Determination of the resonance strength of the 11.83 MeV state in the 22Ne(α,γ)26Mg reaction

The 22Ne(α, γ)26Mg reaction indirectly influences the s-process in both asymptotic giant branch (AGB) and massive stars by competing with the 22Ne(α, n)25Mg reaction that acts as a neutron source. This reaction becomes astrophysically significant only at temperatures exceeding 1 GK, which are likely found in the carbon-burning shells of massive stars with masses M > 8M⊙. As a result, there is limited literature available on its resonances and resonance strengths especially at the resonance corresponding to the Ex = 11.83 MeV excited state. Using the DRAGON recoil separator at the TRIUMF particle accelerator in Vancouver, BC, we directly measured the 22Ne(α, γ)26Mg reaction. Specifically, the Ecm = 1.213 MeV resonance populating the Ex = 11.83 MeV was investigated. A resonance strength ωγ = 1.5 ± 0.1 meV was determined using singles data. While a resonance strength ωγ = 1.8 ± 0.3 meV, for coincidence data was found to be within agreement, the use of a partial BGO array has resulted in an unreliable BGO efficiency. Thus, the singles result is taken to be the most accurate value. These results are compared with the previously accepted resonance strength of ωγ = 2.5 ± 0.3 meV, as reported by Wolke et al. (1989), suggesting that the true resonance strength may be lower than previously believed. The improvements in experimental setup and methodology over the past 36 years are discussed in the context of these findings. Furthermore, the implications of these results on the sprocess and their influence on stellar reaction rates are explored.