nuclear models and discuss work that will be done in the near future. Ab initio nuclear-structure theory, which is developing rapidly, holds out hope of more accurate matrix elements with quantifiable error bars.

  15. MOON for symmetry studies of neutrinos by double beta decays and neutrino nuclear responses

    NASA Astrophysics Data System (ADS)

    Ejiri, H.

    2010-11-01

    Neutrino-less double beta decays (0νββ) are used for high sensitivity studies of symmetry properties of neutrinos such as the Majorana nature of neutrinos, the absolute mass scale, the CP at the lepton sector, and others. Neutrino nuclear responses (0νββ nuclear matrix elements) are crucial for extracting these neutrino properties from 0νββ experiments. This is a brief report of the present status of MOON (spectroscopic 0νββ experiment) with the ν-mass sensitivity of 100-30 meV, and experimental ways to study the neutrino nuclear responses.

  16. Status and future of nuclear matrix elements for neutrinoless double-beta decay: a review.

    PubMed

    Engel, Jonathan; Menéndez, Javier

    2017-04-01

    The nuclear matrix elements that govern the rate of neutrinoless double beta decay must be accurately calculated if experiments are to reach their full potential. Theorists have been working on the problem for a long time but have recently stepped up their efforts as ton-scale experiments have begun to look feasible. Here we review past and recent work on the matrix elements in a wide variety of nuclear models and discuss work that will be done in the near future. Ab initio nuclear-structure theory, which is developing rapidly, holds out hope of more accurate matrix elements with quantifiable error bars.

  17. Nuclear structure relevant to neutrinoless double beta decay candidate {sup 130}Te and other recent results

    SciTech Connect

    Kay, B. P.

    2013-12-30

    We have undertaken a series of single-nucleon and pair transfer reaction measurements to help constrain calculations of the nuclear matrix elements for neutrinoless double beta decay. In this talk, a short overview of measurements relevant to the {sup 130}Te→{sup 130}Xe system is given. Brief mention is made of other recent and forthcoming results.

  18. Damage, crack growth and fracture characteristics of nuclear grade graphite using the Double Torsion technique

    NASA Astrophysics Data System (ADS)

    Becker, T. H.; Marrow, T. J.; Tait, R. B.

    2011-07-01

    The crack initiation and propagation characteristics of two medium grained polygranular graphites, nuclear block graphite (NBG10) and Gilsocarbon (GCMB grade) graphite, have been studied using the Double Torsion (DT) technique. The DT technique allows stable crack propagation and easy crack tip observation of such brittle materials. The linear elastic fracture mechanics (LEFM) methodology of the DT technique was adapted for elastic-plastic fracture mechanics (EPFM) in conjunction with a methodology for directly calculating the J-integral from in-plane displacement fields (JMAN) to account for the non-linearity of graphite deformation. The full field surface displacement measurement techniques of electronic speckle pattern interferometry (ESPI) and digital image correlation (DIC) were used to observe and measure crack initiation and propagation. Significant micro-cracking in the fracture process zone (FPZ) was observed as well as crack bridging in the wake of the crack tip. The R-curve behaviour was measured to determine the critical J-integral for crack propagation in both materials. Micro-cracks tended to nucleate at pores, causing deflection of the crack path. Rising R-curve behaviour was observed, which is attributed to the formation of the FPZ, while crack bridging and distributed micro-cracks are responsible for the increase in fracture resistance. Each contributes around 50% of the irreversible energy dissipation in both graphites.

  19. Nuclear matrix elements of the double beta decay for mass around 80

    NASA Astrophysics Data System (ADS)

    Yoshinaga, Naotaka; Higashiyama, Koji; Teruya, Eri

    2014-09-01

    In nature there are 30 kinds of nuclei which are expected to have double beta decays. Among them ten nuclei are actually observed for the neutrino double beta decays. Still no observation is made for the neutrinoless double beta decays (0 νββ) . The 0 νββ decay is expected to occur only when neutrinos have masses and they are Majorana particles. In that respect observation of 0 νββ is to determine whether neutrinos are Majorana particles or not. In theoretical side in order to estimate the half life of 0 νββ determination of the nuclear matrix elements are essential. They were calculated in many theoretical frameworks, but the results are not consistent in various models. In this study we carry out shell model calculations for 82Se and 82Kr nuclei. After obtaining the wavefunctions, we calculate the nuclear matrix elements. For comparison we make pair truncated shell model calculations.

  20. Nuclear Excitation by Electronic Transition of U-235

    NASA Astrophysics Data System (ADS)

    Chodash, Perry

    2017-01-01

    Nuclear excitation by electronic transition (NEET) is a rare nuclear excitation that is theorized to exist in numerous isotopes. NEET is the inverse of bound internal conversion and occurs when an electronic transition couples to a nuclear transition causing the nucleus to enter an excited state. This process can only occur for isotopes with low-lying nuclear levels due to the requirement that the electronic and nuclear transitions have similar energies. One of the candidate isotopes for NEET, 235U, has been studied several times over the past 40 years and NEET of 235U has never been conclusively observed. These past experiments generated conflicting results with some experiments claiming to observe NEET of 235U and others setting limits for the NEET rate. If NEET of 235U were to occur, the uranium would be excited to its first excited nuclear state. The first excited nuclear state in 235U is only 76 eV, the second lowest known nuclear state. Additionally, the 76 eV state is a nuclear isomer that decays by internal conversion with a half-life of 26 minutes. In order to measure whether NEET occurs in 235U and at what rate, a uranium plasma was required. The plasma was generated using a Q-switched Nd:YAG laser outputting 789 mJ pulses of 1064 nm light. The laser light was focused onto uranium targets generating an intensity on target of order 1012 W/cm2. The resulting plasma was captured on a catcher plate and electrons emitted from the catcher plate were accelerated and focused onto a microchannel plate detector. Measurements performed using a variety of uranium targets spanning depleted uranium up to 99.4% enriched uranium did not observe a 26 minute decay. An upper limit for the NEET rate of 235U was determined. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. The U.S. DHS, UC Berkeley, the NNIS fellowship and the NSSC further supported this work.

  1. Electron nuclear dynamics of H + + H 2O collisions

    NASA Astrophysics Data System (ADS)

    Hedström, M.; Morales, J. A.; Deumens, E.; Öhrn, Y.

    1997-11-01

    Proton water collisions at 46 eV in the center of mass frame are studied within the electron nuclear dynamics theory (END). The electronic degrees of freedom are described with a coherent state formulation of determinantal wavefunctions. The nuclei are treated as classical particles but full nonadiabatic couplings are retained. The equations of motion are formulated in a generalized phase space and bypass the use of preconstructed potential energy surfaces. Differential cross sections for inelastic and electron transfer reactions as well as energy transfer are compared with experiment.

  2. Flux noise in SQUIDs: Electron versus nuclear spins

    NASA Astrophysics Data System (ADS)

    de Sousa, Rogerio; Laforest, Stephanie

    2015-03-01

    Superconducting Quantum Interference Devices (SQUIDs) are limited by intrinsic flux noise whose origin is unknown. We develop a method to accurately calculate the flux produced by spin impurities in realistic superconducting thin film wires, and show that the flux produced by each spin is much larger than anticipated by former calculations. Remarkably, the total flux noise power due to electron spins at the thin side surface of the wires is found to be of similar magnitude as the one due to electrons at the wide top surface of the wires. In addition, flux noise due to lattice nuclear spins in the bulk of the wires is found to be a sizable fraction of the total noise for some SQUID geometries. We discuss the relative importance of electron and nuclear spin species in determining the total noise power, and propose strategies to design SQUIDs with lower flux noise. We acknowledge support from the Canadian agency NSERC through its Discovery and Engage programs.

  3. Internal Energy Loss of the Electrons Ejected in Neutrinoless Double Beta Decay

    NASA Astrophysics Data System (ADS)

    Drukarev, E. G.; Amusia, M. Ya.; Chernysheva, L. V.

    2017-01-01

    The excitations of the electron shell in neutrinoless double beta decay shifts the limiting energy available for ejected electrons. We present the general equations for this shift and make computations for the decays of two nuclei—germanium and xenon.

  4. Electron-electron double resonance (ELDOR) with a loop-gap resonator

    NASA Astrophysics Data System (ADS)

    Hyde, James S.; Yin, Jun-Jie; Froncisz, W.; Feix, Jimmy B.

    Electron-electron double-resonance (ELDOR) experiments on nitroxide-radical-spin-labeled liposomes have been performed using a loop-gap resonator. The signal-to-noise ratio expressed on a molarity basis is 20-fold over the best that has been achieved using a bimodal cavity. This improvement permits ELDOR experiments on spin-labeled plasma membranes of intact cells, as illustrated by a prototype experiment on red blood cells labeled with stearic acid spin label. Moreover, 20 times greater pumping energy density at the sample is achievable for a given incident pump power, permitting ELDOR experiments on less readily saturated systems. Pump and observing frequencies are introduced directly into the loop-gap resonator, which has a relatively low Q, and the pump electron paramagnetic resonance signal is isolated from the receiver using a high Q trap microwave filter.

  5. Isomer triggering via nuclear excitation by electron capture.

    PubMed

    Pálffy, Adriana; Evers, Jörg; Keitel, Christoph H

    2007-10-26

    Triggering of long-lived nuclear isomeric states via coupling to the atomic shells in the process of nuclear excitation by electron capture (NEEC) is studied. NEEC occurring in highly charged ions can excite the isomeric state to a triggering level that subsequently decays to the ground state. We present total cross sections for NEEC isomer triggering considering experimentally confirmed low-lying triggering levels and reaction rates based on realistic experimental parameters in ion storage rings. A comparison with other isomer triggering mechanisms shows that, among these, NEEC is the most efficient.

  6. Isomer Triggering via Nuclear Excitation by Electron Capture

    NASA Astrophysics Data System (ADS)

    Pálffy, Adriana; Evers, Jörg; Keitel, Christoph H.

    2007-10-01

    Triggering of long-lived nuclear isomeric states via coupling to the atomic shells in the process of nuclear excitation by electron capture (NEEC) is studied. NEEC occurring in highly charged ions can excite the isomeric state to a triggering level that subsequently decays to the ground state. We present total cross sections for NEEC isomer triggering considering experimentally confirmed low-lying triggering levels and reaction rates based on realistic experimental parameters in ion storage rings. A comparison with other isomer triggering mechanisms shows that, among these, NEEC is the most efficient.

  7. Spin labeling and Double Electron-Electron Resonance (DEER) to Deconstruct Conformational Ensembles of HIV Protease.

    PubMed

    Casey, Thomas M; Fanucci, Gail E

    2015-01-01

    An understanding of macromolecular conformational equilibrium in biological systems is oftentimes essential to understand function, dysfunction, and disease. For the past few years, our lab has been utilizing site-directed spin labeling (SDSL), coupled with electron paramagnetic resonance (EPR) spectroscopy, to characterize the conformational ensemble and ligand-induced conformational shifts of HIV-1 protease (HIV-1PR). The biomedical importance of characterizing the fractional occupancy of states within the conformational ensemble critically impacts our hypothesis of a conformational selection mechanism of drug-resistance evolution in HIV-1PR. The purpose of the following chapter is to give a timeline perspective of our SDSL EPR approach to characterizing conformational sampling of HIV-1PR. We provide detailed instructions for the procedure utilized in analyzing distance profiles for HIV-1PR obtained from pulsed electron-electron double resonance (PELDOR). Specifically, we employ a version of PELDOR known as double electron-electron resonance (DEER). Data are processed with the software package "DeerAnalysis" (http://www.epr.ethz.ch/software), which implements Tikhonov regularization (TKR), to generate a distance profile from electron spin-echo amplitude modulations. We assign meaning to resultant distance profiles based upon a conformational sampling model, which is described herein. The TKR distance profiles are reconstructed with a linear combination of Gaussian functions, which is then statistically analyzed. In general, DEER has proven powerful for observing structural ensembles in proteins and, more recently, nucleic acids. Our goal is to present our advances in order to aid readers in similar applications.

  8. Energy distribution of elastically scattered electrons from double layer samples

    NASA Astrophysics Data System (ADS)

    Tőkési, K.; Varga, D.

    2016-02-01

    We present a theoretical description of the spectra of electrons elastically scattered from thin double layered Au-C samples. The analysis is based on the Monte Carlo simulation of the recoil and Doppler effects in reflection and transmission geometries of the scattering at a fixed angle of 44.3 ° and a primary energy of 40 keV. The relativistic correction is taken into account. Besides the experimentally measurable energy distributions the simulations give many partial distributions separately, depending on the number of elastic scatterings (single, and multiple scatterings of different types). Furthermore, we present detailed analytical calculations for the main parameters of the single scattering, taking into account both the ideal scattering geometry, i.e. infinitesimally small angular range, and the effect of the real, finite angular range used in the measurements. We show our results for intensity ratios, peak shifts and broadenings for four cases of measurement geometries and layer thicknesses. While in the peak intensity ratios of gold and carbon for transmission geometries were found to be in good agreement with the results of the single scattering model, especially large deviations were obtained in reflection geometries. The separation of the peaks, depending on the geometry and the thickness, generally smaller, and the peak width generally larger than it can be expected from the nominal values of the primary energy, scattering angle, and mean kinetic energy of the atoms. We also show that the peaks are asymmetric even for the case of the single scattering due to the finite solid angle. Finally, we present a qualitative comparison with the experimental data. We find our resulting energy distribution of elastically scattered electrons to be in good agreement with recent measurements.

  9. Use of silicon pixel detectors in double electron capture experiments

    NASA Astrophysics Data System (ADS)

    Cermak, P.; Stekl, I.; Shitov, Yu A.; Mamedov, F.; Rukhadze, E. N.; Jose, J. M.; Cermak, J.; Rukhadze, N. I.; Brudanin, V. B.; Loaiza, P.

    2011-01-01

    A novel experimental approach to search for double electron capture (EC/EC) is discussed in this article. R&D for a new generation EC/EC spectrometer based on silicon pixel detectors (SPDs) has been conducted since 2009 for an upgrade of the TGV experiment. SPDs built on Timepix technology with a spectroscopic readout from each individual pixel are an effective tool to detect the 2νEC/EC signature of the two low energy X-rays hitting two separate pixels. The ability of SPDs to indentify α/β/γ particles and localize them precisely leads to effective background discrimination and thus considerable improvement of the signal-to-background ratio (S/B). A multi-SPD system, called a Silicon Pixel Telescope (SPT), is planned based on the experimental approach of the TGV calorimeter which measures thin foils of enriched EC/EC-isotope sandwiched between HPGe detectors working in coincidence mode. The sources of SPD internal background have been identified by measuring SPD radiopurity with a low-background HPGe detector as well as by long-term SPD background runs in the Modane underground laboratory (LSM, France), and results of these studies are presented.

  10. Quantum and classical correlations in electron-nuclear spin echo

    SciTech Connect

    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.

  11. Correlated electron-nuclear dissociation dynamics: classical versus quantum motion

    NASA Astrophysics Data System (ADS)

    Schaupp, Thomas; Albert, Julian; Engel, Volker

    2017-01-01

    We investigate the coupled electron-nuclear dynamics in a model system which undergoes dissociation. In choosing different initial conditions, the cases of adiabatic and non-adiabatic dissociation are realized. We treat the coupled electronic and nuclear motion in the complete configuration space so that classically, no surface hopping procedures have to be incorporated in the case that more than a single adiabatic electronic state is populated during the fragmentation. Due to the anharmonic interaction potential, it is expected that classical mechanics substantially deviate from quantum mechanics. However, we provide examples where the densities and fragmentation yields obtained from the two treatments are in astonishingly strong agreement in the case that one starts in the electronic ground state initially. As expected, larger deviations are found if one starts in electronically excited states where trajectories are sampled from the more spatially extended electronic wave function. In that case, higher initial energies are accessed, and the motion proceeds in regions with increasing degree of anharmonicity. Contribution to the Topical Issue "Dynamics of Molecular Systems (MOLEC 2016)", edited by Alberto Garcia-Vela, Luis Banares and Maria Luisa Senent.

  12. Low-voltage scanning electron microscopy study of lampbrush chromosomes and nuclear bodies in avian and amphibian oocytes

    PubMed Central

    Kulikova, Tatiana; Khodyuchenko, Tatiana; Petrov, Yuri; Krasikova, Alla

    2016-01-01

    Nucleus is a highly compartmentalized part of the cell where the key processes of genome functionality are realized through the formation of non-membranous nuclear domains. Physically nuclear domains appear as liquid droplets with different viscosity stably maintained throughout the interphase or during the long diplotene stage of meiosis. Since nuclear body surface represents boundary between two liquid phases, the ultrastructural surface topography of nuclear domains is of an outstanding interest. The aim of this study was to examine ultrathin surface topography of the amphibian and avian oocyte nuclear structures such as lampbrush chromosomes, nucleoli, histone-locus bodies, Cajal body-like bodies, and the interchromatin granule clusters via low-voltage scanning electron microscopy. Our results demonstrate that nuclear bodies with similar molecular composition may differ dramatically in the surface topography and vice versa, nuclear bodies that do not share common molecular components may possess similar topographical characteristics. We also have analyzed surface distribution of particular nuclear antigens (double stranded DNA, coilin and splicing snRNA) using indirect immunogold labeling with subsequent secondary electron detection of gold nanoparticles. We suggest that ultrastructural surface morphology reflects functional status of a nuclear body. PMID:27857188

  13. Real-time electron dynamics simulation of two-electron transfer reactions induced by nuclear motion

    NASA Astrophysics Data System (ADS)

    Suzuki, Yasumitsu; Yamashita, Koichi

    2012-04-01

    Real-time electron dynamics of two-electron transfer reactions induced by nuclear motion is calculated by three methods: the numerically exact propagation method, the time-dependent Hartree (TDH) method and the Ehrenfest method. We find that, as long as the nuclei move as localized wave packets, the TDH and Ehrenfest methods can reproduce the exact electron dynamics of a simple charge transfer reaction model containing two electrons qualitatively well, even when nonadiabatic transitions between adiabatic states occur. In particular, both methods can reproduce the cases where a complete two-electron transfer reaction occurs and those where it does not occur.

  14. The concept of the double-purpose electro-nuclear facility

    SciTech Connect

    Bergelson, B.P.; Balyuk, S.A.

    1995-10-01

    The parameters have been determined on a conceptual level of the electro-nuclear facility intended for electric power generation and minor actinide transmutation. Electro-nuclear facilities (ENFs) have been developed without apparent success for many years. The main difficulties are associated with high accelerator cost and absence of their own clearly defined place for ENFs in the nuclear-power complex. In recent years, however, the situation has changed in many aspects in connection with the rise in safety requirements for nuclear power industry and because of the necessity to decrease the equilibrium level of the long-lived radiotoxicity in particular. In the authors opinion double-purpose ENFs designed for power generation and tansmutation of minor actinides are promising. The results of conceptual investigations for such a facility being operated on liquid fuel in the condition of a uranium-plutonium fuel cycle are given here.

  15. Nuclear responses for double-beta decays by hadron, photon, and neutrino probes and MOON experiment

    NASA Astrophysics Data System (ADS)

    Ejiri, H.

    2006-05-01

    Neutrino-less double-beta decays (0νββ) with the mass sensitivities of the solar and atmospheric ν masses are of great interest for studying the Majorana nature of neutrinos and the absolute mass spectrum as suggested by recent ν oscillation experiments. Here nuclear responses (nuclear matrix elements) for 0νββ are crucial. They are well studied experimentally by using charge-exchange, photo-nuclear and neutrino reactions. MOON(Mo Observatory Of Neutrinos) is a high sensitivity 0νβ β experiment with the mass sensitivity of an order of 30 meV. Experimental studies of the nuclear responses and the present status of MOON are briefly discussed.

  16. Nuclear size correction to the electron self-energy

    SciTech Connect

    Mohr, P.J. ); Soff, G. , Planckstrasse 1, Postfach 110552, D-6100 Darmstadt )

    1993-01-11

    The nuclear size correction to the self-energy of an electron in the 1[ital S][sub 1/2], 2[ital S][sub 1/2], or 2[ital P][sub 1/2] state in hydrogenlike ions is calculated. The results modify theoretical predictions required for experimental tests of quantum electrodynamics in strong fields, and they resolve differences among previous calculations for the Lamb shift in hydrogenlike uranium. Results are presented for a number of elements ranging from iron ([ital Z]=26) to fermium ([ital Z]=100). An estimate of the nuclear model dependence of the effect is made, and, based on the numerical results, a simple formula for the correction as a function of the nuclear radius is provided.

  17. Degeneracy at 1871 keV in {sup 112}Cd and implications for neutrinoless double electron capture

    SciTech Connect

    Green, K. L.; Garrett, P. E.; Demand, G. A.; Grinyer, G. F.; Leach, K. G.; Phillips, A. A.; Schumaker, M. A.; Svensson, C. E.; Wong, J.; Austin, R. A. E.; Colosimo, S.; Ball, G. C.; Bandyopadhyay, D. S.; Hackman, G.; Morton, A. C.; Pearson, C. J.; Cross, D.; Kulp, W. D.; Wood, J. L.; Yates, S. W.

    2009-09-15

    High-statistics {beta}-decay measurements of {sup 112}Ag and {sup 112}In were performed to study the structure of the {sup 112}Cd nucleus. The precise energies of the doublet of levels at 1871 keV, for which the 0{sup +} member has been suggested as a possible daughter state following neutrinoless double electron capture of {sup 112}Sn, were determined to be 1871.137(72) keV (0{sub 4}{sup +} level) and 1870.743(54) keV (4{sub 2}{sup +} level). The nature of the 0{sub 4}{sup +} level, required for the calculation of the nuclear matrix element that would be needed to extract a neutrino mass from neutrinoless double electron capture to this state, is suggested to be of intruder origin.

  18. Lepton-violating β-β-, β+β+ decays, (e -, e +) conversion and double electron capture in gauge theories

    NASA Astrophysics Data System (ADS)

    Vergados, J. D.

    1983-05-01

    The lepton violating processes β-β-, β+β+, (e -, e +) and double electron capture have been investigated in the context of modern gauge theories. Mechanisms involving light or heavy intermediate Majorana neutrinos, with or without right-handed currents, as well as Higgs particles, have been studied. The lepton-violating emission of light bosons, recently proposed by Georgi, Glashow and Nussinov, has also been analyzed. From the analysis of the 48Ca → 48Ti data the following limits emerge: ∣ < m v > ∣ < 80 eV, m N > (2-20) × 10 3GeV, m W R > 400 GeVand g v eoverlinevex 0 < 5 × 10 -3. The above limits are then used to predict the lifetimes for β+β+, (e -, e +) and double electron capture in the A = 58, 92 and 96 systems employing realistic nuclear models.

  19. Exchange-Induced Spin Blockade in a Two-Electron Double Quantum Dot.

    PubMed

    Imanaka, D; Sharmin, S; Hashisaka, M; Muraki, K; Fujisawa, T

    2015-10-23

    We have experimentally identified the exchange-induced spin blockade in a GaAs double quantum dot. The transport is suppressed only when the eigenstates are well-defined singlet and triplet states, and thus sensitive to dynamic nuclear-spin polarization that causes singlet-triplet mixing. This gives rise to unusual current spectra, such as a sharp current dip and an asymmetric current profile near the triplet resonance of a double quantum dot. Numerical simulations suggest that the current dip is a signature of identical nuclear-spin polarization in the two dots, which is attractive for coherent spin manipulations in a material with nuclear spins.

  20. Active Interrogation Using Electronic Neutron Generators for Nuclear Safeguards Applications

    SciTech Connect

    David L. Chichester; Edward H. Seabury

    2008-08-01

    Active interrogation, a measurement technique which uses a radiation source to probe materials and generate unique signatures useful for characterizing those materials, is a powerful tool for assaying special nuclear material. The most commonly used technique for performing active interrogation is to use an electronic neutron generator as the probe radiation source. Exploiting the unique operating characteristics of these devices, including their monoenergetic neutron emissions and their ability to operate in pulsed modes, presents a number of options for performing prompt and delayed signature analyses using both photon and neutron sensors. A review of literature in this area shows multiple applications of the active neutron interrogation technique for performing nuclear nonproliferation measurements. Some examples include measuring the plutonium content of spent fuel, assaying plutonium residue in spent fuel hull claddings, assaying plutonium in aqueous fuel reprocessing process streams, and assaying nuclear fuel reprocessing facility waste streams to detect and quantify fissile material. This paper discusses the historical use of this technique and examines its context within the scope and challenges of next-generation nuclear fuel cycles and advanced concept nuclear fuel cycle facilities.

  1. Analytical nuclear derivatives for the parametric two-electron reduced density matrix method

    NASA Astrophysics Data System (ADS)

    Valentine, Andrew J. S.; Mazziotti, David A.

    2017-10-01

    Efficient and accurate nuclear gradients are essential to performing molecular optimizations. Here for the first time we present analytical nuclear gradients for the parametric two-electron reduced-density-matrix method (p2-RDM), which uses the 2-RDM as the primary variable in calculations in lieu of the many-electron wavefunction. While numerical gradients require six energy evaluations for each atom, analytical gradients require only a single calculation for each geometry sampled. We present benchmark p2-RDM geometry optimizations that show analytical gradients reduce CPU times by as much as 80%, even for small molecules. We also use p2-RDM to evaluate the bond length alternation (BLA), or the difference in length between adjacent single and double bonds, of trans-polyacetylene (PA). We find that the BLA in the extrapolated limit to be 0.080 Å, in agreement with experiment and closely mirroring the prediction of the more expensive coupled-cluster with single and double excitations with perturbative triples (CCSD(T)).

  2. Spin labeling and Double Electron-Electron Resonance (DEER) to Deconstruct Conformational Ensembles of HIV Protease

    PubMed Central

    Casey, Thomas M.; Fanucci, Gail E.

    2016-01-01

    An understanding of macromolecular conformational equilibrium in biological systems is oftentimes essential to understand function, dysfunction, and disease. For the past few years, our lab has been utilizing site-directed spin labeling (SDSL), coupled with electron paramagnetic resonance (EPR) spectroscopy, to characterize the conformational ensemble and ligand-induced conformational shifts of HIV-1 protease (HIV-1PR). The biomedical importance of characterizing the fractional occupancy of states within the conformational ensemble critically impacts our hypothesis of a conformational selection mechanism of drug-resistance evolution in HIV-1PR. The purpose of the following chapter is to give a timeline perspective of our SDSL EPR approach to characterizing conformational sampling of HIV-1PR. We provide detailed instructions for the procedure utilized in analyzing distance profiles for HIV-1PR obtained from pulsed electron–electron double resonance (PELDOR). Specifically, we employ a version of PELDOR known as double electron–electron resonance (DEER). Data are processed with the software package “DeerAnalysis” (http://www.epr.ethz.ch/software), which implements Tikhonov regularization (TKR), to generate a distance profile from electron spin-echo amplitude modulations. We assign meaning to resultant distance profiles based upon a conformational sampling model, which is described herein. The TKR distance profiles are reconstructed with a linear combination of Gaussian functions, which is then statistically analyzed. In general, DEER has proven powerful for observing structural ensembles in proteins and, more recently, nucleic acids. Our goal is to present our advances in order to aid readers in similar applications. PMID:26477251

  3. On Cu(II) Cu(II) distance measurements using pulsed electron electron double resonance

    NASA Astrophysics Data System (ADS)

    Yang, Zhongyu; Becker, James; Saxena, Sunil

    2007-10-01

    The effects of orientational selectivity on the 4-pulse electron electron double resonance (PELDOR) ESR spectra of coupled Cu(II)-Cu(II) spins are presented. The data were collected at four magnetic fields on a poly-proline peptide containing two Cu(II) centers. The Cu(II)-PELDOR spectra of this peptide do not change appreciably with magnetic field at X-band. The data were analyzed by adapting the theory of Maryasov, Tsvetkov, and Raap [A.G. Maryasov, Y.D. Tsvetkov, J. Raap, Weakly coupled radical pairs in solids:ELDOR in ESE structure studies, Appl. Magn. Reson. 14 (1998) 101-113]. Simulations indicate that orientational effects are important for Cu(II)-PELDOR. Based on simulations, the field-independence of the PELDOR data for this peptide is likely due to two effects. First, for this peptide, the Cu(II) g-tensor(s) are in a very specific orientation with respect to the interspin vector. Second, the flexibility of the peptide washes out the orientation effects. These effects reduce the suitability of the poly-proline based peptide as a good model system to experimentally probe orientational effects in such experiments. An average Cu(II)-Cu(II) distance of 2.1-2.2 nm was determined, which is consistent with earlier double quantum coherence ESR results.

  4. A continuous-wave electron-nuclear double resonance (X-band) study of the Cu2+ sites of particulate methane mono-oxygenase of Methylococcus capsulatus (strain M) in membrane and pure dopamine beta-mono-oxygenase of the adrenal medulla.

    PubMed Central

    Katterle, Bettina; Gvozdev, Rudolf I; Abudu, Ntei; Ljones, Torbjørn; Andersson, K Kristoffer

    2002-01-01

    All methanotrophic bacteria express a membrane-bound (particulate) methane mono-oxygenase (pMMO). In the present study, we have investigated pMMO in membrane fragments from Methylococcus capsulatus (strain M). pMMO contains a typical type-2 Cu(2+) centre with the following EPR parameters: g(z) 2.24, g(x,y) 2.06, A(Cu)(z) 19.0 mT and A(Cu)(x,y) 1.0 mT. Simulation of the Cu(2+) spectrum yielded a best match by using four equivalent nitrogens (A(N)=1.5 mT, 42 MHz). Incubation with ferricyanide neither changed nor increased the amount of EPR-active Cu(2+), in contrast with other reports. The EPR visible copper seems not to be part of any cluster, as judged from the microwave power saturation behaviour. Continuous-wave electron-nuclear double resonance (CW ENDOR; 9.4 GHz, 5-20 K) experiments at g( perpendicular) of the Cu(II) spectrum show a weak coupling to protons with an A(H) of 2.9 MHz that corresponds to a distance of 3.8 A (1 A identical with 0.1 nm), assuming that it is a purely dipolar coupling. Incubation in (2)H(2)O leads to a significant decrease in these (1)H-ENDOR intensities, showing that these protons are exchangeable. This result strongly suggests that the EPR visible copper site of pMMO is accessible to solvent, which was confirmed by the chelation of the Cu(2+) by diethyldithiocarbamic acid. The (1)H and (14)N hyperfine coupling constants confirm a histidine ligation of the EPR visible copper site in pMMO. The hyperfine structure in the ENDOR or EPR spectra of pMMO is not influenced by the inhibitors azide, cyanide or ammonia, indicating that they do not bind to the EPR visible copper. We compared pMMO with the type-2 Cu(2+) enzyme, dopamine beta-mono-oxygenase (DbetaM). For DbetaM, it is assumed that the copper site is solvent-accessible. CW ENDOR shows similar weakly coupled and (2)H(2)O-exchangeable protons (2.9 MHz), as observed in pMMO, as well as the strongly coupled nitrogens (40 MHz) from the co-ordinating N of the histidines in DbetaM. In

  5. Suppression of Zeeman gradients by nuclear polarization in double quantum dots.

    PubMed

    Frolov, S M; Danon, J; Nadj-Perge, S; Zuo, K; van Tilburg, J W W; Pribiag, V S; van den Berg, J W G; Bakkers, E P A M; Kouwenhoven, L P

    2012-12-07

    We use electric dipole spin resonance to measure dynamic nuclear polarization in InAs nanowire quantum dots. The resonance shifts in frequency when the system transitions between metastable high and low current states, indicating the presence of nuclear polarization. We propose that the low and the high current states correspond to different total Zeeman energy gradients between the two quantum dots. In the low current state, dynamic nuclear polarization efficiently compensates the Zeeman gradient due to the g-factor mismatch, resulting in a suppressed total Zeeman gradient. We present a theoretical model of electron-nuclear feedback that demonstrates a fixed point in nuclear polarization for nearly equal Zeeman splittings in the two dots and predicts a narrowed hyperfine gradient distribution.

  6. 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.

  7. Energetics and electronic structure of double-walled boron nanotubes

    NASA Astrophysics Data System (ADS)

    Tang, Hui; Ismail-Beigi, Sohrab

    2010-03-01

    Single-walled boron nanotubes have been studied extensively since their first successful fabrication in experiments. On the other hand, double-walled or multi-walled boron nanotubes have not yet been discussed in literature. Here, using density functional theory, we present a stable semiconducting two-dimensional double-layered boron sheet, which is 0.14 eV/atom more stable than the most stable single-layered α-sheet [1]. This double-layered sheet is stabilized due to the formation of inter-layer bonds. We show that double-walled boron nanotubes made from this double-layered sheet are all semiconducting. These double-walled nanotubes are more stable than single-walled ones for large nanotubes, but become less energetically favorable when the tube radius is smaller than 20 å due to their large curvature energies. To reduce the large curvature energies, we construct double-walled nanotubes whose inner and outer walls have different number of atoms around their circumference. The resulting nanotubes are more stable than single-walled ones for all radii.[4pt] [1] H. Tang, and S. Ismail-Beigi, PRL 99, 115501 (2007).

  8. Heterogeneous electron transfer at nanoscopic electrodes: importance of electronic structures and electric double layers.

    PubMed

    Chen, Shengli; Liu, Yuwen; Chen, Junxiang

    2014-08-07

    Heterogeneous electron-transfer (ET) processes at solid electrodes play key roles in molecular electronics and electrochemical energy conversion and sensing. Electrode nanosization and/or nanostructurization are among the major current strategies for performance promotion in these fields. Besides, nano-sized/structured electrodes offer great opportunities to characterize electrochemical structures and processes with high spatial and temporal resolution. This review presents recent insights into the nanoscopic size and structure effects of electrodes and electrode materials on heterogeneous ET kinetics, by emphasizing the importance of the electric double-layer (EDL) at the electrode/electrolyte interface and the electronic structure of electrode materials. It is shown, by general conceptual analysis and recent example demonstrations of representative electrode systems including electrodes of nanometer sizes and gaps and of nanomaterials such as sp(2) hybridized nanocarbons and semiconductor quantum dots, how the heterogeneous ET kinetics, the electronic structures of electrodes, the EDL structures at the electrode/electrolyte interface and the nanoscopic electrode sizes and structures may be related.

  9. Competition between radiative recombination and nuclear excitation by electron capture

    NASA Astrophysics Data System (ADS)

    Pály, A.; Harman, Z.; Surzhykov, A.; Scheid, W.

    2007-03-01

    The process of electron recombination is investigated considering the possible resonant channel of nuclear excitation by electron capture (NEEC), in which a continuum electron is captured into a bound state of an ion with the simultaneous excitation of the nucleus. Transition rates and total cross sections for NEEC followed by the radiative decay of the nucleus are presented for various heavy-ion collision systems. The role played by radiative recombination (RR) in the NEEC recombination mechanism is investigated and theoretical estimates of the magnitude of the interference between the two processes are presented. We discuss the experimental possibility of discerning NEEC from the RR background, studying the angular distribution of the radiation emitted in the two processes.

  10. Fast electron beam measurements from relativistically intense, frequency-doubled laser-solid interactions

    NASA Astrophysics Data System (ADS)

    Scott, R. H. H.; Pérez, F.; Streeter, M. J. V.; Clark, E. L.; Davies, J. R.; Schlenvoigt, H.-P.; Santos, J. J.; Hulin, S.; Lancaster, K. L.; Dorchies, F.; Fourment, C.; Vauzour, B.; Soloviev, A. A.; Baton, S. D.; Rose, S. J.; Norreys, P. A.

    2013-09-01

    Experimental measurements of the fast electron beam created by the interaction of relativistically intense, frequency-doubled laser light with planar solid targets and its subsequent transport within the target are presented and compared with those of a similar experiment using the laser fundamental frequency. Using frequency-doubled laser light, the fast electron source size is significantly reduced, while evidence suggests the divergence angle may be reduced. Pyrometric measurements of the target rear surface temperature and the Cu Kα imager data indicate the laser to fast electron absorption fraction is reduced using frequency doubled laser light. Bremsstrahlung measurements indicate the fast electron temperature is 125 keV, while the laser energy absorbed into forward-going fast electrons was found to be 16 ± 4% for frequency doubled light at a mean laser intensity of 5 ± 3 × 1018 W cm-2.

  11. Neutrino nuclear responses for double beta decays and astro neutrinos by charge exchange reactions

    NASA Astrophysics Data System (ADS)

    Ejiri, Hiroyasu

    2014-09-01

    Neutrino nuclear responses are crucial for neutrino studies in nuclei. Charge exchange reactions (CER) are shown to be used to study charged current neutrino nuclear responses associated with double beta decays(DBD)and astro neutrino interactions. CERs to be used are high energy-resolution (He3 ,t) reactions at RCNP, photonuclear reactions via IAR at NewSUBARU and muon capture reactions at MUSIC RCNP and MLF J-PARC. The Gamow Teller (GT) strengths studied by CERs reproduce the observed 2 neutrino DBD matrix elements. The GT and spin dipole (SD) matrix elements are found to be reduced much due to the nucleon spin isospin correlations and the non-nucleonic (delta isobar) nuclear medium effects. Impacts of the reductions on the DBD matrix elements and astro neutrino interactions are discussed.

  12. Controlled energy-selected electron capture and release in double quantum dots

    NASA Astrophysics Data System (ADS)

    Pont, Federico M.; Bande, Annika; Cederbaum, Lorenz S.

    2013-12-01

    Highly accurate quantum electron dynamics calculations demonstrate that energy can be efficiently transferred between quantum dots. Specifically, in a double quantum dot an incoming electron is captured by one dot and the excess energy is transferred to the neighboring dot and used to remove an electron from this dot. This process is due to long-range electron correlation and shown to be operative at rather large distances between the dots. The efficiency of the process is greatly enhanced by preparing the double quantum dot such that the incoming electron is initially captured by a two-electron resonance state of the system. In contrast to atoms and molecules in nature, double quantum dots can be manipulated to achieve this enhancement. This mechanism leads to a surprisingly narrow distribution of the energy of the electron removed in the process which is explained by resonance theory. We argue that the process could be exploited in practice.

  13. Limit on the radiative neutrinoless double electron capture of ^{36}Ar from GERDA Phase I

    NASA Astrophysics Data System (ADS)

    Agostini, M.; Allardt, M.; Bakalyarov, A. M.; Balata, M.; Barabanov, I.; Barros, N.; Baudis, L.; Bauer, C.; Bellotti, E.; Belogurov, S.; Belyaev, S. T.; Benato, G.; Bettini, A.; Bezrukov, L.; Bode, T.; Borowicz, D.; Brudanin, V.; Brugnera, R.; Caldwell, A.; Cattadori, C.; Chernogorov, A.; D'Andrea, V.; Demidova, E. V.; di Vacri, A.; Domula, A.; Doroshkevich, E.; Egorov, V.; Falkenstein, R.; Fedorova, O.; Freund, K.; Frodyma, N.; Gangapshev, A.; Garfagnini, A.; Gooch, C.; Grabmayr, P.; Gurentsov, V.; Gusev, K.; Hakenmüller, J.; Hegai, A.; Heisel, M.; Hemmer, S.; Heusser, G.; Hofmann, W.; Hult, M.; Inzhechik, L. V.; Csáthy, J. Janicskó; Jochum, J.; Junker, M.; Kazalov, V.; Kihm, T.; Kirpichnikov, I. V.; Kirsch, A.; Kish, A.; Klimenko, A.; Kneißl, R.; Knöpfle, K. T.; Kochetov, O.; Kornoukhov, V. N.; Kuzminov, V. V.; Laubenstein, M.; Lazzaro, A.; Lebedev, V. I.; Lehnert, B.; Liao, H. Y.; Lindner, M.; Lippi, I.; Lubashevskiy, A.; Lubsandorzhiev, B.; Lutter, G.; Macolino, C.; Majorovits, B.; Maneschg, W.; Medinaceli, E.; Miloradovic, M.; Mingazheva, R.; Misiaszek, M.; Moseev, P.; Nemchenok, I.; Palioselitis, D.; Panas, K.; Pandola, L.; Pelczar, K.; Pullia, A.; Riboldi, S.; Rumyantseva, N.; Sada, C.; Salamida, F.; Salathe, M.; Schmitt, C.; Schneider, B.; Schönert, S.; Schreiner, J.; Schütz, A.-K.; Schulz, O.; Schwingenheuer, B.; Selivanenko, O.; Shirchenko, M.; Simgen, H.; Smolnikov, A.; Stanco, L.; Stepaniuk, M.; Vanhoefer, L.; Vasenko, A. A.; Veresnikova, A.; von Sturm, K.; Wagner, V.; Walter, M.; Wegmann, A.; Wester, T.; Wiesinger, C.; Wilsenach, H.; Wojcik, M.; Yanovich, E.; Zhitnikov, I.; Zhukov, S. V.; Zinatulina, D.; Zuber, K.; Zuzel, G.

    2016-12-01

    Neutrinoless double electron capture is a process that, if detected, would give evidence of lepton number violation and the Majorana nature of neutrinos. A search for neutrinoless double electron capture of ^{36}Ar has been performed with germanium detectors installed in liquid argon using data from Phase I of the GERmanium Detector Array ( Gerda) experiment at the Gran Sasso Laboratory of INFN, Italy. No signal was observed and an experimental lower limit on the half-life of the radiative neutrinoless double electron capture of ^{36}Ar was established: T_{1/2} > 3.6 × 10^{21} years at 90% CI.

  14. Transport and Charge Manipulation in a Single Electron Silicon Double Quantum Dot

    NASA Astrophysics Data System (ADS)

    Wang, K.; Payette, C.; Dovzhenko, Y.; Petta, J. R.

    2013-03-01

    Silicon is one of the most promising candidates for ultra-coherent qubits due to its relatively early position in periodical table and the absence of nuclear spin in its naturally abundant isotope. Here we demonstrate a reliable recipe that enables us to reproducibly fabricate an accumulation mode few electron double quantum dot (DQD). We demonstrate tunable interdot tunnel coupling at single electron occupancy in the device. The charge state of the qubit is monitored by measuring the amplitude of the radio frequency signal that is reflected from a resonant circuit coupled to a charge sensor. By applying microwave radiation to the depletion gates, we probe the energy level structure of the DQD using photon assisted tunneling (PAT). We apply bursts of microwave radiation and monitor the dependence of the PAT peak height on the burst period to extract the charge relaxation time, T1. By experimentally tuning the charge qubit Hamiltonian, we measure the tunnel coupling and detuning dependence of T1. Supported by the United States Department of Defense. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressly or implied, of the U.S. Government.

