Abstract
Fission phenomena are surveyed where fragment properties are catching the eye. Beyond the Liquid Drop the relevant properties of fragments are shell effects and nuclear pairing. Shell effects influence on mass, charge, stability and deformability of fragments. Most often only the stabilizing effects of shells are discussed and the equally frequent destabilizing effects are not mentioned. For the present purpose the terms shells and anti-shells are used in case of stabilizing and destabilizing effects, respectively. Fragment shells and anti-shells lead to fission modes with characteristic properties. A special issue is where in the course of fission these modes assume their characteristic features. Surprisingly fragment angular distributions in above- and sub-barrier fission help elucidating this question. The discussion is focussed on fission in the standard actinides.
Highlights
Fission phenomena are surveyed where fragment properties are catching the eye
The Liquid Drop Model (LDM) of nuclei has since the discovery of fission been the backbone of our understanding of the fission process
2 Scission Point Model In Scission Point Models (SPM) the properties and the decay of excited fragments are discussed while the fragments are in a configuration of two separate fragments aligned on a common fission axis
Summary
In Scission Point Models (SPM) the properties and the decay of excited fragments are discussed while the fragments are in a configuration of two separate fragments aligned on a common fission axis. The difference between the energy set free at scission Q and the energy bound as potential energy V = VCoul + VDef is available to feed the pre-scission kinetic energy EKpre and the intrinsic excitation energy Eint* the fragments already have at scission. These two limits are addressed as cold compact (1) and cold deformed (2) fission because in particular in both cases the fragments are not excited intrinsically. In fission this quasi-static equilibrium is identified with the average scission configuration. This result is remarkable since it tells that, compared to its companion fragment, a fragment with large stiffness α carries a small deformation energy V and is weakly deformed, in contrast to the companion fragment with larger deformation energy and larger deformation
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