The detection of γ-rays from explosive astrophysical scenarios such as novae
provides an excellent opportunity for the study of on-going nucleosynthesis in
the Universe. Within this context, this work has addressed an uncertainty in
the destruction rate of the 18F nucleus, thought to be the primary source of
511 keV γ-rays from novae. A direct measurement of the 18F(p,α )15O cross
section has provided the opportunity to extract resonance parameters through
the R-Matrix formalism. The inferred parameters of populated states in 19Ne
include the observation of a broad 1/2+ state, consistent with a recent theoretical
prediction, which will have a significant impact on the rate of destruction of this
γ-ray producing radioisotope.
The 18O(p,α )15N reaction follows similar nuclear and kinematic processes and
is expected to occur in the hydrogen burning layers of AGB stars. Resonance
widths have been extracted from a direct measurement in the region around a
poorly constrained broad state close to the Gamow window. This has produced
a new parameter set for future reference and provides new information on the
reaction rate.
The complex R-Matrix formalism used in these analyses is a crucial tool in the
study of nuclear astrophysics reactions, and many codes have been written to
implement the complex mathematics. This thesis presents a comparison of two
publicly available codes from the JINA collaboration and a code used extensively
by the University of Edinburgh. For this, the recent results of the 18F destruction
reaction, presented here, have been used. A minor error was found within one of
the codes, and corrected. The final parameters extracted, and the resulting cross
sections calculations, are shown to be consistent between the three codes.
A further γ-ray line of interest at 1.809 MeV, characteristic of 26Al decay, has
been observed throughout the interstellar medium. If, however, this isotope is
formed in a known isomeric state, its decay bypasses the emission of this γ-ray, thus complicating the interpretation of observed γ-ray fluxes. To this end,
an experiment has been carried out, providing proof of principle of a direct
measurement of the 26mAl(p,γ)27Si reaction. The calculation of the isomeric
intensity is presented here
