Abrupt structural transition in exotic molybdenum isotopes unveils an isospin-symmetric island of inversion
- J. Ha
- F. Recchia
- S. M. Lenzi
- H. Iwasaki
- D. D. Dao
- F. Nowacki
- A. Revel
- P. Aguilera
- G. de Angelis
- J. Ash
- D. Bazin
- M. A. Bentley
- S. Biswas
- S. Carollo
- M. L. Cortes
- R. Elder
- R. Escudeiro
- P. Farris
- A. Gade
- T. Ginter
- M. Grinder
- J. Li
- D. R. Napoli
- S. Noji
- J. Pereira
- S. Pigliapoco
- A. Pompermaier
- A. Poves
- K. Rezynkina
- A. Sanchez
- R. Wadsworth
- D. Weisshaar
2025-11-27
Like electrons in atoms, protons and neutrons in nuclei occupy orbitals in a shell structure with energy gaps at magic numbers. Radioactive-beam experiments revealed the disappearance of magic numbers in some neutron-rich isotopes. In these nuclei, configurations involving particles excited across the shell gap gain correlation energy, becoming the ground state. Neutron-rich regions of the nuclear chart that exhibit this property are known as “Islands of Inversion”. Here we present the lifetime measurement of the first 2 + states in 84 Mo ( N = Z ) and 86 Mo ( N = Z + 2) revealing an unexpected sharp structural change between them defining the edge of the region of deformation around 80 Zr. Similarly to the neutron-rich N = 40 Island of Inversion near 64 Cr where cross-shell excitations dominate, we identify this region as an Island of Inversion with symmetrical proton and neutron excitations that we term “Isospin-Symmetric Island of Inversion”. Three-nucleon forces are suggested to drive Mo isotope structural changes.