  15. Radiation Hardened Electronics Destined For Severe Nuclear Reactor Environments

    SciTech Connect

    Holbert, Keith E.; Clark, Lawrence T.

    2016-02-19

    Post nuclear accident conditions represent a harsh environment for electronics. The full station blackout experience at Fukushima shows the necessity for emergency sensing capabilities in a radiation-enhanced environment. This NEET (Nuclear Energy Enabling Technologies) research project developed radiation hardened by design (RHBD) electronics using commercially available technology that employs commercial off-the-shelf (COTS) devices and present generation circuit fabrication techniques to improve the total ionizing dose (TID) hardness of electronics. Such technology not only has applicability to severe accident conditions but also to facilities throughout the nuclear fuel cycle in which radiation tolerance is required. For example, with TID tolerance to megarads of dose, electronics could be deployed for long-term monitoring, inspection and decontamination missions. The present work has taken a two-pronged approach, specifically, development of both board and application-specific integrated circuit (ASIC) level RHBD techniques. The former path has focused on TID testing of representative microcontroller ICs with embedded flash (eFlash) memory, as well as standalone flash devices that utilize the same fabrication technologies. The standalone flash devices are less complicated, allowing better understanding of the TID response of the crucial circuits. Our TID experiments utilize biased components that are in-situ tested, and in full operation during irradiation. A potential pitfall in the qualification of memory circuits is the lack of rigorous testing of the possible memory states. For this reason, we employ test patterns that include all ones, all zeros, a checkerboard of zeros and ones, an inverse checkerboard, and random data. With experimental evidence of improved radiation response for unbiased versus biased conditions, a demonstration-level board using the COTS devices was constructed. Through a combination of redundancy and power gating, the demonstration

  16. Determination of nitrogen spin concentration in diamond using double electron-electron resonance

    NASA Astrophysics Data System (ADS)

    Stepanov, Viktor; Takahashi, Susumu

    2016-07-01

    Diamond has been extensively investigated recently due to a wide range of potential applications of nitrogen-vacancy (NV) defect centers existing in a diamond lattice. The applications include magnetometry and quantum information technologies, and long decoherence time (T2) of NV centers is critical for those applications. Although it has been known that T2 highly depends on the concentration of paramagnetic impurities in diamond, precise measurement of the impurity concentration remains challenging. In the present work we show a method to determine a wide range of the nitrogen concentration (n ) in diamond using a wide-band high-frequency electron spin resonance and double electron-electron resonance spectrometer. Moreover, we investigate T2 of the nitrogen impurities and show the relationship between T2 and n . The method developed here is applicable for various spin systems in solid and implementable in nanoscale magnetic resonance spectroscopy with NV centers to characterize the concentration of the paramagnetic spins within a microscopic volume.

  17. Nuclear Recoil Cross Sections from Time-dependent Studies of Two-Photon Double Ionization of Helium

    SciTech Connect

    Horner, Daniel A.; Rescigno, Thomas N.; McCurdy, C. William

    2009-12-21

    We examine the sensitivity of nuclear recoil cross sections produced by two-photon double ionization of helium to the underlying triple differential cross sections (TDCS) used in their computation. We show that this sensitivity is greatest in the energy region just below the threshold for sequential double ionization. Accurate TDCS, extracted from non-perturbative solutions of the time-dependent Schroedinger equation, are used here in new computations of the nuclear recoil cross section.

  18. Heavy-ion double charge exchange reactions: A tool toward 0 νββ nuclear matrix elements

    NASA Astrophysics Data System (ADS)

    Cappuzzello, F.; Cavallaro, M.; Agodi, C.; Bondì, M.; Carbone, D.; Cunsolo, A.; Foti, A.

    2015-11-01

    The knowledge of the nuclear matrix elements for the neutrinoless double beta decay is fundamental for neutrino physics. In this paper, an innovative technique to extract information on the nuclear matrix elements by measuring the cross section of a double charge exchange nuclear reaction is proposed. The basic point is that the initial- and final-state wave functions in the two processes are the same and the transition operators are similar. The double charge exchange cross sections can be factorized in a nuclear structure term containing the matrix elements and a nuclear reaction factor. First pioneering experimental results for the 40Ca(18O,18Ne)40Ar reaction at 270 MeV incident energy show that such cross section factorization reasonably holds for the crucial 0+ → 0+ transition to 40Args, at least at very forward angles.

  19. Double electron-electron resonance with multiple non-selective chirp refocusing.

    PubMed

    Doll, Andrin; Jeschke, Gunnar

    2017-01-04

    A new approach to double electron-electron resonance (DEER) for distance determination involving nitroxide spin labels at dilute concentrations is presented. In general, DEER pulse sequences rely on double resonance between pump and observer spins excited by selective pulses at two distinct microwave frequencies. In the new approach abbreviated as nDEER, non-selective chirp pulses that refocus all relevant spin pairs are combined with DEER. This non-selective refocusing results in suppression of unmodulated contributions, such as the constant contribution as well as the background curvature due to inter-molecular spin partners in ordinary DEER data. Due to this dipolar attenuation effect, primary nDEER data are closer to the dipolar modulation of primary interest than ordinary DEER data. Restrictions of nDEER are that secondary information related to these unmodulated contributions becomes difficult to retrieve. Accordingly, incomplete deconvolution of the inter-molecular background prevents the application of nDEER to rigid spin pairs at high concentrations. A key advantage of nDEER is the high fidelity of the chirp refocusing pulses, which is important for nDEER schemes that incorporate dynamical decoupling to access longer distances. In this context, nDEER with Carr-Purcell (CP) pulse trains having N = 2 and N = 4 refocusing pulses are demonstrated. These CP nDEER sequences require a total of N + 2 pulses, which is less than the 2N + 1 pulses required for CP DEER schemes. The pump pulse position is incremented throughout the refocusing pulses, which restricts the minimum time increment to 96 ns on our spectrometer and therefore complicates application to distances below 3 nm. At Q-band frequencies, unwanted modulations related to pulse imperfections contribute only 3.5% relative to the principal nDEER modulation. Accordingly, there is no need for dedicated data reconstruction methods as in CP DEER methods.

  20. Spectral structure of electron antineutrinos from nuclear reactors.

    PubMed

    Dwyer, D A; Langford, T J

    2015-01-09

    Recent measurements of the positron energy spectrum obtained from inverse beta decay interactions of reactor electron antineutrinos show an excess in the 4 to 6 MeV region relative to current predictions. First-principles calculations of fission and beta decay processes within a typical pressurized water reactor core identify prominent fission daughter isotopes as a possible origin for this excess. These calculations also predict percent-level substructures in the antineutrino spectrum due to Coulomb effects in beta decay. Precise measurement of these substructures can elucidate the nuclear processes occurring within reactors. These substructures can be a systematic issue for measurements utilizing the detailed spectral shape.

  1. Relativistic effects on giant resonances in electron-impact double ionization

    SciTech Connect

    Pindzola, M.S.

    1987-06-01

    The electron-impact double-ionization cross section for Fr/sup +/ is calculated in the distorted-wave Born approximation. A giant resonance in the 5d subshell ionization-autoionization contribution to the cross section is found to be quite sensitive to changes in the double-well potential caused by relativistic effects on bound-state wave functions.

  2. Single electron pumping in InAs nanowire double quantum dots

    NASA Astrophysics Data System (ADS)

    Fuhrer, A.; Fasth, C.; Samuelson, L.

    2007-07-01

    Closely spaced local gate electrodes are used to electrically define a double quantum dot along an InAs nanowire crystal. By applying a periodic pulse sequence to two plunger gate electrodes controlling the double quantum dot charge configuration, the device is operated as a single electron pump. The authors find that within measurement accuracy, the pumping current equals one electron per cycle for frequencies up to 2MHz, demonstrating the suitability of nanowire based quantum dots for pumping applications.

  3. Correlated electron-nuclear dynamics with conditional wave functions.

    PubMed

    Albareda, Guillermo; Appel, Heiko; Franco, Ignacio; Abedi, Ali; Rubio, Angel

    2014-08-22

    The molecular Schrödinger equation is rewritten in terms of nonunitary equations of motion for the nuclei (or electrons) that depend parametrically on the configuration of an ensemble of generally defined electronic (or nuclear) trajectories. This scheme is exact and does not rely on the tracing out of degrees of freedom. Hence, the use of trajectory-based statistical techniques can be exploited to circumvent the calculation of the computationally demanding Born-Oppenheimer potential-energy surfaces and nonadiabatic coupling elements. The concept of the potential-energy surface is restored by establishing a formal connection with the exact factorization of the full wave function. This connection is used to gain insight from a simplified form of the exact propagation scheme.

  4. Nuclear mean field and double-folding model of the nucleus-nucleus optical potential

    NASA Astrophysics Data System (ADS)

    Khoa, Dao T.; Phuc, Nguyen Hoang; Loan, Doan Thi; Loc, Bui Minh

    2016-09-01

    Realistic density dependent CDM3Yn versions of the M3Y interaction have been used in an extended Hartree-Fock (HF) calculation of nuclear matter (NM), with the nucleon single-particle potential determined from the total NM energy based on the Hugenholtz-van Hove theorem that gives rise naturally to a rearrangement term (RT). Using the RT of the single-nucleon potential obtained exactly at different NM densities, the density and energy dependence of the CDM3Yn interactions was modified to account properly for both the RT and observed energy dependence of the nucleon optical potential. Based on a local density approximation, the double-folding model of the nucleus-nucleus optical potential has been extended to take into account consistently the rearrangement effect and energy dependence of the nuclear mean-field potential, using the modified CDM3Yn interactions. The extended double-folding model was applied to study the elastic 12C+12C and 16O+12C scattering at the refractive energies, where the Airy structure of the nuclear rainbow has been well established. The RT was found to affect significantly the real nucleus-nucleus optical potential at small internuclear distances, giving a potential strength close to that implied by the realistic optical model description of the Airy oscillation.

  5. Dynamic Phase Shifts in Nanoscale Distance Measurements by Double Electron Electron Resonance (DEER)†

    SciTech Connect

    Bowman, Michael K.; Maryasov, Alexander G.

    2007-04-01

    The off-resonant pump pulse used in double electron electron resonance (DEER) measurements produces dynamic phase shifts that are explained here by simple analytic and vector descriptions of the full range of signal behaviors observed during DEER measurements, including: large phase shifts in the signal; changes in the position and shape of the detected echo; and changes in the signal intensity. The dynamic phase shifts depend on the width, amplitude and offset frequency of the pump pulse. Isolated radicals as well as pairs or clusters of dipolar-coupled radicals have the same dynamic phase shift that is independent of pump pulse delay in a typical measurement. A method of calibrating both the pump pulse offset frequency and the pump pulse field strength is outlined. A vector model is presented that explains the dynamic phase shifts in terms of precessing magnetization that is either spin locked or precessing about the effective pump field during the pump pulse. Implications of the dynamic phase shifts are discussed as they relate to setting up, calibrating and interpreting the results of DEER measurements.

  6. Dynamic phase shifts in nanoscale distance measurements by double electron electron resonance (DEER)

    NASA Astrophysics Data System (ADS)

    Bowman, Michael K.; Maryasov, Alexander G.

    2007-04-01

    The off-resonant pump pulse used in double electron electron resonance (DEER) measurements produces dynamic phase shifts that are explained here by simple analytic and vector descriptions of the full range of signal behaviors observed during DEER measurements, including: large phase shifts in the signal; changes in the position and shape of the detected echo; and changes in the signal intensity. The dynamic phase shifts depend on the width, amplitude and offset frequency of the pump pulse. Isolated radicals as well as pairs or clusters of dipolar-coupled radicals have the same dynamic phase shift that is independent of pump pulse delay in a typical measurement. A method of calibrating both the pump pulse offset frequency and the pump pulse field strength is outlined. A vector model is presented that explains the dynamic phase shifts in terms of precessing magnetization that is either spin locked or precessing about the effective pump field during the pump pulse. Implications of the dynamic phase shifts are discussed as they relate to setting up, calibrating and interpreting the results of DEER measurements.

  7. Cysteine-Specific Cu2+ Chelating Tags Used as Paramagnetic Probes in Double Electron Electron Resonance

    PubMed Central

    Cunningham, Timothy F.; Shannon, Matthew D.; Putterman, Miriam R.; Arachchige, Rajith J.; Sengupta, Ishita; Gao, Min; Jaroniec, Christopher P.; Saxena, Sunil

    2015-01-01

    Double electron electron resonance (DEER) is an attractive technique that is utilized for gaining insight into protein structure and dynamics via nanometer-scale distance measurements. The most commonly used paramagnetic tag in these measurements is a nitroxide spin label, R1. Here, we present the application of two types of high-affinity Cu2+ chelating tags, based on the EDTA and cyclen metal-binding motifs as alternative X-band DEER probes, using the B1 immunoglobulin-binding domain of protein G (GB1) as a model system. Both types of tags have been incorporated into a variety of protein secondary structure environments and exhibit high spectral sensitivity. In particular, the cyclen-based tag displays distance distributions with comparable distribution widths and most probable distances within 1–3 Å when compared to homologous R1 distributions. The results display the viability of the cyclen tag as an alternative to the R1 side chain for X-band DEER distance measurements in proteins. PMID:25608028

  8. Calculation of Cross Sections in Electron-Nuclear Dynamics

    NASA Astrophysics Data System (ADS)

    Cabrera-Trujillo, R.; Sabin, John R.; Deumens, E.; Öhrn, Y.

    In this work, we present an overview of the study of total and differential cross section calculations within the electron-nuclear dynamics (END). END is a method to solve the time-dependent Schrödinger equation in a non-adiabatic approach to direct dynamics. The method takes advantage of a coherent state representation of the molecular wave function. A quantum-mechanical Lagrangian formulation is employed to approximate the Schrödinger equation, via the time-dependent variational principle, to a set of coupled first-order differential equations in time for the END. We obtain the final wave function for the system allowing the determination of collisional properties of interest, as for example, deflection functions, charge exchange probabilities and amplitudes, and differential cross sections. We discuss the use and selection of basis sets for both the electronic description of the colliding systems as well as for their importance in the description of electron capture. As quantum effects are important in many cases and lacking for classical nuclei, we discuss the Schiff methodology and its advantages over other traditional methods for including semiclassical corrections. Time-lapse rendering of the dynamics of the participating electrons and atomic nuclei provides for a detailed view of dynamical and reactive processes. Comparison to experimental and other theoretical results is provided where appropriate data are available.

  9. Double K-shell vacancy production in the electron capture decay of 125I

    NASA Astrophysics Data System (ADS)

    Hindi, M. M.; Kozub, R. L.

    1992-03-01

    We have measured the probability of double K-shell vacancy production in the electron capture decay of 125I to the 35-keV level of 125Te. The probability was deduced from the number of triple coincidences between the Te hypersatellite and satellite x rays produced in filling the double vacancy, and the subsequent normal x ray accompanying the K internal conversion of the 35-keV level. The probability of double K-shell vacancy production per K-shell electron capture (PKK) was found to be (1.35+/-0.15)×10-5.

  10. Electron dynamics of molecular double ionization by circularly polarized laser pulses

    SciTech Connect

    Tong, Aihong; Zhou, Yueming; Huang, Cheng; Lu, Peixiang

    2013-08-21

    Using the classical ensemble method, we have investigated double ionization (DI) of diatomic molecules driven by circularly polarized laser pulses with different internuclear distances (R). The results show that the DI mechanism changes from sequential double ionization (SDI) to nonsequential double ionization (NSDI) as the internuclear distance increases. In SDI range, the structure of the electron momentum distribution changes seriously as R increases, which indicates the sensitive dependence of the release times of the two electrons on R. For NSDI, because of the circular polarization, the ionization of the second electron is not through the well-known recollision process but through a process where the first electron ionizes over the inner potential barrier of the molecule, moves directly towards the other nucleus, and kicks out the second electron.

  11. Auger electron angular distribution of double core-hole states in the molecular reference frame.

    PubMed

    Cryan, James P; Glownia, J M; Andreasson, J; Belkacem, A; Berrah, N; Blaga, C I; Bostedt, C; Bozek, J; Buth, C; DiMauro, L F; Fang, L; Gessner, O; Guehr, M; Hajdu, J; Hertlein, M P; Hoener, M; Kornilov, O; Marangos, J P; March, A M; McFarland, B K; Merdji, H; Petrović, V S; Raman, C; Ray, D; Reis, D; Tarantelli, F; Trigo, M; White, J L; White, W; Young, L; Bucksbaum, P H; Coffee, R N

    2010-08-20

    The Linac Coherent Light Source free electron laser is a source of high brightness x rays, 2×10(11) photons in a ∼5 fs pulse, that can be focused to produce double core vacancies through rapid sequential ionization. This enables double core vacancy Auger electron spectroscopy, an entirely new way to study femtosecond chemical dynamics with Auger electrons that probe the local valence structure of molecules near a specific atomic core. Using 1.1 keV photons for sequential x-ray ionization of impulsively aligned molecular nitrogen, we observed a rich single-site double core vacancy Auger electron spectrum near 413 eV, in good agreement with ab initio calculations, and we measured the corresponding Auger electron angle dependence in the molecular frame.

  12. Auger Electron Angular Distribution of Double Core-Hole States in the Molecular Reference Frame

    NASA Astrophysics Data System (ADS)

    Cryan, James P.; Glownia, J. M.; Andreasson, J.; Belkacem, A.; Berrah, N.; Blaga, C. I.; Bostedt, C.; Bozek, J.; Buth, C.; Dimauro, L. F.; Fang, L.; Gessner, O.; Guehr, M.; Hajdu, J.; Hertlein, M. P.; Hoener, M.; Kornilov, O.; Marangos, J. P.; March, A. M.; McFarland, B. K.; Merdji, H.; Petrović, V. S.; Raman, C.; Ray, D.; Reis, D.; Tarantelli, F.; Trigo, M.; White, J. L.; White, W.; Young, L.; Bucksbaum, P. H.; Coffee, R. N.

    2010-08-01

    The Linac Coherent Light Source free electron laser is a source of high brightness x rays, 2×1011 photons in a ˜5fs pulse, that can be focused to produce double core vacancies through rapid sequential ionization. This enables double core vacancy Auger electron spectroscopy, an entirely new way to study femtosecond chemical dynamics with Auger electrons that probe the local valence structure of molecules near a specific atomic core. Using 1.1 keV photons for sequential x-ray ionization of impulsively aligned molecular nitrogen, we observed a rich single-site double core vacancy Auger electron spectrum near 413 eV, in good agreement with ab initio calculations, and we measured the corresponding Auger electron angle dependence in the molecular frame.

  13. Tunable few-electron double quantum dots with integrated charge read-out

    NASA Astrophysics Data System (ADS)

    Elzerman, J. M.; Hanson, R.; Greidanus, J. S.; Willems van Beveren, L. H.; De Franceschi, S.; Vandersypen, L. M. K.; Tarucha, S.; Kouwenhoven, L. P.

    2004-11-01

    We report on the realization of few-electron double quantum dots defined in a two-dimensional electron gas by means of surface gates on top of a GaAs/AlGaAs heterostructure. Two quantum point contacts (QPCs) are placed in the vicinity of the double quantum dot and serve as charge detectors. These enable determination of the number of conduction electrons on each dot. This number can be reduced to zero, while still allowing transport measurements through the double dot. The coupling between the two dots can be controlled even in the few-electron regime. Microwave radiation is used to pump an electron from one dot to the other by absorption of a single photon. The experiments demonstrate that this quantum dot circuit can serve as a good starting point for a scalable spin-qubit system.

  14. Many-body correlations of QRPA in nuclear matrix elements of double-beta decay

    SciTech Connect

    Terasaki, J.

    2015-10-28

    We present two new ideas on the quasiparticle random-phase approximation (QRPA) approach for calculating nuclear matrix elements of double-beta decay. First, it is necessary to calculate overlaps of the QRPA states obtained on the basis of the ground states of different nuclei. We calculate this overlap using quasiboson vacua as the QRPA ground states. Second, we show that two-particle transfer paths are possible to use for the calculation under the closure approximation. A calculation is shown for {sup 150}Nd→{sup 150}Sm using these two new ideas, and their implication is discussed.

  15. Double-resonance 14N nuclear-magnetic-resonance probe for single-crystal studies

    NASA Astrophysics Data System (ADS)

    Naito, Akira; McDowell, Charles A.

    1989-06-01

    A double-resonance 14N nuclear-magnetic-resonance (NMR) probe suitable for single-crystal studies is described. The 14N and 1H sample coils are wound as coaxial solenoids and used instead of a doubly tuned single coil to tune over the required frequency range of the 14N channel. The choice of materials for the probe body and the wire size for the sample and impedance matching coils were chosen carefully to minimize spurious ringing phenomena, which is troublesome in probe designs for solid-state NMR. The probe has a very accurate goniometer since the resolution of 14N NMR signals is high.

  16. Dynamic nuclear polarization-enhanced 1H–13C double resonance NMR in static samples below 20 K

    PubMed Central

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

    2012-01-01

    We demonstrate the feasibility of one-dimensional and two-dimensional 1H–13C double resonance NMR experiments with dynamic nuclear polarization (DNP) at 9.4 T and temperatures below 20 K, including both 1H–13C cross-polarization and 1H decoupling, and discuss the effects of polarizing agent type, polarizing agent concentration, temperature, and solvent deuteration. We describe a two-channel low-temperature DNP/NMR probe, capable of carrying the radio-frequency power load required for 1H–13C cross-polarization and high-power proton decoupling. Experiments at 8 K and 16 K reveal a significant T2 relaxation of 13C, induced by electron spin flips. Carr–Purcell experiments and numerical simulations of Carr–Purcell dephasing curves allow us to determine the effective correlation time of electron flips under our experimental conditions. The dependence of the DNP signal enhancement on electron spin concentration shows a maximum near 80 mM. Although no significant difference in the absolute DNP enhancements for triradical (DOTOPA-TEMPO) and biradical (TOTAPOL) dopants was found, the triradical produced greater DNP build-up rates, which are advantageous for DNP experiments. Additionally the feasibility of structural measurements on 13C-labeled biomolecules was demonstrated with a two-dimensional 13C–13C exchange spectrum of selectively 13C-labeled β-amyloid fibrils. PMID:22743540

  17. Nuclear matrix element of neutrinoless double-β decay: Relativity and short-range correlations

    NASA Astrophysics Data System (ADS)

    Song, L. S.; Yao, J. M.; Ring, P.; Meng, J.

    2017-02-01

    Background:The discovery of neutrinoless double-β (0 ν β β ) decay would demonstrate the nature of neutrinos, have profound implications for our understanding of matter-antimatter mystery, and solve the mass hierarchy problem of neutrinos. The calculations for the nuclear matrix elements M0 ν of 0 ν β β decay are crucial for the interpretation of this process. Purpose: We study the effects of relativity and nucleon-nucleon short-range correlations on the nuclear matrix elements M0 ν by assuming the mechanism of exchanging light or heavy neutrinos for the 0 ν β β decay. Methods:The nuclear matrix elements M0 ν are calculated within the framework of covariant density functional theory, where the beyond-mean-field correlations are included in the nuclear wave functions by configuration mixing of both angular-momentum and particle-number projected quadrupole deformed mean-field states. Results: The nuclear matrix elements M0 ν are obtained for ten 0 ν β β -decay candidate nuclei. The impact of relativity is illustrated by adopting relativistic or nonrelativistic decay operators. The effects of short-range correlations are evaluated. Conclusions: The effects of relativity and short-range correlations play an important role in the mechanism of exchanging heavy neutrinos though the influences are marginal for light neutrinos. Combining the nuclear matrix elements M0 ν with the observed lower limits on the 0 ν β β -decay half-lives, the predicted strongest limits on the effective masses are ||<0.06 eV for light neutrinos and | |-1>3.065 ×108GeV for heavy neutrinos.

  18. 78 FR 71675 - Update of the Office of Nuclear Reactor Regulation's Electronic Operating Reactor Correspondence

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-29

    ... From the Federal Register Online via the Government Publishing Office NUCLEAR REGULATORY COMMISSION Update of the Office of Nuclear Reactor Regulation's Electronic Operating Reactor Correspondence... Regulatory Commission. Michele G. Evans, Director, Division of Operating Reactor Licensing, Office of...

  19. Electron bilayers in an undoped Si/SiGe double-quantum-well heterostructure

    NASA Astrophysics Data System (ADS)

    Lu, Tzu-Ming; Laroche, Dominique; Huang, Shih-Hsien; Nielsen, Erik; Chuang, Yen; Li, Jiun-Yun; Liu, Cheewee

    We report the design, fabrication, and the magneto-transport study of an undoped Si/SiGe double quantum well heterostructure. We show that employing asymmetric quantum wells for our single-side-gated devices allows us to observe a cross-over from single-layer-like to bi-layer-llike behavior in the mobility-density dependence. We also observe an integer quantum Hall state at filling factor ν = 2, which is expected to arise from inter-layer effects for Si electrons. This state could be due to either inter-layer coherence, or the symmetric-antisymmetric tunneling gap. This work has been supported by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy (DOE). 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.

  20. In situ transmission electron microscopy of electron-beam induced damage process in nuclear grade graphite

    NASA Astrophysics Data System (ADS)

    Karthik, C.; Kane, J.; Butt, D. P.; Windes, W. E.; Ubic, R.

    2011-05-01

    Atomic level processes involved in the swelling and crack-closing in nuclear grade graphite under electron irradiation have been observed in real-time using transmission electron microscopy. Noise-filtered lattice images show the formation of vacancy loops, interstitial loops and resulting dislocations with unprecedented clarity. The dislocation dipoles formed via vacancy loops were found to undergo climb resulting in extra basal planes. Concurrent EELS studies showed a reduction in the atomic density because of the breakage of hexagonal carbon rings. The formation of new basal planes via dislocation climb in addition to the bending/breaking of basal planes leads to swelling and closing of micro-cracks.

  1. Nuclear-polarization correction to the bound-electron g factor in heavy hydrogenlike ions.

    PubMed

    Nefiodov, A V; Plunien, G; Soff, G

    2002-08-19

    The influence of nuclear polarization on the bound-electron g factor in heavy hydrogenlike ions is investigated. Numerical calculations are performed for the K- and L-shell electrons taking into account the dominant virtual nuclear excitations. This determines the ultimate limit for tests of QED utilizing measurements of the bound-electron g factor in highly charged ions.

  2. Valence-electron correlation in the double K -shell photoionization of atomic beryllium

    NASA Astrophysics Data System (ADS)

    Saha, Hari P.

    2017-06-01

    We extended the multiconfiguration Hartree-Fock (MCHF) + effective charge (EFC) method for double photoionization of atoms and investigated the effect of valence-electron correlation in the double K -shell photoionization of atomic beryllium. We used the MCHF method, which accounts for electron correlations, to calculate the initial-state wave function. The wave functions for the two continuum electrons in the final state are calculated in the angle-dependent EFC approximation. The actual interaction potential between the two final-state continuum electrons is approximated by the EFC, which is determined variationally. We studied the effect of valence shell electron correlation on the K -shell double photoionization of beryllium for both equal and unequal sharing of excess photon energies at four fixed scattered electron directions in order to study the effects near the double K -shell ionization threshold. We found considerable effect of valence shell correlation in the triple-differential cross section for double photoionization of the beryllium atom at each of the excess photon energies.

  3. Unipolar Complementary Circuits Using Double Electron Layer Tunneling Tansistors

    SciTech Connect

    Blount, M.A.; Hafich, M.J.; Moon, J.S.; Reno, J.L.; Simmons, J.A.

    1998-10-19

    We demonstrate unipolar complementary circuits consisting of a pair of resonant tunneling transistors based on the gate control of 2D-2D interlayer tunneling, where a single transistor - in addition to exhibiting a welldefined negative-differential-resistance can be operated with either positive or negative transconductance. Details of the device operation are analyzed in terms of the quantum capacitance effect and band-bending in a double quantum well structure, and show good agreement with experiment. Application of resonant tunneling complementary logic is discussed by demonstrating complementary static random access memory using two devices connected in series.

  4. Large amplitude double layers in a positively charged dusty plasma with nonthermal electrons

    SciTech Connect

    Djebli, M.; Marif, H.

    2009-06-15

    A pseudopotential approach is used to investigate large amplitude dust-acoustic solitary structures for a plasma composed of positively charged dust, cold electrons, and nonthermal hot electrons. Numerical investigation for an adiabatic situation is conducted to examine the existence region of the wave. The negative potential of the double layers is found to be dependent on nonthermal parameters, Mach number, and electrons temperature. A range of the nonthermal parameters values exists for which two possible double layers for the same plasma mix at different Mach numbers and with significant different amplitudes. The present model is used to investigate localized structures in the lower-altitude Earth's ionosphere.

  5. Retrocausation acting in the single-electron double-slit interference experiment

    NASA Astrophysics Data System (ADS)

    Hokkyo, Noboru

    The single electron double-slit interference experiment is given a time-symmetric interpretation and visualization in terms of the intermediate amplitude of transition between the particle source and the detection point. It is seen that the retarded (causal) amplitude of the electron wave expanding from the source shows an advanced (retrocausal) bifurcation and merging in passing through the double-slit and converges towards the detection point as if guided by the advanced (retrocausal) wave from the detected electron. An experiment is proposed to confirm the causation-retrocausation symmetry of the electron behavior by observing the insensitivity of the interference pattern to non-magnetic obstacles placed in the shadows of the retarded and advanced waves appearing on the rear and front sides of the double-slit.

  6. Analytical distance distributions in systems of spherical symmetry with applications to double electron-electron resonance

    NASA Astrophysics Data System (ADS)

    Kattnig, Daniel R.; Hinderberger, Dariush

    2013-05-01

    Based on a simple geometrical approach, we derive analytical expression of the probability density functions (pdfs) of distance of probe molecules distributed homogeneously in spherical aggregates with shell structure. These distance distributions can be utilized in the investigation of double electron-electron resonance (DEER) data of disordered nanometer-sized spin clusters. Structural insights and geometrical parameters of the aggregates can be extracted by modeling the DEER time traces based on the analytical pdfs. This approach is efficient and avoids difficulties of the model-free solution of the inverse problem that are related to multi-spin effects, limited excitation bandwidth, bias introduced by the regularization scheme, or ambiguity resulting from broad distance distributions. The derived pdfs can serve as building blocks, from which the distance distributions in arbitrary spherically symmetric objects can be assembled. The scenario of the pumped species being chemically distinct from the observed species is covered as well as that of a single type of probe molecules. We demonstrate the merits of analytical distance distributions by studying the distribution of three different spin probes in SDS micelles. By simultaneously analyzing DEER data corresponding to different spin probe concentrations, the distribution of the spin probes over the micelle can be determined. Employing Bayesian inference it is found that for all probes studied, a spherical shell model is most appropriate among the studied models and by orders of magnitude more likely than a homogeneous distribution in a ball. This statement also applies to probes that are deemed nonpolar. We envisage that the spin probe distributions in disordered soft and hard matter systems can now be quantified using DEER spectroscopy with greater precision and reduced ambiguity.

  7. THE n-DISTRIBUTION OF ELECTRONS AND DOUBLE LAYERS IN THE ELECTRON-BEAM-RETURN-CURRENT SYSTEM OF SOLAR FLARES

    SciTech Connect

    Karlicky, Marian

    2012-05-01

    We investigate processes in the electron-beam-return-current system in the impulsive phase of solar flares to answer a question about the formation of the n-electron distribution detected in this phase of solar flares. An evolution of the electron-beam-return-current system with an initial local density depression is studied using a three-dimensional electromagnetic particle-in-cell model. In the system the strong double layer is formed. Its electric field potential increases with the electron beam flux. In this electric field potential, the electrons of background plasma are strongly accelerated and propagate in the return-current direction. The high-energy part of their distribution at the high-potential side of the strong double layer resembles that of the n-distribution. Thus, the detection of the n-distributions, where a form of the high-energy part of the distribution is the most important, can indicate the presence of strong double layers in solar flares. The similarity between processes in solar flare loops and those in the downward current region of the terrestrial aurora, where the double layers were observed by FAST satellite, supports this idea.

  8. On the threshold energization of radiation belt electrons by double layers.

    NASA Astrophysics Data System (ADS)

    Dimmock, A. P.; Osmane, A.; Pulkkinen, T. I.

    2014-12-01

    Recent in situ electric field measurements by the Van Allen Probes in the radiation belts have revealed the existence and ubiquitous presence of double layers [Mozer et al. Phys. Rev. Lett., 2013]. Encounters with double layers during 1 minute burst mode intervals were both common and indicative of large cumulative potential drops. With electric fields averaging 20 mV/m, and sometimes reaching as high as 100 mV/m, observed double layers have been suggested as possible accelerators of radiation belt electrons and generators of a seed population of 100 keV. Using a Hamiltonian approach we quantify the energization threshold of electrons interacting with radiation belts' double layers analytically and numerically. We find that double layers with electric field amplitude δE ranging between 10-100 mV/m and spatial scales of the order of few Debye lengths are very efficient in energizing electrons with initial velocities v ≤ vthermal≈3000 km/s to 1 keV levels, but are unable to energize electrons with energies E ≥ 10 keV. Our results therefore indicate that the localized electric field associated with the double layers are unlikely to generate a seed population of 100 keV necessary for a plethora of relativistic acceleration mechanisms and additional transport to higher energetic levels.

  9. Two-dimensional quasi-double-layers in two-electron-temperature, current-free plasmas

    SciTech Connect

    Merino, Mario; Ahedo, Eduardo

    2013-02-15

    The expansion of a plasma with two disparate electron populations into vacuum and channeled by a divergent magnetic nozzle is analyzed with an axisymmetric model. The purpose is to study the formation and two-dimensional shape of a current-free double-layer in the case when the electric potential steepening can still be treated within the quasineutral approximation. The properties of this quasi-double-layer are investigated in terms of the relative fraction of the high-energy electron population, its radial distribution when injected into the nozzle, and the geometry and intensity of the applied magnetic field. The two-dimensional double layer presents a curved shape, which is dependent on the natural curvature of the equipotential lines in a magnetically expanded plasma and the particular radial distribution of high-energy electrons at injection. The double layer curvature increases the higher the nozzle divergence is, the lower the magnetic strength is, and the more peripherally hot electrons are injected. A central application of the study is the operation of a helicon plasma thruster in space. To this respect, it is shown that the curvature of the double layer does not increment the thrust, it does not modify appreciably the downstream divergence of the plasma beam, but it increases the magnetic-to-pressure thrust ratio. The present study does not attempt to cover current-free double layers involving plasmas with multiple populations of positive ions.

  10. Small amplitude double layers in a warm electronegative plasma with trapped kappa distributed electrons

    NASA Astrophysics Data System (ADS)

    Shan, Shaukat Ali; Imtiaz, Nadia

    2017-06-01

    We employ quasipotential analysis to derive the Sagdeev potential which accounts for the effect of electron trapping in a warm electronegative plasma with κ-distributed electrons. The trapped electron density is truncated to some finite order of the electrostatic potential Φ. This consequently leads to an extended KdV equation which gives rise to small amplitude double layers (SIADLs). The effects of various plasma parameters, e.g., superthermality index, the electron trapping efficiency, the mass ratio of negative to positive ion, the number density ratio of electron to positive ion, and temperature ratio of positive ion to electron on the small amplitude ion acoustic double layers (SIADLs), have been investigated. It has been found that these parameters have a significant modifying role in the SIADLs.

  11. Nuclear Excitation by Electronic Transition of U-235

    NASA Astrophysics Data System (ADS)

    Chodash, Perry Adam

    Nuclear excitation by electronic transition (NEET) is a rare nuclear excitation that is theorized to occur in numerous isotopes. One isotope in particular, U-235, has been studied several times over the past 40 years and NEET of U-235 has never been conclusively observed. These past experiments generated conflicting results with some experiments claiming to observe NEET of U-235 and others setting limits for the NEET rate. This dissertation discusses the latest attempt to measure NEET of U-235. If NEET of U-235 were to occur, U-235m would be created. U-235m decays by internal conversion with a decay energy of 76 eV and a half-life of 26 minutes. A pulsed Nd:YAG laser operating at 1064 nm with a pulse energy of 789 mJ and a pulse width of 9 ns was used to generate a uranium plasma. The plasma was captured on a catcher plate and electrons emitted from the catcher plate were accelerated and focused onto a microchannel plate detector. A decay of 26 minutes would suggest the creation of U-235m and the possibility that NEET occurred. However, measurements performed using a variety of uranium targets spanning depleted uranium up to 99.4% enriched uranium did not observe a 26 minute decay. Numerous other decays were observed with half-lives ranging from minutes up to hundreds of minutes. While NEET of U-235 was not observed during this experiment, an upper limit for the NEET rate of U-235 was determined. In addition, explanations for the conflicting results from previous experiments are given. Based on the results of this experiment and the previous experiments looking for NEET of U-235, it is likely that NEET of U-235 has never been observed.

  12. Double decimation and sliding vacua in the nuclear many-body system

    NASA Astrophysics Data System (ADS)

    Brown, G. E.; Rho, Mannque

    2004-06-01

    We propose that effective field theories for nuclei and nuclear matter comprise of “double decimation”: (1) the chiral symmetry decimation (CSD) and (2) Fermi liquid decimation (FLD). The Brown-Rho scaling recently identified as the parametric dependence intrinsic in the “vector manifestation” of hidden local symmetry theory of Harada and Yamawaki results from the first decimation. This scaling governs dynamics down to the scale at which the Fermi surface is formed as a quantum critical phenomenon. The next decimation to the top of the Fermi sea where standard nuclear physics is operative makes up the FLD. Thus, nuclear dynamics are dictated by two fixed points, namely, the vector manifestation fixed point and the Fermi liquid fixed point. It has been a prevalent practice in nuclear physics community to proceed with the second decimation only, assuming density-independent masses, without implementing the first, CSD. We show why most nuclear phenomena can be reproduced by theories using either density-independent, or density-dependent masses, a grand conspiracy of nature that is an aspect that could be tied to the Cheshire Cat phenomenon in hadron physics. We identify what is left out in the FLD that does not incorporate the CSD. Experiments such as the dilepton production in relativistic heavy ion reactions, which are specifically designed to observe effects of dropping masses, could exhibit large effects from the reduced masses. However, they are compounded with effects that are not directly tied to chiral symmetry. We discuss a recent STAR/RHIC observation where BR scaling can be singled out in a pristine environment.

  13. Nuclear-Structure Data Relevant to Neutinoless-Double-Beta-Decay Matrix Elements

    NASA Astrophysics Data System (ADS)

    Kay, Benjamin

    2015-10-01

    An observation of neutrinoless double beta decay is one of the most exciting prospects in contemporary physics. It follows that calculations of the nuclear matrix elements for this process are of high priority. The change in the wave functions between the initial and final states of the neutrinoless-double-beta-decay candidates 76Ge-->76Se, 100Mo-->100Ru, 130Te-->130Xe, and 136Xe-->136Ba have been studied with transfer reactions. The data are focused on the change in the occupancies of the valence orbitals in the ground states as two neutrons decay into two protons. The results set a strict constraint on any theoretical calculations describing this rearrangement and thus on the magnitude of the nuclear matrix elements for this process, which currently exhibit uncertainties at the factor of 2-4 level. Prior to these measurements there were limited experimental data were available A = 76 and 100 systems, and very limited data for the A = 130 and 136 systems, in a large part due to the gaseous Xe isotopes involved. The uncertainties on most of these data are estimated to range from 0.1-0.3 nucleons. The program started with the A = 76 system, with subsequent calculations, modified to reproduce the experimental occupancies, exhibiting a significant reduction in the discrepancy between various models. New data are available for the A = 100 , 130, and 136 systems. I review the program, making detailed comparisons between the latest theoretical calculations and the experimental data where available. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract Number DE-AC02-06CH11357.

  14. Nuclear Quantum Effects on Aqueous Electron Attachment and Redox Properties.

    PubMed

    Rybkin, Vladimir V; VandeVondele, Joost

    2017-04-06

    Nuclear quantum effects (NQEs) on the reduction and oxidation properties of small aqueous species (CO2, HO2, and O2) are quantified and rationalized by first-principles molecular dynamics and thermodynamic integration. Vertical electron attachment, or electron affinity, and detachment energies (VEA and VDE) are strongly affected by NQEs, decreasing in absolute value by 0.3 eV going from a classical to a quantum description of the nuclei. The effect is attributed to NQEs that lessen the solvent response upon oxidation/reduction. The reduction of solvent reorganization energy is expected to be general for small solutes in water. In the thermodynamic integral that yields the free energy of oxidation/reduction, these large changes enter with opposite sign, and only a small net effect (0.1 eV) remains. This is not obvious for CO2, where the integrand is strongly influenced by NQEs due to the onset of interaction of the reduced orbital with the conduction band of the liquid during thermodynamic integration. We conclude that NQEs might not have to be included in the computation of redox potentials, unless high accuracy is needed, but are important for VEA and VDE calculations.

  15. Exact factorization of the full electron-nuclear wavefunction: A quantum-classical study

    NASA Astrophysics Data System (ADS)

    Agostini, Federica; Abedi, Ali; Gross, Eberhard

    2012-02-01

    It was recently shown in [1] that the solution of the time-dependent Schr"odinger equation for a molecular system can be exactly factorized to an electronic and a nuclear contribution. In [1], the authors derived exact equations of motion for the coupled evolution of the electronic and nuclear wavefunctions, which are a good starting point to develop approximations, systematically. Based on this exact decomposition of the electron and nuclear motion, we present a quantum-classical scheme for the coupled electron-nuclear dynamics. Nuclear degrees of freedom evolve along a classical trajectory, affecting electronic motion and inducing quantum transitions, which in turn alter nuclear dynamics. Applications of the proposed method to model systems will be presented.[4pt] [1] A. Abedi, N.T. Maitra and E.K.U. Gross, Phys. Rev. Lett. 105 123002 (2010).

