R. Schultheis

The K = 2 band in 24Mg and the point symmetry of the alpha-cluster model state☆

Abstract The failure of previous constrained alpha-cluster model calculations to reproduce the proper symmetry for the K = 2 band in 24 M is overcome by an unconstrained variation. The resulting cluster centers have D 2h symmetry but differ from the classical alpha-particle model.

Alpha-cluster structure ofS32

The ground state and the first excited states of /sup 32/S have been studied within the alpha-cluster model for two standard soft-core forces. We discuss the approximations resulting from variation without projection, variation after parity projection, angular momentum projection after variation, and possible K mixing. In contrast to earlier calculations in lighter nuclei a free variation of all parameters has been performed without forcing the alpha clusters to be arranged in configurations with prescribed symmetry. In all approximations and for both forces the intrinsic ground state turns out to be triaxial with C/sub 2v/ symmetry. The resulting binding and excitation energies, rms radii, and quadrupole moments are given. In comparable cases a close agreement is found with Hartree-Fock results for the same forces.

Cluster structures in double-humped fission barriers☆

Abstract A method is proposed to calculate the shell energy in fission using cluster representations. First results show that the ground state and the second minimum are due to the formation of doubly-magic clusters, while the barriers are due to their breakup.

The oblate state in 28Si: Alpha cluster structure and point symmetry☆

Abstract The discrepancy between Hartree-Fock and alpha-cluster model results for the oblate minimum in 28 Si has been resolved by releasing the point symmetry restrictions that are customarily imposed on the variational space of alpha cluster model calculations.

Cluster aspects of nuclear fission

Experimental fission data for nuclei in the mass regionA = 210 toA =258 are discussed from a unified point of view using cluster representations of nuclei. It is shown that these data can be described as resulting from a superposition of two different modes, one determined by energetically favoured cluster correlations, the other due to liquid-drop effects only. For all nuclei lighter than Fermium the above distinction coincides with that of symmetric and asymmetric fission. Contrary to that in Fermium-isotopes, both symmetric and asymmetric fission are associated with energetically favoured cluster correlations at the Fermi surface.

An alternative approximate solution to the time-dependent schrödinger equation☆

Abstract A second-order time-differential equation is proposed for the approximate solution of the time-dependent Schrodinger equation with a limited basis. The resulting nonunitary solutions allow for a flux of probability into the excluded space. Simple examples are used in demonstration.

A non-linear approximation to the Schrödinger time evolution in a truncated subspace

Abstract Approximations to the Schrodinger time evolution in a highly truncated subspace are studied as an alternative to the time-dependent Hartree-Fock approximation. We derive a differential equation of second order in time, that involves the subspace matrix elements of the square of the Hamiltonian. The equation is completely defined and soluble within an arbitrarily truncated subspace. The solutions are non-unitary and allow for a flux of probability between the subspace and the excluded space. The accuracy of the approximation is studied in a number of examples.

Effect of angular momentum projection in 28Si on the oblate and prolate alpha-cluster model state☆

Abstract Angular momentum projection is shown to diminish, but not resolve, the discrepancy between experiment and existing alpha-cluster model results for the oblate and prolate state in 28Si.

Beyond TDHF : Schrödinger time-evolution in a truncated subspace

We derive non-determinantalapproximations to the Schrodinger time-evolution in a necessarily truncated subspace, that allow for a flux of probability between the subspace and the excluded space.

A shape isomeric state in 32S from an unconstrained variation

Abstract An unconstrained variational search has been performed for a shape isomeric state in 32S. The effect of parity and angular momentum projection has been studied. The resulting many-body state has a double-peaked density distribution with an 16O-16O structure.