The ¹⁶O(α,γ)²⁰Ne and ²⁸Si(α,γ)³²S Reactions at Low Energy

• Main Author: Toevs, James Waldo
• Format: Others
• Language: en
• Published: 1970
• Online Access: https://thesis.library.caltech.edu/5813/1/Toevs_jw_1970.pdf; Toevs, James Waldo (1970) The ¹⁶O(α,γ)²⁰Ne and ²⁸Si(α,γ)³²S Reactions at Low Energy. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/MHA9-5P97. https://resolver.caltech.edu/CaltechTHESIS:05172010-110558216 <https://resolver.caltech.edu/CaltechTHESIS:05172010-110558216>

The ²⁸Si(α,γ)³²S and ¹⁶O(α,γ)²⁰Ne reactions have been investigated to provide data for the calculation of the stellar rates of these reactions. The gamma rays were counted with a NaI(Tl) detection system having a high detection efficiency which is approximately independent of the gamma-ray cascade structure of a nuclear level; the detection efficiency was determined experimentally. The reaction ²⁸Si(α,γ)³²S was studied for He⁺ bombarding energies from 1.4 to 2.7 MeV, and in this region, five new resonances were found, and their strengths, (2J+1) Γ_α Γ_γ/ Γ were measured. An upper limit for the cross section has also been established for bombarding energies below 1.7 MeV. The ¹⁶O(α,γ)²⁰Ne reaction was investigated in the energy region from 0.85 to 1.8 MeV; strengths for the previously known resonances were measured, and an upper limit for the cross section was determined for energies below 1 MeV. Stellar interaction rates and photodisintegration rates have been calculated from the measured resonance strengths, and semi-empirical fits to these rates have been given to facilitate astrophysical calculations.