976 research outputs found

    NMR paramagnetic relaxation due to the S = 5/2S=5∕2 complex, Fe(III)-(tetra-p-sulfonatophenyl)porphyrin: Central role of the tetragonal fourth-order zero-field splitting interaction

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    The metalloporphyrins, Me-TSPP [Me = Cr(III)Me=Cr(III), Mn(III), Mn(II), Fe(III), and TSPP=meso-(tetra-pp-sulfonatophenyl)porphyrin], which possess electron spins S = 3/2S=3∕2, 2, 5/25∕2, and 5/25∕2, respectively, comprise an important series of model systems for mechanistic studies of NMR paramagnetic relaxation enhancement (NMR-PRE). For these S>1/2S>1∕2 spin systems, the NMR-PRE depends critically on the detailed form of the zero-field splitting (zfs) tensor. We report the results of experimental and theoretical studies of the NMR relaxation mechanism associated with Fe(III)-TSPP, a spin 5/25∕2 complex for which the overall zfs is relatively large (D ≈ 10 cm−1)(D≈10cm−1). A comparison of experimental data with spin dynamics simulations shows that the primary determinant of the shape of the magnetic relaxation dispersion profile of the water proton R1R1 is the tetragonal fourth-order component of the zfs tensor. The relaxation mechanism, which has not previously been described, is a consequence of zfs-induced mixing of the spin eigenfunctions of adjacent Kramers doublets. We have also investigated the magnetic-field dependence of electron-spin relaxation for S = 5/2S=5∕2 in the presence of a large zfs, such as occurs in Fe(III)-TSPP. Calculations show that field dependence of this kind is suppressed in the vicinity of the zfs limit, in agreement with observation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87861/2/184501_1.pd

    The higher order Rogue Wave solutions of the Gerdjikov-Ivanov equation

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    We construct higher order rogue wave solutions for the Gerdjikov-Ivanov equation explicitly in term of determinant expression. Dynamics of both soliton and non-soliton solutions is discussed. A family of solutions with distinct structures are presented, which are new to the Gerdjikov-Ivanov equation

    Final-state interactions in the response of nuclear matter

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    Final-state interactions in the response of a many-body system to an external probe delivering large momentum are normally described using the eikonal approximation, for the trajectory of the struck particle, and the frozen approximation, for the positions of the spectators. We propose a generalization of this scheme, in which the initial momentum of the struck particle is explicitly taken into account. Numerical calculations of the nuclear matter response at 1 <∣q∣<< |{\bf q}| < 2 GeV/c show that the inclusion of this momentum dependence leads to a sizable effect in the low energy tail. Possible implications for the analysis of existing electron-nucleus scattering data are discussed.Comment: 21 pages, 4 figure

    Phase-noise reduction in self-injection locked oscillators using slow-wave structures

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    An analysis of self-injection locked oscillators using a slow-wave structure for phase-noise reduction is presented. This structure is the key component of a feedback network, added to an existing oscillator and providing a stable self-injection locking signal. The unit cell of the slow-wave structure is based on a recently proposed configuration, made up of an open-ended stub and a Schiffman section. A tuning capacitor is introduced as an additional parameter, enabling an adjustment of the structure response at the desired oscillation frequency. The circuit solutions are analyzed by means of a semi-analytical formulation that incorporates the results of an electromagnetic simulation of the structure. The formulation enables a prediction of multivalued parameter regions, inherent to the long delay, which are more controllable than in the case of continuous transmission lines. An analytical derivation of the phase-noise spectral density is presented, which relates the phase-noise reduction with respect to the original freerunning oscillator to the group delay of the self-injection network. The analysis and synthesis method has been applied to an oscillator at 2.75 GHz.This work was supported by the Spanish Ministry of Science, Innovation and Universities and the European Regional Development Fund (ERDF/FEDER) under the research project TEC2017-88242-C3-1-R

    In medium T-matrix for superfluid nuclear matter

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    We study a generalized ladder resummation in the superfluid phase of the nuclear matter. The approach is based on a conserving generalization of the usual T-matrix approximation including also anomalous self-energies and propagators. The approximation here discussed is a generalization of the usual mean-field BCS approach and of the in medium T-matrix approximation in the normal phase. The numerical results in this work are obtained in the quasi-particle approximation. Properties of the resulting self-energy, superfluid gap and spectral functions are studied.Comment: 38 pages, 19 figures, Introduction rewritten, Refs. adde
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