Direct Measurements of the 23Na(α,p)26Mg reaction cross section at energies relevant for the production of galactic 26Al

In the convective C/Ne burning shell of massive pre-supernova stars, the ²³Na(α,p)²⁶Mg reaction is one of the main sources of protons for the ²⁵Mg(p, γ)²⁶Al reaction, which is the primary direct process for ²⁶Al production in this environment. A recent study found that a factor of 10 increase in the ²³Na(α,p)²⁶Mg reaction rate corresponds to a factor of 3 change in the final abundance of ²⁶Al for this particular scenario. No reliable experimental information exists at appropriate astrophysical energies. The recommended rate is based on a statistical model. We have performed a direct measurement of the ²³Na(α,p)²⁶Mg reaction cross section using inverse kinematics with a ²³Na beam from ATLAS, a cryogenic ⁴He gas target, and an array of Double Sided Silicon Detectors. Integrated cross sections for the reactions ²³Na(α,p₀)²⁶Mg and ²³Na(α,p₁)²⁶Mg^* have been extracted for the first time at astrophysically relevant energies (Ec_m = 1.84 MeV to 2.63 MeV). The corresponding stellar reaction rate has been recalculated and compared with the statistical model recommended rate.

This work is supported by the U.S. DOE Office of Nuclear Physics DE-AC02-06CH11357.