Binary Cold Fission Research Articles

Complex fission phenomena

Complex fission phenomena are studied in a unified way. Very general reflection asymmetrical equilibrium (saddle point) nuclear shapes are obtained by solving an integro-differential equation without being necessary to specify a certain parametrization. The mass asymmetry in binary cold fission of Th and U isotopes is explained as the result of adding a phenomenological shell correction to the liquid drop model deformation energy. Applications to binary, ternary, and quaternary fission are outlined.

Probing mean field of neutron rich nuclei by cold fission

We propose the cold (neutronless) fission process as a tool for probing mean field properties of exotic neutron rich nuclei. The fissioning state is described as a resonance in the potential well between the emitted fragments. Coupled channels analysis shows that the double fine structure of the binary cold fission is very sensitive to the density distribution. In this way cold fission can be used to investigate the density profile of neutron rich fragments.

Orientations of fragments emitted in binary cold fission of 252Cf

The dependence of the driving potential on the orientation of fragments at scission is investigated for the case of cold fission of 252Cf. It is shown that in the case of cold fission the fragments exclusively emerge at scission in the pole–pole configuration. However, quantum fluctuations enable small deviations from this configuration during the tunnelling process. The mass yields of fission fragment pairs in the cold fission of 252Cf are computed for pole–pole and equator–equator orientations and are compared to the experimental data.

Spontaneous heavy cluster emission rates using microscopic potentials

The nuclear cluster radioactivities have been studied theoretically in the framework of a microscopic superasymmetric fission model (MSAFM). The nuclear interaction potentials required for binary cold fission processes are calculated by folding in the density distribution functions of the two fragments with a realistic effective interaction. The microscopic nuclear potential thus obtained has been used to calculate the action integral within the WKB approximation. The calculated half lives of the present MSAFM calculations are found to be in good agreement over a wide range of observed experimental data.

Double fine structure in binary cold fission

We give a description of the binary cold fission process of 252Cf within the stationary scattering formalism. The decay of the dinuclear system (quasi-molecule) consists in the tunnelling of a metastable state from an internal region, where the nucleus–nucleus potential makes a quasi-molecular pocket due to the interplay of repulsive and attractive nuclear forces and the Coulomb force, to the asymptotic region which is governed solely by the Coulomb repulsion. As a transverse internal motion, we suppose angular oscillations of the fragments up to the scission point. In the external region these vibrations transform into rotations. The nuclear interaction is given by a double-folding procedure using M3Y forces plus a repulsive contact potential. For the experimental Q-value we find several resonant states of the binary system, depending on the repulsive strength. We predict a strong dependence of decay widths upon the internal structure of the considered resonant state. Therefore the measured yields of the two fragments with given angular momenta in coincidence are able to provide more insight into the internal molecular dynamics of the decaying dinuclear system.

Quasimolecular resonances in the binary cold fission of252Cf

We give a description of the binary cold fission process of ${}^{252}\mathrm{Cf}$ within the stationary scattering formalism. The nuclear interaction is given by a double folding procedure using M3Y forces plus a repulsive contact potential. For the experimental Q value we find several resonant states of the binary system, depending on the nuclear repulsive strength. We predict a strong dependence of decay widths upon the internal structure of the considered resonance state. Therefore the measured yields of the two fragments with given angular momenta in coincidence are able to give the information concerning the internal molecular dynamics.

Role of the higher static deformations of fragments in the cold binary fission of252Cf

We study the binary cold fission of $^{252}$Cf in the frame of a cluster model where the fragments are born to their respective ground states and interact via a double-folded potential with deformation effects taken into account up to multipolarity $\lambda=4$. The preformation factors were neglected. In the case when the fragments are assumed to be spherical or with ground state quadrupole deformation, the $Q$-value principle dictates the occurence of a narrow region around the double magic $^{132}$Sn, like in the case of cluster radioactivity. When the hexadecupole deformation is turned on, an entire mass-region of cold fission in the range 138 - 156 for the heavy fragment arise, in agreement with the experimental observations. This fact suggests that in the above mentioned mass-region, contrary to the usual cluster radioactivity where the daughter nucleus is always a neutron/proton (or both) closed shell or nearly closed shell spherical nucleus, the clusterization mechanism seems to be strongly influenced by the hexadecupole deformations rather than the $Q$-value.