Scission-point model of nuclear fission based on deformed-shell effects
A static model of nuclear fission is proposed based on the assumption of statistical equilibrium among collective degrees of freedom at the scission point. The relative probabilities of formation of complementary fission fragment pairs are determined from the relative potential energies of a system of two nearly touching, coaxial spheroids with quadrupole deformations. The total potential energy of the system at the scission point is calculated as the sum of liquid-drop and shell- and pairing-correction terms for each spheroid, and Coulomb and nuclear potential terms describing the interaction between them. The fissioning system at the scission point is characterized by three parameters: the distance between the tips of the spheroids (d), the intrinsic excitation energy of the fragments (tau/sub int/), and a collective temperature (T/sub coll/). No attempt is made to adjust these parameters to give optimum fits to experimental data, but rather, a single choice of values for d, tau/sub int/, and T/sub coll/ is used in the calculations for all fissioning systems. The general trends of the distributions of mass, nuclear charge, and kinetic energy in the fission of a wide range of nuclides from Po to Fm are well reproduced in the calculations. The major influence of the deformed-shell corrections for neutrons is indicated and provides a convenient framework for the interpretation of observed trends in the data and for the prediction of new results. The scission-point configurations derived from the model provide an interpretation of the ''saw-tooth'' neutron emission curve as well as previously unexplained observations on the variation of TKE for isotopes of U, Pu, Cm, and Cf; structure in the width of total kinetic energy release as a function of fragment mass ratio; and a difference in threshold energies for symmetric and asymmetric mass splits in the fission of Ra and Ac isotopes.
- Research Organization:
- Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439
- OSTI ID:
- 7250360
- Journal Information:
- Phys. Rev., C; (United States), Journal Name: Phys. Rev., C; (United States) Vol. 14:5; ISSN PRVCA
- Country of Publication:
- United States
- Language:
- English
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A=220 & above
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653007 -- Nuclear Theory-- Nuclear Models-- (-1987)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ACTINIDES
ALKALINE EARTH METALS
CALIFORNIUM
CURIUM
ELEMENTS
EMISSION
ENERGY SPECTRA
FERMIUM
FISSION
FISSION SPECTRA
LIQUID DROP MODEL
MATHEMATICAL MODELS
METALS
NEUTRON EMISSION
NUCLEAR MODELS
NUCLEAR REACTIONS
POLONIUM
RADIUM
SHELL MODELS
SPECTRA
STATISTICAL MODELS
STRUTINSKY THEORY
TRANSPLUTONIUM ELEMENTS
TRANSURANIUM ELEMENTS
URANIUM