NUCLEAR ASTROPHYSICS STUDIES WITH LASER INVERSE-COMPTON γ RAYS

在AIST（美国国家先进工业科学与技术研究所），由激光反康普顿散射产生的准单色y射线被用于光分解：1)II型超新星核合成的感兴趣be， 2) p过程核合成的^<181>Ta, 3)大爆炸核合成的D，以及4)s过程核合成的^<186>W。得到了以下结果：1)^9Be：测量了从阈值到6.1MeV能量范围内的光子中子截面。确定了^9Be中1/2^+、5/2^-、5/2^+态的电磁约简跃迁概率，并计算了αα(n,γ)^9Be的天体物理反应速率。^<181>Ta：在阈值到12MeV能量范围内测量光子中子截面。基于QRPAγ强度函数的Hauser-Feshbach模型计算，讨论了大质量恒星作为II型超新星爆发时富O/Ne层中^<180>Ta的p过程起源。3)D：测量了从阈值到4.6MeV能量范围内的光子中子截面。p(n,γ)D的反应速率在与大爆炸核合成相关的能量区有6%的不确定度，为理论反应速率提供了实验基础。4)^<186>W：在阈值到10.8MeV的能量范围内测量光子中子截面。用hauser - feshach统计模型计算了放射性^<185>W核（T_<1/2>=75天）在30keV下的中子捕获截面。给出了s过程模型允许的中子密度约束。

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.