  16. Coherent state transfer between an electron and nuclear spin in (15)N@C(60).

    PubMed

    Brown, Richard M; Tyryshkin, Alexei M; Porfyrakis, Kyriakos; Gauger, Erik M; Lovett, Brendon W; Ardavan, Arzhang; Lyon, S A; Briggs, G Andrew D; Morton, John J L

    2011-03-18

    Electron spin qubits in molecular systems offer high reproducibility and the ability to self-assemble into larger architectures. However, interactions between neighboring qubits are "always on," and although the electron spin coherence times can be several hundred microseconds, these are still much shorter than typical times for nuclear spins. Here we implement an electron-nuclear hybrid scheme which uses coherent transfer between electron and nuclear spin degrees of freedom in order to both effectively turn on or off interqubit coupling mediated by dipolar interactions and benefit from the long nuclear spin decoherence times (T(2n)). We transfer qubit states between the electron and (15)N nuclear spin in (15)N@C(60) with a two-way process fidelity of 88%, using a series of tuned microwave and radio frequency pulses and measure a nuclear spin coherence lifetime of over 100 ms.

  17. Computer-automated tuning of semiconductor double quantum dots into the single-electron regime

    SciTech Connect

    Baart, T. A.; Vandersypen, L. M. K.; Eendebak, P. T.; Reichl, C.; Wegscheider, W.

    2016-05-23

    We report the computer-automated tuning of gate-defined semiconductor double quantum dots in GaAs heterostructures. We benchmark the algorithm by creating three double quantum dots inside a linear array of four quantum dots. The algorithm sets the correct gate voltages for all the gates to tune the double quantum dots into the single-electron regime. The algorithm only requires (1) prior knowledge of the gate design and (2) the pinch-off value of the single gate T that is shared by all the quantum dots. This work significantly alleviates the user effort required to tune multiple quantum dot devices.

  18. Valence double ionization electron spectra of CH3F, CH3Cl and CH3I

    NASA Astrophysics Data System (ADS)

    Hult Roos, A.; Eland, J. H. D.; Koulentianos, D.; Squibb, R. J.; Karlsson, L.; Feifel, R.

    2017-07-01

    Valence double ionization electron spectra of the methyl fluoride, methyl chloride, and methyl iodide molecules have been recorded using a time-of-flight photoelectron-photoelectron coincidence technique. The spectra are interpreted by comparison with existing ionization data, Auger spectra, and theoretical calculations. The lowest double ionization energies have been found to be around 35.0 eV, 30.6 eV, and 26.67 eV for CH3F, CH3Cl and CH3I, respectively. These energies are also compared with the predictions and implications of an empirical rule for the lowest double ionization energy in molecules.

  19. Two-dimensional electron-electron double resonance and electron spin-echo study of solute dynamics in smectics

    NASA Astrophysics Data System (ADS)

    Gorcester, Jeff; Rananavare, Shankar B.; Freed, Jack H.

    1989-05-01

    Electron spin-echo (ESE) and two-dimensional electron-electron double resonance (2D ELDOR) experiments have been performed as a function of director orientation and temperature in the smectic A phase of the liquid crystal S2 for the spin-probe PD-tempone(2×10-3 M). Over the entire temperature range studied (288-323 K) we observe significant 2D ELDOR cross peaks only for ΔMI =±1 indicative of 14N spin-relaxation and negligible Heisenberg exchange. From the angular dependent 14N spin-relaxation rates we obtain the dipolar spectral densities at the hyperfine (hf) frequency, whereas from a combination of ESE and 2D ELDOR we obtain the dipolar and Zeeman-dipolar spectral densities at zero frequency. The angular dependent spectral densities were successfully decomposed into their basic components in accordance with theory. The angular dependent spectral densities at the hf frequency are not predicted by a model of anisotropic rotational diffusion in a nematic orienting potential, but are consistent with predictions of a model due to Moro and Nordio of solute rototranslational diffusion in a McMillan-type potential. The angular dependence also indicates that order director fluctuations in the smectic phase are suppressed at frequencies on the order of 10 MHz. An additional contribution to solute reorientation due to cooperative hydrocarbon chain fluctuations is suggested to account for the behavior of the observed spectral densities at zero frequency. An evaluation of the relevance of several other dynamical models to this experimental work is also presented.

  20. Young's double-slit interference observation of hot electrons in semiconductors.

    PubMed

    Furuya, Kazuhito; Ninomiya, Yasunori; Machida, Nobuya; Miyamoto, Yasuyuki

    2003-11-21

    We have carried out Young's double-slit experiment for the hot-electron wave in man-made semiconductor structures with a 25-nm-space double slit in an InP layer buried within GaInAs, a 190-nm-thick GaInAsP hot-electron wave propagation layer, and a collector array of 80 nm pitch. At 4.2 K, dependences of the collector current on the magnetic field were measured and found to agree clearly with the double-slit interference theory. The present results show evidence for the wave front spread of hot electrons using the three-dimensional state in materials, for the first time, and the possibility of using top-down fabrication techniques to achieve quantum wave front control in materials.

  1. Intriguing radical-radical interactions among double-electron oxidized adenine-thymine base pairs

    NASA Astrophysics Data System (ADS)

    Wang, Mei; Zhao, Jing; Zhang, Laibin; Su, Xiyu; Su, Hanlei; Bu, Yuxiang

    2015-01-01

    We present a theoretical investigation of the structural and electronic properties of double-electron oxidized adenine-thymine base pair as well as its deprotonated Watson-Crick derivatives. Double-electron oxidation can destabilize the AT unit, leading to a barrier-hindered metastable A+T+ state with a dissociation channel featuring negative dissociation energy. This unusual energetic phenomenon originates from the competition of electrostatic repulsion and attractively hydrogen-bonding interaction co-existing between Arad + and Trad +. The associated double-proton-transfer process is also explored, suggesting a possible two-step mechanism. Magnetic coupling interactions of various diradical structures are controlled by both intra- and inter-molecular interactions.

  2. Single- and double-electron detachment from H- in collisions with He

    NASA Astrophysics Data System (ADS)

    Víkor, L.; Sarkadi, L.; Penent, F.; Báder, A.; Pálinkás, J.

    1996-09-01

    The single- and double-electron detachment processes have been studied for 85 keV H- on He collisions measuring the energy spectra of the electrons emitted in forward direction. In the spectrum belonging to the single-electron loss (SEL) the nonresonant part (cusp) has been resolved from the resonant part [lines from the (2s2p)1Po shape resonance of H-]. The ratio of the integrated yield of the double-electron loss (DEL) to that of SEL was found to be 0.36+/-0.02. The yield of the cusp in the SEL spectrum was found to be surprisingly small, only (70+/-20)% of the yield of the cusp in the DEL spectrum. The formation of the cusp in SEL is interpreted as a result of dipolar interaction between the electron and the outgoing H0 atom.

  3. Double-electron recombination in high-order-harmonic generation driven by spatially inhomogeneous fields

    NASA Astrophysics Data System (ADS)

    Chacón, Alexis; Ciappina, Marcelo F.; Lewenstein, Maciej

    2016-10-01

    We present theoretical studies of high-order harmonic generation (HHG) driven by plasmonic fields in two-electron atomic systems. Comparing the single- and two-electron active approximation models of the hydrogen negative ion, we provide strong evidence that a nonsequential double-electron recombination mechanism appears to be mainly responsible for the HHG cutoff extension. Our analysis is carried out by means of a reduced one-dimensional numerical integration of the two-electron time-dependent Schrödinger equation, and on investigations of the classical electron trajectories, resulting from the Newton's equation of motion. Additional comparisons between the hydrogen negative ion and the helium atom suggest that the double recombination process depends distinctly on the atomic target. Our research paves the way to the understanding of strong field processes in multielectronic systems driven by spatially inhomogeneous fields.

  4. Angular distributions in the double ionization of DNA bases by electron impact

    NASA Astrophysics Data System (ADS)

    Khelladi, M. F.; Mansouri, A.; Dal Cappello, C.; Charpentier, I.; Hervieux, P. A.; Ruiz-Lopez, M. F.; Roy, A. C.

    2016-11-01

    Ab initio calculations of the five-fold differential cross sections for electron-impact double ionization of thymine, cytosine, adenine and guanine are performed in the first Born approximation for an incident energy close to 5500 eV. The wavefunctions of the DNA bases are constructed using the multi-center wave functions from the Gaussian 03 program. These multi-center wave functions are converted into single-center expansions of Slater-type functions. For the final state, the two ejected electrons are described by two Coulomb wave functions. The electron-electron repulsion between the two ejected electrons is also taken into account. Mechanisms of the double ionization are discussed for each case and the best choices of the kinematical parameters are determined for next experiments.

  5. Beam-target double-spin asymmetry in quasielastic electron scattering off the deuteron with CLAS

    NASA Astrophysics Data System (ADS)

    Mayer, M.; Kuhn, S. E.; Adhikari, K. P.; Akbar, Z.; Anefalos Pereira, S.; Asryan, G.; Avakian, H.; Badui, R. A.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Bedlinskiy, I.; Biselli, A. S.; Boiarinov, S.; Bosted, P.; Briscoe, W. J.; Brooks, W. K.; Bültmann, S.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Charles, G.; Chetry, T.; Ciullo, G.; Clark, L.; Colaneri, L.; Cole, P. L.; Compton, N.; Contalbrigo, M.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dupre, R.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fanchini, E.; Fedotov, G.; Fersch, R.; Filippi, A.; Fleming, J. A.; Forest, T. A.; Ghandilyan, Y.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Gleason, C.; Gothe, R. W.; Griffioen, K. A.; Guidal, M.; Guler, N.; Guo, L.; Hakobyan, H.; Hanretty, C.; Hattawy, M.; Hicks, K.; Holtrop, M.; Hughes, S. M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jiang, H.; Keith, C.; Keller, D.; Khachatryan, G.; Khachatryan, M.; Khandaker, M.; Kim, A.; Kim, W.; Klein, A.; Kubarovsky, V.; Lanza, L.; Lenisa, P.; Livingston, K.; MacGregor, I. J. D.; McKinnon, B.; Meekins, D.; Mirazita, M.; Mokeev, V.; Movsisyan, A.; Net, L. A.; Niccolai, S.; Niculescu, G.; Osipenko, M.; Ostrovidov, A. I.; Paremuzyan, R.; Park, K.; Pasyuk, E.; Phelps, W.; Pogorelko, O.; Price, J. W.; Prok, Y.; Puckett, A. J. R.; Ripani, M.; Rizzo, A.; Rosner, G.; Rossi, P.; Sabatié, F.; Schumacher, R. A.; Sharabian, Y. G.; Skorodumina, Iu.; Smith, G. D.; Sokhan, D.; Sparveris, N.; Stankovic, I.; Stepanyan, S.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tian, Ye; Torayev, B.; Ungaro, M.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Weinstein, L. B.; Wood, M. H.; Zachariou, N.; Zhang, J.; Zonta, I.; CLAS Collaboration

    2017-02-01

    Background: The deuteron plays a pivotal role in nuclear and hadronic physics, as both the simplest bound multinucleon system and as an effective neutron target. Quasielastic electron scattering on the deuteron is a benchmark reaction to test our understanding of deuteron structure and the properties and interactions of the two nucleons bound in the deuteron. Purpose: The experimental data presented here can be used to test state-of-the-art models of the deuteron and the two-nucleon interaction in the final state after two-body breakup of the deuteron. Focusing on polarization degrees of freedom, we gain information on spin-momentum correlations in the deuteron ground state (due to the D -state admixture) and on the limits of the impulse approximation (IA) picture as it applies to measurements of spin-dependent observables like spin structure functions for bound nucleons. Information on this reaction can also be used to reduce systematic uncertainties on the determination of neutron form factors or deuteron polarization through quasielastic polarized electron scattering. Method: We measured the beam-target double-spin asymmetry (A||) for quasielastic electron scattering off the deuteron at several beam energies (1.6 -1.7 , 2.5, 4.2, and 5.6 -5.8 GeV ), using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. The deuterons were polarized along (or opposite to) the beam direction. The double-spin asymmetries were measured as a function of photon virtuality Q2(0.13 -3.17 (GeV/c ) 2) , missing momentum (pm=0.0 -0.5 GeV /c ), and the angle between the (inferred) spectator neutron and the momentum transfer direction (θn q). Results: The results are compared with a recent model that includes final-state interactions (FSI) using a complete parametrization of nucleon-nucleon scattering, as well as a simplified model using the plane wave impulse approximation (PWIA). We find overall good agreement with both the PWIA and FSI

  6. Beam-target double-spin asymmetry in quasielastic electron scattering off the deuteron with CLAS

    DOE PAGES

    Mayer, M.; Kuhn, S. E.; Adhikari, K. P.; ...

    2017-02-24

    The deuteron plays a pivotal role in nuclear and hadronic physics, as both the simplest bound multinucleon system and as an effective neutron target. Quasielastic electron scattering on the deuteron is a benchmark reaction to test our understanding of deuteron structure and the properties and interactions of the two nucleons bound in the deuteron. The experimental data presented here can be used to test state-of-the-art models of the deuteron and the two-nucleon interaction in the final state after two-body breakup of the deuteron. Focusing on polarization degrees of freedom, we gain information on spin-momentum correlations in the deuteron ground statemore » (due to the D-state admixture) and on the limits of the impulse approximation (IA) picture as it applies to measurements of spin-dependent observables like spin structure functions for bound nucleons. Information on this reaction can also be used to reduce systematic uncertainties on the determination of neutron form factors or deuteron polarization through quasielastic polarized electron scattering. Furthermore, we measured the beam-target double-spin asymmetry (A||) for quasielastic electron scattering off the deuteron at several beam energies (1.6–1.7, 2.5, 4.2, and 5.6–5.8GeV), using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. The deuterons were polarized along (or opposite to) the beam direction. The double-spin asymmetries were measured as a function of photon virtuality Q2 (0.13–3.17(GeV/c)2), missing momentum (pm=0.0–0.5GeV/c), and the angle between the (inferred) spectator neutron and the momentum transfer direction (θnq). We compare our results with a recent model that includes final-state interactions (FSI) using a complete parametrization of nucleon-nucleon scattering, as well as a simplified model using the plane wave impulse approximation (PWIA). We find overall good agreement with both the PWIA and FSI expectations at low to

  7. Resonant Enhancement of Neutrinoless Double-Electron Capture in Gd152

    NASA Astrophysics Data System (ADS)

    Eliseev, S.; Roux, C.; Blaum, K.; Block, M.; Droese, C.; Herfurth, F.; Kluge, H.-J.; Krivoruchenko, M. I.; Novikov, Yu. N.; Minaya Ramirez, E.; Schweikhard, L.; Shabaev, V. M.; Šimkovic, F.; Tupitsyn, I. I.; Zuber, K.; Zubova, N. A.

    2011-02-01

    In the search for the nuclide with the largest probability for neutrinoless double-electron capture, we have determined the Qγγ value between the ground states of Gd152 and Sm152 by Penning-trap mass-ratio measurements. The new Qγγ value of 55.70(18) keV results in a half-life of 1026yr for a 1 eV neutrino mass. With this smallest half-life among known 0νγγ transitions, Gd152 is a promising candidate for the search for neutrinoless double-electron capture.

  8. The double window for electron beam injection into the flue gas process vessel

    NASA Astrophysics Data System (ADS)

    Chmielewski, A. G.; Zimek, Z.; Panta, P.; Drabik, W.

    1995-06-01

    The double window configuration for electron beam injection into the flue gas treatment process vessel applied in Polish Pilot Plant was described. The effectiveness of such a system was discussed and flue gas dosimetry results were presented. Approximately 64% of total beam power with initial electron energy 0.7 MeV was delivered into the gas phase due to the losses in double window (two 50 μm titanium foils and 70 mm air gap between them) and process vessel definite diameter 1.6 m.

  9. Transition from nonsequential to sequential double ionization in many-electron systems

    NASA Astrophysics Data System (ADS)

    Pullen, Michael G.; Wolter, Benjamin; Wang, Xu; Tong, Xiao-Min; Sclafani, Michele; Baudisch, Matthias; Pires, Hugo; Schröter, Claus Dieter; Ullrich, Joachim; Pfeifer, Thomas; Moshammer, Robert; Eberly, J. H.; Biegert, Jens

    2017-09-01

    Understanding strong-field double ionization of many-electron systems is an important fundamental problem with potential implications for molecular imaging within this regime. Using mid-IR radiation, we unambiguously identify the transition from nonsequential (e , 2 e ) to sequential double ionization in Xe at an intensity below 1014W /c m2 . Ionization from excited orbitals is found to be decisive at low intensities, but we demonstrate that such mechanisms are unimportant in the sequential regime. We utilize these facts to successfully image a molecular dication using laser-induced electron diffraction. This methodology can be used to study molecular dynamics on unprecedented few-femtosecond time scales.

  10. Ion-acoustic double-layers in a magnetized plasma with nonthermal electrons

    SciTech Connect

    Rios, L. A.; Galvão, R. M. O.

    2013-11-15

    In the present work we investigate the existence of obliquely propagating ion-acoustic double layers in magnetized two-electron plasmas. The fluid model is used to describe the ion dynamics, and the hot electron population is modeled via a κ distribution function, which has been proved to be appropriate for modeling non-Maxwellian plasmas. A quasineutral condition is assumed to investigate these nonlinear structures, which leads to the formation of double-layers propagating with slow ion-acoustic velocity. The problem is investigated numerically, and the influence of parameters such as nonthermality is discussed.

  11. Nuclear excitation by electronic transition of 235U

    SciTech Connect

    Chodash, P. A.; Norman, E. B.; Burke, J. T.; Casperson, R. J.; Fisher, S. E.; Holliday, K. S.; Jeffries, J. R.; Wakeling, M. A.; Wilks, S. C.

    2016-03-11

    Here, nuclear excitation by electronic transition (NEET) is a rare nuclear excitation that can occur in isotopes containing a low-lying nuclear excited state. Over the past 40 yr, several experiments have attempted to measure NEET of 235U and those experiments have yielded conflicting results.

  12. Nuclear Excitation by Electronic Transition of U-235

    SciTech Connect

    Chodash, Perry Adam

    2015-07-14

    Nuclear excitation by electronic transition (NEET) is a rare nuclear excitation that is theorized to occur in numerous isotopes. One isotope in particular, 235U, has been studied several times over the past 40 years and NEET of 235U has never been conclusively observed. These past experiments generated con icting results with some experiments claiming to observe NEET of 235U and others setting limits for the NEET rate. This dissertation discusses the latest attempt to measure NEET of 235U. If NEET of 235U were to occur, 235mU would be created. 235mU decays by internal conversion with a decay energy of 76 eV and a half-life of 26 minutes. A pulsed Nd:YAG laser operating at 1064 nm with a pulse energy of 789 mJ and a pulse width of 9 ns was used to generate a uranium plasma. The plasma was captured on a catcher plate and electrons emitted from the catcher plate were accelerated and focused onto a microchannel plate detector. A decay of 26 minutes would suggest the creation of 235mU and the possibility that NEET occurred. However, measurements performed using a variety of uranium targets spanning depleted uranium up to 99.4% enriched uranium did not observe a 26 minute decay. Numerous other decays were observed with half-lives ranging from minutes up to hundreds of minutes. While NEET of 235U was not observed during this experiment, an upper limit for the NEET rate of 235U was determined. In addition, explanations for the con icting results from previous experiments are given. Based on the results of this experiment and the previous experiments looking for NEET of 235U, it is likely that NEET of 235U has never been observed.

  13. MOON for double beta decays and X-rays from WIMP nuclear interactions

    NASA Astrophysics Data System (ADS)

    Ejiri, H.

    2006-07-01

    Neutrino-less double beta decays (0νββ) and direct observation of cold dark matter (DM) are of great interest for studying fundamental properties of neutrinos and weakly interacting massive particles (WIMPs). These are crucial for particle physics and cosmology beyond the standard electro-weak theory. The present seminar in the Erice neutrino school reports briefly (1) the effective neutrino mass studied by 0νββ, (2) the unique features and the present status of MOON (Molybdenum Observatory Of Neutrinos) for high-sensitivity 0νββ studies with 100Mo in the quasi-degenerate and inverted hierarchy regions, and (3) the direct detection of WIMPs by measuring atomic X-rays following inner-shell ionization by WIMPs nuclear interactions. The MOON project is carried out in collaboration with the MOON collaboration, and the X-ray work from WIMPs is done with Ch.C. Moustakidis and J.D. Vergados.

  14. Nuclear counting filter based on a centered Skellam test and a double exponential smoothing

    SciTech Connect

    Coulon, Romain; Kondrasovs, Vladimir; Dumazert, Jonathan; Rohee, Emmanuel; Normand Stephane

    2015-07-01

    Online nuclear counting represents a challenge due to the stochastic nature of radioactivity. The count data have to be filtered in order to provide a precise and accurate estimation of the count rate, this with a response time compatible with the application in view. An innovative filter is presented in this paper addressing this issue. It is a nonlinear filter based on a Centered Skellam Test (CST) giving a local maximum likelihood estimation of the signal based on a Poisson distribution assumption. This nonlinear approach allows to smooth the counting signal while maintaining a fast response when brutal change activity occur. The filter has been improved by the implementation of a Brown's double Exponential Smoothing (BES). The filter has been validated and compared to other state of the art smoothing filters. The CST-BES filter shows a significant improvement compared to all tested smoothing filters. (authors)

  15. Double tuned 23Na 1H nuclear magnetic resonance birdcage for application on mice in vivo

    NASA Astrophysics Data System (ADS)

    Lanz, Titus; Ruff, Jan; Weisser, Alexander; Haase, Axel

    2001-05-01

    The design and the characterization of a double tuned nuclear magnetic birdcage resonator is presented. It abandons quadrature drive and uses the two orthogonal modes of the birdcage for two different frequencies. In order to tune the birdcage to frequencies that are far apart, the number of legs is reduced to only four. This limits the homogeneity of the rf field, but enables the birdcage to be tuned to very different frequencies without further B1 field distortions. Following a brief explanation of the theory of the coil design, a 23Na 1H four leg birdcage for in vivo measurements on mice is presented. The performance of the coil is demonstrated in experiments on both a phantom and a mouse.

  16. Crystallization of an amorphous solid studied by nuclear quadrupole double resonance

    NASA Astrophysics Data System (ADS)

    Seliger, Janez; Žagar, Veselko

    2013-06-01

    Nuclear quadrupole double resonance (NQDR) is proposed as a method for quantitative observation of crystallization of amorphous solids. NQDR signals from amorphous and crystalline parts of a sample may be separated. The intensity I of the NQDR signal from the crystalline part of the sample is proportional to its mass. With increasing time the amorphous phase in the sample transforms to the crystal phase and the intensity I approaches its limiting value I0 corresponding to the complete transformation to the crystal phase. The ratio I/I0 is equal to the mass fraction of the crystalline part of the sample. The same experimental method can be used to determine the mass fraction of a given crystal polymorph in a mixture of crystal polymorphs. As an example we studied crystallization of amorphous nifedipine at 100 °C. The results of the NQDR study are compared to the published results of other studies.

  17. Spin dipole nuclear matrix elements for double beta decay nuclei by charge-exchange reactions

    NASA Astrophysics Data System (ADS)

    Ejiri, H.; Frekers, D.

    2016-11-01

    Spin dipole (SD) strengths for double beta-decay (DBD) nuclei were studied experimentally for the first time by using measured cross sections of (3He, t) charge-exchange reactions (CERs). Then SD nuclear matrix elements (NMEs) {M}α ({{SD}}) for low-lying 2- states were derived from the experimental SD strengths by referring to the experimental α = GT (Gamow-Teller) and α = F (Fermi) strengths. They are consistent with the empirical NMEs M({{SD}}) based on the quasi-particle model with the empirical effective SD coupling constant. The CERs are used to evaluate the SD NME, which is associated with one of the major components of the neutrino-less DBD NME.

  18. First Principles Study of Nuclear Quadrupole Interactions in Single and Double Chain DNA and Solid Nucleobases

    NASA Astrophysics Data System (ADS)

    Das, T. P.; Pink, R. H.; Badu, S. R.; Dubey, Archana; Scheicher, R. H.; Saha, H. P.; Chow, Lee; Huang, M. B.

    2009-03-01

    Nuclear Quadrupole Interactions (NQI) of ^17O, ^14N and ^2H nuclei have been studied for free nucleobases and nucleobases in single strand and double strand DNA and in solid state. Our first-principles investigations were carried out using the Gaussian 2003 set of programs to implement the Hartree-Fock procedure combined with many-body effects included using many-body perturbation theory. As expected for NQI in general, many-body effects are found to be small. Results will be presented for the quadrupole coupling constants (e^2qQ) and asymmetry parameters (η) for the nucleobases in the various environments. Trends in e^2qQ and η in the different environments will be discussed. In the case of the solid nucleobases, comparisons will be made with available experimental data [1] for ^17O nuclei.[3pt] [1] Gang Wu et al., J. Am. Chem. Soc. 124, 1768 (2002)

  19. Plasma parameters controlled by remote electron shower in a double plasma device

    NASA Astrophysics Data System (ADS)

    Mishra, M. K.; Phukan, A.

    2012-07-01

    The principal feature of this experiment is the electron showers consisting of three tungsten wires embedded by the plasma, which are heated up consequently emitting electrons inside the diffused plasma to control the plasma parameters in the discharge section of a double plasma device. These cold electrons emitted by the heated filament are free from maintenance of discharge which is sustained in the source section. The target plasma, where electrons are injected is produced as a result of diffusion from the source section. It is found that, plasma density and plasma potential can be effectively controlled in this way.

  20. Measurement of Low Energy Electronic Recoil Response and Electronic/Nuclear Recoils Discrimination in XENON100

    NASA Astrophysics Data System (ADS)

    Ye, Jingqiang; Xenon Collaboration

    2017-01-01

    The XENON100 detector uses liquid xenon time projection chamber to search for nuclear recoils(NR) caused by hypothetical Weakly Interacting Massive Particles (WIMPs). The backgrounds are mostly electronic recoils(ER), thus it's crucial to distinguish NR from ER. Using high statistical calibration data from tritiated methane, AmBe and other sources in XENON100, the ER/NR discrimination under different electric fields are measured. The Photon yield and recombination fluctuation of low energy electronic recoils under different fields will also be presented and compared to results from NEST and other experiments, which is crucial to understanding the response of liquid xenon detectors in the energy regime of searching dark matter.

  1. Interplay of Electron and Nuclear Spin Noise in n -Type GaAs

    NASA Astrophysics Data System (ADS)

    Berski, Fabian; Hübner, Jens; Oestreich, Michael; Ludwig, Arne; Wieck, A. D.; Glazov, Mikhail

    2015-10-01

    We present spin-noise spectroscopy measurements on an ensemble of donor-bound electrons in ultrapure GaAs:Si covering temporal dynamics over 6 orders of magnitude from milliseconds to nanoseconds. The spin-noise spectra detected at the donor-bound exciton transition show the multifaceted dynamical regime of the ubiquitous mutual electron and nuclear spin interaction typical for III-V-based semiconductor systems. The experiment distinctly reveals the finite Overhauser shift of an electron spin precession at zero external magnetic field and a second contribution around zero frequency stemming from the electron spin components parallel to the nuclear spin fluctuations. Moreover, at very low frequencies, features related with time-dependent nuclear spin fluctuations are clearly resolved making it possible to study the intricate nuclear spin dynamics at zero and low magnetic fields. The findings are in agreement with the developed model of electron and nuclear spin noise.

  2. Coupled electron-nuclear wavepacket dynamics in potassium dimers

    NASA Astrophysics Data System (ADS)

    Braun, Hendrike; Bayer, Tim; Sarpe, Cristian; Siemering, Robert; de Vivie-Riedle, Regina; Baumert, Thomas; Wollenhaupt, Matthias

    2014-06-01

    Recently we have demonstrated control of valence-bond excitation of a molecule due to the interplay of the induced charge oscillation with the precisely tailored phase of the driving laser field (Bayer et al 2013 Phys. Rev. Lett. 110 123003). In this contribution we describe in more detail the two-colour experiment—a control pulse sequence followed by an ionizing probe pulse of a different wavelength. We provide details on the quantum dynamics simulations carried out to reproduce and to analyse the experimental results. The procedure for averaging over the focal intensity distribution in the interaction region and the method for orientation averaging, which are both crucial for the reproduction of our strong-field measurements, are also described in detail. The analysis of the temporal evolution of the expectation values of the wavepackets on the relevant potentials, the induced energetic shifts in the molecule and the modulation in the charge oscillation provides further insights into the interplay of the coupled nuclear-electron dynamics. Because the measured photoelectron spectra reveal the population of the target states we describe the quantum mechanical approach to calculate the photoelectron spectra and rationalize the results using Mulliken's difference potential method.

  3. Dynamic nuclear polarization-enhanced ¹H-¹³C double resonance NMR in static samples below 20 K.

    PubMed

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

    2012-08-01

    We demonstrate the feasibility of one-dimensional and two-dimensional ¹H-¹³C double resonance NMR experiments with dynamic nuclear polarization (DNP) at 9.4 T and temperatures below 20 K, including both ¹H-¹³C cross-polarization and ¹H decoupling, and discuss the effects of polarizing agent type, polarizing agent concentration, temperature, and solvent deuteration. We describe a two-channel low-temperature DNP/NMR probe, capable of carrying the radio-frequency power load required for ¹H-¹³C cross-polarization and high-power proton decoupling. Experiments at 8 K and 16 K reveal a significant T₂ relaxation of ¹³C, induced by electron spin flips. Carr-Purcell experiments and numerical simulations of Carr-Purcell dephasing curves allow us to determine the effective correlation time of electron flips under our experimental conditions. The dependence of the DNP signal enhancement on electron spin concentration shows a maximum near 80 mM. Although no significant difference in the absolute DNP enhancements for triradical (DOTOPA-TEMPO) and biradical (TOTAPOL) dopants was found, the triradical produced greater DNP build-up rates, which are advantageous for DNP experiments. Additionally the feasibility of structural measurements on ¹³C-labeled biomolecules was demonstrated with a two-dimensional ¹³C-¹³C exchange spectrum of selectively ¹³C-labeled β-amyloid fibrils. Copyright © 2012 Elsevier Inc. All rights reserved.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  5. Neutrino propagation in nuclear medium and neutrinoless double-β decay.

    PubMed

    Kovalenko, S; Krivoruchenko, M I; Simkovic, F

    2014-04-11

    We discuss a novel effect in neutrinoless double-β (0νββ) decay related with the fact that its underlying mechanisms take place in the nuclear matter environment. We study the neutrino exchange mechanism and demonstrate the possible impact of nuclear medium via lepton-number-violating (LNV) four-fermion interactions of neutrinos with quarks from a decaying nucleus. The net effect of these interactions is the generation of an effective in-medium Majorana neutrino mass matrix. The enhanced rate of the 0νββ decay can lead to the apparent incompatibility of observations of the 0νββ decay with the value of the neutrino mass determined or restricted by the β-decay and cosmological data. The effective neutrino masses and mixing are calculated for the complete set of the relevant four-fermion neutrino-quark operators. Using experimental data on the 0νββ decay in combination with the β-decay and cosmological data, we evaluate the characteristic scales of these operators: ΛLNV≥2.4  TeV.

  6. Theoretical uncertainties in the nuclear matrix elements of neutrinoless double beta decay: The transition operator

    SciTech Connect

    Menéndez, Javier

    2013-12-30

    We explore the theoretical uncertainties related to the transition operator of neutrinoless double-beta (0νββ) decay. The transition operator used in standard calculations is a product of one-body currents, that can be obtained phenomenologically as in Tomoda [1] or Šimkovic et al. [2]. However, corrections to the operator are hard to obtain in the phenomenological approach. Instead, we calculate the 0νββ decay operator in the framework of chiral effective theory (EFT), which gives a systematic order-by-order expansion of the transition currents. At leading orders in chiral EFT we reproduce the standard one-body currents of Refs. [1] and [2]. Corrections appear as two-body (2b) currents predicted by chiral EFT. We compute the effects of the leading 2b currents to the nuclear matrix elements of 0νββ decay for several transition candidates. The 2b current contributions are related to the quenching of Gamow-Teller transitions found in nuclear structure calculations.

  7. Focus: Two-dimensional electron-electron double resonance and molecular motions: The challenge of higher frequencies

    SciTech Connect

    Franck, John M.; Chandrasekaran, Siddarth; Dzikovski, Boris; Dunnam, Curt R.; Freed, Jack H.

    2015-06-07

    The development, applications, and current challenges of the pulsed ESR technique of two-dimensional Electron-Electron Double Resonance (2D ELDOR) are described. This is a three-pulse technique akin to 2D Exchange Nuclear Magnetic Resonance, but involving electron spins, usually in the form of spin-probes or spin-labels. As a result, it required the extension to much higher frequencies, i.e., microwaves, and much faster time scales, with π/2 pulses in the 2-3 ns range. It has proven very useful for studying molecular dynamics in complex fluids, and spectral results can be explained by fitting theoretical models (also described) that provide a detailed analysis of the molecular dynamics and structure. We discuss concepts that also appear in other forms of 2D spectroscopy but emphasize the unique advantages and difficulties that are intrinsic to ESR. Advantages include the ability to tune the resonance frequency, in order to probe different motional ranges, while challenges include the high ratio of the detection dead time vs. the relaxation times. We review several important 2D ELDOR studies of molecular dynamics. (1) The results from a spin probe dissolved in a liquid crystal are followed throughout the isotropic → nematic → liquid-like smectic → solid-like smectic → crystalline phases as the temperature is reduced and are interpreted in terms of the slowly relaxing local structure model. Here, the labeled molecule is undergoing overall motion in the macroscopically aligned sample, as well as responding to local site fluctuations. (2) Several examples involving model phospholipid membranes are provided, including the dynamic structural characterization of the boundary lipid that coats a transmembrane peptide dimer. Additionally, subtle differences can be elicited for the phospholipid membrane phases: liquid disordered, liquid ordered, and gel, and the subtle effects upon the membrane, of antigen cross-linking of receptors on the surface of plasma membrane

  8. Focus: Two-dimensional electron-electron double resonance and molecular motions: The challenge of higher frequencies

    NASA Astrophysics Data System (ADS)

    Franck, John M.; Chandrasekaran, Siddarth; Dzikovski, Boris; Dunnam, Curt R.; Freed, Jack H.

    2015-06-01

    The development, applications, and current challenges of the pulsed ESR technique of two-dimensional Electron-Electron Double Resonance (2D ELDOR) are described. This is a three-pulse technique akin to 2D Exchange Nuclear Magnetic Resonance, but involving electron spins, usually in the form of spin-probes or spin-labels. As a result, it required the extension to much higher frequencies, i.e., microwaves, and much faster time scales, with π/2 pulses in the 2-3 ns range. It has proven very useful for studying molecular dynamics in complex fluids, and spectral results can be explained by fitting theoretical models (also described) that provide a detailed analysis of the molecular dynamics and structure. We discuss concepts that also appear in other forms of 2D spectroscopy but emphasize the unique advantages and difficulties that are intrinsic to ESR. Advantages include the ability to tune the resonance frequency, in order to probe different motional ranges, while challenges include the high ratio of the detection dead time vs. the relaxation times. We review several important 2D ELDOR studies of molecular dynamics. (1) The results from a spin probe dissolved in a liquid crystal are followed throughout the isotropic → nematic → liquid-like smectic → solid-like smectic → crystalline phases as the temperature is reduced and are interpreted in terms of the slowly relaxing local structure model. Here, the labeled molecule is undergoing overall motion in the macroscopically aligned sample, as well as responding to local site fluctuations. (2) Several examples involving model phospholipid membranes are provided, including the dynamic structural characterization of the boundary lipid that coats a transmembrane peptide dimer. Additionally, subtle differences can be elicited for the phospholipid membrane phases: liquid disordered, liquid ordered, and gel, and the subtle effects upon the membrane, of antigen cross-linking of receptors on the surface of plasma membrane

  9. Focus: Two-dimensional electron-electron double resonance and molecular motions: The challenge of higher frequencies.

    PubMed

    Franck, John M; Chandrasekaran, Siddarth; Dzikovski, Boris; Dunnam, Curt R; Freed, Jack H

    2015-06-07

    The development, applications, and current challenges of the pulsed ESR technique of two-dimensional Electron-Electron Double Resonance (2D ELDOR) are described. This is a three-pulse technique akin to 2D Exchange Nuclear Magnetic Resonance, but involving electron spins, usually in the form of spin-probes or spin-labels. As a result, it required the extension to much higher frequencies, i.e., microwaves, and much faster time scales, with π/2 pulses in the 2-3 ns range. It has proven very useful for studying molecular dynamics in complex fluids, and spectral results can be explained by fitting theoretical models (also described) that provide a detailed analysis of the molecular dynamics and structure. We discuss concepts that also appear in other forms of 2D spectroscopy but emphasize the unique advantages and difficulties that are intrinsic to ESR. Advantages include the ability to tune the resonance frequency, in order to probe different motional ranges, while challenges include the high ratio of the detection dead time vs. the relaxation times. We review several important 2D ELDOR studies of molecular dynamics. (1) The results from a spin probe dissolved in a liquid crystal are followed throughout the isotropic → nematic → liquid-like smectic → solid-like smectic → crystalline phases as the temperature is reduced and are interpreted in terms of the slowly relaxing local structure model. Here, the labeled molecule is undergoing overall motion in the macroscopically aligned sample, as well as responding to local site fluctuations. (2) Several examples involving model phospholipid membranes are provided, including the dynamic structural characterization of the boundary lipid that coats a transmembrane peptide dimer. Additionally, subtle differences can be elicited for the phospholipid membrane phases: liquid disordered, liquid ordered, and gel, and the subtle effects upon the membrane, of antigen cross-linking of receptors on the surface of plasma membrane

  10. Focus: Two-dimensional electron-electron double resonance and molecular motions: The challenge of higher frequencies

    PubMed Central

    Franck, John M.; Dzikovski, Boris; Freed, Jack H.

    2015-01-01

    The development, applications, and current challenges of the pulsed ESR technique of two-dimensional Electron-Electron Double Resonance (2D ELDOR) are described. This is a three-pulse technique akin to 2D Exchange Nuclear Magnetic Resonance, but involving electron spins, usually in the form of spin-probes or spin-labels. As a result, it required the extension to much higher frequencies, i.e., microwaves, and much faster time scales, with π/2 pulses in the 2-3 ns range. It has proven very useful for studying molecular dynamics in complex fluids, and spectral results can be explained by fitting theoretical models (also described) that provide a detailed analysis of the molecular dynamics and structure. We discuss concepts that also appear in other forms of 2D spectroscopy but emphasize the unique advantages and difficulties that are intrinsic to ESR. Advantages include the ability to tune the resonance frequency, in order to probe different motional ranges, while challenges include the high ratio of the detection dead time vs. the relaxation times. We review several important 2D ELDOR studies of molecular dynamics. (1) The results from a spin probe dissolved in a liquid crystal are followed throughout the isotropic → nematic → liquid-like smectic → solid-like smectic → crystalline phases as the temperature is reduced and are interpreted in terms of the slowly relaxing local structure model. Here, the labeled molecule is undergoing overall motion in the macroscopically aligned sample, as well as responding to local site fluctuations. (2) Several examples involving model phospholipid membranes are provided, including the dynamic structural characterization of the boundary lipid that coats a transmembrane peptide dimer. Additionally, subtle differences can be elicited for the phospholipid membrane phases: liquid disordered, liquid ordered, and gel, and the subtle effects upon the membrane, of antigen cross-linking of receptors on the surface of plasma membrane

  11. Shock waves and double layers in electron degenerate dense plasma with viscous ion fluids

    SciTech Connect

    Mamun, A. A.; Zobaer, M. S.

    2014-02-15

    The properties of ion-acoustic shock waves and double layers propagating in a viscous degenerate dense plasma (containing inertial viscous ion fluid, non-relativistic and ultra-relativistic degenerate electron fluid, and negatively charged stationary heavy element) is investigated. A new nonlinear equation (viz. Gardner equation with additional dissipative term) is derived by the reductive perturbation method. The properties of the ion-acoustic shock waves and double layers are examined by the analysis of the shock and double layer solutions of this new equation (we would like to call it “M-Z equation”). It is found that the properties of these shock and double layer structures obtained from this analysis are significantly different from those obtained from the analysis of standard Gardner or Burgers’ equation. The implications of our results to dense plasmas in astrophysical objects (e.g., non-rotating white dwarf stars) are briefly discussed.

  12. Characterization of Nuclear Recoils in High Pressure Xenon Gas: Towards a Simultaneous Search for WIMP Dark Matter and Neutrinoless Double Beta Decay

    SciTech Connect

    Renner, J.; Gehman, V. M.; Goldschmidt, A.; Oliveira, C. A.B.; Nygren, D.

    2015-03-24

    Xenon has recently been the medium of choice in several large scale detectors searching for WIMP dark matter and neutrinoless double beta decay. Though present-day large scale experiments use liquid xenon, the gas phase offers advantages favorable to both types of searches such as improved intrinsic energy resolution and fewer fluctuations in the partition of deposited energy between scintillation and ionization channels. We recently constructed a high pressure xenon gas TPC as a prototype for the NEXT (Neutrino Experiment with a Xenon TPC) neutrinoless double beta decay experiment and have demonstrated the feasibility of 0.5% FWHM energy resolution at the 136Xe double beta Q-value with 3-D tracking capabilities. We now present results from this prototype on the simultaneous observation of scintillation and ionization produced by nuclear recoils at approximately 14 bar pressure. The recoils were produced by neutrons of approximately 2-6 MeV emitted from a radioisotope plutonium-beryllium source, and primary scintillation (S1) and electroluminescent photons produced by ionization (S2) were observed. We discuss the potential of gaseous xenon to distinguish between electron and nuclear recoils through the ratio of these two signals S2/S1. From these results combined with the possibility of using columnar recombination to sense nuclear recoil directionality at high pressures we envision a dual-purpose, ton-scale gaseous xenon detector capable of a combined search for WIMP dark matter and neutrinoless double beta decay. This work has been performed within the context of the NEXT collaboration.

  13. Characterization of Nuclear Recoils in High Pressure Xenon Gas: Towards a Simultaneous Search for WIMP Dark Matter and Neutrinoless Double Beta Decay

    DOE PAGES

    Renner, J.; Gehman, V. M.; Goldschmidt, A.; ...

