Neutron reactions and nuclear cosmo-chronology

Mosconi, M.; Heil, M.; Käppeler, F.; Mengoni, A.; Plag, R.; Fujii, K.; Gallino, R.; Aerts, G.; Terlizzi, R.; Abbondanno, U.; Álvarez‐Pol, H.; Álvarez‐Velarde, F.; Andriamonje, S.; Andrzejewski, J.; Assimakopoulos, P.; Audouin, L.; Badurek, G.; Baumann, P.; Bečvář, F.; Berthoumieux, E.; Bisterzo, S.; Calviño, F.; Cano‐Ott, D.; Capote, R.; Albornoz, A. Carrillo de; Cennini, P.; Chepel, V.; Chiaveri, E.; Colonna, N.; Cortés, G.; Couture, A.; Cox, James W.; Dahlfors, M.; David, S.; Dillman, I.; Dolfini, R.; Domingo‐Pardo, C.; Dridi, W.; Durán, I.; Eleftheriadis, C.; Embid‐Segura, M.; Ferrant, L.; Ferrari, A.; Ferreira‐Marques, R.; Fitzpatrick, L.; Frais‐Köelbl, H.; Furman, W.; Gonçalves, I. F.; González‐Romero, E.; Goverdovski, A.; Gramegna, F.; Griesmayer, E.; Guerrero, C.; Gunsing, F.; Haas, Brian J.; Haight, R. C.; Herrera-Martı́nez, A.; Igashira, M.; Isaev, S.; Jericha, E.; Kadi, Y.; Karamanis, D.; Karadimos, D.; Kerveno, M.; Ketlerov, V.; Koehler, P.; Konovalov, V.; Kossionides, E.; Krtička, M.; Lamboudis, C.; Leeb, H.; Lindote, A.; Lopes, I.; Lozano, M.; Lukić, S.; Marganiec, J.; Marques, L.; Marrone, S.; Mastinu, P.; Milazzo, Paolo; Moreau, C.; Neves, F.; Oberhummer, H.; Oshima, M.; O’Brien, S.; Pancin, J.; Papachristodoulou, C.; Papadopoulos, C.; Paradela, C.; Patronis, N.; Pavlik, A.; Pavlopoulos, P.; Perrot, L.; Plompen, A.; Plukis, A.; Poch, A.; Pretel, C.; Quesada, J. M.; Rauscher, T.; Reifarth, R.; Rosetti, M.; Rubbia, C.; Rudolf, G.; Rullhusen, P.; Salgado, J.; Sarchiapone, L.; Savvidis, I.; Stéphan, C.; Tagliente, G.; Taín, J. L.; Tassan‐Got, L.; Tavora, L.; Vannini, G.; Vaz, P.; Ventura, Alessandro; Villamarı́n, D.; Vincente, M. C.; Vlachoudis, V.; Vlastou, R.; Voß, F.; Walter, S.; Wendler, H.; Wiescher, M.; Wisshak, K.

doi:10.1016/j.ppnp.2006.12.014

Cited by 7 publications

(4 citation statements)

References 19 publications

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“…However, a recent measurement of the 186 Os neutron-capture cross section by Mosconi et al (2010a) excludes this hypothesis. As noted by Reisberg et al (2009), the mismatch between the inferred 186 Os/ 188 Os s-process ratio, derived from isotopic anomalies observed in primitive meteorites (Brandon et al 2005;Yokoyama et al 2007), and model predictions could be resolved by using a recent measurement of the 188 Os neutron-capture cross section (Mosconi et al 2007), which is ∼27% lower than the recommended value of Bao et al (2000). Sonnabend et al (2003) suggested an increase of the 185 W neutron-capture cross section (by about 60%), which would lead to a decrease of 186 Os and an increase of the 186 W abundance.…”

Section: Discussionmentioning

confidence: 99%

TUNGSTEN ISOTOPIC COMPOSITIONS IN STARDUST SiC GRAINS FROM THE MURCHISON METEORITE: CONSTRAINTS ON THEs-PROCESS IN THE Hf-Ta-W-Re-Os REGION

