Titre de la proposition de thèse ou de stage ou les deux
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Titre de la proposition de thèse ou de stage ou les deux

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Proposition de stage de pré-thèse et thèse 2010-2011 Spécialité : Spécialité NPAC (DEA CPM) Laboratoire : Laboratoire : Institut de Physique Nucléaire d’Orsay Directeur de laboratoire : F. Azaiez Groupe : Structure Nucléaire - NESTER Responsable du stage ou/et de la thèse : • Verney David • Tél. : +33 01 69 15 48 52 • Courriel : verney@ipno.in2p3.fr Titre de la thèse (ou du stage) : 78Contribution à l’étude de la structure de Ni : Etude de la dérive monopolaire des états de particule individuelle neutron dans l’espace de 78valence naturel de Ni. 78Contribution to Ni structure study: Probing the neutron single particle monopole drift in the 78Ni natural valence space Durée du stage : entre 2 et 5 mois environ Ce stage débouche sur une thèse Lieu de travail : Orsay Déplacements éventuels : Legnaro. Collaborations : IPHC (Strasbourg), Legnaro National Laboratory (INFN-Italy), Cologne (Allemagne) Sujet et nature du travail proposé : 78Context: Evolution of Magic Numbers in exotic nuclei, the Ni case. The modification of shell gaps far from stability raises doubts about one of the firmest paradigms of nuclear structure: the universality of magic numbers throughout the nuclear chart. Nuclei are more satble and difficult to excite at particular neutron or proton numbers 8, 20, 28, 50 …, the so-called magic numbers. In recent years, evidence has surfaced pointing to changing shell structure with a varying number of ...

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Proposition de stage de pré-thèse
et thèse 2010-2011
Spécialité :
Spécialité NPAC (DEA CPM)
Laboratoire :
Laboratoire : Institut de Physique Nucléaire d’Orsay
Directeur de laboratoire : F. Azaiez
Groupe : Structure Nucléaire - NESTER
Responsable du stage ou/et de la thèse :
Verney David
Tél. : +33 01 69 15 48 52
Courriel : verney@ipno.in2p3.fr
Titre de la thèse (ou du stage) :
Contribution à l’étude de la structure de
78
Ni :
Etude de la dérive monopolaire des états de particule individuelle neutron dans l’espace de
valence naturel de
78
Ni.
Contribution to
78
Ni structure study:
Probing the neutron single particle monopole drift in the 78Ni natural valence space
Durée du stage :
entre 2 et 5 mois environ
Ce stage débouche sur une thèse
Lieu de travail :
Orsay
Déplacements éventuels :
Legnaro.
Collaborations :
IPHC (Strasbourg), Legnaro National Laboratory (INFN-Italy), Cologne
(Allemagne)
Sujet et nature du travail proposé :
Context
:
Evolution of Magic Numbers in exotic nuclei, the
78
Ni case
.
The modification of shell gaps far from stability raises doubts about one of the firmest
paradigms of nuclear structure: the universality of magic numbers throughout the nuclear
chart. Nuclei are more satble and difficult to excite at particular neutron or proton numbers 8,
20, 28, 50 …, the so-called magic numbers. In recent years, evidence has surfaced pointing to
changing shell structure with a varying number of protons and/or neutrons. These findings
furnish a stringent test for modern nuclear structure models and have important astrophysical
implications. From a theoretical point of view, the reasons for this shell evolution are not well
established and different scenarios are under consideration: variation in the mean field when
approaching the neutron drip-lines as well as specific components (pairing, tensor
interaction…) in the residual interaction, to name a few.
A unique opportunity to study these shell effects is offered by the region of
78
Ni nucleus,
which has 28 protons and 50 neutrons—both magic numbers in stable nuclei.
78
Ni has a
14-neutron excess over the heaviest stable nickel nuclide, and would be—provided 28 and 50
retain their ‘magic’ character—the most neutron rich example of doubly magic nucleus in the
whole nuclide chart with an extreme N/Z ratio of 1.79 (to be compared to N/Z=1.54 for
208
Pb
or 1.64 for
132
Sn). So far, only a dozen of
78
Ni could be successfully synthesized and
identified with most advanced techniques of production of rare isotopes, using high energy
beam fragmentation. The production and observation of
78
Ni was reported only twice in the
history of nuclear physics and this region of the nuclide chart remains extremely hard to reach
experimentally. The only way presently available to study the doubly magic nature of the
78Ni region is to study some relevant cases as close as possible to it.
PhD research program
The light odd-neutron N=51 nuclei
constitute the most interesting cases
to study the neutron single particle
evolution towards
78
Ni. Low-lying
states in N=51 isotones may naturally
be understood in terms of single-
particle
configurations
and
core-
particle coupled states. Our group will
perform in year 2011 an experiment at
Legnaro National Laboratory (Italy)
to determine the nature of the low-
lying yrast or quasi yrast 7/2
+
states in
32 < Z < 40, odd-neutron N=51 nuclei
in order to assess their collective or
ν
1g
7/2
single-particle origin and better constrain the
relative position of the latter with respect to other neutron single particle states above a
78
Ni
core. The structure of the low lying states in odd N=51 isotones will be investigated using the
Recoil distance Doppler-shift (RDDS) method by use of a (so-called)
plunger
device. The
neutron-rich nuclei will be produced in deep-inelastic, multi-nucleon transfer and induced
fission reactions with the
82
Se+
238
U system with an incident
82
Se beam energy of 570 MeV
delivered by the Legnaro Tandem+ALPI accelerator. The plunger will be combined with the
AGATA
gamma-ray spectrometer and the
PRISMA
fragment spectrometer. If the Legnaro
2011 experiment schedule is compatible, then the student will participate in the plunger-
AGATA experiment at Legnaro during his/her “pre-thèse” training program. He/she will take
in charge during his/her PhD all the data analysis of the experiment. In addition, he PhD
student will be in charge of the interpretation of the data in the framework of the nuclear shell
model and core-particle coupling model in close collaboration with the theoretical groups
involved in the field. Last, the PhD student will participate in complementary beta-decay
experiments at
ALTO
which will be scheduled within the next three years.
Figure 1 AGATA demonstrator at Legnaro National Lab (Italy)