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A survey of observed EO transition strength shows that some of the largest strength occurs for transitional nuclei whenever large mixing between almost spherical and largely deformed shapes results. This leads to the conclusion that large EO strength is not an indication of coexisting shapes but of strong mixing between nuclear states with largely different radii. In addition, we discuss the variation of EO transition rates in regions where intruder states become the nuclear ground state.We illustrate this by recent results in the A =100 region concentrating especially on the anomalously large monopoles strength and its variation in the even-even N =60 isotones as compared with the N =58 isotones.

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The 7-ray spectra accompanying the decay of 1B4 Eu(16 yr) has been studied by using an isotopically separated 164 Eu source as well as a Ge(Li) Compton suppression spectrometer. Over 150 7 rays have been detected and can be ascribed to 32 different levels. It is suggested that the positive-parity levels can be accounted for by assignment to one-and two-phonon vibrational bands, and that the negative-parity levels form the bands of the fragmented octupole state. The level structure of the K=0 and 1 members can be accounted for by assuming a strong Coriolis coupling between them. The relative E2 transition probabilities from the one-and two-phonon bands cannot be reconciled with simple two-band mixing theory. Properties associated with ZK indicate that ZK is not a good quantity in this nucleus, because of the strong mixing of the j8-and 7-vibrational bands, and that its use in the past may have given false results for properties associated with it. The level energies in keV are: ground-state band: 123.69. The K=2 octupole state is consistent with Solov'ev and co-workers' assignment of a nearly pure two-quasiparticle configuration of [411] C523]p, while the K-1 state is more consistent with its being of nearly pure [411] [532] p two-quasiparticle configuration. Consideration is given to a rotation-vibration Coriolis-type interaction between the K=0 and 1 bands and a proposed pseudo-rotor-particle-coupling Coriolis-type interaction between the K-1 and 2 bands of the octuple state. It is suggested that the levels at 1531.39, 1660.94, and 1790.4 keV form a £7coupled second vibrational band.