Measurement of the isomer production ratio for the Cd()Cd reaction using neutron beams at J-PARC

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 Sn has remained still an open question. An isomer (=14.1 y) in Cd is an s-process branching point from which a nucleosynthesis flow reaches to Sn. The -process abundance of Sn depends on the isomer production ratio in the Cd()Cd reaction. However, the ratio has not been measured in an energy region higher than the thermal energy. We have measured rays following neutron capture reactions on 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 -ray intensity ratio of the isomer is almost constant in an energy region of up to 5 keV. This result suggests that the -process contribution to the solar abundance of 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 -wave neutron capture. This result suggests measurements of decay rays to isomers are effective to assign the spin and parity for neutron capture resonances.