Nuclear structure and formation mechanism of heavy shell-stabilized nuclei

In a series of experiments, 48Ca induced cold fusion reactions on Pb targets were employed to populate states in 253,254No isotopes. The ground-state band of 254No is identified up to spin 20+. The deduced quadrupole deformation is β = 0.27(2). Evidence for decays from a rotational band built on a 7/2[624] configuration was obtained in 253No. The initial angular momentum and excitation energy of 253,254No residues, after neutron emission, was determined. States up to spin 22 ℎ and excitation energy of E* = 8.5 MeV were observed. The data provide direct information on the fission barrier at high spins Bf≥ 5 MeV, and on the shell-correction energy Eshell expshell ≥ 4.1 MeV. (author)