Masses new and old: Measurements of 39 isotopes from (sup 51)Ca to (sup 72)Ni

摘要

The most recent mass measurements using the Time-of-Flight Isochronous (TOFI) spectrometer are presented. The masses of 8 neutron-rich nuclei are reported for the first time. Good agreement between these results and a previous TOFI experiment is observed except for the most neutron-rich isotopes of vanadium through iron where the present results are more bound and in better agreement with theory. An unreasonably low two-neutron separation energy for (sup 68)Ni suggests the presence of a high-lying, long-lived isomeric state in this nucleus. These results are contrasted with the latest shell model calculations and a variety of mass model predictions. In general good agreement is found, however, an enhanced binding-energy region centered around (sup 51)Ca and (sup 52-54)Sc persists. The neutron-excess dependence of neutron and proton pairing energies in the f(sub 7/2) shell are found to be considerably weaker than those obtained in a global fit.