共查询到20条相似文献,搜索用时 15 毫秒
1.
S. M. Lenzi E. E. Maqueda P. von Brentano 《The European Physical Journal A - Hadrons and Nuclei》2006,27(3):341-347
We show that the SU(3) coupling scheme reproduces the data for E2 transitions in N = Z even-even nuclei both of the sd and the pf shells. The SU(3) results are compared with large-scale shell model calculations. Along the ground-state band-like structures, the increase
of the B(E2) values with spin toward a maximum value and the subsequent fall with further increasing spin are reproduced rather well.
The role of the quadrupole-quadrupole term of the nuclear residual interaction is stressed. 相似文献
2.
3.
P. Van Isacker O. Juillet 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):233-236
Symmetries have played an important role in the elucidation of the structure of nuclei and will continue to do so for exotic
nuclei. As an example, an application of pseudo-SU(4) symmetry is discussed. It can be used as a starting point for a boson model that includes T = 0 as well as T = 1 bosons (IBM-4); applications are presented for N = Z nuclei from 58Cu to 70Br.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: isacker@ganil.fr 相似文献
4.
G. Lévai J. Cseh P. Van Isacker 《The European Physical Journal A - Hadrons and Nuclei》2001,12(3):305-308
A supersymmetry scheme is proposed for nuclear cluster systems. The bosonic sector of the superalgebra describes the relative
motion of the clusters, while its fermionic sector is associated with their internal structure. An example of core + α configurations
is discussed in which the core is a p-shell nucleus and the underlying superalgebra is U(4|12). The α-cluster states of the nuclei 20Ne and 19F are analyzed and correlations between their spectra, electric quadrupole transitions, and one-nucleon transfer reactions
are interpreted in terms of U(4|12) supersymmetry.
Received: 14 September 2001 / Accepted: 26 October 2001 相似文献
5.
V.K.B. Kota U. Datta Pramanik 《The European Physical Journal A - Hadrons and Nuclei》1998,3(3):243-253
The SUBFF(3) dynamical symmetry limits of interacting boson – fermion – fermion model are identified and they are appropriate for heavy
deformed odd – odd nuclei for configurations with both the odd proton and odd neutron occupying all the natural parity orbits
in the corresponding valence shells. There are three symmetry limits and their correspondence with two quasi-particle (proton-neutron)
Nilsson configurations is established; one of the limits mixes both Nilsson nz's and Λ's and other two limits mix only Nilsson Λ's. The 191Ir (d,t) 190Ir single nucleon transfer spectroscopic strengths are well described by one of the symmetry limits that mixes only Nilsson
Λ's.
Received: 22 June 1998 相似文献
6.
K.W. Schmid 《The European Physical Journal A - Hadrons and Nuclei》2001,12(1):29-40
The mathematical tools to restore Galilei invariance in the nuclear many-body problem with the help of projection techniques
are presented. For simple oscillator configurations recursion relations for the various elementary contractions are derived.
The method is then applied to simple configurations for the ground states of 4He, 16O and 40Ca as well as to the corresponding one-hole and one-particle states. As a first application the spectral functions and spectroscopic
factors for the above-mentioned doubly even nuclei are investigated. It turns out that the conventional picture of an uncorrelated
system underestimates the single-particle strengths of the hole states from the last occupied shell while that of the higher
excited hole states is overestimated considerably. These results are in complete agreement with those derived by Dieperink
and de Forest using different methods. Similar effects are seen for the particle states which have not been studied before.
All the calculations presented here are performed analytically and thus can be checked explicitly by the interested reader.
Received: 20 February 2001 / Accepted: 11 September 2001 相似文献
7.
S.S. Dimitrova D.N. Kadrev A.N. Antonov M.V. Stoitsov 《The European Physical Journal A - Hadrons and Nuclei》2000,7(3):335-345
The two-body density matrix for 4He,16O and 40Ca within the Low-order approximation of the Jastrow correlation method is considered. Closed analytical expressions for the
two-body density matrix, the center of mass and relative local densities and momentum distributions are presented. The effects
of the short-range correlations on the two-body nuclear characteristics are investigated.
Received: 11 September 1999 / Revised version: 20 December 1999 相似文献
8.
9.
K.W. Schmid 《The European Physical Journal A - Hadrons and Nuclei》2002,13(3):319-338
The effects of the restoration of Galilei invariance in the nuclear many-body problem on the electromagnetic properties of
simple bound states are investigated. For this purpose the form factors for elastic electron scattering from the oscillator
ground states of 4He, 16O and 40Ca as well as those for elastic and inelastic electron scattering between various one-hole states with respect to these reference
configurations are computed with and without projection into the center-of-momentum rest frame. It is demonstrated that, in
some cases, the full restoration of Galilei invariance produces results which are considerably different from those obtained
with the usual approximate way to treat the center-of-mass motion. The same holds for the mathematical Coulomb sum rules and
their first and second moments obtained for the above-mentioned nuclei.
Received: 21 February 2001 / Accepted: 20 December 2001 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.
12.
