Oscillator strengths with pseudopotentials

The time-dependent local-density approximation (TDLDA) is shown to remain accurate in describing the atomic response of IB elements under the additional approximation of using pseudopotentials to treat the effects of core electrons. This extends the work of Zangwill and Soven who showed the utility of the all-electron TDLDA in the atomic response problem.Comment: 13 pages including 3 Postscript figure

Multiple excitation modes in Hf 163

Excited states of Hf163 were populated using the Zr94(Ge74,5n) reaction and the decay γ rays were measured with the Gammasphere spectrometer. Two previously known bands were extended to higher spins, and nine new bands were identified. In addition to bands associated with three- and five-quasiparticle configurations, two γ-vibrational bands coupled to the i13/2 excitation were also observed. The lowest level of a newly identified, negative-parity band is proposed to be the ground state of the nucleus. A systematic delay of the high-spin proton crossing frequency with increasing quadrupole deformation from Hf162 to Hf172 was established. Extensive band searches failed to reveal a triaxial, strongly deformed structure in Hf163 similar to the one observed in several nuclei around A∼165

Possible Conservation of the K -Quantum Number in Excited Rotating Nuclei

The \ensuremath{\gamma} cascades feeding into low-K and high-K bands in ${}^{163}$Er are investigated analyzing variances and covariance of the spectrum fluctuations. From a large data set of 1${0}^{9}$ triple coincidences, \ensuremath{\gamma}-\ensuremath{\gamma} coincidence spectra gated by resolved low-lying rotational bands are analyzed. Low-K bands are found to be fed by a much larger effective number of cascades than high-K bands. The covariance between pairs of gated spectra shows that the cascades feeding low-K bands are different from those feeding the high-K bands. The persistence of the K-selection rules for the excited rotational bands within the angular momentum region 30\ensuremath{\Elzxh}\ensuremath{\le}I\ensuremath{\le}40\ensuremath{\Elzxh} is suggested as explanation

Triaxial Superdeformation in 163 Lu

Abstract High-spin states in 163 Lu have been investigated using the Euroball spectrometer array. The previously known superdeformed band has been extended at low and high energies, and its connection to the normal-deformed states has been established. From its decay the mixing amplitude and interaction strength between superdeformed and normal states are derived. In addition, a new band with a similar dynamic moment of inertia has been found. The experimental results are compared to cranking calculations which suggest that the superdeformed bands in this mass region correspond to shapes with a pronounced triaxiality ( γ ≈±20°)

Identification of triaxial strongly deformed bands in 164Hf

Two new rotational bands of distinct character have been identified in 164Hf. They are suggested to correspond to the long-anticipated triaxial strongly deformed (TSD) bands predicted by theoretical studies. The bands have been linked to known states, and the level spins and energies could be determined. The bands are also substantially stronger in intensity and are located at lower spins than the previously observed TSD bands in 168Hf, hereby making 164Hf the best even-even system so far for the study of TSD structures in the A∼160 mass region. Cranking calculations based on the modified-oscillator model suggest that the bands are associated with four-quasiparticle configurations that involve high-j intruder (i13/2)2 proton orbitals

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