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Despite the fact that [sup 208]Pb is probably the best example of a shell model nucleus, little is known about its high-spin states and those of its nearest neighbours, primarily because of the experimental difficulties involved in populating neutron-rich nuclei. The high-spin states formed from the valence orbitals are important since they provide the building blocks from which more complex configurations can be calculated. The same orbitals are involved in particle-octupole vibrational coupling which presumably evolves into octupole deformation in heavier nuclei. In this paper we present the results of recent measurements which have used a range of reaction techniques to access states in the N = 128 isotones, [sup 211]Bi, [sup 212]Po and [sup 213]At. The results may contribute to the understanding of the structure of the τ = 65 s isomer in [sup 212]Po. The new states identified include a J[sup π] = 49[sup +]/2 τ = 65 µs isomer in [sup 213]At which decays via an enhanced E3 transition whose strength is influenced by blocking. [ABSTRACT FROM AUTHOR]

A new recoil separator system for studying properties of isomeric states with lifetimes starting from a few hundred nanoseconds is under construction at the Heavy Ion Accelerator Facility of the Australian National University. In this contribution, the design of the system is introduced along with computer simulations on its performance and selected results from the first test measurements. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

High-K states in the region of 177Lu have been studied using multi-nucleon transfer reactions with 136Xe beams and Gammasphere. Results include identification of the predicted 5-quasiparticle Kπ = 39/2 - isomer in 177Lu, a 7-quasiparticle Kπ = 49/2 + isomer in 179Ta with an anomalously fast decay, and numerous other examples in a range of Yb close to stability. The results are discussed in the context of the expectations for multi-quasiparticle states near Z = 72 and the factors which may both govern isomer formation and also give an insight into K-purity, specifically chance degeneracies, and statistical mixing above the yrast line. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

New structures above and below the two-particle isomeric states in [sup 188]Pb have been identified. Their properties are consistent with the presence of three minima in the nuclear potential well, associated with spherical, weakly oblate and substantial prolate deformations. The fragmented decay of the weakly populated K[sup π] = 8[sup -], 1 µs prolate isomer also provides a means of identifying non-yrast low-spin structures which are otherwise inaccessible. Through this mechanism, collective bands which can be associated with the excited 0[sup +] states have been identified and E0 transitions between them inferred. Analysis of the excitation energies, branching ratios and E2/E0 decay-width ratios through a band-mixing model provides a test of shape differences and the separability of the wave functions at low spin. [ABSTRACT FROM AUTHOR]

Fusion-fission reactions were induced by bombarding a thick 27Al target with 178Hf projectiles at a laboratory energy of 1150 MeV using the ATLAS accelerator at Argonne National Laboratory. The subsequent γ-ray decays were measured using the GAMMASPHERE germanium detector array. The beam was pulsed at two different ON/OFF cycles of 82.5/825 ns and 25/75 μs in order to observe the γ rays from the decay of isomeric states. In 121Sb 2721+Δ keV, Iπ=(25/2+) and 2434 keV, Iπ=19/2- states have measured half-lives of T1/2=200(30) μs and 8.2(2) ns respectively. The 2614+Δ keV, Iπ=(27/2+) and 2486 keV, Iπ=19/2+ states in 123Sb have measured half-lives of T1/2=52(3) μs and 7.9(4) ns respectively. The positive parity isomers in these nuclei correspond to a πd5/2 or πg7/2 configuration, in 121Sb and 123Sb respectively, coupled to aligned (h11/2)2 neutrons. The Iπ=19/2- isomeric state in 121Sb is proposed to have a νh11/2 x νd3/2 x πd5/2 configuration. A previously unobserved isomer has been identified in 99Mo at an energy of 3010 keV, decaying with T1/2=18(5) ns. This state is interpreted as an energetically favoured 3 quasi-particle alignment of ν (d5/2 g7/2) x π(g9/2)2 configuration which is observed systematically in the even-Z N=57 isotones. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Measurements of the excitation energies of superdeformed states via the observation of single-step linking transitions have now been made in three even-A Pb nuclei, with a quasicontinuum analysis providing a limit in a fourth, odd-A case. These results allow us to take the first steps towards establishing systematic trends in excitation energies and binding energies in the second minimum in Pb isotopes. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Fragmentation reactions, typically performed at energies ∼E/A > 50 MeV, produce neutron-rich nuclei but leave little angular momentum in the residues. In this work we have examined the product distribution and angular momentum input for a 12C beam at 30 MeV/A on a thick (40 mg/cm2) target of 51V, testing the feasibility of in-beam gamma-ray spectroscopy study of target fragments at this lower energy. This technique allows the study of some neutron-rich nuclei to moderate spins, complementing the beam fragmentation studies. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

We have performed three separate experiments at LBNL’s 88-Inch Cyclotron over a period of several years in which 235U (thick target) was Coulomb-excited. It involved stand-alone experiments with Gammasphere and with the 8PI Spectrometer using 136Xe beams at 720 MeV, and a CHICO-Gammasphere experiment with an 40Ar beam at 180 MeV. In addition to extending the known negative-parity bands to high spin, we have assigned levels in some seven positive-parity bands which are in some cases ( e.g. [631]1/2, [624]7/2 and [622]5/2) strongly populated by E3 excitation. The CHICO data has been analyzed to extract E2 and E3 matrix elements from the observed yields. Additionally, many E1 and M1 matrix elements could be extracted from the γ-ray branching ratios. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

High-spin states in [sup 108]Cd were studied following the reaction [sup 64]Ni([sup 48]Ca,4n) at a beam energy of 207 MeV. Gamma rays were detected using the Gammasphere array. Two rotational bands have been observed at very high angular momentum. Measurements of fractional Doppler shifts yielded lower limits for the quadrupole moments and showed that the observed structures are at least as deformed as the superdeformed structures e.g. in the A ≈ 150 region, and possibly exceed a 2:1 axis ratio. The existence of very extended shapes has been predicted by cranked Strutinsky calculations, and recent projected shell model calculations suggest that the πi[sub 13/2] hyper-intruder orbital is occupied in these newly observed bands. [ABSTRACT FROM AUTHOR]

The intrinsic quadrupole moment Q[sub 0] of superdeformed rotational bands in A∼150 nuclei depends on the associated single-particle configuration. We have derived an empirical formula based on the additivity of effective quadrupole moments of single-particle orbitals that describes existing measurements from [sup 142]Sm to [sup 152]Dy. To further test the formula, the predicted Q[sub 0] moments for two superdeformed bands in [sup 146]Gd of 14.05 eb were confronted with a new measurement yielding 13.9±0.4 eb and 13.9±0.3 eb respectively. This excellent agreement provides empirical evidence of extreme single-particle behavior in highly deformed, collective systems. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have studied the continuous gamma radiation from reactions of [sup 48]Ca beams on targets of [sup 50]Ti, [sup 64]Ni, [sup 96]Zr, and [sup 124]Sn at very high angular momentum. In all but the heaviest target, the nuclear moments of inertia rise rapidly with increasing angular momentum and the data suggest that the gamma ray energies may reach a maximum value. Whether this arises from a gradual transition towards a highly deformed Jacobi-like shape, or from other effects, is unclear. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]