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

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