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The decay of ¹⁵²Eu Walton, Thomas George

Abstract

The excited states of ¹⁵²Sm and ¹⁵²Gd obtained from the decay of ¹⁵²Eu have been investigated. Precise measurements of the energies and intensities of the gamma-ray transitions have been made using Ge(Li) detectors. The placement of transitions in the decay schemes was aided by Ge(Li) - Ge(Li) coincidence measurements. 58 gamma-rays were observed in the decay of ¹⁵²Eu and 37 coincident transitions. Sixteen of the coincident transitions were observed for the first time in this work. The three lowest energy members of the ground state, β and γ—vibrational bands were observed in ¹⁵²Sm. Two K[sup π]= O⁻ levels were identified in ¹⁵²Sm having B(EL) ratios agreeing with adiabatic symmetric rotation model predictions. An alternate K assignment is suggested for the I = 2⁻ and 3⁻ levels at 1530 keV and 1579 keV. The effect of including band mixing in the calculations of the B(E2) ratios by the symmetric rotation model was investigated for transitions from the β and γ- vibrational bands of ¹⁵²Sm. Simple γ band mixing was found to work, within experimental error for transitions from the β- band, however the inclusion of β , γ band mixing could not bring agreement with experiment. For transitions from the β -band, both simple p band mixing and β , γ band mixing could not make the calculated ratios agree with experiment. The asymmetric rotation model of Davidson was also compared with experiment and the value of the deformation parameter γ and the softness parameter µ was found to be 11.1 and 0.396 respectively for ¹⁵²Sm. The asymmetric model was able to predict correctly the B(E2) ratios from the γ band but not from the β band. Monopole contributions in transitions from levels in the β band to levels of the same spin in the ground state were estimated and compared with the model predictions via "x" ratios. It was found that both models over-estimated the amount of the EO contribution in these transitions. Some evidence has been found for a new 1293 keV level in ¹⁵²Sm. Eleven 1^2 levels in ¹⁵²Gd were identified, seven of which could be identified to quasi-rotational bands.

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