β and γ bands in N = 88 , 90, and 92 isotones investigated with a five-dimensional collective Hamiltonian based on covariant density functional theory : vibrations, shape coexistence, and superdeformation
Date
2019-06-05
Journal Title
Journal ISSN
Volume Title
Publisher
American Physical Society
Abstract
A comprehensive systematic study is made for the collective β and γ bands in even-even isotopes with neutron numbers N = 88 to 92 and proton numbers Z = 62 (Sm) to 70 (Yb). Data, including excitation energies,
B(E0) and B(E2) values, and branching ratios from previously published experiments are collated with new
data presented for the first time in this study. The experimental data are compared to calculations using a
five-dimensional collective Hamiltonian (5DCH) based on the covariant density functional theory (CDFT). A
realistic potential in the quadrupole shape parameters V (β,γ ) is determined from potential energy surfaces
(PES) calculated using the CDFT. The parameters of the 5DCH are fixed and contained within the CDFT.
Overall, a satisfactory agreement is found between the data and the calculations. In line with the energy
staggering S(I) of the levels in the 2γ
+ bands, the potential energy surfaces of the CDFT calculations indicate
γ -soft shapes in the N = 88 nuclides, which become γ rigid for N = 90 and N = 92. The nature of the 02
+
bands changes with atomic number. In the isotopes of Sm to Dy, they can be understood as β vibrations, but in
the Er and Yb isotopes the 02
+ bands have wave functions with large components in a triaxial superdeformed
minimum. In the vicinity of 152Sm, the present calculations predict a soft potential in the β direction but do not
find two coexisting minima. This is reminiscent of 152Sm exhibiting an X(5) behavior. The model also predicts
that the 03
+ bands are of two-phonon nature, having an energy twice that of the 02
+ band. This is in contradiction
with the data and implies that other excitation modes must be invoked to explain their origin.
Description
CITATION: Majola, S. N. T. et al. 2019. β and γ bands in N=88, 90, and 92 isotones investigated with a five-dimensional collective Hamiltonian based on covariant density functional theory: Vibrations, shape coexistence, and superdeformation. Physical Review C, 100(4). doi:10.1103/PhysRevC.100.044324.
The original publication is available at https://journals.aps.org/prc/
The original publication is available at https://journals.aps.org/prc/
Keywords
Covariant density functional theory, Density functionals, Nuclear shapes, Potential energy surfaces, Hamiltonian systems
Citation
Majola, S. N. T. et al. 2019. β and γ bands in N=88, 90, and 92 isotones investigated with a five-dimensional collective Hamiltonian based on covariant density functional theory: Vibrations, shape coexistence, and superdeformation. Physical Review C, 100(4). doi:10.1103/PhysRevC.100.044324.