共查询到20条相似文献,搜索用时 958 毫秒
1.
David L. Canham H. -W. Hammer 《The European Physical Journal A - Hadrons and Nuclei》2008,37(3):367-380
The universal properties and structure of halo nuclei composed of two neutrons (2n) and a core are investigated within an effective quantum mechanics framework. We construct an effective interaction potential
that exploits the separation of scales in halo nuclei and treat the nucleus as an effective three-body system. The uncertainty
from higher orders in the expansion is quantified through theoretical error bands. First, we investigate the possibility to
observe excited Efimov states in 2n halo nuclei. Based on the experimental data, 20C is the only halo nucleus candidate to possibly have an Efimov excited state, with an energy less than 7 keV below the scattering
threshold. Second, we study the structure of 20C and other 2n halo nuclei. In particular, we calculate their matter form factors, radii, and two-neutron opening angles. 相似文献
2.
S. F. Ban L. S. Geng W. H. Long J. Meng J. Peng J. M. Yao S. Q. Zhang S. G. Zhou 《The European physical journal. Special topics》2007,150(1):139-144
The recent progress of the relativistic many-body approach
by the group at Peking University will be reviewed. In particular,
axially deformed relativistic Hartree-Bogoliubov approach in
Woods-Saxon basis aiming at halo nucleus, time-odd triaxial RMF
approach, the adiabatic and configuration-fixed constrained triaxial
RMF approaches, a Reflection ASymmetric RMF (RAS-RMF) approach, and
a new relativistic Hartree-Fock (RHF) approach with
density-dependent σ,ω,ρ and π meson-nucleon
couplings for finite nuclei and nuclear matter, will be highlighted. 相似文献
3.
Halo structures of some light mirror nuclei are investigated with the relativistic mean field (RMF) theory. The calculations show that the dispersion of the valence proton is larger than that of the valence neutron in its mirror nucleus, the difference between the root-mean-square (rms) radius of the valence nucleon in each pair of mirror nuclei becomes smaller with the increase of the mass number A, and all the ratios of the rms radius of the valence nucleon to that of the matter in each pair of mirror nuclei decrease almost linearly with the increase of the mass number A. 相似文献
4.
G. Belovitsky E. Konobeevski A. Stepanov V. Zavarzina S. Zuyev N. Polukhina N. Starkov S. Lukyanov Yu. Sobolev 《The European physical journal. Special topics》2007,150(1):5-7
To estimate the probability of two-neutron
configurations in halo nuclei, we propose an experimental method
of studying neutron-neutron correlations at periphery of such
nuclei by measuring two-neutron transfer reaction. The
experimental study of 6He + A ↦ 4He + B for various targets
is performed using 6He beam of Flerov Laboratory of Nuclear
Reactions (JINR, Dubna) at energy of about 15 MeV/u and technique
of nuclear photoemulsions. Searching for events of two-nucleon
transfer reaction and their processing is performed using the
PAVICOM-setup at P.N. Lebedev Physical Institute. 相似文献
5.
P. Egelhof G.D. Alkhazov M.N. Andronenko A. Bauchet A.V. Dobrovolsky S. Fritz G.E. Gavrilov H. Geissel C. Gross A.V. Khanzadeev G.A. Korolev G. Kraus A.A. Lobodenko G. Münzenberg M. Mutterer S.R. Neumaier T. Schäfer C. Scheidenberger D.M. Seliverstov N.A. Timofeev A.A. Vorobyov V.I. Yatsoura 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):27-33
Proton-nucleus elastic scattering at intermediate energies, a well-established method for probing nuclear-matter density distributions
of stable nuclei, was applied for the first time to exotic nuclei. This method is demonstrated to be an effective means for
obtaining accurate and detailed information on the size and radial shape of halo nuclei. Absolute differential cross-sections
for small-angle scattering were measured at energies near 700 MeV/u for the neutron-rich helium isotopes 6He and 8He, and more recently for the lithium isotopes 6Li, 8Li, 9Li and 11Li, using He and Li beams provided by the fragment separator FRS at GSI Darmstadt. Experiments were performed in inverse kinematics
using the hydrogen-filled ionization chamber IKAR which served simultaneously as target and recoil-proton detector. For deducing
nuclear-matter distributions, differential cross-sections calculated with the aid of the Glauber multiple-scattering theory,
using various parametrizations for the nucleon density distributions as input, were fitted to the experimental cross-sections.
The results on nuclear-matter radii and matter distributions are presented, and the significance of the data for a halo structure
is discussed. Nuclear-matter distributions obtained for 6He and 8He conform with the concept that both nuclei compose of α-particle like cores and significant neutron halos. The matter distribution
in 11Li exhibits, as expected from previous reaction cross-section studies with nuclear targets, the by far most extended halo
component of all nuclei being investigated. In addition the present data allow a quantitative comparison of the structure
of the He and Li isobares of either the mass number A = 6 or A = 8. The measured differential cross-sections have also been used for probing density distributions as predicted from various
microscopic calculations. A few examples are presented.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: p.egelhof@gsi.de 相似文献
6.
