M. G. Porquet

Cea Leti, Grenoble, Rhône-Alpes, France

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Publications (182)270.53 Total impact

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    ABSTRACT: Odd-odd 138La nuclei have been produced in the 12C+238U fusion-fission reaction and their γ rays studied with the Euroball array. The high-spin level scheme has been built up to ̃4.5 MeV excitation energy and spin I ̃16ℏ from the triple γ-ray coincidence data. An isomeric state lying at 739-keV excitation energy has been identified. The configurations of the structures are first discussed by analogy with the proton excitations identified in the semimagic 139La82 nucleus, which involve the three high-j orbits lying above the Z =50 gap, πg7/2, πd5/2, and πh11/2. The competition of these three orbits to produce the yrast line is confirmed by the results of shell-model calculations performed in this work.
    02/2014; 89(3).
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    ABSTRACT: The 124-131Te nuclei have been produced as fission fragments in two fusion reactions induced by heavy-ions (12C + 238U at 90 MeV bombarding energy and 18O + 208Pb at 85 MeV) and studied with the Euroball array. Their high-spin level schemes have been extended to higher excitation energy from the triple gamma-ray coincidence data. The gamma-gamma angular correlations have been analyzed in order to assign spin and parity values to many observed states. Moreover the half-lives of isomeric states have been measured from the delayed coincidences between the fission-fragment detector SAPhIR and Euroball, as well as from the timing information of the Ge detectors. The behaviors of the yrast structures identified in the present work are first discussed in comparison with the general features known in the mass region, particularly the breakings of neutron pairs occupying the nuh11/2 orbit identified in the neighboring Sn nuclei. The experimental level schemes are then compared to shell-model calculations performed in this work. The analysis of the wave functions shows the effects of the proton-pair breaking along the yrast lines of the heavy Te isotopes.
    12/2013;
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    ABSTRACT: The /EC decay of 185Tl was studied at the ISOLDE facility, the -rays belonging to 185Hg have been identified and a partial low-spin level scheme of 185Hg has been built. The decay of 185m+gHg was studied at the ISOCELE facility. Conversion electron lines of very low-energy transitions were observed for the first time. Electron data have been obtained for four transitions in 185Au and two transitions in 185Hg . From the analysis performed using an internal energy calibration procedure the energy location of the 185mHg has been determined to be keV. This value is consistent with that determined independently, keV, using 185m+gHg -decay data from literature. New particles emitted from 189m+gPb have been detected and their origins determined by in-source laser spectroscopy at the ISOLDE facility. - coincidence results have served to locate the isomeric state of 189Pb at keV. This latter value added to -decay data from literature have allowed the energy location of the isomeric states of 193Po and 197Rn at 95(7)keV and 194(12)keV, respectively. The nuclear structure of the isomeric and ground states in the nuclei of the three -emitter chains starting with 195m+g, 197m+g, 199m+gRn are discussed.
    European Physical Journal A 09/2013; · 2.42 Impact Factor
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    ABSTRACT: The high-spin states of the two neutron-rich nuclei 88Kr52 and 89Rb52 have been studied from the 18O+208Pb fusion-fission reaction. Their level schemes were built from triple γ-ray coincidence data, and γ-γ angular correlations were analyzed in order to assign spin and parity values to most of the observed states. The two level schemes evolve from collective structures to single-particle excitations as a function of the excitation energy. Comparison with results of shell-model calculations gives the specific proton and neutron configurations which are involved to generate the angular momentum along the yrast lines.
    Physical Review C 08/2013; 88(2). · 3.72 Impact Factor
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    A. Astier, M. -G. Porquet
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    ABSTRACT: The close similarity between the shell structures in the 132Sn and 208Pb regions is a well known phenomenon. Thus, using the correspondence between the high-j orbits located above the Z=50 and Z=82 shell gaps, we discuss the evolutions of the fully aligned states with one broken proton pair in the N=82 and N=126 isotones. A long-lived isomeric state was discovered in 217Pa more than thirty years ago and despite two other experiments giving new experimental results, the discussions on its main properties (spin, parity, configuration) remained inconclusive. Then, using the comparison with the I^\pi=17/2^+ isomeric state recently measured in 139La, the isomeric state of 217Pa is assigned as the fully aligned state of the (\pi h_{9/2})^2(\pi f_{7/2})^1 configuration.
    Physical Review C 05/2013; 87(1). · 3.72 Impact Factor
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    ABSTRACT: Odd-odd 136Cs nuclei have been produced in the 18O+208Pb and 12C+238U fusion-fission reactions and their γ rays studied with the Euroball array. The high-spin level scheme was built up to ∼4.7 MeV excitation energy and spin I∼16ℏ from the triple γ-ray coincidence data. The configurations of the three structures observed above ∼2 MeV excitation energy are first discussed by analogy with the proton excitations identified in the semimagic 137Cs82 nucleus, which involve the three high-j orbits lying above the Z=50 gap, πg7/2, πd5/2, and πh11/2. This is confirmed by the results of shell-model calculations performed in this work.
    Physical Review C 05/2013; 87(5). · 3.72 Impact Factor
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    O. Sorlin, M. -G. Porquet
