Storage-ring mass spectrometry was applied to neutron-rich 197Au
projectile fragments. Masses of 181,183Lu, 185,186Hf, 187,188Ta,
191W, and 192,193Re nuclei were measured for the first time. The
uncertainty of previously known masses of 189,190W and 195Os nuclei
was improved. Observed irregularities on the smooth two-neutron separation
energies for Hf and W isotopes are linked to the collectivity phenomena in the
corresponding nuclei.Comment: 10 pages, 9 figures, 2 table