共查询到20条相似文献,搜索用时 687 毫秒
1.
T. Ishii M. Asai A. Makishima I. Hossain P. Kleinheinz M. Ogawa M. Matsuda S. Ichikawa 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):15-19
Nuclei in the neutron-rich Ni region have been studied by γ-ray spectroscopy. Gamma-rays emitted from isomers, with T
1/2 > 1 ns, produced in heavy-ion deep-inelastic collisions were measured with an isomer-scope. The nuclear structure of the
doubly magic 68Ni and its neighbor 69,71Cu is discussed on the basis of the shell model. Future experiments for more neutron-rich Ni nuclei are also viewed.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
2.
E. Caurier F. Nowacki A. Poves 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):145-150
Recent shell model calculations for the neutron-rich nuclei around the magic numbers N = 20, N = 28 and N = 40 are reviewed. We stress two points: i) The crucial role played by the monopole part of the effective interaction that
determines the evolution of the spherical mean field. In particular, the reduction in the quasiparticle gaps at the magic
numbers can erode or even erase the shell closures. ii) The rich variety of structures that can be found in these situations,
with coexisting deformed and spherical states, rapid changes of behaviour with N or Z, and the massive occurrence of intruder states as ground states.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: alfredo.poves@uam.es 相似文献
3.
L. Stroe G. Lhersonneau A. Andrighetto P. Dendooven J. Huikari H. Penttilä K. Peräjärvi L. Tecchio Y. Wang 《The European Physical Journal A - Hadrons and Nuclei》2003,17(1):57-63
Cross-sections for the production of neutron-rich nuclei obtained by neutron-induced fission of natural uranium have been
measured. The neutrons were generated by bombarding a 13C target with 55 MeV protons. The results, position of the maximum in the (Z, A)-plane, width and magnitude, are very comparable with those where the neutrons are generated by bombardment of natural 12C graphite with 50 MeV deuterons. Depending on the geometry of the converter/target assembly the isotope yields, however,
are a factor of 2-3 lower due to less efficient production of neutrons per primary projectile, especially at small forward
angles.
Received: 8 November 2002 / Accepted: 20 December 2002 / Published online: 15 April 2003 相似文献
4.
We show that the spin-orbit potential of the nuclear mean field destroys isoscalar superfluid correlations in self-conjugate
nuclei. Using group theory and boson mapping techniques on a Hamiltonian including single particle splittings and a SO
ST(8) pairing interaction, we give analytical expressions for the spin-orbit dependence of some N = Z properties such as the relative position of T = 0 and T = 1 states in odd-odd systems or double binding-energy differences of even-even nuclei.
Received: 12 April 2000 / Accepted: 25 May 2000 相似文献
5.
Rajeev K. Puri Manoj K. Sharma Raj K. Gupta 《The European Physical Journal A - Hadrons and Nuclei》1998,3(3):277-280
A systematic study of isotopic dependence of fusion cross-section is carried out by adding neutrons gradually to N=Z colliding
nuclei. We find that fusion barrier position increases and height decreases, both linearly with the increase of N/Z ratio
of the compound system. The increase in barrier position is larger compared to decrease in barrier height. In terms of these
linear relationships, a parameterized form of fusion cross-sections is given for the neutron-rich colliding nuclei. The fusion
cross-sections are also enhanced linearly with the N/Z ratio, and this enhancement is larger for lower incident centre-of-mass
energies and independent of the choice of reaction partners. Experimental data and other theoretical studies are called for
to verify these results.
Received: 27 February 1998 / Revised version: 22 May 1998 相似文献
6.
A. Johnson 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):9-14
Neutron-deficient nuclei in the mass region A≈ 90-100 exhibit a large variety of phenomena. In this region the heaviest N = Z nuclei are identified and enhanced neutron-proton correlations are expected when protons and neutrons occupy identical orbitals.
