Neutron capture cross section and capture -ray spectrum of ⁸⁸Sr in the stellar nucleosynthesis energy region

The neutron capture cross section and the capture gamma -ray spectrum of 88Sr were measured in the keV energy regions: 10-89 keV and 510 keV. Between 34 and 89 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 were about 10% smaller than the values from a previous work [Koehler et al., Phys. Rev. C 62, 055803 (2000)]. On the other hand, 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 suggests that the previous work might overestimate the contribution of the direct capture process. The present experimental capture gamma -ray spectrum shows that primary transition intensities to the low-lying states of 89Sr drastically change with the neutron energy. The ratio between the ground and first excited state transitions was compared with estimation derived from the resonance parameters and theoretical prompt gamma -ray spectrum from the (lJ) neutron capture states. The estimation disagrees with the experimental values between 34 and 89 keV. This disagreement suggests that there are missed or (lJ)-misassigned resonances in the previous resonance analysis.