>Magister Scientiae - MSc / The high-spin states of the nucleus 152Gd have been populated via the 152Sm (α, 4n) 152Gd fusion-evaporation reaction at a beam energy of 45MeV. The emitted γ rays were observed with the AFRODITE spectrometer array. The previously known decay scheme of 152Gd was extended. Directional Correlation from Oriented states of nuclei (DCO) and linear polarization measurements were performed in order to assign spins and parities in the 152Gd decay scheme. An alternative interpretation of the first excited Kπ = 0+ band, previously considered to be a β-vibration is discussed.

La première partie se concentre sur les aspects expérimentaux et nous a permis, dans un premier temps, d'introduire les trois dispositifs de détection ? d'intérêt pour ma thèse. Dans un second temps, plutôt que détailler les procédures traditionnelles d'analyse de données, nous avons choisit d'introduire un nouveau formalisme pour le calcul des intensités relatives dans un spectre. Ce formalisme remet en question la méthode traditionnellement utilisée. Dans l'optique de toujours gagner du temps, et afin d'aller plus loin dans les méthodes d'analyse, un travail collaboratif a été mis en place pour développer le logiciel Cubix. Ce travail collaboratif qui a été mené sur ce logiciel à permis d'aboutir à une version ergonomique, complète et incluant des fonctionnalités inédites. Une des perspectives de ce travailserait d'implémenter le formalisme sur les intensités dans Cubix.La seconde partie, quant à elle, se concentre sur l'interprétation des données obtenues à partir des expérience JUROGAM II et EUROBALL IV. L'analyse simultanée de ces deux expériences a permis d'obtenir des résultats expérimentaux solides et convaincants. L'analyse des états de haut spin dans le noyau de 223 T h ont dévoilé, pour la première fois dans les isotopes de Thorium,une brusque augmentation de son moment d'inertie. Ce phénomène a été interprété comme les premières indications d'un changement de forme de type quadripolaire-octupolaire (ballon de rugby-poire), à haut spin. Sur cette même thématique, certaines perspectives ont été évoquées :(i) Collaboration avec le groupe théorie de l'IPNL pour effectuer une interprétation plus précise du phénomène observé ;(ii) Proposition d'expérience visant à déterminer les premiers indices de déformation octupolaire dans les isotopes de Thorium pauvres en neutrons ;(iii) Caractérisation de la bande quadrupoalaire à quatre quasi-particules alignées dans les isotopes de 222,223,224 Th. Cela représente un challenge expérimental énorme, demandant l'utilisation de détecteurs à très haute efficacité.Enfin, la dernière partie aborde les résultats issus de l'expérience AGATA+VAMOS au GANIL. Un nouveau schéma de niveaux pour le noyau exotique 81Ga a été proposé. Le dernier état d'excitation observé à 2759keV (spin I = 13/2 - ) a été discuté comme étant un indice d'une fermeture de couche N = 50 importante. Des extrapolations concernant le caractère doublement magique du noyau 78Ni peuvent être envisagées en tant que perspectives de ce travail / The first part focuses on the experimental aspects and allowed us, initially, to introduce the three ? detectors of interest for my thesis. In a second step, rather than detailing traditional data analysis procedures, we have chosen to introduce a new formalism for the calculation of relative intensities in a spectrum. This formalism calls into question the method traditionally used. In order to always save time, and in order to go further in the analysis methods, a collaborative work was put in place to develop the Cubix software. This collaborative work on this software has resulted in an ergonomic version, complete and including new features. One of the perspectives of this work would be to implement the formalism on the intensities in Cubix.The second part focuses on the interpretation of the data obtained from the JUROGAM II and EUROBALL IV experiments. The simultaneous analysis of these two experiments yielded solid and convincing experimental results. The analysis of theHigh spin in the nucleus of 223Th has shown for the first time in the isotopes of Thorium, a sudden increase in its moment of inertia. This phenomenon has been interpreted as the first indications of a quadrupole to octupole-quadrupole (rugby ball-pear), high-spin type change. On the same theme, some perspectives were raised:(I) Collaboration with the IPNL theory group to perform a more accurate interpretation of the observed phenomenon;(Ii) Experimental proposal to determine the onset of octupole deformation in Neutron-poor Thorium isotopes;(Iii) Characterization of the quadrupole band with four quasiparticles aligned in the isotopes of 222,223,224Th. This represents a huge experimental challenge, requiring the use of very high-efficiency detectors.Finally, the last part deals with the results of the AGATA + VAMOS experiment at GANIL. A new level scheme for the exotic nucleus 81Ga has been proposed. The last excitation state observed at 2759 keV (spin I = 13/2 -) was discussed as an indication of a large N = 50 shell closure. Extrapolations concerning the doubly magic character of the 78Ni nucleus can be considered as perspectives of this work

