192 research outputs found
A microscopic study of the proton-neutron symmetry and phonon structure of the low-lying states in 92Zr
We studied in a microscopic multiphonon approach the proton-neutron symmetry
and phonon structure of some low-lying states recently discovered in 92Zr. We
confirm the breaking of F-spin symmetry, but argue that the breaking mechanism
is more complex than the one suggested in the original shell model analysis of
the data. We found other new intriguing features of the spectrum, like a
pronounced multiphonon fragmentation of the states and a tentative evidence of
a three-phonon mixed symmetry state.Comment: 13 pages, to appear in Phys. Rev.
An application of the 3-dimensional q-deformed harmonic oscillator to the nuclear shell model
An analysis of the construction of a q-deformed version of the 3-dimensional
harmonic oscillator, which is based on the application of q-deformed algebras,
is presented. The results together with their applicability to the shell model
are compared with the predictions of the modified harmonic oscillator.Comment: 12 pages, LaTe
Orbital Magnetic Dipole Mode in Deformed Clusters: A Fully Microscopic Analysis
The orbital M1 collective mode predicted for deformed clusters in a schematic
model is studied in a self-consistent random-phase-approximation approach which
fully exploits the shell structure of the clusters. The microscopic mechanism
of the excitation is clarified and the close correlation with E2 mode
established. The study shows that the M1 strength of the mode is fragmented
over a large energy interval. In spite of that, the fraction remaining at low
energy, well below the overwhelming dipole plasmon resonance, is comparable to
the strength predicted in the schematic model. The importance of this result in
view of future experiments is stressed.Comment: 10 pages, 3 Postscript figures, uses revte
Simplified boson realization of the subalgebra of and matrix elements of quadrupole operators
A simplified boson realization of the subalgebra of is
constructed. A simplified form of the corresponding basis states is
obtained. The reduced matrix elements of a special second-rank tensor operator
(quadrupole operator) are calculated in the basis.Comment: 13 pages, LaTeX. Uses ioplppt.sty, iopl12.st
Toroidal, compression, and vortical dipole strengths in Sm: Skyrme-RPA exploration of deformation effect
A comparative analysis of toroidal, compressional and vortical dipole
strengths in the spherical Sm and the deformed Sm is performed
within the random-phase-approximation using a set of different Skyrme forces.
Isoscalar (T=0), isovector (T=1), and electromagnetic excitation channels are
considered. The role of the nuclear convection and
magnetization currents is inspected. It is shown that the
deformation leads to an appreciable redistribution of the strengths and causes
a spectacular deformation splitting (exceeding 5 MeV) of the isoscalar
compressional mode. In Sm, the =0 and =1 branches of the mode
form well separated resonances. When stepping from Sm to Sm, we
observe an increase of the toroidal, compression and vortical contributions in
the low-energy region (often called pygmy resonance). The strength in this
region seems to be an overlap of various excitation modes. The energy centroids
of the strengths depend significantly on the isoscalar effective mass .
Skyrme forces with a large (typically ) seem to be
more suitable for description of experimental data for the isoscalar giant
dipole resonance.Comment: 13 pages, 10 figures, submitted to EJP
Large scale shell model calculations for the yrast line of 138Xe
We have adopted an importance sampling iterative matrix diagonalization algorithm to compute a large scale shell model calculation of the yrast spectrum of 138Xe up to high spin thereby extending a previous calculation confined to low-lying angular momenta. An effective nucleon–nucleon interaction derived from the CD-Bonn nucleon-nucleon potential is used to compute energies, E2 transition probabilities, and occupation numbers. A satisfactory agreement with the experimental data is reached
Orbital magnetism in axially deformed sodium clusters: From scissors mode to dia-para magnetic anisotropy
Low-energy orbital magnetic dipole excitations, known as scissors mode (SM),
are studied in alkali metal clusters. Subsequent dynamic and static effects are
explored. The treatment is based on a self-consistent microscopic approach
using the jellium approximation for the ionic background and the Kohn-Sham mean
field for the electrons. The microscopic origin of SM and its main features
(structure of the mode in light and medium clusters, separation into low- and
high-energy plasmons, coupling high-energy M1 scissors and E2 quadrupole
plasmons, contributions of shape isomers, etc) are discussed. The scissors M1
strength acquires large values with increasing cluster size. The mode is
responsible for the van Vleck paramagnetism of spin-saturated clusters. Quantum
shell effects induce a fragile interplay between Langevin diamagnetism and van
Vleck paramagnetism and lead to a remarkable dia-para anisotropy in magnetic
susceptibility of particular light clusters. Finally, several routes for
observing the SM experimentally are discussed.Comment: 21 pages, 7 figure
Temperature Dependence of Damping and Frequency Shifts of the Scissors Mode of a trapped Bose-Einstein Condensate
We have studied the properties of the scissors mode of a trapped
Bose-Einstein condensate of Rb atoms at finite temperature. We measured
a significant shift in the frequency of the mode below the hydrodynamic limit
and a strong dependence of the damping rate as the temperature increased. We
compared our damping rate results to recent theoretical calculations for other
observed collective modes finding a fair agreement. From the frequency
measurements we deduce the moment of inertia of the gas and show that it is
quenched below the transition point, because of the superfluid nature of the
condensed gas.Comment: 5 pages, 4 figure
Removal of the center of mass in nuclei and its effects on 4He
Abstract The singular value decomposition of rectangular matrices is shown to provide the recipe for removing the center of mass spurious admixtures from the multiphonon basis generated by an equation of motion method for solving the nuclear eigenvalue problem. It works for any single particle basis without any energy restriction on the selection of the configurations. Its effects on 4He are illustrated
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