Abstract
The Gamow-Teller strength distribution from was extracted from a experiment at to constrain estimates for the electron-capture rates on nuclei around , between and including and , which are important for the late evolution of core-collapse supernovae. The observed Gamow-Teller strength below an excitation energy of 8 MeV was consistent with zero and below 10 MeV amounted to . Except for a very-weak transition that could come from the 2.231-MeV state, no lines that could be associated with the decay of known states were identified. The derived electron-capture rate from the measured strength distribution is more than an order of magnitude smaller than rates based on the single-state approximation presently used in astrophysical simulations for most nuclei near . Rates based on shell-model and quasiparticle random-phase approximation calculations that account for Pauli-blocking and core-polarization effects provide better estimates than the single-state approximation, although a relatively strong transition to the first state in is not observed in the data. Pauli-unblocking effects due to high stellar temperatures could partially counter the low electron-capture rates. The new data serve as a zero-temperature benchmark for constraining models used to estimate such effects.
- Received 1 February 2019
- Revised 1 April 2019
DOI:https://doi.org/10.1103/PhysRevC.100.032801
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