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Massive stars are a major source of chemical elements in the cosmos, ejecting freshly produced nuclei through winds and core-collapse supernova explosions into the interstellar medium. Among the material ejected, long-lived radioisotopes, such as 60 Fe (iron) and 26 Al (aluminum), offer unique signs of active nucleosynthesis in our galaxy. There is a long-standing discrepancy between the observed 60 Fe/ 26 Al ratio by γ-ray telescopes and predictions from supernova models. This discrepancy has been attributed to uncertainties in the nuclear reaction networks producing 60 Fe, and one reaction in particular, the neutron-capture on 59 Fe. Here we present experimental results that provide a strong constraint on this reaction. We use these results to show that the production of 60 Fe in massive stars is higher than previously thought, further increasing the discrepancy between observed and predicted 60 Fe/ 26 Al ratios. The persisting discrepancy can therefore not be attributed to nuclear uncertainties, and points to issues in massive-star models. 60Fe and 26Al provide insights about active nucleosynthesis in our galaxy and there is a discrepancy between observed and theoretically predicted ratios. Here, the authors show that this discrepancy is higher than previously found.

Neutron-capture cross sections of neutron-rich nuclei are calculated using a Hauser–Feshbach model when direct experimental cross sections cannot be obtained. A number of codes to perform these calculations exist, and each makes different assumptions about the underlying nuclear physics. We investigated the systematic uncertainty associated with the choice of Hauser-Feshbach code used to calculate the neutron-capture cross section of a short-lived nucleus. The neutron-capture cross section for 73 Zn (n, γ ) 74 Zn was calculated using three Hauser-Feshbach statistical model codes: TALYS, CoH, and EMPIRE. The calculation was first performed without any changes to the default settings in each code. Then an experimentally obtained nuclear level density (NLD) and γ -ray strength function ( γ SF ) were included. Finally, the nuclear structure information was made consistent across the codes. The neutron-capture cross sections obtained from the three codes are in good agreement after including the experimentally obtained NLD and γ SF , accounting for differences in the underlying nuclear reaction models, and enforcing consistent approximations for unknown nuclear data. It is possible to use consistent inputs and nuclear physics to reduce the differences in the calculated neutron-capture cross section from different Hauser-Feshbach codes. However, ensuring the treatment of the input of experimental data and other nuclear physics are similar across multiple codes requires a careful investigation. For this reason, more complete documentation of the inputs and physics chosen is important.

Conservation laws are deeply related to any symmetry present in a physical system 1 , 2 . Analogously to electrons in atoms exhibiting spin symmetries 3 , it is possible to consider neutrons and protons in the atomic nucleus as projections of a single fermion with an isobaric spin (isospin) of t  = 1/2 (ref.  4 ). Every nuclear state is thus characterized by a total isobaric spin T and a projection T z —two quantities that are largely conserved in nuclear reactions and decays 5 , 6 . A mirror symmetry emerges from this isobaric-spin formalism: nuclei with exchanged numbers of neutrons and protons, known as mirror nuclei, should have an identical set of states 7 , including their ground state, labelled by their total angular momentum J and parity π . Here we report evidence of mirror-symmetry violation in bound nuclear ground states within the mirror partners strontium-73 and bromine-73. We find that a J   π  = 5/2 − spin assignment is needed to explain the proton-emission pattern observed from the T  = 3/2 isobaric-analogue state in rubidium-73, which is identical to the ground state of strontium-73. Therefore the ground state of strontium-73 must differ from its J   π  = 1/2 − mirror bromine-73. This observation offers insights into charge-symmetry-breaking forces acting in atomic nuclei. Observations of the decay of 73 Sr, when compared to its mirror nucleus 73 Br, indicate that the spin assignment of their ground states differ, demonstrating mirror-symmetry violation.

The nucleosynthesis path of the γ-process is predominantly governed by the branching points at which the flow of the initial (γ,n) is redirected by either (γ,p) or (γ,α) reactions. In this work, the inverse reactions, proton and α capture on 108Cd were studied in order to aid in verification of the 112Sn isotope as a potential branching point in the γ-process. The results of the first measurement with a γ-summing detector, HECTOR, are compared with previous measurements found in the literature and with NON-SMOKER predictions. The results of this work will provide input for Hauser-Feshbach calculations to obtain the γ induced reaction rates.

