Islands of high-spin yrast isomers

Review of metastable states in heavy nuclei

“…[155].) Andersson et al [139] showed that inclusion of the deformation in their DMO model dramatically improved the comparison between theory and experiment, compared to a pure "spherical" case. However, this improvement in energy should not be taken to imply that deformation is a necessary component, and it can be misleading if the configuration assignments disagree with other experimental properties.…”

“…A similar scenario applies to the decay of numerous high-spin isomers with related configurations that have been discovered in this region, including the astatine isotopes [151,169,201,202], other radon isotopes [203,204] and the francium isotopes [205,206,207]. 212 Rn The DIPM calculations of Andersson et al [139] used the Strutinsky method and the modified harmonic oscillator potential to predict states (specifically yrast traps) up to 30 in 212 Rn. In order to match the spherical singleparticle levels for the i 13/2 proton and j 15/2 neutron, they adjusted the parameters given by Nilsson et al [208] to displace those levels through a reduction of the Nilsson parameter µ, hence the label of displaced modified oscillator, or DMO.…”

“…This is a natural expectation given that increasing numbers of particles congregate near the nuclear equator as high angular momentum states are formed by the mutual alignment of the spins of individual nucleons. This idea is captured in various versions of the deformed independent particle model (DIPM) [137,138,139,140,141] as will be discussed with reference to both the radon region and the gadolinium region (Sects. 4.1.9 and 4.2, respectively).…”

Nuclear structure at high angular momentum

“…A second backbend has been observed in the yrast sequence of a few (33 ± 2)h. The structure of the isomers can be ascribed to the alignment of a small number (2-8) of shell-model particles in a spherical or slightly oblate potential (Dossing, et al, 1977, Andersson, et al, 1978, Cerkaski, et al, 1977, Faessler, et al, 1976a. There was no indication of isomeric states at very high spins within the limitations set by the experimental arrangement, 20 ns < T,,~ < 500ns, indicating no strongly oblate shapes there.…”

Effects of thermal shape fluctuations and pairing fluctuations on the giant dipole resonance in warm nuclei

“…The three oscillator frequencies ω k , where k = 1, 2, 3, are given by the Hill-Wheeler approximation [47] as MeV and the Nilsson parameters κ and µ values are chosen for appropriate mass regions from Refs. [46,48,49]. The Hamiltonian (3) is diagonalized in cylindrical representation up to first twelve principal harmonic oscillator shells using the matrix elements given in [50] to obtain the singleparticle energies (e i ), separately for protons and neutrons.…”