    2015-03-24

    Xenon has recently been the medium of choice in several large scale detectors searching for WIMP dark matter and neutrinoless double beta decay. Though present-day large scale experiments use liquid xenon, the gas phase offers advantages favorable to both types of searches such as improved intrinsic energy resolution and fewer fluctuations in the partition of deposited energy between scintillation and ionization channels. We recently constructed a high pressure xenon gas TPC as a prototype for the NEXT (Neutrino Experiment with a Xenon TPC) neutrinoless double beta decay experiment and have demonstrated the feasibility of 0.5% FWHM energy resolution at themore » 136Xe double beta Q-value with 3-D tracking capabilities. We now present results from this prototype on the simultaneous observation of scintillation and ionization produced by nuclear recoils at approximately 14 bar pressure. The recoils were produced by neutrons of approximately 2-6 MeV emitted from a radioisotope plutonium-beryllium source, and primary scintillation (S1) and electroluminescent photons produced by ionization (S2) were observed. We discuss the potential of gaseous xenon to distinguish between electron and nuclear recoils through the ratio of these two signals S2/S1. From these results combined with the possibility of using columnar recombination to sense nuclear recoil directionality at high pressures we envision a dual-purpose, ton-scale gaseous xenon detector capable of a combined search for WIMP dark matter and neutrinoless double beta decay. This work has been performed within the context of the NEXT collaboration.« less

  14. Double K -shell vacancy production in the electron capture decay of sup 125 I

    SciTech Connect

    Hindi, M.M.; Kozub, R.L. )

    1992-03-01

    We have measured the probability of double {ital K}-shell vacancy production in the electron capture decay of {sup 125}I to the 35-keV level of {sup 125}Te. The probability was deduced from the number of triple coincidences between the Te hypersatellite and satellite x rays produced in filling the double vacancy, and the subsequent normal x ray accompanying the {ital K} internal conversion of the 35-keV level. The probability of double {ital K}-shell vacancy production per {ital K}-shell electron capture ({ital P}{sub {ital K}{ital K}}) was found to be (1.35{plus minus}0.15){times}10{sup {minus}5}.

  15. Relativistic description of nuclear matrix elements in neutrinoless double-β decay

    NASA Astrophysics Data System (ADS)

    Song, L. S.; Yao, J. M.; Ring, P.; Meng, J.

    2014-11-01

    Background: Neutrinoless double-β (0 ν β β ) decay is related to many fundamental concepts in nuclear and particle physics beyond the standard model. Currently there are many experiments searching for this weak process. An accurate knowledge of the nuclear matrix element for the 0 ν β β decay is essential for determining the effective neutrino mass once this process is eventually measured. Purpose: We report the first full relativistic description of the 0 ν β β decay matrix element based on a state-of-the-art nuclear structure model. Methods: We adopt the full relativistic transition operators which are derived with the charge-changing nucleonic currents composed of the vector coupling, axial-vector coupling, pseudoscalar coupling, and weak-magnetism coupling terms. The wave functions for the initial and final nuclei are determined by the multireference covariant density functional theory (MR-CDFT) based on the point-coupling functional PC-PK1. Correlations beyond the mean field are introduced by configuration mixing of both angular momentum and particle number projected quadrupole deformed mean-field wave functions. Results: The low-energy spectra and electric quadrupole transitions in 150Nd and its daughter nucleus 150Sm are well reproduced by the MR-CDFT calculations. The 0 ν β β decay matrix elements for both the 01+→01+ and 01+→02+ decays of 150Nd are evaluated. The effects of particle number projection, static and dynamic deformations, and the full relativistic structure of the transition operators on the matrix elements are studied in detail. Conclusions: The resulting 0 ν β β decay matrix element for the 01+→01+ transition is 5.60 , which gives the most optimistic prediction for the next generation of experiments searching for the 0 ν β β decay in 150Nd.

  16. Comment on Double K -shell ionization in the electron capture decay of sup 55 Fe''

    SciTech Connect

    Hindi, M.M.; Kozub, R.L. ); Nagy, H.J. ); Schupp, G. )

    1991-11-01

    The corrections made in a recent paper to the published values for double {ital K}-shell ionization in the electron capture decays of {sup 54}Mn and {sup 65}Zn are not applicable to the data from which these values were derived. Attention is called to a recent article that is relevant to the topic of the paper.

  17. Pulsed Electron Double Resonance in Structural Studies of Spin-Labeled Nucleic Acids

    PubMed Central

    Fedorova, O. S.; Tsvetkov, Yu. D.

    2013-01-01

    This review deals with the application of the pulsed electron double resonance (PELDOR) method to studies of spin-labeled DNA and RNA with complicated spatial structures, such as tetramers, aptamers, riboswitches, and three- and four-way junctions. The use of this method for studying DNA damage sites is also described. PMID:23556128

  18. Double copper sheath multiconductor instrumentation cable is durable and easily installed in high thermal or nuclear radiation area

    NASA Technical Reports Server (NTRS)

    Mc Crae, A. W., Jr.

    1967-01-01

    Multiconductor instrumentation cable in which the conducting wires are routed through two concentric copper tube sheaths, employing a compressed insulator between the conductors and between the inner and outer sheaths, is durable and easily installed in high thermal or nuclear radiation area. The double sheath is a barrier against moisture, abrasion, and vibration.

  19. Collisionless Electron-ion Shocks in Relativistic Unmagnetized Jet-ambient Interactions: Non-thermal Electron Injection by Double Layer

    NASA Astrophysics Data System (ADS)

    Ardaneh, Kazem; Cai, Dongsheng; Nishikawa, Ken-Ichi

    2016-08-01

    The course of non-thermal electron ejection in relativistic unmagnetized electron-ion shocks is investigated by performing self-consistent particle-in-cell simulations. The shocks are excited through the injection of a relativistic jet into ambient plasma, leading to two distinct shocks (referred to as the trailing shock and leading shock) and a contact discontinuity. The Weibel-like instabilities heat the electrons up to approximately half of the ion kinetic energy. The double layers formed in the trailing and leading edges then accelerate the electrons up to the ion kinetic energy. The electron distribution function in the leading edge shows a clear, non-thermal power-law tail which contains ˜1% of electrons and ˜8% of the electron energy. Its power-law index is -2.6. The acceleration efficiency is ˜23% by number and ˜50% by energy, and the power-law index is -1.8 for the electron distribution function in the trailing edge. The effect of the dimensionality is examined by comparing the results of three-dimensional simulations with those of two-dimensional simulations. The comparison demonstrates that electron acceleration is more efficient in two dimensions.

  20. Water promoting electron hole transport between tyrosine and cysteine in proteins via a special mechanism: double proton coupled electron transfer.

    PubMed

    Chen, Xiaohua; Ma, Guangcai; Sun, Weichao; Dai, Hongjing; Xiao, Dong; Zhang, Yanfang; Qin, Xin; Liu, Yongjun; Bu, Yuxiang

    2014-03-26

    The proton/electron transfer reactions between cysteine residue (Cys) and tyrosinyl radical (Tyr(•)) are an important step for many enzyme-catalyzed processes. On the basis of the statistical analysis of protein data bank, we designed three representative models to explore the possible proton/electron transfer mechanisms from Cys to Tyr(•) in proteins. Our ab initio calculations on simplified models and quantum mechanical/molecular mechanical (QM/MM) calculations on real protein environment reveal that the direct electron transfer between Cys and Tyr(•) is difficult to occur, but an inserted water molecule can greatly promote the proton/electron transfer reactions by a double-proton-coupled electron transfer (dPCET) mechanism. The inserted H2O plays two assistant roles in these reactions. The first one is to bridge the side chains of Tyr(•) and Cys via two hydrogen bonds, which act as the proton pathway, and the other one is to enhance the electron overlap between the lone-pair orbital of sulfur atom and the π-orbital of phenol moiety and to function as electron transfer pathway. This water-mediated dPCET mechanism may offer great help to understand the detailed electron transfer processes between Tyr and Cys residues in proteins, such as the electron transfer from Cys439 to Tyr730(•) in the class I ribonucleotide reductase.

  1. Measurements of energetic electrons in a Current-Free Double layer

    NASA Astrophysics Data System (ADS)

    Gulbrandsen, Njaal; Fredriksen, Ashild

    2016-09-01

    In inductively coupled helicon sources, current-free double layers (CFDL) can be formed self-consistently without external current forcing. The CFDLs are evidenced by an ion beam formed as a result of a potential drop between the source and the diffusion chamber. The electrons in the double layer play an important role in balancing the ion beam current, but apart from some observations of electron energy probability functions (EEPFs) by means of Langmuir probes, little information has up to now been obtained about the electron population. By means of an inverted retarding field energy analyzer (RFEA) we have measured for the first time the high-energy part of the electron distribution along the radial direction in the diffusion chamber. In this configuration, the RFEA repeller grid is set to a large positive potential, repelling ions and collecting electrons through the discriminator grid. We find a prominent peak of high-energy electrons up to 60 eV at the footprint of the magnetic field lines emerging from the layer near the wall of the source. This coincides with increased electron temperatures and ion densities at this position. Another small but significant distribution of electrons at energies more than 100 eV are observed within the region of the ion beam itself.

  2. Optical Pulse Control of Electron and Nuclear Spins in Quantum Dots

    DTIC Science & Technology

    2009-01-01

    2 T. Kennedy,1 A. Bracker,1 and T. Reinecke1 1Electronics Science and Technology Division 2George Mason University Introduction: Quantum information...decryption of codes with long encryption keys. Electron spins in quantum dots (QDs) are being widely investigated as qubits for storage and processing...field quantum dot la se r pu ls es z x y nuclear spins electron spin + nuclear spin field Sx El lip tic ity ( ra d) Delay time (ps) tim e Sy

  3. In situ correction of the spherical aberration in a double-toroidal electron analyzer

    NASA Astrophysics Data System (ADS)

    Liu, Xiao-Jing; Nicolas, Christophe; Miron, Catalin

    2017-02-01

    In an energy-dispersive electron spectrometer, the electrons with the same kinetic energy but different polar angles fly along different paths and impinge upon the detector at different locations. This behavior materializes the spherical aberration of the electron optics, which deteriorates the focussing quality on the detector, and thus the energy resolution of the instrument. Here, we demonstrate that, in general, the electron time of flight changes monotonically as a function of the polar angle. Combining the impact position on the detector and the time of flight of electrons, the spherical aberration can be corrected and the energy resolution can be significantly improved, 1.5× in the case of our double toroidal analyser. This correction method has a general applicability and can be of interest to experimentalists willing to push further the performances of their electron spectrometers when the time of flight is available.

  4. The adiabatic limit of the exact factorization of the electron-nuclear wave function.

    PubMed

    Eich, F G; Agostini, Federica

    2016-08-07

    We propose a procedure to analyze the relation between the exact factorization of the electron-nuclear wave function and the Born-Oppenheimer approximation. We define the adiabatic limit as the limit of infinite nuclear mass. To this end, we introduce a unit system that singles out the dependence on the electron-nuclear mass ratio of each term appearing in the equations of the exact factorization. We observe how non-adiabatic effects induced by the coupling to the nuclear motion affect electronic properties and we analyze the leading term, connecting it to the classical nuclear momentum. Its dependence on the mass ratio is tested numerically on a model of proton-coupled electron transfer in different non-adiabatic regimes.

  5. Electron correlation in two-photon double ionization of helium from attosecond to FEL pulses

    SciTech Connect

    Collins, Lee

    2009-01-01

    We investigate the role of electron correlation in the two-photon double ionization of helium for ultrashort pulses in the extreme ultraviolet (XUV) regime with durations ranging from a hundred attoseconds to a few femtoseconds. We perform time-dependent ab initio calculations for pulses with mean frequencies in the so-called 'sequential' regime ({Dirac_h}{omega} > 54.4 eV). Electron correlation induced by the time correlation between emission events manifests itself in the angular distribution of the ejected electrons, which strongly depends on the energy sharing between them. We show that for ultrashort pulses two-photon double ionization probabilities scale non-uniformly with pulse duration depending on the energy sharing between the electrons. Most interestingly we find evidence for an interference between direct ('nonsequential') and indirect ('sequential') double photoionization with intermediate shake-up states, the strength of which is controlled by the pulse duration. This observation may provide a route towards measuring the pulse duration of x-ray free-electron laser (XFEL) pulses.

  6. Single and double electron capture in p-He and α-He collisions

    NASA Astrophysics Data System (ADS)

    Samaddar, S.; Halder, S.; Mondal, A.; Mandal, C. R.; Purkait, M.; Das, T. K.

    2017-03-01

    The differential and total cross sections for both single and double electron capture in collisions of {{{H}}}+ and He2+ with ground state helium atom have been studied by means of the four-body model of target continuum distorted wave (TCDW-4B) approximation in the energy range from 30 to 1000 keV amu–1. In this model, distortion in the final channel related to the Coulomb continuum states of the active electron(s) in the field of residual target ion are included. The calculations are based on the independent electron model. The present computed results are compared with the available experimental and other theoretical results. Total cross sections are found to be in good agreement with the measurements. We have also analysed differential cross sections (DCS) for both single and double electron capture in the collision of proton and α-particles with helium atoms at different projectile energies. The present DCS data exhibits the typical steeply decreasing dependence on the projectile scattering angles, but neither oscillating structures characteristic of interference effects nor peaks reminiscent of the Thomas peak are observed at different projectile energies. The obtained results for the DCS into the ground state are compared with the experimental data and overall a satisfactory agreement has been found. Finally we have also studied the variation of double to single capture differential cross-section ratios with projectile scattering angles at different impact energies.

  7. First operation of a dielectric-loaded double-stripline free-electron maser experiment

    SciTech Connect

    Einat, M.; Jerby, E.; Shahadi, A.

    1995-12-31

    A tabletop free-electron maser (FEM) experiment based on a dielectric-loaded double-stripline waveguide is presented. It employs a low-energy (8 keV, 0.5 A) electron beam and a folded-foil wiggler ({lambda}w = 2 cm). Metal striplines protects the dielectric slabs from the electron beam and support quasi-TEM modes in the waveguide. Radiation output is observed at f = 3.5 GHz, in agreement with the dielectric-loaded FEM tuning relation.

  8. Hedgehog excitations in double-exchange magnetism: Energetics and electronic structure

    NASA Astrophysics Data System (ADS)

    Pekker, David; Goldbart, Paul; Salamon, Myron; Abanov, Alexander

    2004-03-01

    Topological hedgehog excitations of the magnetic state are believed to play an important role in the three-dimensional ferromagnet-to-paramagnet phase transition. This is true not only in Heisenberg magnets but also in double-exchange magnets, for which the transition is accompanied by a metal-insulator transition. The energetics and electronic structure of hedgehog excitations in double-exchange systems are investigated using a model in which the electrons move through a lattice of classical spins, to which they are coupled via Hund's Rule interactions. The core energy of hedgehog excitations is determined, as is the extent to which charge is expelled from the hedgehog cores. In settings involving pairs of hedgehogs, the manner in which the electronic energetics determines the magnetic structure is explored variationally, especially in the region between the hedgehogs.

  9. Tandem-structured, hot electron based photovoltaic cell with double Schottky barriers.

    PubMed

    Lee, Young Keun; Lee, Hyosun; Park, Jeong Young

    2014-04-03

    We demonstrate a tandem-structured, hot electron based photovoltaic cell with double Schottky barriers. The tandem-structured, hot electron based photovoltaic cell is composed of two metal/semiconductor interfaces. Two types of tandem cells were fabricated using TiO2/Au/Si and TiO2/Au/TiO2, and photocurrent enhancement was detected. The double Schottky barriers lead to an additional pathway for harvesting hot electrons, which is enhanced through multiple reflections between the two barriers with different energy ranges. In addition, light absorption is improved by the band-to-band excitation of both semiconductors with different band gaps. Short-circuit current and energy conversion efficiency of the tandem-structured TiO2/Au/Si increased by 86% and 70%, respectively, compared with Au/Si metal/semiconductor nanodiodes, showing an overall solar energy conversion efficiency of 5.3%.

  10. Double K-shell vacancy production in the electron capture decay of 139Ce

    NASA Astrophysics Data System (ADS)

    Hindi, M. M.; Kozub, R. L.

    1991-02-01

    The probability of double K-shell vacancy production in the electron capture decay of 139Ce to the 166-keV level of 139La has been investigated. Triple coincidences between the 166-keV gamma ray, the La satellite Kα x ray, and the La hypersatellite Kα x ray were measured using two intrinsic Ge detectors. We looked for the sum of two of the three radiations in one detector in coincidence with the third radiation in the other detector. The probability of double K-shell vacancy production per K-shell electron capture (PKK) was found to be (2.0+/-1.6)×10-6. From this and the known PKK for 131Cs we estimate a probability for zero K-shell vacancy production (shakedown) per K-shell electron capture of <~2.4×10-5 for 139Ce.

  11. Tandem-structured, hot electron based photovoltaic cell with double Schottky barriers

    PubMed Central

    Lee, Young Keun; Lee, Hyosun; Park, Jeong Young

    2014-01-01

    We demonstrate a tandem-structured, hot electron based photovoltaic cell with double Schottky barriers. The tandem-structured, hot electron based photovoltaic cell is composed of two metal/semiconductor interfaces. Two types of tandem cells were fabricated using TiO2/Au/Si and TiO2/Au/TiO2, and photocurrent enhancement was detected. The double Schottky barriers lead to an additional pathway for harvesting hot electrons, which is enhanced through multiple reflections between the two barriers with different energy ranges. In addition, light absorption is improved by the band-to-band excitation of both semiconductors with different band gaps. Short-circuit current and energy conversion efficiency of the tandem-structured TiO2/Au/Si increased by 86% and 70%, respectively, compared with Au/Si metal/semiconductor nanodiodes, showing an overall solar energy conversion efficiency of 5.3%. PMID:24694838

  12. Arbitrary nuclear-spin gates in diamond mediated by a nitrogen-vacancy-center electron spin

    NASA Astrophysics Data System (ADS)

    Casanova, J.; Wang, Z.-Y.; Plenio, M. B.

    2017-09-01

    We show that arbitrary N -qubit interactions among nuclear spins can be achieved efficiently in solid state quantum platforms, such as nitrogen vacancy centers in diamond, by exerting control only on the electron spin coupled to the nuclei. This allows to exploit nuclear spins as robust quantum registers and the direct measurement of nuclear many-body correlators. The method takes advantage of recently introduced dynamical decoupling techniques and avoids the necessity of external, slow, control on the nuclei. Our protocol is general, being applicable to other nuclear spin-based platforms with electronic spin defects acting as mediators as silicon carbide.

  13. Dynamics of quantum dot nuclear spin polarization controlled by a single electron.

    PubMed

    Maletinsky, P; Badolato, A; Imamoglu, A

    2007-08-03

    We present measurements of the buildup and decay of nuclear spin polarization in a single semiconductor quantum dot. Our experiment shows that we polarize the nuclei in a few milliseconds, while their decay dynamics depends drastically on external parameters. We show that a single electron can very efficiently depolarize nuclear spins in milliseconds whereas in the absence of the electron the nuclear spin lifetime is on the scale of seconds. This lifetime is further enhanced by 1-2 orders of magnitude by quenching the nonsecular nuclear dipole-dipole interactions with a magnetic field of 1 mT.

  14. Observation of warm, higher energy electrons transiting a double layer in a helicon plasma

    NASA Astrophysics Data System (ADS)

    Sung, Yung-Ta; Li, Yan; Scharer, John

    2015-11-01

    Experimental observations in MadiHeX indicate that fast electrons with substantial density fractions can be created at low helicon operating pressure. Two-temperature electron distributions including a fast (>80 eV) tail are observed in an inductive RF helicon argon plasma double layer at 0.17 mTorr Ar pressure. The fast, untrapped electrons measured downstream of the double layer have a higher temperature of 13 eV than the trapped, upstream electrons with a temperature of 4 eV. The reduction of plasma potential and density observed in the double layer region would require an upstream temperature ten times the measured 4 eV if occurring via Boltzmann ambipolar expansion. Upstream fluctuations of +/- 30% are also observed in the emissive probe measured plasma potential. Sideband frequencies have been observed at +/- 2 kHz of the driven RF frequency of 13.56 MHz, implying a beam instability effect dominantly upstream of the double layer. This can affect ion acceleration and electron temperature distribution in the region. The mechanism behind this has been explored via several plasma diagnostics tools. An RF-compensated Langmuir probe has been used to measure the electron temperatures and densities, which are cross-checked with ADAS, OES and millimeter wave IF. The EEDF in the plasma has also been profiled to understand the acceleration mechanism. A four-grid RPA and an emissive probe have been used to measure the IEDF and plasma potential. The measured IEDF has also been checked with LIF techniques.

  15. Electron impact double ionization of krypton ions (q = 14-17)

    NASA Astrophysics Data System (ADS)

    Khouilid, M.; Cherkani-Hassani, S.; Adimi, N.; Rachafi, S.; Defrance, P.

    2001-08-01

    Absolute cross sections for electron impact double ionization of krypton ions Krq + (q = 14-17) have been measured from threshold to 5 keV. The animated crossed beam method has been employed. Direct double ionization is seen to reduce strongly along the isonuclear sequence. Ionization-autoionization from the inner L-shell is seen to be the dominant process. It is roughly approximated by the semi-empirical Lotz formula assuming total autoionization of the ionic intermediate states. Resonant capture and excitation processes implying the L-shell are also obtained for charge states 14-16.

  16. Single and double ionization of magnesium by electron impact: A classical study

    NASA Astrophysics Data System (ADS)

    Dubois, J.; Berman, S. A.; Chandre, C.; Uzer, T.

    2017-02-01

    We consider electron impact-driven single and double ionization of magnesium in the energy range of 10 to 100 eV. Our classical Hamiltonian model of these (e ,2 e ) and (e ,3 e ) processes sheds light on their total cross sections and reveals the underlying ionization mechanisms. Two pathways are at play in single ionization: delayed and direct. In contrast, only the direct process is observed in double ionization, ruling out the excitation-autoionization channel. We also provide evidence that the so-called Two-Step 2 mechanism predominates over the Two-Step 1 mechanism, in agreement with experiments.

  17. Effects of intersubband interaction on multisubband electron transport in single and double quantum wells

    NASA Astrophysics Data System (ADS)

    Hai, G.-Q.; Studart, N.; Marques, G. E.; Peeters, F. M.; Koenraad, P. M.

    1998-07-01

    The multisubband electron transport properties are studied for doped single quantum well and gated double asymmetric quantum well structures. The effects due to intersubband interaction and screening of the ionized impurity scattering are also investigated. We show that intersubband coupling plays an essential role in describing the screening properties as well as the effect of ionized impurity scattering on the mobility in a doped single quantum well. For coupled double quantum well structures, negative transconductance is found theoretically which is due to resonant tunneling between the two quantum wells.

  18. Radiative double electron capture in collisions of fully-stripped fluorine ions with thin carbon foils

    NASA Astrophysics Data System (ADS)

    Elkafrawy, Tamer Mohammad Samy

    Radiative double electron capture (RDEC) is a one-step process in ion-atom collisions occurring when two target electrons are captured to a bound state of the projectile simultaneously with the emission of a single photon. The emitted photon has approximately double the energy of the photon emitted due to radiative electron capture (REC), which occurs when a target electron is captured to a projectile bound state with simultaneous emission of a photon. REC and RDEC can be treated as time-reversed photoionization (PI) and double photoionization (DPI), respectively, if loosely-bound target electrons are captured. This concept can be formulated with the principle of detailed balance, in which the processes of our interest can be described in terms of their time-reversed ones. Fully-stripped ions were used as projectiles in the performed RDEC experiments, providing a recipient system free of electron-related Coulomb fields. This allows the target electrons to be transferred without interaction with any of the projectile electrons, enabling accurate investigation of the electron-electron interaction in the vicinity of electromagnetic field. In this dissertation, RDEC was investigated during the collision of fully-stripped fluorine ions with a thin carbon foil and the results are compared with the recent experimental and theoretical studies. In the current work, x rays associated with projectile charge-changing by single and double electron capture and no charge change by F9+ ions were observed and compared with recent work for O8+ ions and with theory. Both the F 9+ and O8+ ions had energies in the ˜MeV/u range. REC, in turn, was investigated as a means to compare with the theoretical predictions of the RDEC/REC cross section ratio. The most significant background processes including various mechanisms of x-ray emission that may interfere with the energy region of interest are addressed in detail. This enables isolation of the contributions of REC and RDEC from the

  19. Influence of nuclear exchange on nonadiabatic electron processes in H(+)+H2 collisions.

    PubMed

    Errea, L F; Illescas, Clara; Macías, A; Méndez, L; Pons, B; Rabadán, I; Riera, A

    2010-12-28

    H(+)+H(2) collisions are studied by means of a semiclassical approach that explicitly accounts for nuclear rearrangement channels in nonadiabatic electron processes. A set of classical trajectories is used to describe the nuclear motion, while the electronic degrees of freedom are treated quantum mechanically in terms of a three-state expansion of the collision wavefunction. We describe electron capture and vibrational excitation, which can also involve nuclear exchange and dissociation, in the E = 2-1000 eV impact energy range. We compare dynamical results obtained with two parametrizations of the potential energy surface of H(3)(+) ground electronic state. Total cross sections for E > 10 eV agree with previous results using a vibronic close-coupling expansion, and with experimental data for E < 10 eV. Additionally, some prototypical features of both nuclear and electron dynamics at low E are discussed.

  20. Suppression of sodium nuclear magnetic resonance double-quantum coherence by chemical shift and relaxation reagents

    NASA Astrophysics Data System (ADS)

    Hutchison, Robert B.; Huntley, James J. A.; Jin, Haoran; Shapiro, Joseph I.

    1992-12-01

    An investigation into the signal suppression behavior of the paramagnetic shift and relaxation reagents, Dy(P3O10)27- and Gd(P3O10)27-, with regard to their use in the nuclear magnetic resonance spectroscopic study of sodium has been performed. Measurements of T1 and T2 relaxation time constants of sodium in normal saline, Krebs-Henseleit buffer, and human blood serum, as a function of concentration of these reagents showed that, although closely coupled in the saline and K-H buffer environments, in plasma T1 and T2 become decoupled, transverse relaxation dominating in comparison to longitudinal relaxation. Linewidth measurements further suggest that relaxation in the plasma milieu is controlled primarily by inherent T2 relaxation, rather than by field inhomogeneity or diffusion effects. Quantitative single-quantum (1Q) and double-quantum (2Q) intensity measurements, biexponential T2 relaxation measurements, and parametric studies of the preparation time of the 2Q pulse sequence, were obtained in suspensions of bovine serum albumin and human erythrocytes. The observed suppression of sodium 2Q coherence by paramagnetic shift and relaxation reagents was found to exhibit a complex behavior in albumin solutions, involving the biexponential T2 decay to be expected during the preparation time of the 2Q filter pulse sequence, as well as the optimum preparation time for production of the double-quantum coherence itself. The controlling factor for both of these effects is the biexponential amplitude function in the expression for the transverse magnetization observed following application of the 2Q pulse sequence. This in turn is determined entirely by the values for the slow and fast components of biexponential relaxation in sodium, which themselves depend upon the concentration of the macromolecular binding sites for quadrupolar interaction. A similar behavior has been observed in suspensions of human erythrocytes.

  1. Probing strongly hybridized nuclear-electronic states in a model quantum ferromagnet

    NASA Astrophysics Data System (ADS)

    Kovacevic, I.; Babkevich, P.; Jeong, M.; Piatek, J. O.; Boero, G.; Rønnow, H. M.

    2016-12-01

    We present direct local-probe evidence for strongly hybridized nuclear-electronic spin states of an Ising ferromagnet LiHoF4 in a transverse magnetic field. The nuclear-electronic states are addressed via a magnetic resonance in the GHz frequency range using coplanar resonators and a vector network analyzer. The magnetic resonance spectrum is successfully traced over the entire field-temperature phase diagram, which is remarkably well reproduced by mean-field calculations. Our method can be directly applied to a broad class of materials containing rare-earth ions for probing the substantially mixed nature of the nuclear and electronic moments.

  2. Electrochemical Electron Transfer and Proton-Coupled Electron Transfer: Effects of Double Layer and Ionic Environment on Solvent Reorganization Energies

    SciTech Connect

    Ghosh, Soumya; Soudackov, Alexander V.; Hammes-Schiffer, Sharon

    2016-06-14

    Electron transfer and proton coupled electron transfer (PCET) reactions at electrochemical interfaces play an essential role in a broad range of energy conversion processes. The reorganization energy, which is a measure of the free energy change associated with solute and solvent rearrangements, is a key quantity for calculating rate constants for these reactions. We present a computational method for including the effects of the double layer and ionic environment of the diffuse layer in calculations of electrochemical solvent reorganization energies. This approach incorporates an accurate electronic charge distribution of the solute within a molecular-shaped cavity in conjunction with a dielectric continuum treatment of the solvent, ions, and electrode using the integral equations formalism polarizable continuum model. The molecule-solvent boundary is treated explicitly, but the effects of the electrode-double layer and double layer-diffuse layer boundaries, as well as the effects of the ionic strength of the solvent, are included through an external Green’s function. The calculated total reorganization energies agree well with experimentally measured values for a series of electrochemical systems, and the effects of including both the double layer and ionic environment are found to be very small. This general approach was also extended to electrochemical PCET and produced total reorganization energies in close agreement with experimental values for two experimentally studied PCET systems. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center, funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

  3. Electronic transport in double-strand poly(dG)-poly(dC) DNA segments

    NASA Astrophysics Data System (ADS)

    Sarmento, R. G.; Albuquerque, E. L.; Sesion, P. D.; Fulco, U. L.; de Oliveira, B. P. W.

    2009-04-01

    We study the electronic properties of a double-strand quasiperiodic DNA molecule modeled by a one-dimensional effective Hamiltonian, which includes contributions from the nucleobasis system as well as the sugar-phosphate backbone. Our theoretical approach makes use of Dyson's equation together with a transfer-matrix treatment, considering an electronic tight-binding Hamiltonian model to investigate the electronic density of states (DOS) and the electronic transmissivity of sequences of DNA finite segments. To mimic the DNA segments, we consider the finite quasiperiodic sequences of Fibonacci's type, in a poly(dG)-poly(dC) configuration, whose building blocks are the bases guanine G and cytosine C. We compared the electronic transport found for the quasiperiodic structure to those using a sequence of natural DNA, as part of the human chromosome Ch22.

  4. Ion acceleration enhanced by additional neutralizing electrons in a magnetically expanding double layer plasma

    SciTech Connect

    Takahashi, Kazunori; Fujiwara, Tamiya

    2010-10-15

    Electrons neutralizing an ion beam are additionally supplied to a magnetically expanding double layer (DL) plasma from the downstream side of the DL. The rf power and the argon gas pressure are maintained at 200 W and 55 mPa, respectively, and the source magnetic field is varied in the range of about 70-550 G. It is observed that the ion beam energy corresponding to the DL potential drop increases up to 30 eV with an increase in the magnetic field when supplying the additional electrons, while it saturates at 20 eV for the case of the absence of the additional electrons. The supplied electrons are believed to be an energy source for the DL such that increasing the magnetic field is able to increase the potential drop beyond the limit found in the absence of the supplied electrons.

  5. Van der Waals-coupled electronic states in incommensurate double-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Liu, Kaihui; Jin, Chenhao; Hong, Xiaoping; Kim, Jihoon; Zettl, Alex; Wang, Enge; Wang, Feng

    2014-10-01

    Non-commensurate two-dimensional materials such as a twisted graphene bilayer or graphene on boron nitride, consisting of components that have no finite common unit cell, exhibit emerging moiré physics such as novel Van Hove singularities, Fermi velocity renormalization, mini Dirac points and Hofstadter butterflies. Here we use double-walled carbon nanotubes as a model system for probing moiré physics in incommensurate one-dimensional systems, by combining structural and optical characterizations. We show that electron wavefunctions between incommensurate inner- and outer-wall nanotubes can hybridize strongly, contrary to the conventional wisdom of negligible electron hybridization due to destructive interference. The chirality-dependent inter-tube electronic coupling is described by one-dimensional zone folding of the electronic structure of twisted-and-stretched graphene bilayers. Our results demonstrate that incommensurate van der Waals interactions can be important for engineering the electronic structure and optical properties of one-dimensional materials.

  6. Correlated electron dynamics in nonsequential double ionization by orthogonal two-color laser pulses.

    PubMed

    Zhou, Yueming; Huang, Cheng; Tong, Aihong; Liao, Qing; Lu, Peixiang

    2011-01-31

    We have investigated the correlated electron dynamics in nonsequential double ionization (NSDI) of helium by the orthogonally polarized two-color pulses that consisted of an 800-nm and a 400-nm laser fields using the classical ensemble model. Depending on the relative phase of the two-color field, the electron momentum distributions along the polarization direction of the 800-nm field exhibit a surprisingly strong anticorrelated or correlated behavior. Back analysis reveals that recollisions eventually leading to NSDI are concentrated in a time window as short as several hundreds attoseconds with this scheme. By changing the relative phase of the two-color field, the revisit time of recolliding electron wave packet has been controlled with attosecond precision, which is responsible for the various correlated behaviors of the two electrons. Our results reveal that the orthogonally polarized two-color field can serve as a powerful tool to control the correlated electron dynamics in NSDI.

  7. The Role of Superthermal Electrons in the Formation of Double Layers and their Application in Space Plasmas

    NASA Astrophysics Data System (ADS)

    Singh, N.

    2014-12-01

    It is now widely recognized that superthermal electrons commonly exist with the thermal population in most space plasmas. When plasmas consisting of such electron population expand, double layers (DLs) naturally forma due to charge separation; the more mobile superthermal electrons march ahead of the thermal population, leaving a positive charge behind and generating electric fields. Under certain conditions such fields evolve into thin double layers or shocks. The double layers accelerate ions. Such double-layer formation was first invoked to explain expansion of laser produced plasmas. Since then it has been studied in laboratory experiments, and applied to (i) polar wind acceleration,(ii) the existence of low-altitude double layers in the auroral acceleration, (iii) a possible mechanism for the origination of the solar wind, (iv) the helicon double layer thrusters, and (v) the deceleration of electrons after their acceleration in solar flare events. The role of superthermal-electron driven double layers, also known as the low-altitude auroral double layers in the upward current region, in the upward acceleration of ionospheric ions is well-known. In the auroral application the upward moving superthermal electrons consist of backscattered downgoing primary energetic electrons as well as the secondary electrons. Similarly we suggest that such double layers might play roles in the acceleration of ions in the solar wind across the coronal transition region, where the superthermal electrons are supplied by magnetic reconnection events. We will present a unified theoretical view of the superthermal electron-driven double layers and their applications. We will summarize theoretical, experimental, simulation and observational results highlighting the common threads running through the various existing studies.

  8. On the bonding nature of electron states for the Fe-Mo double perovskite

    NASA Astrophysics Data System (ADS)

    Carvajal, E.; Oviedo-Roa, R.; Cruz-Irisson, M.; Navarro, O.

    2014-05-01

    The electronic transport as well as the effect of an external magnetic field has been investigated on manganese-based materials, spinels and perovskites. Potential applications of double perovskites go from magnetic sensors to electrodes in solid-oxide fuel cells; besides the practical interests, it is known that small changes in composition modify radically the physical properties of double perovskites. We have studied the Sr2FeMoO6 double perovskite compound (SFMO) using first-principles density functional theory. The calculations were done within the generalized gradient approximation (GGA) scheme with the Perdew-Burke-Ernzerhof (PBE) functional. We have made a detailed analysis of each electronic state and the charge density maps around the Fermi level. For the electronic properties of SFMO it was used a primitive cell, for which we found the characteristic half-metallic behavior density of states composed by eg and t2g electrons from Fe and Mo atoms. Those peaks were tagged as bonding or antibonding around the Fermi level at both, valence and conduction bands.

  9. Orientation effect on the secondary-electron distributions for the HCl double ionization

    NASA Astrophysics Data System (ADS)

    Mokrani, S.; Aouchiche, H.; Champion, C.

    2017-07-01

    Multiple differential cross sections of the double ionization of hydrogen chloride molecule impacted by electrons are here provided within the first Born approximation. The incident and scattered electrons are represented by plane wave functions, whereas the target is described by means of a single-center molecular wave function. The two ejected electrons are modeled by Coulomb wave functions and a Gamow factor is introduced to take into account the Coulomb repulsion between the two outgoing particles. In this work, we study the relative contributions of the four outermost orbitals of the HCl molecule to the double ionization process in the particular case of two electrons ejected from different subshells. The multiple differential cross sections are analyzed for specific target orientations and compared in terms of magnitude and shape. We report a strong dependence of the cross sections versus the target orientation by pointing out the signature of the well-known double ionizing processes, namely, the shake-off and the two-step 1 mechanisms.

  10. On the bonding nature of electron states for the Fe-Mo double perovskite

    SciTech Connect

    Carvajal, E.; Cruz-Irisson, M.; Oviedo-Roa, R.; Navarro, O.

    2014-05-15

    The electronic transport as well as the effect of an external magnetic field has been investigated on manganese-based materials, spinels and perovskites. Potential applications of double perovskites go from magnetic sensors to electrodes in solid-oxide fuel cells; besides the practical interests, it is known that small changes in composition modify radically the physical properties of double perovskites. We have studied the Sr{sub 2}FeMoO{sub 6} double perovskite compound (SFMO) using first-principles density functional theory. The calculations were done within the generalized gradient approximation (GGA) scheme with the Perdew-Burke-Ernzerhof (PBE) functional. We have made a detailed analysis of each electronic state and the charge density maps around the Fermi level. For the electronic properties of SFMO it was used a primitive cell, for which we found the characteristic half-metallic behavior density of states composed by e{sub g} and t{sub 2g} electrons from Fe and Mo atoms. Those peaks were tagged as bonding or antibonding around the Fermi level at both, valence and conduction bands.

  11. Nb2O5 as a new electron transport layer for double junction polymer solar cells.

    PubMed

    Siddiki, Mahbube K; Venkatesan, Swaminathan; Qiao, Qiquan

    2012-04-14

    Nb(2)O(5) as a new electron transport layer (ETL) was used for double junction polymer solar cells. The Nb(2)O(5) ETL was prepared by spin coating a Nb(2)O(5) sol-gel solution onto the active layer of the optical front subcell. The double junction devices using Nb(2)O(5) ETL exhibit an open circuit voltage (V(oc)) of 1.30 V, which is close to the sum of the s of the individual subcells. The current density-voltage (J-V) simulation showed that the double junction device performance using Nb(2)O(5) as ETL could be significantly increased by reducing the series resistance (R(se)) and matching the current densities of the individual subcells.

  12. Correlative super-resolution fluorescence and electron microscopy of the nuclear pore complex with molecular resolution.

    PubMed

    Löschberger, Anna; Franke, Christian; Krohne, Georg; van de Linde, Sebastian; Sauer, Markus

    2014-10-15

    Here, we combine super-resolution fluorescence localization microscopy with scanning electron microscopy to map the position of proteins of nuclear pore complexes in isolated Xenopus laevis oocyte nuclear envelopes with molecular resolution in both imaging modes. We use the periodic molecular structure of the nuclear pore complex to superimpose direct stochastic optical reconstruction microscopy images with a precision of <20 nm on electron micrographs. The correlative images demonstrate quantitative molecular labeling and localization of nuclear pore complex proteins by standard immunocytochemistry with primary and secondary antibodies and reveal that the nuclear pore complex is composed of eight gp210 (also known as NUP210) protein homodimers. In addition, we find subpopulations of nuclear pore complexes with ninefold symmetry, which are found occasionally among the more typical eightfold symmetrical structures. © 2014. Published by The Company of Biologists Ltd.

  13. Electronic promotion effect of double proton transfer on conduction of DNA through improvement of transverse electronic communication of base pairs

    NASA Astrophysics Data System (ADS)

    Liu, Haiying; Li, Genqin; Zhang, Laibin; Li, Jilai; Wang, Meishan; Bu, Yuxiang

    2011-10-01

    The effect of double proton transfer (DPT) on charge migration of DNA was investigated by the nonequilibrium Green's function method combined with density functional theory. The results revealed that DPT not only lowers ionization potentials, but also improves the delocalization of the localized π-orbitals at each base moiety through adjusting energy levels and spatial distributions of their molecular orbitals. Furthermore, DPT leads to both the strengthening of the second-order interactions of the Watson-Crick H-bond zones, and the promotion of the charge transfer transitions between two pairing bases in the UV absorption spectra. Electronic transport calculations indicated that DPT can improve the charge migration along the DNA duplex for specific sequences through enhancing transverse base-to-base electronic communication. This work will provide a new insight into the understanding of DNA charge conduction which can be electronically promoted or regulated by DPT.

  14. PML nuclear body disruption impairs DNA double-strand break sensing and repair in APL.

    PubMed

    di Masi, A; Cilli, D; Berardinelli, F; Talarico, A; Pallavicini, I; Pennisi, R; Leone, S; Antoccia, A; Noguera, N I; Lo-Coco, F; Ascenzi, P; Minucci, S; Nervi, C

    2016-07-28

    Proteins involved in DNA double-strand break (DSB) repair localize within the promyelocytic leukemia nuclear bodies (PML-NBs), whose disruption is at the root of the acute promyelocytic leukemia (APL) pathogenesis. All-trans-retinoic acid (RA) treatment induces PML-RARα degradation, restores PML-NB functions, and causes terminal cell differentiation of APL blasts. However, the precise role of the APL-associated PML-RARα oncoprotein and PML-NB integrity in the DSB response in APL leukemogenesis and tumor suppression is still lacking. Primary leukemia blasts isolated from APL patients showed high phosphorylation levels of H2AX (γ-H2AX), an initial DSBs sensor. By addressing the consequences of ionizing radiation (IR)-induced DSB response in primary APL blasts and RA-responsive and -resistant myeloid cell lines carrying endogenous or ectopically expressed PML-RARα, before and after treatment with RA, we found that the disruption of PML-NBs is associated with delayed DSB response, as revealed by the impaired kinetic of disappearance of γ-H2AX and 53BP1 foci and activation of ATM and of its substrates H2AX, NBN, and CHK2. The disruption of PML-NB integrity by PML-RARα also affects the IR-induced DSB response in a preleukemic mouse model of APL in vivo. We propose the oncoprotein-dependent PML-NB disruption and DDR impairment as relevant early events in APL tumorigenesis.

