Experimental constraint on stellar electron-capture rates from the Sr 88 (t, He 3 +γ) Rb 88 reaction at 115 MeV/u

J. C. Zamora, R. G.T. Zegers, Sam M. Austin, D. Bazin, B. A. Brown, P. C. Bender, H. L. Crawford, J. Engel, A. Falduto, A. Gade, P. Gastis, B. Gao, T. Ginter, C. J. Guess, S. Lipschutz, B. Longfellow, A. O. Macchiavelli, K. Miki, E. Ney, S. NojiJ. Pereira, J. Schmitt, C. Sullivan, R. Titus, D. Weisshaar

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Abstract

The Gamow-Teller strength distribution from Sr88 was extracted from a (t,He3+γ) experiment at 115MeV/u to constrain estimates for the electron-capture rates on nuclei around N=50, between and including Ni78 and Sr88, 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 0.1±0.05. Except for a very-weak transition that could come from the 2.231-MeV 1+ state, no γ lines that could be associated with the decay of known 1+ 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 N=50. 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 1+ state in Rb88 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.

Original languageEnglish
Article number032801
JournalPhysical Review C
Volume100
Issue number3
DOIs
Publication statusPublished - 2019 Sep 23

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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    Zamora, J. C., Zegers, R. G. T., Austin, S. M., Bazin, D., Brown, B. A., Bender, P. C., Crawford, H. L., Engel, J., Falduto, A., Gade, A., Gastis, P., Gao, B., Ginter, T., Guess, C. J., Lipschutz, S., Longfellow, B., Macchiavelli, A. O., Miki, K., Ney, E., ... Weisshaar, D. (2019). Experimental constraint on stellar electron-capture rates from the Sr 88 (t, He 3 +γ) Rb 88 reaction at 115 MeV/u. Physical Review C, 100(3), [032801]. https://doi.org/10.1103/PhysRevC.100.032801