Ávila

Lugaro

Ireland

et al. 2011

ApJ

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26We report the first tungsten isotopic measurements in stardust silicon carbide (SiC) grains 27 recovered from the Murchison carbonaceous chondrite. The isotopes 182,183,184,186 W and 179,180 Hf 28 were measured on both an aggregate (KJB fraction) and single stardust SiC grains (LS+LU 29 fraction) believed to have condensed in the outflows of low-mass carbon-rich asymptotic 30 giant branch (AGB) stars with close-to-solar metallicity. The SiC aggregate shows small 31 deviations from terrestrial (=solar) composition in the 182 W/ 184 W and 183 W/ 184 W ratios, with 32 deficits in 182 W and 183 W with respect to 184 W. The 186 W/ 184 W ratio, however, shows no 33 apparent deviation from the solar value. Tungsten isotopic measurements in single 34 mainstream stardust SiC grains revealed lower than solar 182 W/ 184 W, 183 W/ 184 W, and 186 W/ 184 W 35 ratios. We have compared the SiC data with theoretical predictions of the evolution of W 36 isotopic ratios in the envelopes of AGB stars. These ratios are affected by the slow neutron-37 capture process and match the SiC data regarding their 182 W/ 184 W, 183 W/ 184 W, and 179 Hf/ 180 Hf 38isotopic compositions, although a small adjustment in the s-process production of 183 W is 39 needed in order to have a better agreement between the SiC data and model predictions. The 40 models cannot explain the 186 W/ 184 W ratios observed in the SiC grains, even when the current 41 185 W neutron-capture cross section is increased by a factor of two. Further study is required to 42 better assess how model uncertainties (e.g., the formation of the 13 C neutron source, the mass-43 loss law, the modelling of the third dredge-up, and the efficiency of the 22 Ne neutron source) 44 may affect current s-process predictions. 45

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Section: Discussionmentioning

confidence: 99%

TUNGSTEN ISOTOPIC COMPOSITIONS IN STARDUST SiC GRAINS FROM THE MURCHISON METEORITE: CONSTRAINTS ON THEs-PROCESS IN THE Hf-Ta-W-Re-Os REGION

Ávila

Lugaro

Ireland

et al. 2011

ApJ

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“…http://kadonis.org 13 2 H (Nagai et al 2006), 9 Be (Wallner et al 2008), 14 C (Reifarth et al 2008), 17 O (Wagoner 1969), 19 F (Uberseder et al 2007), 21 Ne (Heil et al 2005), 23 Na (Heil et al 2007),24,25,26 Mg (Massimi et al 2012),28,29,30 Si(Guber et al 2003),35,37 Cl (Guber et al 2002), 40 Ca (Dillmann et al 2009), 45 Sc (Heil et al 2009), 54 Fe (Coquard et al 2006), 58 Fe, 59 Co, 64 Ni and 63,65 Cu (Heil et al 2008b), 60 Fe (Uberseder et al 2009), 58 Ni (Zugec et al 2014), 60 Ni (Corvi et al 2002), 62 Ni (Lederer et al 2014), 63 Ni (Lederer et al 2013), 74,76 Ge and 75 As (Marganiec et al 2009b), 78 Se (Dillmann et al 2006a), 79,81 Br and 85,87 Rb (Heil et al 2008a), 80,82,83,84,86 Kr (Mutti et al 2005), 90-96 Zr (Lugaro et al 2014), 102 Pd, 120 Te, and 130,132 Ba (Dillmann et al 2010), 116,120 Sn (Koehler et al 2001), 138 La (Dillmann 2006, priv. communication), 151,153 Sn (Best et al 2001), 174 Hf (Vockenhuber et al 2007), 168 Yb, 180 W, 184 Os, 190 Pt and 196 Hg (Marganiec et al 2010), 184,186 W (Marganiec et al 2009a), 185 W (Mohr et al 2004),186,187,188 Os(Mosconi et al 2007),90,192 Os(Marganiec 2008, priv. communication), 204 Pb (Domingo-Pardo et al 2007), 207 Pb (Domingo-Pardo et al 2006b), 209 Bi (Domingo-Pardo et al 2006a).J.…”

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confidence: 99%

The impact of (n,γ) reaction rate uncertainties of unstable isotopes nearN= 50 on the i-process nucleosynthesis in He-shell flash white dwarfs