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    ABSTRACT: The evolution of the N=28 shell closure is investigated far from stability. Using the latest results obtained from various experimental techniques, we discuss the main properties of the N=28 isotones, as well as those of the N=27 and N=29 isotones. Experimental results are confronted to various theoretical predictions. These studies pinpoint the effects of several terms of the nucleon-nucleon interaction, such as the central, the spin-orbit, the tensor and the three-body force components, to account for the modification of the N=28 shell gap and spin-orbit splittings. Analogies between the evolution of the N=28 shell closure and other magic numbers originating from the spin-orbit interaction are proposed (N=14,50, 82 and 90). More generally, questions related to the evolution of nuclear forces towards the drip-line, in bubble nuclei, and for nuclei involved in the r-process nucleosynthesis are proposed and discussed.
    Physica Scripta Volume T. 09/2012;
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    ABSTRACT: Five N=82 isotones have been produced in two fusion-fission reactions and their γ rays studied with the Euroball array. The high-spin states of 139La have been identified, while the high-spin yrast and near-to-yrast structures of the four others have been greatly extended. From angular correlation analysis, spin values have been assigned to some states of 136Xe and 137Cs. Several cascades involving γ rays of 139La have been found to be delayed; they deexcite an isomeric state with T1/2=315(35) ns located at 1800 keV excitation energy. The excited states of these five N=82 isotones are expected to be due to various proton excitations involving the three high-j subshells located above the Z=50 shell closure. This is confirmed by the results of shell-model calculations performed in this work. In addition, high-spin states corresponding to the excitation of the neutron core have been unambiguously identified in 136Xe, 137Cs, and 138Ba.
    Physical Review C 06/2012; 85(6). · 3.72 Impact Factor
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    ABSTRACT: The intraband electromagnetic transitions in 210Po and 210Pb are well described within the shell model approach. In contrast, similar transitions in 212Po are one order of magnitude smaller than the experimental values, suggesting the existence of an α-cluster component in the structure of this nucleus. To probe this assumption we introduced Gaussian-like components in the single-particle orbitals. We thus obtained an enhancement of intraband transitions, as well as a proper description of the absolute α-decay width in 212Po. We analyzed the recently measured unnatural parity states I− in 212Po in terms of the collective octupole excitation in 208Pb coupled to positive parity states in 210Pb. They are connected by relatively large dipole transitions to yrast positive natural parity states. We described E1 transitions by using the same α-cluster component and an effective neutron dipole charge eν=−eZ/A. B(E2) values and absolute α-decay width in 212Po are simultaneously described within the shell model plus a cluster component depending upon one free strength parameter.
    Physical Review C 06/2012; 85(6). · 3.72 Impact Factor
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    ABSTRACT: The 119–126Sn nuclei have been produced as fission fragments in two reactions induced by heavy ions: 12C+238U at a bombarding energy of 90 MeV and 18O+208Pb at 85 MeV. Their level schemes have been built from γ rays detected using the Euroball array. High-spin states located above the long-lived isomeric states of the even- and odd-A 120–126Sn nuclei have been identified. Moreover, isomeric states lying around 4.5 MeV have been established in 120,122,124,126Sn from the delayed coincidences between the fission fragment detector SAPhIR and the Euroball array. The states located above 3 MeV excitation energy are ascribed to several broken pairs of neutrons occupying the νh11/2 orbit. The maximum value of angular momentum available in such a high-j shell, i.e., for midoccupation and the breaking of the three neutron pairs, has been identified. This process is observed for the first time in spherical nuclei.
    Physical Review C 05/2012; 85(5). · 3.72 Impact Factor
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    ABSTRACT: In this paper we formulate and discuss the strategy of constructing theories capable of providing not only the numerical predictions sensu stricto but also the distributions of probability that such predictions apply in the predefined physics context. Examples of applications of the presented ideas are illustrated using as a choice the nuclear mean-field theory with two realistic realizations of the underlying Hamiltonians: Phenomenological Woods-Saxon and self-consistent Skyrme-Hartree-Fock.
    International Journal of Modern Physics E 05/2012; 21(5):50053-. · 0.63 Impact Factor
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    ABSTRACT: The 104,106,108Ru nuclei have been produced as fission fragments following the fusion reaction 28Si + 176Yb at 145 MeV bombarding energy; prompt gamma rays emitted in the reaction were detected using the Eurogam II array. Their high-spin level schemes have been obtained, particularly several side bands have been extended or newly observed. Experimental results are discussed in the framework of both collective model and the rotating mean-field approach in which the Gogny force is the sole input. These calculations provide very good descriptions of both low-spin and high-spin structures observed in the neutron-rich even-A Ru isotopes.
    European Physical Journal A 04/2012; 8(2):177-185. · 2.42 Impact Factor
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    ABSTRACT: In this article we discuss the problem of a reliable determination of parameters of the nuclear mean-field Hamiltonians in view of obtaining high quality comparisons with the experimental single particle spectra: a. In the case of extrapolations to extreme (exotic) isospin nuclei as well as b. In terms of predictions of the energy levels that have not been so far measured also in 'non-exotic' nuclei. We formulate our discussion in terms of the Inverse Problem, a quickly growing sub-field of Applied Mathematics, and introduce a number of mathematical properties which are illustrated in Ref.1 We focus on those mechanisms that may significantly limit the predictive power of the resulting Hamiltonians.
    International Journal of Modern Physics E 01/2012; 19(04). · 0.63 Impact Factor
  • M.-g.porquet
