The elastic scattering of 6He on 208Pb has been measured at laboratory energies of
14, 16, 18 and 22 MeV. These data were analyzed using phenomenological Woods-
Saxon form factors and optical model calculations. A semiclassical polarization po-
tential was used to study the e ect of the Coulomb dipole polarizability. Evidence
for long range absorption, partially arising from Coulomb dipole polarizability, is
reported. The energy variation of the optical potential was found to be consistent
with the dispersion relations which connect the real and imaginary parts of the
potential
The evolution of the nuclear shapes along the triaxial landscape is studied in the Pt isotopic chain using the self-consistent Hartree-Fock-Bogoliubov approximation based on the Gogny interaction. In addition to the parametrization D1S, the new incarnations D1N and D1M of this force are also included in our analysis to assess to which extent the predictions are independent of details of the effective interaction. The considered range of neutron numbers 88 N 126 includes prolate, triaxial, oblate, and spherical ground-state shapes and serves as a detailed comparison of the predictions obtained with the new sets D1N and D1M against the ones provided by the standard parametrization Gogny-D1S in a region of the nuclear landscape for which experimental and theoretical fingerprints of shape transitions have been found. Structural evolution along the Pt chain is discussed in terms of the deformation dependence of single-particle energies.
Article:Bree, N., Wrzosek-Lipska, K., Petts, A. et al. (67 more authors) (2014) Shape coexistence in the neutron-deficient even-even 182-188Hg isotopes studied via Coulomb excitation.
A generic procedure is proposed to construct many-body quantum Hamiltonians with partial dynamical symmetry. It is based on a tensor decomposition of the Hamiltonian and allows the construction of a hierarchy of interactions that have selected classes of solvable states. The method is illustrated in the SO (6) The concept of dynamical symmetry (DS) is now widely accepted to be of central importance in our understanding of many-body systems. In particular, it had a major impact on developments in nuclear [1] and molecular [2] physics and made significant contributions to virtually all areas of many-body physics [3]. Its basic paradigm is to write the Hamiltonian of the system under consideration in terms of Casimir operators of a set of nested algebras. Its hallmarks are (i) solvability of the complete spectrum, (ii) existence of exact quantum numbers for all eigenstates, and (iii) pre-determined symmetry-based structure of the eigenfunctions, independent of the Hamiltonian's parameters.The merits of a DS are self-evident. However, in most applications to realistic systems, the predictions of an exact DS are rarely fulfilled and one is compelled to break it. More often one finds that the assumed symmetry is not obeyed uniformly, i.e., is fulfilled by only some states but not by others. The need to address such situations has led to the introduction of partial dynamical symmetries (PDSs). The essential idea is to relax the stringent conditions of complete solvability so that the properties (i)-(iii) are only partially satisfied. Partiality comes in three different guises: (a) part of the eigenspectrum retains all the DS quantum numbers [4,5], (b) the entire eigenspectrum retains part of the DS quantum numbers [6,7], and (c) part of the eigenspectrum retains part of the DS quantum numbers [8]. PDS of various types have been shown to be relevant to nuclear [5,6,7,8,9] and molecular [10] spectroscopy, to systems with mixed chaotic and regular dynamics [11] and to quantum phase transitions [12].We emphasize that DS as well as its generalization PDS are notions that are not restricted to a specific model but can be applied to any quantal system of interacting particles, bosons and fermions. In this Letter we propose a generic method to construct quantum Hamiltonians with PDS of type (a) and show that its existence is closely related to the order of the interaction among the particles. The procedure is discussed in general terms and subsequently illustrated with a nuclear-physics example with an application to the nucleus 196 Pt.The analysis starts from the chain of nested algebras
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