Experimental challenges for the Re/Os clock
Experimental challenges for the Re/Os clock
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DOI：
10.22323/1.028.0055
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发表时间：
2006-06
影响因子：
5.3
通讯作者：
Francisco Calviño Tavares;Guillem Pere Cortés Rossell;Agustí Poch Parés;Carme Pretel Sánchez
中科院分区：
文献类型：
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作者：
Francisco Calviño Tavares;Guillem Pere Cortés Rossell;Agustí Poch Parés;Carme Pretel Sánchez
186 Os和187 Os的恒星中子俘获截面对于Re/Os宇宙计时器来说是基础，因为它们决定了187 Os的s过程丰度。从太阳187 Os丰度中减去s-分量，得到187 Os的放射成因贡献，这是由于来自r-过程核合成的187 Re的B -衰变（t1=2 = 42.3戈伊）。187 Os的实验室截面需要对9.75 keV的低激发态的影响进行显著的校正，该激发态在恒星条件下具有很强的布居。这种理论校正的可靠性可以大大提高的非弹性散射的截面的实验测定的9.75 keV状态。在这项工作中，高分辨率的光时间测量（n;g）截面的186;187; 188 Os从1 eV到1 MeV的欧洲核子研究中心的n_TOF设施进行报告。推断的恒星横截面不同于以前的建议值。此外，在卡尔斯鲁厄3.7 MV货车德格拉夫的时间-光在30 keV的中子能量的非弹性散射截面已被测量。布里里讨论了这些结果对Re/Os钟的意义。
The stellar neutron capture cross sections of 186Os and 187Os are fundamental for the Re/Os cosmo-chronometer since they are de ning the s-process abundance of 187Os. Subtraction of the s-component from the solar 187Os abundance yields the radiogenic contribution to 187Os due to b -decays of 187Re (t1=2 = 42.3 Gy) originating from r-process nucleosynthesis. The laboratory cross section of 187Os requires a signi cant correction for the effect of the low-lying excited state at 9.75 keV, which is strongly populated under stellar conditions. This reliability of the theoretical correction can be greatly improved by an experimental determination of the cross section for inelastic scattering to the 9.75 keV state. In this work, high resolution time-of- ight measurements of (n;g ) cross sections of 186;187;188Os from 1 eV to 1 MeV performed at the CERN n_TOF facility are reported. The inferred stellar cross sections differ from previously recommended values. In addition, the inelastic scattering cross section has been measured at 30 keV neutron energy via time-of- ight at the Karlsruhe 3.7 MV Van de Graaff. The implications of these results for the Re/Os clock are brie y discussed.