827 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
Mixed Representation RPA Calculation for Octupole Excitations on Superdeformed Sates in the 40Ca and Neutron-Rich Sulfur Regions
By means of the mixed representation RPA based on the Skyrme-Hartree-Fock
mean field, we investigate low-frequency octupole excitations built on the
superdeformed (SD) states in the N=Z nuclei around 40Ca and the neutron-rich
Sulfur isotopes. The RPA calculation is carried out fully self-consistently on
the three-dimensional Cartesian mesh in a box, and yields a number of
low-frequency octupole vibrations built on the SD states in 32S, 36Ar, 40Ca and
44Ti. In particular, a strongly collective K^\pi=1^- octupole vibration is
suggested to appear on top of the SD state in 40Ca. For 48,50S close to the
neutron drip line, we find that the low-lying state created by the excitation
of a single neutron from a loosely bound low Omega level to a high Omega
resonance level acquires an extremely strong octupole transition strength due
to the spatially very extended structure of the particle-hole wave functions.Comment: 22 pages, 7 figure
Photoemission and x-ray absorption studies of valence states in (Ni,Zn,Fe,Ti)O thin films exhibiting photo-induced magnetization
By means of photoemission and x-ray absorption spectroscopy, we have studied
the electronic structure of (Ni,Zn,Fe,Ti)O thin films, which
exhibits a cluster glass behavior with a spin-freezing temperature of
K and photo-induced magnetization (PIM) below . The Ni and Zn
ions were found to be in the divalent states. Most of the Fe and Ti ions in the
thin films were trivalent (Fe) and tetravalent (Ti),
respectively. While Ti doping did not affect the valence states of the Ni and
Zn ions, a small amount of Fe ions increased with Ti concentration,
consistent with the proposed charge-transfer mechanism of PIM.Comment: 4 pages, 4 figure
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