Exploiting Isospin Symmetry To Study The Role Of Isomers In Stellar Environments

Proton capture on the excited isomeric state of Al-26 strongly influences the abundance of Mg-26 ejected in explosive astronomical events and, as such, plays a critical role in determining the initial content of radiogenic Al-26 in presolar grains. This reaction also affects the temperature range for thermal equilibrium between the ground and isomeric levels. We present a novel technique, which exploits the isospin symmetry of the nuclear force, to address the long-standing challenge of determining proton-capture rates on excited nuclear levels. Such a technique has in-built tests that strongly support its veracity and, for the first time, we have experimentally constrained the strengths of resonances that dominate the astrophysical Al-26(m)(p, gamma)Si-27 reaction. These constraints demonstrate that the rate is at least a factor similar to 8 lower than previously expected, indicating an increase in the stellar production of Mg-26 and a possible need to reinvestigate sensitivity studies involving the thermal equilibration of Al-26.