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Center for Nonlinear Studies |
By super-heavy elements (SHEs) we mean elements with proton number (Z) near the next magic number beyond the magic number Z=82, corresponding to Pb. When I started my career around 1967 elements up to Z=105 had been observed. Predicting stability properties of as yet undiscovered elements was a main focus area of my thesis advisor at that time. Now observations of elements up to Z=118 have been claimed. Discoveries are often clustered around groups that develop new experimental techniques. For example the six elements with proton number from 107 to 112 were all discovered at GSI, Darmstadt in the years 1981 to 1996. Today there are many new exciting results from Dubna on still heavier elements up to about Z=118. I will discuss the experimental techniques that have been implemented to produce such heavy elements, how they are identified through their decay patterns and the theoretical models, many of them developed here at LANL, used to describe their properties. Sometimes overlooked is that SHEs are an excellent testing ground for nuclear-theory models. Nuclei with proton number 118 and total nucleon number A near 290 are about 40 nucleons away from systems to which models are normally adjusted, very limited data on level structure, nuclear masses and other properties are available above A=250, so testing models on properties such as fission half-lives and alpha-decay Q values near A=290 involves a jump of about 40 nucleons from known data. This is of similar magnitude as an excursion from the line of beta-stability to the r-process line. I will therefore compare models we currently use in studies of element synthesis in the r-process to SHE data and hope to show that it is possible to make predictions that have useful reliability far from known nuclei.
Host: Ivan Vitev, T-2: NUC & PARTICLE PHYS, ASTROPHYS & COSMOLOGY