@article{611aabc992f34e56806d4952f935055e,
title = "Enhanced low-energy γ-decay strength of Ni 70 and its robustness within the shell model",
abstract = "Neutron-capture reactions on very neutron-rich nuclei are essential for heavy-element nucleosynthesis through the rapid neutron-capture process, now shown to take place in neutron-star merger events. For these exotic nuclei, radiative neutron capture is extremely sensitive to their γ-emission probability at very low γ energies. In this work, we present measurements of the γ-decay strength of Ni70 over the wide range 1.3≤Eγ≤8 MeV. A significant enhancement is found in the γ-decay strength for transitions with Eγ<3 MeV. At present, this is the most neutron-rich nucleus displaying this feature, proving that this phenomenon is not restricted to stable nuclei. We have performed E1-strength calculations within the quasiparticle time-blocking approximation, which describe our data above Eγ≃5 MeV very well. Moreover, large-scale shell-model calculations indicate an M1 nature of the low-energy γ strength. This turns out to be remarkably robust with respect to the choice of interaction, truncation, and model space, and we predict its presence in the whole isotopic chain, in particular the neutron-rich Ni72,74,76.",
author = "Larsen, {A. C.} and Midtb{\o}, {J. E.} and M. Guttormsen and T. Renstr{\o}m and Liddick, {S. N.} and A. Spyrou and S. Karampagia and Brown, {B. A.} and O. Achakovskiy and S. Kamerdzhiev and Bleuel, {D. L.} and A. Couture and Campo, {L. Crespo} and Crider, {B. P.} and Dombos, {A. C.} and R. Lewis and S. Mosby and F. Naqvi and G. Perdikakis and Prokop, {C. J.} and Quinn, {S. J.} and S. Siem",
note = "Funding Information: A.C.L. gratefully acknowledges funding of this research from the European Research Council, ERC-STG-2014 Grant Agreement No. 637686. A.C.L. acknowledges support from the ChETEC COST Action (CA16117), supported by COST (European Cooperation in Science and Technology). Financial support from the Research Council of Norway, Project Grant No. 210007 (L.C.C., T.R., and S.S.) is gratefully acknowledged. We would like to thank N. Shimizu and M. Hjorth-Jensen for valuable input to the shell-model calculations, and T. Engeland and E. Osnes for stimulating discussions. A.C.L. and J.E.M. are grateful to the National Superconducting Cyclotron Laboratory at Michigan State University and to Lawrence Berkeley National Laboratory for their hospitality during parts of this work, as well as to the US-Norway Fulbright Foundation for Educational Exchange for supporting our stay in the United States. kshell calculations were performed on the Abel, Stallo, and Fram HPC clusters at the University of Oslo and the University of Troms{\o}, respectively, supported by the Norwegian Research Council. The work of O.A. and S.K. has been supported by the Russian Science Foundation, Grant No. 16-12-10155. D.L.B. acknowledges the support of LLNL under Contract No. DE-AC52- 07NA27344. This material is based upon work supported by the Department of Energy/National Nuclear Security Administration under Awards No. DE-NA-0003180, No. DE-NA0003221, and No. DE-NA-0000979. This work was supported by the National Science Foundation under Grants No. PHY 1102511 (NSCL), No. PHY 1430152 (Joint Institute for Nuclear Astrophysics), No. PHY 1350234 (CAREER), and No. PHY 1404442. The LANL work was carried out under the auspices of the NNSA of the U.S. Department of Energy at Los Alamos National Laboratory under Contract No. DE-AC52-06NA25396. Some of the plots are made using Python 2.7 with Numpy and Matplotlib . Publisher Copyright: {\textcopyright} 2018 American Physical Society.",
year = "2018",
month = may,
day = "30",
doi = "10.1103/PhysRevC.97.054329",
language = "English",
volume = "97",
journal = "Physical Review C",
issn = "2469-9985",
publisher = "PHYSICAL REVIEW C",
number = "5",
}