The ¹⁶O + ¹⁶O reaction

Citation

Spinka, Harold (1971) The ¹⁶O + ¹⁶O reaction. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/XPJ4-A792. https://resolver.caltech.edu/CaltechTHESIS:11192010-105408465

Abstract

The ¹⁶O + ¹⁶O total reaction cross section was measured at six energies between E_cm = 6.80 to 11.85 MeV near the astrophysical region of interest. Angular distributions and cross sections for the production of protons, alphas and deuterons were obtained with counter telescopes in a differentially pumped gas target. No ³He or ³H were observed. Cross sections for the formation of ³¹S and ³⁰p were measured by detecting the betas from their radioactive decays. The angular distribution and cross section for production of neutrons was obtained with a "long counter" at E_cm = 12 MeV, demonstrating that the ¹⁶O (¹⁶O,pn) process accounts for over 90 % of the ³⁰P formed at this energy. The presence of such three body breakup reactions made the experimental determination of the total cross section difficult. Finally, the ¹⁶O + ¹⁶O → ¹²O (g.s.) + ²⁰Ne (g.s.) reaction was studied with a coincidence technique at E_cm = 12 MeV.

Gamma spectra were taken at several energies for a number of targets using Ge (Li) counters. Gamma lines from nuclei produced in both two and three body exit channels from ¹⁶O + ¹⁶O reactions were observed. In addition, the gamma yield as a function of bombarding energy was measured in 50 keV (c .M.) steps for both ¹⁶O + ¹⁶O and ¹²C + ¹²C. The ¹⁶O + ¹⁶O gamma yield is smoothly varying, indicating that the ¹⁶O + ¹⁶O reaction cross section does not have large fluctuations with energy similar to the structure seen in ¹²C + ¹²C reactions.

Nearly all cross sections were measured relative to the ¹⁶O + ¹⁶O elastic scattering at θ_(lab)= 45° to avoid the problems with direct current integration of heavy ion beams in gas targets. A new, more precise determination of the elastic scattering cross section at θ_cm = 90° was made for E_cm = 7.3 to 14.4 MeV in steps of 100 keV (C .M.). A previously unknown anomaly was observed near E_cm = 10.5 MeV. Elastic scattering cross sections were also obtained for ¹²C + ¹²C in steps of 60 keV C.M. energy from E_cm = 3.9 to 8.0 MeV at θ_cm = 90° In both cases, gas mixtures were used in the differentially pumped system as the target.

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