Denissenkov

Perdikakis

Herwig

et al. 2018

J. Phys. G: Nucl. Part. Phys.

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The anomalous abundances of n-capture elements in the CEMP-r/s stars agree in many instances very well with simulation predictions of intermediate n-density nucleosynthesis, N n ∼ 10 13-10 15 cm −3 , in rapidly-accreting white dwarfs (RAWDs). We have performed Monte-Carlo simulations of this i-process nucleosynthesis in order to determine the impact of (n,γ) reaction rate uncertainties of 164 unstable isotopes, from 131 I to 189 Hf, on the prediction of abundances of 18 elements from Ba to W. The impact study is based on two representative one-zone models with constant values of N n = 3.16 × 10 14 cm −3 and N n = 3.16 × 10 13 cm −3 and on a multi-zone simulation based on a realistic stellar evolution model of He-shell convection entraining H in a RAWD model with [Fe/H] = −2.6. For each of the selected elements, we have identified up to two (n,γ) reactions having the strongest correlations between their rate variations constrained by Hauser-Feshbach computations and the predicted abundances, with the Pearson product-moment correlation coefficients |r P | > 0.15. We find that the possible discrepancies between the predicted and observed abundances of Ba and Pr in the CEMP-r/s star CS31062-050 could be significantly diminished if the rate of the reaction 137 Cs(n,γ) 138 Cs were reduced and the rates of 141 Ba(n,γ) 142 Ba or 141 La(n,γ) 142 La increased. We show that uncertainties of temperature-dependent β-decay rates of the same unstable isotopes have a negligible effect on the predicted abundances and that one-zone Monte-Carlo simulations can be used instead of computationally time-consuming multi-zone Monte-Carlo simulations in reaction rate uncertainty studies if they use comparable values of N n .

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“…The shape of the elastic TOF distribution has been obtained by a detailed GEANT simulation and was validated by the pure elastic yield from an 188 Os sample, while that of the inelastic component was obtained relative to the elastic part by the energy shift corresponding to the excitation energy of the scattering state at 9.75 keV. This analysis replaces a preliminary fit [17] and confirms the alternative approach reported in [16,29]. The separation of the two components in the TOF spectrum of 187 Os is shown in figure 2 for one of the detectors.…”

Section: Inelastic Scattering Cross Sectionmentioning

confidence: 99%

“…Moreover, experimental information below 1 keV is rather incomplete [13], leading to large uncertainties in the calculation of Maxwellian-averaged cross sections (MACS) at the low thermal energies. Experimental setup and techniques used for the (n, γ ) cross section measurements on 186,187,188 Os at the n TOF spallation facility [14] are described in [15][16][17]. In the following, we will focus on the relevant aspects of the final analysis.…”

Section: Radiative Neutron Capture Cross Sectionsmentioning

confidence: 99%

Nuclear physics for the Re/Os clock

Mosconi¹,

Heil

Käppeler³

et al. 2007

J. Phys. G: Nucl. Part. Phys.

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Dating the age of the universe by the β-decay of 187 Re (t 1/2 = 41.2 Gyr) requires the accurate assessment of the s-process reaction flow. The daughter nucleus 187 Os as well as its immediate s-only neighbor 186 Os are shielded from the r-process. Therefore, the radiogenic contribution to 187 Os can be derived via the local approximation of the s-process, which is well justified in this mass region: (σ N s) 187 = (σ N s) 186. Accordingly, accurate Maxwellianaveraged (n, γ) cross sections have to be known for 186 Os and 187 Os over the full range of s-process temperatures. Because 187 Os has low-lying excited states, which are significantly populated during the s-process, neutron captures on these excited states have to be properly taken into account. The input for the corresponding Hauser-Feshbach calculations can be constrained by deriving the strength functions from a detailed resonance analysis of the measured (n, γ) cross sections as well as by an additional measurement of the inelastic scattering cross section for the first exited level, which dominates the competition between the capture and scattering channels. This contribution reports on measurements of the neutron capture cross sections of 186 Os, 187 Os and 188 Os from the eV region to 1 MeV at the CERN/n TOF facility and of the inelastic scattering cross section of 187 Os around 30 keV at the Karlsruhe 3.7 MV Van de Graaff accelerator. Based on these results and on a detailed resonance analysis, improved Maxwellian-averaged cross sections were obtained for thermal energies between 5 keV and 100 keV. The implications of these results for the Re/Os clock are discussed.

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Neutron reactions and nuclear cosmo-chronology

Cited by 7 publications

References 19 publications

TUNGSTEN ISOTOPIC COMPOSITIONS IN STARDUST SiC GRAINS FROM THE MURCHISON METEORITE: CONSTRAINTS ON THEs-PROCESS IN THE Hf-Ta-W-Re-Os REGION

TUNGSTEN ISOTOPIC COMPOSITIONS IN STARDUST SiC GRAINS FROM THE MURCHISON METEORITE: CONSTRAINTS ON THEs-PROCESS IN THE Hf-Ta-W-Re-Os REGION

The impact of (n,γ) reaction rate uncertainties of unstable isotopes nearN= 50 on the i-process nucleosynthesis in He-shell flash white dwarfs

Nuclear physics for the Re/Os clock

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