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S Caldwell - One of the best experts on this subject based on the ideXlab platform.
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first results from the caribu facility mass measurements on the r Process Path
Physical Review Letters, 2013Co-Authors: J Van Schelt, D Lascar, G Savard, J A Clark, P F Bertone, S CaldwellAbstract:The Canadian Penning Trap mass spectrometer has made mass measurements of 33 neutron-rich nuclides provided by the new Californium Rare Isotope Breeder Upgrade facility at Argonne National Laboratory. The studied region includes the $^{132}\mathrm{Sn}$ double shell closure and ranges in $Z$ from In to Cs, with Sn isotopes measured out to $A=135$, and the typical measurement precision is at the 100 ppb level or better. The region encompasses a possible major waiting point of the astrophysical $r$ Process, and the impact of the masses on the $r$ Process is shown through a series of simulations. These first-ever simulations with direct mass information on this waiting point show significant increases in waiting time at Sn and Sb in comparison with commonly used mass models, demonstrating the inadequacy of existing models for accurate $r$-Process calculations.
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mass measurements near the r Process Path using the canadian penning trap mass spectrometer
Physical Review C, 2012Co-Authors: J Van Schelt, D Lascar, G Savard, J A Clark, S Caldwell, A ChaudhuriAbstract:The masses of 40 neutron-rich nuclides from $Z=51$ to 64 were measured at an average precision of $\ensuremath{\delta}m/m={10}^{\ensuremath{-}7}$ using the Canadian Penning Trap mass spectrometer at Argonne National Laboratory. The measurements, of fission fragments from a ${}^{252}$Cf spontaneous fission source in a helium gas catcher, approach the predicted Path of the astrophysical $r$ Process. Where overlap exists, this data set is largely consistent with previous measurements from Penning traps, storage rings, and reaction energetics, but large systematic deviations are apparent in $\ensuremath{\beta}$-endpoint measurements. Differences in mass excess from the 2003 Atomic Mass Evaluation of up to 400 keV are seen, as well as systematic disagreement with various mass models.
G J Mathews - One of the best experts on this subject based on the ideXlab platform.
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impact of new data for neutron rich heavy nuclei on theoretical models for r Process nucleosynthesis
Reports on Progress in Physics, 2017Co-Authors: Toshitaka Kajino, G J MathewsAbstract:Current models for the r Process are summarized with an emphasis on the key constraints from both nuclear physics measurements and astronomical observations. In particular, we analyze the importance of nuclear physics input such as beta-decay rates; nuclear masses; neutron-capture cross sections; beta-delayed neutron emission; probability of spontaneous fission, beta- and neutron-induced fission, fission fragment mass distributions; neutrino-induced reaction cross sections, etc. We highlight the effects on models for r-Process nucleosynthesis of newly measured β-decay half-lives, masses, and spectroscopy of neutron-rich nuclei near the r-Process Path. We overview r-Process nucleosynthesis in the neutrino driven wind above the proto-neutron star in core collapse supernovae along with the possibility of magneto-hydrodynamic jets from rotating supernova explosion models. We also consider the possibility of neutron star mergers as an r-Process environment. A key outcome of newly measured nuclear properties far from stability is the degree of shell quenching for neutron rich isotopes near the closed neutron shells. This leads to important constraints on the sites for r-Process nucleosynthesis in which freezeout occurs on a rapid timescale.
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impact of new data for neutron rich heavy nuclei on theoretical models for r Process nucleosynthesis
arXiv: Nuclear Theory, 2016Co-Authors: Toshitaka Kajino, G J MathewsAbstract:Current models for the $r$ Process are summarized with an emphasis on the key constraints from both nuclear physics measurements and astronomical observations. In particular, we analyze the importance of nuclear physics input such as beta-decay rates; nuclear masses; neutron-capture cross sections; beta-delayed neutron emission; probability of spontaneous fission, beta- and neutron-induced fission, fission fragment mass distributions; neutrino-induced reaction cross sections, etc. We highlight the effects on models for $r$-Process nucleosynthesis of newly measured $\beta$-decay half-lives, masses, and spectroscopy of neutron-rich nuclei near the $r$-Process Path. We overview r-Process nucleosynthesis in the neutrino driven wind above the proto-neutron star in core collapse supernovae along with the possibility of magneto-hydrodynamic jets from rotating supernova explosion models. We also consider the possibility of neutron star mergers as an r-Process environment. A key outcome of newly measured nuclear properties far from stability is the degree of shell quenching for neutron rich isotopes near the closed neutron shells. This leads to important constraints on the sites for $r$-Process nucleosynthesis in which freezeout occurs on a rapid timescale.
