Ground-State Proton Decay of 69Br and Implications for the 68Se Astrophysical Rapid Proton-Capture Process Waiting Point

We report on the first direct measurement of the proton separation energy for the proton-unbound nucleus Br-69. Bypassing the Se-68 waiting point in the rp process is directly related to the 2p-capture rate through Br-69, which depends exponentially on the proton separation energy. We find a proton separation energy for Br-69 of S-p(Br-69) = -785(-40)(+34) keV; this is less bound compared to previous predictions which have relied on uncertain theoretical calculations. The influence of the extracted proton separation energy on the rp process occurring in type I x-ray bursts is examined within the context of a one-zone burst model.