Constraining the Astrophysical P Process: Cross Section Measurement of the ⁸⁴Kr(p, γ)⁸⁵Rb Reaction in Inverse Kinematics

One of the biggest questions in nuclear astrophysics is understanding where the elements come from and how they are made. This work focuses on a nucleosynthesis process, namely the p process, which is a series of photodisintegration reactions responsible for producing the stable isotopes on the proton rich side of stability. These nuclei, known as the p nuclei, cannot be made through the well-known neutron-capture processes. Currently scientists rely heavily on theory to provide the relevant reaction rates in astrophysical p-process models to predict the final p-nuclei abundances and more experimental data is needed. The present work reports on an experiment performed with the Summing Sodium Iodide (NaI) (SuN) detector at the National Superconducting Cyclotron Facility (NSCL) at Michigan State University (MSU) using the ReAccelerator (ReA) facility to measure the ⁸⁴Kr(p, γ)⁸⁵Rb reaction cross section in inverse kinematics for the first time. This reaction is a branching point in the p-process reaction network important in the production of the p-nucleus, ⁷⁸Kr. A new hydrogen gas target was designed and fabricated and a new analysis technique for background subtraction and efficiency calculations of the detector were developed. The experimental cross section is compared to standard statistical model calculations using the NON-SMOKER and TALYS codes.