Publications (112)290.13 Total impact

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. 
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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.Nature Communications 03/2015; 6. DOI:10.1038/ncomms7743 · 10.74 Impact Factor 
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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.Journal of Physics Conference Series 12/2014; 569(1). DOI:10.1088/17426596/569/1/012028 
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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.Journal of Physics Conference Series 12/2014; 569(1). DOI:10.1088/17426596/569/1/012006 
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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.European Physical Journal A 10/2014; 50(10):160. DOI:10.1140/epja/i2014141604 · 2.42 Impact Factor 
Article: Pairing properties of hot nuclei within the finite temperature Hartree Fock+BCS approximation
Journal of Physics Conference Series 09/2014; 533:012019. DOI:10.1088/17426596/533/1/012019 
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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.Physical Review Letters 07/2014; 113(3):032504. DOI:10.1103/PhysRevLett.113.032504 · 7.73 Impact Factor 
Article: Study of new resonances at high excitation energy by the 120 Sn(p,t) 118 Sn reaction at 35 MeV
07/2014; 78(7):802804. DOI:10.7868/S0367676514070199 
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.Physical Review C 06/2014; 89(6):064322. DOI:10.1103/PhysRevC.89.064322 · 3.88 Impact Factor 
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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.Physical Review C 06/2014; 90(5). DOI:10.1103/PhysRevC.90.054329 · 3.88 Impact Factor 
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ABSTRACT: The role of saturation for cluster formation in atomic nuclei is analyzed by considering three lengthscale ratios and performing deformationconstrained selfconsistent meanfield calculations. The effect of clusterization in deformed light systems is related to the saturation property of the internucleon interaction. The formation of clusters at low nucleon density is illustrated by expanding the radius of O16 in a constrained calculation. A phase diagram shows that the formation of clusters can be interpreted as a hybrid state between the crystal and the liquid phases. In the hybrid cluster phase the confining potential attenuates the delocalization generated by the effective nuclear interaction.Physical Review C 03/2014; 89(3):031303. DOI:10.1103/PhysRevC.89.031303 · 3.88 Impact Factor 
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ABSTRACT: Recent results obtained with energy density functional (EDF) based methods are presented, focused on the nuclear phenomenology. EDF approaches aim for an universal description of the nuclear phenomena over the nuclear chart. Achievements from large to small nuclear systems are depicted: equation of state of nuclear matter, heavy and light nuclei. Dynamical aspects such as nuclear excitations, decay and reactions are also presented. EDF methods are progressing towards an unified and systematic description of the rich variety of the nuclear phenomena such as quantum liquid and cluster states, or nuclear structure and reactions.The European Physical Journal Conferences 02/2014; 66. DOI:10.1051/epjconf/20146601009 
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ABSTRACT: The role of superfluidity on the symmetry energy and on the incompressibility is studied in nuclear matter and finite nuclei employing HartreeFockBogoliubov modeling based on several types of pairing interactions (surface, mixed and isovectordensity dependent). It is observed that, while pairing has only a marginal effect on the symmetry energy and on the incompressibility at saturation density, the effects are significantly larger at lower densities.European Physical Journal A 01/2014; 50(2). DOI:10.1140/epja/i2014140189 · 2.42 Impact Factor 
Acta Physica Polonica Series B 01/2014; 45(2):437. DOI:10.5506/APhysPolB.45.437 · 1.00 Impact Factor

