Evidence of Z=120 compound nucleus formation from lifetime measurement in the 238^{238}U+Ni reaction at 6.62 MeV/nucleon

CAS NIMThe formation of compound nuclei with Z=120, followed by fission, has been evidenced in the 238U+Ni system at 6.62 MeV/nucleon by very long reaction times (t ~ 10-17s) measured by the blocking technique in single crystals

Fission time measurements: a new probe into super-heavy element stability

Accepted for publication in Physical Review LettersReaction mechanism analyses performed with a 4 $\pi$ detector for the systems $^{208}$Pb+Ge, $^{238}U+Ni and$^{238}$U+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$^{208}$Pb+Ge reactions have shorter lifetimes, close to or below the sensitivity limit of the experiment

Bimodality: a possible experimental signature of the liquid-gas phase transition of nuclear matter

We have observed a bimodal behaviour of the distribution of the asymmetry between the charges of the two heaviest products resulting from the decay of the quasi-projectile released in binary Xe+Sn and Au+Au collisions from 60 to 100 MeV/u. Event sorting has been achieved through the transverse energy of light charged particles emitted on the quasi-target side, thus avoiding artificial correlations between the bimodality signal and the sorting variable. Bimodality is observed for intermediate impact parameters for which the quasi-projectile is identified. A simulation shows that the deexcitation step rather than the geometry of the collision appears responsible for the bimodal behaviour. The influence of mid-rapidity emission has been verified. The two bumps of the bimodal distribution correspond to different excitation energies and similar temperatures. It is also shown that it is possible to correlate the bimodality signal with a change in the distribution of the heaviest fragment charge and a peak in potential energy fluctuations. All together, this set of data is coherent with what would be expected in a finite system if the corresponding system in the thermodynamic limit exhibits a first order phase transition.Comment: 30 pages, 31 figure

Model-independent tracking of criticality signals in nuclear multifragmentation data

We look for signals of criticality in multifragment production in heavy-ion collisions using model-independent universal fluctuations theory. The phenomenon is studied as a function of system size, bombarding energy, and impact parameter in a wide range of INDRA data. For very central collisions (b/b_ma

Evolution of the multifragmentation of the Xe + Sn system from 25 up to 150 AMeV

ALADI

Dynamical and thermodynamical features in fragment production

NIM, Expérience GANILInternational audienceExperimental data obtained at GANIL and GSI facilities using the 4$pi$ multidetector INDRA are selected to discuss dynamical and thermo-dynamical features on the fragmentation mechanisms at intermediate energies. Few topics are presented each of them addressing a key issue of the field

Long-lived Super-Heavy Elements Evidenced Through Fission Time Measurements

Fission time measurements have been undertaken in the super-heavy elements domain around Z=120, using the crystal blocking technique. Complete fusion followed by fission mechanisms have been evidenced from time measurements and detailed kinematics analysis