Disputation: Lucia Crespo Campo
Doctoral candidate Lucia Crespo Campo at the Department of Physics, Faculty of Mathematics and Natural Sciences, is defending the thesis
"Investigating the γ decay of Ni isotopes and its applications to nuclear astrophysics"
for the degree of Philosophiae Doctor.
The PhD defence and trial lecture are fully digital and streamed using Zoom. The chair of the defence will moderate the disputation.
Ex auditorio questions: the chair of the defence will invite the audience to ask ex auditorio questions either written or oral. This can be requested by clicking 'Participants' and then choose 'Raise hand'.
Main research findings
One of the greatest - and not yet fully understood - puzzles in the history of physics is how elements heavier than Fe are created in the universe. To model this nucleosynthesis, the probability for a nucleus to absorb a neutron and emit a γ ray, i.e., the (n, γ) cross section, must be known for thousands of reactions. Often, these probabilities cannot be directly measured and must be calculated using other average nuclear properties. Two of these properties are the nuclear level density, or number of energy levels in a nucleus per unit of energy, and the γ-strength function, connected to the probability of the nucleus emitting γ rays of a specific energy.
In this PhD thesis, the γ decay of several Ni isotopes has been measured to obtain these nuclear properties and to study one of the least known features of γ decay: the low-energy enhancement, or increased probability of decay with low energy γ rays (< 3 MeV). This enhancement, which can have a major impact on nucleosynthesis calculations, has been seen in all the studied Ni isotopes and, for the first time, suggested by data from neutron capture reactions. Finally, the results have been used to calculate the (n, γ) cross sections for 63Ni and 69Ni, important to model the nucleosynthesis of heavy elements.
Contact information to Department: Line Trosterud Resvold