5,906 research outputs found

    Interpretation of Coulomb breakup of 31Ne in terms of deformation

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    The recent experimental data on Coulomb breakup of the nucleus 31^{31}Ne are interpreted in terms of deformation. The measured large one-neutron removal cross-section indicates that the ground state of 31^{31}Ne is either s- or p-halo. The data can be most easily interpreted as the spin of the ground state being 3/2−^- coming from either the Nilsson level [330 1/2] or [321 3/2] depending on the neutron separation energy SnS_n. However, the possibility of 1/2+^{+} coming from [200 1/2] is not excluded. It is suggested that if the large ambiguity in the measured value of SnS_n of 31^{31}Ne, 0.29±1.64\pm1.64 MeV, can be reduced by an order of magnitude, say to be ±\pm100 keV, one may get a clear picture of the spin-parity of the halo ground state.Comment: 8 pages, 4 figure

    Nilsson diagrams for light neutron-rich nuclei with weakly-bound neutrons

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    Using Woods-Saxon potentials and the eigenphase formalism for one-particle resonances, one-particle bound and resonant levels for neutrons as a function of quadrupole deformation are presented, which are supposed to be useful for the interpretation of spectroscopic properties of some light neutron-rich nuclei with weakly-bound neutrons. Compared with Nilsson diagrams in text books which are constructed using modified oscillator potentials, we point out a systematic change of the shell structure in connection with both weakly-bound and resonant one-particle levels related to small orbital angular momenta ℓ\ell. Then, it is seen that weakly-bound neutrons in nuclei such as 15−19^{15-19}C and 33−37^{33-37}Mg may prefer to being deformed as a result of Jahn-Teller effect, due to the near degeneracy of the 1d5/2_{5/2}-2s1/2_{1/2} levels and the 1f7/2_{7/2}-2p3/2_{3/2} levels in the spherical potential, respectively. Furthermore, the absence of some one-particle resonant levels compared with the Nilsson diagrams in text books is illustrated.Comment: 12 pages, 5 figure

    Coulomb corrections to superallowed beta decay in nuclei

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    Corrections to the superallowed beta decay matrix elements are evaluated in perturbation theory using the notion of the isovector monopole resonance. The calculation avoids the separation into different contributions and thus presents a consistent, systematic and more transparent approach. Explicit expressions for the Coulomb correction as a function of mass number A, are given.Comment: 10 page

    The intruder feature of 31Mg and the coexistence of many particle and many hole states

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    The low-lying level structure of 31Mg^{31}{\rm Mg} has been investigated by the antisymmetrized molecular dynamics (AMD) plus generator coordinate method (GCM) with the Gogny D1S force. It is shown that the N=20 magic number is broken and the ground state has the pure neutron 2p3h2p3h configuration. The coexistence of many particle and many hole states at very low excitation energy is discussed

    Complementarity and Scientific Rationality

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    Bohr's interpretation of quantum mechanics has been criticized as incoherent and opportunistic, and based on doubtful philosophical premises. If so Bohr's influence, in the pre-war period of 1927-1939, is the harder to explain, and the acceptance of his approach to quantum mechanics over de Broglie's had no reasonable foundation. But Bohr's interpretation changed little from the time of its first appearance, and stood independent of any philosophical presuppositions. The principle of complementarity is itself best read as a conjecture of unusually wide scope, on the nature and future course of explanations in the sciences (and not only the physical sciences). If it must be judged a failure today, it is not because of any internal inconsistency.Comment: 29 page

