Evidence for Gamow-Teller Decay of ^{78}Ni Core from Beta-Delayed Neutron Emission Studies.
The β-delayed neutron emission of ^{83,84}Ga isotopes was studied using the neutron time-of-flight technique. The measured neutron energy spectra showed emission from states at excitation energies high above the neutron separation energy and previously not observed in the β decay of midmass nuclei. The large decay strength deduced from the observed intense neutron emission is a signature of Gamow-Teller transformation. This observation was interpreted as evidence for allowed β decay to ^{78}Ni core-excited states in ^{83,84}Ge favored by shell effects. We developed shell model calculations in the proton fpg_{9/2} and neutron extended fpg_{9/2}+d_{5/2} valence space using realistic interactions that were used to understand measured β-decay lifetimes. We conclude that enhanced, concentrated β-decay strength for neutron-unbound states may be common for very neutron-rich nuclei. This leads to intense β-delayed high-energy neutron and strong multineutron emission probabilities that in turn affect astrophysical nucleosynthesis models.
Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA.|ISOLDE, EP Department, CERN, CH-1211 Geneva, Switzerland.
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Madurga
Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA.
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SV
Paulauskas
Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA.|Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA.
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Grzywacz
Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA.
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D
Miller
Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA.
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Bardayan
Department of Nuclear Engineering, University of California, Berkeley, Berkeley, California 94702, USA.
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JC
Batchelder
Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA.
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Brewer
Department of Physics and Astronomy, Rutgers University, New Brunswick, New Jersey 08903, USA.
J A
JA
Cizewski
Faculty of Physics, University of Warsaw, Warszawa PL 00-681, Poland.
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A
Fijałkowska
Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA.
C J
CJ
Gross
Department of Physics and Astronomy, Rutgers University, New Brunswick, New Jersey 08903, USA.
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ME
Howard
Department of Physics, Colorado School of Mines, Golden, Colorado 80401, USA.
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SV
Ilyushkin
Department of Physics and Astronomy, Rutgers University, New Brunswick, New Jersey 08903, USA.
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B
Manning
Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
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Matoš
Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA.|Department of Physics and Astronomy, Austin Peay State University, Clarksville, Tennessee 37044, USA.
A J
AJ
Mendez
Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA.|Faculty of Physics, University of Warsaw, Warszawa PL 00-681, Poland.
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Miernik
Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA.
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Padgett
Oak Ridge Associated Universities, Oak Ridge, Tennessee 37831, USA.
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WA
Peters
Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
B C
BC
Rasco
Department of Physics and Astronomy, Rutgers University, New Brunswick, New Jersey 08903, USA.
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A
Ratkiewicz
Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA.
K P
KP
Rykaczewski
Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA.
D W
DW
Stracener
Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA.
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EH
Wang
Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA.|Heavy Ion Laboratory, University of Warsaw, Warsaw PL 02-093, Poland.
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Wolińska-Cichocka
Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
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Zganjar