Particle number projection with effective forces

The particle number projection method is formulated for density dependent forces and in particular for the finite range Gogny force. Detailed formula for the projected energy and its gradient are provided. The problems arising from the neglection of any exchange term, which may lead to divergences, are throughly discussed and the possible inaccuracies estimated. Numericala results for the projection after variation method are shown for the nucleus 164Er and for the projection before variation approach for the nuclei 48-50Cr. We also confirm the Coulomb antipairing effect found in mean field theories.Comment: 33 pages, 8 figures. Submit to Nuc. Phys.

Analysis of Delta I =2 staggering in nuclear rotational spectra

A method is proposed and tested for the analysis of Delta I=2 staggering observed in nuclear rotational bands. We examine six super- and hyper-deformed bands, among which that of 149Gd and possibly of 147Gd seem to exhibit real staggering. However, we emphasize that the presence of staggering may not necessarily imply the occurrence of bifurcation. It is also shown that a similar staggering seen in normally deformed bands is a manifestation of band crossings. A more extensive analysis is planned.Comment: 15 pages, Revtex, 15 figures (available upon request at [email protected]

Unpaired Nucleons as Probes of Core Collective Fields

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 ..lambda../sub 0/ 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 ..delta.. as opposed to the IBFM ..lambda..jj' 's, (ii) particle transfer at least in principle, and (iii) easy generalizability. In an application of static mean field theory, the ..cap alpha..-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

Forschungszentrum Rossendorf, Institute of Nuclear and Hadronic Physics. Annual report 1995

This annual report of the Institute of Nuclear and Hadronic Physics (IKH) of the Research Center Rossendorf Inc. (FZR) summarizes the research activities, the results obtained and the progress achieved in 1995. The research activities continued the experimental and theoretical studies aiming at properties of the nucleonic system and its constituents, the hadrons and their variation under extreme conditions like high excitation, spin, density and temperature. (orig.)Available from TIB Hannover: RR 1847(130) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Institute of Nuclear and Hadronic Physics. Annual report 1994

The present third annual report of the Institute of Nuclear and Hadronic Physics of the Research Center Rossendorf (FZR) summarizes the research activities, the results obtained and the progress achieved in 1994. Major research activities were focussed at structure studies of the atomic nucleus and its constituent, the hadrons, as well as the investigation of the behaviour of the nucleonic system in nucleus-nucleus collisions. Theoretical investigations dealt with nuclear and subnuclear degrees of freedom, high-spin phenomena and the dynamics of open quantum systems. The major topic of applied research has been the use of Positron Emission Tomography for monitoring the radiation therapy with light heavy ions. Using the possibilities of a newly built up detector laboratory, important contributions have been provided to different detector systems. A project study for a 250 MeV superconducting electron linac (project 'Elbe' - Electronic Linac with high Brightness and low Emittance) proposes a future accelerator basis at the FZR (WEN)Available from TIB Hannover: RR 1847(95-78) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman