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A promising astrophysical site to produce the lighter heavy elements of the first r -process peak (Z = 38 âˆ' 47) is the moderately neutron-rich (0.4 < Y e < 0.5) neutrino-driven ejecta of explosive environments, such as core-collapse supernovae and neutron star mergers, where the weak r -process operates. This nucleosynthesis exhibits uncertainties from the absence of experimental data from (α, xn) reactions on neutron-rich nuclei, which are currently based on statistical model estimates. In this work, we report on a new study of the nuclear reaction impact using a Monte Carlo approach and improved (α, xn) rates based on the Atomki-V2 α optical model potential. We compare our results with observations from an up-to-date list of metal-poor stars with [Fe/H] < âˆ'1.5 to find conditions of the neutrino-driven wind where the lighter heavy elements can be synthesized. We identified a list of (α, xn) reaction rates that affect key elemental ratios in different astrophysical conditions. Our study aims to motivate more nuclear physics experiments on (α, xn) reactions using the current and new generation of radioactive beam facilities and also more observational studies of metal-poor stars. [ABSTRACT FROM AUTHOR]

Excited states in the neutron-rich 121, 123, 125Ag were studied via the fragmentation of a 136Xe beam at 120MeV/nucleon in a thick 9Be target. The levels in 121Ag were populated in the $ \beta$ decay of 121Pd while those assigned to 123, 125Ag were identified via isomer spectroscopy. The transitions identified in 121Ag are consistent with the $ \gamma$ -rays reported in 117, 119Ag . The newly observed transitions were placed in the level schemes of 123, 125Ag based on the analysis of $ \gamma$ - $ \gamma$ coincidences and the systematics. We attribute the onset of isomerism in the 123, 125Ag isotopes to the drop in energy of the negative-parity levels similar to the 5- state in the even-even Cd cores. The proposed level scheme for 125Ag is well described by the NuShellX shell model calculations. [ABSTRACT FROM AUTHOR]

Decay properties of neutron-deficient exotic nuclei close to A=80 have been investigated at the IGISOL facility. The studied nuclei, 81Y, 81Sr, 81mKr, 85Nb, 85Zr, 86Mo and 86Nb, were produced by a 32S beam from the Jyväskylä isochronous cyclotron on 54Fe and natNi targets. The internal conversion coefficient for a 190.5 keV isomeric transition in 81mKr has been measured and the internal transition rate has been determined. The internal transition rate has been used to estimate a neutrino capture rate on 81Br, which yields a log ft of 5.13±0.09 for the reaction 81Br( ν, e-)81mKr. A new isomer with a half-life of 3.3±0.9 s has been observed in 85Nb. The existence of an earlier reported isomer with a half-life of 56 s in 86Nb has not been confirmed. [ABSTRACT FROM AUTHOR]

Despite a lot of experimental and theoretical progress the question of the r-process site and the origin of the heavy elements in nature remains one of the biggest open questions in nuclear astrophysics. I discuss the need for experimental nuclear data and review recent progress made at rare isotope beam facilities. In particular, I summarize some recent experiments performed at the NSCL Coupled Cyclotron Facility at MSU with beams of r-process nuclei, including the measurement of the half-life of 78Ni. [Copyright &y& Elsevier]

With the aim of improving nucleosynthesis calculations, we performed for the first time, a direct high-precision mass measurement on the waiting point in the astrophysical rp-process 72Kr. We used the ISOLTRAP Penning trap mass spectrometer located at ISOLDE/CERN. The measurement yielded a relative mass uncertainty of δ m/ m = 1.2×10-7. In addition, the masses of 73Kr and 74Kr were measured directly with relative mass uncertainties of 1.0×10-7 and 3×10-8, respectively. We analyzed the role of 72Kr in the rp-process during X-ray bursts using the ISOLTRAP and previous mass values of 72-74Kr. [ABSTRACT FROM AUTHOR]

A series of beta decay experiments on nuclei near the Z = N line has been performed using the ISOL technique at the IGISOL facility in Jyväskylä and at ISOLDE, CERN. The decay properties of these neutron-deficient nuclei are important in astrophysics as well as in the studies of isospin symmetry. [ABSTRACT FROM AUTHOR]

Abstract: A summary of the importance of rare isotopes in the understanding of the origin of the elements and accreting neutron stars is presented. [Copyright &y& Elsevier]

