The atomic numbers and the masses of fragments formed in quasifission reactions are simultaneously measured at scission in ^{48}Ti+^{238}U reactions at a laboratory energy of 286 MeV. The atomic numbers are determined from measured characteristic fluorescence x rays, whereas the masses are obtained from the emission angles and times of flight of the two emerging fragments. For the first time, thanks to this full identification of the quasifission fragments on a broad angular range, the important role of the proton shell closure at Z=82 is evidenced by the associated maximum production yield, a maximum predicted by time-dependent Hartree-Fock calculations.
View Article and Find Full Text PDFAn atomic clock based on x-ray fluorescence yields has been used to estimate the mean characteristic time for fusion followed by fission in reactions 238U + 64Ni at 6.6 MeV/A. Inner shell vacancies are created during the collisions in the electronic structure of the possibly formed Z=120 compound nuclei.
View Article and Find Full Text PDFReaction mechanism analyses performed with a 4pi detector for the systems 208Pb + Ge, 238U + Ni and 238U + Ge, combined with analyses of the associated reaction time distributions, provide us with evidence for nuclei with Z=120 and 124 living longer than 10(-18) s and arising from highly excited compound nuclei. By contrast, the neutron deficient nuclei with Z=114 possibly formed in 208Pb + Ge reactions have shorter lifetimes, close to or below the sensitivity limit of the experiment.
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