53 research outputs found
Construction of SU(3) irreps in canonical SO(3)-coupled bases
Alternative canonical methods for defining canonical SO(3)-coupled bases for
SU(3) irreps are considered and compared. It is shown that a basis that
diagonalizes a particular linear combination of SO(3) invariants in the SU(3)
universal enveloping algebra gives basis states that have good quantum
numbers in the asymptotic rotor-model limit.Comment: no figure
Macroscopic and microscopic description of phase transition in cerium isotopes
The spherical-to-deformed phase transition in cerium isotopes recently suggested to occur between Ce146 and Ce148 has been examined in the framework of the macroscopic algebraic collective model and two microscopic approaches, namely Skyrme-Hartree-Fock + Bardeen-Cooper-Schrieffer (BCS) calculations and the symmetry conserving configuration mixing method with Gogny energy density functionals applied also to the neighboring nuclei along the cerium isotopic chain. Possible spectral signatures of the phase transition are discussed in more details. The microscopic calculations predict octupole softness manifested by rather flat potential energy curves as a function of the octupole deformation parameter β3 for Ce146 and Ce148 and shape coexistence characterized by axially symmetric 0+ states, triaxial 2+ bands, and octupole deformation for the lowest 1- state
New features of the triaxial nuclei described with a coherent state model
Supplementing the Liquid Drop Model (LDM) Hamiltonian, written in the
intrinsic reference frame, with a sextic oscillator plus a centrifugal term in
the variable and a potential in with a minimum in
, the Sch\"{o}dinger equation is separated for the two variables
which results in having a new description for the triaxial nuclei, called
Sextic and Mathieu Approach (SMA). SMA is applied for two non-axial nuclei,
Hf and W and results are compared with those yielded by the
Coherent State Model (CSM). As the main result of this paper we derive
analytically the equations characterizing SMA from a semi-classical treatment
of the CSM Hamiltonian. In this manner the potentials in and
variables respectively, show up in a quite natural way which contrasts their
ad-hoc choice when SMA emerges from LDM.Comment: 13 figures, 13 page
Shape evolution in 116,118 Ru: Triaxiality and transition between the O(6) and U(5) dynamical symmetries
116Ru and 118Ru have been studied via β-delayed γ-ray spectroscopy of nuclei produced in fragmentation reactions at the Radioactive Ion-Beam Factory (RIBF) facility. Level schemes with positive-parity states up to spin J=6 have been constructed. The re
Intruder bands and configuration mixing in the lead isotopes
A three-configuration mixing calculation is performed in the context of the
interacting boson model with the aim to describe recently observed collective
bands built on low-lying states in neutron-deficient lead isotopes. The
configurations that are included correspond to the regular, spherical states as
well as two-particle two-hole and four-particle four-hole excitations across
the Z=82 shell gap.Comment: 20 pages, 4 figures, accepted by PRC, reference added for section 1
in this revised versio
Study of Na at SPIRAL
NESTERInternational audienceThe excitation function for the elastic-scattering reaction p18Ne, p18Ne was measured with the first radioactive beam from the SPIRAL facility at the GANIL laboratory and with a solid cryogenic hydrogen target. Several broad resonances have been observed, corresponding to new excited states in the unbound nucleus 19Na. In addition, two-proton emission events have been identified and are discussed
Half-life of the 15/2(+) state of I-135: A test of E2 seniority relations
International audienceThe half-life of the 15/2+1 state of the 3-valence-proton nucleus 135I has been measured to be 1.74(8) ns using the EXILL-FATIMA mixed array of Ge and LaBr3 detectors. The nuclei were produced following the cold neutron-induced fission of a 235U target at the PF1B beam line of the Institut Laue-Langevin. The extracted B(E2;15/2+→11/2+) value enabled a test of seniority relations for the first time between E2 transition rates. Large-scale shell-model calculations were performed for 134Te and 135I, and reinterpreted in a single-orbit approach. The results show that the two-body component of the E2 operator can be large whereas energy shifts due to the three-body component of the effective interaction are small
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