Fission fragment distributions and some comments on the limit to new elements

Peter Moller (Department of Mathematical Physics, Lund University, Sweden)

Since the discovery of fission in 1938-1939 many fission properties have been analyzed by calculating the nuclear potential energy as a function of the shape of the nucleus. To do this one needs to have a realistic model of the potential energy AND perform the study for a sufficient number of shapes. It is only in the past two decades available computer power has made it possible to include the necessary number of shape-degrees of freedoms which leads to potential energies for millions of different shapes. I will show how a simple “random walk” on these surfaces allows us to calculate fission-fragment distributions. Odd-even staggering is also modeled. During my visit here we have studied the variation of odd-even staggering with energy and fissioning systems and further developed the models to describe in more detail new GANIL observations such as local and global odd-even staggering and identify the mechanism leading to odd-even staggering in the odd-proton 239Np isotope.

By now we have sufficient evidence about the predictive reliability of our macroscopic-microscopic model that we with reasonable confidence can make estimates of the possibility of discovering new elements beyond Z=118. I will briefly discuss our view on these possibilities.