67 research outputs found
Rotationally Invariant Hamiltonians for Nuclear Spectra Based on Quantum Algebras
The rotational invariance under the usual physical angular momentum of the
SUq(2) Hamiltonian for the description of rotational nuclear spectra is
explicitly proved and a connection of this Hamiltonian to the formalisms of
Amal'sky and Harris is provided. In addition, a new Hamiltonian for rotational
spectra is introduced, based on the construction of irreducible tensor
operators (ITO) under SUq(2) and use of q-deformed tensor products and
q-deformed Clebsch-Gordan coefficients. The rotational invariance of this
SUq(2) ITO Hamiltonian under the usual physical angular momentum is explicitly
proved, a simple closed expression for its energy spectrum (the ``hyperbolic
tangent formula'') is introduced, and its connection to the Harris formalism is
established. Numerical tests in a series of Th isotopes are provided.Comment: 34 pages, LaTe
Skyrme mean-field study of rotational bands in transfermium isotopes
Self-consistent mean field calculations with the SLy4 interaction and a
density-dependent pairing force are presented for nuclei in the Nobelium mass
region. Predicted quasi-particle spectra are compared with experiment for the
heaviest known odd N and odd Z nuclei. Spectra and rotational bands are
presented for nuclei around No252,4 for which experiments are either planned or
already running.Comment: 13 pages LATEX, elsart style, 6 embedded eps figure
Studies of the electric dipole transitions of deformed rare-earth nuclei
Spectrum and electric dipole transition rates and relative intensities in
Sm, Gd, Dy are studied in the framework of
the interacting boson model with s,p,d,f bosons. It is found that E1 transition
data among the low-lying levels are in good agreement with the SU(3) dynamical
symmetry of the spdf interacting boson model proposed by Engel and Iachello to
describe collective rotation with octupole vibration. These results show that
these nuclei have SU(3) dynamic symmetry to a good approximation. Also in this
work many algebraic expressions for electric dipole transitions in the SU(3)
limit of the spdf-IBM have been obtained. These formulae together with the
formulae given previously exhaust nearly all the E1 transitions for low-lying
negative parity states. They are useful in analyzing experimental data.Comment: 26 pages, 1 figur
Analytical description of the Coherent State Model for near vibrational and well deformed nuclei
Analytical formulas for the excitation energies as well as for the electric
quadrupole reduced transition probabilities in the ground, beta and gamma bands
were derived within the coherent state model for the near vibrational and well
deformed nuclei. Numerical calculations were performed for 42 nuclei exhibiting
various symmetries and therefore with specific properties. Comparison of the
calculation results with the corresponding experimental data shows a good
agreement. The parameters involved in the proposed model satisfy evident
regularities being interpolated by smooth curves. Few of them, which fall out
of the curves, are interpreted as signatures for a critical point in a specific
phase transition. This is actually supported also by the figures showing the
excitation energy dependence on the angular momentum. The formulas provided for
energies and B(E2) values are very simple, being written in a compact form, and
therefore easy to be handled to explain the new experimental data.Comment: 9 figures, 50 page
First decay study of the very neutron-rich isotope Br-93
The decay of the mass-separated, very neutron-rich isotope Br-93 has been
studied by gamma-spectroscopy. A level scheme of its daughter Kr-93 has been
constructed. Level energies, gamma-ray branching ratios and multipolarities
suggest spins and parities which are in accord with a smooth systematics of the
N=57 isotones for Z less-equal 40, suggesting the N=56 shell closure still to
be effective in Kr isotopes. So far, there is no indication of a progressive
onset of deformation in neutron-rich Kr isotopes.Comment: 17 pages, 3 figures, Phys. Rev. C, in prin
X(3): An Exactly Separable Gamma-Rigid Version of the X(5) Critical Point Symmetry
A gamma-rigid version (with gamma=0) of the X(5) critical point symmetry is
constructed. The model, to be called X(3) since it is proved to contain three
degrees of freedom, utilizes an infinite well potential, is based on exact
separation of variables, and leads to parameter free (up to overall scale
factors) predictions for spectra and B(E2) transition rates, which are in good
agreement with existing experimental data for 172-Os and 186-Pt. An unexpected
similarity of the first beta bands of the X(5) nuclei 150-Nd, 152-Sm, 154-Gd,
and 156-Dy to the X(3) predictions is observed.Comment: LaTeX, 12 pagres, including 4 postscript figure
Ground- band coupling in heavy deformed nuclei and SU(3) contraction limit
We derive analytic expressions for the energies and -transition
probabilities in the states of the ground and bands of heavy deformed
nuclei within a collective Vector-Boson Model with SU(3) dynamical symmetry. On
this basis we examine the analytic behavior of the SU(3) energy splitting and
the B(E2) interband transition ratios in the SU(3) contraction limits of the
model. The theoretical analyses outline physically reasonable ways in which the
ground- band coupling vanishes. The experimental data on the lowest
collective states of even-even rare earth nuclei and actinides strongly support
the theoretical results. They suggest that a transition from the
ground- band coupling scheme to a scheme in which the ground band is
situated in a separate irreducible representation of SU(3) should be realized
towards the midshell regions. We propose that generally the SU(3) group
contraction process should play an important role for such a kind of
transitions in any collective band coupling scheme in heavy deformed nuclei.Comment: 24 pages (LaTeX), 7 figures (12 postscript files
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