Mass measurements of 70Se, 71Se, 72Br, and 73Br

The path and termination point for the rapid proton-capture (rp) process above Ni-56 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 similar to 60-80 region using beta-gamma coincidence spectroscopy, Q(EC) values derived from beta (+) spectrum end points were used to calculate mass excess values for Se-70, Se-71, Br-72, Br-73. The results are compared to predictions of mass models and to estimates based on systematic trends in this region.