A. COMPAGNUCCI

nstars,the fusion of 22Ne and4Hemayproduce either 25Mg, with the emission of a neutron, or 26Mg and a γ ray. At hightemperature, the (α,n)channeldominates,while at low temperature, it is energetically hampered. The rate of its competitor, the 22Ne(α,γ)26Mg reaction, and, hence, the minimum temperature for the (α,n) dominance, are controlled by...

The 12C/13C ratio is a significant indicator of nucleosynthesis and mixing processes during hydrogen burning in stars. Its value mainly depends on the relative rates of the 12Cðp; γÞ13N and 13Cðp; γÞ14N reactions. Both reactions have been studied at the Laboratory for Underground Nuclear Astrophysics (LUNA) in Italy down to the lowest energies...

The 20Ne(p, γ ) 21Na reaction is the slowest in the NeNa cycle and directly affects the abundances of the Ne and Na isotopes in a variety of astrophysical sites. Here we report the measurement of its direct capture contribution, for the first time below Ec.m. = 352 keV, and of the contribution from the Ec.m. = 368 keV resonance, which dominates...

Background: Among the several inhomogeneities in the composition of globular cluster stars, an overabundance of 23Na is interpreted as the signature of the operation of the neon-sodium (NeNa) cycle. One of the hypothesis to explain the observed O-Na anticorrelation invokes massive asymptotic giant branch stars as the main agents. At...

The D(p, γ ) 3He reaction, where 'D' denotes '2H', is of primary importance in cosmology and nuclear physics since it offers a unique opportunity to test predictions based on the description of nuclear interactions. We present a novel approach to extract the angular distribution of the photons emitted by the D(p, γ ) 3 He reaction inferred from...

The CNO cycle is one of the most important nuclear energy sources in stars. At temperatures of hydrostatic H-burning (20 MK < T < 80 MK) the 17O(p; γ)18F reaction rate is dominated by the poorly constrained 64.5 keV resonance. Here, we report on the first direct measurements of its resonance strength and of the direct capture contribution at...