Investigation of octupole collectivity near the $A=72$ shape-transitional point

Abstract

Enhanced octupole collectivity is expected in the neutron-deficient Ge, Se and Kr isotopes with neutron number $N\approx 40$ and has indeed been observed for ${}^{70,72}$Ge. Shape coexistence and configuration mixing are, however, a notorious challenge for theoretical models trying to reliably predict octupole collectivity in this mass region, which is known to feature rapid shape changes with changing nucleon number and spin of the system. To further investigate the microscopic configurations causing the prolate-oblate-triaxial shape transition at $A\approx 72$ and their influence on octupole collectivity, the rare isotopes ${}^{72}$Se and ${}^{74,76}$Kr were studied via inelastic proton scattering in inverse kinematics. While significantly enhanced octupole strength of $\sim 32$ Weisskopf units (W.u.) was observed for ${}^{72}$Se, only strengths of $\sim 15$ W.u. were observed for ${}^{74,76}$Kr. In combination with existing data, the new data clearly question a simple origin of enhanced octupole strengths around $N=40$. The present work establishes two regions of distinct octupole strengths with a sudden strength increase around the $A=72$ shape transitional point.

References in corpus (8)

• Structure of Krypton isotopes calculated with symmetry conserving configuration mixing methods
• Shape mixing dynamics in the low-lying states of proton-rich Kr isotopes
• A further look at prolate dominance in nuclear deformation
• Triaxiality and shape coexistence in Germanium isotopes
• Shape changes in the mirror nuclei ${}^{70}$Kr and ${}^{70}$Se
• Shape coexistence revealed in the $N=Z$ isotope ${}^{72}$Kr through inelastic scattering
• UCGretina GEANT4 Simulation of the GRETINA Gamma-Ray Energy Tracking Array
• Effect of configuration mixing on quadrupole and octupole collective states of transitional nuclei

Cited by in corpus (3)

• Hexadecapole strength in the rare isotopes ${}^{74,76}$Kr
• Origin of octupole deformation softness in atomic nuclei
• Proton removal from ${}^{73,75}$Br to ${}^{72,74}$Se at intermediate energies