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A broad discussion of the ground-state potential-energy surfaces of doubly even deformed and transitional nuclei with Z = 50-82 is presented. The surfaces are calculated microscopically as functions of the quadrupole axial ε and non-axial γ and the axial hexadecapole ε4 deformations. A correlation between the form of the surfaces and the experimental spectroscopic trends is extensively discussed.
The effects of the simultaneous presence of monopole and quadrupole pairing interactions on the fission barriers for heavy and superheavy elements are considered. The first barrier for light Thisotopes is found to be raised by 1 MeV, while heavier actinide nuclei seem to be less affected by the inclusion of quadrupole pairing. For the superheavy elements, the inclusion of quadrupole pairing tends
Ground state moments of inertia and collective gyromagnetic ratios of deformed even nuclei with 50 < Z, N < 82 are calculated in the cranking-model approximation. Rather good agreement with experimental values of the moments of inertia is obtained. The dependence of the moment of inertia on the quadrupole (axial ε and non-axial γ) and on the hexadecapole ε4 deformations is investigated. Special co
Relations between different core-particle coupling models based on the Bohr Hamiltonian are discussed, and in particular the γ-unstable and rigid 30° triaxial cores are compared quantitatively. A new formulation is developed employing a rigid triaxial rotor core and the strong-coupling basis. Within the limitations imposed by this model core, it is equally applicable in the limits of small and ext
A detailed analysis of the positive parity levels in odd gold isotopes is carried out with an extended version of the Hecht and Satchler model (1962). A satisfactory description of 193-199Au positive parity levels and their electromagnetic properties is obtained by coupling several Nilsson particle configurations to an asymmetric rotor.
The strong shell effects observed experimentally and theoretically at high spins and moderate deformations are explained in terms of the interference between two effects. Thus, the effect of the quadrupole deformation to destroy the spherical shell degeneracy can be largely compensated by the orbital separation due to rotational motion. In the resulting coupling scheme, the subshell degeneracy of
A detailed analysis of all the available experimental data concerning the h11/2 system of levels in 189,193,195Au is made with the generalised particle-asymmetric rotor model applied previously to the description of the positive-parity states. The influence of several Nilsson orbitals on such h11/2 systems is also investigated in detail.
A detailed analysis of the positive parity levels in odd iridium isotopes is carried out with an extended version of the Hecht and Satchler model. A satisfactory description of187-193Ir positive parity states and their electromagnetic properties is obtained by coupling several Nilsson particle configurations to an asymmetric rotor.
Two γ-rays of 129.2 and 288.4 keV observed in the β-decay of 55 ms 100Rb are interpreted as representing the two lowest transitions in the 100Sr ground-state rotational band. The energy ratio of the two levels, 3.23, approaches the value for a rigid rotator. The half-life of the 2+ state is 5.15 ± 0.20 ns corresponding to a deformation parameter ε{lunate} of 0.29. The theoretical implications of t
The negative parity states of Ag105-109 are interpreted according to the generalized particle asymmetric-rotor model. In particular, the influence of the different Nilsson proton orbitals (lying near the Fermi level) on the theoretical level spectra and electromagnetic properties is investigated in detail. Furthermore, the analysis of the wave functions of the theoretical levels, and the contribut
Hyperfine structure measurements have been performed in some neutron-deficient gold isotopes, using on-line atomic-beam magnetic resonance (ABMR) techniques at the ISOLDE facility, CERN. The following results have been obtained: 185Au, I = 5/2; 187Au, Δv = 44.35(60) GHz, μ = 0.72(7) n.m. and 188Au, Δv = ± 2992(30) MHz. A discussion of the influence of the hyperfine anomaly is included. With due re
We introduce a method which makes possible to consider individual rotational bands in the high-spin region where pairing is unimportant. For each band, an independent energy minimisation with respect to quadrupole and hexadecapole deformation is performed. Bandcrossings at and above the yrast line are discussed in the light of recent experimental results.
Negative-parity excited states of doubly even nuclei have earlier been attributed to vibrational excitations. This paper shows that an interpretation starting from a reflection asymmetric intrinsic state is more appropriate for certain nuclei in the radium region. Theoretical evidence for stable octupole deformation comes from a deformed shell-model calculation in which we use a single-particle po
The very high spin behaviour of nuclei with ∼ 10 particles outside the 146Gd core are studied. Our method of calculation, which is based on the cranked Nilsson-Strutinsky formalism, makes possible to follow individual configurations as functions of spin. We concentrate on 158Er and 154Dy which nuclei become oblate with rotation around the symmetry axes for I = 40-50. It is found that most such obl
First, nuclear shapes are considered with focus on the γ degree of freedom and the unexplored high-spin regions of negative γ. Next, the role of approximate quantum numbers for very high-spin spectroscopy is examined, using as an example a calculation for 160Er which is related to available quasicontinuum data. The trend from regular to chaotic behavior is discussed in the broader context of theor
The reactions 78Kr( alpha ,n) and 80Kr( alpha ,3n) were used to populate excited states in 81Sr. The de-excitation of these states was studied by in-beam gamma -ray spectroscopy. A number of new high-spin states forming band structures have been observed. Lifetime measurements have also been performed. Theoretical calculations using a particle-rotor approach based on the Nilsson model have been ma
High spin states in 127,129,131La have been investigated using the 100Mo(32S,p4n), E= 160 MeV, 100Mo(34S,p4n), E=155 MeV, and 100Mo(36S,p4n), E=160 MeV reactions, respectively. γ rays were detected using the EUROBALL IV (127,131La) and EUROGAM II (129La) arrays. The results have enabled the negative parity yrast band, built on the πh 11/2 orbital at low spin, and the lowest lying (π, α) = (+, ± 1/
High-spin states in 72Br were studied with the EUROBALL III spectrometer using the 40Ca(40Ca,α3p1n) reaction. The negative-parity band observed in this experiment displays a signature inversion around spin I = 16. The interpretation within the cranked Nilsson-Strutinsky approach shows that this signature pattern is a signal of a substantial triaxial shape change with increasing spin where the nucl
The highest-spin discrete states (I ∼ 60ℏ and Ex ∼ 30MeV) in normal deformed nuclei have been observed in the rare-earth isotope 156Dy using the GAMMASPHERE spectrometer. The quadrupole moments for a variety of configurations, including the 9/2+[404] (g9/2) proton, 1/2+[660] (i13/2) and 1/2-[541] (f7/2, h9/2) neutron orbitals, were measured in a wide range of ∼ 130 nuclei.
The level scheme of 103Pd has been reconstructed using high-fold γ-ray coincidence data obtained with the EUROGAM-2 spectrometer in the 70Zn(36S,3n) reaction at E = 130 MeV. New spins and excitation energies are given for levels in the strongly coupled positive parity bands. Four high-spin bands are discussed in terms of terminating configurations using Nilsson-Strutinsky cranking calculations. On
