Determination of the proton separation energy of Rh93 from mass measurements

The proposed vp process, which occurs in the early time proton-rich neutrino winds of core-collapse supernovae, has the potential to resolve the long-standing uncertainty in the production of the light p-nuclei Mo-92 and Mo-94. A recent study incorporating this vp process has indicated that the proton separation energy SP of Rh-93 is especially important in determining the relative production of these two isotopes. To reproduce the observed solar Mo-92/Mo-94 abundance ratio of 1.57 a S-p value for Rh-93 of 1.64 +/- 0.1 MeV is required. The previously unknown masses of Ru-92 and Rh-93 have been measured with the Canadian Penning Trap mass spectrometer resulting in an experimental value for S-p(Rh-93) of 2.007 +/- 0.009 MeV. This implies that with our current understanding of the conditions in core-collapse supernova explosions the vp process is not solely responsible for the observed solar Mo-92/(94) Mo abundance ratio.