Spectroscopy and single-particle structure of the odd-Z heavy elements 255Lr, 251Md and 247Es

The odd-Z isotope Lr and its daughter Md and grand-daughter Es were studied in two experiments performed at GANIL and the University of Jyväskylä. The Lr nuclei were produced using the cold fusion-evaporation reaction Bi(Ca,2n)Lr at a bombarding energy of 217 MeV. The singleparticle structure and decay properties were investigated using α, γ and electron spectroscopy. The groundstate spin and parity could be assigned for Lr (1/2−) and Md (7/2−). States corresponding to the 7/2[633], 7/2−[514] and 1/2−[521] Nilsson orbitals were observed. Results are compared to experimental data obtained in neighbouring isotopes and to Hartree-Fock-Bogoliubov calculations using the Skyrme interaction SLy4 and a density-dependent pairing interaction. The position of the 1/2−[521] orbital from the spherical 2f5/2 shell is discussed. 2 A. Chatillon, Ch. Theisen, P.T. Greenlees et al.: Spectroscopy and single-particle structure...