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Physical Review Letters 108 (2012) 122701
X-ray fluorescence from the element with atomic number Z = 120
M.O. Frégeau1, D. Jacquet2, M. Morjean1, E. Bonnet1, A. Chbihi1, J.D. Frankland1, M.F. Rivet2, L. Tassan-Got2, F. Dechery3, A. Drouart3, L. Nalpas3, X. Ledoux4, M. Pârlog5, C. Ciortea, D. Dumitriu, D. Fluerasu, M. Gugiu, F. Gramegna, V.L. Kravchuk, T. Marchi, D. Fabris, A. Corsi, S. Barlini

An 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. The filling of these vacancies accompanied by X-ray emission with energies characteristic of Z=120 can take place only if the atomic transitions occur before nuclear fission. Therefore, the X-ray yield characteristic of the united atom with 120 protons is strongly related to the fission time and to the vacancy lifetimes. K X-rays from the element with Z = 120 have been unambiguously identified from a coupled analysis of the involved nuclear reaction mechanisms and of the measured photon spectra. A minimum mean fission time $\tau$_f$ = 2.5×10−18s has been deduced for Z=120 from the measured X-ray multiplicity.
1 :  GANIL - Grand Accélérateur National d'Ions Lourds
2 :  IPNO - Institut de Physique Nucléaire d'Orsay
3 :  IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers (ex DAPNIA)
4 :  DAM/DIF - DAM Île-de-France
5 :  LPCC - Laboratoire de Physique Corpusculaire de Caen
Dynamique et thermodynamique nucléaire
Physique/Physique Nucléaire Expérimentale
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