Improved resonance strengths in the 21Ne(p,gamma) reaction at astrophysical energies

The 21Ne(p,gamma)22Na reaction is part of the NeNa cycle, which is one of the possible sets of thermonuclear reactions through which massive stars burn hydrogen into helium. The astrophysical impact of the 21Ne(p,gamma)22Na reaction is the production of the unstable nucleus of 22Na, which is a stellar gamma ray signature, in classical novae and supernovae. To predict the amount of 22Na produced in these environments it is necessary a detailed knowledge of the 21Ne(p,gamma)22Na reaction rate. At low energy, the reaction rate is dominated by several resonances, and the resonance strengths are known with high uncertainty from previous experiments. To the purpose of reducing the uncertainties, the low energy resonances of the 21Ne(p,gamma)22Na reaction are being remeasured in an ongoing experiment at the Laboratory for Underground Nuclear Astrophysics (LUNA) in the Gran Sasso National Laboratory. The exceptionally low background of the underground facility is particularly suited to measure the signal produced by reactions with extremely small cross section, such as charged particle induced reactions at low energy. This thesis is focused on the study of the two resonances at Ep=271 keV and Ep=272 keV, measured at LUNA in Autumn 2022. The experimental setup comprised a windowless gas target, on which the proton beam provided by the LUNA 400 kV accelerator impinged. The gas target was filled with natural neon gas and two high purity germanium detectors were used to detect the prompt gamma rays produced by the reaction. Four new primary transitions are identified for the de-excitation of the 22Na excited level populated by the Ep=272 keV resonance, and the branching ratios have been calculated. In comparison to the literature values, the Ep=271 keV resonance and the Ep=272 keV one are higher by 0.9 keV and 0.8 keV, respectively. The resonance strengths have been measured with higher precision compared to previous experiments, and the resonance energy obtained for the Ep=272 keV resonance is higher by 40 meV than the literature value.