Publications (133)297.91 Total impact
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ABSTRACT: Excited states have been studied in Na28 using the βdecay of implanted Ne28 ions at the Grand Accélérateur National d'Ions Lourds/LISE as well as the inbeam γray spectroscopy at the National Superconducting Cyclotron Laboratory/S800 facility. New states of positive (Jπ=3+,4+) and negative (Jπ=1  5) parity are proposed. The former arise from the coupling between 0d5/2 protons and 0d3/2 neutrons, while the latter are attributable to couplings of 0d5/2 protons with 1p3/2 or 0f7/2 neutrons. While the relative energies between the Jπ=1+4+ states are well reproduced with the USDA interaction in the N=17 isotones, a progressive shift in the groundstate binding energy (by about 500 keV) is observed between F26 and Al30. This points to a possible change in the protonneutron 0d5/20d3/2 effective interaction when moving from stability to the drip line. The presence of Jπ=1  4 negativeparity states around 1.5 MeV as well as of a candidate for a Jπ=5 state around 2.5 MeV give further support to the collapse of the N=20 gap and to the inversion between the neutron 0f7/2 and 1p3/2 levels below Z=12. These features are discussed in the framework of shellmodel and energydensityfunctional calculations, leading to predicted negativeparity states in the lowenergy spectra of the F26 and O25 nuclei.  [Show abstract] [Hide abstract]
ABSTRACT: The Isoscalar Giant Monopole Resonance (ISGMR) and the Isoscalar GiantDipole Resonance (ISGDR) compression modes have been studied in thedoublymagic unstable nucleus 56Ni. They were measured by inelastic αparticlescattering in inverse kinematics at 50 MeV/u with the MAYA active targetat the GANIL facility. The centroid of the ISGMR has been obtained atEx = 19.1 ± 0.5 MeV. Evidence for the lowlying part of the ISGDR has been found at Ex = 17.4 ± 0.7 MeV. The strength distribution for the dipolemode shows similarity with the prediction from the HartreeFock (HF) basedrandomphase approximation (RPA) [1]. These measurements confirm inelasticαparticle scattering as a suitable probe for exciting the ISGMR and the ISGDRmodes in radioactive isotopes in inverse kinematics.  [Show abstract] [Hide abstract]
ABSTRACT: Background: A large number of hypernuclei, where a considerable fraction of nucleons is replaced with strange baryons, and even pure hyperonic species are expected to be bound. However, the hypernuclear landscape remains largely unknown because of scarce constraints on the NY and YY interactions. Purpose: We want to estimate the number of potentially bound hypernuclei. To evaluate realistic error bars within the theoretical uncertainties associated with the spherical meanfield approach and the present information from already synthesized hypernuclei on the NY and YY channels, we limit ourselves to purely Λ hypernuclei, to magic numbers of Λ's (for Z≤120 and Λ≤70), and to eveneveneven systems. Method: We consider a densityfunctional approach adjusted to microscopic BrucknerHartreeFock calculations, where the ΛΛ term is corrected in a phenomenological way, to reproduce present experimental constraints. Different models which strongly deviate at large densities, but giving the same bond energy, are generated to take into account the uncertainties related to the highdensity equation of state. Results: The number of bound eveneveneven Λ hypernuclei is estimated to 491680±34400. This relatively low uncertainty is attributable to the fact that the wellconstrained lowdensity and highly unconstrained highdensity behavior of the energy functional turn out to be largely decoupled. Results in Λ hypernuclei appear to be almost independent of the choice for the highdensity part of the ΛΛ interaction. The location of the Λ hyperdriplines is also evaluated. Significant deviations from ironnickel elements can be found for Λ hypernuclei with the largest binding energy per baryon. Proton, neutron, and Λhyperon magicity evolution and triple magic Λ hypernuclei are studied. Possible bubble and halo effects in Λ hypernuclei are also discussed. Conclusions: The present results provide a first microscopic evaluation of the Λhypernuclear landscape. They shall benefit from the more and more accurate design of the Λbased functionals. The measurements of Λ and multiΛ hypernuclei together with additional constraints of the ΞΛ and ΞΞ interaction are mandatory to improve such critical information.  [Show abstract] [Hide abstract]
