In-flight proton breakup of ${}^{73}$Rb

Properties of nuclei beyond the proton drip-line are important for mass models, astrophysics, and nuclear structure. Weakly-bound or proton-unbound nuclei near the rp process waiting-points, in particular, play a critical role in constraining calculations and observations of type I x-ray bursts. The relatively slow $\beta$-decay of ${}^{72}$Kr, for instance, may be bypassed significantly by 2p-capture reactions through ${}^{73}$Rb. This process, however, depends sensitively on the ${}^{73}$Rb proton separation energy, $S_{\textrm{p}}$. While recent measurements of ${}^{65}$As and ${}^{69}$Br have reduced uncertainties in the reaction sequence, the ${}^{72}$Kr waiting point still remains largely unconstrained. We have performed an experiment at NSCL to measure, using invariant-mass spectroscopy, the decay of ${}^{73}$Rb$\rightarrow$p+${}^{72}$Kr in an attempt to determine $S_{\textrm{p}}({}^{73}\textrm{Rb})$. Preliminary results from our recent ${}^{73}$Rb decay experiment will be presented.