München 2006 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

HK: Physik der Hadronen und Kerne

HK 35: Kernphysik/Spektroskopie

HK 35.6: Vortrag

Mittwoch, 22. März 2006, 18:15–18:30, C

Nonexistence of low-energy symmetric fission — •Geneviève MOUZE — University of Nice, France

The so-called symmetric (or bimodal) fission is nothing else than a partially barrier-free asymmetric fission. In the narrowly symmetric fission mode of 258Fm (s.f.) (1), the width of only 8 u of the peak at symmetry of the fragment mass spectrum results from the fact that for only two fragment pairs ( 128Sn-130Sn, 126Sn-132Sn) the total binding energy- release Q is greater than their individual Coulomb barrier B. The sphericity correction to apply to B for Sn-fragment pairs of 258Fm can be determined. The broadly symmetric mass spectrum observed in trans-Md nuclei (e.g.266Hs) results from the greater number of mass splits for which Q is greater than B. These observations show that the concept of fission barrier has to be revisited. Here the major role is played by the electrostatic properties of individual binary configurations. But another kind of fission barrier can result from the lack of activation energy of a primordial dinuclear system (e.g. 208Pb-28Ne in 238U). (1) D.C. Hoffman et al., Los Alamos Report UR - 77, 29 01(1977); E.K. Hulet et al. P.R.C.21 (1980) 966.