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Some recent theoretical achievements on superdeformed nuclei are discussed. A theoretical search for superdeformations in all even-even nuclei between 3466Se32 and 84218Po134 is presented, and new favourable cases are discussed. The unique role of high-N orbits, and also the effect of a static pairing gap on particularly the J(2) moment of inertia is briefly reviewed. Observed single-particle cros
A general survey of the octupole instability of high spin superdeformed (2:1) and hyperdeformed (3:1) nuclei has been performed in the cranked Nilsson-Strutinsky model. The octupole degree of freedom is predicted to play an important role in several already observed superdeformed nuclei around152Dy, and in particular in N=114 isotones in the Hg-Pb-region. High spin reflection asymmetric hyperdefor
A discrete superdeformed band is found in 146Gd. Lifetime measurements yield an average quadrupole moment of 12±2 e b. A band crossing corresponding to an alignment of ≈2h{stroke} is observed at a rotational frequency of 0.65 MeV. A theoretical analysis suggests that the band has a π62v71 configuration with odd spins and odd parity. Arguments are given that the [651 1 2] and [642 5 2] single-parti
The experimental energy level spectrum of 24Mg is compared with potential energy surfaces calculated from the Nilsson-Strutinsky cranking formalism. Positive-parity states are also compared with the Glasgow school sd shell-model calculations. Emphasis is placed on the high spin and energy states. The subshell occupancies are used in the investigation of similarities and differences of the two comp
Some recent advances in high-spin physics are reviewed emphasising the role of symmetries in rotating nuclei. Evidence is presented for breaking of the axial symmetry (triaxiality) as well as of the reflection symmetry (octupole deformation). Spectroscopic consequences of shell structure in rapidly rotating nuclei with 2:1 shapes (superdeformations) are discussed.
It is investigated how particles in high-N shells affect the moment of inertia, {A figure is presented}(2), and the quadrupole moment, Q0, of superdeformed high-spin states. The different behaviour of {A figure is presented}(2) versus the rotational frequency observed for superdeformed states in 152Dy and 149Gd is explained in terms of different occupations of a few high-N orbits. Predictions for
Level densities are calculated at high spins in the cranked Nilsson model by a simple counting procedure. At a fixed deformation and angular momentum excited states are created as many-particle many-hole excitations (up to 10p-10h) on the cranked ground state. The method allows for a detailed study of high-spin level densities at low excitation energies, at most about 6 MeV above the yrast state,
Potential-energy surfaces of heavy nuclei in the Ra-Th region are calculated by the macroscopic-microscopic method using the modified oscillator potential. A rather large region of nuclei with a third minimum along the fission trajectory is found. This minimum appears at a very large quadrupole deformation, ε2 ∼ 0.9, and has a stable octupole deformation with ε3 ∼ 0.2. It is found that in addition
Isoscalar and isovector giant monopole and quadrupole resonances built on high-spin states are studied in a simple model. Using the random-phase approximation the giant resonance states at spin zero are calculated in the deformed harmonic oscillator potential. Quadrupole and monopole operators, as well as the corresponding coupling constants, are obtained in a self-consistent way, and the coupling
The differential cross-section of inelastic electron scattering for the excitation of the K = 1+ mode in156Gd is calculated in DWBA by using microscopically calculated transition-densities. Discussions are given in comparison with experimental data, isovector rotational mode and the quasi-DWBA technique.
Effects of quantum fluctuations, like wobbling and γ-fluctuations, are examined in even- as well as in odd-particle systems by making use of a simple model based on the Bohr hamiltonian. The strong signature dependence observed in ΔI = 1 E2 transitions in odd nuclei is studied in the context of an axially asymmetric deformation. We point out the importance of the quantum fluctuations especially at
The shell effects responsible for superdeformation in the 152Dy region are discussed. Why is only one band observed in 152Dy and why is there another coexistent collective band? How does the superdeformed band decay?
High-spin states in 164Yb have been populated in the 152Sm(16O, 4n) and 150Sm(18O, 4n) reactions. From studies of γγ coincidences, γ-ray angular distributions and conversion electron measurements the level scheme has been constructed. The g-band and the S-band have been established to spin and parity 22+ and 26+', respectively, and the rotational sequences (π, α) = (-, 1)1, (-, 0)1 and (-, 0)2 to
Theoretical calculations show that both the deformation and the pair field change considerably with increasing spin in the ground-state band of transitional rare-earth nuclei with neutron number close to 90. As a consequence of these changes the g factor is expected to show a significant spin dependence in the ground band of certain transitional nuclei. It is suggested that g-factor measurements m
We derive quadrupole operators for vibrational excitations in a triaxially deformed potential of harmonic oscillator type. Also the self-consistent coupling constants are derived.
The yrast spectra are investigated for the non-collective nuclei150, 152Dy using the Nilsson-Strutinsky + blocked BCS model. The separate effects from the pairing force and the quadrupole force (deformation changes) are studied. It is found that the pairing force is important in describing the yrast line up to/- 30, while the quadrupole force is important for I ≥ 20. The calculated increase of the
The side-feeding patterns and the spectra of unresolved γ-lines are calculated for Gd, Dy and Er nuclei with neutron numbers from 82 to 86. Energies and configurations for states from the yrast line and approximately 2 MeV higher in energy are calculated as many-quasiparticle configurations in a deformed oblate potential. The γ-cascade is simulated by a Monte Carlo calculation. With a common avera
A recently observed Kπ = 1+ mode in deformed nuclei is studied microscopically. By calculating the energies, the B(M1)-values and the form-factors of inelastic electron scattering for 156Gd, we conclude that the relatively strong M1-strength observed at 3.075 MeV comes predominantly from the convection current of proton excitations in the Oh 1 2-orbit. We suggest a search for the M1-strength aroun
The yrast states of 160Yb are calculated using the cranked HFB model with particle-number projection and assuming diabatic bands. The energy of each state is minimized with respect to the proton and neutron pairing gap parameters and the deformation parameters ε and γ. The deformation of the ground band is found to increase with increasing spin, i.e. ε gets larger. Simultaneously γ gets slightly n
We derive an expansion of integrals containing a general function multiplied by a Fermi function raised to an arbitrary power v. When v is an integer, direct expressions for the expansion coefficients are given. The expansion is found to converge quite rapidly if the diffuseness of the Fermi distribution is small, and when v ≳ 1.
