Speaker
Aleksandra Kelic
(GSI)
Description
Fission can have an important influence on the termination of the r-process and on
the abundances of long-lived actinides, which are relevant for determinating the
age of the Universe. Fission can also influence the abundances of nuclei in the
region A~90 and 130 due to the fission cycling. In order to quantitatively
understand the fission role in the r process, two important pieces of information
are needed: the fission-barrier heights and mass- and charge-distributions of the
fission fragments.
Unfortunately, experimental information is only available for nuclei in a limited
region of the nuclide chart, and for heavy r-process nuclei one has to rely on
theoretical predictions. Recently, important progress has been made in developing
full microscopic approaches to nuclear fission. Nevertheless, due to the complexity
of the problem, this type of calculations is still difficult to apply to heavy
nuclei and, moreover, the precission of these models is often still low.
In this contribution we will concentrate on macroscopic-microscopic approaches that
could help us understanding the contribution of fission to the r process. Firstly,
using available experimental data on saddle-point and ground-state masses, we will
present a detailed study on the predictions of different models concerning the
isospin dependence of saddle-point masses [1]. It will be shown that several
models yield unrealistic barriers for very neutron-rich nuclei. Secondly, we will
present a model for calculating mass- and charge-distributions of fission
fragments, that can correctly predict the transition from double-humped to single-
humped distributions with decreasing mass of the fissioning system and increasing
excitation energy in the light actinides. This model has recently [2] been used to
calculate fission-fragment distributions in neutrino-induced fission of r-process
nuclei.
[1] A. Kelic and K.-H. Schmidt, accepted by Phys. Lett. B
[2] A. Kelic et al, Phys. Lett. B 616 (2005) 48
Author
Aleksandra Kelic
(GSI)
Co-authors
Dr
Karl-Heinz Schmidt
(GSI)
Prof.
Karlheinz Langanke
(GSI)
Mr
Nikolaj Zinner
(Aarhus University)