J Van Schelt - One of the best experts on this subject based on the ideXlab platform.
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first results from the caribu facility mass measurements on the r Process Path
Physical Review Letters, 2013Co-Authors: J Van Schelt, D Lascar, G Savard, J A Clark, P F Bertone, S CaldwellAbstract:The Canadian Penning Trap mass spectrometer has made mass measurements of 33 neutron-rich nuclides provided by the new Californium Rare Isotope Breeder Upgrade facility at Argonne National Laboratory. The studied region includes the $^{132}\mathrm{Sn}$ double shell closure and ranges in $Z$ from In to Cs, with Sn isotopes measured out to $A=135$, and the typical measurement precision is at the 100 ppb level or better. The region encompasses a possible major waiting point of the astrophysical $r$ Process, and the impact of the masses on the $r$ Process is shown through a series of simulations. These first-ever simulations with direct mass information on this waiting point show significant increases in waiting time at Sn and Sb in comparison with commonly used mass models, demonstrating the inadequacy of existing models for accurate $r$-Process calculations.
-
mass measurements near the r Process Path using the canadian penning trap mass spectrometer
Physical Review C, 2012Co-Authors: J Van Schelt, D Lascar, G Savard, J A Clark, S Caldwell, A ChaudhuriAbstract:The masses of 40 neutron-rich nuclides from $Z=51$ to 64 were measured at an average precision of $\ensuremath{\delta}m/m={10}^{\ensuremath{-}7}$ using the Canadian Penning Trap mass spectrometer at Argonne National Laboratory. The measurements, of fission fragments from a ${}^{252}$Cf spontaneous fission source in a helium gas catcher, approach the predicted Path of the astrophysical $r$ Process. Where overlap exists, this data set is largely consistent with previous measurements from Penning traps, storage rings, and reaction energetics, but large systematic deviations are apparent in $\ensuremath{\beta}$-endpoint measurements. Differences in mass excess from the 2003 Atomic Mass Evaluation of up to 400 keV are seen, as well as systematic disagreement with various mass models.
Toshitaka Kajino - One of the best experts on this subject based on the ideXlab platform.
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impact of new data for neutron rich heavy nuclei on theoretical models for r Process nucleosynthesis
Reports on Progress in Physics, 2017Co-Authors: Toshitaka Kajino, G J MathewsAbstract:Current models for the r Process are summarized with an emphasis on the key constraints from both nuclear physics measurements and astronomical observations. In particular, we analyze the importance of nuclear physics input such as beta-decay rates; nuclear masses; neutron-capture cross sections; beta-delayed neutron emission; probability of spontaneous fission, beta- and neutron-induced fission, fission fragment mass distributions; neutrino-induced reaction cross sections, etc. We highlight the effects on models for r-Process nucleosynthesis of newly measured β-decay half-lives, masses, and spectroscopy of neutron-rich nuclei near the r-Process Path. We overview r-Process nucleosynthesis in the neutrino driven wind above the proto-neutron star in core collapse supernovae along with the possibility of magneto-hydrodynamic jets from rotating supernova explosion models. We also consider the possibility of neutron star mergers as an r-Process environment. A key outcome of newly measured nuclear properties far from stability is the degree of shell quenching for neutron rich isotopes near the closed neutron shells. This leads to important constraints on the sites for r-Process nucleosynthesis in which freezeout occurs on a rapid timescale.
