584 research outputs found
The proton and neutron distribution in Na isotopes: the development of halo and shell structure
The interaction cross sections for reaction are calculated
using Glauber model. The continuum Hartree-Bogoliubov theory has been
generalized to treat the odd particle system and take the continuum into
account. The theory reproduces the experimental result quite well. The matter
distributions from the proton drip line to the neutron drip line in Na isotopes
have been systematically studied and presented. The relation between the shell
effects and the halos has been examined. The tail of the matter distribution
shows a strong dependence on the shell structure. The neutron N=28 closure
shell fails to appear due to the coming down of the and .
The development of the halo was understood as changes in the occupation in the
next shell or the sub-shell close to the continuum limit. The central proton
density is found to be decreasing near the neutron drip line, which is due to
the proton-neutron interaction. However the diffuseness of the proton density
does not change for the whole Na isotopes.Comment: 10 pages, 4 figure
Study of Proton Magic Even-Even Isotopes and Giant Halos of Ca Isotopes with Relativistic Continuum Hartree-Bogoliubov Theory
We study the proton magic O, Ca, Ni, Zr, Sn, and Pb isotope chains from the
proton drip line to the neutron drip line with the relativistic continuum
Hartree-Bogoliubov (RCHB) theory. Particulary, we study in detail the
properties of even-even Ca isotopes due to the appearance of giant halos in
neutron rich Ca nuclei near the neutron drip line. The RCHB theory is able to
reproduce the experimental binding energies and two neutron separation
energies very well. The predicted neutron drip line nuclei are
O, Ca, Ni, Zr, Sn, and Pb,
respectively. Halo and giant halo properties predicted in Ca isotopes with
are investigated in detail from the analysis of two neutron separation
energies, nucleon density distributions, single particle energy levels, the
occupation probabilities of energy levels including continuum states. The
spin-orbit splitting and the diffuseness of nuclear potential in these Ca
isotopes are studied also. Furthermore, we study the neighboring lighter
isotopes in the drip line Ca region and find some possibility of giant halo
nuclei in the Ne-Na-Mg drip line nuclei.Comment: 45 pages, 20 figure
Coulomb and nuclear breakup of three-body halo nuclei
We investigate dissociation reactions of loosely bound and spatially extended
three-body systems. We formulate a practical method for simultaneous treatment
of long-range Coulomb and short-range nuclear interactions. We use He
(n+n+) and Li (n+n+Li) as examples and study the
two-neutron separation cross sections as functions of target and beam energy.
Individual Coulomb and nuclear as well as interference contributions are also
extracted.Comment: 7 pages, 3 figures, 'epl.cls' style (also sent
The relativistic continuum Hartree-Bogoliubov description of charge-changing cross section for C,N,O and F isotopes
The ground state properties including radii, density distribution and one
neutron separation energy for C, N, O and F isotopes up to the neutron drip
line are systematically studied by the fully self-consistent microscopic
Relativistic Continuum Hartree-Bogoliubov (RCHB) theory. With the proton
density distribution thus obtained, the charge-changing cross sections for C,
N, O and F isotopes are calculated using the Glauber model. Good agreement with
the data has been achieved. The charge changing cross sections change only
slightly with the neutron number except for proton-rich nuclei. Similar trends
of variations of proton radii and of charge changing cross sections for each
isotope chain is observed which implies that the proton density plays important
role in determining the charge-changing cross sections.Comment: 10 pages, 4 figure
Hyperfine Anomaly of Be Isotopes and Anomalous Large Anomaly in Be
A new result of investigations of the hyperfine structure (hfs) anomaly in Be
isotopes is presented. The hfs constant for Be is obtained by using the
core plus neutron type wave function: . A large hfs anomaly of Be is found, which is mainly due
to a large radius of the halo single particle state.Comment: 14 pages, Late
Direct radiative capture of p-wave neutrons
The neutron direct radiative capture (DRC) process is investigated,
highlighting the role of incident p-wave neutrons. A set of calculations is
shown for the 12-C(n,gamma) process at incoming neutron energies up to 500 keV,
a crucial region for astrophysics. The cross section for neutron capture
leading to loosely bound s, p and d orbits of 13-C is well reproduced by the
DRC model demonstrating the feasibility of using this reaction channel to study
the properties of nuclear wave functions on and outside the nuclear surface. A
sensitivity analysis of the results on the neutron-nucleus interaction is
performed for incident s- as well as p-waves. It turned out that the DRC cross
section for p-wave neutrons is insensitive to this interaction, contrary to the
case of incident s-wave neutrons.
PACS number(s): 25.40Lw,21.10Gv,23.40.HcComment: 16 pages, REVTeX file, PostScript file, .dvi fil
Molecular-orbital structure in neutron-rich C isotopes
The molecule-like structure of the C isotopes (A=12, 14, 16) is investigated using a microscopic model. The valence neutrons are classified based on the molecular-orbit (MO) model, and both -orbit and -orbit are introduced around three -clusters. The valence neutrons which occupy the -orbit increase the binding energy and stabilize the linear-chain of 3 against the breathing-like break-up. However, C with the -orbit does not show clear energy minimum against the bending-like path. The combination of the valence neutrons in the - and the -orbit is promising to stabilize the linear-chain state against the breathing- and bending- modes, and it is found that the excited states of C with the configuration for the four valence neutrons is one of the most promising candidates for such structure
Spin-orbit splitting and the tensor component of the Skyrme interaction
We study the role of the tensor term of the Skyrme effective interactions on
the spin-orbit splittings in the N=82 isotones and Z=50 isotopes. The different
role of the triplet-even and triplet-odd tensor forces is pointed out by
analyzing the spin-orbit splittings in these nuclei. The experimental isospin
dependence of these splittings cannot be described by Hartree-Fock calculations
employing the usual Skyrme parametrizations, but is very well accounted for
when the tensor interaction is introduced. The capability of the Skyrme forces
to reproduce binding energies and charge radii in heavy nuclei is not destroyed
by the introduction of the tensor term. Finally, we also discuss the effect of
the tensor force on the centroid of the Gamow-Teller states.Comment: Submitted to Phys. Lett.
Deformed nuclear halos
Deformation properties of weakly bound nuclei are discussed in the deformed
single-particle model. It is demonstrated that in the limit of a very small
binding energy the valence particles in specific orbitals, characterized by a
very small projection of single-particle angular momentum onto the symmetry
axis of a nucleus, can give rise to the halo structure which is completely
decoupled from the rest of the system. The quadrupole deformation of the
resulting halo is completely determined by the intrinsic structure of a weakly
bound orbital, irrespective of the shape of the core.Comment: LaTeX source (21 pages) and postscript file with figures (15 pages).
Accepted to Nucl. Phys.
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