ALPHA-CAPTURE REACTION RATES FOR 22NE(α,N)25MG AND 22NE(α,γ) 26MG REACTIONS VIA SUB-COULOMB ALPHA-TRANSFER AND THEIR EFFECTS ON FINAL ABUNDANCES OF S-PROCESS ISOTOPES

Abstract

The ^22Ne(α,n) reaction is an important neutron source reaction for the slow neutron capture process (s-process) in asymptotic giant branch stars. Direct measurements are extremely difficult to carry out at Gamow energies due to the extremely small reaction cross section. The large uncertainties introduced when extrapolating direct measurements at high energies down to the Gamow energies can be overcome by determining the partial α-width of the relevant states using indirect measurements. This can be done using α-transfer reactions at sub-Coulomb energies to reduce the dependence on optical model parameters. The α-transfer reaction of ^22Ne(^^6Li,d)^26Mg was carried out at the Cyclotron Institute at Texas A&M University to study this reaction. It appears that the partial α widths of the near α-threshold resonances of ^26Mg are different from what was previously assumed. This discrepancy affects the final ^22Ne(α,n) reaction rate and the final abundances of the s-process isotopes.