Oak Ridge National Laboratory

Physics Division

Physics Division Seminars

Physics Division Seminars bring us speakers on a variety of physics related subjects. Usually these are held in the Building 6008 large Conference Room, at 3:00 pm on the chosen day, but times and locations may vary. For more information, contact our seminar chairman,

Alfredo Galindo-Uribarri
Tel (Office): (865) 574-6124  (FAX): (865) 574-1268

Thu., March 26, 2009, at 3:00 p.m. (refreshments at 2:40 p.m.)

Heaviest Nuclei

Yuri Oganessian, Joint Institute for Nuclear Research, Dubna (Russia)
Building 6008 Conference Room

One of the fundamental outcomes of the nuclear shell model is the prediction of the “stability islands” in the domain of the hypothetical superheavy elements. The enhanced stability has been expected for the deformed nuclei near Z=108 and N=162, yet much stronger effect has been predicted for heavier spherical nuclei close to the shells Z=114 and N=184, next to the doubly-magic nucleus 208Pb (Z=82, N=126). The talk is devoted to the experimental verification of these predictions – the synthesis and study of both the decay and chemical properties of the superheavy elements.

For the synthesis of the heavy nuclei fusion reactions of the nuclei of 208Pb, 209Bi with the projectiles of 50Ti, 54Cr, .., 70Zn (cold fusion) have been used that allowed us to investigate decay of the nuclides with Z=104-113 and N=151-165 in the region of the effect of the deformed shells Z=108 and N=162. The synthesis of even heavier and more neutron-rich nuclei has been carried out in the fusion reactions of 233,238U, 237Np, 242,244Pu, 245,248Cm and 249Cf with the 48Na projectiles (hot fusion), that made it possible to study decay of the nuclides with Z=104-118 (except Z=117) with the higher neutron number, N=161-177.

The decay properties of the 34 synthesized nuclei obtained in 48Na-induced reactions presents direct experimental evidence of the existence of the superheavy nuclei that considerably expand the Periodical Table of the chemical elements. Simultaneously in the chemical studies of elements 112 and 114 by methods of absorption gas chromatography the influence of the “relativistic effect” on the chemical properties of the superheavy elements was obtained for the first time.

As a separate issue, I will also discuss a forthcoming set of experiments on the synthesis of element 117 (from 249Bk + 48Ca reaction) projected in collaboration of FLNR (Dubna), ORNL (Oak Ridge), Vanderbilt University (Nashville), LLNL (Livermore), and IAR (Dimitrovgrad).

This talk is based on the results obtained in FLNR (Dubna, Russia) in collaboration with LLNL (Livermore, USA) and PSI (Villigen, Switzerland).

Physics Division Colloquium