Volume 33, Issue 1
July 1989, pages 1-253
pp 1- July 1989
pp 1-12 July 1989
The story of the discovery of nuclear fission, one of the most exciting stories of how a scientific puzzle was finally solved and how the scientists involved were blind to many obvious indications, is described.
pp 13-20 July 1989
This article gives an overview of the physics of the fission phenomenon. It provides a brief introduction to the various aspects of the fission process such as liquid drop model fission barriers, different stages of the fission process, fragment kinetic energy and mass distributions, nuclear shell effects on fission barriers, fragment angular distributions and rare fission modes.
pp 21-32 July 1989
Some new aspects in the theory of heavy nuclei emerging from studies of nuclear shell structure in the nuclear-fission process are described. Specific subjects cover general understanding of shell structure, the significance of macroscopic modes and the droplet model.
pp 33-84 July 1989
Fission theory first developed within the framework of the liquid drop model. Shell model concepts were introduced into fission theory much later than they were in nuclear structure theory, but then with spectacular success in explaining striking experimental results then emerging in actinide fission. In the last two decades the complex topography of the fission barrier that is the result of shell model theory has been a major theme in the expanding knowledge of fission, most experimental data finding a natural explanation within this theme. The development of the concept of shell model structure in the fission barrier is outlined in this review.
pp 85-107 July 1989
The emission of light charged particles in the fission process is of interest as they are believed to emerge from the neck region of the deformed fissioning nucleus at a time close to the scission point and may thus prove a useful probe to investigate the last stages of fission close to the rupture point. Experimental results on light charged particle emission and the efforts made to obtain information about the scission point parameters therefrom are reviewed.
pp 109-131 July 1989
This article summarizes the recent radiochemical investigations on mass, charge kinetic energy and fragment angular distributions in low energy fission of actinides.
pp 133-144 July 1989
Mass asymmetry relaxation as manifested in fission and heavy ion-induced binary reactions is reviewed. In fission, the dynamics is characteristic of a fully damped case and is well described by a stochastic theory. In heavy ion deep inelastic collisions and quasi-fission, on the other hand, the relaxation is incomplete giving rise to the possibility of studying its time evolution.
pp 145-159 July 1989
This article reviews the work relating to the development of a rotating liquid drop model together with a chronology of its confrontation with the experimental interpretation of data. It is brought out that the zero temperature rotating finite range model is quite successful in the interpretation of data obtained from heavy ion-induced reactions.
pp 161-174 July 1989
Fragment angular distributions in fission is one of the oldest and well understood aspects of fission theory. However, recent heavy ion-induced fission and fission-like reactions have added a new dimension to this problem. We review here our present understanding of the fragment angular distribution theory in fission and fission-like reactions.
pp 175-208 July 1989
An introduction is given to the physics of the equilibrium transition-state model and of dissipative nuclear dynamics. Experimental data on pre-scission particle and gamma-ray emission and their interpretation are reviewed. They appear to indicate overdamped motion of the nuclear fluid. A time scale for compound-nucleus fission of about 30 × 10−21 s or greater is indicated, whilst that for quasi- or fast-fission is somewhat shorter.
pp 209-253 July 1989
The dualistic view of fission and evaporation as two distinct compound nucleus processes is substituted with a unified view in which fission, complex fragment emission and light particle evaporation are seen as part of a single process. The underlying connection between these decay modes is the mass asymmetry coordinate and the ridge line as the locus of the associated conditional barriers. The theoretical generalization is carried out explicitly. Complex fragment production at all mass asymmetries, throughout the periodic table, from low to intermediate bombarding energies is discussed in the light of compound nucleus decay.
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