  15. Nuclear DNA C-values in 30 species double the familial representation in pteridophytes.

    PubMed

    Obermayer, Renate; Leitch, Ilia J; Hanson, Lynda; Bennett, Michael D

    2002-08-01

    Nuclear DNA C-values and genome size are important biodiversity characters with fundamental biological significance. Yet C-value data for pteridophytes, a diverse group of vascular plants with approx. 9000 extant species, remain scarce. A recent survey by Bennett and Leitch (2001, Annals of Botany 87: 335-345) found that C-values were reported for only 48 pteridophyte species. To improve phylogenetic representation in this group and to check previously reported estimates, C-values for 30 taxa in 17 families were measured using flow cytometry for all but one species. This technique proved generally applicable, but the ease with which C-value data were generated varied greatly between materials. Comparing the new data with those previously published revealed several large discrepancies. After discounting doubtful data, C-values for 62 pteridophyte species remained acceptable for analysis. The present work has increased the number of such species' C-values by 93 %, and more than doubled the number of families represented (from 10 to 21). Analysis shows that pteridophyte C-values vary approx. 450-fold, from 0-16 pg in Selaginella kraussiana to 72.7 pg in Psilotum nudum var. gasa. Superimposing C-value data onto a robust phylogeny of pteridophytes suggests some possible trends in C-value evolution and highlights areas for future work.

  16. Nuclear magnetic resonance diffusion pore imaging: Experimental phase detection by double diffusion encoding

    NASA Astrophysics Data System (ADS)

    Demberg, Kerstin; Laun, Frederik Bernd; Windschuh, Johannes; Umathum, Reiner; Bachert, Peter; Kuder, Tristan Anselm

    2017-02-01

    Diffusion pore imaging is an extension of diffusion-weighted nuclear magnetic resonance imaging enabling the direct measurement of the shape of arbitrarily formed, closed pores by probing diffusion restrictions using the motion of spin-bearing particles. Examples of such pores comprise cells in biological tissue or oil containing cavities in porous rocks. All pores contained in the measurement volume contribute to one reconstructed image, which reduces the problem of vanishing signal at increasing resolution present in conventional magnetic resonance imaging. It has been previously experimentally demonstrated that pore imaging using a combination of a long and a narrow magnetic field gradient pulse is feasible. In this work, an experimental verification is presented showing that pores can be imaged using short gradient pulses only. Experiments were carried out using hyperpolarized xenon gas in well-defined pores. The phase required for pore image reconstruction was retrieved from double diffusion encoded (DDE) measurements, while the magnitude could either be obtained from DDE signals or classical diffusion measurements with single encoding. The occurring image artifacts caused by restrictions of the gradient system, insufficient diffusion time, and by the phase reconstruction approach were investigated. Employing short gradient pulses only is advantageous compared to the initial long-narrow approach due to a more flexible sequence design when omitting the long gradient and due to faster convergence to the diffusion long-time limit, which may enable application to larger pores.

  17. And yet, it moves: nuclear and chromatin dynamics of a heterochromatic double-strand break.

    PubMed

    Caridi, P Christopher; Delabaere, Laetitia; Zapotoczny, Grzegorz; Chiolo, Irene

    2017-10-05

    Heterochromatin is mostly composed of repeated DNA sequences prone to aberrant recombination. How cells maintain the stability of these sequences during double-strand break (DSB) repair has been a long-standing mystery. Studies in Drosophila cells revealed that faithful homologous recombination repair of heterochromatic DSBs relies on the striking relocalization of repair sites to the nuclear periphery before Rad51 recruitment and repair progression. Here, we summarize our current understanding of this response, including the molecular mechanisms involved, and conserved pathways in mammalian cells. We will highlight important similarities with pathways identified in budding yeast for repair of other types of repeated sequences, including rDNA and short telomeres. We will also discuss the emerging role of chromatin composition and regulation in heterochromatin repair progression. Together, these discoveries challenged previous assumptions that repair sites are substantially static in multicellular eukaryotes, that heterochromatin is largely inert in the presence of DSBs, and that silencing and compaction in this domain are obstacles to repair.This article is part of the themed issue 'Chromatin modifiers and remodellers in DNA repair and signalling'. © 2017 The Authors.

  18. PML nuclear body disruption impairs DNA double-strand break sensing and repair in APL

    PubMed Central

    di Masi, A; Cilli, D; Berardinelli, F; Talarico, A; Pallavicini, I; Pennisi, R; Leone, S; Antoccia, A; Noguera, N I; Lo-Coco, F; Ascenzi, P; Minucci, S; Nervi, C

    2016-01-01

    Proteins involved in DNA double-strand break (DSB) repair localize within the promyelocytic leukemia nuclear bodies (PML-NBs), whose disruption is at the root of the acute promyelocytic leukemia (APL) pathogenesis. All-trans-retinoic acid (RA) treatment induces PML-RARα degradation, restores PML-NB functions, and causes terminal cell differentiation of APL blasts. However, the precise role of the APL-associated PML-RARα oncoprotein and PML-NB integrity in the DSB response in APL leukemogenesis and tumor suppression is still lacking. Primary leukemia blasts isolated from APL patients showed high phosphorylation levels of H2AX (γ-H2AX), an initial DSBs sensor. By addressing the consequences of ionizing radiation (IR)-induced DSB response in primary APL blasts and RA-responsive and -resistant myeloid cell lines carrying endogenous or ectopically expressed PML-RARα, before and after treatment with RA, we found that the disruption of PML-NBs is associated with delayed DSB response, as revealed by the impaired kinetic of disappearance of γ-H2AX and 53BP1 foci and activation of ATM and of its substrates H2AX, NBN, and CHK2. The disruption of PML-NB integrity by PML-RARα also affects the IR-induced DSB response in a preleukemic mouse model of APL in vivo. We propose the oncoprotein-dependent PML-NB disruption and DDR impairment as relevant early events in APL tumorigenesis. PMID:27468685

  19. Nuclear magnetic resonance diffusion pore imaging: Experimental phase detection by double diffusion encoding.

    PubMed

    Demberg, Kerstin; Laun, Frederik Bernd; Windschuh, Johannes; Umathum, Reiner; Bachert, Peter; Kuder, Tristan Anselm

    2017-02-01

    Diffusion pore imaging is an extension of diffusion-weighted nuclear magnetic resonance imaging enabling the direct measurement of the shape of arbitrarily formed, closed pores by probing diffusion restrictions using the motion of spin-bearing particles. Examples of such pores comprise cells in biological tissue or oil containing cavities in porous rocks. All pores contained in the measurement volume contribute to one reconstructed image, which reduces the problem of vanishing signal at increasing resolution present in conventional magnetic resonance imaging. It has been previously experimentally demonstrated that pore imaging using a combination of a long and a narrow magnetic field gradient pulse is feasible. In this work, an experimental verification is presented showing that pores can be imaged using short gradient pulses only. Experiments were carried out using hyperpolarized xenon gas in well-defined pores. The phase required for pore image reconstruction was retrieved from double diffusion encoded (DDE) measurements, while the magnitude could either be obtained from DDE signals or classical diffusion measurements with single encoding. The occurring image artifacts caused by restrictions of the gradient system, insufficient diffusion time, and by the phase reconstruction approach were investigated. Employing short gradient pulses only is advantageous compared to the initial long-narrow approach due to a more flexible sequence design when omitting the long gradient and due to faster convergence to the diffusion long-time limit, which may enable application to larger pores.

  20. Nuclear fission fragment excitation of electronic transition laser media

    NASA Technical Reports Server (NTRS)

    Lorents, D. C.; Mccusker, M. V.; Rhodes, C. K.

    1976-01-01

    Specific characteristics of the media including density, excitation rates, wavelength, kinetics, fissile material, scale size, and medium uniformity are assessed. The use of epithermal neutrons, homogeneously mixed fissile material, and special high cross section nuclear isotopes to optimize coupling of the energy to the medium are shown to be important considerations maximizing the scale size, energy deposition, and medium uniformity. It is demonstrated that e-beam excitation can be used to simulate nuclear pumping conditions to facilitate the search for candidate media.

  1. Electron momentum spectroscopy of dimethyl ether taking account of nuclear dynamics in the electronic ground state

    SciTech Connect

    Morini, Filippo; Deleuze, Michael Simon; Watanabe, Noboru; Kojima, Masataka; Takahashi, Masahiko

    2015-10-07

    The influence of nuclear dynamics in the electronic ground state on the (e,2e) momentum profiles of dimethyl ether has been analyzed using the harmonic analytical quantum mechanical and Born-Oppenheimer molecular dynamics approaches. In spite of fundamental methodological differences, results obtained with both approaches consistently demonstrate that molecular vibrations in the electronic ground state have a most appreciable influence on the momentum profiles associated to the 2b{sub 1}, 6a{sub 1}, 4b{sub 2}, and 1a{sub 2} orbitals. Taking this influence into account considerably improves the agreement between theoretical and newly obtained experimental momentum profiles, with improved statistical accuracy. Both approaches point out in particular the most appreciable role which is played by a few specific molecular vibrations of A{sub 1}, B{sub 1}, and B{sub 2} symmetries, which correspond to C–H stretching and H–C–H bending modes. In line with the Herzberg-Teller principle, the influence of these molecular vibrations on the computed momentum profiles can be unraveled from considerations on the symmetry characteristics of orbitals and their energy spacing.

  2. Electron momentum spectroscopy of dimethyl ether taking account of nuclear dynamics in the electronic ground state.

    PubMed

    Morini, Filippo; Watanabe, Noboru; Kojima, Masataka; Deleuze, Michael Simon; Takahashi, Masahiko

    2015-10-07

    The influence of nuclear dynamics in the electronic ground state on the (e,2e) momentum profiles of dimethyl ether has been analyzed using the harmonic analytical quantum mechanical and Born-Oppenheimer molecular dynamics approaches. In spite of fundamental methodological differences, results obtained with both approaches consistently demonstrate that molecular vibrations in the electronic ground state have a most appreciable influence on the momentum profiles associated to the 2b1, 6a1, 4b2, and 1a2 orbitals. Taking this influence into account considerably improves the agreement between theoretical and newly obtained experimental momentum profiles, with improved statistical accuracy. Both approaches point out in particular the most appreciable role which is played by a few specific molecular vibrations of A1, B1, and B2 symmetries, which correspond to C-H stretching and H-C-H bending modes. In line with the Herzberg-Teller principle, the influence of these molecular vibrations on the computed momentum profiles can be unraveled from considerations on the symmetry characteristics of orbitals and their energy spacing.

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

    SciTech Connect

    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.

  4. Coupling capacitance between double quantum dots tunable by the number of electrons in Si quantum dots

    SciTech Connect

    Uchida, Takafumi Arita, Masashi; Takahashi, Yasuo; Fujiwara, Akira

    2015-02-28

    Tunability of capacitive coupling in the Si double-quantum-dot system is discussed by changing the number of electrons in quantum dots (QDs), in which the QDs are fabricated using pattern-dependent oxidation (PADOX) of a Si nanowire and multi-fine-gate structure. A single QD formed by PADOX is divided into multiple QDs by additional oxidation through the gap between the fine gates. When the number of electrons occupying the QDs is large, the coupling capacitance increases gradually and almost monotonically with the number of electrons. This phenomenon is attributed to the gradual growth in the effective QD size due to the increase in the number of electrons in the QDs. On the other hand, when the number of electrons changes in the few-electron regime, the coupling capacitance irregularly changes. This irregularity can be observed even up to 40 electrons. This behavior is attributable the rough structure of Si nano-dots made by PADOX. This roughness is thought to induce complicated change in the electron wave function when an electron is added to or subtracted from a QD.

  5. Electron-acoustic solitons and double layers in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Vasko, I. Y.; Agapitov, O. V.; Mozer, F. S.; Bonnell, J. W.; Artemyev, A. V.; Krasnoselskikh, V. V.; Reeves, G.; Hospodarsky, G.

    2017-05-01

    The Van Allen Probes observe generally two types of electrostatic solitary waves (ESW) contributing to the broadband electrostatic wave activity in the nightside inner magnetosphere. ESW with symmetric bipolar parallel electric field are electron phase space holes. The nature of ESW with asymmetric bipolar (and almost unipolar) parallel electric field has remained puzzling. To address their nature, we consider a particular event observed by Van Allen Probes to argue that during the broadband wave activity electrons with energy above 200 eV provide the dominant contribution to the total electron density, while the density of cold electrons (below a few eV) is less than a few tenths of the total electron density. We show that velocities of the asymmetric ESW are close to velocity of electron-acoustic waves (existing due to the presence of cold and hot electrons) and follow the Korteweg-de Vries (KdV) dispersion relation derived for the observed plasma conditions (electron energy spectrum is a power law between about 100 eV and 10 keV and Maxwellian above 10 keV). The ESW spatial scales are in general agreement with the KdV theory. We interpret the asymmetric ESW in terms of electron-acoustic solitons and double layers (shocks waves).

  6. Subcycle electron emission in sequential double ionization by elliptical laser pulses

    NASA Astrophysics Data System (ADS)

    Tong, Ai-Hong; Li, Ying-Bin

    2016-12-01

    Using a classical ensemble method, we have investigated sequential double ionization (SDI) of Ar atoms driven by elliptical laser pulses. The results show that the ion momentum distribution of the Ar atoms depends strongly on the pulse duration. As the pulse duration increases, the ion momentum distribution changes from two bands to four bands and then to six bands and finally to an eight-band structure. Back analysis of double ionization trajectories shows that the variation of the band structure originates from pulse duration dependent multiple ionization bursts of the second electron. Our calculations indicate that the subcycle electron emission in the SDI could be more easily accessed by using elliptical laser pulses with a longer wavelength. Moreover, we show that there is good correspondence between the scaled radial momentum and the ionization time.

  7. Electronic energy band structure of the double perovskite Ba2MnWO6.

    PubMed

    Fujioka, Yukari; Frantti, Johannes; Nieminen, Risto M

    2008-06-05

    The electronic and magnetic structures of the double perovskite oxide Ba 2MnWO6 (BMW) were determined by employing the density functional theory within the generalized gradient approximation (GGA) + U approach. BMW is considered a prototype double perovskite due to its high degree of B-site ordering and is a good case study for making a comparison between computations and experiments. By adjusting the U-parameter, the electronic energy band structure and magnetic properties, which were consistent with the experimental results, were obtained. These computations revealed that the valence bands are mainly formed from Mn 3d and O 2p states, while the conduction bands are derived from W 5d and O 2p states. The localized bands composed from Mn 3d states are located in the bandgap. The results imply that the formation of polarons in the conduction band initiate the resonance Raman modes observed as a series of equidistant peaks.

  8. Nonlinear ion-acoustic double-layers in electronegative plasmas with electrons featuring Tsallis distribution

    NASA Astrophysics Data System (ADS)

    Ghebache, Siham; Tribeche, Mouloud

    2016-04-01

    Weakly nonlinear ion-acoustic (IA) double-layers (DLs), which accompany electronegative plasmas composed of positive ions, negative ions, and nonextensive electrons are investigated. A generalized Korteweg-de Vries equation with a cubic nonlinearity is derived using a reductive perturbation method. Different types of electronegative plasmas inspired from the experimental studies of Ichiki et al. (2001) are discussed. It is shown that the IA wave phase velocity, in different mixtures of negative and positive ions, decreases as the nonextensive parameter q increases, before levelling-off at a constant value for larger q. Moreover, a relative increase of Q involves an enhancement of the IA phase velocity. Existence domains of either solitary waves or double-layers are then presented and their parametric dependence is determined. Owing to the electron nonextensivity, our present plasma model can admit compressive as well as rarefactive IA-DLs.

  9. NUMEN Project @ LNS : Heavy ions double charge exchange reactions towards the 0νββ nuclear matrix element determination

    SciTech Connect

    Agodi, C. Calabretta, L.; Calanna, A.; Carbone, D.; Cavallaro, M.; Colonna, M.; Cuttone, G.; Finocchiaro, P.; Pandola, L.; Rifuggiato, D.; Tudisco, S.; Cappuzzello, F.; Greco, V.; Bonanno, D. L.; Bongiovanni, D. G.; Longhitano, F.; Branchina, V.; Foti, A.; Lo Presti, D.; Lanzalone, G.; and others

    2015-10-28

    In the NUMEN Project it is proposed an innovative technique to access the nuclear matrix elements entering in the expression of the life-time of the neutrinoless double beta decay, using relevant cross sections of double charge exchange reactions. A key aspect is the use of MAGNEX large acceptance magnetic spectrometer, for the detection of the ejectiles, and of the INFN Laboratori Nazionali del Sud (LNS) K800 Superconducting Cyclotron (CS), for the acceleration of the required high resolution and low emittance heavy-ion beams.

  10. Double ionization of single oriented water molecules by electron impact: Second-order Born description

    SciTech Connect

    Dal Cappello, C.; Champion, C.; Kada, I.; Mansouri, A.

    2011-06-15

    The double ionization of isolated water molecules fixed in space is investigated within a theoretical approach based on the second-order Born approximation. Electron angular distributions have been studied for specific kinematical conditions. The three usual mechanisms, the shake-off and the two two-step mechanisms, have been identified. A significant contribution of the two-step mechanism is clearly visible for some particular kinematics.

  11. Search for double electron capture on 124Xe with the XMASS-I detector

    NASA Astrophysics Data System (ADS)

    Hiraide, Katsuki; XMASS Collaboration

    2016-05-01

    The XMASS project is a multi-purpose experiment using highly-purified liquid xenon scintillator located underground at the Kamioka Observatory in Japan. A search for two-neutrino double electron capture on 124Xe is performed using 165.9 days of data collected with the XMASS-I detector. No significant excess above background was observed and we set a lower limit on the half-life as 4.7 × 1021 years at 90% confidence level.

  12. Double-spin asymmetries in electron-nucleon scattering in Halls B and C at Jlab

    SciTech Connect

    Donald Crabb

    2003-07-15

    Three experiments at JLab have measured the double polarization asymmetries in the nucleon resonance region, using polarized electron beams incident on polarized proton and deuteron targets. The analysis for the first experiment, eg1a in Hall B, is nearly finished and preliminary values of the spin structure function g1(x, Q2) and the first moment (x) have been extracted. The other two experiments, one in Hall B and one in Hall C, are still analyzing data. Some results are presented.

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

    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.

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

    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.

  15. Optically Imaged Striped Domains of Nonequilibrium Electronic and Nuclear Spins in a Fractional Quantum Hall Liquid

    NASA Astrophysics Data System (ADS)

    Moore, John N.; Hayakawa, Junichiro; Mano, Takaaki; Noda, Takeshi; Yusa, Go

    2017-02-01

    Using photoluminescence microscopy enhanced by magnetic resonance, we visualize in real space both electron and nuclear polarization occurring in nonequilibrium fraction quantum Hall (FQH) liquids. We observe stripelike domain regions comprising FQH excited states which discretely form when the FQH liquid is excited by a source-drain current. These regions are deformable and give rise to bidirectionally polarized nuclear spins as spin-resolved electrons flow across their boundaries.

  16. Optically Imaged Striped Domains of Nonequilibrium Electronic and Nuclear Spins in a Fractional Quantum Hall Liquid.

    PubMed

    Moore, John N; Hayakawa, Junichiro; Mano, Takaaki; Noda, Takeshi; Yusa, Go

    2017-02-17

    Using photoluminescence microscopy enhanced by magnetic resonance, we visualize in real space both electron and nuclear polarization occurring in nonequilibrium fraction quantum Hall (FQH) liquids. We observe stripelike domain regions comprising FQH excited states which discretely form when the FQH liquid is excited by a source-drain current. These regions are deformable and give rise to bidirectionally polarized nuclear spins as spin-resolved electrons flow across their boundaries.

  17. Virtual enterprise model for the electronic components business in the Nuclear Weapons Complex

    SciTech Connect

    Ferguson, T.J.; Long, K.S.; Sayre, J.A.; Hull, A.L.; Carey, D.A.; Sim, J.R.; Smith, M.G.

    1994-08-01

    The electronic components business within the Nuclear Weapons Complex spans organizational and Department of Energy contractor boundaries. An assessment of the current processes indicates a need for fundamentally changing the way electronic components are developed, procured, and manufactured. A model is provided based on a virtual enterprise that recognizes distinctive competencies within the Nuclear Weapons Complex and at the vendors. The model incorporates changes that reduce component delivery cycle time and improve cost effectiveness while delivering components of the appropriate quality.

  18. ELDOR-detected NMR: A general and robust method for electron-nuclear hyperfine spectroscopy?

    NASA Astrophysics Data System (ADS)

    Cox, Nicholas; Nalepa, Anna; Lubitz, Wolfgang; Savitsky, Anton

    2017-07-01

    ELDOR-detected NMR (EDNMR) performed at higher magnetic fields is becoming an increasingly popular alternative to conventional ENDOR for the characterization of electron-nuclear hyperfine interactions owing to its enhanced sensitivity. However there are two key problems that limit its widespread adoption, with factors controlling: (i) lineshape distortions and; (ii) overall spectral resolution, still largely understood only at a qualitative level. Indeed highly anisotropic (dipolar) coupled species are particularly problematic in the EDNMR experiment. Nor is it clear as to whether line intensities measured in EDNMR can provide quantitative information. Here we describe how all these problems can be overcome for a nitroxide radical as model system. We introduce a simulation procedure/protocol for the simulation of EDNMR line-shapes collected over a range of high turning angle (HTA) pulse lengths. It is shown that spectral line-shapes can be robustly reproduced and that the intensities of spectral lines and the spin nutation behavior can be quantitatively assessed. This broadens the scope of the EDNMR experiment as a generally applicable, quantitative double resonance method.

  19. Effect of spin-flip scattering on the electron transport through double quantum dots

    NASA Astrophysics Data System (ADS)

    Yang, Fu-Bin; Huang, Rui; Cheng, Yan

    2015-05-01

    We systematically investigate the electron transport through double quantum dots (DQD) with particular emphasis on the spin-flip scattering of an electron in the DQD. By means of the slave-boson mean-field approximation, we calculate the linear conductance and the transmission in the Kondo regime at zero temperature. The obtained results show that both the linear conductance and transmission probability are quite sensitive to the spin-flip strength when the DQD structure is changed among the serial, parallel and T-shaped. It is suggested that such a theoretical model can be used to study the physical phenomenon related to the spin manipulation transport.

  20. Frustrated double and single ionization in a two-electron triatomic molecule H+ 3

    NASA Astrophysics Data System (ADS)

    Chen, A.; Lazarou, C.; Price, H.; Emmanouilidou, A.

    2016-12-01

    Using a semi-classical model, we study the formation of highly excited neutral fragments during the fragmentation of {{{H}}}3+, a two-electron triatomic molecule, driven by an intense near-IR laser field. To do so, we first formulate a microcanonical distribution for arbitrary one-electron triatomic molecules. We then study frustrated double and single ionization in strongly driven {{{H}}}3+ and compute the kinetic energy release of the nuclei for these two processes. Moreover, we investigate the dependence of frustrated ionization on the strength of the laser field as well as on the geometry of the initial molecular state.

  1. Characteristics of a Sheath with Secondary Electron Emission in the Double Walls of a Hall Thruster

    NASA Astrophysics Data System (ADS)

    Duan, Ping; Li, Xi; Shen, Hongjuan; Chen, Long; E, Peng

    2012-09-01

    In order to investigate the effects of secondary electrons, which are emitted from the wall, on the performance of a thruster, a one-dimensional fluid model of the plasma sheath in double walls is applied to study the characteristics of a magnetized sheath. The effects of secondary electron emission (SEE) coefficients and trapping coefficients, as well as magnetic field, on the structure of the plasma sheath are investigated. The results show that sheath potential and wall potential rise with the increment of SEE coefficient and trapping coefficient which results in a reduced sheath thickness. In addition, magnetic field strength will influence the sheath potential distributions.

  2. Localized Hartree product treatment of multiple protons in the nuclear-electronic orbital framework

    NASA Astrophysics Data System (ADS)

    Auer, Benjamin; Hammes-Schiffer, Sharon

    2010-02-01

    An approximation for treating multiple quantum nuclei within the nuclear-electronic orbital (NEO) framework for molecular systems is presented. In the approximation to NEO-Hartree-Fock, the nuclear wave function is represented by a Hartree product rather than a Slater determinant, corresponding to the neglect of the nuclear exchange interactions. In the approximation to NEO-density functional theory, the nuclear exchange-correlation functional is chosen to be the diagonal nuclear exchange interaction terms, thereby eliminating the nuclear self-interaction terms. To further enhance the simplicity and computational efficiency, the nuclear molecular orbitals or Kohn-Sham orbitals are expanded in terms of localized nuclear basis sets. These approximations are valid because of the inherent localization of the nuclear orbitals and the numerical insignificance of the nuclear exchange interactions in molecular systems. Moreover, these approximations lead to substantial computational savings due to the reduction in both the number of integrals that must be calculated and the size of the matrices that must be diagonalized. These nuclear Hartree product approximation (HPA) methods scale linearly with the number of quantum protons and are highly parallelizable. Applications to a water hexamer, glycine dimer, and 32-water cluster, where all hydrogen nuclei are treated quantum mechanically, illustrate the accuracy and computational efficiency of the nuclear HPA methods. These strategies will facilitate the implementation of explicitly correlated NEO methods for molecular systems with multiple quantum protons.

  3. Tunable surface electron spin splitting with electric double-layer transistors based on InN.

    PubMed

    Yin, Chunming; Yuan, Hongtao; Wang, Xinqiang; Liu, Shitao; Zhang, Shan; Tang, Ning; Xu, Fujun; Chen, Zhuoyu; Shimotani, Hidekazu; Iwasa, Yoshihiro; Chen, Yonghai; Ge, Weikun; Shen, Bo

    2013-05-08

    Electrically manipulating electron spins based on Rashba spin-orbit coupling (SOC) is a key pathway for applications of spintronics and spin-based quantum computation. Two-dimensional electron systems (2DESs) offer a particularly important SOC platform, where spin polarization can be tuned with an electric field perpendicular to the 2DES. Here, by measuring the tunable circular photogalvanic effect (CPGE), we present a room-temperature electric-field-modulated spin splitting of surface electrons on InN epitaxial thin films that is a good candidate to realize spin injection. The surface band bending and resulting CPGE current are successfully modulated by ionic liquid gating within an electric double-layer transistor configuration. The clear gate voltage dependence of CPGE current indicates that the spin splitting of the surface electron accumulation layer is effectively tuned, providing a way to modulate the injected spin polarization in potential spintronic devices.

  4. Double layer electric fields aiding the production of superthermal electrons within magnetic reconnection exhausts

    NASA Astrophysics Data System (ADS)

    Egedal, Jan; Daughton, William; Le, Ari

    2015-11-01

    Using a kinetic simulation of magnetic reconnection it was recently shown that parallel electric fields (E∥) can be present over large spatial scales in reconnection exhausts. The largest values of E∥ are observed within double layers, which form through large parallel streaming of electrons into the reconnection region. The electron confinement, provided in part by the structure in E∥, allows sustained energization by perpendicular electric fields (E⊥). The energization is a consequence of the confined electrons' chaotic orbital motion that includes drifts aligned with the reconnection electric field. The mechanism is effective in an extended region of the reconnection exhaust allowing for the generation of superthermal electrons in reconnection scenarios, including those with only a single x-line. The numerical and analytical results agree with detailed spacecraft observations recorded during reconnection events in the Earth's magnetotail. Supported by NSF GEM award 1405166 and NASA grant NNX14AC68G.

  5. Studies of electron correlation effects in multicharged ion atom collisions involving double capture

    SciTech Connect

    Stolterfoht, N.; Sommer, K.; Griffin, D.C.; Havener, C.C.; Huq, M.S.; Phaneuf, R.A.; Swenson, J.K.; Meyer, F.W.

    1988-01-01

    We review measurements of L-Coster Kronig and Auger electron production in slow, multicharged collision systems to study electron correlation effects in the process of double electron capture. The n/sup /minus/3/ law was confirmed for the production of the Coster-Kronig configurations 1s/sup 2/2pn/ell/ (n greater than or equal to 6) in O/sup 6 +/ + He collisions. Enhancement of high angular momentum /ell/ in specific 1s/sup 2/2pn/ell/ configurations was observed by means of high-resolution measurements of the Coster-Kronig lines. The importance of electron correlation effects in couplings of potential energy curves leading to the 1s/sup 2/2pn/ell/ configurations is verified by means of Landau-Zener model calculations. 32 refs., 4 figs.

  6. Shock waves and double layers in a quantum electron-positron-ion plasma

    NASA Astrophysics Data System (ADS)

    Dip, P. R.; Hossen, M. A.; Salahuddin, M.; Mamun, A. A.

    2016-02-01

    The ion-acoustic (IA) shock waves and double layers (DLs) in an unmagnetized, dissipative, quantum electron-positron-ion (EPI) plasma (composed of a viscous heavy ion fluid, Fermi electrons and positrons) have been theoretically investigated. The higher-order Burgers and Gardner equations are derived by employing the reductive perturbation method. The basic features of the IA shock waves and the DLs are identified by analyzing the solutions of both the higher-order Burgers and Gardner equations. The ratio of the Fermi temperature of the positron to that of the electron, the Fermi pressure of electrons and positrons, the viscous force, the plasma particle number densities, etc. are found to change remarkably the basic features (viz. amplitude, width, phase speed, etc.) of the IA waves. The results of our investigation may be helpful in understanding the nonlinear features of localized IA waves propagating in quantum EPI plasmas which are ubiquitous in astrophysical, as well as laboratory, environments.

  7. Single- and double-electron detachment from H{sup {minus}} in collisions with He

    SciTech Connect

    Vikor, L.; Sarkadi, L.; Penent, F.; Bader, A.; Palinkas, J.

    1996-09-01

    The single- and double-electron detachment processes have been studied for 85 keV H{sup {minus}} on He collisions measuring the energy spectra of the electrons emitted in forward direction. In the spectrum belonging to the single-electron loss (SEL) the nonresonant part (cusp) has been resolved from the resonant part [lines from the (2{ital s}2{ital p}){sup 1}{ital P}{sup {ital o}} shape resonance of H{sup {minus}}]. The ratio of the integrated yield of the double-electron loss (DEL) to that of SEL was found to be 0.36{plus_minus}0.02. The yield of the cusp in the SEL spectrum was found to be surprisingly small, only (70{plus_minus}20){percent} of the yield of the cusp in the DEL spectrum. The formation of the cusp in SEL is interpreted as a result of dipolar interaction between the electron and the outgoing H{sup 0} atom. {copyright} {ital 1996 The American Physical Society.}

  8. Stabilizing nuclear spins around semiconductor electrons via the interplay of optical coherent population trapping and dynamic nuclear polarization

    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.

  9. Recent research directions in Fribourg: nuclear dynamics in resonances revealed by 2-dimensional EEL spectra, electron collisions with ionic liquids and electronic excitation of pyrimidine

    NASA Astrophysics Data System (ADS)

    Allan, Michael; Regeta, Khrystyna; Gorfinkiel, Jimena D.; Mašín, Zdeněk; Grimme, Stefan; Bannwarth, Christoph

    2016-05-01

    The article briefly reviews three subjects recently investigated in Fribourg: (i) electron collisions with surfaces of ionic liquids, (ii) two-dimensional (2D) electron energy loss spectra and (iii) resonances in absolute cross sections for electronic excitation of unsaturated compounds. Electron energy loss spectra of four ionic liquids revealed a number of excited states, including triplet states. A solution of a dye in an ionic liquid showed an energy-loss band of the solute, but not in all ionic liquids. 2D spectra reveal state-to-state information (given resonance to given final state) and are shown to be an interesting means to gain insight into dynamics of nuclear motion in resonances. Absolute cross sections for pyrimidine are reported as a function of scattering angle and as a function of electron energy. They reveal resonant structure which was reproduced very nicely by R-matrix calculations. The calculation provided an assignment of the resonances which reveals common patterns in compounds containing double bonds.

  10. Electron Dynamics upon Ionization of Polyatomic Molecules: Coupling to Quantum Nuclear Motion and Decoherence

    NASA Astrophysics Data System (ADS)

    Vacher, Morgane; Bearpark, Michael J.; Robb, Michael A.; Malhado, João Pedro

    2017-02-01

    Knowledge about the electronic motion in molecules is essential for our understanding of chemical reactions and biological processes. The advent of attosecond techniques opens up the possibility to induce electronic motion, observe it in real time, and potentially steer it. A fundamental question remains the factors influencing electronic decoherence and the role played by nuclear motion in this process. Here, we simulate the dynamics upon ionization of the polyatomic molecules paraxylene and modified bismethylene-adamantane, with a quantum mechanical treatment of both electron and nuclear dynamics using the direct dynamics variational multiconfigurational Gaussian method. Our simulations give new important physical insights about the expected decoherence process. We have shown that the decoherence of electron dynamics happens on the time scale of a few femtoseconds, with the interplay of different mechanisms: the dephasing is responsible for the fast decoherence while the nuclear overlap decay may actually help maintain it and is responsible for small revivals.

  11. Electron nuclear dynamics of LiH and HF in an intense laser field

    NASA Astrophysics Data System (ADS)

    Broeckhove, J.; Coutinho-Neto, M. D.; Deumens, E.; Öhrn, Y.

    1997-12-01

    The electron nuclear dynamics theory (END) extended to include a time-dependent external field is briefly described. The dynamical equations, in addition to the full electron nuclear coupling terms, now also contain the interactions of both the nuclei and the electrons with the external field. This extended END theory is applied to the study of vibrational excitations of the simple diatomics HF and LiH. The END results using an intense infrared laser field are compared with those of molecular dynamics as well as those from quantum wave-packet calculations. While the effect of the nonadiabatic electron-nuclear coupling terms on the vibrational dynamics is negligible for the chosen application, the electron-field coupling has a significant impact.

  12. Electron-Nuclear Dynamics of collision processes: Charge exchange and energy loss

    NASA Astrophysics Data System (ADS)

    Cabrera-Trujillo, Remigio; Sabin, John R.; Öhrn, Yngve; Deumens, Erik

    2004-03-01

    We present the Electron-Nuclear Dynamics (END) method for the study of time-dependent scattering processes. The END is a general approach for treating time-dependent problems which includes the dynamics of electrons and nuclei simultaneously by considering the full electron-nuclear coupling in the system and thus eliminates the necessity of constructing potential-energy surfaces. The theory approximates the time dependent Schrödinger equation starting from the time dependent variational principle by deriving a Hamiltonian dynamical system for time dependent nuclear and electronic wave function parameters. The wave function is described in a coherent state manifold, which leads to a system of Hamilton's equations of motion. Emphasis is put on electron exchange, differential cross section and energy loss (stopping cross section) of collision of ions, atoms and molecules involving H, He, C, N, O, and Ne atoms. We compare our results to available experimental data.

  13. Electron nuclear dynamics for a zig-zag chain of nitrogen atoms

    NASA Astrophysics Data System (ADS)

    Pohl, Anna; Calais, Jean-Louis

    1995-02-01

    We study the nitrogen zig-zag chain with two atoms per unit cell within the electron nuclear dynamics (END) formalism. This amounts to an approximate solution of the time-dependent Schrödinger equation for all the particles in the system. In the present approximation the nuclei are treated classically. The time dependence of the electronic motion is brought in through time-dependent linear combinations of fixed Bloch sums. This implies that the immediate mutual interaction between electronic and nuclear motion is taken into account. We investigate in particular the long-range terms of the interaction so as to arrive at convergent lattice sums. Before going to the general case when electronic and nuclear motion is coupled, we investigate the special cases of END traditional lattice dynamics and the random phase approximation (RPA) for the electrons.

  14. Communication: Adiabatic and non-adiabatic electron-nuclear motion: Quantum and classical dynamics.

    PubMed

    Albert, Julian; Kaiser, Dustin; Engel, Volker

    2016-05-07

    Using a model for coupled electronic-nuclear motion we investigate the range from negligible to strong non-adiabatic coupling. In the adiabatic case, the quantum dynamics proceeds in a single electronic state, whereas for strong coupling a complete transition between two adiabatic electronic states takes place. It is shown that in all coupling regimes the short-time wave-packet dynamics can be described using ensembles of classical trajectories in the phase space spanned by electronic and nuclear degrees of freedom. We thus provide an example which documents that the quantum concept of non-adiabatic transitions is not necessarily needed if electronic and nuclear motion is treated on the same footing.

  15. Electronic and nuclear motion and their couplings in the presence of a magnetic field

    NASA Astrophysics Data System (ADS)

    Schmelcher, P.; Cederbaum, L. S.; Meyer, H.-D.

    1988-12-01

    The performance of an adiabatic separation of electronic and nuclear motion in the presence of a magnetic field is examined, and it is shown that the diagonal term of the nonadiabatic coupling elements must be added to the nuclear equation of motion in the Born-Oppenheimer (BO) approximation. The screened BO approximation is described which is particularly suited to describe the adiabatic separation of electronic and nuclear degrees of freedom in a magnetic field. A new interpretation of the well-known gauge-centering is presented. The results are of interest in connection with the studies of white dwarfs and neutron stars.

  16. Optical detection and ionization of donors in specific electronic and nuclear spin States.

    PubMed

    Yang, A; Steger, M; Karaiskaj, D; Thewalt, M L W; Cardona, M; Itoh, K M; Riemann, H; Abrosimov, N V; Churbanov, M F; Gusev, A V; Bulanov, A D; Kaliteevskii, A K; Godisov, O N; Becker, P; Pohl, H-J; Ager, J W; Haller, E E

    2006-12-01

    We resolve the remarkably sharp bound exciton transitions of highly enriched 28Si using a single-frequency laser and photoluminescence excitation spectroscopy, as well as photocurrent spectroscopy. Well-resolved doublets in the spectrum of the 31P donor reflect the hyperfine coupling of the electronic and nuclear donor spins. The optical detection of the nuclear spin state, and selective pumping and ionization of donors in specific electronic and nuclear spin states, suggests a number of new possibilities which could be useful for the realization of silicon-based quantum computers.

  17. Correspondence of electron spectra from photoionization and nuclear internal conversion

    SciTech Connect

    Wark, D.L.; Bartlett, R.; Bowles, T.J.; Robertson, R.G.H.; Sivia, D.S.; Trela, W.; Wilkerson, J.F. ); Brown, G.S. ); Crasemann, B.; Sorensen, S.L.; Schaphorst, S.J. ); Knapp, D.A.; Henderson, J. ); Tulkki, J.; Aberg, T. )

    1991-10-21

    Electron energy spectra have been measured that result from {ital K}-shell ionization of Kr by two different mechanisms: (1) photoionization and (2) internal conversion in the decay of the isomeric state of {sup 83}Kr. It is demonstrated experimentally that these spectra, including satellites on the low-energy side of the primary 1{ital s}-electron peak, are identical. A theoretical interpretation of the identity of the spectra is given. The spectra agree well with a relativistic many-electron calculation in which the satellites are attributed to excitation and ionization of {ital M} and {ital N} electrons during the {ital K}-ionization process.

  18. Single-electron regime and Pauli spin blockade in a silicon metal-oxide-semiconductor double quantum dot

    NASA Astrophysics Data System (ADS)

    Rochette, Sophie; Ten Eyck, Gregory A.; Pluym, Tammy; Lilly, Michael P.; Carroll, Malcolm S.; Pioro-Ladrière, Michel

    2015-03-01

    Silicon quantum dots are promising candidates for quantum information processing as spin qubits with long coherence time. We present electrical transport measurements on a silicon metal-oxide-semiconductor (MOS) double quantum dot (DQD). First, Coulomb diamonds measurements demonstrate the one-electron regime at a relatively high temperature of 1.5 K. Then, the 8 mK stability diagram shows Pauli spin blockade with a large singlet-triplet separation of approximatively 0.40 meV, pointing towards a strong lifting of the valley degeneracy. Finally, numerical simulations indicate that by integrating a micro-magnet to those devices, we could achieve fast spin rotations of the order of 30 ns. Those results are part of the recent body of work demonstrating the potential of Si MOS DQD as reliable and long-lived spin qubits that could be ultimately integrated into modern electronic facilities. 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.

  19. An Essential Role for Nuclear Factor κB in Promoting Double Positive Thymocyte Apoptosis

    PubMed Central

    Hettmann, Thore; DiDonato, Joseph; Karin, Michael; Leiden, Jeffrey M.

    1999-01-01

    To examine the role of nuclear factor (NF)-κB in T cell development and activation in vivo, we produced transgenic mice that express a superinhibitory mutant form of inhibitor κB-α (IκB-αA32/36) under the control of the T cell–specific CD2 promoter and enhancer (mutant [m]IκB-α mice). Thymocyte development proceeded normally in the mIκB-α mice. However, the numbers of peripheral CD8+ T cells were significantly reduced in these animals. The mIκB-α thymocytes displayed a marked proliferative defect and significant reductions in interleukin (IL)-2, IL-3, and granulocyte/macrophage colony-stimulating factor production after cross-linking of the T cell antigen receptor. Perhaps more unexpectedly, double positive (CD4+CD8+; DP) thymocytes from the mIκB-α mice were resistant to α-CD3–mediated apoptosis in vivo. In contrast, they remained sensitive to apoptosis induced by γ-irradiation. Apoptosis of wild-type DP thymocytes after in vivo administration of α-CD3 mAb was preceded by a significant reduction in the level of expression of the antiapoptotic gene, bcl-xL. In contrast, the DP mIκB-α thymocytes maintained high level expression of bcl-xL after α-CD3 treatment. Taken together, these results demonstrated important roles for NF-κB in both inducible cytokine expression and T cell proliferation after TCR engagement. In addition, NF-κB is required for the α-CD3–mediated apoptosis of DP thymocytes through a pathway that involves the regulation of the antiapoptotic gene, bcl-xL. PMID:9874571

  20. Concerted double proton-transfer electron-transfer between catechol and superoxide radical anion.

    PubMed

    Quintero-Saumeth, Jorge; Rincón, David A; Doerr, Markus; Daza, Martha C

    2017-09-20

    We have carried out a computational study on the reactivity of catechol (1,2-dihydroxybenzene) towards superoxide radical anion (O2˙(-)) in water, N,N-dimethylformamide (DMF), pentyl ethanoate (PEA) and vacuum using density functional theory and the coupled cluster method. Five reaction mechanisms were studied: (i) sequential proton transfer followed by hydrogen atom transfer (PT-HT), (ii) sequential hydrogen atom transfer followed by proton transfer (HT-PT), (iii) single electron transfer (SET), (iv) radical adduct formation (RAF) and (v) concerted double proton-transfer electron-transfer (denoted as global reaction, GR). Our results show that catechol and superoxide do not react via a sequential reaction mechanism (initial PT, initial HAT or SET). Instead, the reaction proceeds via a concerted double proton-transfer electron-transfer mechanism yielding hydrogen peroxide and catechol radical anion. The protons are transferred asynchronously between the σ orbitals of the catechol oxygen atoms to superoxide, while the electron is transferred between oxygen π orbitals in the same direction. The calculated rate constants in aqueous media agree with the experimental values reported in the literature. This suggests that the mechanism proposed in this work is adequate to describe this reaction. In addition, our results show that the reaction exhibits a large tunneling effect.

