UBC Theses and Dissertations
Re-investigation of the excited states of Gd 154 Ng, Leung-Kai
The excited states of Gd 154 obtained from the decay of Eu 154 have been investigated. Precise measurements of the energies and intensities of the gamma transitions have been made, using Lithium-drifted Germanium detectors. A revised decay scheme is presented in which all the gamma transitional energies agree with the corresponding energy differences between levels to within 1 Kev. A 1263.3 Kev level is established by the presence of a gamma transition of 892.7 Kev. Two other gamma transitions of energies, 903.6 Kev and 582.1 Kev from the negative-parity levels to the 2⁺ beta excited level have also been discovered. The proper locations of the 995.9 Kev and 1004.5 Kev in the decay scheme are confirmed by a gamma-gamma coincidence method using a Germanium detector and a NaI(Tl) scintillator. The energies and intensities of the internal conversion electrons and the beta transitions have been measured by an intermediate image spectrometer. Their values are quite consistent with the established decay scheme. Theoretical values of the energy levels and the branching ratios for gamma transitions have been calculated, using the Asymmetric Rotator Model (J.P. Davidson's treatment). The 'stiffness' parameter of the nucleus µ and its asymmetry parameter γ obtained are 0.402 and 11.52 degrees respectively. Comparison of the experimental and theoretical energies of seven positive-parity levels gives a root-mean-square deviation of 1.5 %. Three out of the four experimental branching ratios are in good agreement with the theoretical values. The monopole transition probability for the transition from the 0⁺ beta excited state to the 0⁺ ground state measured also agrees with the present theoretical calculation.
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