Florin Carstoiu

ROLE OF CLUSTER DEFORMATIONS ON THEIR PREFORMATION PROBABILITIES IN RADIOACTIVE CLUSTER–DECAY STUDIES

The folded Michigan — 3–Yukawa (M3Y) potential is used for the first time for calculating the WKB penetration probabilities, with deformation effects of the emitted clusters also included for the first time. For the clusters to be spheres, our calculations of the (empirical) performation probabilities P0 show that, depending rather sensitively on the choice of nuclear potential, P0 decreases with mass Ac of the emitted cluster, as is the case for other two model calculations of Blendowske–Walliser and Malik–Gupta. The deformation effects of the emitted clusters are shown to reduce the performation probabilities by an order of magnitude 103, which invalidates the simple straight line formula between — log10 P0 and Ac.

Cold (Neutronless) Alpha Ternary Fission of 252Cf: Theory and Comparison with Experiment

A new phenomenon is studied: the cold (neutronless) ternary α-accompanied fragmentation of 252Cf. The corresponding isotopic yields were calculated as the ratio of the penetrability of a given fragmentation over the sum of penetrabilities of all possible (neutronless) α-ternary fragmentations. No preformation factors were considered. We considered that close to the scission configuration the nucleons of the alpha particle form a small neck. At a given value of the neck radius a double scission takes place and a third light fragment is formed between the two heavier fragments. The corresponding barriers between the light and heavy fragment and between the alpha particle and the two heavier fragments were evaluated by using a double folding potential generated by M3Y nucleon-nucleon forces and realistic fragment ground state deformations. The relative calculated isotopic yields greater than 2 × 10-3 have been observed experimentally for the partners with known spectra. We predict that fragmentations with unknown light partners 105,106Zr, 109,110Mo and 114Ru to be identified in the present 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.

The cold fission of

We calculate the relative isotopic yields and partial half-lives of the most frequent splittings in the spontaneous cold fission of , described as a heavy cluster radioactivity. A double-folding potential and M3Y nucleon - nucleon forces are used to obtain the potential barrier between the final fragments. The penetrabilities through this barrier are estimated within the one-dimensional WKB approximation. Realistic fragment ground-state deformations are used for the calculations.

Cold alpha-accompanied fission of

The isotopic yields for the spontaneous cold ternary alpha-accompanied fission of were calculated using a double folding potential generated by Coulomb plus M3Y nucleon - nucleon forces and realistic fragment ground state deformations. The penetrabilities through the ternary fragmentation barrier were obtained within the one-dimensional WKB approximation.

BARE α-α POTENTIAL AND IMPLICATIONS ON α-MATTER PROPERTIES

Double folding α – α potentials based on the density dependent n – n Gogny interactions are constrained to reproduce the l = 0 resonance in 8Be. Shallow potentials are obtained by successive supersymmetric transformations which eliminate the l = 0 Pauli forbidden states. Implication for the EOS of cold α-matter are discussed.

Neutronless

A new type of decay corresponding to the neutronless -accompanied fragmentation of is studied. We employ a cluster model similar to the model used for the description of cluster radioactivity. No preformation factors were considered. The ternary relative isotopic yields were calculated as the ratio of the penetrability of a given ternary fragmentation over the sum of penetrabilities of all possible ternary neutronless fragmentations. The corresponding barriers between the light and heavy fragments and between the cluster and the two heavier fragments were computed with the help of a double-folding potential generated by M3Y-NN effective interaction and realistic fragment ground-state deformations. Also, we studied the influence of the fragment excitation energies on the yields, by including the level densities and the -stretching of the fragments. The new phenomenon could be experimentally observed by the triple-gamma coincidence technique between the fragments and .