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ISOLDE Collaboration(Nacher, E. et al), Parra, S., Rubio, B., Agramunt, J., Algora, A., Morales, A. I., et al. (2026). Experimental Gamow-Teller strength in the β decay of the rp-process waiting-point nucleus 64Ge and its impact on stellar weak-decay rates. Phys. Lett. B, 880, 140800–4pp.
Abstract: The beta decay of the rp-process waiting-point nucleus 64Ge plays a key role in Type-I X-ray bursts. Reliable theoretical predictions at the high temperatures and densities of these environments require models capable of reproducing the relevant Gamow-Teller (GT) strength under terrestrial conditions. We report a measurement of the B(GT) distribution in the decay of 64Ge using the Total Absorption Gamma-ray Spectroscopy technique at CERN-ISOLDE. The experimentally determined B(GT) distribution is compared with large-scale shell-model calculations and with existing theoretical approaches. While shell-model-based calculations provide a good description of the data, QRPA results show significant discrepancies. Stellar weak-decay rates derived from our experimental B(GT) distribution provide the first experimentally constrained rates for 64Ge, and a stringent benchmark for nuclear-structure models employed in rp-process simulations.
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