Search for candidate chiral nuclei in rubidium isotopes

The chirality in rubidium isotopes is investigated for the first time by using adiabatic and configuration-fixed constrained triaxial relativistic mean-field theory. Several minima with the triaxial deformation and proper particle-hole configuration are obtained in ${}^{78,80,82,86}\mathrm{Rb}$ where the chiral doublet bands are possible to appear. Furthermore, the possible existence of multiple chiral doublet ($\mathrm{M}\chi \mathrm{D}$) bands is demonstrated in ${}^{78,80,82}\mathrm{Rb}$. The experimental explorations for the chirality and $\mathrm{M}\chi \mathrm{D}$ in Rb isotopes are expected to verify the predictions.

Figure 1

The energy surfaces in the adiabatic (open circles) and configuration-fixed (solid lines) constrained triaxial RMF calculations with PK1 for ${}^{76,78,80,82,84,86}\mathrm{Rb}$. The minima in the energy surfaces for the fixed configuration are represented as stars and are labeled as $A,B,C,D,E,F,G$, and $H$, respectively. Their corresponding triaxial deformation parameters $\beta$ and $\gamma$ are also given. The suitable states for the appearance of the chirality are marked by the blue color and asterisks.

Figure 2

The triaxiality parameter $\gamma$ (in degrees) obtained by minimizing the energy is given as a function of the deformation parameter $\beta$ in triaxial RMF calculations based on the PK1 interaction for ${}^{76,78,80,82,84,86}\mathrm{Rb}$. The minima in the energy surfaces for fixed configurations are indicated by stars and are labeled as $A,B,C,D,E,F,G$, and $H$. The shaded area represents the triaxiality parameter $\gamma$, favorable for nuclear chirality. The suitable states for the appearance of the chirality are marked by solid points with the blue color.

Figure 3

The observed excited energies $E\left(I\right)$ of ${}^{78}\mathrm{Rb}$ and ${}^{80}\mathrm{Rb}$ for the positive ($\pi =+$) and negative ($\pi =-$) parity bands, in comparison with two sets of reported chiral doublet bands in ${}^{78}\mathrm{Br}$. The data and the name of the bands for ${}^{78}\mathrm{Rb},{}^{80}\mathrm{Rb}$, and ${}^{78}\mathrm{Br}$ are taken from Refs. [52, 53] and [25], respectively. The excited energies are plotted relative to a rigid-rotor reference. The assigned configurations for the candidate chiral doublet bands in ${}^{78}\mathrm{Br}$ are listed in the panels.