Electromagnetic-induced fission of 238U projectile fragments, a test case for the production of spherical super-heavy nuclei

Abstract Isotopic series of 58 neutron-deficient secondary projectiles (205,206At, 205–209Rn, 208–212,217,218Fr, 211–223Ra, 215–226Ac, 221–229Th, 226–231Pa, 231–234U) were produced by projectile fragmentation using a 1 A GeV 238U beam. Cross sections of fission induced by nuclear and electromagnetic interactions in a secondary lead target were measured. They were found to vary smoothly as a function of proton and neutron number of the fissioning system, also for nuclei with large ground-state shell effects near the 126-neutron shell. No stabilization against fission was observed for these nuclei at low excitation energies. Consequences for the expectations on the production cross sections of super-heavy nuclei are discussed.