A variety of nuclear shapes are predicted and observed for A? 91, including superdeformed shapes. The nucleus 100Sn is the heaviest N = Z doubly magic nucleus believed to be bound. Knowledge of the shell structure around 100Sn is of utmost importance for understanding the nuclear shell model. New results on both the N = Z nucleus 88Ru, superdeformed structures in A≈ 90 nuclei as well as the first result on the level structure in 103Sn, and an extended level structure in 102In are presented. The limitations of using stable beams and targets and the possibilities with new radioactive beams are briefly
outlined.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
7.
8.
O. Sorlin C. Donzaud F. Nowacki J.C. Angélique F. Azaiez C. Bourgeois V. Chiste Z. Dlouhy S. Grévy D. Guillemaud-Mueller F. Ibrahim K.-L Kratz M. Lewitowicz S.M. Lukyanov J. Mrasek Yu.-E. Penionzhkevich F. de Oliveira Santos B. Pfeiffer F. Pougheon A. Poves M.G. Saint-Laurent M. Stanoiu 《The European Physical Journal A - Hadrons and Nuclei》2003,16(1):55-61
The neutron-rich nuclei 23
60-63V have been produced at GANIL via interactions of a 61.8A·MeV 76Ge beam with a 58Ni target. Beta-decay to 24
60-63Cr has been investigated using combined β- and γ-ray spectroscopy. Half-lives of the 60-63V nuclei have been determined, and the existence of a beta-decay isomer in the 60V nucleus is strongly supported. The observation of low-energy 2+ states in 60Cr (646keV) and 62Cr (446keV) suggests that these isotopes are strongly deformed with β2 ∼ 0.3. This is confirmed by shell model calculations which show the dominant influence of the intruder g and d orbitals to obtain low 2+ energies in the neutron-rich Cr isotopes.
Received: 13 June 2002 / Accepted: 27 August 2002 / Published online: 17 January 2003
RID="a"
ID="a"e-mail: sorlin@ipno.in2p3.fr
Communicated by D. Guerreau 相似文献
9.
S. Hofmann 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):195-200
The nuclear shell model predicts that the next doubly magic shell-closure beyond 208Pb is at a proton number between Z = 114 and 126 and at a neutron number N = 184. The outstanding aim of experimental investigations is the exploration of this region of spherical “Superheavy Elements”.
This article describes the experiments that were performed at the GSI SHIP. They resulted in an unambiguous identification
of elements 107 to 112. They were negative so far in searching for elements 113, 116 and 118 at SHIP; however, positive results
were reported from experiments in Dubna on elements 114 and 116 and from experiments in Berkeley on element 118. The measured
decay data are compared with theoretical predictions. Some aspects concerning the reaction mechanism and the use of radioactive
beams are also presented.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: S.Hofmann@gsi.de 相似文献
10.
H. Horiuchi 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):131-133
Cluster structures of nuclei are discussed, with emphasis on nuclear clustering in unstable nuclei. The subjects we discuss
are alpha condensed states, clustering in Be and B isotopes, and clustering in 32Mg and 30Ne. The subject of alpha cluster condensation comes from the clustering nature of dilute nuclear matter. We discuss that recent
heavy-ion central collision experiments give us nice evidence of the clustering in dilute nuclear matter. We then present
a new prediction of the existence of the “alpha cluster condensed states” in the self-conjugate 4n nuclei around the breakup threshold energy into n alpha-particles. As for the clustering in neutron-rich Be, we discuss the comparison between the antisymmetrized molecular-dynamics
results and the recent experimental data, which shows that the clustering feature manifests itself very clearly in neutron-rich
Be isotopes both in the ground and excited states. Clustering in Be isotopes near neutron dripline is intimately related to
the breaking of the neutron magic number N = 8. We report our recent study about the possible relationship between the clustering and the breaking of the neutron magic
number N = 20 in 32Mg and 30Ne.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: horiuchi@ruby.scphys.kyoto-u.ac.jp 相似文献
11.
I. Hamamoto 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):21-26
Nucleons with very small binding energies present in nuclei far from the β stability line produce a unique shell structure,
which leads to the disappearance of traditional magic numbers or to the creation of new magic numbers and new deformation
regions. We study the shell structure in terms of the variation of two important ingredients, the kinetic energy and the spin-orbit
splitting, as a function of the orbital angular momentum ℓ, when binding energies of neutrons decrease towards zero. It is
also shown that for low-lying threshold strength, a negative sign is possible for the polarization charge coming from the
coupling of one-particle to isoscalar shape oscillations.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
12.