  1. Solid effect in the electron spin dressed state: A new approach for dynamic nuclear polarization

    NASA Astrophysics Data System (ADS)

    Weis, V.; Bennati, M.; Rosay, M.; Griffin, R. G.

    2000-10-01

    We describe a new type of solid effect for dynamic nuclear polarization (DNP) that is based on simultaneous, near resonant microwave (mw) and radio frequency (rf) irradiation of a coupled electron nuclear spin system. The interaction of the electron spin with the mw field is treated as an electron spin dressed state. In contrast to the customary laboratory frame solid effect, it is possible to obtain nuclear polarization with the dressed state solid effect (DSSE) even in the absence of nonsecular hyperfine coupling. Efficient, selective excitation of dressed state transitions generates nuclear polarization in the nuclear laboratory frame on a time scale of tens of μs, depending on the strength of the electron-nuclear coupling, the mw and rf offset and field strength. The experiment employs both pulsed mw and rf irradiation at a repetition rate comparable to T1e-1, where T1e is the electronic spin lattice relaxation time. The DSSE is demonstrated on a perdeuterated BDPA radical in a protonated matrix of polystyrene.

  2. Correlated electron-nuclear dynamics in above-threshold multiphoton ionization of asymmetric molecule

    PubMed Central

    Wang, Zhuo; Li, Min; Zhou, Yueming; Lan, Pengfei; Lu, Peixiang

    2017-01-01

    The partition of the photon energy into the subsystems of molecules determines many photon-induced chemical and physical dynamics in laser-molecule interactions. The electron-nuclear energy sharing from multiphoton ionization of molecules has been used to uncover the correlated dynamics of the electron and fragments. However, most previous studies focus on symmetric molecules. Here we study the electron-nuclear energy sharing in strong-field photoionization of HeH2+ by solving the one-dimensional time-dependent Schrödinger equation (TDSE). Compared with symmetric molecules, the joint electron-nuclear energy spectrum (JES) of HeH2+ reveals an anomalous energy shift at certain nuclear energies, while it disappears at higher and lower nuclear energies. Through tracing the time evolution of the wavepacket of bound states, we identify that this energy shift originates from the joint effect of the Stark shift, associated with the permanent dipole, and the Autler-Townes effect due to the coupling of the 2pσ and 2sσ states in strong fields. The energy shift in the JES appears at certain nuclear distances only when both Stark effect and Autler-Townes effect play important roles. We further demonstrate that the electron-nuclei energy sharing can be controlled by varying laser intensity for asymmetric molecules, providing alternative approaches to manipulate photochemical reactions for more complex molecules. PMID:28218294

  3. Correlated electron-nuclear dynamics in above-threshold multiphoton ionization of asymmetric molecule.

    PubMed

    Wang, Zhuo; Li, Min; Zhou, Yueming; Lan, Pengfei; Lu, Peixiang

    2017-02-20

    The partition of the photon energy into the subsystems of molecules determines many photon-induced chemical and physical dynamics in laser-molecule interactions. The electron-nuclear energy sharing from multiphoton ionization of molecules has been used to uncover the correlated dynamics of the electron and fragments. However, most previous studies focus on symmetric molecules. Here we study the electron-nuclear energy sharing in strong-field photoionization of HeH(2+) by solving the one-dimensional time-dependent Schrödinger equation (TDSE). Compared with symmetric molecules, the joint electron-nuclear energy spectrum (JES) of HeH(2+) reveals an anomalous energy shift at certain nuclear energies, while it disappears at higher and lower nuclear energies. Through tracing the time evolution of the wavepacket of bound states, we identify that this energy shift originates from the joint effect of the Stark shift, associated with the permanent dipole, and the Autler-Townes effect due to the coupling of the 2pσ and 2sσ states in strong fields. The energy shift in the JES appears at certain nuclear distances only when both Stark effect and Autler-Townes effect play important roles. We further demonstrate that the electron-nuclei energy sharing can be controlled by varying laser intensity for asymmetric molecules, providing alternative approaches to manipulate photochemical reactions for more complex molecules.

  4. Correlated electron-nuclear dynamics in above-threshold multiphoton ionization of asymmetric molecule

    NASA Astrophysics Data System (ADS)

    Wang, Zhuo; Li, Min; Zhou, Yueming; Lan, Pengfei; Lu, Peixiang

    2017-02-01

    The partition of the photon energy into the subsystems of molecules determines many photon-induced chemical and physical dynamics in laser-molecule interactions. The electron-nuclear energy sharing from multiphoton ionization of molecules has been used to uncover the correlated dynamics of the electron and fragments. However, most previous studies focus on symmetric molecules. Here we study the electron-nuclear energy sharing in strong-field photoionization of HeH2+ by solving the one-dimensional time-dependent Schrödinger equation (TDSE). Compared with symmetric molecules, the joint electron-nuclear energy spectrum (JES) of HeH2+ reveals an anomalous energy shift at certain nuclear energies, while it disappears at higher and lower nuclear energies. Through tracing the time evolution of the wavepacket of bound states, we identify that this energy shift originates from the joint effect of the Stark shift, associated with the permanent dipole, and the Autler-Townes effect due to the coupling of the 2pσ and 2sσ states in strong fields. The energy shift in the JES appears at certain nuclear distances only when both Stark effect and Autler-Townes effect play important roles. We further demonstrate that the electron-nuclei energy sharing can be controlled by varying laser intensity for asymmetric molecules, providing alternative approaches to manipulate photochemical reactions for more complex molecules.

  5. Direct and secondary nuclear excitation with x-ray free-electron lasers

    SciTech Connect

    Gunst, Jonas; Wu, Yuanbin Kumar, Naveen; Keitel, Christoph H.; Pálffy, Adriana

    2015-11-15

    The direct and secondary nuclear excitation produced by an x-ray free electron laser when interacting with a solid-state nuclear target is investigated theoretically. When driven at the resonance energy, the x-ray free electron laser can produce direct photoexcitation. However, the dominant process in that interaction is the photoelectric effect producing a cold and very dense plasma in which also secondary processes such as nuclear excitation by electron capture may occur. We develop a realistic theoretical model to quantify the temporal dynamics of the plasma and the magnitude of the secondary excitation therein. Numerical results show that depending on the nuclear transition energy and the temperature and charge states reached in the plasma, secondary nuclear excitation by electron capture may dominate the direct photoexcitation by several orders of magnitude, as it is the case for the 4.8 keV transition from the isomeric state of {sup 93}Mo, or it can be negligible, as it is the case for the 14.4 keV Mössbauer transition in {sup 57}Fe. These findings are most relevant for future nuclear quantum optics experiments at x-ray free electron laser facilities.

  6. Evidence for Electron Antineutrino Oscillations with the Double Chooz Far Detector

    NASA Astrophysics Data System (ADS)

    Felde, John W.

    Until recently, the neutrino mixing parameter, theta 13, was unknown. A number of experiments were designed to measure this parameter as it will have a significant impact on future neutrino oscillation research. One such experiment, Double Chooz, measures the disappearance of reactor antineutrinos with a single, 8.3 ton, gadolinium loaded liquid scintillator detector at a baseline of about 1km from two 4.25GWth nuclear power reactors located in Chooz, France. Current results from Double Chooz, along with other reactor and accelerator based experiments, have confirmed that theta 13 is nonzero, and all measurements agree that sin2 (2theta 13) ≃ 0.1. In an independent analysis of 234.77 live days, including 6.84 live days when both reactors were off, a new technique was used to evaluate the Double Chooz data. In this analysis, a comparison between the observed and predicted detection rates as well as the energy spectra were used to determine a best fit of sin2 (2theta13) = 0.105 +/- 0.030. This measurement confirms, and improves upon, the results found by previous analyses. Excellent agreement is also found between this measurement and other experiments. ii

  7. Bright-field scanning confocal electron microscopy using a double aberration-corrected transmission electron microscope.

    PubMed

    Wang, Peng; Behan, Gavin; Kirkland, Angus I; Nellist, Peter D; Cosgriff, Eireann C; D'Alfonso, Adrian J; Morgan, Andrew J; Allen, Leslie J; Hashimoto, Ayako; Takeguchi, Masaki; Mitsuishi, Kazutaka; Shimojo, Masayuki

    2011-06-01

    Scanning confocal electron microscopy (SCEM) offers a mechanism for three-dimensional imaging of materials, which makes use of the reduced depth of field in an aberration-corrected transmission electron microscope. The simplest configuration of SCEM is the bright-field mode. In this paper we present experimental data and simulations showing the form of bright-field SCEM images. We show that the depth dependence of the three-dimensional image can be explained in terms of two-dimensional images formed in the detector plane. For a crystalline sample, this so-called probe image is shown to be similar to a conventional diffraction pattern. Experimental results and simulations show how the diffracted probes in this image are elongated in thicker crystals and the use of this elongation to estimate sample thickness is explored.

  8. Efficiency enhancement of planar perovskite solar cells by adding zwitterion/LiF double interlayers for electron collection.

    PubMed

    Sun, Kuan; Chang, Jingjing; Isikgor, Furkan Halis; Li, Pengcheng; Ouyang, Jianyong

    2015-01-21

    Double interlayers consisting of a zwitterionic small molecule layer and a LiF layer were introduced between the electron transport layer and the cathode of perovskite solar cells. The double interlayers improve the photovoltaic efficiency to 13.2%, which is higher than that of control devices without the double interlayer (9.2%) or with LiF (11.0%) or rhodamine 101 zwitterion (12.1%) alone.

  9. Asymmetric electron energy sharing in electron-impact double ionization of helium

    NASA Astrophysics Data System (ADS)

    Silenou Mengoue, M.; Tetchou Nganso, H. M.

    2016-12-01

    We present the fully fivefold differential cross sections (FDCSs) for (e ,3 e ) processes in helium within the first Born approximation. The calculation is performed for a coplanar geometry in which the incident electron is fast (˜6 keV), the momentum transfer is small (0.24 a.u.), and for an asymmetric energy sharing between both slow ejected electrons at excess energy of 20 eV. Two cases have been considered: E1=15 eV, E2=5 eV and E1=8 eV, E2=12 eV. While waiting for new theoretical and experimental results for confrontations, in particular for asymmetric energy sharing, our results clearly demonstrate that, for the same incident energy, the same momentum transfer and the same excess energy, the (e ,3 e ) process in helium with asymmetric energy sharing between ejected electrons is more likely than the case with symmetric energy sharing. The two- and three-dimensional representation of the FDCSs covering all possible values of the angle of ejections are presented and discussed. The theoretical cross sections are calculated by using a compact-kernel-integral-equation approach associated with the Jacobi matrix method to calculate a three-body wave function and which leads to a full convergence in terms of the basis size.

  10. Ion Acoustic Solitons and Double Layers in the Solar Wind Having Kappa Distributed Electrons

    NASA Astrophysics Data System (ADS)

    Lakhina, G. S.; Singh, S. V.

    2015-12-01

    It is shown that two types of, slow and fast, ion-acoustic solitary waves can occur in a solar wind plasma consisting of fluid hot protons, hot alpha particles streaming with respect to protons, and suprathermal electrons having k- distribution. The fast ion-acoustic mode is similar to the ion-acoustic mode of proton-electron plasma, and can support only positive potential solitons. The slow ion-acoustic mode is a new mode that occurs due to the presence of alpha particles. This mode can support both positive and negative solitons and double layers. The slow ion-acoustic mode can exist even when the relative streaming, U0, between alphas and protons is zero, provided alpha temperature, Ti, is not exactly equal to 4 times the proton temperature, Tp. An increase of the k- index leads to an increase in the critical Mach number, maximum Mach number and the maximum amplitude of both slow and fast ion-acoustic solitons. The model can explain the amplitudes and widths, but not shapes, of the weak double layers (WDLs) observed in the solar wind at 1 AU by Wind spacecraft in terms of slow ion-acoustic double layers. It is proposed that both slow and fast ion-acoustic solitons may be responsible for the ion- acoustic like wave activity in the solar wind.

  11. Electronic Structure of Graphene and Germanene Based on Double Hexagonal Structure

    NASA Astrophysics Data System (ADS)

    Naji, S.; Belhaj, A.; Labrim, H.; Benyoussef, A.; El Kenz, A.

    2013-11-01

    In this paper, we study the electronic structure of monolayer materials based on a double hexagonal geometry with (1×1) and (√ 3 × √ 3)R30o superstructures. Inspired from the two-dimensional root system of an exceptional Lie algebra called G2, this hexagonal atomic configuration involves two hexagons of unequal side length at angle 30°. The principal unit hexagonal cell contains twelve atoms instead of the usual configuration involving only six ones relying only on the (1×1) superstructure. Using ab initio calculations based on FPLO9.00-34 code, we investigate numerically the graphene and the germanene with the double hexagonal geometry. In particular, we find that the usual electronic properties and the lattice parameters of such materials are modified. More precisely, the lattice parameters are increased. It has been shown that, in the single hexagonal geometry, the grapheme and the germanene behave as a gapless semiconductor and a semi-metallic, respectively. In double hexagonal geometry however, both materials becomes metallic.

  12. Electronic decoherence following photoionization: Full quantum-dynamical treatment of the influence of nuclear motion

    NASA Astrophysics Data System (ADS)

    Arnold, Caroline; Vendrell, Oriol; Santra, Robin

    2017-03-01

    Photoionization using attosecond pulses can lead to the formation of coherent superpositions of the electronic states of the parent ion. However, ultrafast electron ejection triggers not only electronic but also nuclear dynamics—leading to electronic decoherence, which is typically neglected on time scales up to tens of femtoseconds. We propose a full quantum-dynamical treatment of nuclear motion in an adiabatic framework, where nuclear wave packets move on adiabatic potential energy surfaces expanded up to second order at the Franck-Condon point. We show that electronic decoherence is caused by the interplay of a large number of nuclear degrees of freedom and by the relative topology of the potential energy surfaces. Application to H2O , paraxylene, and phenylalanine shows that an initially coherent state evolves to an electronically mixed state within just a few femtoseconds. In these examples the fast vibrations involving hydrogen atoms do not affect electronic coherence at short times. Conversely, vibrational modes involving the whole molecular skeleton, which are slow in the ground electronic state, quickly destroy it upon photoionization.

  13. Role of nonthermal electrons on dust ion acoustic double layer with variable dust charge

    NASA Astrophysics Data System (ADS)

    Borah, Prathana; Gogoi, Deepshikha; Das, Nilakshi

    2016-01-01

    The presence of nonthermal electron may play an important role in the formation of nonlinear structures in plasma. On the other hand, fluctuation of dust charge is an important and unique feature of complex plasma and it gives rise to a dissipative effect in the system leading to the formation of nonlinear structures due to the balance between nonlinearity and dissipation. In this paper, the propagation of nonlinear dust ion acoustic (DIA) wave in unmagnetized collisionless dusty plasma consisting of ions, nonthermal electrons and dust grains with variable negative charge has been investigated using the Sagdeev potential method. The existence domain of rarefactive double layer (DL) in the DIA wave has been investigated for the range of plasma parameters. The real potential has been obtained by numerically solving the Poisson equation and dust charging equation. It is observed that the presence of nonthermal electrons strengthens the DIA DL.

  14. A double-layer based model of ion confinement in electron cyclotron resonance ion source

    SciTech Connect

    Mascali, D. Neri, L.; Celona, L.; Castro, G.; Gammino, S.; Ciavola, G.; Torrisi, G.; Sorbello, G.

    2014-02-15

    The paper proposes a new model of ion confinement in ECRIS, which can be easily generalized to any magnetic configuration characterized by closed magnetic surfaces. Traditionally, ion confinement in B-min configurations is ascribed to a negative potential dip due to superhot electrons, adiabatically confined by the magneto-static field. However, kinetic simulations including RF heating affected by cavity modes structures indicate that high energy electrons populate just a thin slab overlapping the ECR layer, while their density drops down of more than one order of magnitude outside. Ions, instead, diffuse across the electron layer due to their high collisionality. This is the proper physical condition to establish a double-layer (DL) configuration which self-consistently originates a potential barrier; this “barrier” confines the ions inside the plasma core surrounded by the ECR surface. The paper will describe a simplified ion confinement model based on plasma density non-homogeneity and DL formation.

  15. Non uniform shrinkages of double-walled carbon nanotube as induced by electron beam irradiation

    SciTech Connect

    Zhu, Xianfang Li, Lunxiong; Gong, Huimin; Yang, Lan; Sun, Chenghua

    2014-09-01

    Electron beam-induced nanoinstabilities of pristine double-walled carbon nanotubes (DWCNTs) of two different configurations, one fixed at both ends and another fixed at only one end, were in-situ investigated in transmission electron microscope at room temperature. It was observed that the DWCNT fixed at both ends shrank in its diameter uniformly. Meanwhile, the DWCNT fixed at only one end intriguingly shrank preferentially from its free cap end along its axial direction whereas its diameter shrinkage was offset. A mechanism of “diffusion” along with “evaporation” at room temperature which is driven by the nanocurvature of the DWCNTs, and the athermal activation induced by the electron beam was proposed to elucidate the observed phenomena. The effect of the interlayer interaction of the DWCNTs was also discussed.

  16. Electron-nuclear wave-packet dynamics through a conical intersection

    NASA Astrophysics Data System (ADS)

    Hader, Kilian; Albert, Julian; Gross, E. K. U.; Engel, Volker

    2017-02-01

    We investigate the coupled electron-nuclear dynamics in a model system showing a conical intersection (CoIn) between two excited state potential energy surfaces. Within the model, a single electron and nucleus move in two dimensions in an external static field. It is demonstrated that the nuclear density conserves its initial Gaussian shape when directly passing the CoIn, whereas the electronic density remains approximately constant. This is in sharp contrast to the picture which evolves from an analysis within the basis of adiabatic electronic states. There, dramatic changes are seen in the dynamics of the different nuclear components of the total wave function. It is thus documented that, in the case of a highly efficient population transfer between the respective adiabatic states, neither the nuclear nor the electronic density is influenced by the existence of a CoIn. This is the case because the nuclear-electronic wave packet moves on the complete potential energy surface which changes its topology smoothly as a function of all particle coordinates.

  17. Electron dynamics following photoionization: Decoherence due to the nuclear-wave-packet width

    NASA Astrophysics Data System (ADS)

    Vacher, Morgane; Steinberg, Lee; Jenkins, Andrew J.; Bearpark, Michael J.; Robb, Michael A.

    2015-10-01

    The advent of attosecond techniques opens up the possibility to observe experimentally electron dynamics following ionization of molecules. Theoretical studies of pure electron dynamics at single fixed nuclear geometries in molecules have demonstrated oscillatory charge migration at a well-defined frequency but often neglecting the natural width of the nuclear wave packet. The effect on electron dynamics of the spatial delocalization of the nuclei is an outstanding question. Here, we show how the inherent distribution of nuclear geometries leads to dephasing. Using a simple analytical model, we demonstrate that the conditions for a long-lived electronic coherence are a narrow nuclear wave packet and almost parallel potential-energy surfaces of the states involved. We demonstrate with numerical simulations the decoherence of electron dynamics for two real molecular systems (paraxylene and polycyclic norbornadiene), which exhibit different decoherence time scales. To represent the quantum distribution of geometries of the nuclear wave packet, the Wigner distribution function is used. The electron dynamics decoherence result has significant implications for the interpretation of attosecond spectroscopy experiments since one no longer expects long-lived oscillations.

  18. The multi-configuration electron-nuclear dynamics method applied to LiH.

    PubMed

    Ulusoy, Inga S; Nest, Mathias

    2012-02-07

    The multi-configuration electron-nuclear dynamics (MCEND) method is a nonadiabatic quantum dynamics approach to the description of molecular processes. MCEND is a combination of the multi-configuration time-dependent Hartree (MCTDH) method for atoms and its antisymmetrized equivalent MCTDHF for electrons. The purpose of this method is to simultaneously describe nuclear and electronic wave packets in a quantum dynamical way, without the need to calculate potential energy surfaces and diabatic coupling functions. In this paper we present first exemplary calculations of MCEND applied to the LiH molecule, and discuss computational and numerical details of our implementation.

  19. Electron nuclear dynamics of H + +H2 collisions at Elab=30 eV

    NASA Astrophysics Data System (ADS)

    Morales, Jorge; Diz, Agustin; Deumens, E.; Öhrn, Yngve

    1995-12-01

    Proton collisions with hydrogen molecules at 30 eV in the laboratory frame is a simple ion-molecule system exhibiting a number of distinct processes such as inelastic scattering, charge transfer, rearrangement, and dissociation. The electron nuclear dynamics (END) theory which allows full electron nuclear coupling and which does not restrict the system from reaching any of the possible product channels, is applied to this sytem to produce transition probabilities, differential, and integral (vibrationally resolved) cross sections. Comparisons with experiment demonstrate that END, even in its simplest implementation, with a single determinantal state for the electrons and with classical nuclei, yields results that are competitive with other theoretical approaches.

  20. Nuclear quantum and electronic exchange-correlation effects on the high pressure phase diagram of lithium

    NASA Astrophysics Data System (ADS)

    Clay, Raymond; Morales, Miguel; Bonev, Stanimir

    Lithium at ambient conditions is the simplest alkali metal and exhibits textbook nearly-free electron character. However, increased core/valence electron overlap under compression leads to surprisingly complex behavior. Dense lithium is known to posses a maximum in the melting line, a metal to semiconductor phase transition around 80GPa, reemergent metallicity around 120GPa, and low coordination solid and liquid phases. In addition to its complex electronic structure at high pressure, the atomic mass of lithium is low enough that nuclear quantum effects could have a nontrivial impact on its phase diagram. Through a combination of density functional theory based path-integral and classical molecular dynamics simulations, we have investigated the impact of both nuclear quantum effects and anharmonicity on the melting line and solid phase boundaries. Additionally, we have determined the robustness of previously predicted tetrahedral clustering in the dense liquid to the inclusion of nuclear quantum effects and approximate treatment of electronic exchange-correlation effects.

  1. Electron recombination in low-energy nuclear recoils tracks in liquid argon

    NASA Astrophysics Data System (ADS)

    Wojcik, M.

    2016-02-01

    This paper presents an analysis of electron-ion recombination processes in ionization tracks of recoiled atoms in liquid argon (LAr) detectors. The analysis is based on the results of computer simulations which use realistic models of electron transport and reactions. The calculations reproduce the recent experimental results of the ionization yield from 6.7 keV nuclear recoils in LAr. The statistical distribution of the number of electrons that escape recombination is found to deviate from the binomial distribution, and estimates of recombination fluctuations for nuclear recoils tracks are obtained. A study of the recombination kinetics shows that a significant part of electrons undergo very fast static recombination, an effect that may be responsible for the weak drift-field dependence of the ionization yield from nuclear recoils in some noble liquids. The obtained results can be useful in the search for hypothetical dark matter particles and in other studies that involve detection of recoiled nuclei.

  2. Observation of electron hole, double layer, and turbulent heating in a laboratory plasma

    NASA Astrophysics Data System (ADS)

    Tsukishima, T.; Inuzuka, H.

    1990-08-01

    Nonlinear phenomena such as electron hole, double layer, and turbulent heating, which were observed in a linear mirror device, THE NU-II, are reviewed. Observations were carried out with a temporal resolution of 2 ns and a spatial resolution of 1 mm, respectively. Upon applying a voltage difference of the order of 10 kV between two electrodes inserted in the cylindrical plasma at a distance of 67 cm, the nonlinear phenomena evolved consecutively. In particular, a strong current limited double layer was formed, and its lifetime was found to satisfy a simple empirical law. One dimensional computer simulations based on a kinetic code were carried out with boundary conditions close to the experimental ones. The effect of magnetic field was taken into consideration in the simulations.

  3. Energy and angle differential cross sections for the electron-impact double ionization of helium

    SciTech Connect

    Colgan, James P; Pindzola, M S; Robicheaux, F

    2008-01-01

    Energy and angle differential cross sections for the electron-impact double ionization of helium are calculated using a non-perturbative time-dependent close-coupling method. Collision probabilities are found by projection of a time evolved nine dimensional coordinate space wave function onto fully antisymmetric products of spatial and spin functions representing three outgoing Coulomb waves. At an incident energy of 106 eV, we present double energy differential cross sections and pentuple energy and angle differential cross sections. The pentuple energy and angle differential cross sections are found to be in relative agreement with the shapes observed in recent (e,3e) reaction microscope experiments. Integration of the differential cross sections over all energies and angles yields a total ionization cross section that is also in reasonable agreement with absolute crossed-beams experiments.

  4. First Principles Study of Electronic and Magnetic Structures in Double Perovskites

    NASA Astrophysics Data System (ADS)

    Ball, Molly

    At present, electronic devices are reaching their storage and processing limit causing a major push to find materials that can be used in the next generation of devices. Double perovskites with A2BB'O 6 stoichiometry form one of the leading classes of materials currently being studied as a potential candidate because of their extremely wide range and tunability of functional properties, along with economic and highly scalable synthesis routes. Having a thorough understanding of their electronic and magnetic structure and their dependence on composition and local structure is the basis for targeted development of novel and optimized double perovskites. While the body of knowledge and rules within the field of materials chemistry has enabled many previous discoveries, recent developments within density functional theory (DFT) allow by now a rather realistic description of the electronic and magnetic properties of materials and especially identification of their origin from geometry and orbital structure. This thesis details computational work based on DFT within several collaborative studies to better understand the electronic and magnetic properties of double perovskites and related materials that show promise for future use in multifunctional devices. First, we will begin with a general introduction to the double perovskite structure, their properties, and the computational methods used to study them. In the next section, we will look at the case of the antiferromagnetic, insulating double perovskite Sr2CoOsO6, where measurements showed that the transition metal ions in the two sublattices undergo magnetic ordering independently of each other, indicating weak magnetic short-range coupling and a dominance of longer-range interactions, which has previously not been observed. Here, we performed DFT calculations to extract the exchange strengths between the ions and explain this unique dominance of the long-range interactions. Then, we will look at studies done on thin

  5. Hybrid Orbital and Numerical Grid Representationfor Electronic Continuum Processes: Double Photoionization of Atomic Beryllium

    SciTech Connect

    Yip, Frank L; McCurdy, C. William; Rescigno, Thomas N

    2010-04-19

    A general approach for ab initio calculations of electronic continuum processes is described in which the many-electron wave function is expanded using a combination of orbitals at short range and the finite-element discrete variable representation(FEM-DVR) at larger distances. The orbital portion of the basis allows the efficient construction of many-electron configurations in which some of the electrons are bound, but because the orbitals are constructed from an underlying FEM-DVR grid, the calculation of two-electron integrals retains the efficiency of the primitive FEM-DVR approach. As an example, double photoionization of beryllium is treated in a calculation in which the 1s{sup 2} core is frozen. This approach extends the use of exterior complex scaling (ECS) successfully applied to helium and H{sub 2} to calculations with two active electrons on more complicated targets. Integrated, energy-differential and triply-differential cross sections are exhibited, and the results agree well with other theoretical investigations.

  6. On the generation of double layers from ion- and electron-acoustic instabilities

    SciTech Connect

    Fu, Xiangrong Cowee, Misa M.; Winske, Dan; Gary, S. Peter

    2016-03-15

    A plasma double layer (DL) is a nonlinear electrostatic structure that carries a uni-polar electric field parallel to the background magnetic field due to local charge separation. Past studies showed that DLs observed in space plasmas are mostly associated with the ion acoustic instability. Recent Van Allen Probes observations of parallel electric field structures traveling much faster than the ion acoustic speed have motivated a computational study to test the hypothesis that a new type of DLs—electron acoustic DLs—generated from the electron acoustic instability are responsible for these electric fields. Nonlinear particle-in-cell simulations yield negative results, i.e., the hypothetical electron acoustic DLs cannot be formed in a way similar to ion acoustic DLs. Linear theory analysis and the simulations show that the frequencies of electron acoustic waves are too high for ions to respond and maintain charge separation required by DLs. However, our results do show that local density perturbations in a two-electron-component plasma can result in unipolar-like electric field structures that propagate at the electron thermal speed, suggesting another potential explanation for the observations.

  7. On the generation of double layers from ion- and electron-acoustic instabilities

    NASA Astrophysics Data System (ADS)

    Fu, Xiangrong; Cowee, Misa M.; Gary, S. Peter; Winske, Dan

    2016-03-01

    A plasma double layer (DL) is a nonlinear electrostatic structure that carries a uni-polar electric field parallel to the background magnetic field due to local charge separation. Past studies showed that DLs observed in space plasmas are mostly associated with the ion acoustic instability. Recent Van Allen Probes observations of parallel electric field structures traveling much faster than the ion acoustic speed have motivated a computational study to test the hypothesis that a new type of DLs—electron acoustic DLs—generated from the electron acoustic instability are responsible for these electric fields. Nonlinear particle-in-cell simulations yield negative results, i.e., the hypothetical electron acoustic DLs cannot be formed in a way similar to ion acoustic DLs. Linear theory analysis and the simulations show that the frequencies of electron acoustic waves are too high for ions to respond and maintain charge separation required by DLs. However, our results do show that local density perturbations in a two-electron-component plasma can result in unipolar-like electric field structures that propagate at the electron thermal speed, suggesting another potential explanation for the observations.

  8. On the generation of double layers from ion- and electron-acoustic instabilities

    DOE PAGES

    Fu, Xiangrong; Cowee, Misa M.; Gary, Stephen Peter; ...

    2016-03-17

    A plasma double layer (DL) is a nonlinear electrostatic structure that carries a uni-polar electric field parallel to the background magnetic field due to local charge separation. Past studies showed that DLs observed in space plasmas are mostly associated with the ion acoustic instability. Recent Van Allen Probes observations of parallel electric fields traveling much faster than the ion acoustic speed have motivated a computational study to test the hypothesis that a new type of DLs – electron acoustic DLs – generated from the electron acoustic instability are responsible for these electric fields. Nonlinear particle-in-cell simulations yield negative results, i.e.more » the hypothetical electron acoustic DLs cannot be formed in a way similar to ion acoustic DLs. We find that linear theory analysis and the simulations show that the frequencies of electron acoustic waves are too high for ions to respond and maintain charge separation required by DLs. However, our results do show that local density perturbations in a two-electron-component plasma can result in unipolar-like electric fields that propagate at the electron thermal speed, suggesting another potential explanation for the observations.« less

  9. Small amplitude electron-acoustic double layers and solitons in fully relativistic plasmas of two-temperature electrons

    SciTech Connect

    Lee, Nam C.

    2009-04-15

    A Korteweg-de Vries (KdV) equation for fully relativistic one dimensional plasmas of arbitrarily large streaming speed and temperature is derived by using the reductive perturbation method. For plasmas with more than two species of particles, the coefficient representing quadratic nonlinearity in KdV can vanish at critical values of certain parameters. To describe the nonlinear evolution at this critical parameter, a modified KdV (mKdV) equation that contains a cubic nonlinear term is obtained. Furthermore, a mixed mKdV equation pertaining to parameters in the vicinity of the critical values is also derived, in which the quadratic and cubic nonlinearities are both present. As an illustration of the results, the mixed mKdV equation is applied to a plasma comprised of cold ions and electrons having cold (T=0) and finite temperature components. For warm temperature T<electron-acoustic nonlinear waves in the shape of double layer (kink) and solitary waves can exist, which have phase speed {radical}(3T/(4+{alpha})m{sub e}) in the rest frame of plasma, where {alpha} is the polytropic index of the equation of state of the warm electrons. The thickness of the transitional layer of the kink structure is of the order of Debye length {lambda}{sub D}. For extremely high temperature T>>m{sub e}c{sup 2}, it is also found that double layer and soliton-type solutions can exist with phase speed {radical}({alpha}-1)c, which is equal to the well known relativistic sound speed c/{radical}(3) for {alpha}=4/3. The thickness of the transition layer scales as {delta}{approx}T{sup -1/4}, which is different from the T<

  10. Dynamics of electron emission in double photoionization processes near the krypton 3d threshold

    NASA Astrophysics Data System (ADS)

    Penent, F.; Sheinerman, S.; Andric, L.; Lablanquie, P.; Palaudoux, J.; Becker, U.; Braune, M.; Viefhaus, J.; Eland, J. H. D.

    2008-02-01

    Two-electron emission following photoabsorption near the Kr 3d threshold is investigated both experimentally and theoretically. On the experimental side, electron/electron coincidences using a magnetic bottle time-of-flight spectrometer allow us to observe the complete double photo ionization (DPI) continua of selected Kr2+ final states, and to see how these continua are affected by resonant processes in the vicinity of the Kr 3d threshold. The analysis is based on a quantum mechanical approach that takes into account the contribution of three different processes: (A) Auger decay of the inner 3d vacancy with the associated post-collision interaction (PCI) effects, (B) capture of slow photoelectrons into discrete states followed by valence multiplet decay (VMD) of the excited ionic states and (C) valence shell DPI. The dominant process for each Kr2+(4p-2) final state is the photoionization of the inner shell followed by Auger decay of the 3d vacancies. Moreover, for the 4p-2(3P) and 4p-2(1D) final ionic states an important contribution comes from the processes of slow photoelectron capture followed by VMD as well as from double ionization of the outer shell involving also VMD.

  11. Double K -shell vacancy production in the electron capture decay of sup 139 Ce

    SciTech Connect

    Hindi, M.M.; Kozub, R.L. )

    1991-02-01

    The probability of double {ital K}-shell vacancy production in the electron capture decay of {sup 139}Ce to the 166-keV level of {sup 139}La has been investigated. Triple coincidences between the 166-keV gamma ray, the La satellite {ital K}{alpha} x ray, and the La hypersatellite {ital K}{alpha} x ray were measured using two intrinsic Ge detectors. We looked for the sum of two of the three radiations in one detector in coincidence with the third radiation in the other detector. The probability of double {ital K}-shell vacancy production per {ital K}-shell electron capture ({ital P}{sub {ital K}{ital K}}) was found to be (2.0{plus minus}1.6){times}10{sup {minus}6}. From this and the known {ital P}{sub {ital K}{ital K}} for {sup 131}Cs we estimate a probability for zero {ital K}-shell vacancy production (shakedown) per {ital K}-shell electron capture of {approx lt}2.4{times}10{sup {minus}5} for {sup 139}Ce.

  12. Preservation of electronic properties of double-decker complexes on metallic supports.

    PubMed

    Cirera, B; Matarrubia, J; Kaposi, T; Giménez-Agulló, N; Paszkiewicz, M; Klappenberger, F; Otero, R; Gallego, J M; Ballester, P; Barth, J V; Miranda, R; Galán-Mascarós, J R; Auwärter, W; Ecija, D

    2017-03-22

    Single-molecule magnets based on lanthanide double-deckers are attracting significant attention due to their unrivaled single-ion anisotropy. To exploit their fascinating electronic and magnetic properties in devices for information storage or spin transport, studies on the preservation or variation of electronic and magnetic functionalities upon adsorption on surfaces are necessary. Herein, we introduced a comprehensive scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) surface science study, complemented by density functional theory (DFT) simulations, of a recently synthesized single-molecule magnet based on porphyrazine deckers, conveniently equipped with ethyl moieties to make them soluble and sublimable. We demonstrated that the double-decker species were intactly adsorbed on Au(111), Ag(111), and Cu(111) in a flat-on fashion and self-assembled in hexagonal close-packed layers. Systematic multi- and monolayer XPS was performed on the surface-confined species, confirming the preservation of the electronic properties of the ligands and the lanthanide center upon adsorption.

  13. A Model for Electron Nuclear Dynamics of a Monatomic Chain

    DTIC Science & Technology

    1994-05-16

    density in cell m) and that on atom n. Due to the choice of basis functions these parameters depend on the di tane In3 - fI -- R but not on the...p2Msaers and t&e choice of basis functions in this time-dependent *hWry. The res Iul ing equations of moioon include eACcvOnic-vibrational couplings...of basis functions in molecular or crystal orbitals, or of "nuclear" type, i.e. characterizn the state vectors for the nuclei. The method has the

  14. Generation and Analysis of Subpicosecond Double Electron Bunch at the Brookhaven Accelerator Test Facility

    SciTech Connect

    Babzien, M.; Kusche, K.; Yakimenko, V.; Zhou, F.; Kimura, Wayne D.; Cline, D.B.; Ding, X.P.; /UCLA

    2011-08-09

    Two compressed electron beam bunches from a single 60-MeV bunch have been generated in a reproducible manner during compression in the magnetic chicane - 'dog leg' arrangement at ATF. Measurements indicate they have comparable bunch lengths ({approx}100-200 fs) and are separated in energy by {approx}1.8 MeV with the higher-energy bunch preceding the lower-energy bunch by 0.5-1 ps. Some simulation results for analyzing the double-bunch formation process are also presented.

  15. Double-resolution electron holography with simple Fourier transform of fringe-shifted holograms.

    PubMed

    Volkov, V V; Han, M G; Zhu, Y

    2013-11-01

    We propose a fringe-shifting holographic method with an appropriate image wave recovery algorithm leading to exact solution of holographic equations. With this new method the complex object image wave recovered from holograms appears to have much less traditional artifacts caused by the autocorrelation band present practically in all Fourier transformed holograms. The new analytical solutions make possible a double-resolution electron holography free from autocorrelation band artifacts and thus push the limits for phase resolution. The new image wave recovery algorithm uses a popular Fourier solution of the side band-pass filter technique, while the fringe-shifting holographic method is simple to implement in practice.

  16. Two-electron double quantum dot coupled to coherent photon and phonon fields

    NASA Astrophysics Data System (ADS)

    Sato, Yuya; Chen, Jason C. H.; Hashisaka, Masayuki; Muraki, Koji; Fujisawa, Toshimasa

    2017-09-01

    Two-electron states of a double quantum dot (DQD) under irradiation of coherent boson (photon and phonon) fields are studied by measuring spin-flip tunneling current in the Pauli spin blockade regime. This measurement scheme allows us to investigate Rabi splitting and associated boson dressed states particularly in the deep dispersive regime where the detuning δ ≡ℏ ω -EAB between the boson energy ℏ ω and energy spacing EAB of the two-level system is significantly large (δ ˜ℏ ω ), where the permanent dipole moment in the DQD plays a significant role in the hybridization.

  17. The electronic properties of concentric double quantum ring and possibility designing XOR gate

    NASA Astrophysics Data System (ADS)

    AL-Badry, Lafy. F.

    2017-03-01

    In this paper I have investigated the Aharonov-Bohm oscillation in concentric double quantum ring. The outer ring attached to leads while the inner ring only tunnel-coupled to the outer ring. The effect of inner ring on electron transport properties through outer ring studied and found that the conductance spectrum consists of two types of oscillations. One is the normal Aharonov-Bohm oscillation, and other is a small oscillations superposed above AB oscillation. The AB oscillation utilized to designing nanoscale XOR gate by choosing the magnetic flux and tuning the gate voltages which realization XOR gate action.

  18. Double K-shell ionization in the electron capture decay of 55Fe

    NASA Astrophysics Data System (ADS)

    Campbell, J. L.; Maxwell, J. A.; Teesdale, W. J.

    1991-04-01

    The probability per K capture for double K-shell ionization in the electron capture decay of 55Fe was obtained by fitting a model spectrum to the x-ray spectrum recorded to very high statistics in a high-resolution Si(Li) detector. The result, PKK=(1.3+/-0.2)×10-4, confirms the trend wherein experimental data decrease smoothly with Z, and are intermediate between the theoretical predictions of Intemann and of Suzuki and Law. Corrections to some recently published PKK values reconcile them with this trend.

  19. Multi-bit dark state memory: Double quantum dot as an electronic quantum memory

    NASA Astrophysics Data System (ADS)

    Aharon, Eran; Pozner, Roni; Lifshitz, Efrat; Peskin, Uri

    2016-12-01

    Quantum dot clusters enable the creation of dark states which preserve electrons or holes in a coherent superposition of dot states for a long time. Various quantum logic devices can be envisioned to arise from the possibility of storing such trapped particles for future release on demand. In this work, we consider a double quantum dot memory device, which enables the preservation of a coherent state to be released as multiple classical bits. Our unique device architecture uses an external gating for storing (writing) the coherent state and for retrieving (reading) the classical bits, in addition to exploiting an internal gating effect for the preservation of the coherent state.

  20. Arbitrary amplitude dust ion acoustic solitons and double layers in the presence of nonthermal positrons and electrons

    NASA Astrophysics Data System (ADS)

    Banerjee, Gadadhar; Maitra, Sarit

    2016-12-01

    Existence of arbitrary amplitude solitons and double layers have been studied in collisionless unmagnetized multicomponent dusty plasmas with nonthermally distributed positrons and electrons by using Sagdeev's pseudopotential method. The linear dispersion relation is obtained for dust ion acoustic wave mode. The present model supports the coexistence of positive potential solitary waves and negative potential solitary waves and double layers. The criterion for the existence of solitary waves and double layers is derived in terms of Mach number limit. The effects of ion temperature and nonthermality of electrons and positrons are studied. Also the effects of positron and dust concentration on the wave propagation are observed.

  1. Ion acoustic solitary waves and double layers in a plasma with two temperature electrons featuring Tsallis distribution

    SciTech Connect

    Shalini, Saini, N. S.

