We study a new s-process path through an isomer of 186 Re to improve a 187 Re-187 Os nucleo-cosmochronometer. The nucleus 187 Re is produced by this new path of 185 Re(n,γ) 186 Re m (n,γ) 187 Re. We measure a ratio of neutron capture cross-sections for the 185 Re(n,γ) 186 Re m and 185 Re(n,γ) 186 Re gs reactions at thermal neutron energy because the ratio with the experimental uncertainty has not been reported. Using an activation method with reactor neutrons, we obtain the ratio of R th = 0.54 ± 0.11%. From this ratio we estimate the ratio of Maxwellian averaged cross sections in a typical s-process environment at kT = 30 keV with a help of the temperature dependence given in a statistical-model calculation because the energy dependence of the isomer/ground ratio is smaller than the absolute neutron capture cross-section. The ratio at kT =30 keV is estimated to be R st = 1.3 ± 0.8%. We calculate the s-process contribution from the new path in a steady-flow model. The additional abundance of 187 Re through this path is estimated to be N s = 0.56 ± 0.35% relative to the abundance of 186 Os. This additional increase of 187 Re does not make any remarkable change in the 187 Re-187 Os chronometer for an age estimate of a primitive meteorite, which has recently been found to be affected strongly by a single supernova r-process episode.

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Abstract. The M1 strengths (or level density of 1 + states) are of importance for estimation of interaction strengths between neutrinos and nuclei for the study of the supernova neutrino-process. In 1957, Agodi predicted theoretically angular distribution of neutrons emitted from states excited via dipole transitions with linearly polarized gamma-ray beam at the polar angle of =90 should be followed by a simple function, a + b cos(2 ), where is azimuthal angel. However, this theoretical prediction has not been verified over the wide mass region except for light nuclei as deuteron. We have measured neutron angular distributions with (polarized gamma, n) reactions on Au, NaI, and Cu. We have verified the Agodi's prediction for the first time over the wide mass region. This suggests that (polarized gamma, n) reactions may be useful tools to study M1 strengths in giant resonance regions.

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The 29 P(p, γ) 30 S reaction rate strongly affects explosive hydrogen burning in classical novae and type I X-ray bursts, and depends on the structure of proton unbound 30 S states. The rate in the temperature characteristic of nucleosynthesis in novae and X-ray bursts had been previously predicted to be dominated by two low-lying, unobserved, J π = 3 + and 2 + resonances above the proton threshold in 30 S. Since then, two states have been found at 4699(6) keV and 4814(3) keV, which were tentatively assigned to be the 3 + and 2 + states, respectively. To confirm the existence of these two levels and their energies, the structure of 30 S was investigated via an in-beam γ-ray spectroscopy experiment using the 28 Si( 3 He, nγ) 30 S reaction at University of Tsukuba Tandem Accelerator Complex in Japan. This work describes the experimental setup and presents the preliminary results.11th Symposium on Nuclei in the Cosmos