Neutron spectroscopy of ²⁶Mg states: Constraining the stellar neutron source ²²Ne(α, n)²⁵Mg

This work reports on accurate, high-resolution measurements of the ²⁵Mg(n, γ)²⁶Mg and ²⁵Mg(n, tot) cross sections in the neutron energy range from thermal to about 300 keV, leading to a significantly improved ²⁵Mg(n, γ)²⁶Mg parametrization. The relevant resonances for n+²⁵Mg were characterized from a combined R-matrix analysis of the experimental data. This resulted in an unambiguous spin/parity assignment of the corresponding excited states in Mg-26. With this information experimental upper limits of the reaction rates for ²²Ne(α, n)²⁵Mg and ²²Ne(α, γ)²⁶Mg were established, potentially leading to a significantly higher (α, n)/(α, γ) ratio than previously evaluated. The impact of these results has been studied for stellar models in the mass range 2 to 25 solar mass. (authors)