The reactions 25Mg(α,n)28Si, 26Mg(α,n)29Si and their possible impact on nucleosynthesis.

At the time neon burning is activated in massive stars, large amounts of ²⁵Mg and ²⁶Mg have been accumulated from the previous evolutionary phases. In particular, at typical temperatures for neon shell burning, the reactions ²⁵Mg(α,n)²⁸Si and ²⁶Mg(α,n)²⁹Si become efficient providing additional neutron fluxes and affecting the nucleosynthesis distribution. Good knowledge of the reaction rates is required to study their effect on nucleosynthesis during neon shell burning conditions (T₉>=1.5, where T₉ is the temperature in gigakelvin). At the Nuclear Science Laboratory, University of Notre Dame, IN, USA we developed a neutron detector to investigate the ²⁵Mg(α,n)²⁸Si and ²⁶Mg(α,n)²⁹Si reactions as possible neutron sources during neon shell burning. In the present paper we briefly describe the experimental procedures developed to measure those reactions. Finally, we discuss the impact of ²⁵Mg(α,n)²⁸Si and ²⁶Mg(α,n)²⁹Si on the s-process nucleosynthesis for the barium isotopes. [ABSTRACT FROM AUTHOR]