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International audience; An IN2P3-JINR collaboration has launched a project called GABRIELA at the Flerov Laboratory for Nuclear Reactions (FLNR) within the Joint Institute for Nuclear Research (JINR) in Dubna (Russia). The goal of the project is to perform gamma-ray and internal conversion electron spectroscopy of heavy nuclei produced in fusion-evaporation reactions and transported to the focal plane of the recoil separator VASSILISSA. During five experimental campaigns of GABRIELA, the detection system has gained in sensitivity and new spectroscopic information has been obtained for 249Fm, 251Fm, 253No and 255Lr.

The fusion excitation function for 36S+48Ca with positive Q‐value for the compound nucleus formation, has been measured from near the barrier down to very low energies, where “fusion hindrance” may be expected. No evidence of hindrance shows up in the measured energy range. Coupled‐channels calculations have been performed with a large diffuseness parameter of the Wood‐Saxon potential, reproducing the data above and below the barrier.

In 2004, the GABRIELA (Gamma Alpha Beta Recoil Investigation with the Electromagnetic Analyzer VASSILISSA) collaboration started a twofold scientific program at the FLNR (Dubna) laboratory : (a) the systematic study of the behaviour of single particle states within isotopic and isotonic chains with Z = 100–104 as N varies from 152 to 162 and (b) the study of isotopes for which very little spectroscopic information is known. After discussing the Physics motivations and the experimental setup, some new results concerning the structure of 249Fm and 253No nuclei, and some preliminary results on the decay of 217Pa decay are presented.

Presently available experimental information on spontaneous fission of transfermium elements mainly concerns partial half ‐ lives. In addition, for Fm and No isotopes and for a few Md, Lr and Rf isotopes the total kinetic energy (TKE) and mass distributions of fission fragments from spontaneous fission were also accurately measured. Recoil in — flight separator VASSILISSA is widely used for the synthesis and study of decay properties of heavy and superheavy nuclei. It is planned in the future to measure the TKE and multiplicity distribution of prompt neutrons in spontaneous fission of other No. Now, the search of alternative methods of the neutrons detection was realized. During the search, with colleagues from Skobeltsyn Institute of Nuclear Physics (SINP MSU), the properties of some inorganic scintillators, was investigate.

Thirty‐four new nuclides with Z = 104–116, 118 and N = 161–177 have been synthesized in the complete‐fusion reactions of 238U, 237Np, 242,244Pu, 243Am, 245,248Cm, and 249Cf targets with 48Ca beams. The masses of evaporation residues were identified through measurements of the excitation functions of the xn‐evaporation channels and from cross bombardments. The decay properties of the new nuclei agree with those of previously known heavy nuclei and with predictions from different theoretical models. A discussion of self‐consistent interpretations of all observed decay chains originating from the parent isotopes 282,283112, 282113, 286–289114, 287,288115, 290–293116, and 294118 is presented. Decay energies and lifetimes of the neutron‐rich superheavy nuclei as well as their production cross sections indicate a considerable increase in the stability of nuclei with the approach to the theoretically predicted nuclear shells with N = 184 and Z = 114.

Results of the experiments aimed at the study of fission and quasi‐fission processes in the reactions 12C+204Pb, 48Ca+144,154Sm, 168Er, 208Pb, 238U, 244Pu, 248Cm; 58Fe+208Pb, 244Pu, 248Cm, and 64Ni+186W, 242Pu are presented. The choice of the above‐mentioned reactions was inspired by the experiments on the production of the isotopes 283112, 289114 and 283116 at Dubna using the same reactions. The 58Fe and 64Ni projectiles were chosen since the corresponding projectile‐target combinations lead to the synthesis of even heavier elements. The experiments were carried out at the U‐400 accelerator of the Flerov Laboratory of Nuclear Reactions (JINR, Russia), the XTU Tandem accelerator of the National Laboratory of Legnaro (LNL, Italy) and the Accelerator of the Laboratory of University of Jyvaskyla (JYFL, Finland) using the time‐of‐flight spectrometer of fission fragments CORSET and the neutron multi‐detector DEMON. The role of shell effects and the influence of the entrance channel asymmetry and the deformatio...

By employing the kinematic separator VASSILISSA and the beams of 20,22Ne, 24,26Mg, 40Ar and 40Ca we studied 18 projectile‐target combinations leading to formation of compound nuclei with atomic numbers 83‐102 and obtained xn, pxn, and αxn evaporation residues in the range of the projectile energy extending from the Coulomb barrier to the values corresponding to the compound nucleus excitation of about 100 MeV. The systematics is presented of the maximum xn reaction cross‐sections which are governed by the fissility of the reaction products. As a result, the values of macroscopic fission barriers were extracted for the neutron‐deficient nuclides in the range of Z=83–92 and N=104–134. These values are discussed in terms of contrasting with predictions of the rotating droplet model. Three isotopes, 252,253,254102, were obtained as deexcitation products of the 258102 compound nucleus formed by 22Ne and 26Mg projectiles. Some conclusions are drawn from these results about the possible use of 22Ne and 26Mg beam...