ABSTRACT: Isoscalar giant resonances have been measured in the unstable Ni68 nucleus using inelastic alpha and deuteron scattering at 50A MeV in inverse kinematics with the active target MAYA at GANIL. Using alpha scattering, the extracted isoscalar giant monopole resonance (ISGMR) centroid was determined to be 21.1±1.9 MeV and the isoscalar giant quadrupole resonance (ISGQR) to be 15.9±1.3 MeV. Indications for soft isoscalar monopole and dipole modes are provided. Results obtained with both (α,α′) and (d,d′) probes are compatible. The evolution of isoscalar giant resonances along the Ni isotopic chain from Ni56 to Ni68 is discussed. 
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ABSTRACT: Spinorbit coupling characterizes quantum systems such as atoms, nuclei, hypernuclei, quarkonia, etc., and is essential for understanding their spectroscopic properties. Depending on the system, the effect of spinorbit coupling on shell structure is large in nuclei, small in quarkonia, perturbative in atoms. In the standard nonrelativistic reduction of the singleparticle Dirac equation, we derive a universal rule for the relative magnitude of the spinorbit effect that applies to very different quantum systems, regardless of whether the spinorbit coupling originates from the strong or electromagnetic interaction. It is shown that in nuclei the near equality of the mass of the nucleon and the difference between the large repulsive and attractive potentials explains the fact that spinorbit splittings are comparable to the energy spacing between major shells. For a specific ratio between the particle mass and the effective potential whose gradient determines the spinorbit force, we predict the occurrence of giant spinorbit energy splittings that dominate the singleparticle excitation spectrum. 
Article: The hypernuclear chart
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ABSTRACT: We calculate the comprehensive hypernuclear chart for eveneven hypernuclei with magic numbers of $\Lambda$'s (for Z $\leq$ 120 and $\Lambda \leq$70) and estimate the number of bound systems, considering the present uncertainties in the $\Lambda$nucleon and $\Lambda\Lambda$ interactions. We consider a density functional approach adjusted to microscopic BrucknerHartreeFock calculations, where the $\Lambda\Lambda$ term is corrected in a phenomenological way, to reproduce present experimental constraints. Different models which strongly deviate at large densities, but giving the same bond energy, are generated in order to take into account the uncertainties related to the high density equation of state. The number of bound eveneveneven hypernuclei is estimated to 491680 $\pm$ 34400. This relatively low uncertainty is due to the fact that the well constrained low density and highly unconstrained high density behavior of the energy functional turn out to be largely decoupled. Results in hypernuclei appear to be almost independent of the choice for the highdensity part of the $\Lambda\Lambda$ interaction. The location of the hyperdriplines is also evaluated. Significant deviations from IronNickel elements can be found for hypernuclei with the largest binding energy per baryon. Proton, neutron and hyperon magicity evolution and triple magic hypernuclei are studied. Possible bubbles and haloes effect in hypernuclei are also discussed. The present results provide a first microscopic evaluation of the hypernuclear landscape. 
Dataset: ncomms7743supplementary information
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ABSTRACT: Excited states in $^{28}$Na have been studied using the $\beta$decay of implanted $^{28}$Ne ions at GANIL/LISE as well as the inbeam $\gamma$ray spectroscopy at the NSCL/S800 facility. New states of positive (J$^{\pi}$=3,4$^+$) and negative (J$^{\pi}$=15$^$) parity are proposed. The former arise from the coupling between 0d$\_{5/2}$ protons and a 0d$\_{3/2}$ neutron, while the latter are due to couplings with 1p$\_{3/2}$ or 0f$\_{7/2}$ neutrons. While the relative energies between the J$^{\pi}$=14$^+$ states are well reproduced with the USDA interaction in the N=17 isotones, a