NUCLEAR ASTROPHYSICS STUDIES WITH LASER INVERSE-COMPTON γ RAYS

在美国国家高级工业科学技术研究所（AIST），激光逆康普顿散射产生的准单色γ射线被用来对1）用于II型超新星核合成的^9Be，2）<181>用于p-过程核合成的^ Ta，3）用于大爆炸核合成的D，以及4）<186>用于s-过程核合成的^ W进行光分解。1）在阈能至6.1MeV范围内测量了^9Be：光中子截面。测量了^9Be的12 ^+、5/2^-、5/2^+态的电磁约化跃迁几率，并计算了αα（n，γ）^9Be的天体物理反应率<181>。基于<180>Hauser-Feshbach模型计算，采用QRPAγ强度函数，讨论了大质量恒星II型超新星爆发时富O/Ne层中^ Ta的p过程起源。3）D：测量了阈能至4.6MeV的光中子截面。在与大爆炸核合成有关的能区，以6%的不确定度测定了p（n，γ）D的反应速率，为理论反应速率提供了实验基础。4）<186>测量了阈能至10.8MeV的光中子截面。用<185>Hauser-Feshbach统计模型计算了30 keV下T_（1/2）=75天的~ 1 W放射性核的中子俘获截面。给出了s过程模型中允许的中子密度约束条件。

Quasi-monochromatic y rays produced from laser inverse-Compton scattering at AIST(National Institute of Advanced Industrial Science and Technology) were used to photo-disintegrate 1)^9Be of interest for nucleosynthesis in type II supernovae, 2)^<181>Ta for the p-process nucleosynthesis, 3)D for big bang nucleosynthesis, and 4) ^<186>W for the s-process nucleosynthesis. The following results were obtained.1)^9Be : Photoneutron cross sections were measured at energies from threshold to 6.1MeV. Electromagnetic reduced transition probabilities were determined for the 1/2^+,5/2^-,5/2^+ states in ^9Be and the astrophysical reaction rate for αα(n,γ)^9Be were evaluated.2)^<181>Ta : Photoneutron cross sections were measured at energies from threshold to 12MeV. The p-process origin of ^<180>Ta in O/Ne rich layers during explosions of massive stars as type II supernovae was discussed based on the Hauser-Feshbach model calculation with the QRPAγ strength function.3)D : Photoneutron cross sections were measured at energies from threshold to 4.6MeV. The reaction rate for p(n,γ)D was determined with 6% uncertainty in the energy region relevant to big bang nucleosynthesis, providing an experimental foundation for theoretical reaction rates.4)^<186>W : Photoneutron cross sections were measured at energies from threshold to 10.8MeV. Neutron-capture cross sections for a radioactive ^<185>W nucleus(T_<1/2>=75 days) were evaluated at 30keV using the Hauser-Feshbach statistical model. Constraints on neutron density allowed in s-process models were provided.