Masses of Proton-Rich Nuclides from Nb to Rh and their Influence on the $rp$- and $\nu p$-processes

The reaction paths of two astrophysical processes on the proton-rich side of stability, the $rp$ and $\nu p$~processes, pass through isotopes of Mo, Tc, Ru and Rh whose masses have only recently been measured. These measurements provide the more precise proton-separation energies,$S_p$, needed to model the paths and final abundances of these two processes. These $S_p$ have been of particular interest to the $\nu p$ process as it is a process which could potentially resolve the long-standing underproduction of light $p$-nuclei such as $^{92}$Mo and $^{94}$Mo. Accordingly, mass measurements of 18 proton-rich nuclides of elements from Nb to Rh have been performed with the Canadian Penning trap mass spectrometer, reducing uncertainties in the associated $S_{p}$ values by up to factors of 60 compared to the 2003 Atomic Mass Evaluation. $^{87}$Mo is found to disagree with the evaluated mass by 3.7$\sigma$, which affects recent $\nu p$-process abundance calculations. This work has been supported by grants from NSERC, Canada and by the U.S. DOE (DE-AC02-06CH11357 and DE-FG02-91ER-40609).