[en] Large systematic shell effects on intrinsic E1 moments are found, which should modulate any E1 moment induced by β₃ deformation. The calculated shell effects can explain an emerging trend for E1 data in Ra-Th nuclei, if and only if the gross β₃-induced polarization of finite nuclear matter goes in the same direction as the lightning rod effect. 16 references

[en] The nuclear states amenable to laser studies are reviewed with respect to their structure. Systematic predictions are made, e.g., for magnetic moments of parity-mixed intrinsic orbitals in the Ac isotopes and for the shape of the known high-spin isomers in the Pb region

[en] A photon emitted by an excited state is likely to carry away, at most, 1 or 2 h-bar of angular momentum. Therefore, a profusion of photons is needed to deexcite the rapidly rotating states of nuclei formed by heavy-ion reactions. The study of electromagnetic properties has become the primary source of information on nuclear structure at high spins and, also, at the warm temperatures present in the initial stage of the electromagnetic cascade process. The purpose of this paper is a review of the E1, M1, and E2 properties of such highly excited states. 42 refs., 5 figs

[en] M1 transition rates are strongly structure dependent and may therefore reveal the structure in a quasicontinuum of nuclear excited states. The theoretical interpretations of low-energy stretched dipole bumps are briefly reviewed. Furthermore, it is suggested that there are higher-energy M1 bumps with a signficant unstretched component, and that the related shell effects influence the cooling which feeds the yrast cascade

[en] Nuclei which are soft with respect to the ß shape degree of freedom are expected to have many different structures coexisting in the near-yrast regime. In particular, the lowest rotational quasi-particle in a high-j shell exerts a strong polarizing effect on ß. The ß to which it drives is found to vary smoothly over a 180₀ range as the position of the Fermi level varies. This simple rule is seen to have a direct connection with the energy staggering of alternate spin states in rotational bands. A diagram is presented which provides a general theoretical reference for experimental tests of the relation between ß, spin staggering, configuration, and nucleon number. In a quasicontinuum spectrum, the coexistence of different structures are expected to make several unrelated features appear within any one slice of sum energy and multiplicity. However, it is also seen that the in-band moment of inertia may be similar for many bands of different ß

[en] Quasi-molecular rotational bands characterized by spin states of alternating parity connected by enhanced E1 transitions have recently been observed in several transitional nuclei around ²²⁴Th. The appearance of such bands can easily be understood by assuming the absence of intrinsic parity symmetry in these nuclei. Another likely region on the chart of nuclides to find octupole-unstable nuclei is the region of nuclei around ¹⁴⁶Ba. In fact, in several Xe, Ba and Ce isotopes with n approximately equal to 88, calculations yield octupole-unstable ground states. The main goal of the present study was to calculate equilibrium deformations of doubly-even Xe, Ba, Ce, Nd, Sm and Gd nuclei with neutron numbers between 84 and 94. The method used was the Woods-Saxon-Bogolyubov cranking model method combined with the shell correction approach. The results of these calculations confirm previous expectations of octupole deformed mean fields at low and medium spins in Xe-Sm nuclei with neutron numbers around N = 86. Recent experimental data support theoretical results. 8 refs., 1 fig

[en] Within the framework of the macroscopic-microscopic method, models have been developed that allow the calculation of nuclear masses and fission barriers to an accuracy of approximately 1 MeV, on the average. In one such calculation Moeller and Nix studied nuclei from ¹⁶O to the heaviest known elements. In that calculation the rms deviations between calculated and experimental masses and fission barriers were 0.835 MeV and 1.331 MeV, respectively. We have now used that model to extend the calculations to additional nuclei up to Z = 122. A table where we list calculated ground-state masses, Q/sub α/, Q/sub β/, and Q/sub EC will be published elsewhere. However, since there were some masses missing in the 1980 calculation for Z = 108 and Z = 109 that are now of interest in connection with the recent discoveries of these elements we give the results for these missing elements here. Thus for ²⁶⁴108 and ²⁶⁵108 our new calculation gives the mass excesses 120.90 and 121.95 MeV. For the isotopes ²⁶⁴²⁶⁸109 the results are 128.26, 127.77, 128.52, 128.19, and 129.05 MeV. Experimentally, Armbruster and collaborators have obtained the masses 120.97 MeV and 128.06 MeV for ²⁶⁵108 and ²⁶⁶109, respectively

[en] A particle-core coupling calculation has been made for the positive parity states in the odd-mass Hg isotopes, A = 187 to 197. This work employed the results of recent calculations with mixing between different boson numbers to describe the even-mass Hg cores. Comparison between the calculated results and the experimental scheme can be interpreted as a test of the core description. 9 references

[en] Field theory techniques are applied to the study of interacting boson systems. A dynamical quasiparticle theory derived by the equations of motion method is compared with IBFM as a means of coupling an odd particle to IBM cores. For a single j-shell, the two models are found to be roughly equivalent on a phenomenological level. This equivalence requires that the IBFM parameter Λ₀ is a function of the core, SU(5) vs. SU(3) or O(6), but not an explicit function of the Fermi level. IBFM is found to Coriolis attenuate in strong-coupled bands - partly decoupled cases must be investigated further. The dynamical quasiparticle method has advantages with respect to (i) the physical significiance of the pairing Δ as opposed to the IBFM Λjj' 's, (ii) particle transfer at least in principle, and (iii) easy generalizability. In an application of static mean field theory, the α-cluster interpretation of the SU(4) model for the Ra isotopes is tested. It is found that a larger cluster would be required to account for experimental odd-nucleon decoupling factors. 38 references

[en] A Monte Carlo code is described, which simulates the low-energy (E_γ < or approx. 5 MeV) part of the largely unresolvable gamma-ray spectrum from heavy-ion fusion reactions. It provides a flexible framework for the modeling of nuclear structure at high spin and finite temperature. New features include a formula for the energy dependence of the entry distribution based on thermodynamical considerations, and the implementation of improved line shapes for the giant E1 and rotational E2 strength functions. (orig.)