The path and termination point for the rapid proton-capture (rp) process above ${}^{56}\mathrm{Ni}$ is uncertain due to a lack of knowledge of nuclear properties, especially masses, near the proton drip line. To address this need we have begun a program to measure masses along the rp-process path in the $A\sim 60–80$ region using β-γ coincidence spectroscopy. $Q_{\mathrm{EC}}$ values derived from ${\beta }^{+}$ spectrum end points were used to calculate mass excess values for ${}^{70}\mathrm{Se},$ ${}^{71}\mathrm{Se},$ ${}^{72}\mathrm{Br},$ and ${}^{73}\mathrm{Br}.$ The results are compared to predictions of mass models and to estimates based on systematic trends in this region.

• Received 14 September 2000

DOI:https://doi.org/10.1103/PhysRevC.63.034314