    2014-10-15

    The propagation properties of large amplitude ion acoustic solitary waves (IASWs) are studied in a plasma containing cold fluid ions and multi-temperature electrons (cool and hot electrons) with nonextensive distribution. Employing Sagdeev pseudopotential method, an energy balance equation has been derived and from the expression for Sagdeev potential function, ion acoustic solitary waves and double layers are investigated numerically. The Mach number (lower and upper limits) for the existence of solitary structures is determined. Positive as well as negative polarity solitary structures are observed. Further, conditions for the existence of ion acoustic double layers (IADLs) are also determined numerically in the form of the critical values of q{sub c}, f and the Mach number (M). It is observed that the nonextensivity of electrons (via q{sub c,h}), concentration of electrons (via f) and temperature ratio of cold to hot electrons (via β) significantly influence the characteristics of ion acoustic solitary waves as well as double layers.

  2. Molecular cloning of cDNA for double-stranded RNA adenosine deaminase, a candidate enzyme for nuclear RNA editing.

    PubMed Central

    Kim, U; Wang, Y; Sanford, T; Zeng, Y; Nishikura, K

    1994-01-01

    We have cloned human cDNA encoding double-stranded RNA adenosine deaminase (DRADA). DRADA is a ubiquitous nuclear enzyme that converts multiple adenosines to inosines in double-helical RNA substrates without apparent sequence specificity. The A --> I conversion activity of the protein encoded by the cloned cDNA was confirmed by recombinant expression in insect cells. Use of the cloned DNA as a molecular probe documented sequence conservation across mammals and detected a single transcript of 7 kb in RNA of all human tissues analyzed. The deduced primary structure of human DRADA revealed a bipartite nuclear localization signal, three repeats of a double-stranded RNA binding motif, and the presence of sequences conserved in the catalytic center of other deaminases, including a cytidine deaminase involved in the RNA editing of apolipoprotein B. These structural properties are consistent with the enzymatic signature of DRADA, and strengthen the hypothesis that DRADA carries out the RNA editing of transcripts encoding glutamate-gated ion channels in brain. Images PMID:7972084

  3. Double electron-electron resonance measurements of diamond to determine T2 dependence on concentration of paramagnetic impurities

    NASA Astrophysics Data System (ADS)

    Stepanov, Viktor; Takahashi, Susumu

    A nitrogen-vacancy (NV) center in diamond is a promising candidate for investigation of fundamental sciences and applications to a nanoscale magnetic field sensing device because of unique properties of a NV center in diamond including capability to detect optically detected magnetic resonance (ODMR) signals from a single NV and initialize its spin state. Fundamental studies and applications of NV centers relay on coherent control of the NV centers that is limited by decoherence time (T2) and, as often observed, T2 is limited by paramagnetic impurity contents in diamond crystals. In this work, we will investigate T2 dependence on concentration of nitrogen impurities in type-Ib and type-IIa diamond crystals. For precise determination of the nitrogen concentration, we employ a home-built high-frequency electron spin resonance spectrometer which enables broadband double electron-electron resonance spectroscopy with high spectral resolution. This work is supported by the National Science Foundation (DMR-1508661) and the Searle scholars program.

  4. Phospholipid bilayer relaxation dynamics as revealed by the pulsed electron-electron double resonance of spin labels

    NASA Astrophysics Data System (ADS)

    Syryamina, V. N.; Dzuba, S. A.

    2012-10-01

    Electron paramagnetic resonance (EPR) spectroscopy in the form of pulsed electron-electron double resonance (ELDOR) was applied to 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) phospholipid bilayers containing lipids that were spin-labeled at different carbon positions along the lipid acyl chain. Pulsed ELDOR detects motionally induced spin flips of nitrogen nuclei in the nitroxide spin labels, which manifests itself as magnetization transfer (MT) in the nitroxide EPR spectrum. The MT effect was observed over a wide temperature range (100-225 K) on a microsecond time scale. In line with a previous study on molecular glasses [N. P. Isaev and S. A. Dzuba, J. Chem. Phys. 135, 094508 (2011), 10.1063/1.3633241], the motions that induce MT effect were suggested to have the same nature as those in dielectric secondary (β) Johari-Goldstein fast relaxation. The results were compared with literature dielectric relaxation data for POPC bilayers, revealing some common features. Molecular motions resulting in MT are faster for deeper spin labels in the membrane interior. The addition of cholesterol to the bilayer suppresses the lipid motions near the steroid nucleus and accelerates the lipid motions beyond the steroid nucleus, in the bilayer interior. This finding was attributed to the lipid acyl chains being more ordered near the steroid nucleus and less ordered in the bilayer interior. The motions are absent in dry lipids, indicating that the motions are determined by intermolecular interactions in the bilayer.

  5. Phospholipid bilayer relaxation dynamics as revealed by the pulsed electron-electron double resonance of spin labels.

    PubMed

    Syryamina, V N; Dzuba, S A

    2012-10-14

    Electron paramagnetic resonance (EPR) spectroscopy in the form of pulsed electron-electron double resonance (ELDOR) was applied to 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) phospholipid bilayers containing lipids that were spin-labeled at different carbon positions along the lipid acyl chain. Pulsed ELDOR detects motionally induced spin flips of nitrogen nuclei in the nitroxide spin labels, which manifests itself as magnetization transfer (MT) in the nitroxide EPR spectrum. The MT effect was observed over a wide temperature range (100-225 K) on a microsecond time scale. In line with a previous study on molecular glasses [N. P. Isaev and S. A. Dzuba, J. Chem. Phys. 135, 094508 (2011)], the motions that induce MT effect were suggested to have the same nature as those in dielectric secondary (β) Johari-Goldstein fast relaxation. The results were compared with literature dielectric relaxation data for POPC bilayers, revealing some common features. Molecular motions resulting in MT are faster for deeper spin labels in the membrane interior. The addition of cholesterol to the bilayer suppresses the lipid motions near the steroid nucleus and accelerates the lipid motions beyond the steroid nucleus, in the bilayer interior. This finding was attributed to the lipid acyl chains being more ordered near the steroid nucleus and less ordered in the bilayer interior. The motions are absent in dry lipids, indicating that the motions are determined by intermolecular interactions in the bilayer.

  6. Design of a lens table for a double toroidal electron spectrometer

    SciTech Connect

    Liu Xiaojng; Nicolas, Christophe; Miron, Catalin

    2013-03-15

    We report here on the method we developed to build a lens table for a four-element electrostatic transfer lens operated together with a double toroidal electron energy analyzer designed by one of us, and whose original design and further improvements are described in detail in Miron et al. [Rev. Sci. Instrum. 68, 3728 (1997)] and Le Guen et al. [Rev. Sci. Instrum. 73, 3885 (2002)]. Both computer simulations and laboratory instrument tuning were performed in order to build this lens table. The obtained result was tested for a broad range of electron kinetic energies and analyzer pass energies. Based on this new lens table, allowing to easily computer control the spectrometer working conditions, we could routinely achieve an electron energy resolution ranging between 0.6% and 0.8% of the analyzer pass energy, while the electron count rate was also significantly improved. The establishment of such a lens table is of high importance to relieve experimentalists from the tedious laboring of the lens optimization, which was previously necessary prior to any measurement. The described method can be adapted to any type of electron/ion energy analyzer, and will thus be interesting for all experimentalists who own, or plan to build or improve their charged particle energy analyzers.

  7. Evolution of electronic states in n-type copper oxide superconductor via electric double layer gating.

    PubMed

    Jin, Kui; Hu, Wei; Zhu, Beiyi; Kim, Dohun; Yuan, Jie; Sun, Yujie; Xiang, Tao; Fuhrer, Michael S; Takeuchi, Ichiro; Greene, Richard L

    2016-05-25

    The occurrence of electrons and holes in n-type copper oxides has been achieved by chemical doping, pressure, and/or deoxygenation. However, the observed electronic properties are blurred by the concomitant effects such as change of lattice structure, disorder, etc. Here, we report on successful tuning the electronic band structure of n-type Pr2-xCexCuO4 (x = 0.15) ultrathin films, via the electric double layer transistor technique. Abnormal transport properties, such as multiple sign reversals of Hall resistivity in normal and mixed states, have been revealed within an electrostatic field in range of -2 V to + 2 V, as well as varying the temperature and magnetic field. In the mixed state, the intrinsic anomalous Hall conductivity invokes the contribution of both electron and hole-bands as well as the energy dependent density of states near the Fermi level. The two-band model can also describe the normal state transport properties well, whereas the carrier concentrations of electrons and holes are always enhanced or depressed simultaneously in electric fields. This is in contrast to the scenario of Fermi surface reconstruction by antiferromagnetism, where an anti-correlation is commonly expected.

  8. Mitigation of energetic electrons in the magnetosphere by amplified whistler wave under double cyclotron resonances

    NASA Astrophysics Data System (ADS)

    Kuo, S. P.

    2008-10-01

    An optimal approach reducing the population of MeV electrons in the magnetosphere is presented. Under a double resonance condition, whistler wave is simultaneously in cyclotron resonance with keV and MeV electrons. The injected whistler waves is first amplified by the background keV electrons via loss-cone negative mass instability to become effective in precipitating MeV electrons via cyclotron resonance elevated chaotic scattering. The numerical results show that a small amplitude whistler wave can be amplified by more than 25 dB. The amplification factor reduces only about 10 dB with a 30 dB increase of the initial wave intensity. Use of an amplified whistler wave to scatter 1.5 MeV electrons from an initial pitch angle of 86.5°to a pitch angle <50° is demonstrated. The ratio of the required wave magnetic field to the background magnetic field is calculated to be about 8×10-4.

  9. Interaction-driven capacitance in graphene electron-hole double layer in strong magnetic fields

    NASA Astrophysics Data System (ADS)

    Roostaei, Bahman

    2015-12-01

    Fabrication of devices made by isolated graphene layers has opened up possibility of examining highly correlated states of electron systems in parts of their phase diagram that is impossible to access in their counterpart devices such as semiconductor heterostructures. An example of such states are graphene double monolayer electron-hole systems under strong magnetic fields where the separation between layers can be adjusted to be as small as one magnetic length with interlayer tunneling still suppressed. In those separations, it is known that correlations between electrons and holes are of crucial importance and must be included in determination of observable quantities. Here we report the results of our full numerical Hartree-Fock study of coherent and crystalline ground states of the interacting balanced electron-hole graphene systems in small and intermediate separations with each layer occupying up to four lowest lying Landau levels. We show that in the Hartree-Fock approximation the electrons and holes pair to form a homogeneous Bose-condensed (excitonic) state, while crystalline states of such exciton systems remain incoherent at intermediate layer separations. Our results of calculation of capacitance of such states as a function of interlayer separation and filling factor provides quantitative and qualitative signatures that can be examined in real experiments. We show that the capacitance of some crystallized states as well as uniform coherent states are significantly enhanced compared to geometrical values solely due to Coulomb interactions and quantum corrections.

  10. Evolution of electronic states in n-type copper oxide superconductor via electric double layer gating

    NASA Astrophysics Data System (ADS)

    Jin, Kui; Hu, Wei; Zhu, Beiyi; Kim, Dohun; Yuan, Jie; Sun, Yujie; Xiang, Tao; Fuhrer, Michael S.; Takeuchi, Ichiro; Greene, Richard. L.

    2016-05-01

    The occurrence of electrons and holes in n-type copper oxides has been achieved by chemical doping, pressure, and/or deoxygenation. However, the observed electronic properties are blurred by the concomitant effects such as change of lattice structure, disorder, etc. Here, we report on successful tuning the electronic band structure of n-type Pr2‑xCexCuO4 (x = 0.15) ultrathin films, via the electric double layer transistor technique. Abnormal transport properties, such as multiple sign reversals of Hall resistivity in normal and mixed states, have been revealed within an electrostatic field in range of ‑2 V to + 2 V, as well as varying the temperature and magnetic field. In the mixed state, the intrinsic anomalous Hall conductivity invokes the contribution of both electron and hole-bands as well as the energy dependent density of states near the Fermi level. The two-band model can also describe the normal state transport properties well, whereas the carrier concentrations of electrons and holes are always enhanced or depressed simultaneously in electric fields. This is in contrast to the scenario of Fermi surface reconstruction by antiferromagnetism, where an anti-correlation is commonly expected.

  11. Evolution of electronic states in n-type copper oxide superconductor via electric double layer gating

    PubMed Central

    Jin, Kui; Hu, Wei; Zhu, Beiyi; Kim, Dohun; Yuan, Jie; Sun, Yujie; Xiang, Tao; Fuhrer, Michael S.; Takeuchi, Ichiro; Greene, Richard. L.

    2016-01-01

    The occurrence of electrons and holes in n-type copper oxides has been achieved by chemical doping, pressure, and/or deoxygenation. However, the observed electronic properties are blurred by the concomitant effects such as change of lattice structure, disorder, etc. Here, we report on successful tuning the electronic band structure of n-type Pr2−xCexCuO4 (x = 0.15) ultrathin films, via the electric double layer transistor technique. Abnormal transport properties, such as multiple sign reversals of Hall resistivity in normal and mixed states, have been revealed within an electrostatic field in range of −2 V to + 2 V, as well as varying the temperature and magnetic field. In the mixed state, the intrinsic anomalous Hall conductivity invokes the contribution of both electron and hole-bands as well as the energy dependent density of states near the Fermi level. The two-band model can also describe the normal state transport properties well, whereas the carrier concentrations of electrons and holes are always enhanced or depressed simultaneously in electric fields. This is in contrast to the scenario of Fermi surface reconstruction by antiferromagnetism, where an anti-correlation is commonly expected. PMID:27221198

  12. Double-electron capture by highly-ionized atoms isolated at very low energy

    NASA Astrophysics Data System (ADS)

    Fogwell Hoogerheide, Shannon; Dreiling, Joan M.; Sahiner, Arda; Tan, Joseph N.

    2016-05-01

    Charge exchange with background gases, also known as electron capture processes, is important in the study of comets, controlled fusion energy, anti-matter atoms, and proposed one-electron ions in Rydberg states. However, there are few experiments in the very low energy regime that could be useful for further theoretical development. At NIST, highly-charged ions extracted from an electron-beam ion trap can be isolated with energy < 10 eV in a compact Penning trap. By controlling the background gas pressure and composition, the charge exchange rates can be studied. Fully stripped neon or other ions are held in the trap for varying lengths of time and allowed to interact with different background gases at multiple pressures. The ions are then pulsed to a time-of-flight detector to count the population of each charge state. Analysis using a system of rate equations yields information about the ion cloud expansion and single-electron capture rates. A substantial amount of double-electron capture is also observed. We present the relative rates and discuss the error budget. SFH and JMD were funded by National Research Council Research Associateship Awards during some of this work.

  13. Understanding the nuclear initial state with an electron ion collider

    NASA Astrophysics Data System (ADS)

    Toll, Tobias

    2013-09-01

    In these proceedings I describe how a future electron-ion collider will allow us to directly measure the initial spatial distribution of gluons in heavy ions, as well as its variance ("lumpiness") in exclusive diffraction. I show the feasibility of such a measurement by means of simulated data from the novel event generator Sartre.

  14. The effects of nuclear power generators upon electronic instrumentation

    NASA Technical Reports Server (NTRS)

    Miller, C. G.; Truscello, V. C.

    1970-01-01

    Radiation sensitivity of electronic instruments susceptible to neutron and gamma radiation is evaluated by means of a radioisotope thermoelectric generator /RTG/. The gamma field of the RTG affects instrument operation and requires shielding, the neutron field does not affect operation via secondary capture-gamma production.

  15. Nuclear interlevel transfer driven by collective outer shell electron oscillations

    SciTech Connect

    Rinker, G.A.; Solem, J.G.; Biedenharn, L.C.

    1986-10-20

    The general problem of dynamic electron-nucleus coupling is discussed, and the possibility of using this mechanism to initiate gamma-ray lasing. Single-particle and collective mechanisms are considered. The problems associated with accurate calculation of these processes are discussed, and some numerical results are given. Work in process in described. 10 refs., 7 figs.

  16. Electron transfer through a self-assembled monolayer of a double-helix peptide with linking the terminals by ferrocene.

    PubMed

    Okamoto, Shinpei; Morita, Tomoyuki; Kimura, Shunsaku

    2009-03-03

    A unique molecular structure, a double-helix peptide, was self-assembled on gold, and the electron transfer through the monolayer was studied. The double-helix peptide consists of two 9mer 3(10)-helical peptide chains having a disulfide group at each N terminal and being linked by a ferrocene dicarboxylic acid between the C terminals. Each helical peptide chain has three naphthyl groups in a linear arrangement along the helix. The monolayer properties and the electron transfer from the ferrocene unit to gold were studied with reference peptides with a similar double helix but without naphthyl groups, a single helix with a dicarboxylic ferrocene unit, and a single helix with a monocarboxylic ferrocene unit. It was demonstrated that the naphthyl groups on the side chains had no effect on electron transfer, and the electron-transfer rate in the double-helix monolayer was not promoted, despite the two electron pathways in the molecule. We propose that in the double-helix monolayer, molecular motions are suppressed, possibly by its rigid structure tethered by the two linkers on gold to cancel out acceleration effects of the 2-fold electron pathways and the ferrocene substitution number. The factors that affect the electron-transfer reaction across the helical peptide SAMs are discussed in depth.

  17. Electron nuclear dynamics of proton collisions with methane at 30 eV

    NASA Astrophysics Data System (ADS)

    Jacquemin, D.; Morales, J. A.; Deumens, E.; Öhrn, Y.

    1997-10-01

    The reactive collisions of protons with methane molecules at 30 eV in the laboratory frame are studied with the electron nuclear dynamics (END). The results from this theoretical approach, which does not invoke the Born-Oppenheimer approximation and does not impose any constraints on the nuclear dynamics, are compared to the results from time-of-flight measurements. Total differential cross sections and integral cross sections as well as fragmentation ratios and energy loss spectra are discussed.

  18. Additive effects of electronic and nuclear energy loss in irradiation-induced amorphization of zircon

    DOE PAGES

    Zarkadoula, Eva; Toulemonde, Marcel; Weber, William J.

    2015-12-29

    We used a combination of ion cascades and the unified thermal spike model to study the electronic effects from 800 keV Kr and Xe ion irradiation in zircon. We compared the damage production for four cases: (a) due to ion cascades alone, (b) due to ion cascades with the electronic energy loss activated as a friction term, (c) due to the thermal spike from the combined electronic and nuclear energy losses, and (d) due to ion cascades with electronic stopping and the electron-phonon interactions superimposed. As a result, we found that taking the electronic energy loss out as a frictionmore » term results in reduced damage, while the electronic electron-phonon interactions have additive impact on the final damage created per ion.« less

  19. Additive effects of electronic and nuclear energy loss in irradiation-induced amorphization of zircon

    SciTech Connect

    Zarkadoula, Eva; Toulemonde, Marcel; Weber, William J.

    2015-12-29

    We used a combination of ion cascades and the unified thermal spike model to study the electronic effects from 800 keV Kr and Xe ion irradiation in zircon. We compared the damage production for four cases: (a) due to ion cascades alone, (b) due to ion cascades with the electronic energy loss activated as a friction term, (c) due to the thermal spike from the combined electronic and nuclear energy losses, and (d) due to ion cascades with electronic stopping and the electron-phonon interactions superimposed. As a result, we found that taking the electronic energy loss out as a friction term results in reduced damage, while the electronic electron-phonon interactions have additive impact on the final damage created per ion.

  20. Additive effects of electronic and nuclear energy losses in irradiation-induced amorphization of zircon

    SciTech Connect

    Zarkadoula, Eva; Toulemonde, Marcel; Weber, William J.

    2015-12-28

    We used a combination of ion cascades and the unified thermal spike model to study the electronic effects from 800 keV Kr and Xe ion irradiation in zircon. We compared the damage production for four cases: (a) due to ion cascades alone, (b) due to ion cascades with the electronic energy loss activated as a friction term, (c) due to the thermal spike from the combined electronic and nuclear energy losses, and (d) due to ion cascades with electronic stopping and the electron-phonon interactions superimposed. We found that taking the electronic energy loss out as a friction term results in reduced damage, while the electronic electron-phonon interactions have additive impact on the final damage created per ion.

  1. Entanglement of two-electron spin states in a double quantum dot

    NASA Astrophysics Data System (ADS)

    Bagrov, V. G.; Gitman, D. M.; Levin, A. D.; Meireles, M. S.

    Recently, an implementation of a universal set of one- and two-quantum-bit gates for quantum computation using spin states of coupled single-electron quantum dots was proposed. It was demonstrated that it is possible to execute a coherent control of a quantum system based on two-electron spin states in a double quantum dot, allowing state preparation, coherent manipulation, and projective readout. This possibility is based on rapid electrical control of the spin exchange interaction. These results motivated us to develop a formal theoretical study of the corresponding model of two coupled spins placed in a magnetic field and subjected to a time-dependent mutual Heisenberg interaction. Using possible exact solutions of the corresponding quantum problem, we study entangling of different separable initial states in this model. It is demonstrated that the entanglement due to a time-dependent Heisenberg interaction is dominating in comparison with the entanglement due to the action of an external magnetic field.

  2. Controlling Two-Electron Threshold Dynamics in Double Photoionization of Lithium by Initial-State Preparation

    NASA Astrophysics Data System (ADS)

    Zhu, G.; Schuricke, M.; Steinmann, J.; Albrecht, J.; Ullrich, J.; Ben-Itzhak, I.; Zouros, T. J. M.; Colgan, J.; Pindzola, M. S.; Dorn, A.

    2009-09-01

    Double photoionization (DPI) and ionization-excitation (IE) of Li(2s) and Li(2p), state-prepared and aligned in a magneto-optical trap, were explored in a reaction microscope at the free-electron laser in Hamburg (FLASH). From 6 to 12 eV above threshold (ℏω=85, 91 eV), total as well as differential DPI cross sections were observed to critically depend on the initial state and, in particular, on the alignment of the 2p orbital with respect to the VUV-light polarization, whereas no effect is seen for IE. The alignment sensitivity is traced back to dynamical electron correlation at threshold.

  3. Controlling Two-Electron Threshold Dynamics in Double Photoionization of Lithium by Initial-State Preparation

    SciTech Connect

    Zhu, G.; Schuricke, M.; Steinmann, J.; Albrecht, J.; Dorn, A.; Ullrich, J.; Ben-Itzhak, I.; Zouros, T. J. M.; Colgan, J.; Pindzola, M. S.

    2009-09-04

    Double photoionization (DPI) and ionization-excitation (IE) of Li(2s) and Li(2p), state-prepared and aligned in a magneto-optical trap, were explored in a reaction microscope at the free-electron laser in Hamburg (FLASH). From 6 to 12 eV above threshold ((Planck constant/2pi)omega=85, 91 eV), total as well as differential DPI cross sections were observed to critically depend on the initial state and, in particular, on the alignment of the 2p orbital with respect to the VUV-light polarization, whereas no effect is seen for IE. The alignment sensitivity is traced back to dynamical electron correlation at threshold.

  4. Magnetic, electronic, and optical properties of double perovskite Bi2FeMnO6

    NASA Astrophysics Data System (ADS)

    Ahmed, Towfiq; Chen, Aiping; Yarotski, Dmitry A.; Trugman, Stuart A.; Jia, Quanxi; Zhu, Jian-Xin

    2017-03-01

    Double perovskite Bi2FeMnO6 is a potential candidate for the single-phase multiferroic system. In this work, we study the magnetic, electronic, and optical properties in BFMO by performing the density functional theory calculations and experimental measurements of magnetic moment. We also demonstrate the strain dependence of magnetization. More importantly, our calculations of electronic and optical properties reveal that the onsite local correlation on Mn and Fe sites is critical to the gap opening in BFMO, which is a prerequisite condition for the ferroelectric ordering. Finally, we calculate the x-ray magnetic circular dichroism spectra of Fe and Mn ions (L2 and L3 edges) in BFMO.

  5. Electron spin resonance and spin-valley physics in a silicon double quantum dot.

    PubMed

    Hao, Xiaojie; Ruskov, Rusko; Xiao, Ming; Tahan, Charles; Jiang, HongWen

    2014-05-14

    Silicon quantum dots are a leading approach for solid-state quantum bits. However, developing this technology is complicated by the multi-valley nature of silicon. Here we observe transport of individual electrons in a silicon CMOS-based double quantum dot under electron spin resonance. An anticrossing of the driven dot energy levels is observed when the Zeeman and valley splittings coincide. A detected anticrossing splitting of 60 MHz is interpreted as a direct measure of spin and valley mixing, facilitated by spin-orbit interaction in the presence of non-ideal interfaces. A lower bound of spin dephasing time of 63 ns is extracted. We also describe a possible experimental evidence of an unconventional spin-valley blockade, despite the assumption of non-ideal interfaces. This understanding of silicon spin-valley physics should enable better control and read-out techniques for the spin qubits in an all CMOS silicon approach.

  6. Operation of the CAPRICE electron cyclotron resonance ion source applying frequency tuning and double frequency heating.

    PubMed

    Maimone, F; Tinschert, K; Celona, L; Lang, R; Mäder, J; Rossbach, J; Spädtke, P

    2012-02-01

    The properties of the electromagnetic waves heating the electrons of the ECR ion sources (ECRIS) plasma affect the features of the extracted ion beams such as the emittance, the shape, and the current, in particular for higher charge states. The electron heating methods such as the frequency tuning effect and the double frequency heating are widely used for enhancing the performances of ECRIS or even for the routine operation during the beam production. In order to better investigate these effects the CAPRICE ECRIS has been operated using these techniques. The ion beam properties for highly charged ions have been measured with beam diagnostic tools. The reason of the observed variations of this performance can be related to the different electromagnetic field patterns, which are changing inside the plasma chamber when the frequency is varying.

  7. Electron paramagnetic resonance study of the nuclear spin dynamics in an AlAs quantum well

    NASA Astrophysics Data System (ADS)

    Shchepetilnikov, A. V.; Frolov, D. D.; Nefyodov, Yu. A.; Kukushkin, I. V.; Tiemann, L.; Reichl, C.; Dietsche, W.; Wegscheider, W.

    2016-12-01

    The nuclear spin dynamics in an asymmetrically doped 16-nm AlAs quantum well grown along the [001] direction has been studied experimentally using the time decay of the Overhauser shift of paramagnetic resonance of conduction electrons. The nonzero spin polarization of nuclei causing the initial observed Overhauser shift is due the relaxation of the nonequilibrium spin polarization of electrons into the nuclear subsystem near electron paramagnetic resonance owing to the hyperfine interaction. The measured relaxation time of nuclear spins near the unity filling factor is (530 ± 30) min at the temperature T = 0.5 K. This value exceeds the characteristic spin relaxation times of nuclei in GaAs/AlGaAs heterostructures by more than an order of magnitude. This fact indicates the decrease in the strength of the hyperfine interaction in the AlAs quantum well in comparison with GaAs/AlGaAs heterostructures.

  8. A path toward single electron devices: Chemical functionalization of Si(111) to achieve single electron transport through double tunnel junctions

    NASA Astrophysics Data System (ADS)

    Campbell, Philip Michael

    Functionalization of silicon through the UV attachment of organic monolayers represents a potential method for creating molecular electronics. Prior research has demonstrated that longchain alkenes create highly ordered, robust monolayers on Si(111). However, specific applications, such as double tunnel junctions and quantum dot solar cells, require shorter chain molecules than have been previously studied. Through the use of FTIR and XPS data, UV attachment of several short-chain organics is demonstrated to create dense monolayers. The results reveal that molecules with a seven carbon base chain are extremely stable and can undergo additional functionalization to create an amine terminated surface without compromising the quality. STS curves on gold nanoparticles deposited on these monolayers show evidence of Coulomb staircase behavior. Conversely, chains shorter than seven carbons degrade more quickly when stored in a dry nitrogen environment and cannot withstand the processing steps necessary to be used for this application.

  9. Bohmian mechanics in the exact factorization of electron-nuclear wave functions

    NASA Astrophysics Data System (ADS)

    Suzuki, Yasumitsu; Watanabe, Kazuyuki

    2016-09-01

    The exact factorization of an electron-nuclear wave function [A. Abedi, N. T. Maitra, and E. K. U. Gross, Phys. Rev. Lett. 105, 123002 (2010), 10.1103/PhysRevLett.105.123002] allows us to define the rigorous nuclear time-dependent Schrödinger equation (TDSE) with a time-dependent potential-energy surface (TDPES) that fully accounts for the coupling to the electronic motion and drives the nuclear wave-packet dynamics. Here, we study whether the propagation of multiple classical trajectories can reproduce the quantum nuclear motion in strong-field processes when their motions are governed by the quantum Hamilton-Jacobi equation derived by applying Bohmian mechanics to this exact nuclear TDSE. We demonstrate that multiple classical trajectories propagated by the force from the gradient of the exact TDPES plus the Bohmian quantum potential can reproduce the strong-field dissociation dynamics of a one-dimensional model of the H2 + molecule. Our results show that the force from the Bohmian quantum potential plays a non-negligible role in yielding quantum nuclear dynamics in the strong-field process studied here, where ionization and/or splitting of nuclear probability density occurs.

  10. Experiments on the Nuclear Interactions of Pions and Electrons

    SciTech Connect

    Ralph C. Minehart

    2005-04-15

    This is the final technical report. Yearly Progress Reports were submitted throughout the duration of the project. Along with our publications, these reports provide a detailed record of our accomplishments. This report largely consists of a summary of the technical activities carried out during last 2-1/2 years of the project, along with a list of papers published in the period from 2002-2005. Our work during this period involved the following: 1. Electro-production of excited states of the nucleon through the analysis of exclusive single pion production reactions induced by polarized electrons incident on both polarized and unpolarized nucleon targets. (JLab) 2. Measurement of proton and deuteron spin structure functions in and above the nucleon resonance region at low and moderate $Q^2$, using inclusive electron-proton and electron deuteron scattering (JLAB). 3. Contributions to the PRIMEX experiment (JLab). 4. A precise measurement of the branching ratio for pion beta decay was carried out along with other members of the PIBETA collaboration (PSI). The first three, labeled JLab, were experiments made with the CLAS detector at the Thomas Jefferson Laboratory in Newport News, VA. The PIBETA experiment was carried out using a low energy pion beam at the Paul Scherrer Institute in Villigen, Switzerland.

  11. Probing and comparing electron doping and miss-site effects in Re-based double perovskites.

    PubMed

    Blasco, J; Sesé, J; Rodríguez-Velamazán, J A; Ritter, C; Herrero-Martín, J

    2009-05-27

    We have studied the Sr(2-x)La(x)Fe(1+x/2)Re(1-x/2)O(6) series in order to check how the increase in the number of Fe-O-Fe superexchange interactions affects the magnetic properties of this family of double perovskites. In these compounds the addition of La(3+) can be compensated by an increase of the Fe(3+) ratio leading to a non-electron-doped system. The unit cell of these samples expands on replacing Sr by La and the cationic ordering disappears for x>1 samples. Spontaneous magnetization at 5 K is observed in a wide range of concentrations but the magnetization at 5 T decreases as the La content increases. This result may be explained in terms of a ferrimagnetic ground state of the double perovskite. The magnetic ordering temperature increases with increasing the La and Fe content in agreement with an increase in the number of Fe-O-Fe interactions. The comparison to the electron-doped samples suggests that this effect is not enough to explain on its own the stronger T(C)-rise in Sr(2-x)La(x)FeReO(6) compounds.

  12. Separation of double-wall carbon nanotubes by electronic type and diameter.

    PubMed

    Streit, J K; Lam, S; Piao, Y; Hight Walker, A R; Fagan, J A; Zheng, M

    2017-02-16

    We introduce a new procedure for the efficient isolation and subsequent separation of double-wall carbon nanotubes (DWCNTs). A simplified, rate zonal ultracentrifugation (RZU) process is first applied to obtain samples of highly-enriched DWCNTs from a raw carbon nanotube material that has both single- and double-wall carbon nanotubes. Using this purified DWCNT suspension, we demonstrate for the first time that DWCNTs can be further processed using aqueous two-phase extraction (ATPE) for sequential separation by electronic structure and diameter. Additionally, we introduce analytical ultracentrifugation (AUC) as a new method for DWCNT characterization to assess DWCNT purity in separated samples. Results from AUC analysis are utilized to compare two DWCNT separation schemes. We find that RZU processing followed by sequential bandgap and diameter sorting via ATPE provides samples of highest DWCNT enrichment, whereas single-step redox sorting of the same raw material through ATPE yields SWCNT/DWCNT mixtures of similar diameter and electronic character. The presented methods offer significant advancement in DWCNT processing and separation while also providing a promising alternative for DWCNT sample analysis.

  13. Ion-acoustic solitons, double layers and rogue waves in plasma having superthermal electrons

    NASA Astrophysics Data System (ADS)

    Singh Saini, Nareshpal

    2016-07-01

    Most of the space and astrophysical plasmas contain different type of charged particles with non-Maxwellian velocity distributions (e.g., nonthermal, superthermal, Tsallis ). These distributions are commonly found in the auroral region of the Earth's magnetosphere, planetary magnetosphere, solar and stellar coronas, solar wind, etc. The observations from various satellite missions have confirmed the presence of superthermal particles in space and astrophysical environments. Over the last many years, there have been a much interest in studying the different kind of properties of the electrostatic nonlinear excitations (solitons, double layers, rogue waves etc.) in a multi-component plasmas in the presence of superthermal particles. It has been analyzed that superthermal distributions are more appropriate than Maxwellian distribution for the modeling of space data. It is interesting to study the dynamics of various kinds of solitary waves, Double layers, Shocks etc. in varieties of plasma systems containing different kind of species obeying Lorentzian (kappa-type)/Tsallis distribution. In this talk, I have focused on the study of large amplitude IA solitary structures (bipolar solitary structures, double layers etc.), modulational instability and rogue waves in multicomponent plasmas. The Sagdeev potential method has been employed to setup an energy balance equation, from which we have studied the characteristics of large amplitude solitary waves under the influence of superthermality of charged particles and other plasma parameters. The critical Mach number has been determined, above which solitary structures are observed and its variation with superthermality of electrons and other parameters has also been discussed. Double layers have also been discussed. Multiple scale reductive perturbation method has been employed to derive NLS equation. From the different kind of solutions of this equation, amplitude modulation of envelope solitons and rogue waves have been

  14. Role of electron-nuclear coupled dynamics on charge migration induced by attosecond pulses in glycine

    NASA Astrophysics Data System (ADS)

    Lara-Astiaso, Manuel; Palacios, Alicia; Decleva, Piero; Tavernelli, Ivano; Martín, Fernando

    2017-09-01

    We present a theoretical study of charge dynamics initiated by an attosecond XUV pulse in the glycine molecule, which consists in delocalized charge fluctuations all over the molecular skeleton. For this, we have explicitly used the actual electron wave packet created by such a broadband pulse. We show that, for the chosen pulse, charge dynamics in glycine is barely affected by nuclear motion or non adiabatic effects during the first 8 fs, and that the initial electronic coherences do not dissipate during the first 20 fs. In contrast, small variations in the initial nuclear positions, compatible with the geometries expected in the Franck-Condon region, lead to noticeable changes in this dynamics.

  15. Discrimination of nuclear and electronic recoil events using plasma effect in germanium detectors

    NASA Astrophysics Data System (ADS)

    Wei, W.-Z.; Liu, J.; Mei, D.-M.

    2016-07-01

    We report a new method of using the plasma time difference, which results from the plasma effect, between the nuclear and electronic recoil events in high-purity germanium detectors to distinguish these two types of events in the search for rare physics processes. The physics mechanism of the plasma effect is discussed in detail. A numerical model is developed to calculate the plasma time for nuclear and electronic recoils at various energies in germanium detectors. It can be shown that under certain conditions the plasma time difference is large enough to be observable. The experimental aspects in realizing such a discrimination in germanium detectors is discussed.

  16. Electron-Nuclear Dynamics of atomic and molecular collisions: Charge exchange and energy loss

    NASA Astrophysics Data System (ADS)

    Cabrera-Trujillo, Remigio; Sabin, John R.; Ohrn, Yngve; Deumens, Erik

    2004-05-01

    Processes like electron exchange (capture and loss), bond breaking, and chemical reactions are difficult to visualize and treat in a time-independent approach. In this work, we present the Electron-Nuclear Dynamics (END) method for the study of time-dependent scattering processes. The END is a general approach for treating time-dependent problems which includes the dynamics of electrons and nuclei simultaneously by considering the full electron-nuclear coupling in the system and thus eliminates the necessity of constructing potential-energy surfaces. The theory approximates the time dependent Schrödinger equation starting from the time dependent variational principle (TDVP) by deriving a Hamiltonian dynamical system for time dependent nuclear and electronic wave function parameters. The wave function is described in a coherent state manifold, which leads to a system of Hamilton's equations of motion. The resulting system of coupled, first order, ordinary differential equations approximates the Schrödinger equation. A detailed analysis of the END equations is given for the case of a single-determinantal state for the electrons and a classical treatment of the nuclei. Emphasis is put on electron exchange, differential cross section and energy loss (stopping cross section) of collision of ions, atoms and molecules involving H, He, C, N, O, and Ne atoms. We compare our results to available experimental data.

  17. Correlated electron-nuclear kinetic energy distribution following strong-field ionization of H2^+

    NASA Astrophysics Data System (ADS)

    Madsen, C. B.; Anis, F.; Madsen, L. B.; Esry, B. D.

    2010-03-01

    Being the simplest molecule, understanding the behavior of H2^+ in a strong laser field helps to understand more complex molecules. Theoretically, however, it is challenging to account for both electronic and nuclear motion in the ionization of even this simple molecule. Accordingly, calculating correlated electron-nuclear physical observables --- such as energy or momentum distributions --- has rarely been accomplished. Such calculations are needed to interpret recent measurements of coincidence momentum distributions of electrons and ions following the ionization of molecules by short intense laser pulses. We study how the energy absorbed from an intense laser pulse (400--800 nm, ˜10^14 W/cm^2, >=10 cycles) is shared among the nuclei and the electron of H2^+ by calculating the 2D electron-nuclei momentum distribution for a 1D model with soft-core Coulomb interactions. These 2D momentum plots reveal multiphoton structure with the energy shared between the nuclei and electron. This structure survives integrating out the nuclear energy, but not integrating out the electronic energy. ^*Supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. DoE.

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

    PubMed

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

    2014-01-14

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

  19. Automatic track following system to study double strangeness nuclei in nuclear emulsion exposed to the observable limit

    NASA Astrophysics Data System (ADS)

    Myint Kyaw Soe; Goto, Ryosuke; Mishina, Akihiro; Nakanisi, Yoshiaki; Nakashima, Daisuke; Yoshida, Junya; Nakazawa, Kazuma

    2017-03-01

    An automatic track following system has been successfully developed to follow tracks in nuclear emulsion sheets exposed with beam up to the limit to be observed for the first time. The track followed rate of the system is 99.5% with the assistance of the new techniques. The working speed for a track is less than 1 min through one thick emulsion sheet, whereas it is 15 times faster than that of semiautomatic system with human. The system working for 24 h is applied for the E07 experiment at J-PARC and makes it possible to detect 102 nuclei with double strangeness (S=-2 nuclei) within one year. Regarding analyses to identify nuclear species of S=-2 nuclei, the system shows quite decent job for significant steps such as following tracks emitted to spherical directions from S=-2 nuclei, measurement of lengths of followed tracks, and so on.

  20. Nonlinear propagation of small-amplitude modified electron acoustic solitary waves and double layer in semirelativistic plasmas

    SciTech Connect

    Sah, O.P.; Goswami, K.S. )

    1994-10-01

    Considering an unmagnetized plasma consisting of relativistic drifting electrons and nondrifting thermal ions and by using reductive perturbation method, a usual Korteweg--de Vries (KdV) equation and a generalized form of KdV equation are derived. It is found that while the former governs the dynamics of a small-amplitude rarefactive modified electron acoustic (MEA) soliton, the latter governs the dynamics of a weak compressive modified electron acoustic double layer. The influences of relativistic effect on the propagation of such a soliton and double layer are examined. The relevance of this investigation to space plasma is pointed out.

  1. Final report on LDRD Project: The double electron layer tunneling transistor (DELTT)

    SciTech Connect

    Simmons, J.A.; Moon, J.S.; Blount, M.A.

    1998-06-01

    This report describes the research accomplishments achieved under the LDRD Project ``Double Electron Layer Tunneling Transistor.`` The main goal of this project was to investigate whether the recently discovered phenomenon of 2D-2D tunneling in GaAs/AlGaAs double quantum wells (DQWs), investigated in a previous LDRD, could be harnessed and implemented as the operating principle for a new type of tunneling device the authors proposed, the double electron layer tunneling transistor (DELTT). In parallel with this main thrust of the project, they also continued a modest basic research effort on DQW physics issues, with significant theoretical support. The project was a considerable success, with the main goal of demonstrating a working prototype of the DELTT having been achieved. Additional DELTT advances included demonstrating good electrical characteristics at 77 K, demonstrating both NMOS and CMOS-like bi-stable memories at 77 K using the DELTT, demonstrating digital logic gates at 77 K, and demonstrating voltage-controlled oscillators at 77 K. In order to successfully fabricate the DELTT, the authors had to develop a novel flip-chip processing scheme, the epoxy-bond-and-stop-etch (EBASE) technique. This technique was latter improved so as to be amenable to electron-beam lithography, allowing the fabrication of DELTTs with sub-micron features, which are expected to be extremely high speed. In the basic physics area they also made several advances, including a measurement of the effective mass of electrons in the hour-glass orbit of a DQW subject to in-plane magnetic fields, and both measurements and theoretical calculations of the full Landau level spectra of DQWs in both perpendicular and in-plane magnetic fields. This last result included the unambiguous demonstration of magnetic breakdown of the Fermi surface. Finally, they also investigated the concept of a far-infrared photodetector based on photon assisted tunneling in a DQW. Absorption calculations showed a

  2. Equatorial electron loss by double resonance with oblique and parallel intense chorus waves

    NASA Astrophysics Data System (ADS)

    Mourenas, D.; Artemyev, A. V.; Agapitov, O. V.; Mozer, F. S.; Krasnoselskikh, V. V.

