G. IMBRIANI

We report on measurements of resonance strengths and energies for the Ep = 151 and 193 keV resonances in the 18O(p,gamma)15N and 17O(p,gamma)14N reactions, respectively, obtained during commissioning of a new setup for alpha-particle detection studies at the LUNA underground laboratory. Our values, omegagamma(151) = 164.2 ± 0.9 stat+12.1−11.7...

In stars with temperatures above 20 × 106 K, hydrogen burning is dominated by the CNO cycle. Its rate is determined by the slowest process, the 14N(p, γ )15O reaction. Deep underground in Italy's Gran Sasso laboratory, at the LUNA 400 kV accelerator, the cross section of this reaction has been measured at energies much lower than ever achieved...

Classical novae are important contributors to the abundances of key isotopes, such as the radioactive 18F, whose observation by satellite missions could provide constraints on nucleosynthesis models in novae. The 17O(p,gamma)18F reaction plays a critical role in the synthesis of both oxygen and fluorine isotopes but its reaction rate is not...

The 22Ne(p,gamma)23Na reaction takes part in the neon-sodium cycle of hydrogen burning. This cycle is active in asymptotic giant branch stars as well as in novae and contributes to the nucleosythesis of neon and sodium isotopes. In order to reduce the uncertainties in the predicted nucleosynthesis yields, new experimental efforts to measure the...

Classical novae are important contributors to the abundances of key isotopes, such as the radioactive 18F, whose observation by satellite missions could provide constraints on nucleosynthesis models in novae. The 17Oðp; Þ18F reaction plays a critical role in the synthesis of both oxygen and fluorine isotopes, but its reaction rate is not well...

The 18O(p,α)15N reaction affects the synthesis of 15N, 18O and 19F isotopes, whose abundances can be used to probe the nucleosynthesis and mixing processes occurring deep inside asymptotic giant branch (AGB) stars. We performed a low-background direct measurement of the 18O(p,α)15N reaction cross-section at the Laboratory for Underground...

The 22Ne(p,γ)23Na reaction, part of the neon-sodium cycle of hydrogen burning, may explain the observed anticorrelation between sodium and oxygen abundances in globular cluster stars. Its rate is controlled by a number of low-energy resonances and a slowly varying nonresonant component. Three new resonances at Ep = 156.2, 189.5, and 259.7 keV...

The direct measurement of reaction cross sections at astrophysical energies often requires the use of solid targets of known thickness, isotopic composition, and stoichiometry that are able to withstand high beam currents for extended periods of time. Here, we report on the production and characterisation of isotopically enriched Ta2O5 targets...

The experimental study of nuclear reactions of astrophysical interest is greatly facilitated by a low-background, high-luminosity setup. The Laboratory for Underground Nuclear Astrophysics (LUNA) 400 kV accelerator offers ultra-low cosmic-ray induced background due to its location deep underground in the Gran Sasso National Laboratory...

Among the reactions involved in the production and destruction of deuterium duringBig Bang Nucleosynthesis, the deuterium-burningD(p,γ)3He reaction has the largest uncertainty and limits the precision of theoretical estimates of primordial deuterium abundance. Here we report the results of a careful commissioning of the experimental setup...

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...