Modification of the Brink-Axel Hypothesis for High Temperature Nuclear Weak Interactions

Abstract

We present shell model calculations of electron capture strength distributions in A=28 nuclei and computations of the corresponding capture rates in supernova core conditions. We find that in these nuclei the Brink-Axel hypothesis for the distribution of Gamow-Teller strength fails at low and moderate initial excitation energy, but may be a valid tool at high excitation. The redistribution of GT strength at high initial excitation may affect capture rates during collapse. If these trends which we have found in lighter nuclei also apply for the heavier nuclei which provide the principal channels for neutronization during stellar collapse, then there could be two implications for supernova core electron capture physics. First, a modified Brink-Axel hypothesis could be a valid approximation for use in collapse codes. Second, the electron capture strength may be moved down significantly in transition energy, which would likely have the effect of increasing the overall electron capture rate during stellar collapse.

arXiv comment15 pages, 19 figures

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Cited by in corpus (25)

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• Thermal QRPA with Skyrme interactions and supernova neutral-current neutrino-nucleus reactions
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• Description of ${}^{93}$Nb stellar electron-capture rates by the Projected Shell Model
• A modified Brink-Axel hypothesis for astrophysical Gamow-Teller transitions
• New experimental constraint on the ${}^{185}$W($n,\gamma$)${}^{186}$W cross section
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• The Skyrme-TQRPA calculations of electron capture on hot nuclei in pre-supernova environment
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• Lepton capture rates due to isotopes of vanadium in astrophysical environment
• Neutrino cooling rates due to nickel isotopes for presupernova evolution of massive stars
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• Comprehensive test of the Brink-Axel hypothesis in the energy region of the pygmy dipole resonance
• Stellar ${\beta }^{-}$-decay rate of ${}^{63}$Ni and its impact on the $s$-process nucleosynthesis in massive stars