Studies of Formation of Fusion Evaporation Residues with Z≥83 in Heavy Ion Reactions

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 beams for synthesis of Z=106–110 nuclides having neutron numbers close to the predicted island of stability around N=162.