[en] The signature inversion in the πh_11/2·νh_11/2 rotational bands of the odd-odd Cs and La isotopes and the πh_11/2·νi_13/2 bands of the odd-odd Tb, Ho and Tm nuclei is investigated using pairing and deformation self-consistent mean-field calculations. The model can rather satisfactorily account for the anomalous signature splitting provided that spin assignments in some of the bands are revised. Our calculations show that signature inversion can appear already at axially symmetric shapes. It is found that this is due to the contribution of the (λμ)=(22) component of the quadrupole-pairing interaction to the mean-field potential

[en] The high-spin structure of the stable nucleus ¹⁸⁶Os has been studied, using a radioactive ¹⁴C beam. New rotational bands built on multi-quasiparticle states with K^π = 5^-, 7^-, 9^-, 10⁺ and 15⁺ are observed and the bandhead energies are compared to predictions of blocked BCS calculations. The first crossing of the ground-state band at I = 14ℎ, involving a high-K t-band structure, is observed and explained using a two-band mixing model. The structure at higher angular momentum is dominated by intrinsic states, that exhibit a dramatic loss of isomerism. Potential-energy-surface calculations, with Lipkin-Nogami pairing, show these configurations to be triaxial, accounting for the breakdown in K conservation. The relation between the K projection and the total angular momentum is investigated for these non-axial states

[en] The high-spin structure of the nucleus ¹⁸³Re has been studied following the ¹⁷⁶Yb(¹¹B,4n) reaction. High-K, multi-quasiparticle excitations compete with collective rotation in the formation of the yrast and near-yrast structures. Broken-pair (i_13/2)² excitations (t-bands) play a dominant role, generating considerable angular momentum both along and perpendicular to the prolate symmetry axis. The stability of axially symmetric, prolate shapes is explored through comparisons with potential-energy-surface calculations. The possible onset of oblate rotation at high angular momentum is discussed

No abstract available

[en] Energy-surface calculations for nuclides in the neutron-rich ¹⁹⁰₇₄W₁₁₆ region show consistently that the collective rotation of a deformed oblate shape is an energetically favoured mode, especially for angular momenta I>12-bar . By comparing the calculations with existing experimental data, it is concluded that the reported t_1/2∼1 ms isomer in ¹⁹⁰W may be an oblate shape isomer. mer

[en] The proton-rich isotopes ¹⁴⁰Tb and ¹⁴¹Dy were produced via the fusion evaporation reaction ⁴⁰Ca+¹⁰⁶Cd. Their β-delayed proton decays were studied by p-γ coincidence in combination with a He-jet tape transport system, and half-lives, proton energy spectra, γ-transitions following the proton emission, as well as β-delayed proton branching ratios to the low-lying states in the grand-daughter nuclei were determined. Comparing the experimental data with statistical model calculations, the ground-state spins of ¹⁴⁰Tb and ¹⁴¹Dy were found to be consistent with 7 and 9/2, respectively. The configuration-constrained nuclear potential energy surfaces (NPES) of ¹⁴⁰Tb and ¹⁴¹Dy were calculated using the Woods-Saxon-Strutinsky method, which suggest the ground-state spins and parities of ¹⁴⁰Tb and ¹⁴¹Dy to be 7⁺ and 9/2^-, respectively. In addition, the configuration-constrained NPES of ¹⁴³Dy were calculated, which predict a 1/2⁺ ground state and a 11/2^- isomer with excitation energy of 198 keV. These findings are consistent with our previous experimental data on ¹⁴³Dy reported in Eur. Phys. J. A 16, 347 (2003). (orig.)

[en] The properties of proton resonances in the p and sd shells are studied with a single-particle potential generated by self-consistent-mean field calculations. Besides, we also propose to calculate the proton-nucleus interaction by a double-folding procedure with the density of the daughter nucleus represented by the result of the same mean-field model. Without raising any adjustable parameter, these calculations provide reasonable estimates for the widths of observed proton resonances in light nuclei. The mean-field-based calculation is particularly useful for the predications of the properties of resonances in light exotic nuclei and the direct proton capture reactions of astrophysics. (author)

[en] The nuclear structure of the stable nucleus ¹⁸⁴₇₆Os has been studied including five newly identified rotational bands built on 2-quasiparticle K^π=0⁺, 6^-, 8^- couplings. The excitation energies of the proposed multi-quasiparticle excitations are in good agreement with predictions of blocked BCS calculations. The interaction responsible for the first band crossing, caused by a high-K tilted 2-neutron configuration, is calculated and a new interpretation presented for the yrast states after the interaction. A second crossing with an aligned s-β band is also reported. The yrast behaviour at high spins is dominated by a wealth of short-lived (nanoseconds and shorter) high-K levels. The low reduced hindrances for intrinsic state decays are discussed, and attributed to the triaxial shapes and fluctuations predicted by configuration-constrained potential-energy-surface calculations. Comparisons with neighbouring nuclei are made

[en] Cranked Hartree-Fock Bogoliubov calculations have been performed for the doubly-mid-shell, N=104, Z=66 nucleus ¹⁷⁰Dy. Assuming the usual spherical magic shell gaps at nucleon numbers 50, 82 and 126, this represents the nucleus with the maximum number of valence nucleons below ²⁰⁸Pb and as such, might naively be thought to exhibit one of the largest low-lying collectivities in the entire Segre chart. The results of our calculations suggest a robust quadrupole deformation, with very little deviation from axial symmetry up to high spins. These results are compared with other recent calculations performed by us on this nucleus which suggest a favoured, K=6⁺ (neutron) 2-quasiparticle state which should have an extended decay lifetime (of the order of hours) into the ground state band. (author)

[en] A spin-conserved potential-energy-surface (PES) calculation, which takes angular momentum restoration and multi-quasiparticle excitations into account is developed by using the concepts of the macroscopic-microscopic shell correction and the projected shell model (PSM). With this method, it may become possible to modify the excitation spectra which are influenced by shape-softness of nuclei. As our first example, this method is performed to study the multi-quasiparticle and collective excitations of "1"7"8Hf, which are in good agreement with the existing experimental data. In addition, the conflict of the dominant structure of 6"+ band between experimental results and previous PSM calculations is clarified. (authors)