Direct mass measurements of light neutron-rich nuclei using fast recoil spectrometers

Abstract

Extensive new mass measurement capabilities have evolved with the development of recoil spectrometers. In the Z=3–9 neutron‐rich region alone, 12 direct mass measurements have been determined for the first time by the fast–recoil direct mass measurement method. A recent experiment using the TOFI spectrometer illustrates this technique. A systematic investigation of nuclei that lie along or near the neutron‐drip line has provided a valuable first glimpse into the nuclear structure of such nuclei. No evidence for a large single‐particle energy gap at N=14 is observed; however, a change in the two‐neutron separation energy trend is found at N=15. This change is correctly predicted by shell model calculations, and is interpreted in terms of the smaller 1s1/2–1s1/2 interaction compared to that of the Od5/2–Od5/2 neutron–neutron interaction.