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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. : [phone] • Courriel : [e-mail] 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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• Publié par: Seam
• Nombre de lectures: 22
• Langue: English

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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. : [phone]

•

Courriel : [e-mail]

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)