The β-delayed neutron emission of Ga83,84 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 Ni78 core-excited states in Ge83,84 favored by shell effects. We developed shell model calculations in the proton fpg9/2 and neutron extended fpg9/2+d5/2 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.
Publication Source (Journal or Book title)
Physical Review Letters
Madurga, M., Paulauskas, S., Grzywacz, R., Miller, D., Bardayan, D., Batchelder, J., Brewer, N., Cizewski, J., Fijałkowska, A., Gross, C., Howard, M., Ilyushkin, S., Manning, B., Matoš, M., Mendez, A., Miernik, K., Padgett, S., Peters, W., Rasco, B., Ratkiewicz, A., Rykaczewski, K., Stracener, D., Wang, E., Wolińska-Cichocka, M., & Zganjar, E. (2016). Evidence for Gamow-Teller Decay of Ni 78 Core from Beta-Delayed Neutron Emission Studies. Physical Review Letters, 117 (9) https://doi.org/10.1103/PhysRevLett.117.092502