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Measurement of the isomer production ratio for the $$^{112}$$Cd($$n,gamma$$)$$^{113}$$Cd reaction using neutron beams at J-PARC

J-PARCの中性子ビームを用いた$$^{112}$$Cd($$n,gamma$$)$$^{113}$$Cd反応におけるアイソマー生成比の測定

早川 岳人*; 藤 暢輔; Huang, M.; 静間 俊行*; 木村 敦; 中村 詔司; 原田 秀郎 ; 岩本 信之; 千葉 敏*; 梶野 敏貴*

Hayakawa, Takehito*; Toh, Yosuke; Huang, M.; Shizuma, Toshiyuki*; Kimura, Atsushi; Nakamura, Shoji; Harada, Hideo; Iwamoto, Nobuyuki; Chiba, Satoshi*; Kajino, Toshitaka*

The astrophysical origin of a rare isotope $$^{115}$$Sn has remained still an open question. An isomer ($$T_{1/2}$$=14.1 y) in $$^{113}$$Cd is an s-process branching point from which a nucleosynthesis flow reaches to $$^{115}$$Sn. The $$s$$-process abundance of $$^{115}$$Sn depends on the isomer production ratio in the $$^{112}$$Cd($$n,gamma$$)$$^{113}$$Cd reaction. However, the ratio has not been measured in an energy region higher than the thermal energy. We have measured $$gamma$$ rays following neutron capture reactions on $$^{112}$$Cd using two cluster HPGe detectors in conjunction with a time-of-flight method at J-PARC. We have obtained the result that the relative $$gamma$$-ray intensity ratio of the isomer is almost constant in an energy region of up to 5 keV. This result suggests that the $$s$$-process contribution to the solar abundance of $$^{115}$$Sn is negligibly small. We have found that the ratio of a resonance at 737 eV shows about 1.5 times higher than other ratios. This enhancement can be explained by a $$p$$-wave neutron capture. This result suggests measurements of decay $$gamma$$ rays to isomers are effective to assign the spin and parity for neutron capture resonances.

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