The generalized hybrid derivative coupling model has been applied to explore various ground state properties of different
nuclei. In this work we have confined our calculation only to the model characterized by the hybridization parameter α = 1/4
which gives better results than the other models of the same class, as we have seen earlier, for nuclear matter calculations.
The binding energy, single-particle energy spectra, density and charge radii of different doubly closed nuclei like 16O, 40Ca, 48Ca, 90Zr, 132Sn, 208Pb have been studied. The success of this model, in describing the doubly closed nuclei, motivates us to extend this calculation
further in the case of open shell nuclei after incorporating the pairing interaction and using a BCS transformation. We have
calculated the binding energy for such nuclei. We have also studied the isotopic shift for different Pb isotopes with respect
to 208Pb. We have compared our results with the other standard theoretical results as well as with the experimental values.
Received: 18 August 2000 / Accepted: 13 April 2001 相似文献
13.
T.Yu. Tretyakova D.E. Lanskoy 《The European Physical Journal A - Hadrons and Nuclei》1999,5(4):391-398
Properties of light neutron-rich Λ hypernuclei (16
ΛC, 12
ΛBe, and 11
ΛLi) are calculated within the Skyrme-Hartree-Fock approach. Interplay between hypernuclear interaction features and properties
of these hypernuclei is studied. Response of weakly bound neutron states to hyperon addition depends generally on core distortion
by hyperon, and it is essentially different for the different states. This response is especially sensitive to details of
the ΛN interaction for 1p
1/2 states. Implications of the nuclear spin-orbit potential and nuclear incompressibility in the neutron-rich system properties
are inferred. Dependence of the Λ binding energies in hypernuclei on Z at fixed A is discussed.
Received: 16 December 1998 相似文献
14.
An effective residual interaction between particles and holes for shell model calculations around 208Pb, derived from the interaction between free nucleons, is compared with the measured properties of proton-hole neutron states
in 208Tl and the interaction between proton holes is adjusted to newly measured level energies in 206Hg. These interaction elements are particularly relevant for neutron-rich nuclei. The adjustment of two mixing elements reproduces
the known γ-decay data in 208Tl.
Received: 2 April 2002 / Accepted: 2 May 2002 相似文献
15.
F. Azaiez M. Belleguic D. Sohler M. Stanoiu Zs. Dombrádi O. Sorlin J. Timár F. Amorini D. Baiborodin A. Bauchet F. Becker C. Borcea C. Bourgeois Z. Dlouhy C. Donzaud J. Duprat D. Guillemaud-Mueller F. Ibrahim M.J. Lopez R. Lucas S.M. Lukyanov V. Maslov J. Mrazek C. Moore F. Nowacki B.M. Nyakó Yu.-E. Penionzhkevich M.G. Saint-Laurent F. Sarazin J.A. Scarpaci G. Sletten C. Stodel M. Taylor C. Theisen G. Voltolini 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):93-97
The structure of neutron-rich light nuclei around N = 20 and 28 has been investigated at GANIL by means of in-beam gamma-spectroscopy using fragmentation reactions of 36S and 48Ca beams on a Be target. Gamma-decay of relatively high-lying excited states have been measured for the first time in nuclei
around 32Mg and 44S. Level schemes are proposed and discussed for a large number of these neutron-rich nuclei around N = 20 and N = 28.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: azaiez@ipno.in2p3.fr 相似文献
16.
The isospin dependence of shell closure phenomena is studied for light neutron-rich nuclei within a microscopic self-consistent
approach using the Gogny force. Introducing configuration mixing, 32Mg is found to be dynamically deformed, although the N = 20 spherical shell closure persists at the mean-field level for all N = 20 isotones. In contrast, the N = 28 spherical shell closure is found to disappear for N - Z≥ 10 whereas deformed shell closures are preserved and lead to shape coexistence in 44
S. Configuration mixing shows that the ground state of this nucleus is triaxially deformed. The first 2+ excitation energy Ex = 1.46 MeV and the reduced transition probability B(E2;0+
gs→ 2+
1)= 420 e
2
fm
4 obtained with our approach are in good agreement with experimental data.
