Comparison of the β-α Angular Correlations in the Beta Decays of Li⁸ and B⁸

Author: Nordberg, Martin Emery, Jr

Year: 1961

Degree: Dissertation (Ph.D.)

Advisors: Barnes, Charles A.; Weidenmuller, Hans A.; Fowler, William A.

Committee Member: Unknown, Unknown

Option: Physics

DOI: 10.7907/00je-ft97

Abstract

This thesis describes a comparison of the β-α angular correlations of the beta decays of Li8 and B8 to the 2.90-Mev α-unstable state of Be8. The data are fitted to the angular correlation function in the laboratory system, W(ϴβα) = 1 + A cos ϴβα + B cos 2ϴβα, where A and B are independently determined for each decay from measurements at ϴβα = 0°, 90°, and 180°. The coefficient, A, is due to the recoil of Be8* and has the same sign for both beta decays. The coefficient, B, arises from the interference of forbidden vector matrix elements with the allowed axial vector matrix element and changes sign in the two decays. The correlation for the Li8 decay is measured with average total β-energies of Wβ ≃ 5, 8, and 11 Mev. Both A and B are approximately linear in the energy. The correlation for the B8 decay is measured only with average total β-energy of Wβ ≃ 11 Mev. From the data with Wβ ≃ 11 Mev, the difference of the coefficients, B(Li8) - B(B8), is equal to (0.0069 ± 0.0011)Wβ. This result is compared with theoretical predictions based on the older Fermi and the newer Conserved Vector Current theories of beta decay. The experiment agrees with the prediction of the latter theory.

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