K.W. Schmid 《The European Physical Journal A - Hadrons and Nuclei》2002,14(4):413-438
The effects of the restoration of Galilei invariance in the nuclear many-body problem on the energies of simple bound states
are investigated. As examples we consider the oscillator ground states of 4He, 16O and 40Ca as well as the various hole states with respect to these reference configurations. Density-independent as well as density-dependent
interactions are studied. It turns out that the full restoration of Galilei-invariance yields considerable contributions on
top of the trivial 1/A effect resulting from removing the center-of-momentum part of the Hamiltonian.
Received: 20 February 2001 / Accepted: 10 May 2002 相似文献
13.
O. Civitarese F. Montani M. Reboiro 《The European Physical Journal A - Hadrons and Nuclei》2001,11(3):263-270
The treatment of the separable pairing interaction in the context of the BRST formalism and in the Dyson boson expansion method
is discussed. The approach is based on the use of the vacuum expectation value of the boson number operator to define a suitable
mean field.
Received: 10 April 2000 / Accepted: 6 July 2001 相似文献
14.
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
15.
S. Stoica I. Mihut J. Suhonen 《The European Physical Journal A - Hadrons and Nuclei》1998,3(4):319-323
Charge-changing transitions are considered in an extended Lipkin-Meshkov-Glick (LMG) model taking into account explicitly
the proton and neutron degrees of freedom. The proton and neutron Hamiltonians are taken to be of the LMG form and, in addition,
a residual proton-neutron interaction is included. Model charge-changing operators and their action on eigenfunctions of the
model Hamiltonian are defined. Transition amplitudes of these operators are calculated using exact eigenfunctions and then
the RPA approximation. The best agreement between the two kinds of calculation is obtained when the correlated RPA ground
state, instead of the uncorrelated HF ground state, is employed and when the proton-neutron residual interaction, besides
the proton-proton and neutron-neutron residual interactions, is taken into account in the model Hamiltonian.
Received: 4 May 1998 相似文献
16.
Semiclassical expansions derived in the framework of the Extended Thomas-Fermi approach for the kinetic energy density τ(
r) and the spin-orbit density
J(
r) as functions of the local density ρ(
r) are used to determine the central nuclear potentials V
n(
r) and V
p(
r) of the neutron and proton distribution for effective interactions of the Skyrme type. We demonstrate that the convergence
of the resulting semiclassical expansions for these potentials is fast and that they reproduce quite accurately the corresponding
Hartree-Fock average fields.
Received: 12 February 2000 / Accepted: 14 March 2002 相似文献
17.
P. Guazzoni M. Jaskola L. Zetta J.N. Gu A. Vitturi G. Graw R. Hertenberger P. Schiemenz B. Valnion U. Atzrott G. Staudt 《The European Physical Journal A - Hadrons and Nuclei》1998,1(4):365-378
The (p,α) reaction on 90Zr has been studied in a high resolution experiment at an incident proton energy of 22 MeV. The cross section and asymmetry
angular distributions for transitions to 36 levels of 87Y with an excitation energy up to 3 MeV have been measured. DWBA analyses of experimental angular distributions, using either
Woods-Saxon or Double Folded potentials for the exit channel, have been done, allowing either the confirmation of previous
spin and parity values or the assignment of new spin and parity to a large number of states. The structure of low lying states
of 87Y has been studied in the framework of the shell model, using the OXBASH code. With the interaction PMM90 reasonable agreement
is obtained for part of the negative parity spectrum.
Received: 17 November 1997 相似文献
18.
19.
J.G. Hirsch P.O. Hess O. Civitarese 《The European Physical Journal A - Hadrons and Nuclei》2002,14(3):355-364
Coherent states are used as trial states to determine, variationally, the structure of the eigenvectors belonging to a schematic
Hamiltonian consisting of single-particle, pairing and residual proton-neutron interaction terms. It is shown that the standard
proton-neutron quasiparticle random-phase approximation (pn-QRPA) is recovered, as a variational theory, by replacing quasiparticle pair creation and annihilation operators by bosons.
It is also shown that an exact, algebra preserving, mapping of the Hamiltonian is needed to describe the spectrum beyond the
QRPA phase transition. The role of the spurious components of the trial wave functions is discussed.
Received: 19 February 2002 / Accepted: 3 May 2002 相似文献
20.
R.R. Rodríguez-Guzmán J.L. Egido L.M. Robledo 《The European Physical Journal A - Hadrons and Nuclei》2003,17(1):37-47
The Angular Momentum Projected Generator Coordinate Method, with the quadrupole moment as collective coordinate and the Gogny
force (D1S) as the effective interaction, is used to describe the properties of the ground state and low-lying excited states
of the even-even neon isotopes 20-34Ne, that is, from the stability valley up to the drip line. It is found that the ground state of the N = 20 nucleus 30Ne is deformed but to a lesser extent than the N = 20 isotope of the magnesium. In the calculations, the isotope 32Ne is at the drip line in good agreement with other theoretical predictions. On the other hand, rather good agreement with
experimental data for many observables is obtained.
Received: 19 Novemeber 2002 / Accepted: 24 January 2003 / Published online: 8 April 2003 相似文献