The first measurements of the capture reactions for the astrophysical γ-process using HECTOR, a total absorption spectrometer are presented. Two reactions: 102Pd(p,γ)103Ag and 90Zr(α,γ)94Mo were measured using the γ-summing technique. The results are compared with the previous measurements found in the literature and with the NON-SMOKER predictions. The results from the current work are in a good agreement with the data found in the literature and serve as a test of the newly developed detector.

Massive stars are a major source of chemical elements in the cosmos, ejecting freshly produced nuclei through winds and core-collapse supernova explosions into the interstellar medium. Among the material ejected, long-lived radioisotopes, such as 60Fe (iron) and 26Al (aluminum), offer unique signs of active nucleosynthesis in our galaxy. There is a long-standing discrepancy between the observed 60Fe/26Al ratio by γ-ray telescopes and predictions from supernova models. This discrepancy has been attributed to uncertainties in the nuclear reaction networks producing 60Fe, and one reaction in particular, the neutron-capture on 59Fe. Here we present experimental results that provide a strong constraint on this reaction. We use these results to show that the production of 60Fe in massive stars is higher than previously thought, further increasing the discrepancy between observed and predicted 60Fe/26Al ratios. The persisting discrepancy can therefore not be attributed to nuclear uncertainties, and points to issues in massive-star models.

Massive stars are a major source of chemical elements in the cosmos, ejecting freshly produced nuclei through winds and core-collapse supernova explosions into the interstellar medium. Among the material ejected, long lived radioisotopes, such as 60Fe (iron) and 26Al (aluminum), offer unique signs of active nucleosynthesis in our galaxy. There is a long-standing discrepancy between the observed 60Fe/26Al ratio by {\\gamma}-ray telescopes and predictions from supernova models. This discrepancy has been attributed to uncertainties in the nuclear reaction networks producing 60Fe, and one reaction in particular, the neutron-capture on 59Fe. Here we present experimental results that provide a strong constraint on this reaction. We use these results to show that the production of 60Fe in massive stars is higher than previously thought, further increasing the discrepancy between observed and predicted 60Fe/26Al ratios. The persisting discrepancy can therefore not be attributed to nuclear uncertainties, and points to issues in massive-star models.

Massive stars are a major source of chemical elements in the cosmos, ejecting freshly produced nuclei through winds and core-collapse supernova explosions into the interstellar medium. Among the material ejected, long-lived radioisotopes, such as Fe (iron) and Al (aluminum), offer unique signs of active nucleosynthesis in our galaxy. There is a long-standing discrepancy between the observed Fe/ Al ratio by γ-ray telescopes and predictions from supernova models. This discrepancy has been attributed to uncertainties in the nuclear reaction networks producing Fe, and one reaction in particular, the neutron-capture on Fe. Here we present experimental results that provide a strong constraint on this reaction. We use these results to show that the production of Fe in massive stars is higher than previously thought, further increasing the discrepancy between observed and predicted Fe/ Al ratios. The persisting discrepancy can therefore not be attributed to nuclear uncertainties, and points to issues in massive-star models.

We have developed and tested an experimental technique for the measurement of low-energy (p,n) reactions in inverse kinematics relevant to nuclear astrophysics. The proposed setup is located at the ReA3 facility at the National Superconducting Cyclotron Laboratory. In the current approach, we operate the beam-transport line in ReA3 as a recoil separator while tagging the outgoing neutrons from the (p,n) reactions with the low-energy neutron detector array (LENDA). The developed technique was verified by using the \\(^{40}\\)Ar(p,n)\\(^{40}\\)K reaction as a probe. The results of the proof-of-principle experiment with the \\(^{40}\\)Ar beam show that cross-section measurements within an uncertainty of \\(\\sim\\)25\\% are feasible with count rates up to 7 counts/mb/pnA/s. In this article, we give a detailed description of the experimental setup, and present the analysis method and results from the test experiment. Future plans on using the technique in experiments with the separator for capture reactions (SECAR) that is currently being commissioned are also discussed.

A novel technique has been developed, which will open exciting new opportunities for studying the very neutron-rich nuclei involved in the r-process. As a proof-of-principle, the \\(\\gamma\\)-spectra from the \\(\\beta\\)-decay of \\(^{76}\\)Ga have been measured with the SuN detector at the National Superconducting Cyclotron Laboratory. The nuclear level density and \\(\\gamma\\)-ray strength function are extracted and used as input to Hauser-Feshbach calculations. The present technique is shown to strongly constrain the \\(^{75}\\)Ge(\\(n,\\gamma\\))\\(^{76}\\)Ge cross section and reaction rate.