Speaker
Description
There are 35 proton-rich stable isotopes, known as p-nuclei. Their existence is attributed to the p-process, primarily consisting of a network of photodisintegration reactions on s- and r-process seed nuclei. The abundances of p-nuclei can be obtained based on simulations of this network, with most of the isotopes involved being radioactive. For this reason, direct measurements of these reactions are challenging, thus reaction rates are often obtained via theoretical calculations based on the Hauser-Feshbach (HF) theory. The Nuclear Level Density (NLD), gamma-ray strength function (gSF) of the compound nucleus is given as inputs to the theory as well as the Optical Model Potential (OMP) to obtain a theoretical cross section. Constraining theoretical models is crucial to obtain experimentally constrained cross-section values for unstable elements. In the present work, we focus on reactions around $^{85}\mathrm{Rb}$, relevant to the astrophysical p process, where reaction flow is defined by the competition between two reactions, the (γ, n) and the (γ, p). Depending on which is the dominant channel, that affects the production of the $^{78}\mathrm{Kr}$ p nucleus. Therefore, constraining the reaction rates for both channels is crucial to obtaining more accurate abundances for $^{78}\mathrm{Kr}$. Here we use the $^{84}\mathrm{Kr}(p,\gamma)^{85}\mathrm{Rb}$ reaction to populate the $^{85}\mathrm{Rb}$ compound nucleus, and constrain the NLD, gSF.
The $^{84}\mathrm{Kr}(p,\gamma)^{85}\mathrm{Rb}$ proton capture reaction was measured with the SuN detector at NSCL at MSU. A stable $^{84}\mathrm{Kr}$ beam was impinged onto a hydrogen gas target in the energy range of 2.7 MeV/u to 3.7 MeV/u. We present a re-analysis of the proton capture data in which we provide new values for the reaction cross section, and in addition, we use the γ-ray spectra to constrain the statistical properties of $^{85}\mathrm{Rb}$, namely the NLD and the gSF. In addition, the proton optical model potential (pOMP) parameters were modified to obtain a better fit on the experimental data of $^{84}\mathrm{Kr}(p,\gamma)^{85}\mathrm{Rb}$, $^{84}\mathrm{Kr}(p,n)^{84}\mathrm{Rb}$ and $^{84}\mathrm{Kr}(p,2n)^{83}\mathrm{Rb}$ reaction channels. The constrained NLD and gSF, as well as the modified pOMP, were used to calculate the astrophysical reaction rates for the $^{85}\mathrm{Rb}(\gamma,p)^{84}\mathrm{Kr}$ and $^{85}\mathrm{Rb}(\gamma,n)^{84}\mathrm{Rb}$ channels.