MASS MEASUREMENT OF NEUTRON-RICH ISOTOPES FROM CA-51 TO NI-72

The ground state masses of thirty-nine neutron-rich nuclei from 51Ca t o 72Ni have been measured using the Time-of-Flight Isochronous (TOFI) spectrometer. Eight of these masses have been measured for the first t ime and thirty-one are remeasurements of neutron-rich nuclei previousl y reported. Good agreement between these results and a previous TOFI e xperiment was observed except for the most neutron-rich isotopes of va nadium through iron with the present results being more bound and in b etter agreement with theory. The low binding energy of 68Ni, as indica ted by an unreasonably low two-neutron separation energy, suggests the presence of a high-lying, long-lived isomeric state in this nucleus.