Observation of strong isospin mixing in proton emission from the astrophysically interesting isobaric analog state in 23Mg.

Abstract

Utilizing the $^{24}\mathrm{Mg}(p, 2n)$ reaction and unique particle telescopes, beta-delayed proton emission from $^{23}\mathrm{Al}$ proceeding via its isobaric analog state in $^{23}\mathrm{Mg}$ has been observed. The relevant proton group was detected at 223\ifmmode\pm\else\textpm\fi{}20 keV with a proton decay branching ratio of 3.5\ifmmode\pm\else\textpm\fi{}1.9%. The proton width determined for this state is approximately an order of magnitude larger than that predicted by a full-basis $1s\ensuremath{-}0d$ shell model calculation which includes the expected isospin mixing. In addition, the resulting resonance strength (45\ifmmode\pm\else\textpm\fi{}25 meV) has important astrophysical implications.