126 research outputs found
Shape-phase transitions in odd-mass -soft nuclei with mass
Quantum phase transitions between competing equilibrium shapes of nuclei with
an odd number of nucleons are explored using a microscopic framework of nuclear
energy density functionals and a particle-boson core coupling model. The boson
Hamiltonian for the even-even core nucleus, as well as the spherical
single-particle energies and occupation probabilities of unpaired nucleons, are
completely determined by a constrained self-consistent mean-field calculation
for a specific choice of the energy density functional and pairing interaction.
Only the strength parameters of the particle-core coupling have to be adjusted
to reproduce a few empirical low-energy spectroscopic properties of the
corresponding odd-mass system. The model is applied to the odd-A Ba, Xe, La and
Cs isotopes with mass , for which the corresponding even-even Ba
and Xe nuclei present a typical case of -soft nuclear potential. The
theoretical results reproduce the experimental low-energy excitation spectra
and electromagnetic properties, and confirm that a phase transition between
nearly spherical and -soft nuclear shapes occurs also in the odd-A
systems.Comment: 13 pages, 15 figures, 9 table
Signatures of shape phase transitions in odd-mass nuclei
Quantum phase transitions between competing ground-state shapes of atomic
nuclei with an odd number of protons or neutrons are investigated in a
microscopic framework based on nuclear energy density functional theory and the
particle-plus-boson-core coupling scheme. The boson-core Hamiltonian, as well
as the single-particle energies and occupation probabilities of the unpaired
nucleon, are completely determined by constrained self-consistent mean-field
calculations for a specific choice of the energy density functional and paring
interaction, and only the strength parameters of the particle-core coupling are
adjusted to reproduce selected spectroscopic properties of the odd-mass system.
We apply this method to odd-A Eu and Sm isotopes with neutron number , and explore the influence of the single unpaired fermion on the occurrence
of a shape phase transition. Collective wave functions of low-energy states are
used to compute quantities that can be related to quantum order parameters:
deformations, excitation energies, E2 transition rates and separation energies,
and their evolution with the control parameter (neutron number) is analysed.Comment: 15 pages, 13 figures; Accepted for publication in Phys. Rev.
Random-phase approximation based on relativistic point-coupling models
The matrix equations of the random-phase approximation (RPA) are derived for
the point-coupling Lagrangian of the relativistic mean-field (RMF) model. Fully
consistent RMF plus (quasiparticle) RPA illustrative calculations of the
isoscalar monopole, isovector dipole and isoscalar quadrupole response of
spherical medium-heavy and heavy nuclei, test the phenomenological effective
interactions of the point-coupling RMF model. A comparison with experiment
shows that the best point-coupling effective interactions accurately reproduce
not only ground-state properties, but also data on excitation energies of giant
resonances.Comment: 24 pages, 4 figures, accepted for publication in Physical Review
Quadrupole Collective Dynamics from Energy Density Functionals: Collective Hamiltonian and the Interacting Boson Model
Microscopic energy density functionals (EDF) have become a standard tool for
nuclear structure calculations, providing an accurate global description of
nuclear ground states and collective excitations. For spectroscopic
applications this framework has to be extended to account for collective
correlations related to restoration of symmetries broken by the static mean
field, and for fluctuations of collective variables. In this work we compare
two approaches to five-dimensional quadrupole dynamics: the collective
Hamiltonian for quadrupole vibrations and rotations, and the Interacting Boson
Model. The two models are compared in a study of the evolution of non-axial
shapes in Pt isotopes. Starting from the binding energy surfaces of
Pt, calculated with a microscopic energy density functional, we
analyze the resulting low-energy collective spectra obtained from the
collective Hamiltonian, and the corresponding IBM-2 Hamiltonian. The calculated
excitation spectra and transition probabilities for the ground-state bands and
the -vibration bands are compared to the corresponding sequences of
experimental states.Comment: 10 pages, 4 figures; to be published in Phys. Rev.
