Eur. Phys. J. A (2006) 30: 397-411
https://doi.org/10.1140/epja/i2006-10134-5

Nuclear Structure and Reactions

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

¹ CEA Saclay, DSM/DAPNIA/SPhN, F-91191, Gif-sur-Yvette Cedex, France
² Department of Physics, University of Jyväskylä, P.O. Box 35, FIN-40014, Finland
³ GANIL, Boulevard Henri Becquerel, B.P. 55027, F-14074, Caen Cedex 5, France
⁴ Oliver Lodge Laboratory, Department of Physics, University of Liverpool, L69 7ZE, Liverpool, UK
⁵ CEA Saclay, DSM/SPhT, F-91191, Gif-sur-Yvette Cedex, France
⁶ LPC, 6 boulevard du Maréchal Juin, F-14050, CAEN Cedex, France
⁷ CSNSM, Bat. 104-108, F-91405, Orsay, France
⁸ Service de Physique Nucléaire Théorique, Université Libre de Bruxelles, C.P. 229, B-1050, Bruxelles, Belgium
⁹ Joint Institute for Nuclear Research, 141980, Dubna, Russia

^* e-mail: christophe.theisen@cea.fr

Received: 20 July 2006
Accepted: 18 October 2006
Published online: 24 November 2006

Abstract

The odd-Z isotope ²⁵⁵Lr, its daughter ²⁵¹Md and grand-daughter ²⁴⁷Es were studied in two experiments performed at GANIL and the University of Jyväskylä. The ²⁵⁵Lr nuclei were produced using the cold fusion-evaporation reaction ²⁰⁹Bi(⁴⁸Ca, 2n)²⁵⁵Lr at a bombarding energy of 217MeV. The single-particle structure and decay properties were investigated using α, γ and electron spectroscopy. The ground-state spin and parity could be assigned for ²⁵⁵Lr (1/2^-) and ²⁵¹Md (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 2f _5/2 shell is discussed.