691 research outputs found
Exotic nuclei far from the stability line
The recent availability of radioactive beams has opened up a new era in
nuclear physics. The interactions and structure of exotic nuclei close to the
drip lines have been studied extensively world wide, and it has been revealed
that unstable nuclei, having weakly bound nucleons, exhibit characteristic
features such as a halo structure and a soft dipole excitation. We here review
the developments of the physics of unstable nuclei in the past few decades. The
topics discussed in this Chapter include the halo and skin structures, the
Coulomb breakup, the dineutron correlation, the pair transfer reactions, the
two-nucleon radioactivity, the appearance of new magic numbers, and the pygmy
dipole resonances.Comment: 43 pages, 30 eps figures. chapter in "100 years of subatomic
physics", edited by E.M. Henley and S. Elli
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
The surface diffuseness and the spin-orbital splitting in relativistic continuum Hartree-Bogoliubov theory
The Relativistic Continuum Hartree Bogoliubov theory (RCHB), which is the
extension of the Relativistic Mean Field and the Bogoliubov transformation in
the coordinate representation, has been used to study tin isotopes. The pairing
correlation is taken into account by a density-dependent force of zero range.
RCHB is used to describe the even-even tin isotopes all the way from the proton
drip line to the neutron drip line. The contribution of the continuum which is
important for nuclei near the drip-line has been taken into account. The
theoretical as well as the neutron, proton, and matter radii are
presented and compared with the experimental values where they exist. The
change of the potential surface with the neutron number has been investigated.
The diffuseness of the potentials in tin isotopes is analyzed through the
spin-orbital splitting in order to provide new way to understand the halo
phenomena in exotic nuclei. The systematic of the isospin and energy dependence
of these results are extracted and analyzed.Comment: 11 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
Toward precision mass measurements of neutron-rich nuclei relevant to -process nucleosynthesis
The open question of where, when, and how the heavy elements beyond iron
enrich our Universe has triggered a new era in nuclear physics studies.\ Of all
the relevant nuclear physics inputs, the mass of very neutron-rich nuclides is
a key quantity for revealing the origin of heavy elements beyond iron.\
Although the precise determination of this property is a great challenge,
enormous progress has been made in recent decades, and it has contributed
significantly to both nuclear structure and astrophysical nucleosynthesis
studies.\ In this review, we first survey our present knowledge of the nuclear
mass surface, emphasizing the importance of nuclear mass precision in
-process calculations.\ We then discuss recent progress in various methods
of nuclear mass measurement with a few selected examples.\ For each method, we
focus on recent breakthroughs and discuss possible ways of improving the
weighing of -process nuclides.Comment: 10 figures, review articles in Frontiers of Physic
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
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
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
The neutron halo of He in a microscopic model
The two--neutron separation energy of He has been reproduced for the
first time in a realistic parameter--free microscopic multicluster model
comprising the and clusterizations, with cluster
breathing excitations included. The contribution of the channel is
substantial. A very thick (0.85 fm) neutron halo has been found in full
agreement with the results of the latest phenomenological analysis.Comment: Submitted to Phys. Rev. C, 8 pages, Latex with Revtex, 2 figures (not
included) available on request, 08-03-9
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
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