This PhD thesis is concerned with developing a methodology for early diagnosis of cancer by comparing the resonant frequencies in the amplitude spectra obtained during a vibration test using the AFM or, by comparing the stiffness properties of single cancerous and normal cells obtained using a resonant technique. As there is no reliable data in the literature to prove the existence of resonant frequencies of single cells, this work pioneers the search for resonant frequencies of related microspherical soft bodies using the AFM. Experiments to investigate the resonant behaviour of single cells depends on various parameters which are difficult to control; for example, the cell type, deciding at what stage the cell should be tested during the culturing process, determining the nucleus size, determining the cytoskeleton integrity and designing an appropriate vibration test setup among others. For this reason, agarose microspheres were selected to carry out preliminary work as these samples have similar properties to human cells and their resonances are affected by fewer variables. Although these micrometric spheres were tested under different conditions, no clear resonant behaviour was found at frequencies below 20 kHz and, only wide curves (interpreted as highly damped peaks of resonance) in the interval ranging from 20 kHz to 100 kHz were observed. By considering those curves as the quadrupole (Qp) vibration mode, approximate stiffness values for the agarose microspheres were found to be in between 37 kPa and 72 kPa. These values are similar to those obtained during an indentation test performed on the same samples whic¬¬h gave Young’s modulus values ranging from 10 kPa to 200 kPa. In order to gain a greater insight into the vibration test performed on microscopic samples, the research was extended to include agarose spheres of millimetric size. The characterization of these samples was carried out using an innovative purpose-built experimental setup. For the vibration test, a PZT based excitation device and a vibro-acoustic sensor were designed and constructed. The amplitude spectra of the vibration tests performed on millimetric samples consistently showed at least three peaks of resonance from which after the numerical simulation of the vibration test were interpreted as the quadrupole (Qp) and octupole (Op) vibration modes. Using this information, stiffness values for the samples ranging from 100 kPa to 700 kPa were calculated. In order to obtain the stiffness of the millimetric samples using a different technique, an experimental setup was constructed to perform a compression test. However, due to high viscoleasticity of the samples, it was not possible to obtain a standard compression curve necessary for their mechanical characterization. The results obtained from the tests on millimetric agarose samples demonstrate that spheres made of this material are able to provide measurable vibrational characteristics. Consequently, this methodology can be further implemented on micrometric samples and possibly on human cells to detect their resonant frequencies and equivalent stiffness values which can be used as a cancer marker. From the vibrational experiments on millimetric samples, it was noticed that the excitation mechanism plays an important role and for this reason future work is proposed to continue in this direction.

The existence of highest proton numbers at which the nuclear landscape cease to ex- ist, the end of the periodic table of elements and the limits of the existence of the nu- clei are some of the difficult questions to answer. To explore those questions, we in- vestigated hyperheavy nuclei (Z ≥ 126) using covariant density functional theory. We demonstrate the existence of three regions of spherical hyperheavy nuclei centered around (Z ∼ 138, N ∼ 230), (Z ∼ 156, N ∼ 310) and (Z ∼ 174, N ∼ 410). Also, we explored other properties of hyperheavy nuclei such as octupole deformation, alpha decay half lives, chemical potential, etc.

Covariant density functional theory (CDFT) is a modern theoretical tool for the description of nuclear structure phenomena. Different physical observables of the ground and excited states in even-even nuclei have been studied within the CDFT framework employing three major classes of the state-of-the-art covariant energy density functionals. The global assessment of the accuracy of the description of the ground state properties and systematic theoretical uncertainties of atomic nuclei have been investigated. Large-scale axial relativistic Hartree-Bogoliubov (RHB) calculations are performed for all Z < 106 even-even nuclei between the two-proton and two-neutron drip lines. The sources of theoretical uncertainties in the prediction of the two-neutron drip line are analyzed in the framework of CDFT. We concentrate on single-particle and pairing properties as potential sources of these uncertainties. The major source of these uncertainties can be traced back to the differences in the underlying single-particle structure of the various CEDFs. A systematic search for axial octupole deformation in the actinides and superheavy nuclei with proton numbers Z = 88 - 126 and neutron numbers from two-proton drip line up to N = 210 has been performed in CDFT. The nuclei in the Z ~ 96, N ~ 196 region of octupole deformation have been investigated in detail and their systematic uncertainties have been quantified. The structure of superheavy nuclei has been reanalyzed with inclusion of quadrupole deformation. Theoretical uncertainties in the predictions of inner fission barrier heights in superheavy elements have been investigated in a systematic way. The correlations between global description of the ground state properties and nuclear matter properties have been studied. It was concluded that the strict enforcement of the constraints on the nuclear matter properties (NMP) defined in Ref. [1] will not necessary lead to the functionals with good description of ground state properties. The different aspects of the existence and stability of hyperheavy nuclei have been investigated. For the first time, we demonstrate the existence of three regions of spherical hyperheavy nuclei centered around (Z ~ 138, N ~ 230), (Z ~ 156, N ~ 310) and (Z ~ 174, N ~ 410) which are expected to be reasonably stable against spontaneous fission.

