1,037 research outputs found
Pairing effects on the collectivity of quadrupole states around 32Mg
The first 2+ states in N=20 isotones including neutron-rich nuclei 32Mg and
30Ne are studied by the Hartree-Fock-Bogoliubov plus quasiparticle random phase
approximation method based on the Green's function approach. The residual
interaction between the quasiparticles is consistently derived from the
hamiltonian density of Skyrme interactions with explicit velocity dependence.
The B(E2) transition probabilities and the excitation energies of the first 2+
states are well described within a single framework. We conclude that pairing
effects account largely for the anomalously large B(E2) value and the very low
excitation energy in 32Mg.Comment: 14 pages, 9 figure
Mean-field approach to superdeformed high-spin states in 40Ca and neutron-rich 50S regions
With the use of the symmetry-unrestricted cranked SHF method in the 3D
coordinate-mesh representation, a systematic search for the SD and HD
rotational bands in the N=Z nuclei from 32S to 48Cr has been done, and SD and
HD solutions have been found in 32S, 36Ar, 40Ca, 44Ti, and in 36Ar, 40Ca, 44Ti,
48Cr, respectively. The SD band in 40Ca is found to be extremely soft against
both the axially symmetric (Y30) and asymmetric (Y31) octupole deformations.
Possible presense of SD states in neutron-rich sulfur isotopes from 46S to 52S
has also been investigated, and deformation properties of neutron skins both in
the ground and SD states are discussed.Comment: 10 pages including 9 ps figures, Talk at International Symposium on
"Frontiers of Collective Motion 2002", November 6-9, 2002, Univ. of Aizu,
Japa
Nuclear Tetrahedral Symmetry: Possibly Present Throughout the Periodic Table
More than half a century after the fundamental, spherical shell structure in
nuclei has been established, theoretical predictions indicate that the
shell-gaps comparable or even stronger than those at spherical shapes may
exist. Group-theoretical analysis supported by realistic mean-field
calculations indicate that the corresponding nuclei are characterized by the
('double-tetrahedral') group of symmetry, exact or approximate. The
corresponding strong shell-gap structure is markedly enhanced by the existence
of the 4-dimensional irreducible representations of the group in question and
consequently it can be seen as a geometrical effect that does not depend on a
particular realization of the mean-field. Possibilities of discovering the
corresponding symmetry in experiment are discussed.Comment: 4 pages in LaTeX and 4 figures in eps forma
Superdeformed bands in neutron-rich Sulfur isotopes suggested by cranked Skyrme-Hartree-Fock calculations
On the basis of the cranked Skyrme-Hartree-Fock calculations in the
three-dimensional coordinate-mesh representation, we suggest that, in addition
to the well-known candidate 32S, the neutron-rich nucleus 36S and the drip-line
nuclei,48S and 50S, are also good candidates for finding superdeformed
rotational bands in Sulfur isotopes. Calculated density distributions for the
superdeformed states in 48S and 50S exhibit superdeformed neutron skinsComment: 18 pages including 10 ps figure
Lymph node removal enhances corneal graft survival in mice at high risk of rejection
Peer reviewedPublisher PD
Pairing and continuum effects on low-frequency quadrupole vibrations in deformed Mg isotopes close to the neutron drip line
Low-frequency quadrupole vibrational modes in deformed Mg close
to the neutron drip line are studied by means of the quasiparticle-random-phase
approximation based on the coordinate-space Hartree-Fock-Bogoliubov formalism.
Strongly collective and excitation modes carrying 10-20
Weisskopf units in the intrinsic isoscalar quadrupole transition strengths are
obtained at about 3 MeV. There are two reasons for the enhancement of the
transition strengths. First, the quasiparticle wave functions generating these
modes possess spatially very extended structure. The asymptotic selection rules
characterizing the and vibrations in stable deformed nuclei
are thus strongly violated. Second, the dynamic pairing effects act strongly to
enhance the collectivity of these modes. It is suggested that the lowest
collective mode is a particularly sensitive indicator of the
nature of pairing correlations in deformed nuclei close to the neutron drip
line.Comment: 23 pages including 11 figures and 8 tables. Submitted to NP
Clustering in stable and unstable nuclei in -shell and -shell regions
According to microscopic calculations with antisymmetrized molecular
dynamics, we studied cluster features in stable and unstable nuclei. A variety
of structure was found in stable and unstable nuclei in the -shell and
-shell regions. The structure of excited states of Be was
investigated, while in -shell nuclei we focused on molecular states and
deformed states. The deformed states in Si and Ca were discussed
in connection with the high-lying molecular states. Appealing molecular states
in Ar and Mg were suggested. The results signified that both
clustering of nucleons and mean-field formation are essential features in
-shell nuclei as well as -shell nuclei.Comment: 5 pages, 2 figs, proceedings of the 8th International conference on
Clustering Aspects of Nuclear Structure and Dynamics, Nov. 2003, Nara, Japan,
to be published in Nucl.Phys.
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