We have measured the cross section of the $^{ 83}$Rb(p,$\gamma)^{ 84}$Sr radiative capture reaction in inverse kinematics using a radioactive beam of $^{ 83}$Rb at incident energies of 2.4 and $2.7 A$ MeV. Prior to the radioactive beam measurement, the $^{ 84}$Kr(p,$\gamma)^{ 85}$Rb radiative capture reaction was measured in inverse kinematics using a stable beam of $^{ 84}$Kr at an incident energy of $2.7 A$ MeV. The effective relative kinetic energies of these measurements lie within the relevant energy window for the $\gamma$ process in supernovae. The central values of the measured partial cross sections of both reactions were found to be $0.17-0.42$ times the predictions of statistical model calculations. Assuming the predicted cross section at other energies is reduced by the same factor leads to a slightly higher calculated abundance of the $p$ nucleus $^{ 84}$Sr, caused by the reduced rate of the $^{ 84}$Sr($\gamma$,p)$^{ 83}$Rb reaction derived from the present measurement.
Categories: nucl-ex astro-ph.SR