progressive shift in the ground state binding energy (by about 500 keV) is observed between $^{26}$F and $^{30}$Al. This points to a possible change in the protonneutron 0d$\_{5/2}$0d$\_{3/2}$ effective interaction when moving from stability to the drip line. The presence of J$^{\pi}$=14$^$ negative parity states around 1.5 MeV as well as of a candidate for a J$^{\pi}$=5$^$ state around 2.5 MeV give further support to the collapse of the N=20 gap and to the inversion between the 0f$\_{7/2}$ and 1p$\_{3/2}$ levels below Z=12. These features are discussed in the framework of Shell Model and EDF calculations, leading to predicted negative parity states in the low energy spectra of the $^{26}$F and $^{25}$O nuclei.  [Show abstract] [Hide abstract]
ABSTRACT: Giant resonances are collective excitation modes for manybody systems of fermions governed by a mean field, such as the atomic nuclei. The microscopic origin of such modes is the coherence among elementary particlehole excitations, where a particle is promoted from an occupied state below the Fermi level (hole) to an empty one above the Fermi level (particle). The same coherence is also predicted for the particle–particle and the hole–hole excitations, because of the basic quantum symmetry between particles and holes. In nuclear physics, the giant modes have been widely reported for the particle–hole sector but, despite several attempts, there is no precedent in the particle–particle and hole–hole ones, thus making questionable the aforementioned symmetry assumption. Here we provide experimental indications of the Giant Pairing Vibration, which is the leading particle–particle giant mode. An immediate implication of it is the validation of the particle–hole symmetry.  [Show abstract] [Hide abstract]
ABSTRACT: Nuclear states are often described as quantum liquid states. Using the localisation parameter, it is possible to understand cluster states in nuclei as hybrid states between quantum liquid and crystal states. Recent calculations discussing the effect of the depth of the confining potential, as well as various lengthscales ratios, are presented in order to provide a complementary view on the cluster phenomenon in nuclei.  [Show abstract] [Hide abstract]
ABSTRACT: Nuclear Energy Density Functionals (EDFs) are a microscopic tool of choice extensively used over the whole chart to successfully describe the properties of atomic nuclei ensuing from their quantum liquid nature. In the last decade, they also have proved their ability to deal with the cluster phenomenon, shedding a new light on its fundamental understanding by treating on an equal footing both quantum liquid and cluster aspects of nuclei. Such a unified microscopic description based on nucleonic degrees of freedom enables to tackle the question pertaining to the origin of the cluster phenomenon and emphasizes intrinsic mechanisms leading to the emergence of clusters in nuclei.  [Show abstract] [Hide abstract]
ABSTRACT: We study the finite temperature HartreeFockBCS approximation for selected stable Sn nuclei with zerorange Skyrme forces. Hartree Fock BCS approximation allows for a straightforward interpretation of the results since it involves $u$ and $v$'s which are not matrices as in HFB. Pairing transitions from superfluid to the normal state are studied with respect to the temperature. The temperature dependence of the nuclear radii and neutron skin are also analyzed. An increase of proton and neutron radii is obtained in neutron rich nuclei especially above the critical temperature. Using different Skyrme energy functionals, it is found that the correlation between the effective mass in symmetric nuclear matter and the critical temperature depends on the pairing prescription. The temperature dependence of the nucleon effective mass is also investigated, showing that proton and neutron effective masses display different behavior below and above the critical temperature, due to the small temperature dependence of the density. 
Article: Pairing properties of hot nuclei within the finite temperature Hartree Fock+BCS approximation
