Experimental study of the quasifission, fusion-fission, and de-excitation of Cf compound nuclei
Date
2015
Authors
Khuyagbaatar, J.
Hinde, David
Carter, I. P.
Dasgupta, M.
Düllmann, Ch. E.
Evers, M.
Luong, D. H.
du Rietz, R.
Wakhle, A.
Williams, E.
Journal Title
Journal ISSN
Volume Title
Publisher
American Physical Society
Abstract
Background: The fusion-evaporation reaction at energies around the Coulomb barrier is presently the only way
to produce the heaviest elements. However, formation of evaporation residues is strongly hindered due to the
competing fusion-fission and quasifission processes. Presently, a full understanding of these processes and their
relationships has not been reached.
Purpose: This work aims to use new fission measurements and existing evaporation residue and fission excitation
function data for reactions forming Cf isotopes to investigate the dependence of the quasifission probability and
characteristics on the identities of the two colliding nuclei in heavy element formation reactions.
Method: Using the Australian National University’s 14UD electrostatic accelerator and CUBE detector array,
fission fragments from the 12C + 235U, 34S + 208Pb, 36S + 206Pb, 36S + 208Pb, and 44Ca + 198Pt reactions were
measured. Mass and angle distributions of fission fragments were extracted and compared to investigate the
presence and characteristics of quasifission.
Results: Mass-angle-correlated fission fragments were observed for the 44Ca + 198Pt reaction; no correlation
was observed in the other reactions measured. Flat-topped fission-fragment mass distributions were observed
for 12C + 235U at compound-nucleus excitation energies from 28 to 52 MeV. Less pronounced flat-topped
distributions were observed, with very similar shapes, for all three sulfur-induced reactions at excitation energies
lower than 45 MeV.
Conclusions: A high probability of long-time-scale quasifission seems necessary to explain both the fission and
evaporation residue data for the 34S + 208Pb and 36S + 206Pb reactions. Flat-topped mass distributions observed
for 12C- and 34,36S-induced reactions are suggested to originate both from late-chance fusion-fission at low
excitation energies and the persistence of shell effects at the higher energies associated with quasifission
Description
Keywords
Citation
Collections
Source
Physical Review C - Nuclear Physics
Type
Journal article
Book Title
Entity type
Access Statement
Open Access
License Rights
Restricted until
Downloads
File
Description