Westfälische Wilhelms-Universität Münster
- Fachbereich Physik -
KOLLOQUIUM ÜBER SPEZIELLE FRAGEN DER PHYSIK
Montag, 16. Juni 1997
Prof. Dr. Y. Abe
Yukawa Institute for Theoretical Physics, Kyoto University
Dynamical Theory for Synthesis of Superheavy
Elements
Synthesis of superheavy elements is a long-standing important subject
in nuclear physics. In the neighbourhood of (Z = 114, N = 184), superheavy
elements are expected to exist, i.e. to be stable against fission by our
knowledge of extreme stability of closed shell structure. Recently the
Z = 112 element was synthesized by the GSI group with so-called cold fusion
reaction. The reaction mechanism is not well understood, but cross sections
are empirically inferred to be much smaller for heavier elements. We therefore
propose to explore another way, the so-called hot fusion reaction. There
we can apply dissipation-fluctuation dynamics to fusion as well as fission
processes. In a preliminary analysis, we employ the Smoluchovski equation
which is valid for cases of strong dissipation, and solve the fusion-fission
problem. As a compromise between larger fusion probability and smaller
fission probability, i.e. larger survival probability, we find an optimum
excitation energy of the reaction. It is shown that the optimum condition
is most stable, and the optimum residue cross section becomes large, if
a neutron-rich compound nucleus is formed at the beginning. This is due
to a quicker cooling by successive evaporations of neutrons with small
separation energies.
Ort: Wilhelm-Klemm-Str. 9, Hörsaal 404
Zeit: 17 Uhr c.t.
Einladender: Weiguny