Abstract: Atomic masses play an important role in nuclear physics and astrophysics. The need of experimental mass values for unstable nuclides has triggered the development of a wide range of mass measurement techniques, with devices installed at many laboratories around the world. We have implemented a time-of-flight–magnetic-rigidity technique at the National Superconducting Cyclotron Laboratory (NSCL) that includes a position measurement for magnetic rigidity corrections and uses the A1900 separator and the S800 spectrograph. We performed a successful first experiment measuring masses of neutron-rich isotopes in the region of 20–30, important for calculations of processes occurring in the crust of accreting neutron stars. The masses of 16 nuclei were determined, for 61V, 63Cr, 66Mn, and 74Ni for the first time, with atomic mass excesses of −30.510(890)MeV, −35.280(650)MeV, −36.900(790)MeV, and −49.210(990)MeV, respectively. The mass resolution achieved was 1.8×10−4. [Copyright &y& Elsevier]

The astrophysical p-process is responsible for the origin of the proton rich nuclei,which are heavier than iron. A huge network involving thousands of reaction rates is necessary to calculate the final p-abundances. But not all rates included in the network have a strong influence on the p-nuclei abundances. The p-process was investigated using a full nuclear reaction network for a type II supernova explosion when the shock front passes through the O/Ne layer. Calculations were done with a multi-layer model adopting the seed of a pre-explosion evolution of a 25 mass star. In extensive simulations we investigated the impact of single reaction rates on the final p-abundances. The results are important for the strategy of future experiments in this field. [Copyright &y& Elsevier]

As one of a series of physics cases to demonstrate the unique benefit of the new Jet Experiments in Nuclear Structure and Astrophysics (JENSA) gas-jet target for enabling next-generation transfer reaction studies, the 14N (p,r)12N reaction was studied for the first time, using a pure jet of nitrogen, in an attempt to resolve conflicting information on the structure of 12N. A potentially new level at 4.561-MeV excitation energy in 12N was found. [ABSTRACT FROM AUTHOR]

New radioactive ion beam (RIB) facilities will push further away from stability and enable the next generation of nuclear physics experiments. Of great importance to the future of RIB physics are scattering, transfer, and capture reaction measurements of rare, exotic, and unstable nuclei on light targets such as hydrogen and helium. These measurements require targets that are dense, highly localized, and pure. Targets must also accommodate the use of large area silicon detector arrays, high-efficiency gamma arrays, and heavy ion detector systems to efficiently measure the reaction products. To address these issues, the Jet Experiments in Nuclear Structure and Astrophysics (JENSA) Collaboration has designed, built, and characterized a supersonic gas jet target, capable of providing gas areal densities on par with commonly used solid targets within a region of a few millimeters diameter. Densities of over 5×10 18 atoms/cm 2 of helium have been achieved, making the JENSA gas jet target the most dense helium jet achieved so far. [ABSTRACT FROM AUTHOR]

Abstract: Observed neutron-capture elemental abundances in metal-poor stars, along with ongoing analysis of the extremely metal-poor Eu-enriched sub-class provide new guidance for astrophysical models aimed at finding the r-process sites. The present paper emphasizes the importance of nuclear physics parameters entering in these models, particularly β-decay properties of neutron-rich nuclei. In this context, several r-process motivated β-decay experiments performed at the National Superconducting Cyclotron Laboratory (NSCL) are presented, including a summary of results and impact on model calculations. [Copyright &y& Elsevier]

The level structure of 30S was studied at the NSCL by using neutron removal reactions with a radioactive 31S beam. The γ-decay from excited states in 30S was measured in a Ge-detector array. The results discussed for this work will reduce the uncertainties in the determination of the astrophysical 29P(p,γ)30S reaction rate under rp-process conditions. [Copyright &y& Elsevier]

The light curves of type I X-ray bursts (XRBs) result from energy released from the atmosphere of a neutron star when accreted hydrogen and helium ignite and burn explosively via the rp-process. Since charged particle reaction rates are both density and very temperature dependent, a simulation model must provide accurate values of these variables to predict the reaction flow. This paper uses a self-consistent one-dimensional model calculation with a constant accretion rate of and reports on the detailed rp-process reaction flow of a given burst. [Copyright &y& Elsevier]

The regions around the doubly magic nuclei 100Sn and 78Ni are of great interest from a nuclear structure standpoint. These nuclei also play a key role in the astrophysical rp- and r-processes, respectively. Recently, nuclei in these regions were studied at the Coupled Cyclotron Facility at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. [Copyright &y& Elsevier]