Neutron-capture rates for explosive nucleosynthesis: the case of⁶⁸Ni(n,γ)⁶⁹Ni

Abstract

Neutron-capture reactions play an important role in heavy element nucleosynthesis, since they are the driving force for the two processes that create the vast majority of the heavy elements. When a neutron capture occurs on a short-lived nucleus, it is extremely challenging to study the reaction directly and therefore the use of indirect techniques is essential. The present work reports on such an indirect measurement that provides strong constraints on the 68 Ni(n,γ) 69 Ni reaction rate. Before the present results, this reaction was unconstrained and the purely theoretical reaction rate was highly uncertain. The new uncertainty on the reaction rate based on the present experiment is approximately a factor of 3. The commonly used reaction libraries JINA-REACLIB and BRUSLIB are in relatively good agreement with the experimental rate. The impact of the new rate on weak r-process calculations is discussed.

Reference database for photon strength functions

“…actions. A similar situation is found in the beta-Oslo method [54][55][56] for which the nucleus of interest is populated by β -decay. In these cases, a good knowledge of the populated spin distribution is crucial for a proper determination of the PSF by the Oslo method, as being recently studied in Ref.…”

“…Recently, the Oslo method has been further developed to allow for the study of the NLDs and PSFs in more neutronrich nuclei, either via the analysis of experimental data following beta-decay, the so-called beta-Oslo method [54][55][56] or using inverse kinematic reactions [57]. It is important to note that both of these newly developed methods measure particle-γ coincidences and use these coincidences to obtain excitation energy E i versus γ-ray energy matrices to which the Oslo method is applied.…”

β-decay half-lives of neutron-rich nuclides in theA=100–110mass region

“…This experiment was the first-ever application of the TAS technique with a fast beam produced via projectile fragmentation. Results from later experiments with roughly the same experimental setup have already been published [20][21][22]. The extracted β-decay feeding intensity distributions for the nuclides in the present work will be presented in forthcoming papers.…”

The Beta-Oslo Method: Experimentally Constrained ( $$n,\gamma $$ ) Reaction Rates Relevant to the r-Process

“…The beta-Oslo method is capable of extracting NLDs and γSFs of neutron-rich nuclei, enabling an indirect way to experimentally constrain (n, γ) reaction rates of relevance to the r-process. So far, three reaction rates have been inferred: 75 Ge(n, γ) 76 Ge [8], 69 Ni(n, γ) 70 Ni [9] and 68 Ni(n, γ) 69 Ni [26]. In the future, many more rates will be constrained with this technique, to the benefit of r-process nucleosynthesis calculations and our understanding of NLDs and γSFs.…”