β decay of ⁹⁷Ag:  Evidence for the Gamow-Teller resonance near ¹⁰⁰Sn

In two complementary measurements, a cubelike array of 6 Euroball-Cluster germanium detectors and a total-absorption γ-spectrometer were used to investigate the β decay of ⁹⁷Ag, a three proton-hole nucleus with respect to the ¹⁰⁰Sn core. The half-life and Q_EC value of the decay of the 9/2⁺ ground state of ⁹⁷Ag were determined to be 25.9(4) s and 6.98(11) MeV, respectively. A total of 603 γ rays (578 new) was observed, and 151 levels (132 new) in ⁹⁷Pd have been identified. An interesting β-delayed γ cascade was observed, which comprises 6 γ-transitions with a deexcitation pattern involving an initial increase of the level spin. The Gamow-Teller (GT) β-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 ⁹⁷Pd, 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.