Utilisation de détecteurs à semi-conducteurs pour l'étude de la désintégration bêta des isotopes 79Zn et 80Zn.

Nuclear structure research aims to understand the properties of atomic nuclei, such as their shape, size, stability, and the interactions between their particles. Scientists develop theoretical models and experimental techniques to describe and predict the behavior of these nuclei, with a focus on exotic nuclei rich in neutrons that exhibit unusual structures. This thesis focuses on studying the $\beta$ decay of nuclei $^{79}$Zn and $^{80}$Zn, produced at the ISOLDE facility at CERN. These relatively simple nuclear systems, with a few protons and neutron holes outside the doubly magic nucleus$^{78}$Ni, can be treated within the framework of the shell model. The main objective is to improve existing level schemes and extract the lifetimes of excited states of these nuclei using the fast timing electronic synchronization technique. We have examined the nuclear structure of $^{80}$Ge nucleus ($N$=48, $Z$=32) produced by the $\beta$ decay of the 3- state of $^{80}$Ga. Previous studies suggested the presence of a deformed 0$_{2}^{+}$ state at 639(1) keV in $^{80}$Ge. We used $\gamma$$\gamma$ coincidence measurements within $\gamma$ spectroscopy and shell model calculations to study the position of this state. Although some gamma transitions were observed in coincidence with known levels, no connecting transition with the proposed state was established. Shell model calculations could not satisfactorily reproduce this low-energy state. We analyzed the energy level structure of $^{80}$As nucleus, formed by the beta decay of $^{80}$Ge. A low-energy excited state (46 keV) and a new transition at 672 keV were observed. In the nucleus 79Ga, several new transitions and levels were identified. A half-life measurement was performed, revealing a long-lived excited state at 2561 keV attributed to a 9/2+ spin. In nucleus $^{79}$Ge, precise half-life measurements of low-energy states were conducted, confirming previously established upper limits for the level at 465 keV, where a half-life of 60(10) ps was measured. Additionally, a long half-life of 240(20) ps was measured for the energy level at 607 keV, suggesting a reduction in collectivity for this state due to the low reduced transition probability B(E2) compared to neighboring nuclei. In nucleus $^{79}$As, new transitions and levels were observed, but some spin and parity assignments remain uncertain. Half-life measurements were made for the levels at 100, 110, and 231 keV. A half-life of 680(30) ps was determined for the level at 100 keV, confirming its special status at low energy. This transition is of M1 type, and the spin assignment for this state is 1/2-. Experimental measurements revealed half-lives of 145(15) ps and 210(24) ps for the energy levels at 110 and 231 keV, respectively. Reduced transition probabilities suggest that these transitions are delayed M1 type, which is in accordance with shell model predictions and with the observed systematics for neighboring isotopes.