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. Evidence for decays from a rotational band built on a 7/2[624] configuration was obtained in 253No. The ground-state band of 254No is identified up to spin 20+. The deduced quadrupole deformation is β=0.27(2). The initial angular momentum and excitation energy of 253,254No residues, after neutron emission, was determined. States up to spin 22(ℎ/2π) 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 Eshellexp≥4.1 MeV