Indirect studies of astrophysical reaction rates through transfer reactions

摘要

The work in this thesis describes two experiments which use transfer reactions to perform spectroscopic studies of nuclei in order to improve reaction rates in astrophysical environments.udThe first experiment is an indirect study of the 34S(p,γ)35Cl reaction rate at energies relevant to classical novae temperatures. By reducing uncertainties in this reaction it may be possible to use 32S/34S isotopic ratio as a diagnostic tool to determine pre-solar grain paternity. A study of the 34S(3He,d)35Cl transfer reaction was performed to identify energy levels in the astrophysically relevant energy region and assign spin and parity to these new states. A new reaction rate has been calculated from this spectroscopic information and is the first experimental measurement of the 34S(p,γ)35Cl reaction rate. Using this new rate it was concluded that it is now possible to determine the paternity of pre-solar grains using the 32S/34S isotopicudratio.udThe second experiment measured two proton transfer reactions, (3He,d) and (α,t), with the aim of making spin assignments of states above the neutron threshold in 27Al. Combined with information from complementary experiments this information would be used to calculate new 26Al(n,p/α) reaction rates. Direct comparison ofudthe two transfer reactions should allow for low and high spin states to be identified, however due to lower than expected cross sections useful information could not beudextracted from the (α,t) reaction. The experimental resolution was insufficient to resolve individual states with the (3He,d) reaction, however due to the selectivityudof the reaction it appears that many of the previously known states show low spin behaviour and are likely not relevant to the reaction rate at astrophysicaludtemperatures. In addition, the non-observation of 23 states known to exist in 27Al may indicate they are high spin and further measurements of these states should beudperformed in order to calculate new 26Al(n,p/α) reaction rates.