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ABSTRACT: The isoscalar monopole response is studied in doubly magic 208Pb, 100,132Sn nuclei using the Skyrme HF+RPA model. A lowenergy strength is predicted and corresponds to almost pure singleparticle excitations. These pure singleparticle excitations allow to analyse the splitting of the corresponding spinorbit partners. A good agreement with the spinorbit splitting data is found in the case of 208Pb. The experimental width of the giant monopole resonance may hinder the measurement of the soft monopole mode.European Physical Journal A 10/2013; 49(124):18. DOI:10.1140/epja/i2013131246 · 2.42 Impact Factor 
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ABSTRACT: The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, protonrich isotopes cannot be formed during those processes, because they are shielded from the sprocess flow and rprocess betadecay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or timereversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes. 
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ABSTRACT: Background: The determination of the density dependence of the nuclear incompressibility can be investigated using the isoscalar giant monopole resonance.Purpose: The importance of the socalled crossing density at subsaturation density is underlined.Methods: The measurements of the isoscalar giant monopole resonance (GMR), also called the breathing mode, are analyzed with respect to their constraints on the quantity M_{c}, e.g., the density dependence of the nuclear incompressibility around the socalled crossing density ρ_{c}=0.1 fm^{−3}.Results: The correlation between the centroid of the GMR, E_{GMR}, and M_{c} is shown to be more accurate than the one between E_{GMR} and the incompressibility modulus at saturation density, K_{∞}, giving rise to an improved determination on the nuclear equation of state. The relationship between M_{c} and K_{∞} is given as a function of the skewness parameter Q_{∞} associated with the density dependence of the equation of state. The large variation of Q_{∞} among different energy density functionals directly impacts the knowledge of K_{∞}: A better knowledge of Q_{∞} is required to deduce more accurately K_{∞}. Using the local density approximation, a simple and accurate expression relating E_{GMR} and the quantity M_{c} is derived and successfully compared to the fully microscopic predictions.Conclusions: The measurement of the GMR constrains the slope of the incompressibility M_{c} at the crossing density rather than the incompressibility modulus at the saturation density.Physical Review C 09/2013; 88(3). DOI:10.1103/PhysRevC.88.034319 · 3.88 Impact Factor 
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ABSTRACT: The incompressibility of finite fermionic systems is investigated using analytical approaches and microscopic models. The incompressibility of a system is directly linked to the zeropoint kinetic energy of constituent fermions, and this is a universal feature of fermionic systems. In the case of atomic nuclei, this implies a constant value of the incompressibility in mediumheavy and heavy nuclei. The evolution of nuclear incompressibility along Sn and Pb isotopic chains is analyzed using global microscopic models, based on both nonrelativistic and relativistic energy functionals. The result is an almost constant incompressibility in stable nuclei and systems not far from stability, and a steep decrease in nuclei with pronounced neutron excess, caused by the emergence of a soft monopole mode in neutronrich nuclei.Physical Review C 06/2013; 87:064311. DOI:10.1103/PhysRevC.87.064311 · 3.88 Impact Factor 
Article: Towards a better knowledge of the nuclear equation of state from the isoscalar breathing mode
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ABSTRACT: The measurements of the isoscalar giant monopole resonance (GMR), also called the breathing mode, are analyzed with respect to their constraints on the quantity $M_c$, e.g. the density dependence of the nuclear incompressibility around the socalled crossing density $\rho_c$=0.1 fm$^{3}$. The correlation between the centroid of the GMR, $E_\mathrm{GMR}$, and $M_c$ is shown to be more accurate than the one between $E_\mathrm{GMR}$ and the incompressibility modulus at saturation density, $K_\infty$, giving rise to an improved determination on the nuclear equation of state. The relationship between $M_c$ and $K_\infty$ is given as a function of the skewness parameter $Q_\infty$ associated to the density dependence of the equation of state. The large variation of $Q_\infty$ among different energy density functionnals directly impacts the knowledge of $K_\infty$: a better knowledge of $Q_\infty$ is required to deduce more accurately $K_\infty$. Using the Local Density Approximation, a simple and accurate expression relating $E_\mathrm{GMR}$ and the quantity $M_c$ is derived and successfully compared to the fully microscopic predictions.
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1k  Citations  
290.13  Total Impact Points  
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 Physical Review C (23)
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Institutions

2004–2014

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


2013

Yildiz Technical University
 Department of Physics
İstanbul, Istanbul, Turkey


2000–2012

Institut de Physique Nucléaire de Lyon
Lyons, RhôneAlpes, France 
University of Milan
Milano, Lombardy, Italy


2002–2010

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


1998

Orsay Physics
Fuveau, ProvenceAlpesCôte d'Azur, France
