[en] Problem of experimental confirmation of deformed shapes of superheavy nuclei situated in the neighbourhood of ²⁷⁰Hs is discussed. Measurement of the energy E₂₊ of the lowest 2+ state in even-even species of these nuclei is considered as a method for this confirmation. The energy is calculated in the cranking approximation for heavy and superheavy nuclei. The branching ratio p₂₊/p₀₊ between α decay of a nucleus to this lowest 2+ state and to the ground state 0+ of its daughter is also calculated for these nuclei. The results indicate that a measurement of the energy E₂₊ for some superheavy nuclei by electron or α spectroscopy is a promising method for the confirmation of their deformed shapes. (orig.)

[en] The present work reveals the applicability of an analytical model to evaluate the alpha decay of neutron deficient isotopes as well as spontaneous symmetric fission of superheavy elements

[en] A successful experiment was performed last November - December for the production and identification of the element 106 (^261,260Sg) at GANIL using the LISE-III Wien filter. The reaction residues, produced in the reaction ⁵⁴Cr+²⁰⁸Pb, were identified at 2 bombarding energies, i.e. 4,698 A and 4,756 A MeW. The preliminary analysis identified 2 (Z=106) events for the first energy and a total of 9 events for the second one. Particularly, the good transmission of the residues combined with a satisfactory suppression of the primary beam are very encouraging for the following envisaged programme. (authors)

[en] Ground-state properties of the heaviest nuclei are analyzed in the three-dimensional deformation space {β_λ}, λ=2, 4, 6. Effects of using even larger spaces are explored. Deformation, mass, alpha-decay energy and half-life of even-even nuclei with proton number Z=90-114 and neutron number N=136-168 are studied. The ground-state energy of the nuclei is treated in the macroscopic-microscopic approach. It is found that the use a larger deformation space (in particular, a proper inclusion of the deformation β₆ in this space) significantly improves the description of experimental results and, also significantly, changes the predictions for nuclei not yet observed. (orig.)

[en] Spontaneous-fission and alpha-decay half-lives are calculated for even-even nuclei with the atomic number Z=104-110. The results reproduce rather well the existing experimental data for these nuclei and predict rather large total lifetimes for nuclei even heavier than observed up to now. The latter is mainly due to a deformed shall at the neutron number N=162-164, obtained in calculations. (orig.)

[en] Spontaneous-fission half-lives of heaviest nuclei are analyzed in a multidimensional deformation space. They are calculated in a dynamical approach, without any adjustable parameters. The potential energy is obtained by the macroscopic-microscopic method and the inertia tensor by the cranking method. The action integral is minimized by a variational procedure. Even-even nuclei with proton number Z=104-114 and neutron number N=142-176 are considered. The results reproduce rather well the existing experimental data for the considered nuclei and predict relatively long half-lives for many nuclei not yet observed, sufficient to detect them if synthesized in a laboratory. (orig.)

[en] Shell effects are extracted in the following experimental quantities: Mass, alpha-decay energy and half-life, spontaneous-fission barrier and lifetime. The heaviest even-even nuclei known experimentally, with Z=92-108 are considered. This extraction is based on the Yukawa-plus-exponential model, used for the description of the macroscopic part of nuclear mass. The effects are found to be large: e.g. they increase the spontaneous-fission half-life of some nuclei by about 15 orders of magnitude. The sensitivity of these effects to changing the macroscopic model is discussed. (orig.)

[en] Ground-state properties of the heaviest nuclei are analyzed in the three-dimensional deformation space {β_λ}, λ=2, 4, 6. Effects of using even larger spaces are explored. Deformation, mass, alpha-decay energy and half-life of even-even nulcei with proton number Z=90-114 and neutron number N=136-168 are studied. The ground-state energy of the nuclei is treated in the macroscopic-microscopic approach. It is found that the use of a larger deformation space (in particular, a proper inclusion of the deformation β₆ in this space) significantly improves the description of experimental results and, also significantly, changes the predictions for nuclei not yet observed. (orig.)

[en] We present a quantitative calculation that shows where high-kinetic-energy symmetric fission occurs and why it is associated with a sudden and large decrease in fission half-lives. We base our study on calculations of potential-energy surfaces in the macroscopic-microscopic model and a semi-empirical model for the nuclear inertia. For the macroscopic part we use a Yukawa-plus-exponential (finite-range) model and for the microscopic part a folded-Yukawa (diffuse-surface) single-particle potential. We use the three-quadratic-surface parameterization to generate the shapes for which the potential-energy surfaces are calculated. The use of this parameterization and the use of the finite-range macroscopic model allows for the study of two touching spheres and similar shapes. Since these shapes are thought to correspond to the scission shapes for the high-kinetic-energy events it is of crucial importance that a continuous sequence of shapes leading from the nuclear ground state to these configurations can be studied within the framework of the model. (orig.)

[en] The properties of the heaviest isotopes are discussed using recent results on α-energies, halflives, and branchings between the different decay modes. From the data on α- and spontaneous fission halflives and absolute masses, fission barriers and barrier widths are deduced. Shell corrections of the heaviest nuclei are obtained and compared to recent calculations. The concept of superheavy elements is examined, and it is shown that the heaviest isotopes known must be classified 'superheavy'. The production cross sections are summarized and within the extra-push model the reduced fusion probabilities in the entrance channel are discussed. It is shown that besides nuclear structure effects in the collision partners are of importance. It is concluded that targets around ²⁰⁸Pb give a double gain, on the one hand from the fact that fusion is relatively cold (1n- and 2n-channels), and on the other hand that the extra-push limitation is setting in later than the model predicts. The possibilities to make still heavier elements are restricted not by their groundstate instability but by the principal limitations of their production. (orig.)