0000000000010298
AUTHOR
P. O. Lipas
Group O(4) in the Nuclear IBA Model
The group O(4) is established as a link in the group chains of the interacting-boson model (IBA) of nuclear structure. It is obtained as a subgroup of O(5) by excluding the m = 0 component of the d boson. Since only the third component of the angular momentum is then conserved, O(4) symmetry is limited to intrinsic states. No O(3) can be sandwiched between this O(4) and the physical O(2). Branching rules are derived for groups U(4), O(4) and O(2). The dynamic-symmetry contributions of O(4) and U(4) to the energy are given. The structure \(O\left( 4 \right) \approx O\left( 3 \right) \times O\left( 3 \right) \supset O\left( 3 \right)\)is established
Nuclear shell model applied to metallic clusters
We apply the nuclear shell model to jellium clusters of up to twenty-one Na atoms. Binding energies, ionization potentials, and photoabsorption cross sections are calculated and compared with mean-field results.
Configuration-interaction calculations of jellium clusters by the nuclear shell model
Configuration-interaction (CI) calculations are performed on Na clusters of up to 20 atoms within the spherical jellium model, with particular attention paid to the magic clusters with N=2, 8, and 20. The interacting valence electrons are assumed to move in the Coulomb field of the jellium core. The numerical work is carried out by the nuclear-structure code oxbash modified to handle LS coupling. The many-particle bases are constructed of harmonic-oscillator single-particle states extending over 11 major shells and, alternatively, of single-particle states generated by the local-spin-density approximation (LSDA). The calculated quantities include ground- and excited state energies, ionizati…
Unrestricted Shapes of Jellium Clusters
A jellium model with a completely relaxable background charge density is used to study metal clusters containing 2 to 22 electrons. The resulting shapes of the clusters exhibit breaking of axial and inversion symmetries, as well as molecular formation. The clusters without inversion symmetry are soft against deformation. The strongly deformed 14-electron cluster is found to be semi-magic. Stable-shape isomers are predicted.
Many-body origin of the plasmon resonance in small metal clusters
The origin of the plasmon excitation in small metal clusters is studied within the jellium model through ab initio electronic-structure calculations based on the nuclear shell model. In the limit of infinite size, the plasmon classically represents pure harmonic motion of the center of mass of the valence electrons. It is shown that this limit is already well approximated by clusters of only eight electrons.
Electron-gas clusters: the ultimate jellium model
The local spin-density approximation is used to calculate ground- and isomeric-state geometries of jellium clusters with 2 to 22 electrons. The positive background charge of the model is completely deformable, both in shape and in density. The model has no input parameters. The resulting shapes of the clusters exhibit breaking of axial and inversion symmetries; in general the shapes are far from ellipsoidal. Those clusters which lack inversion symmetry are extremely soft against odd-multipole deformations. Some clusters can be interpreted as molecules built from magic clusters. The deformation produces a gap at the Fermi level. This results in a regular odd-even staggering of the total ener…