25.4.2023 Beta decay of neutron-rich nuclei provides a way to study nuclear structure and the production of heavy elements in neutron star collisions (Al Ayoubi)
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.
Lama Al Ayoubi did her MSc thesis project at GANIL, Caen, and got her MSc degree from the Lebanese University in 2018. Since 2019, she has been pursuing her Ph.D. through a joint "cotutelle" PhD program between the University of Jyvaskyla and the University of Paris-Saclay. "I am fortunate to have had the opportunity to do my Ph.D. in a cotutelle program, which allowed me to work with experts from two different universities and cultures, expanding my knowledge and providing me with a broader perspective. While the experience was challenging, such as balancing the demands of two universities and managing the logistics of living in two different countries, the cotutelle program helped me grow professionally and personally," says Al Ayoubi.
M.Sc. Lama Al Ayoubi defends her doctoral dissertation ”Nuclear structure at the neutron emission threshold and below explored via beta-decays of 82,83Ga and 86As” on 25 April 2023 at 12 noon. Opponent is Professor Maria Jose Garcia Borge (CSIC Madrid, Spain) and custos is Professor Anu Kankainen (Ģֱ). The language of the dissertation is English.
Audience can follow the dissertation in the lecture hall FYS1, or online.
Link to the Zoom Webinar event (Zoom application or Google Chrome web browser recommended):
