Towards the Structure of the Heaviest Nuclei

Abstract

The understanding of the structure of the heaviest, in particular superheavy elements (SHE), is essential for the development of mean field theories that are used to predict nuclear properties far from stability. Experimental insight into the structure of superheavy spherical nuclei can be obtained by direct measurement of the ground state properties of nuclei. Attempts to reach the spherical SHE have been made in recent years, with firm evidence for Z=112 [1] and candidates for alpha decay from several nuclei with Z=114 – 116 have been reported [2]. Equally important information can come from the study of mid-shell deformed nuclei, since selected single particle orbitals that lie close to the spherical shell gap in SHE are close to the Fermi level in nuclei having large quadrupole deformation. Such information can come from alpha-decay studies or from in-beam spectroscopy. In the latter technique the prompt decay process is tagged by detection of the recoiling nucleus or by alpha decay from the recoil, using electromagnetic separators. In this manner, in-beam gamma-ray spectroscopy has enabled the rotational behaviour of the even-even nuclei 252,254No to be studied up to spin 20ħ. In these experiments the reaction products, although populated with small cross sections ( σ < 3µbarn), have been separated from the dominant fission background.