Structure de noyaux exotiques. Moments nucléaires d'états excités

par Konstantin Stoychev (IJCLab)

mardi 19 sept. 2023, 14:00 → 17:00 Europe/Paris

108/1-XX - Grande Salle 108 (IJCLab)

Title: Structure of exotic nuclei. Nuclear moments of excited states

Abstract:

Magnetic moments of excited nuclear states are a unique probe of nuclear structure. Experimentally obtained values of magnetic moments are useful to constrain theoretical models. Measurements of magnetic moments in exotic nuclei are sensitive to how nuclear structure evolves far from the line of stability. Different experimental techniques have been developed to measure magnetic moments of excited states depending on their mean lifetimes. The Time-Differential Recoil In Vacuum (TDRIV) method is applied on excited states with picosecond lifetimes. For isomeric states with mean lifetimes in the order of hundreds of nanoseconds a suitable method is the Time Dependent Perturbed Angular Distribution (TDPAD) method. The main topic of this thesis relates to the application of these methods to measure magnetic moments of exotic nuclei through the use of radioactive ion beams (RIBs).

The first application of the TDRIV method on a RIB is presented in the first part of the current work. The experiment was performed at the MINIBALL setup of the HIE-ISOLDE facility, CERN. The goal of the experiment was to measure the magnetic moment of the $2_1^{+}$ state in ${}^{28}$Mg. The analysis of the obtained data is presented, alongside that of a calibration TDRIV measurement of the magnetic moment of the $2_1^{+}$ state in ${}^{22}$Ne.

In the next part of the thesis the possibilities to extend the range of applicability of the TDRIV method to higher-$Z$ nuclei is discussed. A charge state measurement of titanium ions was performed at JYFL, Finland, in preparation for a future experiment to determine the magnetic moment of the $2_1^{+}$ state in ${}^{46}$Ti. The analysis of the obtained data and simulations of the planned experiment are discussed.

Finally, the magnetic moments of isomeric states around ${}^{68}$Ni were measured in an experiment at NSCL, MSU, USA, using the TDPAD method. A detailed account of the data analysis is provided and the obtained results are compared with shell-model calculations.

Thesis director: 

Dr. Georgi Georgiev, IJCLab 

Co-director: 

Dr. Johan Ljungvall, IJCLab

Jury:

Dr. Araceli Lopez Martens, IJCLab
Dr. Emmanuel Clement, GANIL
Prof. Theodoros Mertzimekis, University of Athens, Greece
Prof. Giacomo de Angelis, LNL, Legnaro, Italy 
Prof. Luis Mario Fraile, University Complutense, Madrid, Spain