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impact of new data for neutron rich heavy nuclei on theoretical models for r Process nucleosynthesis
arXiv: Nuclear Theory, 2016Co-Authors: Toshitaka Kajino, G J MathewsAbstract:Current models for the $r$ Process are summarized with an emphasis on the key constraints from both nuclear physics measurements and astronomical observations. In particular, we analyze the importance of nuclear physics input such as beta-decay rates; nuclear masses; neutron-capture cross sections; beta-delayed neutron emission; probability of spontaneous fission, beta- and neutron-induced fission, fission fragment mass distributions; neutrino-induced reaction cross sections, etc. We highlight the effects on models for $r$-Process nucleosynthesis of newly measured $\beta$-decay half-lives, masses, and spectroscopy of neutron-rich nuclei near the $r$-Process Path. We overview r-Process nucleosynthesis in the neutrino driven wind above the proto-neutron star in core collapse supernovae along with the possibility of magneto-hydrodynamic jets from rotating supernova explosion models. We also consider the possibility of neutron star mergers as an r-Process environment. A key outcome of newly measured nuclear properties far from stability is the degree of shell quenching for neutron rich isotopes near the closed neutron shells. This leads to important constraints on the sites for $r$-Process nucleosynthesis in which freezeout occurs on a rapid timescale.
Y. Miyashita - One of the best experts on this subject based on the ideXlab platform.
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Search for spin-orbit-force reduction at 106,108Zr around r-Process Path
2012Co-Authors: T. Sumikama, K. Yoshinaga, Hiroshi Watanabe, Shunji Nishimura, Y. Miyashita, K. Yamaguchi, K. Sugimoto, J. Chiba, Z. H. Li, H. BabaAbstract:Shell gap at the magic number N = 82 is important to reproduce the 2nd peak of r-Process abundance. If a spin-orbit force is reduced in a very neutron-rich region, a shell quenching at N = 82 and a new shell closure at N = 70 are predicted. A shell evolution by the spin-orbit-force reduction can be searched for through the shape evolution of Zr isotopes around an expected double magic nuclei, 110Zr(Z = 40,N = 70). We performed β-γ and isomer spectroscopy at RIBF to observe low-lying states in 106,108Zr. The present results indicate a well deformed shape for 106,108Zr. The drastic reduction of the spin-orbit force most likely does not occur around 110Zr on an r-Process Path.
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β decay half lives of very neutron rich kr to tc isotopes on the boundary of the r Process Path an indication of fast r matter flow
Physical Review Letters, 2011Co-Authors: S Nishimura, T. Sumikama, K. Yoshinaga, Y. Miyashita, K. Yamaguchi, H Watanabe, T Tachibana, M Kuratanishimura, G Lorusso, A OdaharaAbstract:The β-decay half-lives of 38 neutron-rich isotopes from (36)Kr to (43)Tc have been measured; the half-lives of (100)Kr, (103-105)Sr, (106-108)Y, (108-110)Zr, (111,112)Nb, (112-115)Mo, and (116,117)Tc are reported here. The results when compared with previous standard models indicate an overestimation in the predicted half-lives by a factor of 2 or more in the A≈110 region. A revised model based on the second generation gross theory of β decay better predicts the measured half-lives and suggests a more rapid flow of the rapid neutron-capture Process (r-matter flow) through this region than previously predicted.
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β decay half lives of very neutron rich kr to tc isotopes on the boundary of the r Process Path an indication of fast r matter flow
Physical Review Letters, 2011Co-Authors: S Nishimura, T. Sumikama, K. Yoshinaga, K. Yamaguchi, Z. H. Li, H Watanabe, T Tachibana, M Kuratanishimura, G Lorusso, Y. MiyashitaAbstract:The {beta}-decay half-lives of 38 neutron-rich isotopes from {sub 36}Kr to {sub 43}Tc have been measured; the half-lives of {sup 100}Kr, {sup 103-105}Sr, {sup 106-108}Y, {sup 108-110}Zr, {sup 111,112}Nb, {sup 112-115}Mo, and {sup 116,117}Tc are reported here. The results when compared with previous standard models indicate an overestimation in the predicted half-lives by a factor of 2 or more in the A{approx_equal}110 region. A revised model based on the second generation gross theory of {beta} decay better predicts the measured half-lives and suggests a more rapid flow of the rapid neutron-capture Process (r-matter flow) through this region than previously predicted.