18,632 research outputs found
Shell-model studies on exotic nuclei around 132Sn
The study of exotic nuclei around 132Sn is a subject of current experimental
and theoretical interest. Experimental information for nuclei in the vicinity
of 132Sn, which have been long inaccessible to spectroscopic studies, is now
available thanks to new advanced facilities and techniques. The experimental
data which have been now become available for these neutron-rich nuclei may
suggest a modification in the shell structure. They are, in fact, somewhat
different from what one might expect by extrapolating the existing results for
N<82, and as a possible explanation a change in the single-proton level scheme
has been suggested. The latter would be caused by a more diffuse nuclear
surface, and could be seen as a precursor of major effects which should show up
at larger neutron excess. New data offer therefore the opportunity to test the
shell model and look for a possible evolution of shell structure when going
toward neutron drip line. This is stimulating shell-model studies in this
region. Here, we present an overview of recent shell-model studies of 132Sn
neighbors, focusing attention on those calculations employing realistic
effective interactions.Comment: 8 pages, 4 tables, invited talk at INPC2007, Tokyo, Japan, June 3-8
2007. To be published in Nuclear Physics
Shell-model study of quadrupole collectivity in light tin isotopes
A realistic shell-model study is performed for neutron-deficient tin isotopes
up to mass A=108. All shell-model ingredients, namely two-body matrix elements,
single-particle energies, and effective charges for electric quadrupole
transition operators, have been calculated by way of the many-body perturbation
theory, starting from a low-momentum interaction derived from the
high-precision CD-Bonn free nucleon-nucleon potential. The focus has been put
on the enhanced quadrupole collectivity of these nuclei, which is testified by
the observed large B(E2;0+ -> 2+)s. Our results evidence the crucial role
played by the Z=50 cross-shell excitations that need to be taken into account
explicitly to obtain a satisfactory theoretical description of light tin
isotopes. We find also that a relevant contribution comes from the calculated
neutron effective charges, whose magnitudes exceed the standard empirical
values. An original double-step procedure has been introduced to reduce
effectively the model space in order to overcome the computational problem.Comment: 6 pages, 6 figures, 2 table
Low-momentum Nucleon-Nucleon Potential and Hartree-Fock Calculations
A low-momentum nucleon-nucleon (NN) potential V-low-k is derived from modern
realistic NN potentials by integrating out the high-momentum modes. The smooth
V-low-k may be used as input for nuclear structure calculations instead of the
usual Brueckner G matrix. Such an approach eliminates the energy dependence one
finds in the G-matrix approach, allowing this interaction to be used directly
in Hartree-Fock calculations. Bulk properties of 16O have been calculated
starting from different NN potentials. Our results, obtained including up to
second order contributions in the Goldstone expansion, are in good agreement
with experiment.Comment: 7 pages, talk presented at IX Convegno su Problemi di Fisica Nucleare
Teorica, Cortona (Italy), October 9-12 200
Shell-Model Calculations with Realistic Effective Interactions
In this paper, we present some results of shell-model calculations employing
effective interactions derived from the CD-Bonn free nucleon-nucleon potential.
These concern 18O, 134Te, and 210Po, and are part of a comprehensive study of
nuclei around doubly closed shells. Comparison of the calculated results with
experimental data illustrates the degree of accuracy of modern realistic
shell-model calculations.Comment: Talk presented at INPC 2001, 29 July - 3 August 2001, Berkeley (USA
p-Shell Nuclei and Two-Frequency Shell Model with a Realistic Effective Interaction
We have studied p-shell nuclei using a two-frequency shell-model approach
with an effective interaction derived from the Bonn-A nucleon-nucleon potential
by means of a G-matrix folded-diagram method. First, we briefly describe our
derivation of the effective interaction in a model space composed of harmonic
hoscillator wave functions with two different length parameters, b_in and
b_out, for the core and the valence orbits, respectively. Then we present some
selected results of our calculations. We show that a good agreement with
experiment is obtained, which is definitely better than that provided by a
standard one-frequency calculation. A comparison with results obtained from
large-basis shell-model calculations is also made.Comment: 9 pages, 1 figure, talk presented at VIII Convegno di Fisica Nucleare
Teorica, Cortona, 18-21 Ottobre 200
Shell-model study of the N=82 isotonic chain with a realistic effective hamiltonian
We have performed shell-model calculations for the even- and odd-mass N=82
isotones, focusing attention on low-energy states. The single-particle energies
and effective two-body interaction have been both determined within the
framework of the time-dependent degenerate linked-diagram perturbation theory,
starting from a low-momentum interaction derived from the CD-Bonn
nucleon-nucleon potential. In this way, no phenomenological input enters our
effective Hamiltonian, whose reliability is evidenced by the good agreement
between theory and experiment.Comment: 7 pages, 11 figures, 3 tables, to be published in Physical Review
Low-momentum nucleon-nucleon interaction and shell-model calculations
We discuss the use of the low-momentum nucleon-nucleon NN interaction V-low-k
in the derivation of the shell-model effective interaction and emphasize its
practical value as an alternative to the Brueckner G-matrix method. We present
some selected results of our current study of exotic nuclei around closed
shells, which have been obtained starting from the CD-Bonn potential. We also
show some results of calculations performed with different phase-shift
equivalent NN potentials, and discuss the effect of changes in the cutoff
momentum which defines the V-low-k potential.Comment: 5 pages, 5 figures, 1 table, Talk presented at CDN05, 31 Jan - 4 Feb
2005, University of Tokyo, Japa
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