Cette thèse a été effectuée dans le cadre d'un projet qui vise à explorer les facteurs limitants des performances d'une horloge à ions dans le domaine des fréquences micro-onde. Ce travail repose sur l'observation et la manipulation d'un grand nuage d'ions dans des potentiels de géométries différentes. Le but est l'analyse et le transport d'un grand nuage pouvant dépasser 10^6 ions dans un piège radio-fréquence linéaire à plusieurs zones. Notre groupe à construit un piège à trois zones destiné au piégeage d'ions calcium: deux parties quadrupolaires et une partie octupolaire montées en ligne. Les ions sont créés dans la première partie quadrupolaire et refroidis par laser le long de l'axe du piège. Nous avons d'abord étudié la création d'un grand nuage. La limite actuelle des paramètres du système permet de confiner et détecter des nuages de taille maximale 1,2.10^5 ions. Ensuite, grâce à un protocole de transport rapide et optimisé, ces ions sont transportés dans le deuxième et troisième piège avec une efficacité pouvant atteindre 100%. Les résultats en fonction de la durée de transport montrent une asymétrie entre les deux sens de transport que nous exploitons pour ajouter des ions dans le deuxième piège sans perte du nuage initialement présent. Cette technique d'accumulation a permis de piégér 2,5.10^5 ions dans le deuxième et troisième piège. Ce nombre semble limité par les refroidissement. Enfin, dans l'octupole, les observations montrent que, contrairement aux structures creuses attendues par les modèles, les ions froids s'organisent dans trois minima locaux de potentiels. La cause de cette différence est un petit défaut dans la symétrie octupolaire des barreaux. / This thesis is part of a project aiming to explore the performance limiting factors of a microwave ion clock. This work is based on the observation and manipulation of a large ion cloud in potentials with different geometries. The purpose is to analyze and transport a large cloud of more than 10^6 ions in a linear radio-frequency trap with several zones. Our group has build a three-zone trap for calcium ion trapping: two quadrupole parts and an octupole part mounted inline. Ions are created in the first quadrupole part and cooled by lasers along the trap symmetry axis. We study the creation of a large ion cloud. The current trapping and cooling parameters limit the maximum size of the cloud to 1,2.10^5 ions. with a rapid and optimized transport protocol, these ions are transfered in the second part of the trap and then in the octupole trap with an efficiency of up to 100%. The result as function of the transport duration shows an asymmetry between the two transport directions. We exploit this feature to add ions in the second or third trap without loss of the already trapped ions. This accumulation technique has allowed to trap 2,5.10^5 ions in the second and third trap. The cooling laser power seems to be the major limiting factor of this number. Finally the observation of the ions in the octupole shows that the cold ions are localised in three different potential wells. This is in contradiction with the hollow structure predicted by the analytical fluid model and molecular dynamics simulations. The cause of this difference is a tiny defect in the octupole symmetry of the RF-electrodes which leads to local minima in the multipole potential.

Nous nous sommes intéressés à la restauration de la symétrie de réflexion droite-gauche brisée dans certains calculs effectués en utilisant l'approche HTDA (Higher Tamm-Dancoff Approximation). Cette approche a été proposée par le groupe de Bordeaux pour traiter de façon microscopique les corrélations en conservant explicitement les nombres de nucléons. La projection sur la parité par la méthode PAV (projection après variation) utilisant une généralisation du théorème de Wick de type Löwdin s'est avérée être très bien adaptée dans le cadre d'un modèle simplifié pour ce type de calcul et a permis de tourner certaines difficultés propres aux calculs qui utilisent la théorie de la fonctionnelle de la densité déduite par exemple de l'interaction de Skyrme. Les résultats obtenus pour des noyaux lourds manifestant une déformation octupôlaire ou à tout le moins une grande déformabilité pour ce mode, sont en gros tout à fait cohérents avec les calculs antérieurs effectués dans une approche HFB ou HF+BCS. D'autre part nos résultats montrent qu'on peut abaisser par projection sur la parité positive la hauteur de la seconde barrière de fission par une quantité de l'ordre de 1 MeV. / This thesis has been concerned with the restoration of the left-right symmetry broken in some instances. This has been achieved in the framework of the Higher Tamm-Dancoff Approximation (HTDA) proposed by the Bordeaux group to treat correlations in an explicitly particle-number conserving microscopic approach. The parity-projected calculations performed within a PAV (projection after variation) method using a generalized Wick's theorem due to Löwdin has appeared to be a very well-suited frame. It has been implemented within a simple model approach. This has been proposed to clear out some difficulties appearing when one uses an Energy Density Functional approach with an energy density functional issued from an underlying Skyrme interaction. As a result we obtain a fairly good global agreement of our results with previous ones issuing from an HFB approach or its HF+BCS limit, for some heavy nuclei exhibiting a stable octupole deformation or at least a remarkable smoothness for this collective mode. As another result, we have shown that the projection on a positive parity solution is able to reduce the second fission barrier height by about 1 MeV.