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

Abstract

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 β 2 and β 3 . The system is considered to oscillate between positive and negative β 3 -values, by rounding an infinite potential core in the (β 2 , β 3 )-plane with β 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 150 Nd, 152 Sm, 154 Gd and 156 Dy is presented.

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

“…In this work we apply the original concept for the lowest k By using the wave functions (12) one can calculate B(Eλ) transition probabilities (λ = 1, 2, 3) in the yrast and non-yrast quasi-doublet spectra. The relevant formalism was originally developed in [9,10] and further extended to the non-yrast states of even-even nuclei [13]. In this work we apply the formalism developed in [13].…”

Application of the triaxial quadrupole–octupole rotor to the ground and negative-parity levels of actinide nuclei

“…[25,27,28]. We remark that in the nuclei 230,232,234,238 U the staggering amplitude shows a slow decrease without reaching zero.…”

“…1-9 (left). To get more detailed information about the angular momentum behaviour of the theoretical and experimental alternating-parity sequences we apply the following odd-even staggering formula [25] Stg(I) = 6∆E(I) − 4∆E(I − 1) − 4∆E(I + 1) + ∆E(I + 2) + ∆E(I − 2),…”

“…Based on the earlier interpretation [9] of the positive-and negative-parity excitations, the present approach is essentially different from the concept of pure octupole, or mixed quadrupole-octupole, vibrations and rotations. The latter concept assumes nuclear vibrations with respect to an octupole double-well [14]- [17], [24], or more general two-dimensional quadrupole-octupole potential with axial symmetry [18]- [23], [25]- [28] and rotations, used to explain the so-called alternating-parity spectra.…”

Octupole degree of freedom for nuclei near152Sm in a reflection-asymmetric relativistic mean-field approach

“…The spdf interacting boson model was applied to Sm isotopes with N = 86 − 92 to examine the signatures of octupole correlations [15]. Based on a collective rotation-vibration Hamiltonian in which the axial quadrupole and octupole degrees of freedom are coupled, the energy levels and electromagnetic transition probabilities for N = 90 isotones were well reproduced [16].…”