Observation of Giant Gamow-Teller Strength in ($p, n$) Reactions

In ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}(p, n){}_{}{}^{90}{}_{}{}^{}\mathrm{Nb}$ spectra for $E_p=35\mathrm{} \mathrm{and} 45$ MeV, we observe a strong enhancement of the $T=4\mathrm{}$ continuum over a range of excitation energies (full width at half-maximum of 4.2 ± 0.4 MeV) centered at 8.4±0.3 MeV. The data are consistent with an interpretation of the broad peak as a ${(\pi g_{\frac{7}{2}}, \nu {g_{\frac{9}{2}}}^{-1\mathrm{}})}_{1^{+}}$ excitation wich corresponds to the giant magneticdipole resonance. Similar structure is observed near the isobaric analog state of ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{120}{}_{}{}^{}\mathrm{Sn}$, and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$.