Speaker
Description
The formation of heavy nuclei along the neutron-rich region of the chart of nuclides is usually explained using two main processes, namely the s- and r-processes. Recent astronomical observations have shown ``strange’’ abundance distributions in Carbon-Enhanced Metallic Poor (CEMP) stars, which cannot be explained by these two neutron-capture processes alone, hence giving rise to additional nucleosynthesis processes. One such process is the astrophysical intermediate (i-)process.
The site at which the i-process occurs is not yet identified as one of the reasons is the associated nuclear uncertainties. The i-process occurs from 2-8 mass units away from the valley of stability, and while the structure of these nuclei along this pathway is mostly known experimentally, the neutron-capture reaction rates are almost entirely provided by theory. In particular, recent sensitivity studies of neutron-capture reactions on Kr isotopes have been identified to strongly affect Rb/Sr abundances.
To better understand the i-process, CARIBU, located at ATLAS facility at Argonne National Laboratory, was utilised to constrain the neutron-capture of the $^{87,89}$Kr(n,$\gamma$)$^{88,90}$Kr reactions. The indirect method of $\beta$-decays from the $^{88,90}$Br nuclei into $^{88,90}$Kr was used to identify the resulting $\gamma$-rays using the SUmming NaI detector, SuN, and the SuNTAN moving tape system.
Nuclear level densities and $\gamma$-ray strength functions of $^{88,90}$Kr were extracted using the $\beta$-Oslo method, of which the preliminary results will be discussed in this presentation. By exploiting the statistical properties of both $^{88,90}$Kr, the $^{87,89}$Kr(n,$\gamma$)$^{88,90}$Kr reaction rates and cross sections will be constrained to help understand their impact on the astrophysical i-process and on the Rb/Sr production.