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    ABSTRACT: Using the Euroball array, we have recently performed several experiments devoted to the study of high-spin states of nuclei with A~80–130, produced from fission following various fusion reactions. High-spin level schemes of many neutron-rich nuclei have been extended or newly established. We present here the new experimental results obtained in some neutron-rich odd-Z nuclei from 43Tc to 49In. All the band-head configurations have been identified from the behaviour of the collective bands built on them. Therefore the single-proton states, located around the Fermi levels for Z=43 to 49, can be discussed as a function of the neutron number (and the deformation). In all these isotopic series, three-quasiparticle states have been measured above 2 MeV excitation energy. The case of 49In nuclei is discussed in the framework of shell-model calculations. Futhermore the individual identification of each fragment by means of its emitted γ transitions allows us to have a new insight into the mechanism of fission induced by heavy ions. Preliminary results of the total number of emitted neutrons are discussed as a function of the N/Z ratios of the fragments.
    International Journal of Modern Physics E 01/2012; 13(01). · 0.63 Impact Factor
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    ABSTRACT: The structure of the weakly bound 926F17 odd-odd nucleus, produced from 27,28Na nuclei, has been investigated at GANIL by means of the in-beam γ-ray spectroscopy technique. A single γ-line is observed at 657(7) keV in 926F which has been ascribed to the decay of the excited J=2+ state to the J=1+ ground state. The possible presence of intruder negative parity states in 26F is also discussed.
    Physical Review C 01/2012; 85(1). · 3.72 Impact Factor
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    M.-G. Porquet, O. Sorlin
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    ABSTRACT: The evolution of the N=50 gap is analyzed as a function of the occupation of the proton πf5/2 and πp3/2 orbits. It is based on experimental atomic masses, using three different methods of one- or two-neutron separation energies of ground or isomeric states. We show that the effect of correlations, which is maximized at Z=32 could be misleading with respect to the determination of the size of the shell gap, especially when using the method with two-neutron separation energies. From the methods that are the least perturbed by correlations, we estimate the N=50 spherical shell gap in 2878Ni50. Whether 78Ni would be a rigid spherical or deformed nucleus is discussed in comparison with other nuclei in which similar nucleon-nucleon forces are at play.
    Physical Review C 01/2012; 85(1). · 3.72 Impact Factor
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    ABSTRACT: The 83,81 As nuclei have been produced as fission fragments in the fusion reaction 18O + 208Pb at 85 MeV bombarding energy and studied with the Euroball array. Medium-spin states of 83,81 As have been established up to ∼3.5 MeV excitation energy. From angular correlation analysis, spin values have been assigned to most of the 81 As excited states. The behaviors of the yrast structures identified in this work are discussed in comparison with the general features known in the mass region. Then they are compared to the results of two theoretical approaches: the “rotor + quasiparticle” for 81 As and the shell model using the effective interactions JUN45 for 83,81 As.
    Physical Review C 11/2011; 84(5). · 3.72 Impact Factor
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    ABSTRACT: . Excited states in 212Po have been populated by transfer using the 208Pb(18O,14C) reaction at 85MeV beam energy and studied with the EUROBALL IV multi-detector array. The level scheme has been extended up to ∼ 3.2 MeV excitation energy from the triple- coincidence data. Spin and parity values of most of the observed states have been assigned from the angular distributions and - angular correlations. Several -lines with E γ < 1 MeV have been found to be shifted by the Doppler effect, allowing for the measurements of the associated lifetimes by the DSAM method. The values, found in the range [0.1-0.6]ps, lead to very enhanced E1 transitions. All the emitting states, which have non-natural parity values, are discussed in terms of - 208Pb structure. They are in the same excitation-energy range as the states issued from shell-model configurations.
    European Physical Journal A - EUR PHYS J A. 01/2010; 46(2):165-185.
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    ABSTRACT: Determination of the mean-field Hamiltonian parameters can be seen as gathering information about all the single-particle states out of a very partial information on only a few experimentally known levels. This is exactly what the inverse problem in applied mathematics is about. We illustrate some of the related concepts in view of a preparation of the fully statistically significant parameter adjustment procedures. For this purpose we construct the exactly soluble inverse problems associated with the realistic and phenomenologically powerful nuclear Woods-Saxon Hamiltonian and we analyse a few both physical and mathematical aspects of such procedures. Presented illustrations suggest that to be able to discuss the predictive power of the mean-field Hamiltonians the parameter adjustment procedures must be based on a relatively complex statistical analysis partially addressed in Ref.1
    International Journal of Modern Physics E 01/2010; 19(04):665-671. · 0.63 Impact Factor
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    ABSTRACT: The surrogate reaction method is an indirect way of determining cross sections for nuclear re-actions that proceed through a compound nucleus. This technique enables neutron-induced cross sections to be extracted for nuclear reactions on short-lived unstable nuclei that otherwise can not be measured. This technique has been succesfully applied to determine the neutron-induced fission cross sections of several short-lived nuclei. In this work, we investigate whether this powerful tech-nique can also be used to determine of neutron-induced capture cross sections. For this purpose we use the surrogate reaction 174 Yb(3 He,pγ) 176 Lu to infer the well known 175 Lu(n,γ) cross section and compare the results with the directly measured neutron-induced data. This surrogate experiment has been performed in March 2010. The experimental technique used and the first preliminary results will be presented.
    International Conference on Nuclear Data for Science and Technology 2010, Jeju, Korea; 01/2010

