Penning-trap mass spectrometry of highly charged, neutron-rich Rb and Sr isotopes in the vicinity of A ≈ 100

The neutron-rich mass region around A approximate to 100 presents challenges for modeling the astrophysical r process because of rapid shape transitions. We report on mass measurements using the TITAN Penning trap at TRIUMF-ISAC to attain more reliable theoretical predictions of r-process nucleosynthesis paths in this region. A new approach using highly charged (q = 15+) ions has been applied which considerably saves measurement time and preserves accuracy. New mass measurements of neutron-rich Rb-94,Rb-97,Rb-98 and Sr-94,Sr-97-99 have uncertainties of less than 4 keV and show deviations of up to 11 sigma when compared to previous measurements. An analysis using a parameterized r-process model is performed and shows that mass uncertainties for the A = 90 abundance region are eliminated.