We have performed the first direct measurement of the ${}^{83}\mathrm{Rb}(p,\gamma )$ radiative capture reaction cross section in inverse kinematics using a radioactive beam of ${}^{83}\mathrm{Rb}$ at incident energies of 2.4 and $2.7A\mathrm{MeV}$. The measured cross section at an effective relative kinetic energy of $E_{\mathrm{cm}}=2.393\mathrm{MeV}$, which lies within the relevant energy window for core collapse supernovae, is smaller than the prediction of statistical model calculations. This leads to the abundance of ${}^{84}\mathrm{Sr}$ produced in the astrophysical $p$ process being higher than previously calculated. Moreover, the discrepancy of the present data with theoretical predictions indicates that further experimental investigation of $p$-process reactions involving unstable projectiles is clearly warranted.

• Received 14 May 2021
• Revised 19 July 2021
• Accepted 11 August 2021

DOI:https://doi.org/10.1103/PhysRevLett.127.112701