107 research outputs found
Evolution of collectivity near mid-shell from excited-state lifetime measurements in rare earth nuclei
The B(E2) excitation strength of the first excited 2+ state in even-even nuclei should directly correlate with the size of the valence space and maximize at mid-shell. A previously found saturation of B(E2) strengths in well-deformed rotors at mid-shell is tested through high-precision measurements of the lifetimes of the lowest-lying 2+ states of the Hf168 and W174 rare earth isotopes. Measurements were performed using fast LaBr3 scintillation detectors. Combined with the recently remeasured B(E2;2+1→0+1) values for Hf and W isotopes the new data remove discrepancies observed in the differentials of B(E2) values for these isotope
Structure of low-lying states in 128Ba from γ-γ angular correlations and polarization measurements
Excited State Lifetime Measurements in Rare Earth Nuclei with Fast Electronics
We investigated the collectivity of the lowest excited 2⁺ states of even-even rare earth nuclei. The B(E2) excitation strengths of these nuclei should directly correlate to the size of the valence space, and maximize at mid-shell. The previously identified saturation of B(E2) strength in well-deformed rotors at mid-shell is put to a high precision test in this series of measurements. Lifetimes of the 2⁺1 states in ¹⁶⁸Hf and ¹⁷⁴W have been measured using the newly developed LaBr₃ scintillation detectors. The excellent energy resolution in conjunction with superb time properties of the new material allows for reliable handling of background, which is a source of systematic error in such experiments. Preliminary lifetime values are obtained and discussed in the context of previous and ongoing work
\u3cem\u3eg\u3c/em\u3e Factor of the 2\u3csup\u3e+\u3c/sup\u3e\u3csub\u3e1\u3c/sub\u3e State of \u3csup\u3e172\u3c/sup\u3eHf
The g factor of the 2+1 state of 172Hf was measured using the perturbed angular correlation technique in a static external magnetic field. The result, g(2+1) = 0.25(5), is discussed in relation to the systematics of the previously reported g factors in the Hf isotopes and compared with the predictions of several models. An interesting outcome of the analysis presented in this paper is the agreement between the calculated g factors within the interacting boson approximation (IBA) and the results of a large-scale shell model calculation. This agreement supports the emphasis in the IBA on the valence space. The undershooting of the empirical g factors near midshell in both models suggests that they underestimate the role of the saturation of collectivity, which is explicitly incorporated into a phenomenological model that agrees better with the data
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