Observation of isotonic symmetry for enhanced quadrupole collectivity in neutron-rich 62,64,66Fe isotopes at N=40

TL;DR

This study investigates the enhanced quadrupole collectivity in neutron-rich 62,64,66Fe isotopes at N=40 through Coulomb excitation, revealing isotonic symmetry and supporting shell model predictions.

Contribution

It provides experimental evidence of isotonic symmetry in Fe isotopes at N=40 and introduces a new effective interaction for shell model calculations.

Findings

Enhanced E2 transition strengths in 62,64,66Fe

Reproduction of deformation by shell model with new interaction

Support for valence proton symmetry concept

Abstract

The transition rates for the 2_{1}^{+} states in 62,64,66Fe were studied using the Recoil Distance Doppler-Shift technique applied to projectile Coulomb excitation reactions. The deduced E2 strengths illustrate the enhanced collectivity of the neutron-rich Fe isotopes up to N=40. The results are interpreted by the generalized concept of valence proton symmetry which describes the evolution of nuclear structure around N=40 as governed by the number of valence protons with respect to Z~30. The deformation suggested by the experimental data is reproduced by state-of-the-art shell calculations with a new effective interaction developed for the fpgd valence space.