    2016-05-01

    Puzzling satellite observations of butterfly pitch angle distributions and rapid dropouts of 30-150 keV electrons are widespread in the Earth's radiation belts. Several mechanisms have been proposed to explain these observations, such as enhanced outward radial diffusion combined with magnetopause shadowing or scattering by intense magnetosonic waves, but their effectiveness is mainly limited to storm times. Moreover, the scattering of 30-150 keV electrons via cyclotron resonance with intense parallel chorus waves should be limited to particles with equatorial pitch angle smaller than 70°-75°, leaving unaffected a large portion of the population. In this paper, we investigate the possible effects of oblique whistler mode waves, noting, in particular, that Landau resonance with very oblique waves can occur up to ˜89°. We demonstrate that such very oblique chorus waves with realistic amplitudes can very efficiently nonlinearly transport nearly equatorially mirroring electrons toward smaller pitch angles where nonlinear scattering (phase bunching) via cyclotron resonance with quasi-parallel waves can take over and quickly send them to much lower pitch angles <40°. The proposed double resonance mechanism could therefore explain the formation of butterfly pitch angle distributions as well as contribute to some fast dropouts of 30-150 keV electrons occurring during moderate geomagnetic disturbances at L = 4-6. Since 30-150 keV electrons represent a seed population for a further acceleration to relativistic energies by intense parallel chorus waves during storms or substorms, the proposed mechanism may have important consequences on the dynamics of 100 keV to MeV electron fluxes in the radiation belts.

  3. Conformational changes of the histidine ATP-binding cassette transporter studied by double electron-electron resonance spectroscopy.

    PubMed

    Sippach, Michael; Weidlich, Daniela; Klose, Daniel; Abé, Christoph; Klare, Johann; Schneider, Erwin; Steinhoff, Heinz-Jürgen

    2014-07-01

    The conformational dynamics of the histidine ABC transporter HisQMP2 from Salmonella enterica serovar Typhimurium, reconstituted into liposomes, is studied by site-directed spin labeling and double electron-electron resonance spectroscopy in the absence of nucleotides, in the ATP-bound, and in the post-hydrolysis state. The results show that the inter-dimer distances as measured between the Q-loops of HisP2 in the intact transporter resemble those determined for the maltose transporter in all three states of the hydrolysis cycle. Only in the presence of liganded HisJ the closed conformation of the nucleotide binding sites is achieved revealing the transmembrane communication of the presence of substrate. Two conformational states can be distinguished for the periplasmic moiety of HisQMP2 as detected by differences in distributions of interspin distances between positions 86 and 96 or 104 and 197. The observed conformational changes are correlated to proposed open, semi-open and closed conformations of the nucleotide binding domains HisP2. Our results are in line with a rearrangement of transmembrane helices 4 and 4' of HisQM during the closed to the semi-open transition of HisP2 driven by the reorientation of the coupled helices 3a and 3b to occur upon hydrolysis. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Dependence of Distance Distributions Derived from Double Electron-Electron Resonance Pulsed EPR on Pulse Sequence Time**

    PubMed Central

    Louis, John M.

    2015-01-01

    Pulsed double electron-electron resonance (DEER) provides pairwise P(r) distance distributions in doubly spin-labeled proteins. We report that in protonated proteins P(r) is dependent on the length of the second echo period T owing to local environmental effects on spin-label phase memory relaxation time Tm. For the protein ABD, this effect results in a 1.4 Å increase in the P(r) maximum from T = 6 to 20 μs. Protein A has a bimodal P(r) distribution and the relative height of the shorter distance peak at T = 10 μs, the shortest value required to obtain a reliable P(r), is reduced by 40% relative to that obtained by extrapolation to T = 0. Our results indicate that data at a series of T values are essential for quantitative interpretation of DEER to determine the extent of the T dependence and to extrapolate the results to T= 0. Complete deuteration (99%) of the protein is accompanied by a significant increase in Tm and effectively abolishes the P(r) dependence on T. PMID:25757985

  5. Hybrid quantum magnetic-field sensor with an electron spin and a nuclear spin in diamond

    NASA Astrophysics Data System (ADS)

    Matsuzaki, Yuichiro; Shimo-Oka, Takaaki; Tanaka, Hirotaka; Tokura, Yasuhiro; Semba, Kouichi; Mizuochi, Norikazu

    2016-11-01

    Recently, magnetic-field sensors based on an electron spin of a nitrogen vacancy center in diamond have been studied both from an experimental and theoretical point of view. This system provides a nanoscale magnetometer, and it is possible to detect a precession of a single spin. In this paper, we propose a sensor consisting of an electron spin and a nuclear spin in diamond. Although the electron spin has a reasonable interaction strength with magnetic field, the coherence time of the spin is relatively short. On the other hand, the nuclear spin has a longer lifetime while the spin has a negligible interaction with magnetic fields. We show that, through the combination of such two different spins via the hyperfine interaction, it is possible to construct a magnetic-field sensor with the sensitivity far beyond that of previous sensors using just a single electron spin.

  6. The second Born approximation for the double ionization of N2 by electron impact

    NASA Astrophysics Data System (ADS)

    Lamy, P.; Dal Cappello, C.; Charpentier, I.; Ruiz-Lopez, M. F.; Hervieux, P. A.

    2016-07-01

    In their (e,3e) and (e,3-1e) experiments of the double ionization (DI) of the outermost orbital of N2, Li et al (2012 J. Phys. B: At. Mol. Opt. Phys. 45 135201) recently showed that the process is largely dominated by a two-step-2 mechanism, which is a double interaction of the incident electron with the target. From a theoretical point of view, this should entail the use of the second Born approximation. In the past, very few theoretical calculations had been carried out this way because it requires a difficult numerical triple integration. We propose here to take into account the second Born approximation for the DI of N2 by using the closure approximation. The initial state is described by a single-center wave function derived from the usual multi-center wave function obtained in the self-consistent-field Hartree-Fock method using the linear combination of atomic orbitals-molecular orbital (LCAO-MO) approximation. The final state describes the interaction between each of the ejected electrons and the target by a Coulomb wave and the interaction between the two ejected electrons with the use of the Gamow factor. We calculate differential cross sections using the same kinematic conditions as Li et al (intermediate incident energy about 600 eV) for (e,3e) and (e,3-1e) DI of N2. The results show that the model does not allow a shift of the variation of the four-fold differential cross section near the momentum transfer to be obtained nor its opposite when we include the contribution given by the second Born approximation, as in (e,3-1e) experiments.

  7. Quasi-Monoenergetic Dense and Uniform Electron Bunch Generation from Laser Driven Double-Layer Thin Films

    NASA Astrophysics Data System (ADS)

    Wang, C.; Roycroft, R.; McCary, E.; Meadows, A.; Blakeney, J.; Serratto, K.; Kuk, D.; Chester, C.; Gao, L.; Fu, H.; Yan, X. Q.; Schreiber, J.; Pomerantz, I.; Bernstein, A.; Quevedo, H.; Dyer, G.; Gaul, E.; Ditmire, T.; Gautier, D. C.; Fernandez, J.; Hegelich, B. M.

    2014-10-01

    We demonstrate that dense, uniform quasi-monoenergetic relativistic electron bunches can be generated from the interaction of a high-intensity laser pulse with a double-layer thin film target. The first layer of the target is a freestanding, nanometer-scale, diamond-like carbon production layer. The second layer is a thin plastic reflection layer which reflects the drive-laser pulse, but allows electrons to pass through. Although no electron bunch is generated from the second layer alone, by adding it behind the first layer we obtained a quasi-monoenergetic bunch along the laser axis, 35 times denser than a bunch from the single layer target. Comparing the angular distribution of the electron spectra from a double-layer target with that of a single-layer target, we observed an increase of the electron cutoff energy at larger angles, which improves the uniformity of created electron bunches.

  8. One-electron versus electron-electron interaction contributions to the spin-spin coupling mechanism in nuclear magnetic resonance spectroscopy: analysis of basic electronic effects.

    PubMed

    Gräfenstein, Jürgen; Cremer, Dieter

    2004-12-22

    For the first time, the nuclear magnetic resonance (NMR) spin-spin coupling mechanism is decomposed into one-electron and electron-electron interaction contributions to demonstrate that spin-information transport between different orbitals is not exclusively an electron-exchange phenomenon. This is done using coupled perturbed density-functional theory in conjunction with the recently developed J-OC-PSP [=J-OC-OC-PSP: Decomposition of J into orbital contributions using orbital currents and partial spin polarization)] method. One-orbital contributions comprise Ramsey response and self-exchange effects and the two-orbital contributions describe first-order delocalization and steric exchange. The two-orbital effects can be characterized as external orbital, echo, and spin transport contributions. A relationship of these electronic effects to zeroth-order orbital theory is demonstrated and their sign and magnitude predicted using simple models and graphical representations of first order orbitals. In the case of methane the two NMR spin-spin coupling constants result from totally different Fermi contact coupling mechanisms. (1)J(C,H) is the result of the Ramsey response and the self-exchange of the bond orbital diminished by external first-order delocalization external one-orbital effects whereas (2)J(H,H) spin-spin coupling is almost exclusively mitigated by a two-orbital steric exchange effect. From this analysis, a series of prediction can be made how geometrical deformations, electron lone pairs, and substituent effects lead to a change in the values of (1)J(C,H) and (2)J(H,H), respectively, for hydrocarbons.

  9. ELCS in ice: cryo-electron microscopy of nuclear envelope-limited chromatin sheets.

    PubMed

    Eltsov, Mikhail; Sosnovski, Sergey; Olins, Ada L; Olins, Donald E

    2014-06-01

    Nuclear envelope-limited chromatin sheets (ELCS) form during excessive interphase nuclear envelope growth in a variety of cells. ELCS appear as extended sheets within the cytoplasm connecting distant nuclear lobes. Cross-section stained images of ELCS, viewed by transmission electron microscopy, resemble a sandwich of apposed nuclear envelopes separated by ∼30 nm, containing a layer of parallel chromatin fibers. In this study, the ultrastructure of ELCS was compared by three different methods: (1) aldehyde fixation/dehydration/plastic embedding/sectioning and staining, (2) high-pressure freezing/freeze substitution into plastic/sectioning and staining, and (3) high-pressure freezing/cryo-sectioning/cryo-electron microscopy. ELCS could be clearly visualized by all three methods and, consequently, must exist in vivo and are not fixation artifacts. The ∼30-nm chromatin fibers could only be observed following aldehyde fixation; none were seen in cryo-sections. Electron microscopic tomography tangential views of aldehyde-fixed ELCS suggested an ordering of the separate chromatin fibers adjacent to the nuclear envelope. Possible mechanisms of this chromatin ordering are discussed.

  10. Dynamical Green's function and an exact optical potential for electron-molecule scattering including nuclear dynamics

    NASA Astrophysics Data System (ADS)

    Brand, Joachim; Cederbaum, Lorenz S.; Meyer, Hans-Dieter

    1999-10-01

    We derive a rigorous optical potential for electron-molecule scattering including the effects of nuclear dynamics by extending the common many-body Green's function approach to optical potentials beyond the fixed-nuclei limit for molecular targets. Our formalism treats the projectile electron and the nuclear motion of the target molecule on the same footing whereby the dynamical optical potential rigorously accounts for the complex many-body nature of the scattering target. One central result of the present work is that the common fixed-nuclei optical potential is a valid adiabatic approximation to the dynamical optical potential even when projectile and nuclear motion are (nonadiabatically) coupled as long as the scattering energy is well below the electronic excitation thresholds of the target. For extremely low projectile velocities, however, when the cross sections are most sensitive to the scattering potential, we expect the influences of the nuclear dynamics on the optical potential to become relevant. For these cases, a systematic way to improve the adiabatic approximation to the dynamical optical potential is presented that yields nonlocal operators with respect to the nuclear coordinates.

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

    PubMed

    Lazzeretti, Paolo

    2012-08-21

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

  12. Present and Future Applications of Digital Electronics in Nuclear Science - a Commercial Prospective

    NASA Astrophysics Data System (ADS)

    Tan, Hui

    2011-10-01

    Digital readout electronics instrumenting radiation detectors have experienced significant advancements in the last decade or so. This on one hand can be attributed to the steady improvements in commercial digital processing components such as analog-to-digital converters (ADCs), digital-to-analog converters (DACs), field-programmable-gate-arrays (FPGAs), and digital-signal-processors (DSPs), and on the other hand can also be attributed to the increasing needs for improved time, position, and energy resolution in nuclear physics experiments, which have spurred the rapid development of commercial off-the-shelf high speed, high resolution digitizers or spectrometers. Absent from conventional analog electronics, the capability to record fast decaying pulses from radiation detectors in digital readout electronics has profoundly benefited nuclear physics researchers since they now can perform detailed pulse processing for applications such as gamma-ray tracking and decay-event selection and reconstruction. In this talk, present state-of-the-art digital readout electronics and its applications in a variety of nuclear science fields will be discussed, and future directions in hardware development for digital electronics will also be outlined, all from the prospective of a commercial manufacturer of digital electronics.

  13. The Effect of Electronic Paramagnetism on Nuclear Magnetic Resonance Frequencies in Metals

    DOE R&D Accomplishments Database

    Townes, C. H.; Herring, C.; Knight, W. D.

    1950-09-22

    Observations on the shifts of nuclear resonances in metals ( Li{sup 7}, Na{sup 23}, Cu {sup 63}, Be{sup 9}, Pb{sup 207}, Al{sup 27}, and Ca{sup 69} ) due to free electron paramagnetism; comparison with theoretical values.

  14. Energy doubling of 42 GeV electrons in a metre-scale plasma wakefield accelerator.

    PubMed

    Blumenfeld, Ian; Clayton, Christopher E; Decker, Franz-Josef; Hogan, Mark J; Huang, Chengkun; Ischebeck, Rasmus; Iverson, Richard; Joshi, Chandrashekhar; Katsouleas, Thomas; Kirby, Neil; Lu, Wei; Marsh, Kenneth A; Mori, Warren B; Muggli, Patric; Oz, Erdem; Siemann, Robert H; Walz, Dieter; Zhou, Miaomiao

    2007-02-15

    The energy frontier of particle physics is several trillion electron volts, but colliders capable of reaching this regime (such as the Large Hadron Collider and the International Linear Collider) are costly and time-consuming to build; it is therefore important to explore new methods of accelerating particles to high energies. Plasma-based accelerators are particularly attractive because they are capable of producing accelerating fields that are orders of magnitude larger than those used in conventional colliders. In these accelerators, a drive beam (either laser or particle) produces a plasma wave (wakefield) that accelerates charged particles. The ultimate utility of plasma accelerators will depend on sustaining ultrahigh accelerating fields over a substantial length to achieve a significant energy gain. Here we show that an energy gain of more than 42 GeV is achieved in a plasma wakefield accelerator of 85 cm length, driven by a 42 GeV electron beam at the Stanford Linear Accelerator Center (SLAC). The results are in excellent agreement with the predictions of three-dimensional particle-in-cell simulations. Most of the beam electrons lose energy to the plasma wave, but some electrons in the back of the same beam pulse are accelerated with a field of approximately 52 GV m(-1). This effectively doubles their energy, producing the energy gain of the 3-km-long SLAC accelerator in less than a metre for a small fraction of the electrons in the injected bunch. This is an important step towards demonstrating the viability of plasma accelerators for high-energy physics applications.

  15. Electron dynamics upon ionization: Control of the timescale through chemical substitution and effect of nuclear motion

    SciTech Connect

    Vacher, Morgane; Bearpark, Michael J.; Robb, Michael A.; Mendive-Tapia, David

    2015-03-07

    Photoionization can generate a non-stationary electronic state, which leads to coupled electron-nuclear dynamics in molecules. In this article, we choose benzene cation as a prototype because vertical ionization of the neutral species leads to a Jahn-Teller degeneracy between ground and first excited states of the cation. Starting with equal populations of ground and first excited states, there is no electron dynamics in this case. However, if we add methyl substituents that break symmetry but do not radically alter the electronic structure, we see charge migration: oscillations in the spin density that we can correlate with particular localized electronic structures, with a period depending on the gap between the states initially populated. We have also investigated the effect of nuclear motion on electron dynamics using a complete active space self-consistent field (CASSCF) implementation of the Ehrenfest method, most previous theoretical studies of electron dynamics having been carried out with fixed nuclei. In toluene cation for instance, simulations where the nuclei are allowed to move show significant differences in the electron dynamics after 3 fs, compared to simulations with fixed nuclei.

  16. Observation of electron emission in the nuclear reaction between protons and deuterons

    NASA Astrophysics Data System (ADS)

    Lipoglavšek, M.; Markelj, S.; Mihovilovič, M.; Petrovič, T.; Štajner, S.; Vencelj, M.; Vesić, J.

    2017-10-01

    Proton-deuteron fusion reaction has been studied using a proton beam with an energy of 260 keV and a deuterium-implanted graphite target. The reaction product, 3He, usually de-excites by γ-ray emission. However, instead of a γ ray, 3He can emit an electron with a discrete energy of 5.6 MeV, due to electron screening in graphite. Such electrons were identified with the ΔE-E technique. The emission of fast electrons shows that electron screening causes the electrons to approach the nuclei during the reaction very closely. Different behavior of nuclear reactions at low and high energies was also demonstrated.

  17. Electron-Nuclear Dynamics in a Quantum Dot under Nonunitary Electron Control

    DTIC Science & Technology

    2011-07-20

    the Overhauser term, while the second is called the ‘‘flip-flop’’ term. The couplings ðtÞ arise from periodic, ultrafast laser fields like those used...a shift of the precession frequency through the Overhauser term ( Overhauser shift). Therefore, we consider first a single nuclear spin interacting...for the nuclear SV: d dtSn ¼ 1TR ðYn 1ÞSn, which gives SnðtÞ ¼ eðYn1Þt=TRSnð0Þ. For small flip-flop coupling (but keeping the Overhauser term to

  18. Neutrinos by double beta decays from 100Mo and nuclear spin-isospin responses

    NASA Astrophysics Data System (ADS)

    Kudomi, N.; Ejiri, H.; Fushimi, K.; Hayashi, K.; Kishimoto, T.; Komori, M.; Kume, K.; Kuramoto, H.; Matsuoka, K.; Ohsumi, H.; Takahisa, K.; Umehara, S.; Yoshida, S.

    2001-06-01

    Spectroscopic studies of neutrino-less double beta decays (0νββ) of 100Mo were made by means of ELEGANT V. The data at Oto lab., being combined with the data at Kamioka, gives stringent limits on the half-life of T1/2 for the 0νββ and the effective Majorana neutrino mass of <2.1 eV(90%C.L.). Spin-isospin responses for neutrinos associated with ββ of 100Mo are discussed. A perspective of double beta decay of 100Mo and a possible proposal of MOON are discussed. .

  19. Effects of electron cyclotron current drive on the evolution of double tearing mode

    SciTech Connect

    Sun, Guanglan Dong, Chunying; Duan, Longfang

    2015-09-15

    The effects of electron cyclotron current drive (ECCD) on the double tearing mode (DTM) in slab geometry are investigated by using two-dimensional compressible magnetohydrodynamics equations. It is found that, mainly, the double tearing mode is suppressed by the emergence of the secondary island, due to the deposition of driven current on the X-point of magnetic island at one rational surface, which forms a new non-complete symmetric magnetic topology structure (defined as a non-complete symmetric structure, NSS). The effects of driven current with different parameters (magnitude, initial time of deposition, duration time, and location of deposition) on the evolution of DTM are analyzed elaborately. The optimal magnitude or optimal deposition duration of driven current is the one which makes the duration of NSS the longest, which depends on the mutual effect between ECCD and the background plasma. Moreover, driven current introduced at the early Sweet-Parker phase has the best suppression effect; and the optimal moment also exists, depending on the duration of the NSS. Finally, the effects varied by the driven current disposition location are studied. It is verified that the favorable location of driven current is the X-point which is completely different from the result of single tearing mode.

  20. AA stacking, tribological and electronic properties of double-layer graphene with krypton spacer.

    PubMed

    Popov, Andrey M; Lebedeva, Irina V; Knizhnik, Andrey A; Lozovik, Yurii E; Potapkin, Boris V; Poklonski, Nikolai A; Siahlo, Andrei I; Vyrko, Sergey A

    2013-10-21

    Structural, energetic, and tribological characteristics of double-layer graphene with commensurate and incommensurate krypton spacers of nearly monolayer coverage are studied within the van der Waals-corrected density functional theory. It is shown that when the spacer is in the commensurate phase, the graphene layers have the AA stacking. For this phase, the barriers to relative in-plane translational and rotational motion and the shear mode frequency of the graphene layers are calculated. For the incommensurate phase, both of the barriers are found to be negligibly small. A considerable change of tunneling conductance between the graphene layers separated by the commensurate krypton spacer at their relative subangstrom displacement is revealed by the use of the Bardeen method. The possibility of nanoelectromechanical systems based on the studied tribological and electronic properties of the considered heterostructures is discussed.

  1. Equation-of-motion coupled cluster method for high spin double electron attachment calculations

    SciTech Connect

    Musiał, Monika Lupa, Łukasz; Kucharski, Stanisław A.

    2014-03-21

    The new formulation of the equation-of-motion (EOM) coupled cluster (CC) approach applicable to the calculations of the double electron attachment (DEA) states for the high spin components is proposed. The new EOM equations are derived for the high spin triplet and quintet states. In both cases the new equations are easier to solve but the substantial simplification is observed in the case of quintets. Out of 21 diagrammatic terms contributing to the standard DEA-EOM-CCSDT equations for the R{sub 2} and R{sub 3} amplitudes only four terms survive contributing to the R{sub 3} part. The implemented method has been applied to the calculations of the excited states (singlets, triplets, and quintets) energies of the carbon and silicon atoms and potential energy curves for selected states of the Na{sub 2} (triplets) and B{sub 2} (quintets) molecules.

  2. On the role of different types of electron in double ring tubular clusters

    NASA Astrophysics Data System (ADS)

    Duong, Long Van; Nguyen, Minh Tho

    2017-10-01

    Partial electron localization functions ELF(σ_loca), ELF(π) and ELF(σ_delo) of boron Bn and silicon MSi12 double ring (DR) clusters were analyzed. In a DR, separated basins are localized within peripheral bonds (σ), delocalized outside inner bonds (π), or delocalized above and below peripheral bonds (σ). MO spectrum of skeleton D6h Si12 DR follows delightfully the hollow cylinder model. A mixture of different sets of MOs makes the D6h Si12 structure highly unstable. Upon interacting with 3d orbitals of Cr dopant, such a mixed behavior of MO sets is removed and the Cr@Si12 DR becomes a global minimum structure.

  3. Optical and electronic properties of double perovskite Ba2ScSbO6

    NASA Astrophysics Data System (ADS)

    Ray, Rajyavardhan; Himanshu, A. K.; Lahiri, J.; Kumar, Uday; Sen, Pintu; Bandyopadhyay, S. K.; Sinha, T. P.

    2016-05-01

    The ordered double perovskite Ba2ScSbO6 (BSS) has been synthesized in polycrystalline form by solid state reaction at 1400 C for 72 Hrs. Structural characterization of the compound was done through X-ray diffraction (XRD) followed by Rietveld analysis. The crystal structure is cubic, with space group Fm-3m (No. 225) and lattice parameter, a = 8.20 Ǻ. Optical band-gap has been calculated using UV-Vis Spectroscopy and Kubelka-Munk (KM) function, yielding 4.23 eV. A detailed Ab-initio Density Functional Theory (DFT) study of the electronic properties has been carried out using the Full-Potential Linear Augmented Plane Wave (FP-LAPW) as implemented in WIEN2k. BSS is found to be a large band-gap insulator with potential technological applications.

  4. Crystallographic, Ferroelectric and Electronic Properties of the Sr2ZrTiO6 Double Perovskite

    NASA Astrophysics Data System (ADS)

    Landínez Téllez, D. A.; Carrero Bermúdez, L. A.; Deluque Toro, C. E.; Cardona, R.; Roa-Rojas, J.

    2013-08-01

    In this paper, we report structural analysis, ferroelectric behavior and electronic structure of Sr2ZrTiO6 double perovskite. Samples were produced by the solid state reaction recipe. Crystallographic analysis was performed by Rietveld refinement of experimental X-ray diffraction patterns. Results show that this material crystallizes in a tetragonal perovskite structure which corresponds to the space group I4/m. The curve of polarization as a function of applied voltage evidences a ferroelectric character with saturation polarization on the application of voltages up to 1800 V. Calculations of density of states and band structure for this manganite-like material were carried out by means of the density functional theory implemented into the Wien2k code. Results of total and partial density of states reveal the insulator character of this material with an energy gap of 2.66 eV.

  5. Examination of the possible enhancement of neutrinoless double-electron capture in 78Kr

    NASA Astrophysics Data System (ADS)

    Bustabad, S.; Bollen, G.; Brodeur, M.; Lincoln, D. L.; Novario, S. J.; Redshaw, M.; Ringle, R.; Schwarz, S.

    2013-09-01

    Penning-trap mass spectrometry was used at the Low-Energy Beam and Ion Trap (LEBIT) facility at the National Superconducting Cyclotron Laboratory (NSCL) to investigate 78Kr, a candidate for resonantly enhanced neutrinoless double-electron capture (0νECEC). The newly determined Q value of 2847.75 (27) keV is 1.4 keV greater than the value from the most recent atomic mass evaluation [Chin. Phys. C1674-113710.1088/1674-1137/36/12/003 36, 1603 (2012)], a change of two sigma, and the uncertainty has been reduced by a factor of three. The change in the Q value shifts allowed 0νECEC in 78Kr further from resonant enhancement. With the improved determination of the Q value, all known excited states can now be confidently excluded from possible 78Se candidates that could lead to resonantly enhanced 0νECEC.

  6. Electron-atom bremsstrahlung: Double-differential cross section and polarization correlations

    NASA Astrophysics Data System (ADS)

    Yerokhin, Vladimir A.; Surzhykov, Andrey

    2010-12-01

    The leading-order electron-atom bremsstrahlung is investigated within the rigorous relativistic approach based on the partial-wave representation of the Dirac wave functions in the external atomic field. Approximating the atomic target by an effective local potential, we calculate the double-differential cross section and the polarization correlations in a wide range of the impact energies. Connection between the bremsstrahlung at the hard-photon end point of the spectrum and the continuum-threshold limit of the radiative recombination is studied. A detailed analysis of the screening effect and the energy dependence of the polarization correlations is presented, with the main focus on the high-impact-energy region.

  7. Effect of interdots electronic repulsion in the Majorana signature for a double dot interferometer

    NASA Astrophysics Data System (ADS)

    Ricco, L. S.; Marques, Y.; Dessotti, F. A.; de Souza, M.; Seridonio, A. C.

    2016-04-01

    We investigate theoretically the features of the Majorana hallmark in the presence of Coulomb repulsion between two quantum dots describing a spinless double dot interferometer, where one of the dots is strongly coupled to a Kitaev wire within the topological phase. Such a system has been originally proposed without Coulomb interaction in Dessotti et al. (2014 [16]) . Our findings reveal that for dots in resonance, the ratio between the strength of Coulomb repulsion and the dot-wire coupling changes the width of the Majorana zero-bias peak for both Fano regimes studied, indicating thus that the electronic interdots correlation influences the Majorana state lifetime in the dot hybridized with the wire. Moreover, for the off-resonance case, the swap between the energy levels of the dots also modifies the width of the Majorana peak, which does not happen for the noninteracting case. The results obtained here can guide experimentalists that pursuit a way of revealing Majorana signatures.

  8. Counter-diabatic driving for fast spin control in a two-electron double quantum dot

    PubMed Central

    Ban, Yue; Chen, Xi

    2014-01-01

    The techniques of shortcuts to adiabaticity have been proposed to accelerate the “slow” adiabatic processes in various quantum systems with the applications in quantum information processing. In this paper, we study the counter-diabatic driving for fast adiabatic spin manipulation in a two-electron double quantum dot by designing time-dependent electric fields in the presence of spin-orbit coupling. To simplify implementation and find an alternative shortcut, we further transform the Hamiltonian in term of Lie algebra, which allows one to use a single Cartesian component of electric fields. In addition, the relation between energy and time is quantified to show the lower bound for the operation time when the maximum amplitude of electric fields is given. Finally, the fidelity is discussed with respect to noise and systematic errors, which demonstrates that the decoherence effect induced by stochastic environment can be avoided in speeded-up adiabatic control. PMID:25174453

  9. Competing Effects Of Electronic And Nuclear Energy Loss On Microstructural Evolution In Ionic-covalent Materials

    SciTech Connect

    Zhang, Yanwen; Varga, Tamas; Ishimaru, Manabu; Edmondson, P. D.; Xue, H.; Liu, Peng; Moll, Sandra; Hardiman, Christopher M.; Shannon, Steven; Weber, William J.

    2014-05-01

    Ever increasing energy needs have raised the demands for advanced fuels and cladding materials that withstand the extreme radiation environments with improved accident tolerance over a long period of time. Ceria (CeO2) is a well known ionic conductor that is isostructural with urania and plutonia-based nuclear fuels. In the context of nuclear fuels, immobilization and transmutation of actinides, CeO2 is a model system for radiation effect studies. Covalent silicon carbide (SiC) is a candidate for use as structural material in fusion, cladding material for fission reactors, and an inert matrix for the transmutation of plutonium and other radioactive actinides. Understanding microstructural change of these ionic-covalent materials to irradiation is important for advanced nuclear energy systems. While displacements from nuclear energy loss may be the primary contribution to damage accumulation in a crystalline matrix and a driving force for the grain boundary evolution in nanostructured materials, local non-equilibrium disorder and excitation through electronic While displacements from nuclear energy loss may be the primary contribution to damage accumulation in a crystalline matrix and a driving force for the grain boundary evolution in nanostructured materials, local non-equilibrium disorder and excitation through electronic energy loss may, however, produce additional damage or anneal pre-existing defect. At intermediate transit energies where electronic and nuclear energy losses are both significant, synergistic, additive or competitive processes may evolve that affect the dynamic response of materials to irradiation. The response of crystalline and nanostructured CeO2 and SiC to ion irradiation are studied under different nuclear and electronic stopping powers to describe some general material response in this transit energy regime. Although fast radiation-induced grain growth in CeO2 is evident with no phase transformation, different fluence and dose dependence

  10. Enhancing the Number of High-Energy Electrons Deposited to a Compressed Pellet via Double Cones in Fast Ignition

    SciTech Connect

    Cai Hongbo; Mima, Kunioki; Zhou Weimin; Jozaki, Tomoyuki; Nagatomo, Hideo; Sunahara, Atsushi; Mason, Rodney J.

    2009-06-19

    Particle-in-cell simulations aimed at improving the coupling efficiency of input laser energy deposited to a compressed core by using a double cone are described. It is found that the number of high-energy electrons escaping from the sides of the cone is greatly reduced by the vacuum gap inside the wing of the double cone. Two main mechanisms to confine high-energy electrons are found. These mechanisms are the sheath electric field at the rear of the inner cone wing and the quasistatic magnetic field inside the vacuum gap. The generation mechanism for the quasistatic magnetic fields is discussed in detail. It is found that the quasistatic fields continue to confine the high-energy electrons for longer than a few picoseconds. The double cones provide confinement and focusing of about 15% of the input energy for deposition in the compressed core.

  11. Electron and nuclear dynamics in many-electron atoms, molecules and chlorophyll-protein complexes: a review.

    PubMed

    Shuvalov, Vladimir A

    2007-06-01

    It has been shown [V.A. Shuvalov, Quantum dynamics of electrons in many-electron atoms of biologically important compounds, Biochemistry (Mosc.) 68 (2003) 1333-1354; V.A. Shuvalov, Quantum dynamics of electrons in atoms of biologically important molecules, Uspekhi biologicheskoi khimii, (Pushchino) 44 (2004) 79-108] that the orbit angular momentum L of each electron in many-electron atoms is L=mVr=nPlanck's and similar to L for one-electron atom suggested by N. Bohr. It has been found that for an atom with N electrons the total electron energy equation E=-(Z(eff))(2)e(4)m/(2n(2)Planck's(2)N) is more appropriate for energy calculation than standard quantum mechanical expressions. It means that the value of L of each electron is independent of the presence of other electrons in an atom and correlates well to the properties of virtual photons emitted by the nucleus and creating a trap for electrons. The energies for elements of the 1st up to the 5th rows and their ions (total amount 240) of Mendeleev' Periodical table were calculated consistent with the experimental data (deviations in average were 5 x 10(-3)). The obtained equations can be used for electron dynamics calculations in molecules. For H(2) and H(2)(+) the interference of electron-photon orbits between the atoms determines the distances between the nuclei which are in agreement with the experimental values. The formation of resonance electron-photon orbit in molecules with the conjugated bonds, including chlorophyll-like molecules, appears to form a resonance trap for an electron with E values close to experimental data. Two mechanisms were suggested for non-barrier primary charge separation in reaction centers (RCs) of photosynthetic bacteria and green plants by using the idea of electron-photon orbit interference between the two molecules. Both mechanisms are connected to formation of the exciplexes of chlorophyll-like molecules. The first one includes some nuclear motion before exciplex formation, the

  12. Estimations of electron densities and temperatures in He-3 dominated plasmas. [in nuclear pumped lasers

    NASA Technical Reports Server (NTRS)

    Depaola, B. D.; Marcum, S. D.; Wrench, H. K.; Whitten, B. L.; Wells, W. E.

    1979-01-01

    It is very useful to have a method of estimation for electron temperature and electron densities in nuclear pumped plasmas because measurements of such quantities are very difficult. This paper describes a method, based on rate equation analysis of the ionized species in the plasma and the electron energy balance. In addition to the ionized species, certain neutral species must also be calculated. Examples are given for pure helium and a mixture of helium and argon. In the HeAr case, He(+), He2(+), He/2 3S/, Ar(+), Ar2(+), and excited Ar are evaluated.

  13. Monitoring Nonadiabatic Electron-Nuclear Dynamics in Molecules by Attosecond Streaking of Photoelectrons

    NASA Astrophysics Data System (ADS)

    Kowalewski, Markus; Bennett, Kochise; Rouxel, Jérémy R.; Mukamel, Shaul

    2016-07-01

    Streaking of photoelectrons has long been used for the temporal characterization of attosecond extreme ultraviolet pulses. When the time-resolved photoelectrons originate from a coherent superposition of electronic states, they carry additional phase information, which can be retrieved by the streaking technique. In this contribution we extend the streaking formalism to include coupled electron and nuclear dynamics in molecules as well as initial coherences. We demonstrate how streaked photoelectrons offer a novel tool for monitoring nonadiabatic dynamics as it occurs in the vicinity of conical intersections and avoided crossings. Streaking can provide high time resolution direct signatures of electronic coherences, which affect many primary photochemical and biological events.

  14. Double ionization effect in electron accelerations by high-intensity laser pulse interaction with a neutral gas

    NASA Astrophysics Data System (ADS)

    Nandan Gupta, Devki

    2013-11-01

    We study the effect of laser-induced double-ionization of a helium gas (with inhomogeneous density profile) on vacuum electron acceleration. For enough laser intensity, helium gas can be found doubly ionized and it strengthens the divergence of the pulse. The double ionization of helium gas can defocus the laser pulse significantly, and electrons are accelerated by the front of the laser pulse in vacuum and then decelerated by the defocused trail part of the laser pulse. It is observed that the electrons experience a very low laser-intensity at the trailing part of the laser pulse. Hence, there is not much electron deceleration at the trailing part of the pulse. We found that the inhomogeneity of the neutral gas reduced the rate of tunnel ionization causing less defocusing of the laser pulse and thus the electron energy gain is reduced.

  15. Double electron–electron resonance reveals cAMP-induced conformational change in HCN channels

    PubMed Central

    Zagotta, William N.; Stoll, Stefan

    2014-01-01

    Binding of 3′,5′-cyclic adenosine monophosphate (cAMP) to hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channels regulates their gating. cAMP binds to a conserved intracellular cyclic nucleotide-binding domain (CNBD) in the channel, increasing the rate and extent of activation of the channel and shifting activation to less hyperpolarized voltages. The structural mechanism underlying this regulation, however, is unknown. We used double electron–electron resonance (DEER) spectroscopy to directly map the conformational ensembles of the CNBD in the absence and presence of cAMP. Site-directed, double-cysteine mutants in a soluble CNBD fragment were spin-labeled, and interspin label distance distributions were determined using DEER. We found motions of up to 10 Å induced by the binding of cAMP. In addition, the distributions were narrower in the presence of cAMP. Continuous-wave electron paramagnetic resonance studies revealed changes in mobility associated with cAMP binding, indicating less conformational heterogeneity in the cAMP-bound state. From the measured DEER distributions, we constructed a coarse-grained elastic-network structural model of the cAMP-induced conformational transition. We find that binding of cAMP triggers a reorientation of several helices within the CNBD, including the C-helix closest to the cAMP-binding site. These results provide a basis for understanding how the binding of cAMP is coupled to channel opening in HCN and related channels. PMID:24958877

  16. Analysis of the H(2)(+) with H(2) reaction using electron nuclear dynamics

    NASA Astrophysics Data System (ADS)

    Oreiro, Juan J. G.

    The END formalism addresses the solution of the time- dependent Schrodinger equation, treating both electrons and nuclei simultaneously. It differs from the other traditional fully quantum mechanical time-dependent methods in that it does not require a potential energy surface (PES) to carry the nuclear motion. The interaction between electronic and nuclear motion is, therefore, obtained in a transparent way, not relying on PES gradients to obtain the coupling between electrons and nuclei. We analyze the H2+ + H2 reaction at energies below 4 eV using different approximations and basis sets. Other than the choice of initial conditions, form of wave function, and basis set, no constraints are imposed on the system evolution. The nuclei are treated in the classical limit, and the electronic part is described by a single determinantal, unrestricted wave function. We obtain properties, such as Mulliken populations, transition probabilities, and cross-sections, from the resulting trajectories. These results are compared with other current theoretical approaches, and with experimental values. The relevance of the electron- nuclear coupling is estimated by comparing the END trajectories with molecular dynamics calculations for selected initial conditions in different basis sets.

  17. Electron and nuclear spin polarization in Rb-Xe spin-exchange optical hyperpolarization

    NASA Astrophysics Data System (ADS)

    Hanni, Matti; Lantto, Perttu; Repiský, Michal; Mareš, Jiří; Saam, Brian; Vaara, Juha

    2017-03-01

    Spin-exchange optical hyperpolarization of 129Xe gas enhances the signal-to-noise ratio in nuclear magnetic resonance experiments. The governing parameter of the Rb-Xe spin-exchange process, the so-called enhancement factor, was recently reevaluated experimentally. However, the underlying hyperfine coupling and atomic interaction potential as functions of the internuclear distance of the open-shell Rb-Xe dimer have not been accurately determined to date. We present a piecewise approximation based on first-principles calculations of these parameters contributing to the NMR and EPR frequency shifts in the low-density Rb-Xe gas mixture of relevance to hyperpolarization experiments. Both Rb electron and 129Xe nuclear spin polarizations are estimated based on a combination of electronic-structure calculations, observed frequency shifts, and an estimate of the Rb number density. Finally, an expression for the enhancement factor in terms of modern electronic-structure theory is obtained.

  18. Energetic electron processes fluorescence effects for structured nanoparticles X-ray analysis and nuclear medicine applications

    NASA Astrophysics Data System (ADS)

    Taborda, A.; Desbrée, A.; Carvalho, A.; Chaves, P. C.; Reis, M. A.

    2016-08-01

    Superparamagnetic iron oxide (SPIO) nanoparticles are widely used as contrast agents for nuclear magnetic resonance imaging (MRI), and can be modified for improved imaging or to become tissue-specific or even protein-specific. The knowledge of their detailed elemental composition characterisation and potential use in nuclear medicine applications, is, therefore, an important issue. X-ray fluorescence techniques such as particle induced X-ray emission (PIXE) or X-ray fluorescence spectrometry (XRF), can be used for elemental characterisation even in problematic situations where very little sample volume is available. Still, the fluorescence coefficient of Fe is such that, during the decay of the inner-shell ionised atomic structure, keV Auger electrons are produced in excess to X-rays. Since cross-sections for ionisation induced by keV electrons, for low atomic number atoms, are of the order of 103 barn, care should be taken to account for possible fluorescence effects caused by Auger electrons, which may lead to the wrong quantification of elements having atomic number lower than the atomic number of Fe. Furthermore, the same electron processes will occur in iron oxide nanoparticles containing 57Co, which may be used for nuclear medicine therapy purposes. In the present work, simple approximation algorithms are proposed for the quantitative description of radiative and non-radiative processes associated with Auger electrons cascades. The effects on analytical processes and nuclear medicine applications are quantified for the case of iron oxide nanoparticles, by calculating both electron fluorescence emissions and energy deposition on cell tissues where the nanoparticles may be embedded.

  19. Quantum Trajectory-Electronic Structure Approach for Exploring Nuclear Effects in the Dynamics of Nanomaterials.

    PubMed

    Garashchuk, Sophya; Jakowski, Jacek; Wang, Lei; Sumpter, Bobby G

    2013-12-10

    A massively parallel, direct quantum molecular dynamics method is described. The method combines a quantum trajectory (QT) representation of the nuclear wave function discretized into an ensemble of trajectories with an electronic structure (ES) description of electrons, namely using the density functional tight binding (DFTB) theory. Quantum nuclear effects are included into the dynamics of the nuclei via quantum corrections to the classical forces. To reduce computational cost and increase numerical accuracy, the quantum corrections to dynamics resulting from localization of the nuclear wave function are computed approximately and included into selected degrees of freedom representing light particles where the quantum effects are expected to be the most pronounced. A massively parallel implementation, based on the message passing interface allows for efficient simulations of ensembles of thousands of trajectories at once. The QTES-DFTB dynamics approach is employed to study the role of quantum nuclear effects on the interaction of hydrogen with a model graphene sheet, revealing that neglect of nuclear effects can lead to an overestimation of adsorption.

  20. Photo-electron double regulated resistive switching memory behaviors of Ag/CuWO4/FTO device

    NASA Astrophysics Data System (ADS)

    Sun, B.; Jia, X. J.; Wu, J. H.; Chen, P.

    2015-12-01

    In this work, the CuWO4 film based resistive switching memory capacitors were fabricated with hydrothermal and spin-coating approaches. The device exhibits excellent photo-electron double controlled resistive switching memory characteristics with OFF/ON resistance ratio of ~103. It is believed that the interface of CuWO4 and FTO is responsible for such a switching behavior and it can be described by the Schottky-like barriers model. This study is useful for exploring the multifunctional materials and their applications in photo-electron double controlled nonvolatile memory devices.