Neutron capture cross section and capture -ray spectrum of Sr in the stellar nucleosynthesis energy region

恒星での元素合成に関わるエネルギー領域におけるSrの中性子捕獲断面積及び捕獲線スペクトル

片渕 竜也*; 井頭 政之*; 鎌田 創*; 田近 道英*; 岩本 信之  ; 河野 俊彦*

Katabuchi, Tatsuya*; Igashira, Masayuki*; Kamada, So*; Tajika, Michihide*; Iwamoto, Nobuyuki; Kawano, Toshihiko*

The neutron capture cross section and the capture -ray spectrum of Sr were measured in the keV energy regions. Above 34 keV, the present data are larger than evaluated cross sections which are based on a set of resonance parameters measured in past experiments. To investigate the impact of the present results to the stellar nucleosynthesis, the Maxwellian averaged neutron capture cross section (MACS) was calculated using the present experimental results. The calculated MACS was about 10% smaller than the values widely used in stellar nucleosynthesis calculations and it is found that this difference arises from a problem in calculating the direct capture process in the previous study. In fact, the present and previous MACS become in good agreement when the contribution from the direct neutron capture process that has been theoretically calculated is removed from the previous MACS. This indicates that the previous work overestimated the contribution of the direct capture process. The present experimental capture -ray spectrum shows that primary transition intensities to the low-lying states of Sr drastically changes with the neutron energy.