$\beta$ decay of ${}^{97}\mathrm{Ag}$:  Evidence for the Gamow-Teller resonance near ${}^{100}\mathrm{Sn}$

In two complementary measurements, a cubelike array of 6 Euroball-Cluster germanium detectors and a total-absorption $\gamma$-spectrometer were used to investigate the $\beta$ decay of ${}^{97}\mathrm{Ag}$, a three proton-hole nucleus with respect to the ${}^{100}\mathrm{Sn}$ core. The half-life and $Q_{\mathrm{EC}}$ value of the decay of the ${9/2}^{+}$ ground state of ${}^{97}\mathrm{Ag}$ were determined to be 25.9(4) s and 6.98(11) MeV, respectively. A total of 603 $\gamma$ rays (578 new) was observed, and 151 levels (132 new) in ${}^{97}\mathrm{Pd}$ have been identified. An interesting $\beta$-delayed $\gamma$ cascade was observed, which comprises 6 $\gamma$-transitions with a deexcitation pattern involving an initial increase of the level spin. The Gamow-Teller (GT) $\beta$-decay strength distributions from the two measurements reveal a large GT resonance around 4 MeV with a width of about 1.8 MeV. The hindrance factor for the total GT strength, summed from the ground state up to 6 MeV excitation energy in ${}^{97}\mathrm{Pd}$, amounts to 4.3(6) with reference to a shell-model prediction. This factor is discussed in comparison with a core polarization and a Monte Carlo shell-model calculation.