    On the relation between E(5)−E(5)-models and the interacting boson model

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    The connections between the E(5)−E(5)-models (the original E(5) using an infinite square well, E(5)−β4E(5)-\beta^4, E(5)−β6E(5)-\beta^6 and E(5)−β8E(5)-\beta^8), based on particular solutions of the geometrical Bohr Hamiltonian with γ\gamma-unstable potentials, and the interacting boson model (IBM) are explored. For that purpose, the general IBM Hamiltonian for the U(5)−O(6)U(5)-O(6) transition line is used and a numerical fit to the different E(5)−E(5)-models energies is performed, later on the obtained wavefunctions are used to calculate B(E2) transition rates. It is shown that within the IBM one can reproduce very well all these E(5)−E(5)-models. The agreement is the best for E(5)−β4E(5)-\beta^4 and reduces when passing through E(5)−β6E(5)-\beta^6, E(5)−β8E(5)-\beta^8 and E(5), where the worst agreement is obtained (although still very good for a restricted set of lowest lying states). The fitted IBM Hamiltonians correspond to energy surfaces close to those expected for the critical point. A phenomenon similar to the quasidynamical symmetry is observed

    Model of molecular bonding based on the Bohr-Sommerfeld picture of atoms

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    We develop a model of molecular binding based on the Bohr-Sommerfeld description of atoms together with a constraint taken from conventional quantum mechanics. The model can describe the binding energy curves of H2, H3 and other molecules with striking accuracy. Our approach treats electrons as point particles with positions determined by extrema of an algebraic energy function. Our constrained model provides a physically appealing, accurate description of multi-electron chemical bonds.Comment: 5 pages, 7 figures, to appear in Physics Letters

    Stellar weak decay rates in neutron-deficient medium-mass nuclei

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    Weak decay rates under stellar density and temperature conditions holding at the rapid proton capture process are studied in neutron-deficient medium-mass waiting point nuclei extending from Ni up to Sn. Neighboring isotopes to these waiting point nuclei are also included in the analysis. The nuclear structure part of the problem is described within a deformed Skyrme Hartree-Fock + BCS + QRPA approach, which reproduces not only the beta-decay half-lives but also the available Gamow-Teller strength distributions, measured under terrestrial conditions. The various sensitivities of the decay rates to both density and temperature are discussed. In particular, we study the impact of contributions coming from thermally populated excited states in the parent nucleus, as well as the competition between beta decays and continuum electron captures.Comment: 24 pages, 16 figure

    Relationship between X(5)-models and the interacting boson model

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    The connections between the X(5)-models (the original X(5) using an infinite square well, X(5)-β8\beta^8, X(5)-β6\beta^6, X(5)-β4\beta^4, and X(5)-β2\beta^2), based on particular solutions of the geometrical Bohr Hamiltonian with harmonic potential in the γ\gamma degree of freedom, and the interacting boson model (IBM) are explored. This work is the natural extension of the work presented in [1] for the E(5)-models. For that purpose, a quite general one- and two-body IBM Hamiltonian is used and a numerical fit to the different X(5)-models energies is performed, later on the obtained wave functions are used to calculate B(E2) transition rates. It is shown that within the IBM one can reproduce well the results for energies and B(E2) transition rates obtained with all these X(5)-models, although the agreement is not so impressive as for the E(5)-models. From the fitted IBM parameters the corresponding energy surface can be extracted and it is obtained that, surprisingly, only the X(5) case corresponds in the moderate large N limit to an energy surface very close to the one expected for a critical point, while the rest of models seat a little farther.Comment: Accepted in Physical Review

    Self-consistent Skyrme QRPA for use in axially-symmetric nuclei of arbitrary mass

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    We describe a new implementation of the quasiparticle random phase approximation (QRPA) in axially-symmetric deformed nuclei with Skyrme and volume-pairing energy-density functionals. After using a variety of tests to demonstrate the accuracy of the code in ^{24,26}Mg and ^{16}O, we report the first fully self-consistent application of the Skyrme QRPA to a heavy deformed nucleus, calculating strength distributions for several K^pi in ^{172}Yb. We present energy-weighted sums, properties of gamma-vibrational and low-energy K^pi=0^+ states, and the complete isovector E1 strength function. The QRPA calculation reproduces the properties of the low-lying 2^+ states as well or better than it typically does in spherical nuclei.Comment: 5 pages, 6 figure
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