Identification of analog states in theT=1/2A=27mirror system from low excitation energies to the region of hydrogen burning in the26Alg,m(p,γ)27Si reactions

Abstract

The reactions ${}^{26}$Al${}^{g}$($p$,$\phantom{\rule{0.16em}{0ex}}$$\ensuremath{\gamma}$)${}^{27}$Si and ${}^{26}$Al${}^{m}$($p$,$\phantom{\rule{0.16em}{0ex}}$$\ensuremath{\gamma}$)${}^{27}$Si are important for influencing the galactic abundance of the cosmic $\ensuremath{\gamma}$-ray emitter ${}^{26}$Al${}^{g}$ and for the excess abundance of ${}^{26}$Mg found in presolar grains, respectively. Precise excitation energies and spin assignments of states from the ground state to the region of astrophysical interest in ${}^{27}$Si, including the identification and pairing of key astrophysical resonances with analog states in the mirror nucleus ${}^{27}$Al, are reported using $\ensuremath{\gamma}$ rays observed in the ${}^{12}$C + ${}^{16}$O fusion reaction. The detailed evolution of Coulomb energy differences between the states in ${}^{27}$Si and ${}^{27}$Al is explored, including the region above the astrophysical reaction thresholds.