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ABSTRACT: In this work, finite temperature Hartree Fock BCS (FT+HFBCS) calculations are performed in Sn isotopes with the zerorange Skyrme type interactions. Vanishing of pairing correlations due to the increase in temperature are investigated with various types of Skyrme interactions. In addition, dependence of the critical temperature with respect to the several properties of these energy density functionals are analysed. 
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ABSTRACT: The isoscalar monopole response has been measured in the unstable nucleus ^{68}Ni using inelastic alpha scattering at 50A MeV in inverse kinematics with the active target MAYA at GANIL. The isoscalar giant monopole resonance (ISGMR) centroid was determined to be 21.1±1.9 MeV and indications for a soft monopole mode are provided for the first time at 12.9±1.0 MeV. Analysis of the corresponding angular distributions using distortedwaveborn approximation with randomphase approximation transition densities indicates that the L=0 multipolarity dominates the cross section for the ISGMR and significantly contributes to the lowenergy mode. The L=0 part of this lowenergy mode, the soft monopole mode, is dominated by neutron excitations. This demonstrates the relevance of inelastic alpha scattering in inverse kinematics in order to probe both the ISGMR and isoscalar soft modes in neutronrich nuclei. 
Article: Study of new resonances at high excitation energy by the 120 Sn(p,t) 118 Sn reaction at 35 MeV
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ABSTRACT: The 120Sn(p,t)118Sn reaction was investigated at 35 MeV incident energy. The 118Sn excitation energy spectrum was reconstructed up to about 16 MeV. Preliminary results show the presence of a broad resonance at high excitation energy, compatible with the predicted population of the Giant Pairing Vibration (GPV). 
Article: Effects of the tensor force on the ground and first $2^{+}$ states of the magic $^{54}$Ca nucleus
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ABSTRACT: The magic nature of the $^{54}$Ca nucleus is investigated in the light of the recent experimental results. We employ both HFB and HF+BCS methods using Skyrmetype SLy5, SLy5+T and T44 interactions. The evolution of the singleparticle spectra is studied for the N=34 isotones: $^{60}$Fe, $^{58}$Cr, $^{56}$Ti and $^{54}$Ca. An increase is obtained in the neutron spinorbit splittings of $p$ and $f$ states due to the effect of the tensor force which also makes $^{54}$Ca a magic nucleus candidate. QRPA calculations on top of HF+BCS are performed to investigate the first $J^{\pi}$=$2^{+}$ states of the calcium isotopic chain. A good agreement for excitation energies is obtained when we include the tensor force in the meanfield part of the calculations. The first $2^{+}$ states indicate a subshell closure for both $^{52}$Ca and $^{54}$Ca nuclei. We confirm that the tensor part of the interaction is quite essential in explaining the neutron subshell closure in $^{52}$Ca and $^{54}$Ca nuclei.  [Show abstract] [Hide abstract]
ABSTRACT: The framework of nuclear energy density functionals is applied to a study of the formation and evolution of cluster states in nuclei. The relativistic functional DDME2 is used in triaxial and reflectionasymmetric relativistic HartreeBogoliubov calculations of relatively light $N = Z$ and neutronrich nuclei. The role of deformation and degeneracy of singlenucleon states in the formation of clusters is analysed, and interesting cluster structures are predicted in excited configurations of Be, C, O, Ne, Mg, Si, S, Ar and Ca $N = Z$ nuclei. Cluster phenomena in neutronrich nuclei are discussed, and it is shown that in neutronrich Be and C nuclei cluster states occur as a result of molecular bonding of $\alpha$particles by the excess neutrons, and also that proton covalent bonding can occur in $^{10}$C.  [Show abstract] [Hide abstract]
ABSTRACT: Expérience GANIL/LISE/MAYA
Publication Stats
2k  Citations  
297.91  Total Impact Points  
Top Journals
Institutions

20022015

Université ParisSud 11
 Institut de Physique Nucléaire (IPN)
Orsay, ÎledeFrance, France


2013

Yildiz Technical University
 Department of Physics
İstanbul, Istanbul, Turkey


20002012

Institut de Physique Nucléaire de Lyon
Lyons, RhôneAlpes, France


20002010

French National Centre for Scientific Research
Lutetia Parisorum, ÎledeFrance, France


1998

Orsay Physics
Fuveau, ProvenceAlpesCôte d'Azur, France
