"Stretched"6−T=1State inAl24Observed in the ReactionMg24(p, n)Al24

An isovector $M6\mathrm{}$ transition is observed for the first time in a ($p, n$) reaction. A prominent peak was seen at $E_x=5.545\mathrm{}\pm 0.025$ MeV in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Al}$ in the study of the reaction ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}(p, n){}_{}{}^{24}{}_{}{}^{}\mathrm{Al}$ at $E_p=35\mathrm{}$ MeV. This state is interpreted as the "stretched" particle-hole state with $J^{\pi }=6^{-}$, $T=1\mathrm{}$, which corresponds to the 15.13-MeV state in ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$. Distorted-wave Born approximation analysis gives a result consistent with those for ($p, p^{\prime }$) and ($e, e^{\prime }$) reactions, indicating that at least 50% of the isovector $M6\mathrm{}$ strength is missing.