Results 1 - 10 of 1985
Results 1 - 10 of 1985. Search took: 0.032 seconds
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[en] The dependence on deformation of the isovector twist mode ([rY1rvec l]λ=2t+) is investigated. We calculate the strengths and energies in the asymptotic (oblate) limit using 12C as an example of a strongly deformed nucleus. We also consider the λ=1 case. In a ΔN=0 Nilsson model the summed strength is independent of the relative P3/2 and P1/2 occupancy but when we allow for different frequencies ωi in the x, y, and z directions there is an enhancement of this strength due to deformation. This dependence is stronger than that for the ordinary dipole mode but much weaker than that for the scissors mode. At the same time, it is observed that there are considerable changes in the spectrum and that the strength is strongly fragmented amongst these disparate levels. We further show that in this model the associated spin mode [rY1rvec s]λt+ has a weaker dependence on deformation and is less fragmented than the twist mode
[en] In this work, we are interested in understanding the relationship between the Interacting Boson Model ( IBM ) and the Bohr-Mottelson Model ( BMM ). Several authors have shown equivalence between these two models, while others have shown the lack of equivalence. The similarities in some of the two models predictions suggest that they are closely related. An intrinsic state was defined in terms of quadrupole shape variables from which all eigenstates of the IBM were projected by averaging over-these shape variables and the orientations of the interinsic state. With this intrinsic state, on energy surface and Bohr-Hamiltonin were derived for the most general IBM-1 Hamiltonian. For IBM-2 the interinsic state is a product of the neutron and proton intrinsic states. The classical limit of the IBM-2 was investigated. From the general form of the IBM-2 Hamiltonian, a general expression of the potential energy for the neutron and proton distributions aligned along the same axis is obtained. In the present work we have investigated the above methods and applied the expressions for the potential energy to real nuclei ( even isotopes of Os, W and Sm ), in order to compare the results with the BMM
[en] A semi-classical model for wobbling motion is presented as an extension to the Bohr-Mottelson model of wobbling motion. Using the resultant wobbling potential, a quantum mechanical equation is derived for anharmonic wobbling motion. We then attempt to explain the anharmonicity observed in the excited bands of two wobbling phonons in the A∼160 region
[en] The original model for the nuclear wobbling motion was presented by Bohr and Mottelson in 1970s. Despite its beauty in the theoretical framework, the wobbling phenomenon had not been observed until recently. However, as the experimental investigations go on, there appear many problems in the observed wobbling spectrum. One of them is a strong anharmonicity seen in the two wobbling phonon states. The energy spacing between the one and two-phonon states are only half the spacing between the zero and one phonon states. With macroscopic and microscopic approaches, we try to investigate the origin of this strong anharmonicity in the wobbling motion.
[en] Cluster studies have predicted both the existence of a hyperdeformed state in 36Ar,1 and the favorite reaction channels 24Mg+12C, 20Ne+16O for its population.1,2 Recent experimental data seem to justify these predictions,3 and Nilsson-calculations give the same shape.4 According to structure-considerations it could also be built up in alpha-emitting reactions. (author)