Gamow-Teller (GT) strength has been extracted from cross sections for the reaction ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$(n,p${)\mathrm{}}^{54}$Mn at 0°, 2.5°, 5°, 8°, and 12°, and for an incident energy of 298 MeV. This determination of the ${\beta }^{+}$ GT strength $S_{+}$ allows for the first time a full test of the Ikeda sum rule. These data also show that the best available shell-model calculations overestimate this strength by a factor of 2. This result is significant in models of supernovae since electron capture in (fp)-shell nuclei, which is proportional to $S_{+}$, depletes the relativistic electron gas in precollapse stars.

• Received 27 April 1987

DOI:https://doi.org/10.1103/PhysRevLett.59.439