S. B. Drenska

SUq(2) description of rotational spectra and its relation to the variable moment of the inertia model

Abstract Rotational spectra of even-even nuclei can be described by the quantum algebra SUq(2). The two-parameter formula given by the algebra is equivalent to an expansion in terms of powers of j(j + 1), similar to the expansion given by the variable moment of inertia (VMI) model. The moment of inertia parameter in the two models, as well as the small parameter of the expansion, are found to have very similar numerical values.

Description of superdeformed bands by the quantum algebra SUq(2)

Spectra of superdeformed bands in even-even nuclei, as well as rotational bands with normal deformation, are described very accurately within the framework of the quantum algebra SUq(2). Stretching effects are taken into account by allowing the algebra to slightly deviate from the normal SU(2) form. It is proven that this deviation is equivalent to the usual expansion of the energy in terms of powers of j(j + 1), summed up to all orders.

Nuclear collective motion with a coherent coupling interaction between quadrupole and octupole modes

A collective Hamiltonian for the rotation-vibration motion of nuclei is considered in which the axial quadrupole and octupole degrees of freedom are coupled through the centrifugal interaction. The potential of the system depends on the two deformation variables {beta}{sub 2} and {beta}{sub 3}. The system is considered to oscillate between positive and negative {beta}{sub 3} values by rounding an infinite potential core in the ({beta}{sub 2},{beta}{sub 3}) plane with {beta}{sub 2}>0. By assuming a coherent contribution of the quadrupole and octupole oscillation modes in the collective motion, the energy spectrum is derived in an explicit analytic form, providing specific parity shift effects. On this basis several possible ways in the evolution of quadrupole-octupole collectivity are outlined. A particular application of the model to the energy levels and electric transition probabilities in alternating parity spectra of the nuclei {sup 150}Nd, {sup 152}Sm, {sup 154}Gd, and {sup 156}Dy is presented.

Parity shift and beat staggering structure of octupole bands in a collective model for quadrupole-octupole-deformed nuclei

We propose a collective model formalism which describes the strong parity shift observed in low-lying spectra of nuclei with octupole deformations together with the fine rotational band structure developed at higher-angular momenta. The parity effect is obtained by the Schrodinger equation for oscillations of the reflection asymmetric (octupole) shape between two opposite orientations in an angular momentum dependent double-well potential. The rotational structure is obtained by a collective quadrupole-octupole rotation Hamiltonian. The model scheme reproduces the complicated beat staggering patterns observed in the octupole bands of light actinide nuclei. It explains the angular momentum evolution of octupole spectra as the interplay between the octupole shape oscillation (parity shift) mode and the stable quadrupole-octupole rotation mode.

Non-yrast nuclear spectra in a model of coherent quadrupole-octupole motion

A model assuming coherent quadrupole-octupole vibrations and rotations is applied to describe non-yrast energy sequences with alternating parity in several even-even nuclei from different regions, namely

Ground − γ band mixing and odd-even staggering in heavy deformed nuclei

^{152,154}

Coriolis interaction in nuclear single-particle states with mixed parity

Sm,

Broken SU(3) symmetry in deformed even-even nuclei

^{154,156,158}

Delta I=4 and Delta I=8 bifurcations in rotational bands of diatomic molecules.

Gd,

Coriolis interaction in quadrupole–octupole deformed nuclei

^{236}