This thesis presents measurements of low-energy positron
scattering from Argon
and C60. Absolute elastic differential cross sections are
presented for positron
scattering from Argon in the energy range 2 to 50 eV, as well as
absolute total
elastic and inelastic cross sections up to 20 eV. These results
are compared with
theoretical calculations using the convergent close-coupling
(CCC) and relativistic
optical potential (ROP) methods and it was found that generally
the measurements
were in closer agreement with the CCC method than the ROP method
across the energy range, although the ROP method was an excellent
description
of the total inelastic cross section in this energy range.
Argon was also the focus of the first results from the newly
developed positron
reaction microscope. Experimental techniques were developed to
produce measurements
of the kinematics of positron-induced single ionisation of Argon.
Single
ionisation events were detected in coincidence and their momenta
reconstructed
using data analysis methods detailed in this thesis. Although
further work is
required to provide total differential cross sections, the
initial data presented in
this thesis is in alignment with expectations based upon
available theory and
experiment and provides a promising starting point for future
studies using the
positron reaction microscope.
Finally, a search was conducted for resonant features in the
total scattering
and Positronium formation cross sections of C60. Motivated by the
predictions of
Gianturco and Lucchese (1999), which indicated
experimentally-accessible resonances,
the present data does not show any features. However, the current
results
in this thesis represent the first preliminary measurements of
the total scattering
and Positronium formation cross sections for C60 and follow the
expected trend
for positron-molecule scattering. Additional data to be collected
in the future,
would allow for confirmation of the presence, or lack thereof, of
resonant features
with a higher statistical confidence
