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1.
Shell-model studies on the N =14 and 16 shell closures in neutron-rich Be, C, O and Ne isotopes are presented. We calculate, with the WBT interaction, the excited states in these nuclei. The calculations agree with recent experiment data. Excited energies and B(E2) values are displayed to discuss the shell closures. Our results support the N =16 shell closure in these isotopes, while indicating a disappearance of N =14 shell closure in Be and C isotopes. 相似文献
2.
Shell-model studies on the N=14 and 16 shell closures in neutron-rich Be, C, O and Ne isotopes are presented. We calculate, with the WBT interaction, the excited states in these nuclei. The calculations agree with recent experiment data. Excited energies and B(E2) values are displayed to discuss the shell closures. Our results support the N=16 shell closure in these isotopes, while indicating a disappearance of N=14 shell closure in Be and C isotopes. 相似文献
3.
A. S. Lalleman G. Auger W. Mittig M. Chabert M. Chartier J. Fermé A. Gillibert A. Lépine-Szily M. Lewitowicz M. H. Moscatello N. A. Orr G. Politi F. Sarazin H. Savajols P. Van Isacker A. C. C. Villari 《Hyperfine Interactions》2001,132(1-4):313-320
Mass measurements of the N=Z nuclei 80Zr, 76Sr, 68Se were performed for the first time and a new measurement was obtained for 80Y, using the second cyclotron CSS2 of GANIL as a high-resolution spectrometer. Ions around N=Z were produced by fusion-evaporation in the inverse 58Ni (4.32MeVA) + 24Mg and 12C reactions. New masses were measured by a time-of-flight method, with a precision of 2⋅10−6, by using well-known masses as references. Study of the double binding energy difference δV
np is then performed leading to a strong N=Z Wigner effect around N=Z=40. Knowledge of new masses in this region also plays a crucial role in the modelling of the astrophysical rp process.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
5.
Recent results and progress of mass measurements of neutron-rich nuclei utilizing Isochronous Mass Spectrometry (IMS) based on the HIRFL-CSR complex at Lanzhou are reported. The nuclei of interest were produced through projectile fragmentation of primary 86Kr ions at a realistic energy of 460.65 MeV/u. After in-flight separation by the fragment separator RIBLL2, the fragments were injected and stored in the experimental storage ring CSRe, and their masses were determined from measurements of their revolution times. The re-determined masses were compared and evaluated with other mass measurements, and the impact of these evaluated masses on the shell evolution study is discussed. 相似文献
6.
Sarazin F Savajols H Mittig W Nowacki F Orr NA Ren Z Roussel-Chomaz P Auger G Baiborodin D Belozyorov AV Borcea C Caurier E Dlouhy Z Gillibert A Lalleman AS Lewitowicz M Lukyanov SM de Oliveira F Penionzhkevich YE Ridikas D Sakurai H Tarasov O de Vismes A 《Physical review letters》2000,84(22):5062-5065
The masses of 31 neutron-rich nuclei in the range A = 29-47 have been measured. The precision of 19 masses has been significantly improved and 12 masses were measured for the first time. The neutron-rich Cl, S, and P isotopes are seen to exhibit a change in shell structure around N = 28. Comparison with shell model and relativistic mean field calculations demonstrate that the observed effects arise from deformed prolate ground state configurations associated with shape coexistence. Evidence for shape coexistence is provided by the observation of an isomer in 43S. 相似文献
7.
The study of neutron-rich nuclei near 132Sn is interesting and important for both nuclear structure and nuclear astrophysics. For a considerably large model space allowing cross-shell excitations, a new effective Hamiltonian is determined by employing the extended pairing-plus-quadrupole model with monopole corrections. Calculations for two mass regions, for the north-east quadrant of 132Sn with Z > 50 and N > 82 and for the south-west quadrant with Z < 50 and N < 82, have been performed recently. The structure of these nuclei is analyzed in detail, and the role of the monopole corrections canbe clearly seen. 相似文献
8.
W. Mittig H. Savajols D. Baiborodin J.M. Casandjian C.E. Demonchy P. Roussel-Chomaz F. Sarazin Z. Dlouhý J. Mrazek A.V. Belozyorov S.M. Lukyanov Y.E. Penionzhkevich N. Alamanos A. Drouart A. Gillibert C. Jouanne V. Lapoux E. Pollacco A. Korichi J.A. Scarpaci 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):157-160
Following mass measurements in the region N = 20 and N = 28, we have studied inelastic nuclear scattering for the nuclei 34Si, 33Al and 32Mg. No evidence for a low-lying shape isomeric 0+ state was found in 34Si, and an upper limit for the population cross-section could be established, rendering its existence very unlikely. A new
transition was found in 33Al, that is a good candidate for a 2p-2h state and therefore a determination of the 2p-2h gap at N = 20. Inelastic nuclear scattering strongly excites 3- states, as seen in 34Si. A strong transition was found in 32Mg that should correspond to the first 3- in this nucleus, lying very low as compared to theory and systematics in this region.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: mittig@ganil.fr 相似文献
9.