Publication Stats

1k Citations
270.53 Total Impact Points

Institutions

  • 2014
    • Cea Leti
      Grenoble, Rhône-Alpes, France
  • 1999–2013
    • Université Paris-Sud 11
      • • Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse - (CSNSM)
      • • Institut de Physique Nucléaire (IPN)
      Orsay, Île-de-France, France
  • 2012
    • The University of York
      • Department of Physics
      York, ENG, United Kingdom
  • 2007
    • Institute for Nuclear Research and Nuclear Energy
      Ulpia Serdica, Sofia-Capital, Bulgaria
  • 2005
    • University of Birmingham
      • School of Physics and Astronomy
      Birmingham, ENG, United Kingdom
  • 2003
    • Sofia University "St. Kliment Ohridski"
      Ulpia Serdica, Sofia-Capital, Bulgaria
  • 2002–2003
    • Medical University of Sofia
      Ulpia Serdica, Sofia-Capital, Bulgaria
  • 1994–1998
    • French National Centre for Scientific Research
      • Interactions, particles, nucleus, from the laboratory to the cosmos - National Institute of nuclear physic and particles physic (IN2P3)
      Lutetia Parisorum, Île-de-France, France
  • 1995–1997
    • University of Oxford
      • Department of Physics
      Oxford, England, United Kingdom
  • 1996
    • University of Liverpool
      • Department of Physics
      Liverpool, ENG, United Kingdom
  • 1989
    • McGill University
      • Department of Physics
      Montréal, Quebec, Canada
  • 1982–1983
    • Institut de Physique Nucléaire de Lyon
      Lyons, Rhône-Alpes, France