Lien de connexion / Link :
https://r.jyu.fi/dissertation-al-ayoubi-250423
Merci de laisser fermés camera et micro de votre ordinateur pendant la soutenance.
Please keep your camera and microphone switched off throughout the defense.
Lien de l'annonce :
Abstract :
β--decay is a type of radioactive decay that occurs when a neutron in the nucleus decays into a proton, an electron, and an antineutrino to become more stable. The newly formed "daughter" nucleus can be populated in its ground state or higher energy excited states. Excited states are typically unstable and tend to decay back to their ground state by emitting energy in the form of gamma rays or particles.
The thesis of MSc Lama Al Ayoubi focused on the population of high-energy states around the neutron separation energy, which is the energy required for a neutron to be removed from the nucleus. These high-energy states in atomic nuclei are of particular interest because their structure can provide important insights into complex nuclear physics questions. One such question relates to the Pygmy Dipole Resonance, a type of oscillation that occurs in neutron-rich nuclei. In addition, the studied neutron-rich nuclei play a role in elemental nucleosynthesis taking place in neutron-star mergers.
The research involved two experiments. The first experiment studied the beta decay of 82,83Ga at the ALTO facility, in Orsay, France. The second experiment focused on the beta decay of 86As at the IGISOL facility of the JYFL Accelerator Laboratory at the University of Jyvaskyla. Through these experiments, MSc Lama Al Ayoubi updated the level schemes of the β-decay daughters and observed more than 80 new γ-ray transitions. In addition, γ-ray transitions were detected with energies higher than the neutron separation energy for the first time in 82Ge and new γ-ray transitions following the beta-delayed neutron emission in both 81Ge and 85Se were observed. The research also involved measuring the half-lives of 82,83Ga and 86As and the neutron emission probabilities of 83Ga and 86As. As a result, the measurements showed that the β-decay of 82Ga populates states with 1- spin-parity between 6 and 8 MeV in 82Ge, but it is unclear if they have PDR characteristics. Additionally, shell-model calculations were performed . The calculated spectrum for 86Se shows agreement with the newly assigned spin and parities.