The neutron dripline has presently been reached only for the lightest nuclei up to the element oxygen. In this region of light
neutron-rich nuclei, scattering experiments are feasible even for dripline nuclei by utilizing high-energy secondary beams
produced by fragmentation. In the present article, reactions of high-energy radioactive beams will be exemplified using recent
experimental results mainly derived from measurements of breakup reactions performed at the LAND and FRS facilities at GSI
and at the S800 spectrometer at the NSCL. Nuclear and electromagnetically induced reactions allow probing different aspects
of nuclear structure at the limits of stability related to the neutron-proton asymmetry and the weak binding close to the
dripline. Properties of the valence-neutron wave functions are studied in the one-neutron knockout reaction, revealing the
changes of shell structure when going from the beta-stability line to more asymmetric loosely bound neutron-rich systems.
The vanishing of the N = 8 shell gap for neutron-rich systems like 11Li and 12Be, or the new closed N = 14, 16 shells for the oxygen isotopes are examples. The continuum of weakly bound nuclei and halo states can be studied
by inelastic scattering. The dipole response, for instance, is found to change dramatically when going away from the valley
of stability. A redistribution of the dipole strength towards lower excitation energies is observed for neutron-rich nuclei,
which partly might be due to a new collective excitation mode related to the neutron-proton asymmetry. Halo nuclei, in particular,
show strong dipole transitions to the continuum at the threshold, being directly related to the ground-state properties of
the projectile. Finally, an outlook on future experimental prospects is given. 相似文献
7.
The g-factors of the positive parity rotational states up to spin I = 8^+ for the ground state band in even-even nuclei S2Sr have been measured by a transient-magnetic-field ion implantation perturbed angular distribution method. The experimentally measured 9-factors increase with the increasing spin along the band and show that the g9/2 proton aligns only and the alignment starts from I =6^+. The measured g-factors also indicate that the nuclei ^82Sr gain their spins by the quasi-proton alignment at higher spin. 相似文献
8.
F. Barranco P.F. Bortignon R.A. Broglia G. Colò E. Vigezzi 《The European Physical Journal A - Hadrons and Nuclei》2001,11(4):385-392
If neutrons are progressively added to a normal nucleus, the Pauli principle forces them into states of higher momentum. When
the core becomes neutron saturated, the nucleus expels most of the wave function of the last neutrons outside to form a halo,
which, because of its large size, can have a lower momentum. It is an open question how nature stabilizes such a fragile system
and provides the glue needed to bind the halo neutrons to the core. Here, we show that this problem is similar to that of
the instability of the normal state of an electron system at zero temperature solved by Cooper, a solution which is at the
basis of BCS theory of superconductivity. By mimicking this approach using, aside from the bare nucleon-nucleon interaction,
the long wavelength vibrations of the nucleus 11Li, the paradigm of halo nuclei, as tailored glues of the least bound neutrons, we are able to obtain a unified and quantitative
picture of the observed properties of 11Li.
Received: 9 May 2001 / Accepted: 17 November 2001 相似文献
9.
10.
Fully-microscopic no-core shell model (NCSM) calculations of all stable s and p shell nuclei are used to determine a realistic NN interaction, JISP16, describing not only the two-nucleon data but the binding energies and spectra of nuclei with A?16 as well. The JISP16 interaction, providing rapid convergence of the NCSM calculations, is obtained in an ab exitu approach by phase-equivalent transformations of the JISP6 NN interaction. 相似文献
11.
A new parameterization of the effective nucleon–nucleon Gogny interaction is proposed. It reproduces the neutron matter equation of state much better than the commonly used D1S Gogny interaction and furthermore reduces the binding energies' drift for the major part of the isotopic chains. Other important nuclear properties related both to nuclear matter and finite nuclei are studied and shown to be of similar quality as with D1S. 相似文献
12.
13.
14.
The ground state properties and the properties of low-lying states of the even-even6Be-12Be beryllium isotopes are investigated using the extended version of the Antisymmetrized Molecular Dynamics Multi-Slater Determinant
model. The theoretical method is found to be very useful to study ground state properties of various nuclei covering light
unstable nuclei. Many experimental data can be successfully reproduced by the adopted approach. Binding energies, the energies
of the 2
1
+
states, electromagnetic transition strengths and quadrupole moments of proton and neutron distribution are calculated.
This work is supported in part by Grant-in-Aid for Scientific Research (13740145) from the Ministry of Education, Science
and Culture. 相似文献
15.
