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The collective wobbling mode, the strongest signature for the rotation of a triaxial nucleus, has previously been seen only in a few Lu isotopes in spite of extensive searches in nearby isotopes. A sequence of transitions in the N = 94 167 Ta nucleus exhibiting features similar to those attributed to the wobbling bands in the Lu nuclei has now been found. This band feeds into the πi 13/2 band at a relative energy similar to that seen in the established wobbling bands and its dynamic moment of inertia and alignment properties are nearly identical to the i 13/2 structure over a significant frequency range. Given these characteristics, it is likely that the wobbling mode has been observed for the first time in a nucleus other than Lu, making this collective motion a more general phenomenon. PACS number(s): 21.10. Re, 23.20.Lv, 27.70.+q Our understanding of the wobbling mode in nuclei (and the associated stable triaxial deformation) has evolved quickly over the past decade. Bohr and Mottelson [1] first proposed that the rotation of a stable triaxially deformed nucleus would result in the presence of wobbling excitations. These excitations occur because the rotational angular momentum is not aligned with any of the body-fixed axes; rather it precesses and wobbles around one of these axes in a manner similar to that of an asymmetric top.In 1995, Schnack-Petersen et al.[2] first suggested that rotational bands based on proton i 13/2 excitations in 163,165 Lu are associated with a triaxial strongly deformed (TSD) potential well. The large deformation is mainly due to the occupation of the intruder i 13/2 orbital, and the triaxial deformation (γ = 20 • ) results from an N = 94 shell gap that develops with enhanced quadrupole deformation ( 2 ≈ 0.37). No direct experimental evidence for triaxiality was observed until the wobbling mode was confirmed in 163 Lu by Ødegård et al.[3]. This seminal work established the existence of a band feeding into the πi 13/2 structure where the two sequences have nearly identical moments of inertia and alignments over a large frequency range. The similarities of the moments of * Present address: inertia and alignments are a predicted feature for a wobbling band as the intrinsic structure for both bands should be the same; the only difference between the two is the degree to which the rotational angular momentum vector lies off axis. The collective wobbling behavior can thus be described within a phonon model, where the energy of each band is equal to E =¯h 2 2J I (I + 1) +hω w (n w + 1/2), wherehω w = hω rot (J x − J y )(J x − J z )/(J y J z ) [1]. The n w = 0 phonon number is assigned to the energetically lowest band in the family, as its angular momentum vector lies closest to a body axis, and in the case of the Lu isotopes, this is associated with the πi 13/2 band. Wobbling excitations with n w = 1, 2, 3, etc. then follow, each lying successively higher in energy as the rotational angular momentum vector progressively lies farther from the body axis with increasing n w . Indeed, Jense...

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High-spin states (I 50h) of the odd-odd nucleus 170 Ta have been investigated with the 124 Sn( 51 V,5n) reaction. The resolving power of Gammasphere has allowed for the observation of eleven rotational bands (eight of which are new) and over 430 transitions (∼350 of which are new) in this nucleus. Many interband transitions have been observed such that the relative spins and excitation energies of the 11 bands have been established. This is an unusual circumstance in an odd-odd study. Configurations have been assigned to most of these bands based upon features such as alignment properties, band crossings, B(M1)/B(E2) ratios, and the additivity of Routhians. A systematic study of the frequency at which normal signature ordering occurs in the πh 9/2 νi 13/2 band has been performed and it is found that its trend is opposite to that observed in the πh 11/2 νi 13/2 bands. A possible interpretation of these trends is discussed based on a proton-neutron interaction.

High-spin states in the odd-odd nucleus 166 Ta are investigated through the 5n channel of the 51 V + 120 Sn reaction. Four new bands are observed and linked into the previous level scheme. Configurations for the bands are proposed, based on measured alignments and B(M1)/B(E2) transition strength ratios.