D. Lunney C. Monsanglant G. Audi G. Bollen C. Borcea H. Doubre C. Gaulard S. Henry M. deSaintSimon C. Thibault C. Toader N. Vieira 《Hyperfine Interactions》2001,132(1-4):297-305
The MISTRAL experiment (Mass measurements at ISOLDE with a Transmission and Radiofrequency spectrometer on-Line), conceived
for very short-lived nuclides, has reached the end of its commissioning phase. Installed in 1997, results have been obtained
consistent with all aspects of the projected spectrometer performance: nuclides with half-lives as short as 30 ms have been
measured and accuracies of 0.4 ppm have been achieved, despite the presence of a systematic shift and difficulties with isobaric
contamination. Masses of several nuclides, including 25–26Ne and 32Mg that forms the famous island of inversion around N=20, have been significantly improved.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
The shell evolution at N = 20, a disappearing neutron magic number observed experimentally in very neutron-rich nuclides, is investigated in the constrained relativistic mean field (RMF) theory. The trend of the shell closure observed experimentally towards the neutron drip-line can be reproduced. The predicted two-neutron separation energies, neutron shell gap energies and deformation parameters of ground states are shown as well. These results are compared with the recent Hartree-Fock-Bogliubov (HFB-14) model and the available experimental data. The perspective towards a better understanding of the shell evolution is discussed. 相似文献
11.
The shell evolution at N=20, a disappearing neutron magic number observed experimentally in very neutron-rich nuclides, is investigated in the constrained relativistic mean field (RMF) theory. The trend of the shell closure observed experimentally towards the neutron drip-line can be reproduced. The predicted two-neutron separation energies, neutron shell gap energies and deformation parameters of ground states are shown as well. These results are compared with the recent Hartree-Fock-Bogliubov (HFB-14) model and the available experimental data. The perspective towards a better understanding of the shell evolution is discussed. 相似文献
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13.
The shell effect is included in the improved isospin dependent quantum molecular dynamics model in which the shell correction energy of the system is calculated by using the deformed two-center shell model.A switch function is introduced to connect the shell correction energy of the projectile and the target with that of the compound nucleus during the dynamical fusion process.It is found that the calculated capture cross sections reproduce the experimental data quantitatively at the energy near the Coulomb... 相似文献
14.
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
15.
Yu. E. Penionzhkevich 《Hyperfine Interactions》2006,171(1-3):157-166
The present work reviews the properties of the neutron-rich isotopes near the closed shells N = 20 and N = 28. The changes in nuclear structure appearing as one goes away from the β-stability line are discussed. The location of
the neutron drip line and questions about the stability of nuclides with Z ≥ 8 are considered in connection with the weakening or even vanishing of the shell effects at the magic numbers 20 and 28,
and the discovery of the new neutron magic numbers at N = 16 and N = 32. These properties are extremely interesting from the point of view of laser experiments as well as for all other experimental
methods giving access to this region. 相似文献
16.
Magdalena Kowalska 《Hyperfine Interactions》2006,171(1-3):167-172
Collinear laser spectroscopy and β-NMR spectroscopy with optical pumping were applied at ISOLDE/CERN to measure for the first time the magnetic moments of neutron-rich
27Mg, 29Mg, 31Mg and 33Mg, along with the spins of the two latter. The magnetic moment of 27Mg was derived from its hyperfine structure detected in UV fluorescent light, whereas the nuclear magnetic resonance observed
in β-decay asymmetry from a polarised ensemble of nuclei gave the magnetic moment of 29Mg. For 31Mg and 33Mg, the hyperfine structure and nuclear magnetic resonance gave the spin and the magnetic moment. The preliminary results
for 27Mg and 29Mg are consistent with a large neutron shell gap at N=20, whereas data on 31Mg show that for this nucleus N=20 is not a magic number, which is also the case for 33Mg, based on preliminary analysis. Thus, the two latter isotopes belong to the “island of inversion.”
Magdalena Kowalska for the IS 427 collaboration at ISOLDE/CERN. 相似文献
17.
E. Galindo A. Jungclaus K.P. Lieb 《The European Physical Journal A - Hadrons and Nuclei》2000,9(4):439-451
The known level energies, electromagnetic moments and decay probabilities of high-spin states in the N = 46 isotones 86Zr, 87Nb, 88Mo, 89Tc, and 90Ru are interpreted within the shell model. The single-particle space was truncated to the p
1/2 and g
9/2 orbits (relative to the 88Sr core) and the single-particle energies and empirical two-body matrix elements derived by Gross and Frenkel were used in
the calculations. Based on the generally good success of this approach, energies and decay properties of the yrast spectra
in 90Ru and 91Rh are predicted.
Received: 31 July 2000 / Accepted: 18 December 2000 相似文献
18.
The interacting boson model with isospin (IBM-3) has been used to study the isospin excitation states and mixed symmetry states at low spin for 28Si. The theoretical calculations are in agreement with experimental data. The theoretical results show that the 81+ energy is 14.73 MeV. 相似文献
19.
The interacting boson model with isospin (IBM-3) has been used to study mixed symmetry states and electromagnetic transitions at low-lying states for a ^28Si nucleus. The theoretical calculations show that the 24^+ state is the lowest mixed symmetry state in ^28Si and the 43+ state is also a mixed symmetry state. 相似文献
20.
The interacting boson model with isospin (IBM-3) has been used to study mixed symmetry states and electromagnetic transitions at low-lying states for a 28Si nucleus. The theoretical calculations show that the 24+ state is the lowest mixed symmetry state in 28Si and the 43+ state is also a mixed symmetry state. 相似文献