Description: The systematics of the (E2) ..gamma.. ray transition energies and the available lifetime data are used to characterize the excitation modes of the light rare-earth nuclei (N greater than or equal to 82) at different spins. The results, which include our recently obtained data on /sup 149/Gd, /sup 154/Ho, /sup 155/Er, /sup 157/Yb and /sup 158/Yb nuclei, indicate that, at low spins, the nuclear excitation mode (shapes) change from single-particle excitations (weakly oblate) in N less than or equal to 85 nuclei to quasi-vibrational (soft triaxial) in N = 86, weakly rotational (prolate) in N = 87, and rotational (prolate) in the N greater than or equal to 88 systems. At higher angular momenta, all these nuclei show a general tendency to traverse the (epsilon,..gamma..) plane towards the oblate axis, and to eventually adopt the aligned coupling mode of excitation.
Date: January 1, 1982
Creator: Baktash, C.
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