Cluster preformation at the nuclear surface in cold fission

Horia Hulubei National Institute of Physics and Nuclear Engineering (IFIN-HH) - P.O. Box MG-6, RO-077125 Bucharest-Magurele, Romania and Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe University - Ruth-Moufang-Str. 1, D-60438 Frankfurt am Main, Germany

Received: 28 January 2017
Accepted: 8 June 2017

Abstract

Microscopic theories of alpha decay and cluster radioactivity explain these decay modes as a quantum tunnelling of a preformed cluster at the nuclear surface. In the present work we show that in a spontaneous cold-fission process the shell plus pairing corrections, calculated with Strutinsky's procedure based on the two-center shell model, may give a strong argument for preformation of a light fission fragment near the nuclear surface. It is obtained when the radius of the light fragment, R₂, is increased linearly with the separation distance, R, of the two fragments, while for R₂ =  const one gets the well-known two-hump potential barrier for heavy and superheavy nuclei. Nuclear-physics community also contributed to nanocluster physics by applying the macroscopic-microscopic method to explain the shell effects experimentally observed since 1984. Applications are shown for two nuclei, ²⁶⁰Rf and ²⁶⁴Sg, whose half-life against spontaneous fission is very well known. We stress a new aspect of the cold spontaneous fission, unifying its theory with that of α- and cluster decays, all having in common a preformed light cluster which will penetrate the potential barrier by quantum tunelling.