Gamow-Teller strength in 54Fe and 56Fe

Through a sequence of large scale shell model calculations, total Gamow-Teller strengths ($S_+$ and $S_-$) in $^{54}$Fe and $^{56}$Fe are obtained. They reproduce the experimental values once the $\sigma\tau$ operator is quenched by the standard factor of $0.77$. Comparisons are made with recent Shell Model Monte Carlo calculations. Results are shown to depend critically on the interaction. From an analysis of the GT+ and GT$-$ strength functions it is concluded that experimental evidence is consistent with the $3(N-Z)$ sum rule.