Mass measurements of isotopes of Nb, Mo, Tc, Ru, and Rh along the nup- and rp-process paths using the Canadian Penning trap mass spectrometer

The reaction paths of two proposed nucleosynthetic processes on the proton-rich side of stability, the rp and nu p processes, pass through a region of isotopes between Mo and Pd where masses had long gone unmeasured. Precise knowledge of the paths and final abundances of these two processes has been limited by the corresponding lack of precision in the proton-separation energies S-p when derived from extrapolated masses. The masses of 18 neutron-deficient isotopes of Nb, Mo, Tc, Ru, and Rh have been measured using the Canadian Penning trap mass spectrometer. Three of the masses presented, Mo-90, Mo-91, and Tc-93, provide the first direct measurement of the masses of these nuclides, and the others provide confirmation of recent measurements using other Penning traps. Included in this work is a measurement of the mass of Mo-87, which differs by 3.7 sigma from the mass presented in the 2003 Atomic Mass Evaluation. This leads to a change in the S-p value of Tc-88 which reduces the suppression of flow of the nu p-process path through Mo-87(p, gamma)Tc-88 reported following the mass measurement of Tc-88 [C. Weber et al., Phys. Rev. C 78, 054310 (2008)]. This in turn affects the resulting nu p-process abundances.