Shell model study of single-particle and collective structure in neutron-rich Cr isotopes

TL;DR

This study uses the spherical shell model to analyze neutron-rich Cr isotopes, successfully reproducing known energy levels and predicting new collective behaviors around neutron number N=40, including a novel band in 64Cr.

Contribution

The paper provides new shell model calculations that predict collective structures and energy level behaviors in neutron-rich Cr isotopes near N=40, including a new band in 64Cr.

Findings

Reproduces known energy levels in Cr isotopes

Predicts enhanced collectivity around N=40

Identifies a new collective band in 64Cr

Abstract

The structure of neutron-rich Cr isotopes is systematically investigated by using the spherical shell model. The calculations reproduce well the known energy levels for the even-even $^{52-62}$Cr and odd-mass $^{53-59}$Cr nuclei, and predict a lowering of excitation energies around neutron number N=40. The calculated $B(E2;2_{1}^{+}\to 0_{1}^{+})$ systematics shows a pronounced collectivity around N=40; a similar characteristic behavior has been suggested for Zn and Ge isotopes. Causes for the sudden drop of the $9/2_{1}^{+}$ energy in $^{59}$Cr and the appearance of very low $0_{2}^{+}$ states around N=40 are discussed. We also predict a new band with strong collectivity built on the $0_{2}^{+}$ state in the N=40 isotope $^{64}$Cr.