Relativistic Nuclear Energy Density Functionals: Mean-Field and Beyond
Relativistic energy density functionals (EDF) have become a standard tool for
nuclear structure calculations, providing a complete and accurate, global
description of nuclear ground states and collective excitations. Guided by the
medium dependence of the microscopic nucleon self-energies in nuclear matter,
semi-empirical functionals have been adjusted to the nuclear matter equation of
state and to bulk properties of finite nuclei, and applied to studies of
arbitrarily heavy nuclei, exotic nuclei far from stability, and even systems at
the nucleon drip-lines. REDF-based structure models have also been developed
that go beyond the static mean-field approximation, and include collective
correlations related to the restoration of broken symmetries and to
fluctuations of collective variables. These models are employed in analyses of
structure phenomena related to shell evolution, including detailed predictions
of excitation spectra and electromagnetic transition rates.Comment: To be published in Progress in Particle and Nuclear Physic
Relativistic Energy Density Functional Description of Shape Transition in Superheavy Nuclei
Relativistic energy density functionals (REDF) provide a complete and
accurate, global description of nuclear structure phenomena. A modern
semi-empirical functional, adjusted to the nuclear matter equation of state and
to empirical masses of deformed nuclei, is applied to studies of shapes of
superheavy nuclei. The theoretical framework is tested in a comparison of
calculated masses, quadrupole deformations, and potential energy barriers to
available data on actinide isotopes. Self-consistent mean-field calculations
predict a variety of spherical, axial and triaxial shapes of long-lived
superheavy nuclei, and their alpha-decay energies and half-lives are compared
to data. A microscopic, REDF-based, quadrupole collective Hamiltonian model is
used to study the effect of explicit treatment of collective correlations in
the calculation of Q{\alpha} values and half-lives.Comment: 23 pages, 10 figure
Relativistic Nuclear Energy Density Functionals: adjusting parameters to binding energies
We study a particular class of relativistic nuclear energy density
functionals in which only nucleon degrees of freedom are explicitly used in the
construction of effective interaction terms. Short-distance (high-momentum)
correlations, as well as intermediate and long-range dynamics, are encoded in
the medium (nucleon density) dependence of the strength functionals of an
effective interaction Lagrangian. Guided by the density dependence of
microscopic nucleon self-energies in nuclear matter, a phenomenological ansatz
for the density-dependent coupling functionals is accurately determined in
self-consistent mean-field calculations of binding energies of a large set of
axially deformed nuclei. The relationship between the nuclear matter volume,
surface and symmetry energies, and the corresponding predictions for nuclear
masses is analyzed in detail. The resulting best-fit parametrization of the
nuclear energy density functional is further tested in calculations of
properties of spherical and deformed medium-heavy and heavy nuclei, including
binding energies, charge radii, deformation parameters, neutron skin thickness,
and excitation energies of giant multipole resonances.Comment: 53 pages, 23 figures, accepted for publication in Physical Review
-decay half-lives of neutron-rich nuclei and matter flow in the -process
The -decay half-lives of neutron-rich nuclei with are systematically investigated using the newly developed fully
self-consistent proton-neutron quasiparticle random phase approximation (QRPA),
based on the spherical relativistic Hartree-Fock-Bogoliubov (RHFB) framework.
Available data are reproduced by including an isospin-dependent proton-neutron
pairing interaction in the isoscalar channel of the RHFB+QRPA model. With the
calculated -decay half-lives of neutron-rich nuclei a remarkable
speeding up of -matter flow is predicted. This leads to enhanced -process
abundances of elements with , an important result for the
understanding of the origin of heavy elements in the universe.Comment: 14 pages, 4 figure
Superallowed Fermi transitions in RPA with a relativistic point-coupling energy functional
The self-consistent random phase approximation (RPA) approach with the
residual interaction derived from a relativistic point-coupling energy
functional is applied to evaluate the isospin symmetry-breaking corrections
{\delta}c for the 0+\to0+ superallowed Fermi transitions. With these {\delta}c
values, together with the available experimental ft values and the improved
radiative corrections, the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM)
matrix is examined. Even with the consideration of uncertainty, the sum of
squared top-row elements has been shown to deviate from the unitarity condition
by 0.1% for all the employed relativistic energy functionals.Comment: 13 pages,2 figure
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