412 research outputs found
Kinetic energy and spin-orbit splitting in nuclei near neutron drip line
Two important ingredients of nuclear shell-structure, kinetic energy and
spin-orbit splitting, are studied as a function of orbital angular momenta \ell
and binding energies, when binding energies of neutrons decrease towards zero.
If we use the standard parameters of the Woods-Saxon potential in \beta stable
nuclei and approach the limit of zero binding energy from 10 MeV, the
spin-orbit splitting for n=1 orbitals decreases considerably for \ell=1, while
for \ell > 2 little decreasing is observed in the limit. In contrast, the
kinetic energy decreases considerably for \ell \simleq 3. The smaller the \ell
values of orbitals, the larger the decreasing rate of both kinetic energy and
spin-orbit splitting. The dependence of the above bservation on the diffuseness
of potentials is studied.Comment: 12 pages, 3 figures, submitted to Nucl. Phy
Low Energy States of : Elements on the Doubly-Magic Nature of Ni
Excited levels were attributed to Ga for the first time
which were fed in the -decay of its mother nucleus Zn produced in
the fission of U using the ISOL technique. We show that the structure
of this nucleus is consistent with that of the less exotic proton-deficient
N=50 isotones within the assumption of strong proton Z=28 and neutron N=50
effective shell effects.Comment: 4 pages, REVTeX 4, 5 figures (eps format
Collective Properties of Low-lying Octupole Excitations in , and
The octupole strengths of -stable nucleus , a
neutron skin nucleus and a neutron drip line nucleus
are studied by using the self-consistent Hartree-Fock
calculation plus the random phase approximation (RPA) with Skyrme interaction.
The collective properties of low-lying excitations are analyzed by using
particle-vibration coupling. The results show that the lowest isoscalar states
above threshold in and are the
superpositions of collective excitations and unperturbed transitions from bound
state to nonresonance states. For these three nuclei, both the low-lying
isoscalar states and giant isoscalar resonance carry isovector strength. The
ratio B(IV)/B(IS) is checked. It is found that, for , the
ratios are equal to in good accuracy, while for
and , the ratios are much larger than
. This results from the excess neutrons with small binding
energies in and .Comment: 14 pages, 10 figure
A method of implementing Hartree-Fock calculations with zero- and finite-range interactions
We develop a new method of implementing the Hartree-Fock calculations. A
class of Gaussian bases is assumed, which includes the Kamimura-Gauss basis-set
as well as the set equivalent to the harmonic-oscillator basis-set. By using
the Fourier transformation to calculate the interaction matrix elements, we can
treat various interactions in a unified manner, including finite-range ones.
The present method is numerically applied to the spherically-symmetric
Hartree-Fock calculations for the oxygen isotopes with the Skyrme and the Gogny
interactions, by adopting the harmonic-oscillator, the Kamimura-Gauss and a
hybrid basis-sets. The characters of the basis-sets are discussed. Adaptable to
slowly decreasing density distribution, the Kamimura-Gauss set is suitable to
describe unstable nuclei. A hybrid basis-set of the harmonic-oscillator and the
Kamimura-Gauss ones is useful to accelerate the convergence, both for stable
and unstable nuclei.Comment: LaTex 32 pages with 6 Postscript figure
Discovery of the Vanadium Isotopes
Twenty-four vanadium isotopes have so far been observed; the discovery of
these isotopes is discussed. For each isotope a brief summary of the first
refereed publication, including the production and identification method, is
presented.Comment: to be published in At. Data. Nucl. Data Table
Nuclear break-up of 11Be
The break-up of 11Be was studied at 41AMeV using a secondary beam of 11Be
from the GANIL facility on a 48Ti target by measuring correlations between the
10Be core, the emitted neutrons and gamma rays. The nuclear break-up leading to
the emission of a neutron at large angle in the laboratory frame is identified
with the towing mode through its characteristic n-fragment correlation. The
experimental spectra are compared with a model where the time dependent
Schrodinger equation (TDSE) is solved for the neutron initially in the 11 Be. A
good agreement is found between experiment and theory for the shapes of neutron
experimental energies and angular distributions. The spectroscopic factor of
the 2s orbital is tentatively extracted to be 0.46+-0.15. The neutron emission
from the 1p and 1d orbitals is also studied
Discovery of the Cobalt Isotopes
Twenty-six cobalt isotopes have so far been observed; the discovery of these
isotopes is discussed. For each isotope a brief summary of the first refereed
publication, including the production and identification method, is presented.Comment: to be published in Atomic Data and Nuclear Data Table
Rapid onset of collectivity in the vicinity of 78Ni
gamma-rays following the B and B-n decay of the very neutron rich 84Ga
produced by photo-fission of 238U have been studied at the newly built ISOL
facility of IPN Orsay: ALTO. Two activities were observed and assigned to two
B-decaying states: 84gGa, I = (0\^-) and 84mGa, I = (3\^-, 4\^-). Excitation
energies of the 2+1 and 4+1 excited states of 84Ge were measured at E(2+1) =
624.3 keV and E(4+1) = 1670.1 keV. Comparison with HFB+GCM calculations allows
to establish the collective character of this nucleus indicating a substantial
N=50 core polarization. The excitation energy of the 1/2+1 state in 83Ga known
to carry a large part of the neutron 3s1/2 strength was measured at 247.8keV.
Altogether these data allow to confirm the new single particle state ordering
which appears immediately after the double Z=28 and N=50 shell closure and to
designate 78Ni as a fragile and easily polarized doubly-magic core.Comment: 4 pages, ReVTe
Angular momentum projected analysis of Quadrupole Collectivity in \protect(^{30,32,34}Mg\protect) and \protect(^{32,34,36,38}Si\protect) with the Gogny interaction
A microscopic angular momentum projection after variation is used to describe
quadrupole collectivity in (^{30,32,34}Mg) and (^{32,34,36,38}Si). The
Hartree-Fock-Bogoliubov states obtained in the quadrupole constrained mean
field approach are taken as intrinsic states for the projection. Excitation
energies of the first (2^{+}) states and the (B(E2,0^{+}\to 2^{+})) transition
probabilities are given. A reasonable agreement with available experimental
data is obtained. It is also shown that the mean field picture of those nuclei
is strongly modified by the projection.Comment: 10 pages, 2 figures, to be published in Phys. Lett.
Spectroscopy of F
The structure of the weakly-bound F odd-odd nucleus,
produced from Na nuclei, has been investigated at GANIL by means of
the in-beam -ray spectroscopy technique. A single -line is
observed at 657(7) keV in F which has been ascribed to the decay of
the excited J= state to the J=1 ground state. The possible presence of
intruder negative parity states in F is also discussed.Comment: 3 pages, 1 figure, accepted for publication in Physical Review
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