294 research outputs found
Descritpion of Exotic Nuclei Using Continuum Shell Model
In weakly bound exotic nuclei, number of excited bound states or narrow
resonances is small and, moreover, they couple strongly to the particle
continuum. Hence, these systems should be described in the quantum open system
formalism which does not artificially separate the subspaces of (quasi-) bound
and scattering states. The Shell Model Embedded in the Continuum provides a
novel approach which solves this problem. Examples of application in sd-shell
nuclei will be presented.Comment: Presented at the NATO Advanced Research Workshop Brijuni, Pula,
Croatia, June 2-5, 200
Results from Shell Model Monte Carlo Studies
We review results obtained using Shell Model Monte Carlo (SMMC) techniques.
These methods reduce the imaginary-time many-body evolution operator to a
coherent superposition of one-body evolutions in fluctuating one-body fields;
the resultant path integral is evaluated stochastically. After a brief review
of the methods, we discuss a variety of nuclear physics applications. These
include studies of the ground-state properties of pf-shell nuclei, Gamow-Teller
strength distributions, thermal and rotational pairing properties of nuclei
near N=Z, -soft nuclei, and -decay in ^{76}Ge. Several
other illustrative calculations are also reviewed. Finally, we discuss
prospects for further progress in SMMC and related calculations
Time-odd triaxial relativistic mean field approach for nuclear magnetic moments
The time-odd triaxial relativistic mean field approach is developed and
applied to the investigation of the ground-state properties of light odd-mass
nuclei near the double-closed shells. The nuclear magnetic moments including
the isoscalar and isovector ones are calculated and good agreement with Schmidt
values is obtained. Taking F as an example, the splitting of the single
particle levels (around MeV near the Fermi level), the nuclear current,
the core polarizations, and the nuclear magnetic potential, i.e., the spatial
part of the vector potential, due to the violation of the time reversal
invariance are investigated in detail.Comment: 26 pages, 8 figures. PHYSICAL REVIEW C (accepted
Beta-decay properties of Si and P
The -decay properties of the neutron-deficient nuclei Si and
P have been investigated at the GANIL/LISE3 facility by means of
charged-particle and -ray spectroscopy. The decay schemes obtained and
the Gamow-Teller strength distributions are compared to shell-model
calculations based on the USD interaction. B(GT) values derived from the
absolute measurement of the -decay branching ratios give rise to a
quenching factor of the Gamow-Teller strength of 0.6. A precise half-life of
43.7 (6) ms was determined for P, the - (2)p decay mode of which
is described
On the Strength of Spin-Isospin Transitions in A=28 Nuclei
The relations between the strengths of spin-isospin transition operators
extracted from direct nuclear reactions, magnetic scattering of electrons and
processes of semi-leptonic weak interactions are discussed.Comment: LaTeX, 8 pages, 1Postscript with figur
Muon capture on nuclei with N > Z, random phase approximation, and in-medium renormalization of the axial-vector coupling constant
We use the random phase approximation to describe the muon capture rate on
Ca,Ca, Fe, Zr, and Pb. With
Ca as a test case, we show that the Continuum Random Phase
Approximation (CRPA) and the standard RPA give essentially equivalent
descriptions of the muon capture process. Using the standard RPA with the free
nucleon weak form factors we reproduce the experimental total capture rates on
these nuclei quite well. Confirming our previous CRPA result for the
nuclei, we find that the calculated rates would be significantly lower than the
data if the in-medium quenching of the axial-vector coupling constant were
employed.Comment: submitted to Phys. Rev.
RPA vs. exact shell-model correlation energies
The random phase approximation (RPA) builds in correlations left out by
mean-field theory. In full 0-hbar-omega shell-model spaces we calculate the
Hartree-Fock + RPA binding energy, and compare it to exact diagonalization. We
find that in general HF+RPA gives a very good approximation to the ``exact''
ground state energy. In those cases where RPA is less satisfactory, however,
there is no obvious correlation with properties of the HF state, such as
deformation or overlap with the exact ground state wavefunction.Comment: 6 pages, 7 figures, submitted to Phys Rev
Mass Dependence of M3Y-Type Interactions and the Effects of Tensor Correlations
The mass dependence of the M3Y-type effective interactions and the effects of
tensor correlations are examined. Two-body nuclear matrix elements are obtained
by the lowest order constrained variational (LOCV) technique with and without
tensor correlations. We have found that the tensor correlations are important
especially in the triplet-even (TE) and tensor-even (TNE) channels in order to
reproduce the G-matrix elements obtained previously. Then M3Y-type potentials
for inelastic scattering are obtained by fitting our two-body matrix elements
to those of a sum of Yukawa functions for the mass numbers A=24, A=40 and A=90.Comment: 13 pages, 6 table
Quadrupole Moments of Neutron-Deficient Na
The electric-quadrupole coupling constant of the ground states of the proton
drip line nucleus Na( = 2, = 447.9 ms) and the
neutron-deficient nucleus Na( = 3/2, = 22.49 s)
in a hexagonal ZnO single crystal were precisely measured to be kHz and 939 14 kHz, respectively, using the multi-frequency
-ray detecting nuclear magnetic resonance technique under presence of an
electric-quadrupole interaction. A electric-quadrupole coupling constant of
Na in the ZnO crystal was also measured to be
kHz. The electric-quadrupole moments were extracted as Na) = 10.3
0.8 fm and Na) = 14.0 1.1 fm, using
the electric-coupling constant of Na and the known quadrupole moment of
this nucleus as references. The present results are well explained by
shell-model calculations in the full -shell model space.Comment: Accepted for publication in Physics Letters
- âŠ