Complete Study of Proton Capture on Carbon Isotopes at Astrophysical Energies

This thesis presents a comprehensive investigation of the 12C(p,g)13N and the 13C(p,g)14N reactions, crucial elements that help in understanding different stages of stellar evolution. In particular, the ratio of carbon isotopes, 12C/13C, directly observable in the stellar atmospheres, is profoundly impacted by the dynamics of stars. Thus, it is a useful observable that can be tested against the stellar models to better constrain the mixing phenomena within Red Giant Branch (RGB) and Asymptotic Giant Branch (AGB) stars, offering valuable insights into their evolution. Additionally, the carbon isotopic ratio serves as a potent tool to study the chemical evolution of galaxies. The primary focus of this study was the determination of precise cross section data for these reactions, achieved through experiments conducted at LUNA, located in the Laboratori Nazionali del Gran Sasso (LNGS), both the 12C(p,g)13N and the 13C(p,g)14N, and at Felsenkeller laboratories, only the 12C(p,g)13N. The energy range covered in the former is Ep = 70 - 400 keV, the latter instead is Ep = 320 - 620 keV. By employing multiple experimental techniques and performing rigorous cross checks, the highly precise cross section data were obtained for the 12C(p,g)13N and 13C(p,g)14N reactions. Additionally, an in depth characterization of systematic uncertainties were performed with several supplementary measurements to enhance the reliability of the results. The results show cross section approximately 30% lower for both the reactions with respect to the literature values. The novel 12C/13C ratio derived from this study, in combination with the obtained reaction rates, can significantly advance our ability to model and understand the mixing phenomena occurring in stars. The improved precision facilitates the constraining of theoretical stellar models against the observations, leading to more accurate predictions of stellar evolution and nucleosynthesis processes.