Nuclear stucture studies of transfermium nuclei

Abstract

The study of deformed nuclei in the region of 254No provides an indirect method to access the single-particle orbitals which are of relevance in determining the location of the next closed proton and neutron closed shells above 208Pb. Several of these orbitals are strongly down-sloping and are close to the Fermi surface in the deformed region. These nuclei are some of the heaviest for which detailed spectroscopy can be performed. Initial in-beam measurements in the region focussed on γ-ray spectroscopy of even-even nuclei (e.g. 252,254No, 250Fm), while more recently attention has switched to odd-mass nuclei such as 253No, 251Md and 255Lr, the latter being the heaviest nucleus so far studied in-beam. Non-yrast and isomeric states have recently been observed in 252,254No and 250Fm through the use of both in-beam and focal plane decay spectroscopy. Such experiments have yielded data which can be used to determine the excitation energies and configurations of two-quasiparticle states in the region, providing a stringent test for current nuclear structure models. An overview of the most recent results and the experimental techniques used is presented. Perspectives for the development of new devices for further studies in this region are also discussed.