Received: 26 July 2000 / Accepted: 30 August 2000 相似文献
17.
T. Kadowaki J. Asai W. Imoto S. Iwata M. Kurosawa K. Nakai A. Sato K. Imai H. Takahashi C.J. Yoon T. Maruta M. Ieiri T. Nagae H. Noumi T. Fukuda P.K. Saha B. Bassalleck 《The European Physical Journal A - Hadrons and Nuclei》2002,15(3):295-298
In order to study the hyperon-nucleon spin-orbit interaction, asymmetries of the polarized Σ+ elastic scattering on protons have been measured. The polarized hyperons were produced through the p(π+, K+) Σ+ reaction in a liquid-scintillator active target, and tracks of Σ+p scattering events were recorded with a newly developed track detector named SCITIC (scintillating track image camera). Although
analyses of 10 times more data with more sophisticated data-taking systems and more elaborated analyzing tools are under way,
data from an early stage of this experiment indicate a large Σ+p spin-orbit interaction in contrast to the case of the small ΛN spin-orbit interaction.
Received: 27 May 2002 / Accepted: 23 July 2002 / Published online: 19 November 2002
RID="a"
ID="a"e-mail: nakai@post.kek.jp
Communicated by Th. Walcher 相似文献
18.
Effective charges are calculated for protons and neutrons in the region of mass 90. It is found that their magnitudes differ
appreciably depending on whether the proton p
1/2 shell is empty or full. The calculated values are compared with values deduced from nuclei with simple configurations, and
from a fit to N=50 data. The empirical values are used in shell-model calculations of quadrupole moments of N=50-58 nuclei.
Received: 16 February 1998 相似文献
19.
Theoretical results for giant resonances in the three doubly magic exotic nuclei 78Ni, 100Sn and 132Sn are obtained from Hartree-Fock (HF) plus Random Phase Approximation (RPA) calculations using the D1S parameterization of
the Gogny two-body effective interaction. Special attention is paid to full consistency between the HF field and the RPA particle-hole
residual interaction. The results for the exotic nuclei, on average, appear similar to those of stable ones, especially for
quadrupole and octupole states. More exotic systems have to be studied in order to confirm such a trend. The low energy of
the monopole resonance in 78Ni suggests that the compression modulus in this neutron-rich nucleus is lower than the one of stable ones. 相似文献
20.
N. Itagaki S. Okabe K. Ikeda I. Tanihata 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):43-47
The structure of Be and C isotopes are investigated based on the molecular-orbit (MO) model. The low-lying states are characterized
by several configurations of valence neutrons, which are constructed as combinations of basic orbits. In 10Be, all of the observed positive-parity bands and the negative-parity bands are described within the model. The second 0+ state of 10Be has a large α-α cluster structure, and this is characterized by a (1/2+
σ)2 configuration. An enlargement of the α-α distance due to two-valence neutrons along the α-α axis makes their wave function
smooth and reduces the kinetic energy drastically. Furthermore, the contribution of the spin-orbit interaction due to coupling
between the S
z = 0 and the S
z = 1 configurations, is important. In the ground state of 12Be, the calculated energy exhibits similar characteristics, that the remarkable α clustering and the contribution of the spin-orbit
interaction make the binding of the state with (3/2-
π)2(1/2+
σ)2 configuration properly stronger in comparison with the closed p-shell (3/2-
π)2(1/2-
π)2 configuration. This is related to the breaking of the N = 8 (closed p-shell) neutron magic number. Also, the molecule-like structure of the C isotopes is investigated using a microscopic α+α+α+n+n+ . . . model. The combination of the valence neutrons in the π- and the σ-orbit is promising to stabilize the linear-chain state
against the breathing and bending modes, and it is found that the excited states of 16C are the most promising candidates for such structure.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献