Time-of-flight mass measurements of exotic nuclei

Atomic masses play an important role in nuclear physics and astrophysics. The need of experimental mass values for unstable nuclides has triggered the development of a wide range of mass measurement techniques, with devices installed at many laboratories around the world. We have implemented a time-of-flight–magnetic-rigidity (TOF-Bρ)(TOF-Bρ) technique at the National Superconducting Cyclotron Laboratory (NSCL) that includes a position measurement for magnetic rigidity corrections and uses the A1900 separator and the S800 spectrograph. We performed a successful first experiment measuring masses of neutron-rich isotopes in the region of Z∼Z∼ 20–30, important for calculations of processes occurring in the crust of accreting neutron stars. The masses of 16 nuclei were determined, for 61V, 63Cr, 66Mn, and 74Ni for the first time, with atomic mass excesses of −30.510(890) MeV, −35.280(650) MeV, −36.900(790) MeV, and −49.210(990) MeV, respectively. The mass resolution achieved was 1.8×10−4.