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The weakly collective nucleus 94Mo has been considered an excellent example of quadrupole vibrational mixed-symmetry structure. Algebraic models such as the interacting boson model-2 have been largely unsuccessful in describing the structure of the 4 2 + state, due to the strong M1 transition between the 4 2 + and 4 1 + states, and the low energy of the 4 2 + state. In this Letter, we show that introducing g-bosons into the interacting boson model-2 allows for the first time a description of the electromagnetic decay properties of the low-lying 4 + states in 94Mo within an algebraic model. The hexadecapole degree of freedom is shown to be important for the description of the collective low-energy structure of nuclei in this region.

We measured the lifetimes of the ${2}_{1,2}^{+}$ and ${4}_{1}^{+}$ states in ${}^{98}$Ru in order to reduce their uncertainties and resolve the discrepancies in the literature for the lifetime of the ${4}_{1}^{+}$ state. Coulomb excitation in inverse kinematics was used to populate excited states in ${}^{98}$Ru, and the recoil distance doppler shift (RDDS) method was employed using the nNew Yale plunger device (NYPD). This technique combined with inverse Coulomb excitation requires several corrections due to relativistic and deorientation effects but yields high precision lifetimes. The determined ${B}_{4/2}=B({4}_{1}^{+}\ensuremath{\rightarrow}{2}_{1}^{+})/B({2}_{1}^{+}\ensuremath{\rightarrow}{0}_{1}^{+})=1.86(16)$ agrees well with the vibrational limit. In order to analyze the data, a new method for the deorientation correction of RDDS data was developed using the perturbation of experimental angular correlations. The simultaneous measurement of deorientation and lifetime of a given state and its application are discussed. The method is suitable for radioactive beam experiments.

The transient field (TF) technique in inverse kinematics was used to measure the g factors of the low lying 2{sub 1}{sup +}, 4{sub 1}{sup +}, and 2{sub 2}{sup +} states in {sup 106}Pd. The g factor of the 4{sub 1}{sup +} state was determined and the g(2{sub 1}{sup +}) and g(2{sub 2}{sup +}) factors were remeasured. The values of g(2{sub 1}{sup +}) and g(2{sub 2}{sup +}) had been determined earlier in integral perturbed angular correlation (IPAC) experiments and the value of the former served to calibrate the TF. The three g factors, g(2{sub 1}{sup +}), g(2{sub 2}{sup +}), and g(4{sub 1}{sup +}), agree with each other and with the collective Z/A value. The uncertainties in the g(2{sub 2}{sup +}) and g(4{sub 1}{sup +}) factors remain fairly large in spite of long measuring times because of the weak excitation of the two-phonon states. The lifetimes of the 2{sub 2}{sup +} and 4{sub 1}{sup +} states were newly determined from line-shape fits.

The nucleus $^{140}\mathrm{Nd}$ was investigated using $\ensuremath{\gamma}$-$\ensuremath{\gamma}$ coincidence and angular-correlation techniques following the $\ensuremath{\epsilon}/{\ensuremath{\beta}}^{+}$ decay of $^{140}\mathrm{Sm}$ and $^{140}\mathrm{Pr}$. Spins, $\ensuremath{\gamma}$-decay intensities, and $E2/M1$ mixing ratios were extracted from the data. The ${2}_{3}^{+}$ and ${2}_{4}^{+}$ states were identified as possible mixed-symmetry states, based on mixing ratios obtained for observed decays to the ${2}_{1}^{+}$ state. The relationship between the decay pattern of these two candidate states and underlying shell structure in this mass region is discussed.

The energies of subsets of excited 0+ states in geometric collective models are investigated and found to exhibit intriguing regularities. In models with an infinite square well potential, it is found that a single formula, dependent on only the number of dimensions, describes a subset of 0+ states. The same behavior of a subset of 0+ states is seen in the large boson number limit of the Interacting Boson Approximation (IBA) model near the critical point of a first order phase transition, in contrast to the fact that these 0+ state energies exhibit a harmonic behavior in all three limiting symmetries of the IBA. Finally, the observed regularities in 0+ energies are analyzed in terms of the underlying group theoretical framework of the different models., 9 pages, 3 figures, added reference [38]

Multipole mixing ratios for transitions between excited 2+ states and the 21+ state in 140Nd are measured using angular correlation techniques for beta decay reactions. Two transitions with dominant M1 components are identified, and the higher‐lying 2+ states involved in these transitions are presented as candidates for the one‐phonon mixed‐symmetric 2+ state in 140Nd. Assuming pure two‐state mixing between the one‐phonon 2+ state and a presumed three‐phonon symmetric state yields a mixing matrix element between these states, which is discussed in terms of shell effects on mixed‐symmetric behavior in the N = 80 isotones.

The lifetime of the 120Te first‐excited 2+ state is measured using the recoil distance Doppler shift (RDDS) method after population by inverse‐kinematics Coulomb excitation. The resulting mean lifetime of 10.4(2) ps provides a factor of ten improvement in precision relative to the previously accepted value. A number of necessary corrections are discussed stemming from relativistic effects due to large recoil velocities.

The $g$ factor of the ${2}_{1}^{+}$ state of $^{170}\mathrm{Hf}$ was measured by perturbed \ensuremath{\gamma}-\ensuremath{\gamma} angular correlation in a static external magnetic field. The result, $g({2}_{1}^{+})=0.28$(5), extends the systematics of $g$ factors of even-even Hf isotopes to $N=98$ and enables a better test of theoretical models. The $g({2}_{1}^{+})$ experimental values of these isotopes exhibit a remarkable constancy as a function of neutron number. This phenomenon, which was also observed for other isotopic chains in the Gd--W range, is explained in terms of a recently proposed empirical model.