Evidence for octupole vibration in the triaxial superdeformed well of Lu164

High-spin states in Lu164 were populated in the Sb121(Ca48,5n) reaction at 215 MeV and γ-ray coincidences were measured with the Gammasphere spectrometer. Through this experiment the eight known triaxial superdeformed bands in Lu164 could be confirmed. Some of these bands were extended to higher as well as to lower spins. Evidence is reported for the first time for weak ΔI=1,E1 transitions linking TSD3 and TSD1. This observation may imply coupling to octupole vibrational degrees of freedom. The decay mechanism is different from the one observed in the neighboring even-N isotopes, which exhibit wobbling excitations built on the πi13/2 structure with E2(M1),ΔI=1 interband decay. An additional sequence decaying at high spin into TSD1 was observed up to Iπ=(50-). This band has a constant dynamic moment of inertia of ∼70 2MeV-1 and an alignment that is ∼2 larger than that found for TSD1. A revision of the assumed spin-parity-assignment of TSD2 is based on the observed decay-out to normal-deformed structures. The parity and signature quantum numbers of TSD2 are now firmly assigned as (π,α)=(+,0), in disagreement with the former assignment of (π,α)=(-,1), which was based on the assumption that TSD2 is the signature partner of TSD1. TSD1 and TSD2 show an alignment gain at ω∼0.67 and 0.60 MeV, respectively. In TSD1 the involvement of the j15/2 neutron orbital is suggested to be responsible for the high-frequency crossing

Quadrupole moment measurements for strongly deformed bands in Hf171,172

A lifetime experiment, using the Doppler-shift attenuation method, has been performed at Gammasphere to measure the transition quadrupole moments Q t of strongly deformed bands in Hf171 and Hf172. The measured value of Qt ~ 9.5 e b for the band labeled ED in Hf171 strongly supports the recent suggestion that this sequence and several structures with similar properties in neighboring Hf isotopes are associated with a near-prolate shape with a deformation enhanced relative to that of normal deformed structures. The measured values of Qt- 14 e b for the bands labeled SD1 and SD3 in Hf172 confirm that these sequences are associated with a prolate superdeformed shape, a property inferred in earlier work from other measured characteristics of the bands. Similar bands in Hf173-175 are also likely to be associated with superdeformed shapes. The observations are in contrast to predictions of cranking calculations performed with the ultimate cranker code

Evolution of collective and noncollective structures in Xe 123

An experiment involving a heavy-ion-induced fusion-evaporation reaction was carried out where high-spin states of Xe123 were populated in the Se80(Ca48,5n)Xe123 reaction at 207 MeV beam energy. Gamma-ray coincidence events were recorded with the Gammasphere Ge detector array. The previously known level scheme was confirmed and enhanced with the addition of five new band structures and several interband transitions. Cranked Nilsson-Strutinsky (CNS) calculations were performed and compared with the experimental results in order to assign configurations to the bands

High-spin proton alignments and evidence for a second band with enhanced deformation in 171Hf

High-spin properties of the nucleus 171Hf were studied through the 128Te(48Ca,5n) reaction. Previously known bands have been extended to significantly higher spins and four new bands have been extracted from these data. The results are discussed within the framework of the cranked shell model aided by a comparison with level structures in the neighboring nuclei. The band crossings at rotational frequencies ∼500 keV are interpreted as caused by the alignments of h11/2 and h9/2 proton orbitals. Band ED2 exhibits an alignment pattern similar to that of band ED1 which was reported in a recent paper and proposed to be built on a second potential energy minimum involving the deformation-driving proton i13/2 - h9/2 configuration. It is likely that band ED2 is also associated with a deformation enhanced with respect to that of the normal deformed structures. Further experimental investigation is needed to ascertain the nature of this band

Highly deformed band structures due to core excitations in Xe 123

High-spin states in Xe123 were populated in the Se80(Ca48, 5n)Xe123 reaction at a beam energy of 207 MeV. γ-ray coincidence events were recorded with the Gammasphere spectrometer. Four new high-spin bands have been discovered in this nucleus. The bands are compared with those calculated within the framework of cranked Nilsson-Strutinsky and cranked Nilsson-Strutinsky-Bogoliubov models. It is concluded that the configurations of the bands involve two-proton excitations across the Z=50 as well as excitation of neutrons across the N=82 shell gaps resulting in a large deformation, 2≈0.30 and γ≈5°C

Collective and noncollective excitations in 122Te

High-spin states in 122Te were populated in the reaction 82Se(48Ca, α4n)122Te at a beam energy of 200 MeV and γ-ray coincidences were measured with the Gammasphere spectrometer. The previously known level scheme was extended to considerably higher spin. Maximally aligned states and several high-energy transitions feeding into some of these levels were observed. In addition, seven collective high-spin bands were discovered for the first time in this nucleus. The experimental results are compared with cranked Nilsson-Strutinsky model calculations and possible configuration assignments to the new high-spin structures are discussed

High-spin spectroscopy in Xe125

Levels excited up to 39.8 MeV and 119/2 units of angular momentum have been populated in Xe125 by the 82Se(Ca48,5n)Xe125 reaction. High-fold γ-ray coincidence events were measured using the Gammasphere Ge detector array. Nine regular rotational bands extending from levels identified previously up to almost 60ℏ have been identified, and three of these have been connected to low-lying levels having well-established spins and parities. Configurations have been assigned to six of the bands based on alignment properties, band crossings, and comparison with theoretical cranked shell model calculations (CSM). Transition quadrupole moments have been measured for these bands in the spin range 31-55ℏ and were found to be in agreement with the CSM calculations. The corresponding quadrupole deformation ε2 ranges from 0.28 to 0.34 at a γ deformation of 0° and from 0.29 to 0.36 at a γ value of 5°

Revised level structure of Te 120

The level scheme of the nucleus Te120, populated in the reaction Se80(Ca48,α4n), was reinvestigated using γ-ray coincidence data measured with the Gammasphere spectrometer. Previously, five high-spin rotational bands were discovered in this nucleus. The present reinvestigation revealed that the decay of band b1 is more complex than suggested in the earlier work and that it cannot be uniquely determined. Furthermore, a number of new transitions are added to the level scheme. The implications for the spin assignments and excitation energies of the five bands and for comparisons with cranked Nilsson-Strutinsky calculations are discussed

High-spin rotational bands in 123I

High-spin states in 123I were populated in the reaction 80Se(48Ca,p4n)123I at a beam energy of 207 MeV and γ-ray coincidence events were measured using the Gammasphere spectrometer. Three weakly populated, high-spin rotational bands have been discovered with characteristics similar to those of the long collective bands recently observed in other nuclei of this mass region. Configuration assignments are proposed based on calculations within the framework of the cranked Nilsson-Strutinsky approach

Observation of high-spin bands with large moments of inertia in Xe 124

High-spin states in Xe124 have been populated using the Se80(Ca48,4n) reaction at a beam energy of 207 MeV and high-multiplicity, γ-ray coincidence events were measured using the Gammasphere spectrometer. Six high-spin bands with large moments of inertia, similar to those observed in neighboring nuclei, have been observed. The experimental results are compared with calculations within the framework of the cranked Nilsson-Strutinsky model. It is suggested that the configurations of the bands involve excitations of protons across the Z=50 shell gap coupled to neutrons within the N=50-82 shell or excited across the N=82 shell closure