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Nuclar ‘’BUBBLE’’ structure in 34 Si IPNO Participation: M. Grasso, E. Khan, N. Van Giai Collaboration : CEA DAM DIF F-91297 Arpajon, France, GANIL, France, Florida State University, USA, Zagreb University, Croatia Les noyaux avec des structures à bulles sont caractérises par des densités très creusées au centre. Des prédictions sur leur existence sont effectuées avec trois modèles théoriques : le modèle en couches et les champs moyens relativiste et non relativiste. Un accord de tous les modèles indique le noyau 34 Si comme possible candidat pour une structure à bulle, avec une déplétion de la densité centrale protonique de 40%. The bubble structure characterizes atomic nuclei having a central density depletion.. This phenomenon has been discussed for many decades, starting from the work of Wilson in the 40s [1] for the study of low-energy excitations as oscillations of bubbles up to the first microscopic calculations of Campi and Sprung in the 70s [2]. More recently, bubbles have been discussed in superheavy and hyperheavy nuclei [3]. The perspective of producing more exotic nuclei with the new generation of RIB facilities has led to a revived interest in the subject. The s orbits have the only radial distributions peaked in the interior of the nucleus, their wave function extending further to the surface according to their number of nodes. Orbits with increasing angular momenta are more localized at the nuclear surface. Therefore, the non filling of s orbits is expected to provoke a central depletion of the nucleon density. A suitable region of the chart of nuclides to search for a proton bubble is found for the N=20 isotones. Between Z=20 and Z=16 the s1/2 orbit is separated by about 6.5 MeV from the lower d5/2 orbit and 2.5 MeV from the upper d3/2 orbit, forming two subshell closures at Z=14 and Z=16, respectively [4]. In addition, the N=20 shell closure is rigid enough for these nuclei to hamper significant coupling to collective states. Following the sequential filling of the proton orbits, 34 Si should not contain any proton in the 2s1/2 orbit, whereas 36 S should contain 2 protons there. This would lead to an important change in the proton density distribution between the nuclei 36 S and 34 Si and make the 34 Si a bubble nucleus. The work in Ref. [5] aimed at determining, using various theoretical approaches (shell model, relativistic and non relativistic mean field), whether the 34 Si could actually be considered as good proton bubble nucleus. As an illustration, the HF proton density profiles, obtained with the Skyrme parametrization SLy4 and calculated in 34 Si and 36 S (where the s state is occupied), are shown in Fig. 1. The depletion fraction F of the density is ~ 38\%, where: F Fig 1. Proton densities of 34 Si and 36 S max max central Similar results have been found with all the other models. These results indicate that 34 Si is a good candidate for a bubble density profile. The measurement of the charge density in this nucleus should be undertaken, for instance by electron scattering in a exotic beam collider such as EXL in FAIR and RIBF in Riken. The study of 34 Si, either by high energy proton scattering to study the matter density profile, or by direct reactions to yield the spectroscopic factors and the low-energy excitation spectrum is presently possible. For the 61
transfer reaction, the 34 Si(d, 3 He) 33 Al reaction channel should be used to determine if the occupancy of the s proton orbit has dropped to zero in 34 Si. This would confirm the shell model predictions of Ref. [5] and provide a strong signal for a central density depletion of ~ 40%. References: [1] H.A. Wilson, Phys. Rev. 69, 538 (1946) [2] X. Campi and W.L. Sprung, Phys. Lett. B 46, 291 (1973) [3] M. Bender, et al., Phys. Rev. C 60, 034304 (1999); J. Dechargé, et al., Nucl. Phys. A 716, 55 (2003) [4] O. Sorlin and M.-G. Porquet, Prog. Part. Nucl. Phys. 61, 602 (2008) [5] M. Grasso, et al., Phys. Rev. C 79, 034318 (2009) 62
Page 1 and 2: EXOTIC NUCLEI STRUCTURE AND REACTIO
Page 3 and 4: in the spectra by analyzing their t
Page 5 and 6: were taken from ref. [5]. Concernin
Page 7 and 8: keV -ray with the particles and the
Page 9 and 10: the 605.9 keV line of the 74 Zn 2+
Page 11 and 12: Figure 2 a n d analysis. Figure 2 s
Page 13 and 14: ing particles was thus obtained by
Page 15 and 16: First p-p p collisions in the ALICE
Page 17 and 18: Quarkonia physics with ALICE IPNO P
Page 19 and 20: NA50 updated puzzle IPNO Participat
Page 21 and 22: Status of the HADES experiment (I):
Page 23 and 24: Status of the HADES experiments (II
Page 25 and 26: Status of the HADES experiment (III
Page 27 and 28: Hadron physics in pbar-p p annihila
Page 29 and 30: Hadron Electrodynamics IPNO Partici
Page 31 and 32: G0 experiment at Jefferson Lab. IPN
Page 33 and 34: GEp-III and GEp-2 at Jefferson Lab
Page 35 and 36: Exotic low mass narrow baryons from
Page 37 and 38: The PVA4 parity violation experimen
Page 39 and 40: Etude des Distributions de Partons
Page 41 and 42: Latest Results from GRAAL IPNO Part
Page 43 and 44: Persistence of the Polarization in
Page 45 and 46: The northern site of the Pierre Aug
Page 47 and 48: The Pierre Auger southern Observato
Page 49 and 50: In figure 4 we plot the differentia
Page 51: THEORETICAL PHYSICS Research in the
Page 55 and 56: Collective excitations with SKYRME
Page 57 and 58: Pairing and nuclear incompressibili
Page 59 and 60: Pairing properties in nuclei and in
Page 61 and 62: Evaporation-residue residue cross s
Page 63 and 64: Extending the VMI model: normal and
Page 65 and 66: Alpha particle condensation in nucl
Page 67 and 68: Collective Modes in Ultracold Trapp
Page 69 and 70: Exploring key unknown neutrino prop
Page 71 and 72: Relic astrophysical and cosmologica
Page 73 and 74: After a term by term Borel resummat
Page 75 and 76: Chiral expansions of the π 0 lifet
Page 77 and 78: IPNO Participation: H. Sazdjian Eff
Page 79 and 80: fer is used to extract f + (0). We
Page 81 and 82: cleon. The spectrum becomes strongl
Page 83 and 84: A pseudo Coulombian potential in D=
Page 85 and 86: The many-body problem with an energ
Page 87 and 88: The rotational spectrum and the att
Page 89 and 90: Z-identification of very heavy nucl
Page 91 and 92: The Pegase project, a new solid sur
Page 93 and 94: But at 80 keV total energy ( 200 eV
Page 95 and 96: Isospin effects on fragment and par
Page 97 and 98: Radial collective energy and fragme
Page 99 and 100: Latent heat of the phase transition
Page 101 and 102: Alpha-particle particle condensatio
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Fluo X: Deexcitation time measureme
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ENERGY AND ENVIRONMENT The increasi
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toe/cap/y which energy access inequ
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nides. A global comparison can be p
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3D coupling of Monte-Carlo neutroni
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Fission cross sections of actinides
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Studies and synthesis of specific m
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Chemistry and Electrochemistry of T
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function of temperature. The recent
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global electron number of the redox
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(D 0 /D)-1 ln complexes of Pa(V). I
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