Speaker
Description
Protons and neutrons in nuclei are arranged in orbitals that follow a shell structure, with energy gaps at specific magic numbers. Experiments using radioactive beams have shown that these magic numbers vanish in some neutron-rich isotopes. This results in unusual arrangements, where configurations with nucleons scattered to higher energy orbitals are the most bound, forming what has been called "Islands of Inversion" [1]. These Islands of Inversion (IOI) have been explained through the shell model with variants of dynamical SU(3) symmetry [2].
The lifetime of the first $2^+$ states in $^{84}$Mo and $^{86}$Mo was measured in an experiment performed at the NSCL, Michigan State University. We discovered a dramatic structural change between the two isotopes from the experimental results. This has been understood as the boundary of an "Isospin-Symmetric Island of Inversion," where both proton and neutron excitations play an equal role and the evolution of collectivity is governed by three-nucleon forces.
References
[1] F. Nowacki, A. Obertelli and A. Poves, Prog. Part. Nucl. Phys. 120, 103866 (2021).
[2] S. M. Lenzi, F. Nowacki, A. Poves and K. Sieja, Phys. Rev. C 82, 054301 (2010).
