First forbidden beta decay of some strongly deformed nuclei

Siebren Ysbrand van der Werf

Research output: ThesisThesis fully internal (DIV)


In this thesis we present measurements of the shape factors of the first forbidden beta decays of the nuclei Tm^170, Re^186, Re^188 and Lu^176m. For Lu^176m, also the beta gamma directionalcorrelation was measured. In chapter I formulas for the observable quantities in first forbidden beta decay and the approximations that make them suitable for practical use are given. Besides the well known Kotani and Konopinski Uhlenbeck (K, U. ) approximation we propose a new one, the Modified Konopinski Uhlenbeck (M.K. U. ) approximation. In chapters IV and V the experimental equipment and the data handlÍng are described, while in chapters VI-IX the experimental results are presented. Values for the beta decay matrix elements are derived from least squares fits of the theoretical formulas to the experimental data. The rule of equal ratios predicts that all matrix elements of tensor rank 1 operators are the same for the l- '2+ and the 1-- 0-transition, apart from a common geometrical factor, since the 0- and 2- states are members of the same rotational band. Small deviations from this rule are found for Tm^170, Re^186 and Re^188. We have performed matrix element calculations on the basis of Nilsson wave functions for the deformed harmonic oscillator potential and the deformed Saxon Woods potential. The formalism necessary for these calculations is developed in chapters II and III. Our calculations do not show agreement with the experimental results as is shown in chapters VI-IX. In a general discussion given in chapter X we note some systematic features in the analysis of shape factors of first forbidden beta transitions. Possible reasons are given there for the failure of the simple shell model calculations.
Original languageEnglish
QualificationDoctor of Philosophy
  • de Waard, H., Supervisor, External person
Publication statusPublished - 1971

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