|PSI - Group
A comprehensive experimental investigation
and theoretical modelling
of light-ion induced reaction mechanisms in medium mass targets
from the Coulomb barrier to the fission threshold
The experimental methods
involve both the spectroscopy of the residues created and the light
particles emitted in the reaction.
The experiments are carried out at iThemba LABS by the Milano-WITS-iThemba-Stellenbosch collaboration.
- Stacked Foil Spectroscopy
Momenta by Doppler Gamma - Ray Spectroscopy
- Light particle emission
were found to be
fusion, as well as
fusion following the breakup of the projectile, particularly into alpha
like fragments or the
of a single nucleon
based on tracking the time evolution of the composite system formed
after the reaction mechanisms mentioned above has been continuously developed
by comparisons to the experiments.The time evolution of the composite system
is followed using a time differential method adapted from the Boltzmann
Master Equation theory and coupled to a Monte Carlo approach, implemented
at each time step. The theory can produce probability distributions for all
relevant observables of the de-excitation by emission of light particles,
from the fast stage stage through to the stage of the equilibrated residue.
and outputs to 2004
role of pre-equilibrium emission has been found to be more significant
entrance channel energy dependence of the mean field is significant.
fast and efficient de-excitation mechanisms have been discovered.
alpha re-emission after a few interactions in the peripheral region
of the target
emission of intermediate mass fragments via a coalescence mechanism.
During the fast stage of the interaction, a group of nucleons may be identified
as being correlated in momentum space. The probability for these correlated
nucleons to be emitted as a medium mass fragment can be evaluated based
partly on the cross section for the inverse process.
excitation of the target by the projectile or the fusing fragment has been
evidenced, and represents a friction mechanism. This effect accounts
for the softening of the breakup fragment spectra.
- A new
method of probing nuclear reaction mechanisms based on 8Be spectroscopy has been
developed. This allows for an experimental distinction to be made between
intial state and final state interactions.
is a high yield of fragments similar in mass to alpha-like particles.
It was shown these are not produced in final state reactions. Instead, one needs to develop
the understanding of the break-up and co-alescence processes.