Dorin N. Poenaru

Deformation energy of superheavy nuclei

We study the nuclear deformation energy of superheavy nuclei by using the macroscopic - microscopic method. Nuclear shape is determined by three independent shape coordinates: separation distance between the fragment centres; mass asymmetry, and neck radius. The Yukawa-plus-exponential model gives the macroscopic energy. Shell and pairing (microscopic) corrections are calculated on the basis of a superasymmetric two-centre shell model. Various spherical magic numbers in the region of superheavy nuclei are obtained by changing the strength of the spin - orbit coupling in the two-centre shell model. A complete set of and values have been obtained leading to magic numbers up to 126 for protons and 184 for neutrons (including Z = 114, 120 and N = 172). Potential energy surfaces for nuclei , , and are plotted versus the separation distance and mass asymmetry. Compact shapes, typical for synthesis by fusion reactions or cold fission, are assumed.

Synthesis of 286114 and 290114 using low-energy fusion channels

Low-energy fusion reactions are studied in order to obtain 286114 and 290114 elements. Potential energy surfaces are calculated as the result of dynamic minimization with independent deformations of the target and projectile, small semiaxis of the projectile and distance between centres as degrees of freedom. An advanced binary macroscopic–microscopic method is used to obtain the deformation energy and the Werner–Wheeler approximation yields the mass tensor. Charge asymmetry is varied for the same mass asymmetry channel belonging to an energy valley. The highest penetrability values are obtained for cold fusion channels with a 142Ba projectile for 286114 and 104Kr, 108Sr and 112Zr leading to 290114.

Fragment configurations in multi-cluster fission

Besides fission into two or three fragments, a heavy or superheavy nucleus spontaneously breaks into four, five or six nuclei, of which two are asymmetric or symmetric heavy fragments and the others are light clusters. Examples are presented for the cold fission of 252Cf, in which the emitted clusters are: 2α, α + 10Be, 3α, α + 6He + 10Be and 4α. A comparison is made with the recently observed 252Cf cold binary fission and cold ternary (accompanied by an α particle or by 10Be cluster) fission. The strong shell effect associated with the doubly magic heavy fragment 132Sn is emphasized. From the analysis of different configurations of fragments we conclude that the most favourable mechanism in such a decay mode should be cluster emission from an elongated neck formed between the two heavy fragments.

Recent Advances in Cluster Radioactivities

The physics of nuclear decay modes by spontaneous or beta-delayed emission of charged or neutral particles from nuclei has been developed intensively.1,2 A real progress has been achieved in the understanding of newly discovered phenomena on the basis of our unified approach of cluster radioactivities, cold fission, and α-decay.3–5 A system exhibiting such kind of processes may be viewed as a nuclear molecule.6

Neck Influence on Fission Paths

The neck region generates a microscopic potential, derived in correlation with the necking region within the fission‐like shape on the potential theory basis. The whole microscopic potential is of the two‐center type, yielding the evolution of proton and neutron level schemes from one parent to two completely separated fragment nuclei. The shell corrections are calculated using the neck in single‐particle levels. The total deformation energy is obtained from the macroscopic‐microscopic method. As an application, dynamic calculation is performed for the fission of 236Pu, using the multidimensional minimization within the total space of deformation of two spheroids joined by a smoothed necking region.

The Quasimolecular stage of ternary fission

We developed a three-center phenomenological model,able to explain qualitatively the recently obtained experimental results concerning the quasimolecular stage of a light-particle accompanied fission process. It was derived from the liquid drop model under the assumption that the aligned configuration, with the emitted particle between the light and heavy fragment, is reached by increasing continuously the separation distance, while the radii of the heavy fragment and of the light particle are kept constant. In such a way,a new minimum of a short-lived molecular state appears in the deformation energy at a separation distance very close to the touching point. This minimum allows the existence of a short-lived quasi-molecular state, decaying into the three final fragments.The influence of the shell effects is discussed. The half-lives of some quasimolecular states which could be formed in the

Nuclear quasi-molecular states in ternary fission

^{10}

Shell closure at the touching point of nuclear fragments

Be and

Approaching 100Sn by Cluster Radioactivities

^{12}

Atomic nuclei decay modes by spontaneous emission of heavy ions.

C accompanied fission of