The 13C(α,n)16O reaction is crucial because it is one of the main neutron sources that feed s process for the nucleosynthesis of the elements heavier than iron. The reaction occurs in Asymptotic Giant Branch stars (AGB), which are subject to complex convective motions. Specifically, the reaction takes place in the helium intershell, an environment with temperatures of 108 K. In order to predict the abundances of heavy elements produced in AGB stars it is crucial to know the cross section of the 13C(α,n)16O neutron source in its Gamow Peak, corresponding to Ecm= 140-230 keV.
The LUNA collaboration made a huge effort to measure the cross section in the energy range between 230 and 305 keV, with uncertainties lower than 20%. It's the first time that a direct measurement of this reaction reaches the Gamow Peak window.