A.V. Anisovich V.V. Anisovich V.A. Nikonov L. Montanet 《The European Physical Journal A - Hadrons and Nuclei》1999,6(3):247-249
We discuss γγ partial widths of pseudoscalar/isoscalar mesons η:(M) in the mass region M∼ 1000–1500 MeV. The transition amplitudes η:(1295) →γγ and η:(1440) →γγ are studied within an assumption that the decaying
mesons are the members of the first radial excitation nonet 21
S
0qˉq. The calculations show that partial widths being of the order of 0.1 keV are dominantly due to the nˉn meson component
while the contribution of the sˉs component is small.
Received: 24 September 1999 相似文献
16.
17.
Half-lives of the proton radioactivity for spherical proton emitters are investigated theoretically in the Wentzel- Kramers-Brillouin approximation. Microscopic proton-nucleus interaction potentials are obtained by folding the densities of the residual daughter nuclei with renormalized M3Y effective interactions. We also take the spectroscopic factor (Sp) into account in the calculation, which is evaluated in the relativistic mean field approach using the force NL3. The calculated results are found to be in good agreement with the experimental data. 相似文献
18.
GUOWen-Jun JIANGHuan-Qing LIUJian-Ye ZUOWei RENZhong-Zhou LEEXi-Guo 《理论物理通讯》2003,40(5):577-584
We develop a method for calculation of the total reaction cross sections induced by the halo nuclei and stable nuclei. This approach is based on the Glauber theory, which is valid for nuclear reactions at high energies. It is extended for nuclear reactions at low energies and intermediate energies by including both the quantum correction and Coulomb correction under the assumption of the effective nuclear density distribution. The calculated results of the total reaction cross section induced by stable nuclei agree well with 30 experimental data within 10 percent accuracy.The comparison between the numerical results and 20 experimental data for the total nuclear reaction cross section induced by the neutron halo nuclei and the proton halo nuclei indicates a satisfactory agreement after considering the halo structure of these nuclei, which implies quite digerent mean fields for the nuclear reactions induced by halo nuclei and stable nuclei. The halo nucleon distributions and the root-mean-square radii of these nuclei can be extracted from the above comparison based on the improved Glauber model, which indicates clearly the halo structures of these nuclei. Especially,it is clear to see that the medium correction of the nucleon-nucleon collision has little effect on the total reaction cross sections, induced by the halo nuclei due to the very weak binding and the very extended density distribution. 相似文献
19.
We develop a method for calculation of the total reaction cross sections induced by the halo nuclei and stable. nuclei. This approach is based on the Glauber theory, which is valid for nuclear reactions at high energies. It is extended for nuclear reactions at low energies and intermediate energies by including both the quantum correction and Coulomb correction under the assumption of the effective nuclear density distribution. The calculated results of the total reaction cross section induced by stable nuclei agree well with 30 experimental data within 10 percent accuracy. The comparison between the numerical results and 20 experimental data for the total nuclear reaction cross section induced by the neutron halo nuclei and the proton halo nuclei indicates a satisfactory agreement after considering the halo structure of these nuclei, which implies quite different mean fields for the nuclear reactions induced by halo nuclei and stable nuclei. The halo nucleon distributions and the root-mean-square radii of these nuclei can be extracted from the above comparison based on the improved Glauber model, which indicates clearly the halo structures of these nuclei. Especially,it is clear to see that the medium correction of the nucleon-nucleon collision has little effect on the total reaction cross sections induced by the halo nuclei due to the very weak binding and the very extended density distribution. 相似文献
20.
H.F. Lü J. Meng S.Q. Zhang S.-G. Zhou 《The European Physical Journal A - Hadrons and Nuclei》2003,17(1):19-24
Properties of single- Λ and double- Λ hypernuclei for even-N Ca isotopes ranging from the proton dripline to the neutron dripline are studied using the relativistic continuum Hartree-Bogoliubov
theory with a zero-range pairing interaction. Compared with ordinary nuclei, the addition of one or two Λ-hyperons lowers
the Fermi level. The predicted neutron dripline nuclei are, respectively, 75
ΛCa and 76
2ΛCa, as the additional attractive force provided by the Λ-N interaction shifts nuclei from outside to inside the dripline.
Therefore, the last bound hypernuclei have two more neutrons than the corresponding ordinary nuclei. Based on the analysis
of two-neutron separation energies, neutron single-particle energy levels, the contribution of continuum and nucleon density
distribution, giant halo phenomena due to the pairing correlation, and the contribution from the continuum are suggested to
exist in Ca hypernuclei similar to those that appear in ordinary Ca isotopes.
Received: 21 October 2002 / Accepted: 11 January 2003 / Published online: 8 April 2003 相似文献